1. Introduction In day today’s applications, though the economic and environmental aspects do not agree to the usage of diesel, it is not promising to accomplish the habitual livelihood without the usage of diesel engine. Therefore it is enforced to formulate the usage of diesel in an economic and environmentally benign way. The emission from the diesel engines seriously disturbing the living beings. This work was aimed at to study the effect adding n-propanol with diesel on performance, combustion and emission characteristics of a four stroke diesel engine.
It was revealed that the combustion of diesel in a compression ignition engine occurs in three major stages like ignition delay, pre-mixed combustion phase and diffusion combustion phase. Of these, the ignition delay period which is the time period between the start of injection and the onset of combustion, have influence on all ignition processes. Various studies have already been done to improve the performance and reduce the emission by using different types of neat bio-diesel, blending different bio-diesels with diesel at varying proportions, introducing some modifications in the fuel supply system and in the combustion chamber, and blending different additives with diesel. Many researchers have done number of experimental investigations to use vegetable oils as fuel in diesel engines, and reported that the very high viscosity and low volatility of vegetable oils resulting in poor atomization slow burning, more smoke emissions and uncontrolled combustion. The exhaust gas temperature increase and NOx reduction with a slight increase in CO emission while using diesel blended with vegetable oil as fuel were observed. The usage of palm oil as fuel in diesel engines reported that the short term usage of palm oil augments the performance and emission levels considerably and the prolong usage causes carbon deposits and piston rings sticking. The usage of preheated vegetable oil as fuel, reduces the problem of filter clogging, also increases the engine performance and reduces the carbon deposits. The usage of cotton seed oil as fuel, without doing any modifications in the engine concluded that the engine parameters need to be readjusted in order to have the maximum power output and highest thermal efficiency. The experimental investigation on a DI compression ignition engine by using honge, neem and sesame oil methyl esters as fuel resulted that the performance and emission characteristics are comparable. The higher viscosity of biodiesel tends to reduce the engine power and engine torque, also the lower calorific value of biodiesel results in the increase in specific fuel consumption and decrease in combustion temperature. The usage of biodiesel derived from rice bran oil concluded that there is an increase in NOx emissions due to the presence of molecular oxygen in the bio-diesel. The experimental investigation on the diesel engine while using linseed oil, rice bran oil and mahua oil with diesel, reported that blending of 50% linseed oil with diesel increases the smoke density and decreases the brake specific energy consumption, and also concluded that the mixing of 30% mahua oil with diesel reduces the smoke density and increases the thermal efficiency as compared to diesel. The modifications in the engine received significant attention among the engine researchers in order to improve the performance and combustion characteristics, and reduce the emission from the diesel engine. The adoption of exhaust gas recirculation technique reduces the NOx emission considerably. The various experimental investigations by advancing the injection timing and increasing the injection pressure reported that there is an appreciable increase in brake thermal efficiency and decrease in CO, HC and smoke emissions. In recent years, considerable attention is given on the usage of primary alcohols as additive or blend with diesel. The usage of alcohols in compression ignition engine has its own intricacy due to its high latent heat of vaporization and long ignition delay period. However, it was reported that the usage of alcohols as blend in proper proportion with diesel reduces the exhaust emissions. The bioethanol derived from vegetable oils was considered as the most suitable alternate fuel because of its better spark characteristics and higher cetane number values. The blending of bioethanol with diesel appreciably reduces the green house gas emission. The usage of biodiesel blended with alcohols reported that there is an increase in brake thermalefficiency and decrease in CO, HC and NOx emissions. In this experimental study, n-propanol was identified and blended with diesel as an additive in varying proportions like 2%, 4%, 6%, 8% and 10% by volume. The various performance, combustion and emission characteristics of the diesel engine while using diesel blended with n-propanol at different proportions and at different loading conditions were evaluated. The various performance, combustion and emission parameters of the engine thus evaluated were analyzed and compared with that of the engine while using normal diesel as fuel. 1.2 Methodology a) Materials used The normal diesel supplied by Indian Oil Corporation was procured from the local market. The npropanol supplied by Kemphasol Limited, Mumbai was taken for blending with diesel. The blended fuels were prepared by mixing n-propanol at different proportions like 2%, 4%, 6%, 8% and 10% by volume with diesel.The complete mixing of n-propanol with diesel was done with the help of a mechanical stirrer. The various properties of diesel and n-propanol are given in Table 1. Table 1: Properties of diesel and n-propanol used
S. No. Property Unit Diesel n- propanol
1. Molecular formula -- C14H22 C3H7OH
2. Lower calorific value kJ/kg 43,200 30,680
3. Specific gravity -- 0.83 0.802
4. Kinematic viscosity cSt 2.6 2.8
5. Latent heat of vaporization kJ/kg 250 779
6. Cetane number -- 49 15
1.2 Experimental set-up For experimentation, a stationary single cylinder diesel engine with the specifications mentioned in Table 2 was used. The engine was coupled with an eddy current dynamometer. A computerized data acquisition system was attached with the engine to measure and record various performance and combustion parameters like fuel flow rate, speed of the engine, temperature of incoming air, temperature of exhaust gas, pressure inside the cylinder, heat release rate, etc. The AVL 444 Di gas exhaust gas analyzer manufactured by AVL, Austria was used to measure the amount of CO, CO2, NOx, O2 and HC present in the exhaust emission. The AVL 413 smoke meter was used to measure the smoke density. The layout of the experimental setup was shown in the figure 1. Figure 1. Experimental setup 1. Engine, 2. Eddy current dynamometer, 3. Fuel tank, 4. Air box, 5. Fuel flow sensor, 6. Pressure sensor, 7. Speed sensor, 8. Crank angle encoder, 9. Load cell, 10. Data acquisition system, 11.Computer, 12. Five gas analyzer, 13. Smoke meter. 1.3 Experimental procedure Initially, at no load conditions, the engine was started using normal diesel as fuel. After getting warmup,the load was applied on the engine at the rate of 20% of full load, through the eddy current dynamometer and the engine was allowed to run for a while. After the engine reaches equilibrium condition, the various performance, combustion and emission characteristic parameters were observed and recorded. The load was then increased to 40% of full load and the engine was allowed to run for some time to reach the equilibrium condition. After reaching the equilibrium conditions, the various performance,combustion and emission parameters were noted as per the standard procedure. By adopting the same procedure, the various parameters were observed and recorded for higher loads such as 60%, 80% and 100% of full load. From the observed and recorded values, the various parameters such brake thermal efficiency,brake specific energy consumption were evaluated by using standard relations. Then the diesel mixed with 2% n-propanol was used as fuel; by repeating the same procedure, the parameters related to performance, combustion and emission characteristics were observed and recorded at different load ranges. From the observed values, by using standard relations, the various performance, combustion and emission characteristics of the engine were calculated. The same procedure was then repeated to evaluate the performance, combustion and emission characteristics of the engine for other blended fuels such as 4%, 6%, 8% and 10% of n-propanol blended with diesel. The various characteristics thus evaluated were compared and analyzed with that of the engine using normal diesel as fuel. From the observed, recorded and calculated values, the various performance, combustion and emission characteristics of the engine while using diesel and different blended fuels at different loading conditions were presented in the form of graphs. Table 2: Engine specifications
S. No Parameter Specification
1 Engine model Kirloskar TV-1, DI, Naturally aspirated, Water cooled
2. Number of cylinders 1
3. Bore 87.5 mm
4. Stroke 110 mm
5. Compression ratio 17.5
6. Maximum power at rated rpm 5.2 kW
7. Rated speed 1500 rpm
8. Injection pressure 220 bar
9. Injection timing 23° before TDC
1.4 Uncertainty analysis The operating environment and usage of various measuring instruments may cause some error and uncertainty in the observed and calculated values. The accuracy of the direct measuring instruments was given in the table 3. By using the uncertainty analysis based on Gaussian distribution method with a confident limit of ±2σ, the overall uncertainty for the performance parameters in the experiment was calculated as ±1.5%. Table 3:Accuracy of the measuring instruments
S. No. Name of the instrument Parameters Measuring range Accuracy
1. AVL 444 Digas - 5 gas analyzer CO 0 – 10 % volume <0.6 % vol: ±0.03% vol
CO2 0 – 20 % volume <10 % vol: ±0.5% vol
O2 0 – 22 % volume >2 % vol: ± 5% vol
HC 0 – 20000 ppm volume >200 ppm vol: ±0.5% of ind value
NOx 0 – 5000 ppm volume >500 ppm vol: ±10% of ind value
2. AVL 413 Smoke meter Smoke density 0 – 100 % opacity ± 2%
1.5 Results and Discussion The comparison and analysis made on the various graphs drawn resulted in the following discussions. Comparison of Performance Parameters 1.5(a) Brake thermal efficiency Figure 2 shows the relation between brake thermal efficiency and load. From the graphs, it was noted that the brake thermal efficiency is almost same at low and medium loads for all the blended fuels. But above 60% load, the brake thermal efficiency increases for all the blended fuels, moreover the increase in percentage of n-propanol with diesel increases the brake thermal efficiency. At full load, the brake thermal efficiency is increased by 3.907%, 6.541%, 7.773%, 9.462% and 11.784% for the addition of 2%, 4%, 6%, 8% and 10% npropanol with diesel respectively. The increase in brake thermal efficiency due to the addition of alcohols was already evidenced. The addition of alcohol with diesel decreases the viscosity of the blended fuels. The decrease in viscosity improves the spray characteristics and resulted in higher brake thermal efficiency. The increase in brake thermal efficiency may also due to the higher premixed combustion of alcohol blended fuels because of low cetane number which lead the higher percentage of combustion at constant volume. Figure 2: Brake thermal efficiency Vs Load 1.5(b) Brake specific energy consumption Figure 3 indicates the graphs drawn between brake specific energy consumption and load. From the graphs, it was observed that the brake specific energy consumption at low and up to medium loads is almost same for all blended fuels, and decreases from medium load to full load for all blended fuels. The lower viscosity and higher volatility of n-propanol blended with diesel improves the spray characteristics, fast vaporization and thereby efficient combustion. At full load, the brake specific energy consumption decreases by 3.763% for 2% addition, 6.139% for 4% addition, 7.214% for 6% addition, 8.646% for 8% addition and 10.543% for 10% addition. The decrease in brake specific energy consumption is also due to the lower calorific value of n-propanol. Figure 3: Brake specific energy consumption Vs Load 1.5(c) Exhaust gas temperature Figure 4 depicts the variation of exhaust gas temperature with respect to load. From the graphs, it was clear that at lower loads, the exhaust gas temperature for all blended fuels is slightly higher than that of diesel. But at medium and at full loads, the exhaust gas temperature for all the blended fuels is lower when compared with that of diesel. The reduction in exhaust gas temperature is due to the higher latent heat of vaporization and the quenching effect of n-propanol in the combustion chamber. Figure 4: Exhaust gas temperature Vs Load. 1.6 Comparison of Combustion Parameters 1.6(a) Peak cylinder pressure Figure 5 shows the magnitude and occurrence of peak cylinder pressure which were found from the history of cylinder pressure and crank angle at full load and at the rated speed of the engine. From the graphs, it was observed that the cylinder pressure curves for diesel and all blended fuels are similar in shape. The small variation in maximum cylinder pressure while using blended fuels was already reported by Gong Yanfeng et al. Figure 5: Peak pressure Vs Load 1.6(b) Heat release rate Figure 6 indicates the heat release rate of diesel and various blended fuels between the crank angle variation -30° and 90° when the engine is running at full load. From the graphs, it was observed that the maximum heat release rate is 138.6 kJ/m3for diesel at 11° BTDC, 157.9 kJ/m3 for 2% n- propanol with diesel at 10° BTDC, 154.2 kJ/m3 for 4% n- propanol with diesel at 10° BTDC, 155.6 kJ/m3 for 6% n- propanol with diesel at 10° BTDC, 148.1 kJ/m3 for 8% n- propanol with diesel at 10° BTDC, 163.2 kJ/m3 for 10% npropanol with diesel at 10° BTDC. Here the increase in heat release rate for blended fuels is due to the increase in spray characteristics by the addition of n- propanol. The quenching effect and reduction in cylinder temperature due to the high latent heat of vaporization of n- propanol delayed the maximum heat release rate. Figure 6:Heat release rate Vs Load 1.6(c) Total heat release Figure 7 depicts the total heat release during a cycle. From the graphs, it was noted that the accumulated heat release rate is higher for all blended fuels at full load. This is due to the increase in flame travel speed and spray characteristics due to the addition of n-propanol which is supported by Gong Yanfeng et al. Figure 7:Total heat release Vs Load 1.7 Comparison of Emission 1.7(a)CO Emission Figure 8 indicates the relation between the CO emission and load. From the graphs, it was observed that the CO emission decreases gradually up to 60% load on the engine for all fuels, then the CO emission gradually increases up to 80% load, and after that it increases rapidly up to full load. The sharp increase in CO emission at full load is because, when at high load the mixture supplied to the engine is rich. It was also noted that, the CO emission for all blended fuels is greater than that of diesel at low and medium loads. This is due to the reduction in in-cylinder temperature by the higher latent heat of vaporization of n-propanol. But at full load, the reduction in CO emission is 5.882% for 4% addition, 14.706% for 6% addition, 23.529% for 8% addition and 44.118% for 10% addition of n-propanol with diesel. This is due to the fact that at full load, the in-cylinder temperature is high which makes better combustion. Figure 8: CO Emission Vs Load 1.7(b)CO2 Emission Figure 9 shows the graphs drawn between CO2 emission and load. Since the CO2 emission highly influences the green house effect and global warning, it is necessary to measure the CO2 emission from the engine. From the graphs, it was observed that the CO2 emission increases gradually as the load increases for all blended fuels and also the emission of CO2 is almost less for all blended fuels at all load ranges. This is because of the lower operating temperature due to high latent heat of vaporization of n-propanol. Figure 9: CO2 Emission Vs Load 1.7(c) HC Emission Figure 10 represents the graphs drawn between HC emission and load. The graphs concluded that the HC emission is more for all blended fuels and at all load ranges. Moreover the HC emission increases with the increases in load. Here it was noted that the increases in percentage of n-propanol with diesel increases the HC emission, the rate of increase in HC emission at medium load is higher than that at higher load. This may be due to the high latent heat of vaporization of n-propanol, which leads the development of quench layer, reduction in temperature inside the cylinder, slow vaporization and incomplete mixing. Figure 10: HC Emission Vs Load 1.7(d) NOx Emission Figure 11 indicates the presence of NOx in the engine exhaust with respect to load. The NOx formation is highly influenced by combustion temperature25. From the graphs, it was observed that the NOx emission increases with the increase in load for diesel and various blended fuels. Moreover at all load ranges, the NOx emission is less for all blended fuels when compared with that of diesel. At 60% load on the engine, the decrease in NOx emission is 12.446% for 2% addition, 14.077% for 4% addition, 15.193% for 6% addition, 26.438% for 8% addition and 28.584% for 10% addition of n-propanol with diesel. The high latent heat of vaporization and lower calorific value of n-propanol reduces the in-cylinder temperature which in turn reduces the NOx emission26. Since NOx is the most harmful, the reduction of it holds a prime important in the engine research. Figure 11:NOx Emission Vs Load 1.7(e) Smoke density The graphs drawn between smoke density and load are given in figure 12. It was observed that the smoke density increases with the increase in load for diesel as well as all blended fuels. The smoke density is less for all blended fuels at low and medium loads and it is high for higher loads. For 2% addition of npropanol with diesel, at 20% load, the smoke density gets decreased by 30.555%, and at 100% load the smoke density gets increased by 17.658%. This is due to the fact that the richness of the mixture increases with the increase in load and the reduction in in-cylinder temperature is due to high latent heat of vaporization of the blend. Figure 12: Smoke density Vs Load 2.BLENDING USING JATROPHA 1. Introduction The petroleum fuels fulfill our energy needs in industrial development, transportation, agriculture sector and many other basic requirements. These fuel reserves are fast depleting due to excessive usage. Besides combating the limited availability of crude oil, researchers are also dealing with other associated serious problems with petroleum fuel such as increase in pollutant emissions like: CO2, HC, NOx, Sox and many other .These pollutants cause diseases of the respiratory/nervous system, skin infection and acid rain phenomenon also occurs due to these emitted pollutants. One of the very important issues catching the attention of researchers worldwide is rise in green house gases (GHGs) emissions levels due the usage of petroleum fuels. In last few years volatility in the pricing of petroleum and its products has seriously affected the political-economic scenario of nations around the whole world. Hence, the need to search alternative to petroleum fuels is inevitable. India imports more than seventy percent of its crude oil requirement. Almost forty percent of all the quantity of petroleum products consumed in India is diesel. As evident from the Figure 13, petro-diesel consumption is showing an increasing trend. Sector wise petro-diesel consumption in India shown in Figure 14 indicates that automobile sector comprising of commercial and passenger vehicles is the largest consumer followed by industry and agriculture. Figure 13. Consumption of petro-diesel, petrol and total petroleum products in India Recent sales trend of automobiles in India clearly indicates increasing dominance of petro-diesel vehicles as compared to petrol vehicles. Mileage and price differential relative to petrol vehicles is the major factor leading to increased sales trend petro-diesel vehicles in India. Moreover latest CI engines being used in Indian automobiles have less operational noise, vibrations and maintenance issues as compared to their primitives Figure 14. Sectorwise petro-diesel consumption in India Self-sustainable energy sources are likely to hold the key to economic development of India in future. India should not look towards a certain group of countries to meet its ever growing petroleum needs but it is mandatory to seriously implement bioenergy development programs as a part of environmental sustainability in the form of clean development mechanism (CDM) . The much required green energy revolution would provide India an opportunity to change its standing from a fuel-importing nation to one that generates clean and affordable energy. Hence researchers are looking for techno-economically alternatives to petro-diesel. India being agriculture based economy, with more than sixty percent of population still living in rural areas, locally grown biodiesel can be a viable source of meeting their energy needs on a reasonable cost. Among various alternatives to diesel, Government of India (GoI) has identified jatropha, a non-edible oil bearing tree capable of producing oil that is easily convertible in to biodiesel with properties almost similar to diesel. Jatropha curcas plant is a drought-resistant, perennial plant living up to 50 years and has the capability to grow on marginal soils. It requires very little irrigation and grows in all types of soils, thus making Jatropha a more sustainable choice than other vegetable oils. In the longer run economic sustainability of jatropha biodiesel will definitely prove to be the best bet for India as far as economic viability of biodiesel w. r. t. diesel is concerned .Production of jatropha biodiesel would also result in reclamation of degraded/waste land, help in supplementing the ever increasing energy demand in line with the requirements of higher targeted growth rate and may also fulfill other social objectives such as: additional employment generation and participation of marginal laborers without threatening the food security with a sustainable ecosystem. An integrated approach realizing the monetary benefits of CDM is required to be implemented with proper co-ordination amongst the various governmental and nongovernmental organizations to achieve the targeted production of jatropha biodiesel. Biodiesel, a methyl or ethyl ester (ME or EE) of fatty acids made from vegetable oils (both edible and non-edible) and animal fat is looked upon as potential supplement/alternative to petro-diesel. Biodiesel can be used in its pure form or as a blend with petro-diesel in different proportions. It is being used in diesel engines because it has properties similar to petro-diesel as shown in Table 1. Important properties of both diesel and jatropha biodiesel (JME) like: density, viscosity, cetane number, calorific value and carbon content are comparable. Moreover JME has negligible sulfur content, reducing the chances of SOx emissions which cause acid rains. Better self-lubrication property of biodiesel is also attributed to the lesser sulfur content, which causes reduced wear & tear of engine and its components. Biodegradability of ME due to its oxidation leads to lesser damage to flora and fauna in case of accidental spillage. Inbuilt oxygen content helps in ensuring proper combustion and lesser release of carbon monoxide (CO). Table 4.Properties of diesel and Jatropha biodiesel The objective of this study is to explore performance of petro-diesel (B0) blended with JME (B100) in 5% (B5), 20% (B20), 50% (B50) and 80% (B80) by volume in direct injection CI engine used extensively for agricultural applications under varying load conditions. It is mandatory to experimentally validate suitable blends to be used as fuel in the engines in future with better performance, lesser emissions and optimum level of noise and vibrations. 2.1 Experiment and experimental set-up Constant speed (1500 rpm) short-term engine performance (STEP) tests were conducted on a 3.7 kW single cylinder, naturally aspirated, four-stroke Kirloskar engine at varying load. The fuel used in the engine was B0, B5, B20, B50 and B100. The major specifications of the Kirloskar engine are presented in Table 5. The engine was coupled to a hydraulic dynamometer for application of load and opening the water inlet valve increased the load and vice-versa. Table 5. Kirloskar Engine Specifications Experimental setup as shown in Figure 3 was used for performance and emissions analysis. In this study following operational parameters were focused upon while analyzing the performance of an engine like specific fuel consumption (the ratio of amount of fuel consumed in kg/hr to power output in kW), volumetric efficiency (breathing ability of an engine) and brake thermal efficiency (the ratio of brake power to heat input). Figure 15. Experimental setup of single cylinder four stroke diesel engine with hydraulic dynamometer AVL make exhaust and flue gas analyzer were used to determine the percentage of smoke opacity, HC, CO2, CO, O2 and NOX in the exhaust with the range mentioned in Table 3. For every blend, the engine was started and after it attains stable condition, important parameters related to its performance were recorded. The engine was operated at the speed of 1500 ± 10 rpm. The engine was then tested at 13.33%, 20%, 40%, 60%, 80% and 100% load. As per the test rig specifications, at rated power, i.e. at full load (100%), the hydraulic dynamometer is to be loaded with 7.5 kg load for given arm length. The engine at the above mentioned loads was tested on all the fuel blends discussed above. For each load condition, the experiment was repeated three times. 2.2 Results and discussions The Brake specific fuel consumption (BSFC) was calculated by fuel consumption divided by the rated power output of the engine. Figure 4 shows that variation of BSFC with load. SFC is showing an increasing trend for B80 and B100 for higher loadings. For B0 to B50 fuel consumption is decreasing with respect to increase in loading. Higher SFC can be attributed to the lower calorific value of biodiesel than that of diesel and poor atomization of blended JME with petro-diesel to its higher viscosity and density. Lowest BSFC is observed for B0 (254.5 g/kW hr) than B5 (268.4 g/kW hr) and B20 (278.5 g/kW hr) at 13.33% load. As a blended fuel B20 has marginally higher BSFC than B0. Highest BSFC is observed for B100 (597.5 g/kW hr) at 13.33% load. B80 and B100 fuel were found to give lowest BSFC at 60% load implying that the impact of higher viscosity and density is minimal. Figure 16.BSFC vs load Figure Figure 17 shows that variation of brake thermal efficiency with load. The BTE of the engine was observed to increase with increase in the load and was found maximum for B-0 (32.05%) at 100 % of load. This implies that the engine running on B0 fuel has good full load efficiency. For B5 (30.56%) and B20 (30.01%) BTE was lower as compared to that of B0 at 100% load due to lower calorific value, higher viscosity and density. For higher blends B50 and above, full load BTE is lower as compared to that of B0. This could also be attributed to the high mass flow rate of fuel inside the engine cylinder on account of larger density of JME as compared to diesel. Lower volatility, high viscosity and density of B50, B80 and B100 cause poor atomization and combustion and hence lower efficiency. Poor atomization leads to improper nuclei formation for initiation of combustion. Moreover larger density and viscosity of B50 and above blends leads to utilization of more amount of heat energy for initiation and completion of combustion thus leading to lower thermal efficiency. Figure 17.Thermal efficiency vs load Hydrocarbon (HC) emissions at varying load on different blends are shown in Figure 6. Lowest value of HC emissions at 17-21 ppm is observed for B50. Highest value of HC emissions is observed for B0 (65 ppm) at 100% load. HC emissions for B20 are in the range of 24-32 ppm. Lower HC emissions are very strong criteria favouring the usage of blended diesel in place of pure diesel. Cetane number of JME being higher than diesel, leads to a shorter delay period and results in better combustion resulting in lower HC emission. Also the intrinsic oxygen present in the fuel B5 to B100 was responsible for the reduction in HC emission. Since a long time diesel is known to emit large amount of soot particles which may cause serious respiratory disorders in human beings. B20 depicts lower HC emissions even at higher loading. Slightly higher HC emissions are observed at higher loading for B80 and B100 primarily due to higher viscosity and density causes improper Air/Fuel ratio resulting in improper combustion. Lower HC emissions may lessen the wear of key engine parts, compared with diesel. It is attributed to the lower soot formation, and the inherent lubricity of biodiesel. The higher oxygen content and lower aromatic compounds also reduces HC emissions. Figure 18. Hydrocarbon emission vs load The variation of oxides of nitrogen (NOx) emission for different blends is indicated in Figure 7. The NOx emission for all the fuels tested resulted in an increasing trend with respect to load. NOx emissions are higher for B-5, B-20, B-50, B80 and B100 as compared to B-0. NOx emission depends upon the maximum combustion temperature. Higher combustion temperature of blends is the main reason for increasing NOx. The lowest combustion temperature is for B-0. Therefore, total heat developed is comparatively low and lowest emission in NOx is observed for B-0. The reason could be the higher average flue gas temperature at higher load conditions. The amount of fuel injected increases with the engine load in order to maintain the power output and hence the amount of heat release and the exhaust gas temperature rise with increase in load. Suitable NOx reducing catalyst are being developed which can take care of this issue Figure 19.NOx emission vs load The variation of exhaust gas temperature for various blends with respect to the load is indicated in Figure 20. The exhaust gas temperature for all the fuels tested increases with increase in the load. The amount of fuel injected increases with the engine load in order to maintain the power output and hence the heat release rate and the exhaust gas temperature rise with increase in load. Exhaust gas temperature is an indicative of the quality of combustion in the combustion chamber. Exhaust temperatures for B0 were in the range of 143°C to 441°C. At all loads, B100 was found to have the highest temperature of 561°C and the temperatures for the different blends showed a upward trend with increasing concentration of JME in the blends. This is due to the increased heat release rate owing to higher SFC. The increased exhaust gas temperature may heat the combustion chamber also thus putting extra load on engine cooling and lubrication system. This may enhance the requirement of coolant and lubricating oil in the engine. Increased combustion chamber temperature may itself cause detonation of injected fuel. Thus more field trials are required in hot areas in order to establish validity of JME blends with petro-diesel. Figure 20. Exhaust gas temperature vs load. Figure 21 shows variation of smoke opacity with different blends at different loads. Smoke opacity increases with clogged, worn, mismatched injectors, misadjusted injection timing, clogged or worn fuel filters and restricted air filters. During experimental work Injector fouling took place while operating CI engine using diesel blended with JME. Excessive gum deposits were observed around injector which might have fouled the injector. Injection timing needs readjustment while using different fuel in the engine. Smoke opacity showed an increasing trend for diesel blended with biodiesel. B20 showed lower opacity compared to B50, B80 and B100 fuel. It is due to heavier molecular structure and higher viscosity; atomization becomes poor and this leads to higher smoke emission. Figure 21. Smoke opacity vs load It is interesting to note that the engine emits more CO for diesel as compared to diesel blended with JME under all loading conditions. It is seen from Figure 10 that the CO concentration is marginally present for the blend of B50 for all loading conditions and as the JME concentration in the blend increases above 50%, very marginal presence of CO is observed. At lower JME concentration, the oxygen present in the JME aids for complete combustion. Lower ignition delay due to higher cetane number also results in complete combustion. However, as the JME concentration increases, the negative effect due to high viscosity and small increase in density suppresses the complete combustion process which produces small amount of CO. At heavy loading B80 and B100 shows increase in CO emissions. This may be due to the incomplete combustion of larger quantity of fuel inducted during testing. Figure 22.CO emission vs load Figure 23 depicts the CO2 emission of various fuels used. The CO2 emission increased with increase in load for all blends. B20 and B50 fuel emits less amount of CO2 in comparison with diesel. B50 emits least amount of CO2 emissions. This is due to the fact that biodiesel in general is a low carbon fuel and has a lower elemental carbon to hydrogen ratio than diesel fuel. Using higher content JME blends, an increase in CO2 emission was noted, which is due to the incomplete combustion as explained earlier. Though at higher loads, higher JME blends emit higher amount of CO2, normally biodiesels themselves are considered carbon neutral because, all the CO2 released during combustion is sequestered from the atmosphere for the growth of the vegetable oil crops. Figure 23. CO2 emission vs load Advantages • Biodiesel fuel is a renewable energy source unlike petroleum-based diesel.
• An excessive production of soybeans in the world makes it an economic way to utilize this surplus for manufacturing the Biodiesel fuel.
• One of the main biodiesel fuel advantages is that it is less polluting than petroleum diesel.
• The lack of sulfur in 100% biodiesel extends the life of catalytic converters.
• Another of the advantages of biodiesel fuel is that it can also be blended with other energy resources and oil.
• Biodiesel fuel can also be used in existing oil heating systems and diesel engines without making any alterations.
• It can also be distributed through existing diesel fuel pumps, which is another biodiesel fuel advantage over other alternative fuels.
• The lubricating property of the biodiesel may lengthen the lifetime of engines.
Disadvantages • At present, Biodiesel fuel is bout one and a half times more expensive than petroleum diesel fuel.
• It requires energy to produce biodiesel fuel from soy crops, plaus there is the energy of sowing, fertilizing and harvesting.
• Another biodiesel fuel disadvantage is that it can harm rubber hoses in some engines.
• As Biodiesel cleans the dirt from the engine, this dirt can then get collected in the fuel filter, thus clogging it. So, filters have to be changed after the first several hours of biodiesel use.
• Biodiesel fuel distribution infrastructure needs improvement, which is another of the biodiesel fuel disadvantages.
CONCLUSION · The blending of n-propanol with diesel shows almost same brake thermal efficiency at low and medium loads, and higher percentage addition of n-propanol augments the brake thermal efficiency at high loads. · The blending of n-propanol with diesel reduces the brake specific energy consumption at medium and high loads. · The addition of n-propanol with diesel results in the reduction in engine operating temperature which in turn increases the life of the engine. · The addition of n-propanol with diesel appreciably reduces the CO emission over the medium and high load ranges. · The blending of n-propanol with diesel results in significant reduction in NOx emission over the entire load ranges. Since NOx is the most harmful, the reduction of it holds a prime important in the engine research. Presented experimental work shows higher BSFC, exhaust temperature and lower BTE with JME blended diesel. Higher exhaust temperature of JME blends can be attributed to the increased heat release rate owing to higher SFC. The increased exhaust gas temperature may heat the combustion chamber also thus putting extra load on engine cooling and lubrication system. This may enhance the requirement of coolant and lubricating oil in the engine. Increased combustion chamber temperature may itself cause detonation of injected fuel. Thus more field trials are required in hot areas in order to establish validity of JME blends with petro-diesel. Higher BSFC for B5, B10, B20, B50 and B100 fuel is due to lower calorific value of JME as compared to diesel. Lower HC, CO2, CO emissions during the usage of JME blended with diesel is a positive attribute related to lowering of regulated emissions. Considering stringent emission norms smoke opacity is a possible impediment to adoption of biodiesel. Considering comparable BSFC and BTE of B20 w.r.t. diesel along with lower regulated emissions and lesser noise and vibrations observed for B20 fuel it can be concluded that maximum blending percentage of JME with diesel shall be kept as 20%. HC emissions for biodiesel are significantly reduced, compared with diesel. The higher oxygen content, advance in injection and combustion of biodiesel and lower aromatic compounds has been regarded as the main reasons. NOx emissions increase when using biodiesel mainly due to higher oxygen content and cetane number for biodiesel. The further studies on the low temperature performance of biodiesel engine should be fulfilled because biodiesel presents higher viscosity than diesel, which could affect the emissions due to the different size of droplets for biodiesel and diesel without any change in fuel nozzle. Improvement in properties and quality of biodiesel should be incorporated in the future. And the further development in additives which improve consumption of biodiesel should be needed to enhance power output and reduce emissions especially NOx emissions. It should be done to readjust or redesign engine or/and its control systems for biodiesel, especially for optimizing ignition and injection, and EGR control to achieve a more efficient combustion and thus meet the needs of biodiesel engine. The further studies on biodiesel engine endurance tests should be carried out to clarify the reason and mechanism of wears. Lastly, biodiesel, especially for the blends with a small portion of biodiesel, is technically feasible as an alternative fuel in CI engines with no or minor modifications to engine. From environmental and economic perspectives, their popularity may soon grow. However, more researches and development in biodiesel resources and engine design are needed in India to make it feasible specifically in rural areas. 5. References 1. Heywood, J.B. Internal Combustion Engine Fundamentals, McGraw-Hill, Inc., New York, 1988. 2. Wang, Y.D., T. Al-Shemmeri, P. Eames, J.Mcmullan, N. Hewitt, and Y. Huang. An experimental investigation of the performance and gaseous exhaust emissions of a diesel engine using blends of a vegetable oil. Applied Thermal Engineering, 2006, 26, 1684–91. 3. Tadashi Young. Low carbon build up, low smoke and efficient diesel operation with vegetable oil by conversion to monoesters and blending of diesel or alcohols. SAE 841161, 1984. 4. Murayama T. Low carbon flower build -up, low smoke and efficient diesel operation with vegetable oil by conversion into monoesters and blending with diesel or alcohol SAE. 1984, 5, 292-301. 5. Wang YD, AZ-Shemmeri T, Eames P, McMullan J, Hewitt N and Huang Y. An experimental investigation of the performance and gaseous exhaust emission of a diesel engine using blends of a vegetable oil. Applied Thermal Engineering, 2006, 26, 1684-1691. 6. Shahid E.M. Jamal Y. A review of biodiesel as vehicular fuel. Renewable and Sustainable Energy Reviews. 2008, 12(9), 2484-2494. 7. Petroleum Planning and Analysis Cell (PPAC). Available at: www.ppac.org.in, accessed in September 2011. 8.Sethi V. India’s Demand Outlook. India-IEA Seminar on Global Oil Market Outlook & Stability. New Delhi, India, October 2009. .