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An innovative Diffusive Air Jet (DAJ) Combustion Chamber concept has been introduced in the present work. The DAJ Combustion Chamber design is based on the study of rate of heat release (ROHR) curve and its correlation with emission generation. The objective is to lower the trade-off between NOx and soot without sacrificing fuel economy of Direct Injection (DI) diesel engine. DAJ Combustion Chamber modifies ROHR curve to the desired one so that it lowers engine out emissions. To study its effect, a large bore, six cylinder engine with mechanical fuel injection system has been used. Three dimensional simulation software is used for the model calibration of basic reentrant cavity. Local emissions and ROHR curve have been studied using reentrant cavity shape. It has been modified to DAJ Combustion Chamber using Air Jet Chambers (AJCs). AJCs are positioned in the three dimensional model in such a way that they affect local in-cylinder emissions.

Indian emission norms for stationary Gensets are upgraded from CPCB I to CPCB II. These new emission norms call for a significant change in emission limits. CPCB II emission norms call for 62% reduction in NOx+HC and 33% reduction in particulates for engines above 75 kW up to 800 kW power range compared to existing CPCB I norms. CPCB II norms are more stringent as compared to European Stage IIIA and CEV BS III. To meet equivalent emission norms in US and Europe most of the engine manufacturers have used Common Rail Direct Injection (CRDI) or electronic unit injection as the fuel injection technology. This paper describes mechanical fuel injection solution for meeting CPCB II emission norms on engines between 93 kW up to 552 kW with acceptable fuel consumption values. The paper presents simulation and experimentation work carried out to achieve the norms for the said power ratings.

To meet stringent emission norms with internal engine measures, design of piston cavity geometry perform a defining role in air motion, fuel air mixing, combustion and emission formation. A study is performed with the objective to have a better tradeoff between NOx, PM and fuel consumption for a Medium duty, constant speed diesel engine operated with Mechanical fuel injection system. Through simulations in 3D CFD tool the effect of piston cavity geometry on performance and emission of diesel engine is investigated and then validated with actual experimentation. In this exercise efforts are made to reduce emissions in a direct injection diesel engine by changing the piston cavity geometry. The piston cavity geometry and dimensions like torus radius, pip region, cavity lip area, and impingement area have an effect on emission formation. The target was to deliberately split the fuel spray and have a better utilization of available air.

In Direct Injection (DI) diesel engines, combustion gets affected by change in in-cylinder air motion and Fuel injection system characteristics. Computational Fluid Dynamics (CFD) based models give detailed insight into the combustion phenomena. The present work investigates the effect of different combustion chamber geometries and fuel injection system parameters on engine emissions and performance aiming to improve trade-off between NOx and smoke. AVL FIRE CFD software is used in this work. Research engine having 9 liter capacity of heavy duty application has been selected for the study. Seven hole injector is used with mechanical fuel injection system having 1000 bar maximum pressure capability. Inputs required to model complex combustion process in the AVL FIRE are derived from one dimensional engine simulation software AVL BOOST.

In order to meet emission norms, modern day diesel engines rely on methods of in cylinder emission reduction and expensive exhaust after treatment devices. Engine manufacturers across the world are finding it hard to maintain balance between customers' demand for better fuel consumption and obeying the stringent legislative emission regulations. Optimum combination of variables such as piston bowl shape, compression ratio, fuel injection and turbo charging systems precisely matched with engine, Exhaust Gas Re-circulation (EGR) rate etc can result in refined combustion leading to better engine out emissions as well as fuel efficiency. Optimization of piston bowl geometry and EGR rate would require a lot of experiments, which involves cost and time. If the numbers of variants of piston bowl shapes or EGR rates are more, so would be the expensive and require more testing time.