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Use of water diesel emulsions in diesel engines reduces simultaneously smoke and NOx emissions. However the ignition delay increases and there is a rise in the HC and CO levels as well. In this work hydrogen peroxide was added to water diesel emulsion and tested in a diesel engine. Initially the engine was run with water diesel emulsion (water to diesel ratio of 0.4:1). The water diesel emulsion with a H2O2/diesel ratio of 0.05 was used. The single cylinder diesel engine was tested at the rated speed of 1500 rpm. Brake thermal efficiency increased with hydrogen peroxide from 32.6% to 33.5% as compared to the plain emulsion at full load. These values are even better than neat diesel operation. CO and HC levels decreased significantly with the addition of H2O2. HC with the neat diesel engine at full load was 50 ppm. It rose to 75 ppm with water diesel emulsion and was controlled to 50 ppm when H2O2 was used. This is due to the strong oxidizing nature of H2O2.

The use of alcohol-gasoline blends enables the favorable features of alcohols to be utilized in spark ignition (SI) engines while avoiding the shortcomings of their application as straight fuels. Eucalyptus and orange oils possess high octane values and are also good potential alternative fuels for SI engines. The high octane value of these fuels can enhance the octane value of the fuel when it is blended with low-octane gasoline. In the present work, 20 percent by volume of orange oil, eucalyptus oil, methanol and ethanol were blended separately with gasoline, and the performance, combustion and exhaust emission characteristics were evaluated at two different compression ratios. The phase separation problems arising from the alcohol-gasoline blends were minimized by adding eucalyptus oil as a co-solvent. Test results indicate that the compression ratio can be raised from 7.4 to 9 without any detrimental effect, due to the higher octane rating of the fuel blends.

The self-ignition temperature of alcohols is so high that abnormally high compression ratios would be required to use them in conventional diesel engines. This paper presents a novel approach of force igniting methanol or ethanol alone in a diesel engine at normal compression ratios. The well established proneness of methanol to pre-ignite in SI engine is made use of in the present method by employing a heated and insulated surface to initiate ignition. A conventional single cylinder diesel engine was modified to work on this principle. The engine operates satisfactorily at the rated speed (1500 RPM) on methanol and ethanol with thermal efficiencies comparable to the normal diesel engine of the same configuration. The operational experience further shows that it is possible to design a self-sustaining hot surface to initiate ignition. The engine also exhibits multi-fuel capability. A new direction for the use of methanol in diesel engines can follow from this technique.

Experiments were conducted on a single cylinder 160cc, four stroke gasoline SI engine. Preliminary experiments were conducted on the base engine to characterize the nature of CBC (cycle by cycle) variations and the influencing parameters. The results have indicated that as the ignition advances, Peak pressure increases and its COV (Coefficient of variation) reduces. IMEP increases up to MBT (Minimum advance for Best Torque) timing and its COV reduces. HC emission and BSFC are minimum at MBT timing. The best AFR (main jet) and spark timing are selected based on low CBC variations and good performance. The engine behavior with this best timing and AFR were taken as the base line data for comparison. The combustion geometry improvement method like dual spark plug and swirl chamber (SC) with multi torch ignition is considered to be more effective for combustion rate enhancement.

A diesel engine was operated with karanja oil, bio-diesel obtained from karanja oil (BDK) and diesel as pilot fuels while LPG was used as primary fuel. LPG supply was varied from zero to the maximum value that the engine could tolerate. The engine output was kept at different constant levels of 25%, 50%, 75% and 100% of full load. The thermal efficiency improved at high loads. Smoke level was reduced drastically at all loads. CO and HC levels were reduced at full load. There was a slight increase in the NO level. Combustion parameters indicated an increase in the ignition delay. Peak pressure and rate of pressure rise were not unfavorably affected. There was an increase in the peak heat release rate with LPG induction. The amount of LPG that could be tolerated with out knock at full load was 49%, 53% and 61% on energy basis with karanja oil, BDK and diesel as pilots.

In the present work, investigations were carried out on a single cylinder, low compression ratio, spark-assisted low heat rejection D.I diesel engine. An extended electrode spark plug was used. Performance and emission tests on the engine were carried out with diesel fuel at two compression ratios, 10.5 and 12.5. In each case the engine was tested as a normal engine as well as a low heat rejection engine. The test results show that the low compression ratio spark assisted diesel engine operates very smoothly due to the low peak pressure and low rate of pressure rise. The low heat rejection spark assisted diesel engine gave an improved performance and reduced emissions compared to the normal baseline diesel engine.

A combustion engine of a given displacement will develop less power when running on hydrogen compared to gasoline or natural gas operation due to less heating value of the fuel air mixture in the combustion chamber. This drop in output exists for external mixing of hydrogen and air prior to intake valve closure. However, external mixing does not require intricate engine modification. Without substantial investment, supercharging is an effective method to increase the output of a hydrogen engine which uses the simple technique of external mixing of hydrogen and air. AVL stationary type research engine was used to investigate the percentage gain in output and thermal efficiency, knock limited combustion air ratios, NO emission and combustion characteristics at different supercharging pressures. The performance of the supercharged hydrogen engine is also compared with that of naturally aspirated hydrogen engine.

The performance of a conventional, carbureted, two-stroke spark-ignition (SI) engine can be improved by providing moderate thermal insulation in the combustion chamber. This will help to improve the vaporization characteristics in particular at part load and medium loads with gasoline fuel and high-latent-heat fuels such as methanol. In the present investigation, the combustion chamber surface was coated with a 0.5-mm thickness of partially stabilized zirconia, and experiments were carried out in a single-cylinder, two-stroke SI engine with gasoline and methanol as fuels. Test results indicate that with gasoline as a fuel, the thin ceramic-coated combustion chamber improves the part load to medium load operation considerably, but it affects the performance at higher speeds and at higher loads to the extent of knock and loss of brake power by about 18%. However, with methanol as a fuel, the performance is better under most of the operating range and free from knock.

In this work, a 7.45 cc capacity glow plug based two-stroke engine for mini aircraft applications was evaluated for its performance, emissions and combustion. It uses a fuel containing 65% methanol, 25% castor oil and 10% nitromethane by volume. Since test rigs are not readily available for such small engines, a reaction type test bed with low friction linear and rolling element bearings was developed and used successfully. The propeller of the engine acted as the load and also the flywheel. Pressure time diagrams were recorded using a small piezoelectric pressure transducer. Tests were conducted at two different throttle positions and at various equivalence ratios. The brake thermal efficiency was generally in the range of 4 to 17.5% depending on the equivalence ratio and throttle position. IMEP was between 2 and 4 bar. It was found that only a part of the castor oil that was supplied participated in the combustion process.

Use of methanol and ethanol in conventional diesel engines is associated with problems on account of the high self ignition temperature of these fuels. The Hot Surface Ignition (HSI) method wherein a part of the injected fuel is made to touch an electrically heated hot surface for ignition, is an effective way of utilizing these fuels in conventional diesel engines. In the present work two types of HSI engines, one using a large ceramic base and the other using a conventional glowplug were developed. These engines were tested with methanol, M.spirit (about 90 % methanol and 10 % ethanol) and diesel. The results of performance, fuel economy emissions and combustion parameters including heat release rates for these fuels with both the types of HSI engines are presented. Diesel engines are commonly used as primemovers in the mass transportation and agricultural sectors because of their high brake thermal efficiency and reliability.

The increasing use of natural gas as a vehicle fuel has generated considerable research activity to characterize the performance of engines utilizing this fuel. A light duty prechamber diesel engine was run under naturally aspirated and turbocharged CNG- Diesel dual fuel mode at four engine speeds 1100, 1400, 1700 and 2000 rpm. The maximum percentage of CNG substitution continues up to the engine knock limited power. The experimental results indicate a fall in brake power under naturally aspirated CNG-Diesel dual fuel mode compared to neat diesel operation. It was due to decrease in volumetric efficiency and slower combustion. Although turbocharged dual fuel operation shows an increase in brake power as well as an improvement in brake specific energy consumption as it provides a better air/fuel mixing and improves the homogeneous natural gas/air charge.

Conventional two-stroke spark-ignition (SI) engines have difficulty meeting the ignition requirements of lean fuel-air mixtures and high compression ratios, due to their breaker-operated, magneto-coil ignition systems. In the present work, a breakerless, high-energy electronic ignition system was developed and tested with and without a platinum-tipped-electrode spark plug. The high-energy ignition system showed an improved lean-burn capability at high compression ratios relative to the conventional ignition system. At a high compression ratio of 9:1 with lean fuel-air mixtures, the maximum percentage improvement in the brake thermal efficiency was about 16.5% at 2.7 kW and 3000 rpm. Cylinder peak pressures were higher, ignition delay was lower, and combustion duration was shorter at both normal and high compression ratios. Combustion stability as measured by the coefficient of variation in peak cylinder pressure was also considerably improved with the high-energy ignition system.

Aldehyde formation and emissions from alcohol fueled engines are studied and presented in this paper. Several chemical kinetic models on the mechanism leading to aldehyde formation have been examined to explore the appropriate control methods to reduce exhaust aldehyde emissions. Control of aldehydes in exhaust emissions by suitable alteration of engine operating parameters, by in cylinder treatment with additives like aniline and water, by external treatment like airpreheating, secondary air injection cooling water rate and exhaust treatment are examined. The concept of surface ignition for alcohol fuels is briefly presented as a long range objective for using alcohols with minimal aldehyde emissions.

In the context of fossil fuel crisis and ever increasing vehicle population, the search for alternative fuel has become necessary. Vegetable oil can be used as an alternative fuel for the diesel engine operation. How ever, engine performance is inferior to diesel due to their higher viscosity. The higher viscosity of vegetable oil causes improper atomization of fuel during injection resulting in incomplete combustion. This leads to smoky exhaust in a diesel engine. While pre-heating of vegetable oil, it was found that viscosity reduces exponentially with temperature. The high temperature of the exhaust, which is otherwise wasted, can be used to preheat the vegetable oil. For this purpose a heat exchanger has to be designed. It was observed that the rubber seed oil (RSO) requires a heating temperature of 155°C to bring down its viscosity to that of diesel.

As alternate fuels, ethyl and methyl alcohols stand out because of the feasibility of producing them in bulk from plentifully available raw materials. In the present work, ethanol is used as the only fuel, in the standard and Low Heat Rejection(LHR) diesel engines by adopting three different methods. In the first method, ethanol as the sole fuel was used in the LHR engine with normal metal glowplug and in the second method spark plug assistance was used to initiate combustion. In the third method, ethanol was used as the sole fuel in a LHR engine and a ceramic glow plug was used to initiate combustion. The engine was tested for performance and emissions for the above three methods of 100% ethanol operation in both the standard and LHR diesel engine and the results are compared. The spark plug assisted ethanol operation in the LHR engine gave the highest brake thermal efficiency and the lowest emissions.

Use of vegetable oils in diesel engines results in increased smoke and reduced brake thermal efficiency. Dual fuel engines can use a wide range of fuels and yet operate with low smoke emissions and high thermal efficiency. In this work, a single cylinder diesel engine was converted to use vegetable oil (Jatropha oil) as the pilot fuel and methanol as the inducted primary fuel. Tests were conducted at 1500 rev/min and full load. Different quantities of methanol and Jatropha oil were used. Results of experiments with diesel as the pilot fuel and methanol as the primary fuel were used for comparison. Brake thermal efficiency increased in the dual fuel mode when both Jatropha oil and diesel were used as pilot fuels. The maximum brake thermal efficiency was 30.6% with Jatropha oil and 32.8% with diesel. Smoke was drastically reduced from 4.4 BSU with pure Jatropha oil operation to 1.6 BSU in the dual fuel mode.

As alternate fuels, ethyl and methyl alcohols stand out because of the feasibility of producing them in bulk from plentifully available raw materials. In the present work, methanol is used as the only fuel, in a Low Heat Rejection(LHR) engine by adapting three different methods. In the first method, methanol as the sole fuel was used in the LHR engine with a ceramic glowplug and in the second spark plug assistance was used to initiate combustion of the injected methanol. In the third method, methanol was used as the sole fuel in a LHR engine by a new method in which part of the methanol fuel was inducted through a heated inlet manifold using a carburetor and another part of methanol (with 1% castor oil for lubrication) was injected through the normal injector. With inducted methanol air charge temperature at 70 C and above the engine operated smoothly.

In a dual fuel engine a primary fuel that is generally a gas is mixed with air, compressed and ignited by a small pilot- spray of diesel as in a diesel engine. Dual fuel engines generally suffer from the problem of lower brake power and lower peak engine cylinder pressure due to lower volumetric efficiency, although an improvement in brake specific energy consumption is observed compared to pure diesel mode. Results indicate that with an increase in percentage of CNG substitution the brake power decreases. The exhaust gas temperature and peak cylinder pressure also decrease. The rate of pressure rise is higher at lower engine speeds (1100, 1400 rev/min), although at 1700 and 2000 rev/min it is lower. The delay period throughout the engine speed shows an increasing trend. The coefficient of variation is also higher throughout the engine speeds and shows an increasing trend. The brake specific energy consumption is lower at 1100, 1400 and 1700 rev/min and at 2000 rev/min it is higher.

A single cylinder, direct injection diesel engine was run on water diesel emulsion at a constant speed of 1500 rpm under variable load conditions. Water to diesel ratio of 0.4 on the mass basis was used. Tests indicated a considerable reduction in smoke and NO levels. This was accompanied by an increase in brake thermal efficiency at high outputs. HC & CO levels, ignition delay and rate of pressure rise went up. The heat release rate in the premixed burn period was higher. When the oxygen concentration in the intake air was enhanced in steps up to 25% along with the use of water diesel emulsion, the brake thermal efficiency was improved and there was a further reduction in the smoke level. HC and CO levels also dropped. NO emission went up due to increased temperature and oxygen availability. An oxygen concentration of 24% by volume was optimal as the NO levels were near about base diesel values.

Experiments were conducted on a single cylinder, natural gas fuelled spark ignition engine. Air fuel ratio was varied from about stoichiometric to the lean limit at two different throttle positions with optimum spark timing. Subsequently the engine was tested at constant throttle and equivalence ratio with variable spark timing. COV (coefficient of variation) of IMEP (indicated mean effective pressure) and peak pressure increase with a reduction in equivalence ratio. When the engine starts to misfire there is a drastic increase in the COV of IMEP. Spark timing has a smaller effect on COV of IMEP than on COV of peak pressure. When the spark timing is advanced, COV of peak pressure attains a minimum value just before knock sets in. Prior cycle effects were seen when there was misfire. Spark timing had little influence on the frequency distribution of IMEPs of cycles, which was generally symmetrical about the mean.