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The distribution of fuel-air mixture inside the engine cylinder strongly influences the combustion process. Planar laser-induced fluorescence (PLIF) is commonly used for fuel distribution measurement, however, it is mostly reported on moderate- to large-sized engines. In the present work, PLIF is applied to measure the fuel distribution inside the cylinder of a small, four-stroke, port-fuel-injection (PFI), spark-ignition engine with displacement volume of 110 cm3. Iso-octane was used as the base fuel, and 3-pentanone (15% by volume) was added as a fluorescent tracer in the base fuel. The effect of equivalence ratio, considering ϕ = 1.2, 1.0, and 0.8, on in-cylinder fuel distribution was studied with low throttle opening of 25% at 1200 rpm. PLIF images were recorded at different crank angle degrees during both intake and compression strokes over a swirl measurement plane located at the TDC position.

In the present work, the possibility of engine knock detection is investigated based on in-cycle speed data, which is readily available to the ECU. Experiments were conducted at 3000 rpm with wide-open throttle condition in a single-cylinder, air-cooled, port-fuel-injection spark-ignition engine at different levels of knocking. It was found that amplitude of speed oscillations increased with the knock intensity for considered window with the size of 100 crank angle degree, starting from the top dead center of compression. The proposed knock indicators based on in-cycle speed oscillations were found to be able to identify the knock-limited spark timings at different operating conditions. Results showed that the amplitude of speed oscillations, derived from in-cycle speed data with resolution of six crank angle degree, could also be used to quantify the knock. The knock frequency based on speed oscillations also showed a sharp increase at the onset of knock.

In the present work, it is aimed at developing an integrated approach for combustor modeling involving rapid prototyping and water tunnel testing to assess the cold flow numerical simulations; the physical model will be subjected to cold flow visualization and parametric studies and CFD analysis to demonstrate its capability for undergoing rigorous cold flow testing. A straight through annular combustors is chosen for the present study because of it has low pressure drop, less weight and used widely in modern day aviation engines. Numerical Analysis has been performed using ANSYS-FLUENT. Three dimensional RANS equations are solved using k-ɛ model for the Reynolds numbers ranging from 0.64 x 105-1.5 x 105 based on the annulus diameter. Post processing the results is done in terms of jet penetration, formation of recirculation zone, effective mixing, flow split and pressure drop for different cases.

Nowadays, due to stringent emission regulations, it is imperative to incorporate modeling efforts with experiments. This paper presents the development of a phenomenological model to investigate the effects of various in-cylinder strategies on combustion and emission characteristics of a common-rail direct-injection (CRDI) diesel engine. Experiments were conducted on a single-cylinder, supercharged engine with displacement volume of 0.55 l at different operating conditions with various combinations of injection pressure, number of injections involving single injection and multiple injections with two injection pulses, and EGR. Data obtained from experiments was also used for model validation. The model incorporated detailed phenomenological aspects of spray growth, air entrainment, droplet evaporation, wall impingement, ignition delay, premixed and mixing-controlled combustion rates, and emissions of nitrogen oxides (NOx) and diesel soot.

Today, GDI engines are becoming very popular because of better fuel economy and low exhaust emissions. The gain in fuel economy in these engines is realized only in the stratified mode of operation. In wall-guided GDI engines, the mixture stratification is realized by properly shaping the combustion chamber. However, the level of mixture stratification varies significantly with engine operating conditions. In this study, an attempt has been made to understand the effect of engine operating parameters viz., compression ratio, engine speed and inlet air pressure on the level of mixture stratification in a four-stroke wall-guided GDI engine using CFD analysis. Three compression ratios of 10.5, 11.5 and 12.5, three engine speeds of 2000, 3000 and 4000 rev/min., and three inlet air pressures of 1, 1.2 and 1.4 bar are considered for the analysis. The CONVERGE software is used to perform the CFD analysis. Simulation is done for one full cycle of the engine.

Gasoline direct injection (GDI) engines are now trending in automobile field because of good fuel economy and low exhaust emissions over their port fuel injection (PFI) counter parts. They operate with a lean stratified mixture in most of conditions. However, their performance is dependent on mixture stratification which in-turn depends on fuel injection pressure, timing and strategy. But, the main challenge to GDI engines is soot and particulate matter (PM) emissions. However, they can be reduced by employing multi-stage fuel injection strategy. Therefore, in the present work, an effort has been made to study the effect of fuel injection parameters on soot emissions of a GDI engine using the CFD analysis. In addition, the study is also extended to evaluate the performance, combustion and other emission characteristics of the engine. First the engine is modelled using the PRO-E software. The geometrical details of the engine are obtained from the literature.

Owing to a high power-to-weight ratio, mini internal combustion engine is used in propelling an unmanned air vehicle. In comparison to the performance characteristics, the investigations on the combustion aspects of mini engines are scanty. This investigation concerns study of the combustion process of a mini engine and its variability. For this purpose, the experimental cylinder pressure histories were obtained on a laboratory set-up of a 7.45 cm3 capacity mini engine. The analyses of experimental data at different throttle settings reveal that there existed a varied range of rich and lean misfiring limits around a reference equivalence ratio that corresponds to the respective maximum indicated mean effective pressure. At the limiting equivalence ratios, cylinder pressure measurements showed a high degree of cycle-to-cycle variations. In some cases, a slow combustion or misfiring event preceded a rapid combustion.

Short-circuiting of the fuel air mixture during scavenging is the main reason for high fuel consumption and hydrocarbon (HC) emissions in two-stroke SI engines. Though direct injection of the fuel after the closure of ports has advantages, it is costly and complex. In this work, in a 2S-SI, single cylinder, automotive engine, LPG (liquefied Petroleum Gas) was injected through the boost port to reduce short-circuiting losses. A fuel injector was located on one of the boost ports and the air alone was fed through the other transfer and boost ports for scavenging. Experiments were done at 25% and 70% throttle openings with different injection timings and optimal spark timing at 3000 rpm. Boost port injection (BPI) of LPG reduced HC emissions at all conditions as compared to LPG-MI (Manifold Injection). Particularly significant reductions were seen at high throttle conditions and rich mixtures. HC reductions with BPI were 19% and 25% as compared to LPG-MI and gasoline-MI respectively.

This experimental study was aimed at improving a two-stroke S.I engine by injecting gasoline with air assistance through the cylinder barrel. Experimentally obtained performance and emission parameters of the engine at 25% and 100% throttle positions were analyzed at 3000 rpm. The timing of air assisted injection was optimized at 25% throttle and 3000 rpm. The performance and emissions of the engine were compared with those obtained with an optimized manifold injection system. In all cases the best spark timing was used. At 25% throttle although the thermal efficiency was increased only slightly, there was a significant reduction in HC emissions to 6.63 g/kW-h with cylinder barrel injection from 10.69 g/kW-h with manifold injection due to reduced short circuiting of the fuel. There was a reduction in NO emissions as well with cylinder barrel injection. Comparisons were made at the point of highest thermal efficiency at 100% throttle also.

The classical trade-off between NOx and soot emissions from conventional diesel engines has been a limiting factor in meeting ever stringent emission norms. The electronic control of fuel injection in diesel engines emerged as an important strategy for their simultaneous reduction. The high pressure multiple-injection in a common rail direct injection system has been promising in this regard. While, the effects of pilot injection or multiple pulses of CRDI injection schedule on simultaneous reduction of NOx and soot have been widely investigated and reported, the investigations concerning three and more injection pulses have been limited. In this paper, the ability of a predictive model, developed by the authors, in providing optimal multiple-injection schedule is demonstrated through parametric investigations. The effects of pilot and post fuel quantity and dwell between the injection pulses on NOx and soot emissions are discussed.

In this work a novel mixture injection system has been developed and tested on a two stroke scooter engine. This system admits finely atomized gasoline directly into the combustion chamber. It employs many components that were individually developed, fabricated, tested and then coupled together. A small compressor driven by the engine sends pressurized air at the correct crank angle through a timing valve. This is connected to a mechanical injector through a high pressure pipe. Fuel is metered into the high pressure pipe using a standard low pressure injector. The developed mixture injection system resulted in considerable improvements in thermal efficiency and reduction in HC emissions over the manifold injection method at all engine outputs. A considerable reduction in short circuiting losses was seen. The highest brake thermal efficiency achieved was 25.5% as against 23% with the manifold injection system.

Experimental investigations were carried out to assess the effect of using diethyl ether to improve performance & emissions of a DI diesel engine running on water-diesel emulsion. The water-diesel ratio was 0.4:1 (by weight) and diethyl ether percentages of 5, 10 & 15 by weight were tried. The optimum quantity of diethyl ether was chosen as 10% based on emissions. It was found that diethyl ether, when added to water-diesel emulsion can significantly lower NOx and smoke levels without adverse effect on brake thermal efficiency. High HC & CO levels which are problems with water-diesel emulsions, can be significantly lowered with the addition of diethyl ether particularly at high outputs. Ignition delay and maximum rate of pressure rise at full load are also reduced. Even at part load the addition of the diethyl ether can improve the performance as compared to neat water-diesel emulsion without any adverse effect on NOx emission.

The pressure gain characteristics of jet pipe servovalve is required as an input to the designer for improving performance of the servovalve. An attempt has been made to design the first stage jet pipe servovalve parameters to get maximum pressure recovery. The static recovery pressure in receiving holes is a function of jet pipe nozzle displacement relative to receiver plate. The recovery pressure depends on web thickness, jet pipe nozzle diameter, receivers hole diameter, nozzle offset and nozzle stand-of distance. A detailed static recovery pressure analysis of a two stage, four-way, closed ports electrohydraulic flow control valve considering the effect of web thickness, nozzle diameter, receiver hole diameter and offset parameters are presented in the paper. Also the effect of supply pressure on recovery pressure is presented.