CHAPTER 2 LITERATURE REVIEW

Transcription

1 24 CHAPTER 2 LITERATURE REVIEW 2.1 GENERAL In the recent years efforts have been made by several researchers to use biofuel as fuel to the engines. During use of biofuel some measures has to taken to solve the problems of long-term operational and durability problems e.g. poor fuel atomisation, piston ring- sticking, fuel injector coking and deposits, fuel pump failure and lubricating oil dilution, etc..these problems are avoided by adopting of two different possibilities: adaption of fuel to the engines, and adaption of engines to the fuel. In this present work adaption of engines to the fuel has been tried and given in the following categories: 1. Biofuel with standard diesel blends operated in direct injection diesel engine with standard and various compression ratios. 2. Biofuel with standard diesel blends in direct injection diesel engine with exhaust gas recirculation. 3. Biofuel with standard diesel blends operated in thermal barrier coated diesel engine.

2 BIOFUEL WITH DIESEL BLENDS OPERATED IN DIRECT INJECTION DIESEL ENGINE WITH STANDARD AND VARIOUS COMPRESSION RATIOS. The use of biofuel in diesel engines has to be widely investigated because of their availability and their inherent proprieties. The biofuel (Eucalyptus and Turpentine) used in this study has low cetane number as compared to the standard diesel fuel. As part of attempt to understand better, the performance, combustion and emission benefits of biofuel (Low cetane fuel) and their diesel blends as fuel in diesel engines, many literatures were studied and it is summarised in this section. Poola et al (1994) investigated the performance, combustion and exhaust emissions characteristics of spark-ignition engines at two different compression ratios of 7.4 and 9.0 using eucalyptus oil and orange oil as alternative fuels. It was reported that most of their properties were similar in nature to those of gasoline and they were miscible with gasoline without any phase separation. Eucalyptus oil is an effective co-solvent that prevents the alcohol-gasoline blended fuel from undergoing phase separation. One of the reasons is the fact that, eucalyptus oil is quite similar to the naphthenic base in its chemical structure. It was found that the octane value of the eucalyptus oilgasoline blend was higher compared to that of gasoline. Tests were conducted using 20% volume of orange oil and eucalyptus oil that were blended separately with gasoline and the performance, combustion and exhaust emission characteristics were evaluated at two different compression ratios. The results indicated that the performance of the fuel blends was much better than that of gasoline fuel, in particular, at higher compression ratio. Hydrocarbons and carbon monoxide emission levels in the engine exhaust were considerably reduced with fuel blends at both the Compression Ratios

3 26 (CRs) tested. Between the two fuel blends tested, the eucalyptus oil blend provided better performance than the orange oil blend. Maximum improvement in brake thermal efficiency was obtained at the higher compression ratio of 9. In comparing the two fuel blends tested, the eucalyptus oil blend provided the potential for a high brake thermal efficiency concomitant with low exhaust emissions. Purushothman and Nagarajan (2009) investigated the use of orange oil in single cylinder compression ignition engine. The orange oil exhibits a longer ignition delay than diesel fuel. The heat release rate and brake thermal efficiency are higher as compared to diesel fuel.smoke emission such as HC, CO and smoke emission were reduced considerably except NO X emission. Murat Karabektas and Murat Hosoz (2009) conducted test on single cylinder, direct injection diesel engine powered by diesel fuel and isobutanol blends.four different isobutanol-diesel fuel blends containing 5, 10, 15 and 20% isobutanol were prepared in volume basis and employed in the experiments along with pure diesel. The experiment was conducted at full load condition and at the speeds between 1200 and 2800 rpm with the intervals of 200 rpm. The test results showed that there is increase in the BSFC in proportional to the isobutanol content in the blends. Break thermal efficiency was higher for diesel fuel as compared to four blends. Emission such as CO and NO X emissions decreased with the use of the blends, whereas HC emission increased considerably. Ashok et al (2008) conducted experiments on single cylinder direct injection diesel engine powered by diesel and emulsified fuel in the ratios of 90D: 10E, 80D: 20E, 70D: 30E and 60D: 40E and tested at different load conditions. Brake thermal efficiency increased by 3.45% for emulsified fuel as

4 27 compared to the diesel fuel. From the results, it was also revealed that there was reduction in specific fuel consumption and smoke emission and simultaneously there was increase in NO X and particulate matter. 80D: 20E was much suitable for getting good performance and low emission of the engine. Takeda (1984) conducted experiments on the utilisation of eucalyptus oil and orange oil in small passenger cars. It was reported that eucalyptus oil obtained from leaves by means of steam extraction, contains 1.8-cincole (C 10 H 18 O) as the main ingredient. It was reported that in using 100 % of eucalyptus oil, there existed a difficulty in the engine starting under the low atmospheric temperature because of the high flash point of eucalyptus oil. He also conducted experiments using eucalyptus oil, gasoline, ethanol and their blended fuels. The various distilation curves were obtained from the use of six kinds of fuels, based upon the distilation curve; eucalyptus oil presented some difficult in starting the engine. It was also reported that the distilation temperature for eucalyptus oil is 167 C and 45 C for gasoline. This difficulty, however, was not experienced in the case of a blended fuel of gasoline and eucalyptus oil. It was further reported that the phase separation problem was not noticed when the eucalyptus oil was blended with ethanol and gasoline. One of the reasons citied for this fact was that, as eucalyptus oil (C 10 H 18 O) is quite similar to the napthenic base in its chemical structure, it played the role of a third material, which can easily combine both the materials. The flame propagation velocity of eucalyptus oil appears to be slightly higher than that of gasoline. In the second part of the paper, results of the road test were reported. This included the study on the wear and carbon deposit in the engine parts while the car tested in road conditions. It was founded that there were no critical problems on start ability and drivability while driving the vehicle. However, carbon deposits were found on the position head, exhaust port and combustion chamber. The carbon deposit

5 28 consisted of 60% carbon and a few percent of CaSO 4 Fe, and Zn. The carbon deposit caused by eucalyptus oil on the piston head was less than that found when the gasoline was used. It was also observed that no abnormal conditions were found including oil leakage of fuel system, deformation of the fuel system and cracks on the cylinder head. Carbon deposit was found slightly on the piston head and exhaust manifolds. Ajav E. A. and Akingbehin O.A. (2002) have made a study on some of the fuel properties of ethanol blended with diesel fuel. Some properties have been experimentally determined to establish their suitability for use in CI engines. The results showed that both the relative density and viscosity of the blends decreased as the ethanol content in the blends has increased. Based on the findings of their report, blends with 5 &10% ethanol content are found to have acceptable fuel properties for use as supplementary fuels in diesel engines. Naveenkumar et al (2004) have explained in detail the use of ethanol-diesel emulsion as a diesel fuel extender. Ethanol has emerged as one of the viable biofuel. They have made an attempt to use ethanol-diesel blends as a fuel for unmodified diesel engine. Various fuel samples have been prepared and their physico-chemical properties evaluated. Tests have been conducted on a single cylinder, direct injection diesel engine to compare these fuels in terms of performance and exhaust gaseous emissions. Finally, the authors have concluded that thermal efficiency improves by using ethanol with standard diesel. Keith et al (2003) reviewed the existing public data from previous exhaust emissions tested on ethanol (E) diesel fuel. They conducted experiments at different engine loads, engine speeds and on different engine

6 29 designs. The variations in performance under these various conditions were observed and discussed. They observed that the emissions of E diesel relative to diesel fuel varied widely with respect to different engine sizes, engine design, and cetane number and operating conditions. Increasing the cetane number of the E diesel blend resulted in improvements in the emissions. They further reported that, generally, regardless of the cetane number, diesel resulted in increased HC and CO emissions, without any change in NO x emissions and reduction in PM emissions. Agarwal (2007) reviewed the production, characterisation and current status of the research work on ethanol, vegetable oil and bio-diesels. He also reviewed the properties and specifications of ethanol blended with diesel gasoline fuel. He observed that ethanol as an additive to gasoline improved the engine performance and exhaust emissions. He further reported that ethanol-diesel blends up to 20 % (E20) could be used in a constant speed CI engine without any engine modifications. The exhaust gas temperature and lubricating oil temperature were lower for ethanol-diesel blends. The engine could be started normally both in hot and cold conditions. A significant reduction in CO and NO x emission was observed while using ethanol-diesel blends. The E20 blend improved the peak thermal efficiency of the engine by 2.5 % along with a reduction in exhaust emissions. He also conducted experiments with a blend of up to 20 % of methyl ester of rice bran oil with diesel and found a satisfactory performance without any engine modifications. He further reported that the 20 % bio-diesel blend (B20) produced better thermal efficiency and lesser smoke emissions. He concluded that the overall combustion characteristics were quite similar for B20 when compared to those of mineral diesel.

7 30 Pramanik (2003) studied the use of jatropha oil and its diesel fuel blends in a compression ignition engine. Blends of varying proportions of jatropha oil and diesel were prepared, analysed and compared with diesel fuel. He reported that the high viscosity of jatropha oil decreased when it was blended with diesel. He found that 70% to 80% of diesel may be added to jatropha oil to bring the viscosity close to that of diesel fuel, and thus blends containing 20% to 30% of jatropha oil can be used as engine fuel without preheating. He also studied the effect of temperature on the viscosity of jatropha oil. The viscosity of the blends containing 70% and 60% vegetable oil came close to that of diesel in the temperature ranges of 70 C to 75 C and 60 C to 65 C respectively. He also reported that the higher density of blends led to more discharge of fuel for the same displacement of the plunger in the fuel injection pump, thereby increasing the specific fuel consumption. A significant improvement in engine performance was observed for blends compared to that of neat vegetable oil. He further reported that the specific fuel consumption was comparable for the 50:50 J/D blend. Acceptable thermal efficiencies of the engine were obtained with blends containing up to 50% volume of jatropha oil. He concluded from the properties and engine test results, that 40% to 50% of jatropha oil can be substituted for diesel without any engine modification and preheating of the blends. Humke and Barsic (1981) evaluated the performance and emission characteristics of crude soybean oil, a 50% mixture of crude soybean oil and degummed soybean oil, and these data were compared with those of diesel fuel using a naturally aspirated, direct injection diesel engine. They reported that injection nozzle deposits with vegetable oil and vegetable oil blends with diesel fuel caused engine performance to decrease and emissions to increase as a function of test time. They also reported that vegetable oil densities were 10% higher than that of diesel fuel and resulted in a greater mass flow to the

8 31 engine because the fuel injection pump controlled volume delivery. Since vegetable oil viscosities were 8 to 10 times higher than that of diesel fuel, the internal pump leakage was reduced which also contributed to an increased flow. They found that degummed vegetable oil performs better than crude vegetable oil. Robert Fanick and Ian Williamson (2002) have reported on the comparison of emissions and fuel economy characteristics for the emulsified fuel for the heavy duty diesel engine. Also, three emulsified fuels have been prepared with the help of oxygen enriched additives. Results obtained are based on the fuel properties such as cetane number, lubricity, emissions and fuel consumption compared with diesel fuel. Further, continuing result of lubricity, FC and emission have been decreased, when a cetane improver has been implemented for preparing the emulsified fuel. Wang et al (2008) studied the combustion characteristics of a methanol-diesel dual-fuel compression ignition engine. They investigated the combustion characteristics of the engine, with measured cylinder pressures, using a single cylinder, naturally aspirated, four stroke, and direct injection diesel engine, operated on pure diesel and on dual fuel (methanol-diesel). They reported that the static injection timing of pilot diesel was kept constant at 21 BTDC and engine speed at 1600r/min. They introduced methanol until the engine load was higher than 15 percent of the maximum torque, since, methanol has a low cetane number and high latent heat. They found that the ignition delay of the methanol-diesel dual-fuel engine increases with an increase in the methanol mass fraction. Methanol has a faster flame speed; hence, the shorter flame propagation distance. These aspects make the rapid combustion duration shorter. They further reported that the engine smoke showed a sharp decrease with an increase in the methanol mass fraction as methanol contains no heavy hydrocarbons and no carbon- carbon bonds. They

9 32 concluded that with an increase in the methanol mass fraction, both CO and HC increased but smoke and NO X decreased simultaneously under all operating conditions. Irshad Ahmed (2001) has investigated the study of emissions and performance characteristics of ethanol-diesel blends in CI engines. It has been found that the formation of NO X, smoke and other harmful emissions could be significantly reduced by mixing oxygenate additives in to diesel fuel. The overall results have established that the ethanol-diesel blends are compatible with the existing technology, fuel distribution, use and blending infrastructure. The report finally states that fuel performance, long term storage ability, emissions, durability, materials compatibility, environmental biodegradability and other engine characteristics have been established to meet the required emulsified fuel specifications. Murayama et al (1984) investigated the feasibility of rapeseed oil and palm oil for diesel fuel substitution in a naturally aspirated D.I. diesel engine, and also found the means to reduce the carbon deposit buildup in vegetable oil combustion. The engine performance, exhaust gas emissions, and carbon deposits were measured for a number of fuels, namely, rapeseed oil, palm oil, methyl ester of rapeseed oil and blends of these oils with ethanol and diesel fuels at different fuel temperatures. They found that both the vegetable oils generated an acceptable engine performance and exhaust gas emission levels for short-term operation, but they caused carbon deposit buildups and sticking of piston rings after extended operation. They suggested practical solutions (to overcome these problems) such as increasing the fuel temperature to over 200 C, blending 25% by volume of diesel fuel in the vegetable oil, blending 20% by volume of ethanol in the fuel, or converting the vegetable oils into methyl esters. They found that a blend of 25% diesel and

10 33 75% rapeseed oil gave better engine performance, lower emissions, carbon deposit build up and piston ring sticking. They also established empirical equations to estimate the density and viscosity of rapeseed oil, palm oil and their blends at different temperatures. Senthilkumar et al (2001) operated a dual fuel diesel engine using vegetable oils as primary and pilot fuels. They conducted experiments with orange oil as an induction fuel and jatropha as a pilot fuel. They varied the energy share of orange oil up to 35% of the total energy share. They also tried methyl ester of jatropha oil and diesel as pilot fuels for comparison. They reported that dual fuel operation with orange oil induction reduced the smoke level and improved the thermal efficiency with all pilot fuels. The NO X emission is lower with all pilot fuels in the dual fuel mode as compared to that in single fuel operation. They concluded that the use of jatropha oil and methyl ester of jatropha oil as pilot fuels and orange oil as the inducted fuel will improve the performance of the diesel engines. Li et al (2008) analysed the combustion characteristics of a compression ignition engine fueled with diesel-ethanol blends with and without the cetane improver using a single cylinder DI diesel engine. They showed that for the same brake mean effective pressure and engine speed, the maximum cylinder pressure, the ignition delay, premixed combustion duration and the fraction of heat release in premixed combustion phase increased, while the diffusive combustion duration, the fraction of diffusive combustion phase and the total combustion duration decreased with an increase in the ethanol fraction in the blends. The centre of the heat release curve moves close to the top dead centre, and the maximum rate of heat release and maximum rate of pressure rise increased with increase in the ethanol fraction in the blends.

11 34 They reported that the addition of ethanol to diesel fuel decreases the cetane number of the blends, increasing the ignition delay and the amount of combustible mixture available within the ignition delay period, subsequently increasing the amount of fuel burned in the premixed burning phase, which increases the rate of pressure rise, and the combustion noise when operating on diesel ethanol blends by reducing the amount of combustible mixture within the delay period. They revealed that the amount of the premixed combustion heat release for diesel-ethanol blends decreased by adding a cetane number improver to the blends. Armbruster et al (2003) conducted experiments with on-board conversion of alcohols to ethers for fumigation in compression ignition engines. For the use of methanol in compression ignition engines, DME fumigation has been found to be a promising alternative, which gives excellent performance and emission results. However, they found an increase in CO and HC emissions. They evaluated the heat release and ignition delay based on the cylinder pressure data and reported that precombustion creates appropriate conditions for the main fuel (Methanol) to facilitate ignition and enhance the main combustion. They concluded that the use of ethers as ignition improves in alcohol engines gives comparable performance and emissions. Bhattacharya et al (2006) have conducted the experiment on stationary, constant speed compression ignition engine, using an alcohol fuel in diesel emulsions. The performance of the engine has been evaluated in terms of brake power, FC, brake thermal efficiency and emission of NOx. The result shows that the brake thermal efficiency of the engine and the emission part increased have been increase and decreased respectively. Finally they conclude that the performance of the engine with respect to efficiency and

12 35 emissions, emulsion fuels could be used in a CI engine, during periods of lean supply of diesel. Agarwal and Rajamanoharan (2009) investigated the performance and emission characteristics of a compression ignition engine fueled with karanja oil and its diesel blends of 10%, 20%, 50% and 75%. The effect of temperature on the viscosity of karanja and diesel blends was also investigated. They reported that significant improvements were obtained both in the performance and emission characteristics with preheating or without preheating the vegetable oil. Higher brake thermal efficiencies than those of mineral diesel were obtained for all blends except 100% karanja oil. However, it was reported that preheating the oil improved the brake thermal efficiency for all the blends including 100% karanja oil. They concluded that the karanja oil blends with diesel up to 50% with or without preheating, and could replace diesel for running the CI engine for lower emissions and also improve the performance. Abolle et al (2009) proposed empirical modelling to interpolate viscosity to any kind of diesel oil/straight vegetable oil blend. They reported that when viscosity increased the spray angle decreases. This property of straight vegetable oil induces a reduction of the spray angle, and this may cause the fuel droplets trajectory to collide with the combustion chamber walls. This leads to the formation of carbon deposits and/or the engine wall lubricant dilution. They also reported that viscosity can be varied to a great extent when blending diesel oil with vegetable oil. Patterson et al (2006) experimentally studied the performance and emissions of a four cylinder, four stroke DI diesel engine using methyl esters derived from three different vegetable oils, namely rapeseed, soybean and

13 36 waste cooking oils. They conducted experiments at five conditions and at two different speeds. They reported that the engine performance and emission for all the 5% bio-diesel blends were indistinguishable from those of mineral diesel. However, at higher blends, the rapeseed oil fuel exhibited better emission and performance characteristics than those of either the soybean or waste cooking oil fuels. They reported that the soybean oil bio-diesel has the lowest NO X emission and lowest fuel borne oxygen content. They reported that the reason for lowest NO X emissions is the higher viscosity of the fuels leading to poor spray characteristics that reduced combustion efficiency and hence maximum combustion temperature. They reported that for 50% and 100% blends, ignition delays were increased at low loads; with the longest ignition delay being observed for S100 (neat soybean bio-diesel) and the shortest for rape seed oil bio-diesel. They conducted that in an unmodified engine, rapeseed oil gave the best combustion and emission performance. Jose and Desantes (1999) carried out experimental investigation in a single cylinder direct injection (DI) diesel engine fueled with rapeseed oil methyl ester at three different pressures and reported that the droplet size of methyl ester was more than that of diesel due to higher viscosity and resulted in increased combustion duration. Carraretto et al (2004) investigated the potentiality of biodiesel as an alternative fuel in boilers and diesel engines installed in urban buses. Investigation monitored the distance, fuel consumption and emissions (CO 2, CO, HC and NO X ) and also checked the wear and tear, oil and air filter dirtiness and lubricant degradation. The results revealed a slight reduction in the performance, notable increase in specific fuel consumption (SFC), reduced CO and increased NO X emissions.

14 37 Eugene Ecklund et al (1984) demonstrated various methods of using alcohol fuels in diesel engines. They reported the various techniques of using alcohol fuels in diesel engines like solutions, emulsions, fumigation, dual injection, spark ignition, and ignition improvers. They also reported that power output, thermal efficiency, and exhaust emissions can change significantly depending on the techniques employed. The easiest method by which alcohols can be used in diesel engines is in the form of solutions. But this method is limited due to its limited solubility in diesel. The dual-fuel techniques (fumigation and dual injection) are better suited to moderate length shortages and could allow relatively easy switching back to straight diesel fuel. They further reported that the use of spark ignition or ignition improving additives allow total displacement of diesel fuel in situations in which total substitution of diesel fuel is desired. Physical properties like viscosity, cetane rating, and lower heating value were reduced when alcohol was added to decrease in brake thermal efficiency. They observed that Unburned Hydrocarbons (UBHC) and carbon monoxide (CO) increased slightly whereas there was a fluctuation in the trend of NO X emissions and smoke emission with alcohol content in the solution. Lakshmi Narayana Rao et al (2008a) analysed the combustion, performance and emission characteristics of Used Cooking Oil Methyl Ester (UCME) and its blends with diesel in a direct injection diesel engine. They found a minor decrease in thermal efficiency with a significant improvement in the reduction of particulates, carbon monoxide and unburnt hydrocarbons compared to those of diesel. An increase in the oxygen content in the UCME blend resulted in better combustion and increase in the combustion chamber temperature, which leads to an increase in NO X emission. They reported a significant reduction in smoke intensity, especially at higher loads even with 20% UCME. The engine developed the maximum rate of pressure rise and

15 38 maximum heat release rate for diesel, compared to those of 100% UCME and other blends. The ignition delay of UCME and its diesel blends was found to be lesser compared to that of diesel. They mentioned that used cooking oil as feedstock for tranesterification reduced the production cost of bio-diesel. They concluded that UCME satisfies the important fuel properties as per the ASTM specification of bio-diesel and improves the performance and emission characteristics of the engine significantly. Nwafor and Rice (1995) evaluated the performance of Rapeseed Methyl Ester (RME) in an unmodified diesel engine. They compared the effect of using RME in a diesel engine with the baseline test on diesel fuel. It was reported that the maximum power output of the engine running on RME was slightly lower than that running on diesel fuel, due to the low heating values of plant oil. The thermal efficiency of the engine was higher at high load levels when operating on RME. The carbon deposits on the injector were similar to those observed with diesel fuel. They reported lower cylinder peak pressure and longer ignition delay for RME compared to those of diesel fuel. They also reported that the start of fuel injection was the same for RME and diesel, but the injection duration for RME operation was longer due to its higher fuel viscosity and perhaps to compensate for the low heating value of plant fuels. Banapurmath et al (2008) investigated the performance and emission characteristics of a DI compression ignition engine operated on honge, jatropha and sesame oil methyl esters using a single cylinder four stroke DI diesel engine. They reported that poor mixture formation, lower volatility, and higher viscosity lead to lower brake thermal efficiency for Jatropha Methyl Ester (JOME) among the biodiesel tested. The HC, CO and smoke opacity for JOME are higher in comparison with those of other fuels

16 39 due to the heavier molecular structure, higher viscosity and poor atomisation of jatropha oil. They observed that NO X emissions were higher for diesel operation compared to those of biodiesel. The heat release rates of biodiesel were lower during the premixed combustion phase, and led to lower peak temperature. They further reported longer ignition delay and combustion duration for biodiesel compared to those of neat diesel. From the literature survey on usage of low cetane biofuels in diesel engine, it has been found that bio-fuel with diesel fuel can be used in long term operation without affecting engine performance and exhaust emissions. The properties of bio-fuel blends are similar to those of diesel fuel. Bio-fuel can be blended with any proportion and injected as in a conventional injection system. It is evident that many researchers attempted to use different kinds of low cetane biofuels as alternative fuels to diesel engines and spark ignition engines. And it is also reported that the low cetane fuel was used in diesel engine with or without any modifications. There are still only a few literature reporting experimental results on the combined use of low cetane bio-fuel with diesel fuel, while there is certainly need to obtain more such experimental data.

17 BIOFUEL WITH STANDARD DIESEL BLENDS IN DIRECT INJECTION DIESEL ENGINE WITH EXHAUST GAS RECIRCULATION Oxides of nitrogen (NO X ) are formed during combustion when localised temperatures in the combustion chamber exceed the critical temperature which makes molecules of oxygen and nitrogen to combine. Exhaust Gas Recirculation (EGR) system has received attention as a potential solution. Many research work results showed that EGR is one of the most effective methods used in the modern engines to reduce the NO X emissions. These studies are summarised and given in this section. Pradeep and Sharma (2007) reported exhaust gas recirculation is an effective method to reduce the NO X. He conducted experiment in direct injection diesel engine powered by jatropha based bio-diesel. From the research it is found that the NO X emissions were reduced when the engine was operated with 5-25% and the brake thermal efficiency is reduced beyond 15% EGR level. And also, quoted that 15% EGR is the optimum level which results in minimum possible Smoke, CO, HC and reasonable brake thermal efficiency. Hot EGR technique reduces the practical difficulty faced in the cooled EGR system viz. corrosion of gas cooler, cooling capacity at higher loads and extra weight are avoided. Further it is noted that combustion parameters were found comparable with JBD and standard diesel fuel. Abd-Alla (2002) in his work reviewed the potential of exhaust gas recirculation (EGR) to reduce the exhaust emissions, particularly NO X emissions, and to delimit the application range of this technique. A detailed analysis of previous and current results of EGR effects on the emissions and performance of diesel engines, spark ignition engines and duel fuel engines is

18 41 introduced. From the detailed analysis, it was found that adding EGR to the air flow rate to the diesel engine, rather than displacing some of the inlet air, appears to be a more beneficial way of utilising EGR in diesel engines. This way may allow exhaust NO X emissions to be reduced substantially. EGR also reduces the combustion rate, which makes stable combustion more difficult to achieve. At constant burn duration and brake mean effective pressure, the brake specific fuel consumption decreases with increasing EGR. The improvement in fuel consumption with increasing EGR is due to three factors: firstly, reduced pumping work; secondly, reduced heat loss to the cylinder walls, and thirdly, a reduction in the degree of dissociation in the high temperature burned gases. In dual fuel engines, with hot EGR, the thermal efficiencies improved due to increased intake charge temperatures and reburning of the unburned fuel in the recirculated gas. Simultaneously, NO X is reduced to almost zero at high natural gas fractions. Cooled EGR gives lower thermal efficiency than hot EGR but makes possible lower NO X emissions. The use of EGR is therefore, believed to be most effective improving exhaust emissions. Agarwal et al (2006) chosen constant speed, two-cylinder, fourstroke cylinder, direct injection diesel engine generator set of 9 kw rated for his research and used biodiesel extracted from rice bran oil as fuel. From the results, it is noted that biodiesel-fueled engine produced less CO, unburned HC, particulate emissions and higher NO X emissions as compared to mineral diesel. They have also reported that EGR was effective to reduce NO X from diesel engines and could be effectively employed for biodiesel applications. And also reported that 20% biodiesel with 15% EGR is found to be optimum concentration for biodiesel, which improves the thermal efficiency, reduces the exhaust emissions and the BSEC.

19 42 Ladommatos et al (1998) reported that the EGR is one of the most effective techniques to reduce NO X emissions in internal combustion engines. However, the application of EGR also incurs penalties. In the case of diesel engines, they include worsening specific fuel consumption and particulate emissions. From the results it is found that at high loads, EGR aggravates the trade-off between NO X and particulate emissions. The application of EGR can also affect adversely the lubricating oil quality and engine durability. Also, EGR has not been applied practically for heavy duty diesel engines because wear of piston rings and cylinder liner is increased by EGR. It is widely considered that sulphurdioxide in the exhaust gas strongly relates to the wear. The results showed that the sulfur oxide concentration in the oil layer is related strongly to the EGR rate, inversely with engine speed and decreases under light load conditions. It was also found that as the carbon dioxide levels are increased due to EGR, the combustion noise levels also increase, but the effect is more noticeable at certain frequencies. Lazaro et al (2002) analysed dual cooled EGR prototype and tested in four steady state operating conditions in a direct injection diesel engine. The prototype was characterised on test flow and thermal efficiency rigs and also studied on the engine test bed. From the results it is concluded that under steady partial load conditions small reduction in CO and HC emission with a small increase of NO X emission. There were significant reductions of HC and CO emission with slight increases of NO X emission were obtained during engine warm-up tests. This showed a potential to reduce CO and HC emission during the first stages in the emission certification test in Europe. This technique can be used to improve catalyst light-off, temperature particle trap regeneration and other engine functions.

20 43 Miller et al (2007) employed four strokes, single cylinder, water cooled, and naturally aspirated direct injection diesel engine developing 3.73KW at 1500 r.p.m fueled by L.P.G. EGR flow rates were varied in steps of 5%, 10%, 15% and 20%. The test results showed that brake thermal efficiency increased by about 2.5% at part loads for all EGR percentages, but at full load higher EGR percentage affected the performance of the engine. HC and NO concentrations were lowest at full load at 20% EGR. The rate of pressure rise was marginal for all EGR percentages at part loads however the rate of pressure rise reduced significantly at higher loads. Raheman and Phadatare (2004) conducted performance and exhaust emission analysis in a diesel engine supplied with Karanja Methyl Ester (KME) and its blends with diesel from 20% to 80% by volume. They noticed increase in torque, brake power, brake thermal efficiency and reduction in brake specific fuel consumption and CO, NO X emissions and smoke density. They also concluded that blend with 20% and 40% biodiesel could be replaced with diesel. Nidal and Abu-Hamdeh (2003) studied spiral fin exhaust pipe that was designed to analyse the effect of cooled EGR on diesel engine. In this study, emissions such as NO X, CO 2 and CO were analysed. In addition; O 2 concentration in the exhaust was also measured. The two designs adopted in this study were with solid exhaust pipes and hollow fins around them. First model used airflow around the fins to cool the exhaust gases where as second model consisted of hollow fins around the exhaust pipe to allow cooling water to flow in the hollow passage. Different combinations and arrangement of the solid and hollow fins exhaust pipes were analysed. From the results it is

21 44 inferred that decreasing in the EGR temperature results reductions in the NO X, CO 2 emissions and increased CO emission in the exhaust gases. Alain Maiboom et al (2008) studied the influence of cylinder to cylinder variations in EGR distribution on the NO X - PM trade off had been experimentally investigated on an automotive high speed direct injection diesel engine. The test results showed that suppression of unequal EGR distribution results in decreased NO X and PM emissions, especially when running with high EGR rates. Ming Zheng et al (2004) reported that EGR was effective to reduce NO X emission from diesel engines because it lowered the flame temperature and the oxygen concentration of the working fluid in the combustion chamber. However, as NO X emission reduced, particulate matter increased, resulting from the lowered oxygen concentration. When EGR ratio further increased, the engine operation reached zones with higher instabilities, increased carbonaceous emission and even power losses. They also studied oxidation catalyst converter with EGR that eliminated the recycle combustible thus stabilising the cycle s variations. Saleh (2009) investigated the effect of exhaust gas recirculation on exhaust emission and performance in a diesel engine operating with jatropha methyl ester. For all operating conditions, a better trade off between HC, CO and NO X emissions can be attained within a limited EGR rate of 5 15% with little economy penalty. Spring and Onder et al. (2007) addressed the problem of EGR occurring when pressure-wave superchargers were used as boosting devices of IC engines. During accelerations, critical situations arise whenever large

22 45 amounts of exhaust gas were recirculated over the charger from the exhaust to the intake manifolds of the engine. Such recirculation's caused the engine torque to drop sharply and thus severely affected the driveability of the vehicle. A new Pressure Wave Supercharged (PWS) controller system was designed and experimentally verified that prevented the above mentioned problems. The control concept was based on the fact that the EGR rate was linked to the scavenging rate, an indicator for the amount of fresh air leaving through four channels of the PWS. From the above literature review, it is evident that many researchers have investigated the effect of exhaust gas recirculation on diesel engine performance. Hot EGR technique is preferred because it reduces the practical difficulty faced in the cooled EGR system. And also it is inferred that there is better trade off between HC, CO and NO X emissions can be attained with 15% EGR and without reduction in brake thermal efficiency. In research, we use 15% of exhaust gas recirculation to analyse the performance, combustion and emission characteristics of direct injection diesel engine powered with standard diesel fuel, eucalyptus oil with diesel fuel blends and turpentine oil with diesel fuel blends.

23 BIOFUEL WITH STANDARD DIESEL BLENDS OPERATED IN THERMAL BARRIER COATED DI DIESEL ENGINE In the recent researches there are only limited numbers of technical papers available in the area of application of metal matrix composites and ceramic based thermal barrier coating on automobile engine components. Can Hasimoglu et al (2008) used biodiesel produced from sunflower oil in the Low Heat Rejection (LHR) engine and analysed its performance and emission characteristics. In this work Mercedes Benz / OM364A type, four cylinders, turbocharged DI diesel engine. The tests were performed at full load condition for the engine speeds of 1100,1200,1400,1600,1800,2000,2200,2400,2600 and 2800 rpm. Yttria Stabilised Zirconia with a thickness of 0.35 mm over a 0.15mm thickness of NiCrAl bond coat was used to convert the test engine into LHR engine. The results revealed that the specific fuel consumption and the brake thermal efficiency were improved in LHR engine. Hanbey Hazar (2009) conducted experiment on four stroke, single cylinder, direct injection, naturally aspirated, air cooled 6LD 400 Lombardini model diesel engine was used. The cylinder head, exhaust and inlet valves of the engine were coated with MgO-ZrO 2 to a thickness of 0.35mm over a 0.15mm thickness of NiCrAl bond coat by plasma spray method. The fuels used for this test are canola methyl ester with diesel fuel mixed at ratios of 20% and 35% respectively. The engine power was increased by 8.4%, 3.5% and 1.6% for Diesel fuel and 80D: 20C and 65D: 35C respectively. Emission such as CO and Smoke density decreased considerably whereas NOx emission increases by 11.4%,5.4% and 2.6% for Diesel fuel and 80D:20C and 65D:35C respectively.

24 47 Ramu (2009) conducted an experiment on single cylinder direct injection diesel engine where the cylinder head, valves, piston crown were coated with ZrO 2 and Al 2 O 3 with particle sizes ranging from 38.5 to 63 µm and Ni-20Cr-6Al-Y metal powder with particle sizes ranging from 10 to 100 µm were used. The results revealed that the thermal efficiency was increased and NOx emission was reduced by 500 ppm for ZrO 2 and Al 2 O 3 and 800 ppm for Ni-20Cr-6Al-Y.And also results showed that the smoke density was higher for thermal barrier coated engine. Heat release rate and peak cylinder pressure was also reduced. Buyukkaya et al (2004) studied the effect of ceramic coatings on diesel engine performance and exhaust emissions. The cylinder head and valves of an engine were coated with a 0.35 mm thickness of CaZrO 3 over a 0.15 mm thickness of NiCrAl bond coat and pistons were also coated with MgZrO 3 by using atmospheric plasma spray technique. The result showed that specific fuel consumption was lower for the insulated engine when compared to standard engine. Due to better combustion efficiency in the coated engine, particulate emissions were lower (about 48%) than the standard engine. Hejwowski and Weronski (2002) reported the effect of thin thermal barrier coating diesel engine to analyse the performance, temperature, stress distribution and wear analytically evaluated by means of Cosmos/Works FEM code. From the FEM calculation, the optimum coating thickness for the engine components was identified. The components were coated with (i) NiCrAl bond coat 0.15 mm thick, Al 2 O 3 40% TiO mm thick (ii) NiCrAl bond coat 0.15 mm thick, ZrO 2 8% Y 2 O mm thick. They concluded that the optimum coating thickness for ZrO 2 Y 2 O 3 and Al 2 O 3 TiO 2 was slightly below 0.5 mm. Effect of coatings on stress and temperature distributions

25 48 decreased with increasing distance from the free surface. In this work thermal fatigue and wear test were also discussed. Taymaz et al (2005) evaluated experimentally the effect of ceramic coating on diesel engine with different engine speeds and loads. Experiments were conducted with six cylinder direct injection, turbocharged, inter-cooled diesel engine. The combustion chamber surfaces like cylinder head, piston and valves were coated with CaZro 3 and MgZrO 3, by using plasma coating method onto the base of the NiCrAl bond coat. The thickness of coating is 0.35 mm. The result showed that the increase of the combustion temperature caused the effective efficiency to rise from 32% to 34% at medium load and from 37% to 39% at full load and medium engine speeded for ceramic-coated engine while it increases only from 26% to 27% at low load. It was seen, that the values of the effective efficiency are slightly higher for the ceramic-coated engine compared to the standard engine (without coating). Ekrem Buyukkaya and Muhammet Cerit (2008) conducted a test in a six cylinders, indirect injection diesel engine with an intercooler system.al bond coat and pistons were also coated with MgZrO 3 by using atmospheric plasma spray technique. For the original injection timing of the 20 0 before top dead centre, the brake specific fuel consumption value of the LHR engine was approximately 6% lower than the original engine. NOx emissions were also higher. In this investigation to reduce the NOx emission, the two injection timing 18 0 and 16 0 crank angle BTDC was used. The results showed that BSFC and NOx emission were reduced by 2% and 11%, respectively by retarding the injection timing and optimum injection timing was obtained through decreasing by 2 0 BTDC.

26 49 Adnan Parlak (2005) conducted a test in a single cylinder, indirect injection Ricardo E6 MS/128/76 type diesel engine. Supercharging was applied to test engine with an external compressor. Intake pressure and exhaust back pressure were controlled with a regulator valve, thus permitting an intake to exhaust gas pressure ratio to be maintained constant through the tests. The tests were conducted with variable load at various engine speeds and at the static injection timings of 38 0, 36 0, 34 0 and 32 0 CA. Atmospheric plasma spray coating method was used to coat the combustion chamber components. As for plasma gas, a mixture of Ar + 5% H 2 was used. The combustion chamber components (cylinder head, valves and piston) were coated with MgO ZrO 2 layer of 0.35 mm thickness over a NiCrAl bond coat of 0.15 mm thickness. In this study, optimum injection timing was found with crank angle (34 0 CA) retarded btdc. When the LHR engine was operated with the injection timing of the 38 CA, which is the optimum value of the standard engine, it was shown that oxides of nitrogen emission increased about 15%. When the injection timing was retarded to 34 0 CA in the LHR engine, a decrease in the NOx emission (about 40%) and the brake specific fuel consumption (about 6%) compared to that of the standard engine were observed. By retarding the injection timing, an additional 1.5% saving in fuel consumption was obtained. Ekrem Buyukkaya et al (2006) conducted an experimental investigation on a six cylinders, direct injection and turbocharged diesel engine. The pistons were coated with a 350 micron thickness of MgZrO 3 over a 150 micron thickness of NiCrAl bond coat. The cylinder head and valves are coated with CaZrO 3. The result showed almost 65 C increases in the combustion gas temperature in the LHR engine compared to standard engine. The brake specific fuel consumption was lower by 6% in the LHR engine and

27 50 NOx emission levels were found to be higher by about 9% when compared to standard engine. Yhuda Tzabari et al (1990) conducted an experimental investigation on Petter AV1 diesel engine. In this work the piston was covered by silicon nitrite cup with the help of aluminum adaptor connected to the aluminum piston and supported by the specially fitted gasket. The aluminum alloy/silicon nitride joint was formed by integral casting of an aluminum alloy threaded sleeve which was screwed into the aluminum piston. Insulation was created by an air gap and ceramic fiber washer which provides a flexible support to the piston cap attachment. The test was conducted at various loads to analyse the thermal shock and heat transfer characteristics. The temperature of cylinder head, linier and exhaust valve obtained by finite element models were compared with measured temperature. The test results showed that non uniform displacement occurs between the ceramic cup and piston. In order to improve the piston cup attachment to that aluminum piston the characteristic of the gasket has been changed. Katsuyuki Osawa et al (1991) studied the effect of aluminum engine block without iron sleeve was coated with Zirconium and chrome oxide in the cylinder head, piston crown and valves. The investigation was carried out in single cylinder air cooled diesel engine coupled with AC generator. In this work, injection timing was retarded by 2 degrees before TDC. They conclude that 10% improvement in fuel consumption was recorded for thermal barrier coated engine. From the temperature data analysis, 5% decrease in brake fuel consumption for the coated engine. Coating of the cylinder liner only gives the best performance on comparison to coated piston and cylinder.

28 51 Martin R. Myers et al (1991) investigated the mechanical properties of aluminum, Silicon alloy reinforced ceramic fiber metal matrix composite. Tensile and fatigue tests were carried out over a range of temperatures typical of those experienced during engine operation. The development of metal matrix composites (MMCs) which are of low cost can be produced to near net shape, and be used to selectively to reinforce critical areas of components. These composites may have much improved properties in terms of strength, wear resistance and thermal stability, making them very attractive for use in heavy duty diesel engines. They concluded that, ceramic fibers substantially improve the tensile and fatigue characteristics of the current material at temperatures in the range of the maximum engine operating conditions. The thermal fatigue durability of diesel engine piston may be substantially improved by the incorporation of ceramic fibers. Dennis Assanis et al (1991) conducted the detailed study of effect of ceramic coating on diesel engine performance and emission. Tests were carried out at different engine speeds with a standard metal piston and two pistons insulated with 0.5 mm and 1.0 mm thick ceramic coatings. They reported that the thinner (0.5 mm) ceramic coated piston provided 10% higher thermal efficiency than the metal piston and thicker coated piston resulted in 6 % higher thermal efficiency than the conventional engine. It showed 30% to 60% lower CO levels, 35% to 40% lower unburned hydrocarbon levels, and 10% to 30% lower NOx levels and lower smoke levels when compared to baseline engine. They reason for this is more complete combustion in the insulated version. Matthew Winkler et al (1992) reported on thermal barrier coated diesel engine. In this work they used plasma thermal spray method to coat the piston, cylinder head and liner by Zirconium oxide. In this process, metallic