TABLE OF CONTENTS
CHAPTER NO TITLE PAGE NO
ABSTRACT
INTRODUCTION
1 LITRATURE SURVEY
3 EXPERIMENTAL SETUP AND PROCEDURE
4 RESULT AND DISCUSSION
5 CONCLUSION
6 REFERENCE
7 FUTURE OF WORK (EGR,supercharging)
8 APPENDIX
I. PHOTOGRAPHY
II. TEST RESULTS
ABSTRACT
Petrol and diesel are the most widely used fuel for transportation
purpose. Since it is a non-renewable source of energy and due to the
current level of usage, will result in its depletion in the coming years.
So there is a need in changing the current standards in fuel
consumption. Thus the idea of a natural fuel came into existence. But
the efficiency of the bio-fuels are way lower than gasoline, we try to
mix the bio-fuel with diesel to reduce its quantity in usage without
much loss in their efficiency.
Here we are taking rubber seed oil for
preparing the bio-fuel since it is non-edible oil and is available
abundantly in the southern end regions of India. Rubber seed oil
cannot be used directly as a fuel due to its high density and higher
acid content. So we are reducing them both. Then only it could be
mixed with diesel for getting optimum value for its efficiency. Then
the obtained biodiesel will be blended with diesel and its
performance will be obtained. And the compression ratio of this best
performance value is varied in a VCR DI Diesel Engine and optimum
value is to be found out.
For more than 70 years, in many countries bio-fuels have played an important role as fuel in automobiles as they are renewable, eco-friendly and non-toxic. They can effectively substitute diesel fuel and help to reduce the import of petroleum crude. Besides, they can create huge rural employment. The discarded rubber seed from the hefty rubber plantation of southern India is considered as the potential source for extracting biodiesel. Since extracted raw rubber seed oil cannot be used for edible purposes, utilizing this waste oil as an alternate fuel will lend a hand in conserving petroleum reserves.
Rubber seed oil extracted and used for this analysis is having an acid value of 35, which is equivalent to 17.5% Free Fatty acid. The major influencing process parameter and their ranges are identified to optimize the acid and alkaline catalyzed esterification process. Design of experiments is employed in this work, since it takes into account the interactive effects between the input parameters. It is a powerful statistical approach which is used for optimizing the process parameters through two stage esterification process, relating acid and alkaline as catalyst.Reducing the acid value is the primary objective for process optimization in acid esterification process, whereas, maximizing the monoester yield is the objective for the alkaline-esterification process. Different saturated and unsaturated monoesters present in the biodiesel are quantified using gas chromatography in order to determine the yield percentage, which ensures the quality of the biodiesel. The viscosity of the oil is reduced from 37.06 to 3.12 millimeter square per second, which is similar to that of diesel. The fuel is tested for properties such as viscosity, calorific value and carbon residue using standard test procedures and found to be analogous with diesel, which makes it possible to use this alternate fuel in the existing engine without any modification. A single cylinder, four stroke, constant speed, variable compression ratio, direct injection diesel engine developing 5 kilo watt with provision for computerized data acquisition is used to evaluate the performance, emission and combustion characteristics. The test results are analyzed for blends of bio-diesel in comparison with standard diesel at different compression ratios (16:1, 18:1, 20:1 & 22:1). From the results of performance, emission and combustion characteristics of the engine, it is noticed that brake thermal efficiency for bio-diesel is slightly better than that of diesel at all compression ratios. Moreover, the optimum compression ratio for bio-diesel is found to be 20 and that for standard diesel is 18. Engine modification is a method to improve the performance of the engine and reducing pollution levels. The engine runs at higher injection pressures of 240 bars and 260 bars; in addition to that the piston is coated with Copper, Magnesium oxide and Nickel for a thickness of 350 microns using plasma spray technique. The effect of coating lowers heat rejection from the combustion chamber through thermally insulated components increases available energy which further increases the efficiency and reduces emission.
CHAPTER 1
INTRODUCTION
Fast depletion o f fossil fuels accompanied by serious environmental issues. The longevity of the world’s oil reserves is up for debate. On the other hand, global warming threatens the world nations forcing for the emergence of sustainable energy sources. Countries are striving for energy security and independence, since the base Strength of a nation is its energy resources.
Energy resources available in two forms – renewable and non-renewable, are the prime indicators of a country’s growth and development. Till date we are mainly relying on non-renewable fossil fuels – coal, oil and natural gas contributing to more than 80% of our consumption. The burning of fossil fuels produces around 21.3 billion tones (21.3 gigatonnes) of carbon dioxide per year, and it is estimated that natural processes can only absorb about half of that amount, leaving a net increase of 10.65 billion tons of atmospheric carbon dioxide per year
CRUDE OIL
Oil has become the world's most important source of energy since the mid-1950s, due to its high energy density, easy transportability and relative abundance and is being consumed increasingly. Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents,
Plastics which contribute around 16%. Petroleum is found in porous rock formations in the upper strata of some areas of the earth's crust. There is also petroleum in oil sands (tar sands). Known oil reserves are typically estimated at around 190 km3 [1.2 Countries at the end of 2011, the highest proved oil reserves including non-conventional oil deposits are in Venezuela (24.8% of global reserves), Saudi Arabia (22.1% of global reserves), Iran (12.9%) and Iraq (11.8%) [9]. Consumption of oil is currently around 84.6 million barrels (13.4×106 m3) per day or 4.9 km3 per year, which in turn yields a remaining oil supply of only about 120 years, if current demand remains static [10].
ALTERNATIVE FUEL SOURCE
The situation has led to the search for an alternative fuel, which should be not only sustainable but also environment-friendly. Renewable fuels so far being emerged are solar, wind, hydropower, tidal and wave energy, geo-thermal energy, hydrogen fuel cell, alcohol, biogas, biomass, synthetic fuels, etc. As on 2010, only about 16% of global energy consumption comes from renewable sources [17], 10% from traditional biomass, w hydroelectricity. Other emerging renewables (small hydro, modern biomass, wind, solar, geothermal and biofuels) accounted for another 3% and are growing very rapidly. In recent years there has been a trend towards an increased commercialization of various renewable energy sources.
Industrialization and globalization have increased the automobile population in the recent years. Huge usage of fossil fuels reduced the carbon sources within a short span of time [1]. During 1970’s the Organization of Petroleum Export Countries (OPEC) implemented a series of price hike due to heavy demand for fuel which increases the cost of fuel, due to this reason the vehicles have to meet the increasingly stringent emission norms. By using various fossil fuels the carbon dioxide level has been increased from 250PPM to 380PPM. These emission levels are increasing drastically by burning the fuel which leads to greenhouse effect, acid rains, smog and global warming thought the world. These factors have made the researches to focus their attention on alternative and eco-friendly fuels that would help to reduce the import of crude oil, which will reduce the emission significantly.
The use of vegetable oil in diesel engine had been done by the father of diesel engine named Rudolf Diesel. He run his first diesel engine using peanut oil in 1900 . In early periods low cost of fossil fuel did not lend the hand to a large extent on utilizing vegetable oil or biodiesel. The whole consumption of the fossil fuel cannot be replaced by the vegetable oil. Rapid growth of pollution from vehicles makes the scientists to concentrate on pollution free fuels. Statistical data reveals that the available fossil fuels can withstand for about sixty years.
The alternative fuels, have better characteristics like energy conservation, efficiency and environmental preservation. The bio fuels are an alternative solution for the worldwide petroleum crisis. Researchers in the world are working on several alternative sources in order to make a pollution free environment because diesel engines are the major sources for pollution.
Energy sources are biomass, biogas, primary alcohols, vegetable oils and biodiesel are eco-friendly and they can be used directly in diesel engines by bringing the properties closer to diesel.
BIO-MASS
It is an organic matter produced by plants and aquatic derivatives. It can be considered as a renewable energy source because plant life renews and adds to itself every year. The word clearly signifies, biomass means organic matter. Biomass is classified in to two categories, in which biomass
in its traditional solid mass and biomass in its nontraditional form. The first type of biomass is to generate energy by direct conversion method. The second category is to convert the biomass into ethanol and methanol which can be used as a liquid fuel. The thermal plants run by biomass have advantages over coal and diesel fuel plants because the rate of emission gradually reduces when using bio fuels. When biomass is used directly in energy application without chemical processing it is combusted. Biomass can be converted into biofuels such as bioethanol, biodiesel and thermo chemical conversion products such as syn-oil, bio-syngas and biochemical’s.
Bio-mass has been a source of fuel used traditionally for many centuries in under-developed countries. In the developed countries, the application of bio-mass is increasing significantly and it plays an important source for combined heat and power generation. Our country accounts for one third of the total bio-mass consumption in the world, in which for house hold purpose nearly 80% of the rural people and 20% of the urban are using biomass. According to the present scenario about 3400MW of power could be generated from sugar mills in India. Around 290 MW capacity power plants have already been commissioned and some more are under construction.
BIO-OIL
Bio-oil is formed by the process called pyrolysis. The input feed stock undergoes heating in the absence of oxygen to produce bio fuels. The raw materials are solid mass such as wood, house hold waste or agro waste. The end products such as gases and bio oil can be utilized as a fuel for generating energy when it undergoes combustion.
BIO-FUELS
Environmental pollution takes place mainly by transportation and agricultural sector which consumes more amounts of fossil fuels and it can be reduced by replacing mineral-based fuels by bio-origin. Bio-fuel is any fuel that is derived from bio-mass such as waste fruits, vegetables, living organism or their metabolic byproducts. In the next few years, due to its less pollution content the biofuel playas a vital role in the automobile area. The merits of bio-fuels are the following
• It can be generated easily from bio sources.
• Eco friendly.
• Free from pollution.
• Biodegradable.
Bio-fuels namely ethanol, methanol, bio-gas and vegetable oils are being used as an alternative to fossil fuels partially or fully in diesel engines.
BIO GAS
The generation of Biogas is by an aerobic digestion or fermentation process. The input material is plant waste, animal waste, agro waste, kitchen waste etc are utilized as an input for the generation of biogas. In the gasifier these feed stock is undergone fermentation process in the absence of oxygen which liberates biogas, in which its major composition is methane.
Biogas can be produced by feeding energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste. The process takes place in an air-tight tank which helps in the production of methane. The generation of biogas may varies depending upon the raw material which is used as an input. Biogas also contains water vapor. Highly compressed biogas is has been used in countries such as Sweden, Switzerland, and Germany. In early 2006 bio gas powered trains has been in service in Sweden.
VEGETABLE OIL
The father of diesel engine Dr. Rudolf planned to run the engine with different fuels like vegetable oils. But his first trial becomes a failure in the exhibition held at Paris when running with 100% vegetable oil. By using the vegetable oil as fuel the development of agriculture gives the employment for the farmers. Due to high viscosity of vegetable oil the combustion efficiency has been reduced when compared with the diesel. The fluctuating prices of crude oil focused the vegetable oils and animal fats to generate biodiesel for future generation.
The plantation of soybean in United States of America, Sunflower oil in India and palm oil in Malaysia are being considered as a substitute for Diesel fuel. The bio fuel must satisfy the operating conditions by giving better efficiency and it may fulfill the environmental protection. Bio diesel can give better efficiency than diesel fuel by making minor modification in engine like dual fuelling, fuel injection modification and in fuel supply system like blending, micro emulsion, cracking and viscosity reduction.
Jatropha Curcas
Jatropha is derived from the greek word which has been used for medical purpose. The plant can grow on hard soils where there is low rainfall, and it makes good income for the village people who involved in agriculture sector [4, 5, 6]. Rapid growth can be seen in terrestrial soils and it can prevent from erosion of soil. When jatropha is cultivated under optimum conditions, the grown trees produced about five kilogram of seed per year. Jatropha curcas gives yield for very long years on an average of 30 -60 years [7, 8].
Jatropha curcas belongs to spurge family which has been originated from Central America. It is a poisiounes species of flowering plant and cultivated in tropical and subtropical regions around the world reaching a height of 5.5m and has a resistance to with stand the heat, so it can be grown in deserts. The jatropha seeds contain 25 - 44% oil which can undergo esterification process to produce biodiesel, and can be substituted as a fuel in diesel engines [86]. Oleic, linoleic, palmitic and the stearic fatty acids are the major fatty acids present in jatropha seeds [9, 10]. The highest percentage of composition of oleic acid is 42.8% and linoleic acid is 32.8%.
Pongamia Pinnata
Pongamia pinnata is normally mentioned as Karanji in Hindi [11]. It grows about 12-30m height which spreads equally wide. In summer the leaves are soft and shiny. It starts flowering after 2 - 5 years. The flowers are purple in colour and finally it gives seeds which appear in brown colour. It’s a traditional Ayurvedic medicine which can be
used for treating various diseases. It is a medicinal plant native to Western Ghats and chiefly found in tidal forests of India [12, 13]. The tree has large number of uses, and it can be utilized for preparing medicines, but its major contribution is in production of biodiesel. The seeds have an average of about 30– 38% oil with high percentage of poly unsaturated fatty acids [14]. If you analyze the medical history the karanji plays a vital role in Ayurvedha and Siddha systems of Indian medicine [15]. The entire plants are used for treating various dieseas such as tumours, piles, skin diseases, itches, abscess, painful rheumatic joints wounds, ulcers, diarrhea etc [16].
Neem oil
It is an ever green tree which gives the vegetable oil from the seeds of Neem. The seeds are pressed and the oil is extracted by screw pressing. The oil is generally red in colour and it gives a bad odour. The oil has high triglycerides and it contains steroids. Neem oil is not used for cooking purposes but it plays a vital role in medical applications [17, 18]. The percentage oil received from the neem seeds vary from 25% to 45% and the oil is extracted by pressing the kernels under the standard temperature.
Rapeseed oil
It belongs to the family Brassicaceae, which is a flowering plant gives beautiful yellow flowers. The latin word named Brassicacea family of plants includes similar crops, such as mustard and cabbage. The seeds contain high oil content and it is rich in protein. Most of the world's rapeseed is grown in China, Canada and India [19]. Mainly rapeseed is grown for the production of biodiesel in addition to that it can be used for animal feed. In our country plantation is done in 15% of dry lands. Agriculture department has announced in the year 2000, in which rapseed takes its third place for producing huge amount of vegetable oil in the world. The trucks and cars in European countries are expected to run with biodiesel in 2015.
Rubber seed oil.
Our country plays a vital role in the production of rubber, in which Kerala is the leading state for rubber plantation. The rubber tree comes under the family of Euphrobiaceae [29]. The tree grows to a height of 25 to 35 meters which grows straight and has a light brownish straight bark. The tree gives latex on daily basis which is extracted from its trunk. The latex is of high cost. It is white in color with a high viscous liquid. The collected latex is solidified by using acid as a catalyst. The thickness of the latex is reduced by sending it in two rollers and finally it is dried. The latex plays a vital role in automobile industry for the manufacture of tiers and some rubber parts. The plant sheds their leaf in every year during the month of January and it starts growing from March which yields flowers. Flowers are small but appear in large clusters. However, the rubber tree also produces large volumes of seed, which is underutilized.
CHAPTER 2
LITRATURE REVIW
ENGINE PERFORMANCE AND EMISSION
Ramadhas et al. had conducted experiments on the utilization of rubber seed oil Methyl esters on A four stroke, direct injection, naturally aspirated single cylinder diesel engine.
It is reported that Rubber seed oil extracted from the rubber seeds is having high free fatty acid content so it must undergo esterification process to bring the properties closer to diesel. The experiments are carried out by using different blends of methyl esters of rubber seed oil and using diesel as a fuel the combustion and emission characteristics are carried out in a single cylinder direct ignition diesel engine.
Edwin Geo et al. Have carried out investigations to study the performance, combustion and exhaust emission characteristics of Rubber seed oil Methyl ester in a single cylinder direct injection, four-stroke diesel engine.
The properties of the rubber seed oil methyl ester were observed and it is similar to that of diesel and they were miscible with diesel without any phase separation. He utilized three different types of fuel for his experimental investigation such as Diesel, Rubber seed oil methyl ester and pure Rubber seed oil.
Jindal et al. studied the performance and emission characteristics on an variable compression ratio diesel engine by varying the compression ratio and injection pressure. He selected the vegetable oil named jatropha for his experimental work, which is non edible oil.
Result shows the relationship between the variables such as compression ratio and injection pressure. Initially the methyl ester utilized as a fuel in diesel engine is prepared in the chemistry laboratory using esterification process. He selected jatropha oil for his study in diesel engine. Due to its high viscosity and high acid number, it cannot be used directly in diesel engines.
Raheman et al. had conducted experiments on Ricardo E6 engine using a vegetable oil named Mahua which is non edible, and he under goes esterification process to produce biodiesel from raw oil, and it is blended with diesel with certain percentage and the diesel engine is made to run at different compression ratios and injection timings.
.
Zheng m, mulenga mc . compression ignition engine which can generate a power of about 4.4KW. He achieved the results when the engine is loaded with twenty five percentage, fifty percentage, seventy five percentage and for hundred percentage. The thermal efficiency has been increased for about 2.4% in the single fuel operation. When hydrogen is mixed with rubber seed oil methyl ester in dual fuel operation, the peak efficiencies are 28.12%, 29.26% and 31.62% with rubber seed oil, rubber seed oil methyl ester, diesel and for hydrogen. While analyzing the emissions a small reduction in emission can be achieved for carbon monoxide and hydrocarbons.
Joshi H.c. carried out experimental studies to improve the
performance of rubber seed oil by exhaust gas preheating. Tests were
carried out on a Kirloskar TAF-1 single cylinder air-cooled; direct
injection, four-stroke diesel engine. He used the three variables like
diesel, raw rubber seed oil and preheated rubber seed oil. No
esterification technique is utilized in this work. carried out
experimental studies to improve the performance of rubber seed oil by
exhaust gas preheating. Tests were carried out on a Kirloskar TAF-1
single cylinder air-cooled; direct injection, four-stroke diesel engine.
He used the three variables like diesel, raw rubber seed oil and
preheated rubber seed oil.
Agarwal A K. Had conducted experiments on the utilization of rubber seed oil Methyl esters on A four stroke, direct injection, naturally aspirated single cylinder diesel engine. It is reported that Rubber seed oil extracted from the rubber seeds is having high free fatty acid content so it must undergo esterification process to bring the properties closer to diesel. The experiments are carried out by using different blends of methyl esters of rubber seed oil and using diesel as a fuel the combustion and emission characteristics are carried out in a single cylinder direct ignition diesel engine.
Hamasaki k,Tajima H. Had conducted experiments on Ricardo E6 engine using a vegetable oil named Mahua which is non edible, and he under goes esterification process to produce biodiesel from raw oil, and it is blended with diesel with certain percentage and the diesel engine is made to run at different compression ratios and injection timings. The results reveal that when the compression ratio has been increased the efficiency of the engine increases and proportional to each other. We can achieve good performance of the engine at higher compression ratios, because the ignition delay period is reduced. Normally methyl esters of vegetable oil are having low volatility when comparing with the diesel fuel.
Korbitz W,Friedrich S. The efficiency of the engine can also be increased by varying the injection timing of the engine. When the piston reaches the top dead centre the injection timing can be advanced from35° to 40° an improvement in thermal efficiency is seen. Similarly the exhaust temperature increases with the increase in blends of methyl ester; this can also be reduced when the engine is allowed to run at higher compression ratios. Even though biodiesel is safe to use in diesel engines and it can be blended with diesel fuel to any percentage at any compression ratios to reduce the emission and increasing the efficiency of the engine.
Kumar M S, Ramesh A. studied the performance and emission characteristics on an variable compression ratio diesel engine by varying the compression ratio and injection pressure. He selected the vegetable oil named jatropha for his experimental work, which is non-edible oil.
Result shows the relationship between the variables such as compression ratio and injection pressure. Initially the methyl ester utilized as a fuel in diesel engine is prepared in the chemistry laboratory using esterification process. He selected jatropha oil for his study in diesel engine. Due to its high viscosity and high acid number, it cannot be used directly in diesel engines.
CHAPTER 3
EXPERIMENTAL SETUP AND PROCEDURE
EXTRACTION OF BIO-DIESEL FROM RUBBER SEED
Rubber seed collected from the farm is not utilized for any other purpose, it is going out as a waste, to utilize this kernels in the seeds are removed before crushing and the oil is extracted by screw pressing. The extracted oil contains number of impurities and it is filtered before undergoing esterification process. The color of the pure rubber seed oil varies depending upon its acid value and normally it will be in light brown. The formation of methyl esters can be explained using the diagram which is presented below.
Diagram representing the biodiesel generation
The important properties and its ingredients of the rubber seed oil is mentioned in the table and it is compared with other non edible oil is indicated in the Table 3.1 The unsaturated fatty acids present for the different oils may vary depending on their growing conditions related with the soil and climate. The fatty acid present in the raw oil is having a value 17.5% and it may vary from place to place. Oils having high fatty acids must
undergo acid estrification .
From various studies it has been found that only by alkaline esterification biodiesel cannot be generated for oils having high acid value. Reduction in acid value plays a vital role in rubber seed oil; it can be reduced using the hydrochloric acid or sulphuric acid as a catalyst.
TRANSESTERIFICATION
Any vegetable oil needs esterification process before it is used as a fuel in engines. Methyl esters of oil are free from pollution because it belongs to the origin of plants. Esterification process is carried out by using alcohols such as ethyl alcohol or methyl alcohol. In the esterification process our motto is to remove the glycerol present in the vegetable oil to reduce its viscosity for complete combustion.
During esterification process the vegetable oil undergoes chemical reaction at constant temperature with continuous stirring. Without catalyst the reaction cannot takes place, so catalyst is the essential criteria for acid
and alkaline esterification. The amount of catalyst utilized in this reaction may vary depending upon the fatty acid present in the vegetable oil. Alkali-catalyzed transesterification is much faster than acid-catalyzed transesterification and is most often used commercially [2]. The esterification have made a great change in the vegetable oil by minimizing its viscosity. The biodiesel yield which we received after acid and alkaline esterification gives the better results in reducing its viscosity and by verifying with the properties of diesel it makes a very close results with diesel. The fuel properties such as calorific value, carbon reside, flash and fire point will match with the standard diesel.
Diesel engines can be fuelled with biodiesl with any engine modifications and it can undergo combustion for a long duration of time. By using biodiesel based rubber seed oil, the emission will be reduced and the efficiency can be improved by comparing with diesel. Vegetable oils in diesel increases the viscosity of the oil which leads to carbon deposit formation in the cylinder valves and coking takes place in the engine which leads to higher emissions in the exhaust. Methyl ester yield during esterification process hinders the reaction, some of the variables which affect the formation of methyl esters are:
Reaction temperature.
Molar ratio of alcohol and oil.
Catalyst.
Reaction time.
Presence of moisture and free fatty acids (FFA).
Effect of Reaction Temperature
Reaction takes place in the vegetable oil mainly deals with the temperature. Starting and completion of reaction takes in atmospheric temperature, normally the temperature ranges from (55-73°C). The maximum yields of methyl ester can be obtained in between the temperatures of 45 to 70°C [3]. Different experiments have been done on the temperature study with vegetable oils. Finally it can be concluded that the biodiesel yield may vary depending on the temperature when it undergoes acid and alkaline esterification.
Effect of Molar ratio
One of the other factors which affect the esterification yield is the molar ratio, The alcohol plays a vital role, when esterification takes. To make the reaction in a positive manner more amount of alcohol is utilized in the reaction and the excess alcohol can be removed by chemical treatments. To obtain a maximum methyl ester yield a molar ratio of 5:1 is preferred. In large scale production the molar ratio varies when compared with the batch process, and it is in the range of 6:1 which gives the maximum yield period.
Effect of Catalyst
A catalyst is the one which decides the yield of biodiesel in the vegetable oil. Many types of catalysts are available; normally we will be using acid and alkaline catalyst for better yield. The presence of fatty acids in the vegetable oils may vary depending on the type of the oil. Acid catalysts are used for acid reaction and alkaline catalysts are used for alkaline reaction.
Effect of Reaction Time
Transformation of raw oil to methyl ester takes place when it undergoes alkaline reaction under standard operating temperature with respect to its time. Initially the reaction is very slow and then it started moving in a faster manner depending upon time. Proper time is needed to complete the reaction, and the time limit may vary on its composition of fatty acids present in the vegetable oil.
Effect of Moisture and FFA
The water content present in the oil can be removed by doing preheating before going for acid esterification.
twenty minutes to remove the moisture content present in the vegetable oil. If the water content is present in the oil the reaction will not go in proper manner, which may leads to the formation of soap. Formation of soap reduced the yield of methyl esters and the alcoholic reaction will not proceed and finally we are not in a position to separate the glycerol and biodiesl. The industrial equipments are corroded when acid catalyst is used but alkaline catalyst is less corrosive. When the alkaline reaction is not moving ina proper manner it leads to formation of soap.
METHADOLOGY
Non edible oil sources contribute the major raw material for production of biodiesel. Biodiesel produced from various oils drastically varies in quality and the general characteristics depend upon the methods and modification adopted. The main aim is to generate methyl esters from non edible oil named rubber seed oil is low cost oil which is not used for any other purpose. Bio-diesel production from rubber seed oil includes the reduction of acid value to its minimum by acid-esterification followed by transesterification using alkali catalyst.
Acid esterification: The prime point is to reduce the acid number of the raw oil and it must be come down below 2% when acid catalyst is used.
O CH3 O
+ H CH3 H O
C C
OH 2
OH R
R O
Alkaline esterification: Before going for alkaline esterification the acid number must be reduced and the output of the acid esterification is used as an input for second stage.
O O
R O C R'
CH2 O C R'
CH2 OH
O O
+ 3ROH KOH OH + R
CH O C CH O C
R'' R''
CH2 OH
CH2 O C R'''
R O C R'''
O
Esterification Setup
The experimental set up is carried out in the chemistry lab in which a glass flask having the shape of round at the bottom is used for heating the oil. A heating element is utilized to heat the oil, which has a hot plate at the top. The oil is poured in the flask and is kept in heater in which a magnetic stirrer is coupled with it. The oil mixed with alcohol is heated and the mixture is stirred with a constant speed and the entire mixture is heated at a temperature of 40-60°C and the temperature is maintained throughout its entire process when experiments are conducted.
Acid Esterification to Reduce FFA
The main motto of acid esterification is to reduce the acid value of the raw rubber seed oil by using hydrochloric acid as a catalyst. Fifty milliliter of raw rubber seed oil is taken in the flask and it is heated at the standard temperature. Adequate amount of methanol and acid catalyst is added with the rubber seed oil, and the entire mixture is maintained at a constant temperature for about thirty minute with continuous stirring. The reaction is stopped after attaining the standard time and it is allowed to settle in the
Separating funnel. The excess alcohol with the impurities present in the oil is separated at the top in the separating funnel
Effect of Methanol/Oil Ratio
The molar ratio of methanol to oil is the major process parameter that affects the yield of biodiesel. Molar ratio is the ratio of number of moles of alcohol to number of moles of glycerides in the oil. Chemically, three moles of alcohol is required for esterification of each mole of oil. However, usually the molar ratio higher than three is needed for proper completion of reaction. Fig.3.2 shows the variation of biodiesel yield with methanol /oil ratio. It can be noted that the yield increases with methanol/oil ratio, and gets saturated above the molar ratio of 10.
Effect of HCl/Oil ratio.
Acid esterification studies was also carried out by varying the catalyst (HCl)concentration by keeping the methanol/oil molar ratio constant at 15:1. The variation of biodiesel yield was shown in Fig.3.3. The required amount of methanol is added with the preheated rubber seed oil and stirred for a few minutes. 0.4-0.6% of hydrochloric acid is also added with the methanol mixture.
Effect of methanol/oil molar ratio on biodiesel yield during acid
esterification
The entire mixture is heated and stirred continuously for a time duration of 25-30 minutes. When the reaction gets completed the entire mixture is poured in the separating funnel for removing the excess alcohol. The biodiesel yield increase with HCl concentration and reaches a maximum of 79 % at a ratio of 0.52. However the yield starts to decrease as the hydrochloric acid concentration increases. This decrease in yield with increase in catalyst concentration is the result of reversible hydrolysis. With these optimum process parameters the FFA values of raw rubber seed oil were reduced below 2 % and then subjected to alkali esterification in the second stage
Effect of HCl/Oil molar ratio on biodiesel yield during acid esterification
ALKALINE ESTERIFICATION TO PRODUCE BIODIESEL
The prime aim of the vegetable oil is to reduce its acid value of the raw rubber seed oil ranging from 36 to less than 4. After completing the acid esterification we got the rubber seed oil in its reduced acid number less than three and the reduced free fatty acid oil is used as an input for the second stage of alkaline esterification.
Effect of Methanol/Oil ratio.
In order to study the influence of methanol/oil ratio on yield, the other process parameters were held constant; say KOH/oil molar ratio as 0.008, temperature at 80°C.
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The variation of biodiesel yield with methanol/oil ratio is shown in Fig. 3.4. The biodiesel yield increases of methanol /oil concentration from 3.5 onwards, however the percentage of increase in yield decreases after the molar ratio of 7.5. Further increase of methanol/oil ratio will not increase the yield of biodiesel, which indicates that higher methanol concentrations are not required to increase the yield. Excess methanol in the ester decreases the flash point of the biodiesel [4].
Fig.3.4 Effect of methanol/oil molar ratio on biodiesel yield during alkali
esterification
Effect of KOH/Oil ratio.
In order to study the influence of alkali catalyst in the yield of biodiesel, the catalyst concentration was varied from molar ratio of 0.008 to 0.016 while keeping the other process parameter constant. The values of other parameters are the methanol/oil molar ratio of 6:1, temperature at 80oC with reaction time of 15 minutes.
The yield of biodiesel increases with the concentration of the alkali-catalyst to reach a maximum of 80.3% when the catalyst to oil ratio is 0.016. The use of higher
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catalyst concentration has the disadvantage of causing a parallel reaction viz. saponification against transesterification, thereby reducing the yield and introducing additional impurities in the system. The soap formed during the saponification will also cause emulsification of the biodiesel.
Effect of catalyst (KOH) on the yield of biodiesel during alkali esterification
Effect of Reaction Time
The effect of reaction time for the biodiesel yield is studied from 15 to 75 minutes by keeping other process parameters constant at the appropriate values mentioned above. The reaction was very slow during the first few minutes due to the mixing and dispersion of alcohol with oil.
That the yield is not affected much to a reaction time of 45 minutes. However, higher reaction time has a reverse effect on esterification process, leading to saponification and possible emulsification of the product. In fact, 15 minutes of reaction is quite sufficient to produce the maximum yield.
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Effect of reaction time on the yield of biodiesel during alkali esterification
Effect of Temperature
Temperature plays a vital role in the yield of methyl ester. Moderate temperature is maintained throughout the reaction for better yield. Fig.3.7 shows the variation of biodiesel yield with respect to its temperature. Maximum yield is achieved at a temperature of 65°C, further increase in temperature decreases the yield.
The boiling point of methanol is 65°C, and having reaction temperature above this is not advisable, because they tend to accelerate saponification process by the alkaline catalyst before completion of the alcoholysis.
Effect of temperature on the yield of biodiesel during esterification
MEASUREMENT OF FUEL CHARACTERISTICS
The biodiesel obtained after two stage esterification is then gone for purification in order to remove the impurities, excess methanol and catalyst. Water washing is done for three to four times for time duration of one hour. At most care is taken, in order to prevent from emulsification. Finally the methyl esters of rubber seed oil is dried by using pure silica gel. The approximate cost for raw oil is 12 Rs/liter, and the total cost for producing biodiesel will be around 43 Rs/liter. The purified biodiesel is then carried for finding the fuel properties to match with the diesel before going for combustion in diesel engines.
The properties of methyl esters such as viscosity, density, cetane number, cloud and pour points, flash and fire point, ash content, carbon residue and higher heating value are analyzed. The viscosity of Biodiesel is found out by Brookfield viscometer at a temperature of 45°C, which should be maintained constant throughout the process. The flash and fire point is found out by using the standard equipments. Heating value plays a vital role in the combustion, it can be found out by using parra calorimeter. The carbon content present in the biodiesel is found out by using micro carbon residue tester. The viscosity of the oil gets reduced after two stage esterification
OPTIMIZATION OF BIODIESEL
Acid Esterification
The acid value of raw rubber seed oil is higher and it is above 38 mg KOH/g. Methyl esters can be generated by alkaline esterification. Initially the acid value must be reduced below 4 mg KOH/g, then only the oil can undergone for alkaline esterification. In the first stage the maximum yield can be attained of about 98% when the oil is carried out under acid esterification. The effect of alcohol to oil, reaction temperature, acid catalyst, time duration, viscosity and acid number with different composition of several trials is shown in Table3.2. The lower layer after acid esterification is separated for further processing (alkaline esterification).
Alkaline Esterification
The output received from the acid esterification is used as an input for the alkaline esterification. The ranges for each experiment can be finalized through literature survey. For every trial about 50ml of oil is taken from the acid esterification and is heated in the round bottom flask with the desired temperature and required amount of methanol is added for alkaline esterification. Stirring is done continuously to making the reaction proper and the temperature is maintained constant throughout the reaction. After the stipulated time the entire reaction is stopped and it is allowed to pour in the separating funnel. The glycerol settles at the bottom of the separating funnel and the methyl ester is at the top. The impurities present in the methyl ester are removed by water washing and finally it is dried by using silica gel. The final result of biodiesel yield by weight percentage
Quantification Using Gas Chromatography
It is widely applied in the methyl esters to analyze the saturated and unsaturated fatty acids present in the mixture. The objective of the present work has been to maximize the yield of monoester. The total yield after esterification is calculated by using gas chromatography. The yield of biodiesel may vary depending upon the composition of alcohol with oil. The other parameters such as temperature and times also affect the yield of methyl ester. In chromatography about 5ml of biodiesel is injected into the analyzer in which normally an inert gas such as helium is utilized. The gas particles will react with the walls of the colum which is coated with different phases. The different composition present in the methyl ester is denoted by peaks which are displayed in the computer as an output is indicated
OPTIMIZATION OF ACID ESTERIFICATION PROCESS PARAMETER
Poor choice of factors and ranges results in unsatisfactory solution – no matter how good the experimental plan and ingenuity in data analysis. Accordingly, central composite design is employed in the first stage for acid esterification process to evaluate the relevance of these process parameters on the acid value. The planned experimental parameter for conducting experiments as per the procedure mentioned .
An analysis of variance (ANOVA) is then carried out for the response (acid value) in order to test the model signification and suitability.
The model p-value of 0.0099 indicates that there is only 0.99% chance that a
“Model F-value” of this large could occur due to noise, moreover p-value less than 0.05 indicate that the model terms are significant. In this model, factor A, which is the volume ratio of oil to methanol is the most significant model term. However the other parameters have less influence on the acid value of the oil extracted from raw rubber seed oil. The "Pred R-Squared" value of 0.1715 is in reasonable agreement with the "Adj R-Squared" value of 0.3648. The "Adeq Precision" measures the signal to noise ratio and ratio greater than 4 is desirable, whereas the model ratio is 6.746 indicates an adequate signal. With these statistical validations the model is used to navigate the design.
The perturbation plot compares the effect of all the factors about a particular point in the design space. The response (acid value) is plotted by changing only one factor (process varibale) over its range while holding the other factors constant.
is the perturbation chart for the acid value of the oil after acid esterification process. A steep slope or curvature in a factor shows that the response is more sensitive to that factor. The perturbation chart strengthen the claim that the factor A, oil/methanol ratio is the most influencing factor in deciding the acid value, by the steep positive slope.
OPTIMIZATION OF ALKALINE ESTERIFICATION PROCESS PARAMETER
It was possible to produce monoesters (biodiesel) by alkaline catalyzed esterification process only after reducing the FFA content of the unrefined oil by acid esterification process to less than 2%. The objective of the second step is to maximize the yield of monoester. The percentage yield was calculated by quantifying the different fatty acid composition present in the ester by gas chromatography, which is the most accurate method. The planned experimental process parameter for conducting experiments and their corresponding yield percentage of biodiesel (response) based on weight percentage as well as through gas chromatograph study .
CHAPTER 4
RESULT AND DISCUSSION
Characteristics of Rubber seed oil
Some of the relevant characteristics of the feedstock for biodiesel production were analysed by adopting standard methods.
Determination of Acid Number
About 1.00 ± 0.03 g of the rubber seed oil was titrated against standard potassium hydroxide solution (0.089 N), using phenolphthalein indicator and the acid number of the rubber seed oil which is also a measure of free fatty acid content, was determined.
Determination of Viscosity by Redwood Viscometer
In the viscometer oil container, 50 ml of the RSO was taken. The water jacket surrounding the oil container was heated by an electrical heater to 65oC. Continuous stirring allows the heat to get transferred between the sample and water, and when the temperature of the sample and water got equalized, the stopper rod was opened and the stop clock was switched on simultaneously. The time taken for the collection of 50 ml sample was noted down, by which the viscosity of the sample was determined .
Kinematic Viscosity (γ) = (At - B/t) centistokes, ------------------- (2) where,
A = a constant (0.226) B = a constant (171.5)
t = time taken to collect the 50 ml sample.
Determination of Density
Density of the feedstock was calculated, by weighing the sample against different volumes,
Density = Mass/Volume -------------------------- (3)
Determination of Peroxide Value
About 5.00 ± 0.05 g sample was weighed accurately into a 250 ml Erlenmeyer flask, 30 ml of acetic acid - chloroform solution (3:2) was added to the sample, and the contents were dissolved by swirling the flask gently followed by addition of 0.5 ml of saturated potassium iodide solution. The solution was allowed to stand for a minute. To the solution, 30 ml of distilled water was added and titrated.
against 0.01 N sodium thiosulfate (Na2S2O3) solution using starch as indicator when
the blue colour suddenly disappeared. A blank was carried out similarly and the
peroxide value calculated using Eq. 4,
Peroxide Value = (S-B) x N x 1000/ W -------------------- (4)
where,
S = Titre value of sample,
B = Titre value of blank
N = Concentration of the Na2S2O3 solution (0.01 N)
W = Weight of sample (g)
Determination of Saponification Value
About 1.00 ± 0.03 g of the sample was dissolved in 12.5 ml of 0.5 N ethanolic solution of KOH. The solution was refluxed using water condenser until the oily layer disappeared. The hot soap solution was titrated against 0.5 N HCl using phenolphthalein indicator when the pink colour disappeared. A blank was performed simultaneously and the saponification value was calculated using Eq.5,
Saponification value = 56.11 x N x (S - B) / W ----------------------- where,
N = Strength of HCl
S = Titre value for sample B = Titre value for blank W = Weight of sample (g)
FORMULATION OF PROBLEM
Several experimental studies on diesel engine fuelled with hundred
percent Rubber seed oil biodiesel report lower engine performance and
considerable variation in exhaust gas emissions at different operating conditions. Inefficient and incomplete combustion of bio-diesel due to the existing fuel injection system design and operating conditions are main causes for this. Thus there is a need to study the influence on engine operating parameters in order to optimize the combustion and emission characteristics of diesel engine by using Rubber seed oil methyl ester as fuel in different compression ratios. This investigation has been carried out with the following objectives.
i. Optimization technique using design of experiment for biodiesel extraction
ii. Various blends of biodiesel-diesel are used as fuel in a Variable Compression Ignition Engine.
iii. Effect of injection pressure at different nozzle opening conditions.
iv. Improved engine performance and emission reduction when the piston is coated with Copper, Magnesium oxide and Nickel.
The experimental results such as brake specific fuel consumption, brake thermal
efficiency and emissions (CO, HC, NOx and smoke) are also used to
optimize the engine with different fuels at different operating
conditions. Findings from this study also contribute to make settings
in engine parameters for replacing the diesel with alternative fuel
COMBUSTION AND EMISSION CHARACTERISTICS OF BLENDS OF
BIODIESEL AT CR= 16
The results obtained from the experimental investigation of the combustion, performance and emission parameters using B20, B40, B60, B100 & Diesel as fuels are presented and discussed in this section. The results are also compared with diesel fuel operation for different Compression Ratios.
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Brake Thermal Efficiency
The brake thermal efficiency of the engine is given by
BTE = 3600 / (CV × BSFC)
Where,
BTE = Brake thermal efficiency, %
CV = Calorific value of fuel used, kJ/kg
BSFC = Brake specific fuel consumption, g/kWh
40
35
30 CR=16
25
BTE(%) 20 Diesel
15 B20
B40
10 B60
5 B100
0
0 1 2 3 4 5
BP(kW)
Variation of brake thermal efficiency with brake power
The variation of brake thermal efficiency with respect to CR-16 for different fuels considered in the present analysis is presented in Fig.5.1. From the graph it can be analyzed that thermal efficiency increases with increase in load due to increase in power and reduction in heat loss.
From the observation of the results, it has been concluded that the brake thermal efficiency of the blend B20 is slightly higher than that of the standard diesel at CR-16.
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When the methyl ester of rubber seed oil is mixed with diesel, the molecules present in the methyl ester contains oxygen compounds which makes the combustion faster and it leads to complete combustion. Even though the biodiesel has some lubricity characteristics which makes the reaction faster at the time of combustion. The maximum brake thermal efficiency was 35% and 33% for B20 and B40 as compared to 32% for Diesel. By analyzing the graph when the biodiesel blend gets increases, the thermal efficiency starts decreasing due to reduction in heating value [6]. This is mainly due to longer ignition delay result in late burning which leads to a reduction in thermal efficiency.
Specific fuel Consumption
The fuel consumption of an engine is measured by determining the time required for consumption of a given volume of fuel [7, 8]. The time taken by the engine to consume the fuel is measured on its volume basis. The test engine has the provision for measuring both diesel and biodiesel. These two fuels are stored in separate tanks in the engine, initially the engine is fuelled with diesel and then it is switched over to biodiesel. When the stable operating conditions have been achieved the engine is allowed to run at different operating conditions.
The variation in BSFC with load for different fuels is presented in Fig.5.2. From the figure it can be noticed that the specific fuel consumption increases with increase in blend at low load and decreases with decrease in blend at high load may be due to the increase in viscosity of the blend.
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0.8
0.7 CR=16 Diesel
0.6 B20
Sfc(kg/kWh) B40
0.5 B60
0.4 B100
0.3
0.2
0.1
0
0 1 2 3 4 5
BP(kW)
Fig.5.2 Variation of specific fuel consumption with brake power
The mean BSFC for the blends was higher than that of pure diesel and it is to be noted as for every 20% additional blending of biodiesel in diesel. Increase in density of methyl esters causes higher injection pressure to inject the fuel in the combustion chamber. The lowest BSFCs are 0.22, 0.25, 0.28, 0.29 and 0.32 kg/kWh for diesel B20, B40, B60 and B100 respectively. The fuel consumption of any compression ignition engines depends on the characteristics such as volumetric fuel injection system, density, viscosity and lower heating value.
5.2.3 Peak Cylinder Pressure
In a compression ignition engine, the peak cylinder pressure depends on the burning of fuel inside the combustion chamber at the time of combustion. The variation of cylinder pressure with biodiesel and its blends in comparison with diesel fuel for compression ratio 16 is shown in Fig.5.3.
88
80
(bar) 75 Diesel B20 B40 B60 B100
70
Pressure CR=16
65
60
Peak
55
Cylinder
50
45
40
0 1 2 BP(kW) 3 4 5
Fig.5.3 Variation of cylinder pressure with brake power
It is noticed from the figure that the peak pressure for diesel increases from 47.5bar to 70bar for diesel from no load to full load and the cylinder pressure gets decreases when the biodiesel blends gets increases.
The maximum pressure of a diesel engine supports the combustion at the initial period which mixes in the premixed combustion period. The premixed combustion is dependent on the delay period and the mixture preparation [9, 10]. From the statistical approach it can be noticed that ignition delay takes place when the engine is fuelled with methyl esters and less delay period is seen when the engine undergoes combustion with diesel.
5.2.4 Combustion Duration
Increase in pressure rise reduces the combustion duration. When the piston reaches the top dead center, the maximum pressure is achieved for a long duration of time which gives the power stroke.
89
140
Diesel B20 B40 B60 B100
duration(Deg) 120
100
CR=16
80
Combustion
60
40
20
0 1 2 BP(kW) 3 4 5
Fig.5.4 Variation of combustion duration with brake power
Fig.5.4. shows the variation of combustion duration with brake power for different blends of biodiesel. When the engine operates at lean or rich mixture the rate of combustion can be increased and the reduction in flame propagation can be seen due to deficiency in oxygen compounds [11, 12]. The combustion duration is higher for increase in brake power for a compression ratio of 16. The highest combustion duration is noted as 105° crank angle at full load when the engine is fuelled with biodiesel and the lowest is about 74°crank angle for diesel . It can be observed that the combustion duration decreases with decrease in blend of biodiesel, which indicates faster heat release and leads to high thermal efficiency.
5.2.5 Exhaust Gas Temperature
The variation of Exhaust Gas Temperature with respect to brake power for blends of biodiesel when running at compression ratio 16:1 is presented in Fig5.5.
90
350
(°C) Diesel B20 B40 B60 B100
300
Temperature
CR=16
250
Gas 200
Exhaust 150
100
0 1 2 3 4 5
BP(kW)
Fig.5.5 Variation of Exhaust gas temperature with brake power
Normally exhaust gas temperature increases with increase in load for diesel and blends of biodiesel. The maximum temperature has been achieved for diesel fuel when it undergoes combustion from no load to high load and the temperature is recorded as 137°C at no load to 310°C at full load. When the engine is loaded in steps it consumes more amount of fuel to produce more power depending on the load. The pure methyl esters of rubber seed oil gives low exhaust temperature when compared with the diesel due to its low heating value and more oxygen compounds present in the biodiesel make the combustion complete.
The exhaust gas temperature was lower for blends of biodiesel than Diesel. The highest temperature recorded as 296°C for Diesel and for biodiesel it is recorded as 284°C. The reason being the lower calorific value of blended fuels compared to diesel and the lower temperature at the end of compression. Also, biodiesel is partially oxidized
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while burning, and it has lower temperature which results in reduced exhaust gas temperature.
5.2.6 Pressure - Crank angle Diagram
The cylinder pressure versus crank angle obtained at peak power output for full load is shown in Fig.5.6. The methyl esters of rubber seed oil gives longer ignition delay than the ordinary diesel fuel which starts the combustion later. The ignition delay for biodiesel is due to its lower content of volatile compound in comparison with the diesel. More energy is released in the latter part of the expansion process which will reduce the thermal efficiency and increase the exhaust gas temperature. When knock occurs high frequency pressure fluctuations are observed whose amplitude decays with time [13, 14]. It occurs late in the burning process and the amplitude of the pressure fluctuation is small. The initial amplitude of the pressure fluctuation is much longer thereby causing a shock wave to propagate away from the end gas region across the combustion chamber.
Fig.5.6 Variation of Cylinder pressure with Crank angle
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It can be noticed that the cylinder pressure is reduced when the flow rate is increased. It can be seen that Diesel has low peak pressure than rubber seed oil methyl ester when the engine is running at a compression ratio of 16:1. The maximum peak pressure is about 72 bar for biodiesel at full load conditions and the lowest peak pressure is about 62 bar for diesel. The premixed combustion is dependent on the delay period and the mixture preparation. Higher cetane number has the capability to reduce the ignition delay when fuel is send inside the engine cylinder which leads to the formation of increase in smoke at the engine exhaust.
5.2.7 Heat Release Rate
The combustion heat release profiles for Diesel & biodiesel for CR=16 at full load is shown in Fig 5.7. The profiles produces different ignition delays, longer delays allow more fuel to mix with in the combustible limits during the delay.
Fig.5.7 Variation of Heat Release with Crank angle
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It can be observed that the heat release rate for diesel is low when compared to biodiesel with respect to CR 16. In methyl esters of rubber seed oil higher heat release is observed, it can occur due to the premixed combustion phenomena, and when comparing it is higher than the diesel fuel. It may result due to the high viscosity of biodiesel which leads to reduced fuel air mixing and make the combustion earlier.
5.2.8 Smoke
The smoke from the Diesel engine using methyl esters of rubber seed oil and its blends with Diesel for a compression ratio of 16:1 is shown in Fig.5.8. When the combustion takes place inside the engine cylinder, the smoke level increases due to the increase in fuel for diesel and blends of methyl esters. When the load increases more amount of fuel is essential to produce more power, at this juncture the injected fuel won’t find the sufficient time for complete combustion, in which some of the partially burned fuel goes through the exhaust as smoke. It can be noticed that blends of methyl esters generates more smoke when comparing with the diesel fuel.
100
Diesel B20 B40 B60 B100
80
CR=16
60
Smoke(%)
40
20
0
0 1 2 BP(kW) 3 4 5
Fig.5.8 Variation of Smoke with brake power
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The recorded values of intensity of smoke generated for blends B20 to B100 were 16% and 27% at no load and for maximum load it is about 50% to 72% respectively.
The smoke level is higher with rubber seed oil methyl ester as compared to diesel, due to its improper atomization of fuel mixture. Normally in diesel engine smoke formation generally occurs in the rich zone at high temperatures [15].
5.2.9 Carbon monoxide (CO)
Incomplete combustion of carbon leads to CO formation. CO is a toxic combustion product. In the presence of sufficient oxygen, CO is converted into CO2. The formation of CO takes place when the oxygen for combustion is insufficient to form CO2. Intially at no load condition, less temperature is recorded inside the engine cylinder, but the temperature of the engine cylinder is increased at higher loads due to consumption of more amount of fuel inside the cylinder.
0.10
0.08 CR=16
CO (%) 0.06
0.04
0.02
Diesel B20 B40 B60 B100
0.00
0 1 2 3 4 5
BP(kW)
Fig.5.9 Variation of Carbon monoxide with brake power
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Formation of CO in the case of rich mixture mechanism seems to be primarily determined by the rate at which the fuel-rich zones within the fuel jets are fed with air. Both mechanisms involve chemical kinetics and hence are expected to be temperature sensitive [16]. Fig.5.9 shows the graphical representation of carbon monoxide emission for blends of methyl esters of rubber seed oil and diesel fuel when the engine is running at a constant speed at different loading. There is no much variation for Diesel and B20, due to similar properties of fuels.When the load of the engine increases the fuel air ratio is reduced which shoots the carbon monoxide higher. The maximum value of CO for rubber seed oil methyl ester is found to be 0.094% under full load conditions and the minimum value for diesel is found to be 0.052%. It was observed that during the initial period when the engine is running at zero load the temperature inside the cylinder is very low, and when it is loaded in steps to generate maximum power, more amount of fuel is injected in to the engine cylinder which leads to the formations of emission.
5.2.10 Unburned Hydrocarbons (HC)
Exhaust gases leaving the combustion chamber of an engine contains more amount of hydrocarbon components. This may result due to improper burning of fuels; due to increase in molecular weight of diesel fuel when it undergoes combustion the temperature gets increases and results in higher emissions.
96
70
60 CR =16
50
HC(ppm) 40
30
20
10 Diesel B20 B40 B60 B100
0
0 1 2 3 4 5
BP(kW)
Fig.5.10 Variation of Hydrocarbon with brake power
Combustion chamber phenomena and engine operating parameters will influence on hydrocarbon emission. Fig.5.10 shows the variation of hydrocarbon emission with different fuels when the engine is running at a compression ratio of 16:1. The hydro carbon level increases with increase in load for all the fuels. For rubber seed oil methyl ester the HC emissions are lower than that of diesel fuel. This may be due to the fact that pure biodiesel contains more oxygen and this leads to better combustion.
The HC emission for diesel fuel differs from 22ppm at zero load to 67ppm at peak load and for pure biodiesel it ranges from 16ppm at zero load to 40ppm at maximum load. As the ignition delay period increases the fuel mixture losses it efficiency and tries to become lean than the required combustion. Often this may occur at the periphery of the fuel spray, where vaporized fuel may be stripped off and carried away by the swirling air [17]. This leads to the reduction in HC emission for pure biodiesel than diesel
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5.2.11 Oxides of Nitrogen (NOX)
Nitric oxide emission is one of the major pollutants emerged from the engine exhaust when it undergoes combustion. It causes mainly due to increase in temperature during the combustion period. Normally NOx is measured in parts per million. Fig.5.11. shows the graphical representation for blends of methyl esters when the engines is allowed to run at a compression ratio of 16:1.
The nitric oxide emission from the engine exhaust for the blends of methyl esters of rubber seed oil varies from 235 to 674ppm and for diesel it varies about 222 to 475ppm. From the graph it can be concluded that increase in proportion of biodiesel with diesel increases the nitric oxide emission.
800
700
600 CR=16
(ppm) 500
400
X
NO 300
200
100 Diesel B20 B40 B60 B100
0
0 1 2 BP(kW) 3 4 5
Fig.5.11 Variation of Oxides of Nitrogen with brake power
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Methyl esters are oxygenated fuels; increase in oxygen content increases the exhaust gas temperature at the engine exhaust which leads to the formation of NOx. Normally increase in load increases the air- fuel ratio, which increases the temperature in the engine cylinder leads to generate higher nitric oxide emissions
COMBUSTION AND EMISSION CHARACTERISTICS OF BLENDS OF
BIODIESEL AT CR= 18
5.3.1 Brake Thermal Efficiency
The variation of brake thermal efficiency with respect to brake power for different blends of methyl esters of rubber seed oil when the engine is running at a compression ratios of 18:1 is shown in Fig.5.12. Normally thermal efficiency increases with increase in load for all fuels, but when comparing the maximum efficiency at full load for blends of biodiesel and diesel, methyl ester blend B40 gives the maximum efficiency of about 36%. This may cause due to the increase in percentage of oxygen in the biodiesel, which can go for complete combustion.
40
35
30 CR=18
BTE(%) 25
20 Diesel
B20
15 B40
10 B60
B100
5
0
0 1 2 BP(kW) 3 4 5
Fig.5.12 Variation of Brake thermal efficiency with brake power
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The blend B100 gives lower efficiency than the diesel fuel and it is recorded as 31%, which may cause due to the increase in viscosity and high density of the fuel. When comparing the efficiencies for the different blends it can be noticed that at full load conditions the efficiencies varies in a slight manner but major difference is noticed for the blends B40 and B100.
5.3.2 Specific fuel Consumption
The variation of specific fuel consumption with respect to brake power for different fuels for a compression ratio of 18 is considered for the present analysis is presented in Fig.5.13. From the graphical representation it can be noticed that the specific fuel consumption increases with increase in blend at low load and decreases with decrease in blend at high load, be due to the increase in viscosity of the blend. When low percentage of methyl ester is added with the diesel, the brake specific fuel consumption gets lowered and it matches close to diesel fuel.
0.8 Diesel
0.7 CR=18 B20
0.6 B40
Sfc(kg/kWh) B60
0.5 B100
0.4
0.3
0.2
0.1
0
0 1 2 BP(kW) 3 4 5
Fig.5.13 Variation of Specific fuel consumption with brake power
100
From the figure it can be noticed that the brake specific fuel consumption for the blends B20, B40, B60, B100 and Diesel is having a value of 0.24, 0.26, 0.27, 0.29 & 0.31 kg/kWh. By seeing the values it can be noticed that increase in viscosity of the blend the brake specific fuel consumption increases at maximum load conditions. The heating value of the fuel decreases when blends of methyl ester get increases, so that the engine is in a position to consume more amount of fuel to generate the power output.
5.3.3 Peak Cylinder Pressure
The cylinder pressure increases as combustion of the fuel-air mixture occurs. Fig. 5.14 shows the variation of in-cylinder pressure for Diesel, B20, B40, B60 & B100 with respect to crank position from no load to full load for compression ratio 18.
80
75 Diesel B20 B40 B60 B100
Pressure(bar) 70
65 CR=18
60
Cylinder 55
50
45
40
0 1 2 BP(Kw) 3 4 5
Fig.5.14 Variation of Cylinder pressure with brake power
The peak value of pressure depends on the fuel properties, combustion process and the engine load. As shown in figure the peak pressure of all the tested fuels increases with load, this may be due to more amount of fuel gets burned and the consequent release
101
of heat at higher loads. The peak pressure varies from 48bar at no load to 67bar at full load for diesel and the cylinder pressure gets reduced when it is blended with biodiesel.
It may be noticed from the figure that for a B100 blend the cylinder pressure drastically reduced from 42 bar to 54 bar. Normally in diesel engines the rise in pressure depends on the combustion phenomena in which it may vary depending on the fuel injection rate in the engine cylinder. This is because, ignition delay increases and longer delay leads to sufficiently late ignition occurring in the expansion process consequently leads to incomplete combustion and lower fuel conversion efficiency and power output [18].
5.3.4 Combustion Duration
Combustion duration mainly depends on the mixture of the fuel air ratio when the engine is operating in lean or rich mixture. Normally in lean mixture more amount of oxygen is present, so the fuel has a tendency to go for complete combustion when compared with the rich mixture. When the duration of combustion increases misfiring takes place inside the engine cylinder, which leads to the reduction in specific fuel consumption and this may leads to increase in thermal efficiency.
The variation of combustion duration with brake power for different blends of biodiesel is compared with diesel for compression ratio of 18 is indicated in Fig.5.15.The peak value of combustion duration depends on the fuel properties, combustion process and the engine load. The combustion duration for B60 & B100 is almost same and the highest value is noted as 89° & 94° CA and the lowest value for diesel is about 62° CA when the engine is running at full load conditions.
102
140
duration(deg) 120 Diesel B20 B40 B60 B100
100 CR=18
80
Combustion 60
40
20
0 1 2 3 4 5
Bp(kW)
Fig.5.15 Variation of Combustion duration with brake power
5.3.5 Exhaust Gas Temperature
Fig.5.16 shows the variation of Exhaust Gas Temperature with brake power for
the tested fuels when running at compression ratio of 18:1.
C)) 350
Diesel B20 B40 B60 B100
(° 300
Temperature
250 CR=18
200
Gas
Exhaust 150
100
0 1 2 3 4 5
BP(kW)
Fig.5.16 Variation of Exhaust gas temperature with brake power
103
The exhaust gas temperature varies from 155°C at no load to 295°C at full load for diesel fuel, from 145°C to 290°C for B20 and from 150°C to 274°C for rubber seed oil methyl ester. It can be seen from the figure that exhaust gas temperature lines for various fuel blends are closer to each other in a narrow band. The reason for lower exhaust gas temperature for biodiesel blends is due to its increase in viscosity, the fuel mixture cannot atomize in to fine spray in the combustion chamber, there by releasing lesser amount of heat [19].
5.3.6 Pressure - Crank angle Diagram
Fig.5.17 indicates the cylinder pressure with crank angle for different blends of biodiesel at maximum load conditions when the engine is running at a compression ratio of 18:1. Normally cylinder pressures are higher for blends of methyl esters of rubber seed oil when the engine is running at low loads. During peak loads the pressure fluctuations are noticed from the graph and it is similar for methyl ester blends. The peak cylinder pressure for biodiesel is 72 bar and for diesel is 63 bar at full load conditions.
Fig.5.17 Variation of Cylinder pressure with Crank angle
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Due to longer delays the combustion starts later for diesel than biodiesel during low loads. The cylinder pressure makes a value lower and it moves far from top dead centre during the expansion stroke. During high load the cylinder pressure makes near the crank angle for all the fuels. Increase in load reduces the delay period and it rises more quickly than the premixed burning phase.
5.3.7 Heat Release Rate
The variation of heat release rate with respect to crank angle for blends of biodiesel at compression ratio 18 is shown in Fig.5.18. Heat release rate is not a fundamental property of fuel, but the effective heat of combustion is a measure of how much energy is released when a unit mass of material is oxidized. Normally complete combustion can be mentioned as the release of energy takes place inside the engine cylinder when the fuel undergoes chemical reaction leaving no fuel inside the engine cylinder.
Fig.5.18Variation of Heat Release with Crank angle
105
The diagram represents that when the engine is running with twenty percentage blends of biodiesel reduced in ignition delay can be found when it is compared with diesel. From the graph it can be noticed that the heat release curves fluctuates steeply during peak loads and it comes to the normal position when the engine is running at no load. This may occur due to the increase in density of the rubber seed oil methyl ester which cannot go for proper atomization when the fuel is sprayed inside the combustion chamber. Due to incomplete combustion the exhaust temperature gets increased and finally it leads to increase in emission.
5.3.8 Smoke
Fig.5.19 depicts the variation of smoke density with respect to brake load for blends of biodiesel when running under compression ratio 18:1 is discussed below. It may be observed that smoke decreases with decrease in biodiesel blends. This is due to uniform mixture present inside the cylinder which leads to complete combustion and higher heat release rate in the premixed combustion phase.
100
Diesel B20 B40 B60 B100
80
(%) CR=18
60
Smoke 40
20
0
0 1 2 BP(kW) 3 4 5
Fig.5.19 Variation of Smoke with brake power
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From the graph it can be noticed that when the percentage of methyl ester blend gets increases, due to its incomplete combustion, smoke increases when the engine is running at full load conditions. The maximum value of smoke for rubber seed oil methyl ester is about 78%. and for diesel it is 59%. The lowest smoke emission can be seen for the blend B40, it may results due to the complete combustion of the fuel by the presence of oxygen in the biodiesel. The aromatic content in the blend is increased with constant cetane number, particulate emission increases at high load [20, 21]. Increase in smoke can be seen for higher blends, this may cause due to incomplete combustion of rubber seed oil methyl esters.
5.3.9 Carbon monoxide (CO)
The variation of carbon monoxide emission with engine loading for different fuels when running at a compression ratio of 18:1 is shown in Fig5.20.
0.10
0.08 CR=18
CO(%) 0.06
0.04
Diesel
B20
0.02 B40
B60
0.00 B100
0 1 2 BP(kW) 3 4 5
Fig.5.20 Variation of Carbon monoxide with brake power
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The carbon monoxide emission varies from 0.018% at no load to 0.049% at full load for diesel fuel, for rubber seed oil methyl ester it varies from 0.024% at no load to 0.085% at full load respectively. It can be seen that when the blends of biodiesel is increased the carbon monoxide emission also increases drastically. It is found that for B20 & B40 the CO emission reduces than the 100% biodiesel, this is due to the fact that oxygen present in the blends may lead to complete combustion thereby lowering CO emissions.
The enrichment of oxygen owing to rubber seed oil addition as increasing the proportion of oxygen will not only decrease the incomplete combustion products such as CO especially during the diffusive combustion process, but also promote further oxidation of CO during the engine expansion and exhaust process. The study reveals that operating on the oxygenated fuels would reduce the engine incomplete combustion products as a result of oxygen enrichment [22, 23].
5.3.10 Unburned Hydrocarbon (HC)
Emission characteristics vary depending on the combustion phenomena of an engine. When the fuel injected in to the engine cylinder is not mixed properly with air and during combustion it leads to higher hydro carbon emissions. The variation of hydrocarbon emission level with break power for blends of biodiesel is depicted in Fig.5.21 when the engine is running at a compression ratio of 18:1. From the graph it can be noticed that the hydro carbon emissions for Diesel, B20, B40, B60 & B100 are 62, 59, 54, 48 & 43ppm respectively. By analyzing the emission results it can be concluded that increase in rubber seed oil methyl ester blend decreases the hydro carbon levels. It is one
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of the fact that the oxygen concentration present in the biodiesel undergoes complete combustion thus reduces the hydrocarbon level in the engine exhaust timing.
70
60
50
HC(ppm) 40
30
20
10 Diesel B20 B40 B60 B100
0
0 1 2 3 4 5
BP(kW)
Fig.5.21 Variation of Hydrocarbon with brake power
The hydrocarbon emission also varies depending on the injection timing of the fuel. If the injection is advanced before its desired timings, loner delay occurs which leads to higher emissions of hydrocarbons in the exhaust of the engine.
5.3.11 Oxides of Nitrogen (NOX)
The variation of NOX with brake power for diesel fuel and blends of biodiesel when running under a compression ratio of 18:1 is indicated in Fig.5.22. The NOX emission varies from 160ppm at low load to 440ppm at full load for diesel fuel, while for biodiesel it varies from 260ppm at low load to 660ppm at full load. The major cause for nitric oxide emission depends on the temperature occurs inside the engine cylinder during combustion and the presence of nitrogen present in the atmospheric air.
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800
700 Diesel B20 B40 B60 B100
600
(ppm) 500 CR=18
400
X
NO 300
200
100
0
0 1 2 3 4 5
BP(kW)
Fig.5.22 Variation of Oxides of nitrogen with brake power
Due to increase in load more amount of fuel is injected in to the engine cylinder and when it undergoes combustion it releases more amount of temperature in the engine cylinder which leads to NOX formation. In the case of methyl esters of rubber seed oil, the viscosity of the biodiesel is higher than diesel which makes the combustion delay and leads to nitric oxide emission. The reason for higher NOX for the blends is due to higher peak temperature at the time of combustion in the engine cylinder.
.
CHAPTER-5
CONCLUSION
CHAPTER-6
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