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Flow variations from one cycle to the next significantly influence the mixture formation and combustion processes in engines. Therefore, it is important to understand the fluid motion and its cycle-to-cycle variations (CCVs) inside the engine cylinder. Researchers have generally investigated the cycle-to-cycle flow variations in moderate- to large-sized engines. In the present work, we have performed the flow measurement and analysis in a small spark-ignition engine. Experiments are conducted in an optically accessible, single-cylinder, port-fuel-injection engine with displacement volume of 110 cm3 at different throttle openings (i.e. 50% and WOT) using particle image velocimetry. Images are captured at different crank angle positions during both intake and compression strokes over a tumble measurement plane, bisecting the intake and exhaust valves and passing through the cylinder axis.

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.

Cycle-to-cycle flow variations significantly influence the combustion variations from one cycle to the next, particularly at low operating loads in small spark-ignition engines. Hence in the present work, cycle-to-cycle flow variations are analyzed at low throttle opening of 25% in a small spark-ignition engine using particle image velocimetry (PIV) technique. Experiments are conducted in an optically accessible single-cylinder, port-fuel-injection engine (volume: 110 cm3) at 1200 rpm engine speed. Images are captured at different crank angle positions during both intake and compression strokes over a tumble measurement plane bisecting the intake and exhaust valves, and processed using cross-correlation method to obtain the instantaneous velocity fields considering 200 image pairs at each crank angle position considered.

Alternate fuels like LPG and CNG are beneficial in terms of operating cost and emissions as well. They also contribute to reduce CO2 emissions. These gas fuels are known for its problems in engines including wear of parts. Cylinder head valve - seat wear is higher in gas engines. This paper discusses the experimental work on reduction of valve -seat wear in 3 wheeler engine. In the development of new higher power version of the gas engine valve-seat interface wear is observed. Effect of this wear on performance, leak and emissions were studied, qualitative measurements of valve temperatures were studied at different conditions with different fuels. Combustion gas and part temperatures are higher in gas engines. Simulation test cycle is developed for the wear test and various solutions to reduce wear at the valve - seat interface were evaluated. Cost effective solution is implemented with minimum changes in engine.

This paper discusses various noise sources of cylinder head assembly and focuses on design options developed to reduce the cylinder head noise in a single cylinder, 110cc scooter engine. Various experimental procedures were used for identification and ranking of different noise sources. In case of air-cooled small engines, temperature effects are dominant and as a consequence certain noises stand out in hot condition causing severe noise discomfort. After identifying the reasons for abnormal cylinder head noise, countermeasure mechanisms for reducing unintended impacts of valve train/ rocker arm in the layout were developed. The side-effects due to introduction of these additional mechanisms are studied using performance metrics. It is essential to limit noise deterioration over time to increase customer satisfaction. Simulation cycles were developed to quantify the cylinder head noise deterioration using accelerated testing procedures.

Heat flux measurements can provide much needed insight into the energy flow inside an IC engine, which is the key to optimizing its performance. This paper focuses on understanding the nature of heat flux curve and how it varies with varying load conditions, engine speed, Air fuel ratio and ignition timing in a single cylinder, 4 stroke, carbureted, air cooled, spark ignition engine for motorcycle application. In-cylinder heat flux was monitored along with wall temperature and cylinder pressure for motored operation as well as fired conditions. The difference between the motoring mode and fired mode was analyzed to separate out the effects of combustion. In general, the magnitude of maximum heat flux was found to increase with engine rpm and load when all other engine parameters remained constant. The heat flux was found to increase when a mixture setting closer to the stoichiometric value was used.

In this work, a new mechanical cam phaser (MCP) system is developed. This MCP system is simple, reliable, and cost-effective, and also offers good control. Phasing of either intake, exhaust or both intake and exhaust cam can be achieved with this system. A prototype of the mechanical cam phaser has been tested on a motored rig to validate its dynamic characteristics. The system was tested onto a small two wheeler engine and this paper describes the newly developed MCP mechanism and its effects on the performance of a small two wheeler engine.

Small gasoline four stroke engines used in motorcycle applications run mostly at part load conditions. Here fuel economy and good drivability are the major requirements. In this work, a single cylinder, four stroke, 2 valve gasoline motorcycle engine in which part load performance needs to be improved was taken for investigation. Various factors affecting part load performance were investigated and it was found that high exhaust gas dilution was the cause of high cycle by cycle variations in this engine. Commercial software was used in order to predict exhaust gas dilution levels. Based on the simulation, a set of parameters that lead to low exhaust gas dilution were arrived at. These were implemented and tested on the engine and part load performance characteristics such as combustion stability, brake specific fuel consumption and torque output were found to be improved.

Three-wheeler is a popular mode of transport in developing nations. Customers demand higher fuel economy from the vehicles to keep the operating costs to a minimum. Competitive environment of automobile market demands for new improved products with minimum development time. Computer simulations are very useful in reducing the development time through virtual prototyping and testing the system on computers rather than making the physical prototypes and testing on road. Particularly, lumped parameter modeling provides reasonably accurate results for predicting vehicle performance characteristics in short span of time. This is very useful when various system level targets have to be achieved and when trade-offs have to be made to obtain optimal results. This paper focuses on the development of a three-wheeler with LPG fuelled engine to achieve target performance using simulation tools.

The cooling system is an important engine subsystem. The air cooling mechanism of the engine is mostly dependent on the fin design of the cylinder head and block. In the present paper an effort is made to study the effect of fin parameters on fin array heat transfer. Two and three dimensional conjugate heat transfer analyses have been performed using commercially available computational fluid dynamics (CFD) codes. For a given heat flux, the fin profile and fin array parameters could be optimized in a better way by numerical simulation methods. CFD could be used to determine optimal values of the fin parameters, upstream of design process. Different trends of these parameters are observed and the values which give optimized fin surface from the thermal point of view at a given heat flux are determined.