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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.

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.

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.

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.

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.

In this work methanol was port injected while diesel was injected using a common rail system in a single cylinder non-road CI engine. Experiments were conducted with single (SPI) and double (DPI - pilot and main) injection of the directly injected diesel at 75% load and at a constant speed of 1500 rpm. The effects of methanol to diesel energy share (MDES) and injection scheduling on combustion stability, efficiency and emissions were evaluated. Initially, in the SPI mode, the methanol to diesel Energy Share (MDES) was varied, while the injection timing of diesel was always fixed for best brake thermal efficiency (BTE). Increase in the MDES resulted in a reduction in NOx and smoke emissions because of the high latent heat of vaporization of methanol and the oxygen available. Enhanced premixed combustion led to a raise in brake thermal efficiency (BTE). Coefficient of variation of IMEP, peak pressure and BTE were deteriorated which limited the usable MDES to 43%.

Experiments were conducted on a single cylinder, four stroke S.I. engine fuelled with biogas to characterize the nature of cycle by cycle variations (CCV) at different equivalence ratios. A full cycle simulation program using a two zone model with the capability to study the effects of fluctuations in equivalence ratio on hydrocarbon emissions was developed. CCV have been modeled using the Monte Carlo simulation scheme. The scheme has the capability to account for the deterministic and stochastic effects on the inputs. The model was validated using steady state experimental data and then applied to predict UBHC (Un Burned Hydro Carbon) emissions under conditions of low to high CCV. The predictions agreed fairly well with experimental results. The model can be used to determine the influence of adjusting spark ignition timings of cycles based on individual cycle equivalence ratios.

Experiments were conducted to assess the relative effects of swirl (by using a masked intake valve and by providing swirl grooves on the piston crown) and squish on the performance, emission and combustion characteristics of a lean burn engine operating on liquefied petroleum gas (LPG) at a compression ratio of 10.5 under 20% and 100% throttle opening conditions. The swirl produced by the masked intake valve configuration at 100% throttle opening resulted in improved thermal efficiency and reduced HC emission, cyclic variations, ignition delay & combustion duration as compared to swirl groove piston and enhanced squish piston. The lean misfire limit was extended and there was no increase in the NO level at any given power output. At 20% throttle with high squish, under lean mixture conditions, combustion is even better than the masked valve configuration.

Vegetable oils can be directly used in compression ignition engines without any modification. A dual fuel engine was run using vegetable oils as primary and pilot fuels. Small quantities of orange oil were inducted along with air and ignited after compression by a pilot spray of Jatropha oil. The energy share of orange oil was varied till 35% of the total. Methyl ester of Jatropha oil and diesel were also used as pilot fuels for comparison. Dual fuel operation with orange oil induction reduced the smoke level and improved the thermal efficiency with all pilot fuels. However, hydrocarbon and carbon monoxide emissions were higher. Ignition delay was also increased. Methyl ester of Jatropha oil showed inferior performance than diesel. Performance with Jatropha oil was still inferior. On the whole it is concluded that the use of Jatropha oil and methyl ester of Jatropha oil as pilot fuels and orange oil as the inducted fuel will lead to reduced smoke levels and improved thermal efficiency.

Experimental investigations relating to the performance and emission characteristics under idling conditions of a three cylinder passenger car spark ignition engine operating on a conventional carburettor and a developed single point gasoline fuel injection system are described in this paper. The idling performance at different engine speeds was studied by carrying out comprehensive engine testing on a test bed in two phases. In the first phase, experiments were conducted on an engine fitted with a conventional carburettor whilst they were extended to the engine provided with a developed electronic single point fuel injection (SPI) system, whose fuel spray was directed against the direction of air flow. The injection timing of the SPI system was varied from 82 deg. before inlet valve opening (or 98 deg. before top dead center) to 42 deg. after inlet valve opening (or 26 deg. after top dead center).

The ionization current across the spark plug gap is obtained by applying a constant voltage using DC power source across the spark gap after the high-voltage discharge. The methodology involves study and comparison of different knock detection methods (cylinder gas pressure, accelerometer and ion current) through literature survey, development of analytical models (ionization current, chemical equilibrium, kinetic Nitric Oxides) to estimate crank angle resolved cylinder gas pressure from the measured values of ionization current. Model refinements and validations, development of Ignition Coil integrated DC power source and ion current measurement circuit, Transistorized Coil Ignition and microcontroller based knock controller have been carried out. Experiments have been conducted to validate the model with the reference method (cylinder gas pressure).

An electronic system was developed for the control of the injection timing and injected fuel quantity for studies on a passenger car engine. This system can be used to produce maps of these parameters for implementation in an electronic control unit. The complete electronic hardware which included the cam position sensor, pulse shaping, pulse delay and sequencing features was developed and tested. The system could control the injection pulse width for the different cylinders independent of each other. The developed system was used to conduct parametric studies. The results obtained were compared with that obtained from the base carbureted engine. There was a significant improvement in brake thermal efficiency and reduction in HC and CO emissions with the injection system. A retarded injection timing was needed at low loads. The volumetric efficiency of the injection system was much higher than the carbureted version.

The objective of this work is to make a detailed investigation on the effect of using water diesel emulsions in a direct injection diesel engine. A single cylinder diesel engine was tested under variable load conditions at a constant speed of 1500 rpm at different water to diesel ratios of 0.3, 0.4, 0.5 & 0.6:1 by weight. Performance, combustion and emissions parameters were analysed and compared with pure diesel operation. Significant reductions in smoke density, NO concentraion and an improvement in brake thermal efficiency at high loads were achieved. Smoke level dropped from 3.7 BSU to 1.9 BSU and NO level dropped from 752 ppm to 463 ppm with a water to diesel ratio of 0.5:1, near full load. Water to diesel ratios of 0.4 to 0.5:1 were found to the optimal. Ignition delay, peak pressure, maximum rate of pressure rise, peak heat release rate and premixed burn fraction were higher as compared to diesel operation. Water diesel emulsions had an adverse effect on HC and CO emissions.

Valve actuation parameters like lift, opening and closing times affect performance and emissions of an engine. In this work, a new hydraulic variable valve actuation (VVA) concept is explained, simulated and analyzed using MATLAB. The system applies differential hydraulic pressure on two sides of a piston to open the inlet valve. A system of orifices, one of fixed diameter and the other of variable diameter is used to control the differential pressure. Some of the key parameters, which affect the performance of the system, are fluid supply pressure, damping, orifice diameters, displacement of the plunger controlling the orifice and the spring stiffnesses. The variation of parameters like the plunger movement, inlet and exit areas in a certain way was found to reduce the response time as well as increase the lift. It was also observed that the valve lift could be varied from 3.5 mm to 8 mm by just a 1.5 mm movement of the solenoid actuator.

The upcoming Bharat Stage VI (BS VI) emission legislation has put enormous pressure on the future of small diesel engines which are widely used in the Indian market. The present work investigates the emission reduction potential of a common rail direct injection single cylinder diesel engine by adopting a holistic approach of lowering the compression ratio, boosting the intake air and down-speeding the engine. Experimental investigations were conducted across the entire operating map of a mass-production, light-duty diesel engine to examine the benefits of the proposed approach and the results are quantified for the modified Indian drive cycle (MIDC). By reducing the compression ratio from 18:1 to 14:1, the oxides of nitrogen (NOx) and soot emissions are reduced by 40% and 75% respectively. However, a significant penalty in fuel economy, unburned hydrocarbon (HC) and carbon monoxide (CO) emissions are observed with the reduced compression ratio.

In a direct-injection (DI) engine, charge motion and mixture preparation are among the most important factors deciding the performance and emissions. This work was focused on studying the effect of injector positioning on fuel-air mixture preparation and fuel impingement on in-cylinder surfaces during the homogeneous mode of operation in a naturally aspirated, small bore, 0.2 l, light-duty, air-cooled, four-stroke, spark-ignition engine modified to operate under the DI mode. A commercially available, six-hole, solenoid-operated injector was used. Two injector locations were identified based on the availability of the space on the cylinder head. One location yielded the spray-guided (SG) configuration, with one of the spray plumes targeted towards the spark plug. In the second location, the spray plumes were targeted towards the piston top in a wall-guided (WG) configuration so as to minimize the impingement of fuel on the liner.