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There are only few studies which address specifically to noise of small engines, and still fewer to noise and smoke both. In this paper Noise-Smoke-Fuel economy correlation study for a small DI diesel has been attempted. The effects of load, speed and injection timing on these parameters are discussed. A common basis for study of Noise and Smoke generation in a diesel engine has been presented. A definite correlation between combustion index with noise and smoke is obtained.

A detailed assessment of the various models proposed to simulate the scavenging process in two stroke cycle engines has been made by comparing the charging efficiency and fresh charge fraction in the exhaust gas predicted by the various models. The effect of delivery ratio on the charging efficiency has been studied in detail using different models. It is recommended that a simple two phase model consisting of 50 percent perfect displacement and 50 percent perfect mixing may be used as a satisfactory approximation of the scavenging process. The effect of charge stratification in improving the fuel economy of two-stroke engines has been examined and an analytical preidction of the effect of charge stratification on reduction in fuel loss has been presented.

A detailed soot emission model for Direct Injection diesel engines has been developed. The model can predict both in-cylinder and exhaust soot concentrations from the engines. Accurate predictions of flame temperature, equivalence ratio and engine cylinder pressure are made for the soot model using a two-dimensional, multi-zone, phenomenological spray mixing combustion model. The net soot concentration in diesel exhaust results from the soot formation and oxidation processes in the combustion chamber. Both these processes occur within the turbulent eddy structure of the charge. Soot formation occurs in the large scale eddy structure in two stages - radical nuclei formation and the formation of the soot particulates from these nuclei. In the fuel rich spray elements, soot is considered to form in both the burning zone and the surrounding fluids. The oxidation or combustion rate of nuclei and soot particulates is kinetically controlled and takes place in the fine eddy structure.

A simulation model for crankcase scavenged 2-stroke cycle SI engine has been developed to predict the performance and scavenging characteristics. A suitable coupling of scavenging and combustion processes has been achieved to enable these predictions. Scavenging process has been analysed through a 3-phase, that is, displacement, short circuiting and mixing, model capable of taking any combination of these phases. The flow of fresh charge in the exhaust during mixing period is modeled based on ‘S’ shape concept. The back flow through the ports is also considered. The combustion analysis uses quasi-dimensional eddy entrainment concept that includes the basic turbulent parameters. The results concerning the combination of displacement, short circuiting and mixing phases are analysed to judge the scavenging characteristics of the enginefrom its overall parameters. The predictions of cylinder pressure time history at different speeds, equivalence ratios and compression ratios are made.