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Global development trend in diesel engine is to extract more power from the same engine thereby increasing the brake mean effective pressure (BMEP). With increase in the engine BMEP, maintaining reliability of the pistons and piston ring set becomes challenging as mechanical and thermal loading increases simultaneously. Reliability can be maintained by changing the material to higher grade and/or applying different coatings; however this involves significant cost and development time. It is always preferred to keep the same material and improve the reliability of parts. In this work the BMEP of a heavy duty medium speed diesel engine is increased by 10% (from 22.8 bar BMEP to 25 bar BMEP) without change in the piston or piston ring set material. This is achieved by studying the effect of existing piston bowl shape and then changing the shape to improve the reliability of piston and piston ring set. A systematic 6 step methodology is followed.

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.

Development trend in diesel engines is to downsize and develop more power from same size of engine. This requires additional air flow and hence increased boost pressure ratio (BPR). With increased brake mean effective pressure (BMEP), the altitude capability of engine reduces. This paper presents a novel approach to estimate the altitude capability of engine and calculate deration factor. As the altitude above sea level increases, ambient pressure decreases, air becomes thinner. For same altitude, ambient temperature also varies as per seasonal changes. This results in change (reduction) in ambient air density. This reduction has significant effect on turbocharger (TC), Intercooler and engine performance. Beyond a limiting altitude, engine performance shall be compromised to avoid any damage to engine and its components.

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.