The Effect of Bio-Fuel Blends and Engine
Load on Diesel Engine Smoke Density for
Sustainable Environment
R. K. Mandloi *, Prof. A. Rehman
Mechanical Engineering Department M. A. National Institute of Technology.
Bhopal-462051 (M P) India. *E-mail: profrkmandloi@yahoo.com
Abstract
The diesel engine is a major contributor to air pollution especially within cities and along urban traffic routes. Therefore it has become very essential to develop the technology of IC engines, which will reduce the consumption of petroleum fuels and exhaust gas emissions. In fact, agricultural and transport sectors are almost diesel dependent. The various alternative fuel options researched for diesel are mainly biogas, producer gas, ethanol, methanol and vegetable oils. Out of all these, vegetable oils offer an advantage because of its comparable fuel properties with diesel and can be substituted between 20%-100%depending upon its processing. But as India still imports huge quantity of edible oils, therefore, the use of non-edible oils of minor oilseeds like Karanji oil has been tested as a diesel fuel extender. The problems have been mitigated by developing vegetable oil derivatives that approximate the properties and performance and make them compatible with the hydrocarbon-based diesel fuels through the pyrolysis, micro emulsification, dilution and transesterification. The various fuel blends of karanji oil were tested on different engine loads to evaluate it smoke density.
Key Words: MEKO (Methyl Esters Karanji Oil), Karanji-Fruit Contains Non Edible Oil
Introduction
The diesel engine is a major contributor to air pollution especially within cities and along urban traffic routes, in addition to air pollution that cause ground level ozone and smog in the atmosphere, diesel exhaust also contains particulate and hydrocarbon toxic air contaminants (TAC). Various harmful effect of exhaust emission are already established and known to today's society. Therefore it has become very essential to develop the technology of IC engines, which will reduce the consumption of petroleum fuels and exhaust gas emissions.
The various biomass based resources which can be used as an extender or a complete substitute of diesel fuel may have very significant role in the development of agriculture, industrial and transport sectors in the energy crisis situation. The role of diesel fuel in these sectors cannot be denied because of its ever increasing use. In fact, agricultural and transport sectors are almost diesel dependent. The various alternative fuel options researched for diesel are mainly biogas, producer gas, ethanol, methanol and vegetable oils. Out of all these, vegetable oils offer an advantage because of its comparable fuel properties with diesel and can be substituted between 20%-100%depending upon its processing. The various edible vegetable oils like sunflower, soybean, peanut, cotton seed etc1 have been tested successfully in the diesel engine. Research in this direction with edible oils yielded encouraging results. But as India still imports huge quantity of edible oils, therefore, the use of non-edible oils of minor oilseeds like Karanji oil has been tested as a diesel fuel extender.[1]
mitigated by developing vegetable oil derivatives that approximate the properties and performance and make them compatible with the hydrocarbon-based diesel fuels through the pyrolysis, micro emulsification, dilution and transesterification.
The work reported here it was decided to carry out the experimental investigation to ascertain the possibility of using hen-edible modified karanji oil test fuels by transestertication methods in naturally aspirated diesel engine with various oil modifications. To determine the effects of varying operating engine load, Compression ratios, performance and emission characteristics of compression ignition engine with modified karanji oil fuel blends and diesel fuel.[3], [5]
Methodology:
Vegetable Oil Fuel Blends for C. I. Engines
Out of all alternative fuel options for diesel, vegetable oil in the form of blends or transesterified form emerged out as promising source as fuel extenders. Vegetable oil can be used in diesel engine without engine modifications. The alternative diesel fuels must be technically and environmentally acceptable, and economically competitive. From the viewpoint of these requirements, triglycerides (vegetable oils/animal fats) and their derivatives may be considered as viable alternatives for diesel fuels. The problems with substituting triglycerides for diesel fuels are mostly associated with their high viscosity, low volatility and polyunsaturated character. The problems have been mitigated by developing vegetable oil derivatives that approximate the properties and performance and make them compatible with the hydrocarbon-based diesel fuels through the pyrolysis, micro emulsification, dilution and transesterification. [2]
Pyrolysis: Pyrolysis refers to a chemical change caused by the application of thermal energy in the absence of air or nitrogen. The liquid fractions of the thermally decomposed vegetable oil are likely to approach diesel fuels. The pyrolyzate had lower viscosity, flash point, and pour point than diesel fuel and equivalent calorific values. The cetane number of the pyrolyzate was lower.
Micro-emulsification: The formation of micro emulsions (co-solvency) is one of the potential solutions for solving the problem of vegetable oil viscosity. A micro-emulsion can be made of vegetable oils with an ester and dispersant (co-solvent), or of vegetable oils, an alcohol and a surfactant and a cetane improver, with or without diesel fuels.
Dilution: Dilution of vegetable oils can be accomplished with such materials as diesel fuels, solvent or ethanol.
Trans-esterification: Trans-esterification also called alcoholysis is the displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis. This process has been widely used to reduce the viscosity of "triglycerides. Triglycerides are readily trans-esterified in the presence of alkaline catalyst at atmospheric pressure and at a temperature of approximately 60 to 70 C with an excess of methanol. [2],[3],[5]
The most important variables that influence trans-esterification reaction time and conversion are: a) Oil temperature.
b) Reaction temperature. c) Ratio of alcohol to oil.
d) Type of catalyst and concentration. e) Intensity of mixing.
f) Purity of reactants.
a) Oil Temperature: The temperature to which oil is heated before mixing with catalyst and methanol, affects the reaction. It was observed that increase in oil temperature marginally increases emulsification, dilution and transesterification. However, the tests were conducted up-to only 60Deg. as higher temperatures may result in methanol loss in the batch process.
proceed satisfactorily at ambient temperatures in the case of the alkaline catalyst.
c) Ratio of alcohol to oil: Another important variable affecting the yield of ester is the molar ratio of alcohol to vegetable oil. A molar ratio of 6: 1 is normally used in industrial processes to obtain methyl ester yields higher than 98% by weight. Higher molar ratio of alcohol to vegetable oil interferes in the separation of glycerol. It was observed that lower molar ratios required more reaction time.
d) Catalyst type and concentration: Alkali metal alkoxides are the most effective transesterification catalyst compared to the acidic catalyst. Sodium alkoxides are among the most efficient catalysts used for this purpose, although potassium hydroxide and can also be used. Trans methylations occur many folds faster in the presence of an alkaline catalyst than those catalyzed by the same amount of acidic catalyst. Most commercial transesterification is the alkaline catalyst concentration in the range of 0.5 to 1 % by weight yields 94 to 99% conversion of vegetable oil into esters.
e) Mixing intensity: The mixing effect is most significant during the slow rate region of the transesterification reaction. As the single phase is established, mixing becomes insignificant. The understanding of the mixing effects on the kinetics of the trans-esterification process is a valuable tool in the process scale-up and design. It was observed that after adding methanol & catalyst to the oil, 5-10 minutes stirring helps in higher rate of conversion and recovery.
f) Purity of reactants: Impurities present in the oil also affect conversion levels. Under the same conditions, 67 to 84% conversion into esters can be obtained, using crude vegetable oils, compared with 94 to 97% when using refined oils. The free fatty acids in the original oils interfere with the catalyst. However, under conditions of high temperature and pressure this problem can be overcome. It was observed that crude oils were equally good compared to
refined oils for production of bio-diesel [3],[5]
Proposed BIS Standard for Bio-diesel
Standard Specification Unit BIS Std.
Density @ 150C G/Cm3 0.87 – 0.9
Viscosity @ 400C Mm2/s 3.5 – 5.0
Flash Point 0C 100
Sulphur,max % mass 0.035
CCR,100% Distilation Reside,max % mass 0.5
Sulphated ash, max % mass 0.02
Water max mg/kg 500
Total Contamination mg/kg 20
Cetane number - 51
Acid number mg KOH/g 0.8
Methanol % Mass 0.02
Ester content % Mass 96.5
Mono glyceride % Mass 0.8
Di glyceride % Mass 0.2
Tri glyceride % Mass 0.2
Free glycerol % Mass 0.02
Total glycerol % Mass 0.25
Phosphorous ppm 10
Objectives:
possibility of using hen-edible karanji oil in naturally aspirated diesel engine with various oil modifications. The specific objectives were:
i) To prepare the modified karanji oil test fuels by transestertication methods ii) Blending esterified karanji oil with diesel in different proportions
iii) Performance and initial study of engines using bio-diesel iv) Performance of bio-diesel blends and its optimization
To determine the effects of varying operating engine load, Compression ratios, performance and emission characteristics of compression ignition engine with modified karanji oil fuel blends and diesel fuel.
Conclusion:
The review of report literature highlights these points. There is considerable scope of increase in the production of oilseed in India by extending irrigation facilities, cultivating waste land for oil seed cropping and adopting suitable technologies. Using efficient expellers can also increase vegetable oil production.
A comparison of physical and fuel properties of vegetable oils with those of diesel fuel indicate that vegetable oils are quite similar in nature to diesel fuel and can be used as diesel engine fuel.
Problems encountered with the use of straight vegetable oil, vegetable oil blends and heated oils in the present day unmodified compression ignition engines include injector chocking, increased carbon deposits in combustion chamber and piston ring grooves, increased lubricating oil contamination and marginally higher wear rate. These problems are however not insurmountable. Pure esters of vegetable oil show a better response, although lubricating oil contamination is there.
The approaches for using vegetable oils as supplementary/ substitute diesel engine fuel include the use of vegetable oil ester (bio-diesel), vegetable oil blends with diesel and heated vegetable oils before injection. These are primarily aimed to reduce the viscosity of vegetable oils.
Experimental investigations reported by various researchers established the possibility of the use of different vegetable oil esters and oil blends in diesel engines.
While using blends up to 30% concentration of vegetable oil and diesel reported similar engine performance without any modification in engine as given by neat diesel fuel. [3, 4]
Test on the Engine:
To ascertain the possibility of use of modified karanji oil as fuel for compression ignition engine the performance test were conducted. The comparison of the test fuels was made with diesel base line values. The comparison standards were specific energy consumption and smoke density. Test fuels' performance analyzed are for esters of karanji oil, blends of karanji oil, and the diesel oil as baseline at varying loads performed at governor controlled speed. The variation in the injection parameters were analyzed to observe its influence on the engine performance with different fuels. To get the picture of the effect of variation of injection timing, the test was performed at 4 settings.
0 10 20 30 40 50 60 70
100 200 300 400 500 600
BMEP (Kpa) S m ok e D e ns ity ( H S U )
Diesel MEKO 30KO 50KO
0 10 20 30 40 50 60 70
Diesel 50KO 30KO MEKO Fuel S m ok e D ens ity ( H S U ) BMEP:150KPa BPEM:300KPa BPEM:450KPa BPEM:600KPa
Fig1 Effect of load in terms of BMEP on exhaust smoke density Fig2 Effect of different fuel on smoke density at different
with different fuel. fuel injection timing.
Effect of Load on Smoke Density:
Smoke density in the exhaust depends upon fuel combustion and carbon content of the fuel. Fuel combustion depends upon fuel cetane number, viscosity and density of fuel. Cetane number indicates fuel response during combustion in CI engines as it is related to fuel self ignition temperature. Self ignition temperature is related to rate of heat release. Higher viscosity and density influences spray pattern, mixing and hence combustion.
Figure shows the effect of load and injection pressure on exhaust pressure at best injection timing comparable with base line diesel value.
RESULTS AND DISSCUSSION
1. Diesel as convenient fuel compared to all the test fuels. Further, It is also seen that with the blends of esters in diesel i.e. 30% esters and 50% esters in diesel respectively the SEC has a lower
value as compared to MEKO. This may be attributed to improved properties of blends being similar to diesel than MEKO.
2 The calorific value of esterified karanja oil found to be 36.76 MJ/kg which is 17.95% lower than that of diesel. 3 Comparable smokes found for karanja oil methyl ester with that of diesel fuel.
References
[1] S.Kalligeros, F. Zannicos and S. Stournas: Biomass & Bio-energy, 24(2003) 141-149 [2] A. Rehman and Phadatare: Bio-energy News Sept. (2003) 17-23
[3] J.G. Suryawanshi and N.V. Deshpandey: ASME, ICEF (2004) 866 [4] S. Patel and B.K.Mishra: Science Tech Entrepreneur, 12, 08(2004) 59-61
[5] A. S. Huzayyin, A.H. Bawdy and M.A. Rudy: Energy Conversion & Management 45 (2004) 2093-2112 [6] D. Kusdiana and Saka Shiron: Bioresources Technology 91(2004) 289- 295
