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As per pieces of literature, 40 to 60 % of friction losses of Internal combustion engines occur in their piston-piston rings-liner assemblies and, there is a significant supportive role of simulation in improving this assembly. Literature is also available which tells, how changes in pistons affect oil consumption. Thus, piston dynamics is also important for oil consumption. Furthermore, the results from the simulation module of piston movement also serve as a significant input for postprocessing to calculate piston ring dynamics. This research is conducted to understand the piston secondary motion effect on oil consumption, friction, and blow-by. In this work, the results of ring dynamics and oil consumption simulation modules are studied with consideration and non-consideration of piston secondary motion results. The results like minimum oil film thickness, lubricating oil consumption, friction, friction power loss, and blow-by are investigated.

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.

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.

Valve trains are highly burdened powertrain subsystem which has to undergo high fatigue cycles during its service lifespan. Wear enhances valve lash thus depreciating the performance drastically. Analytical advances have helped engineers to predict parameters such as wear, contact stresses, lubrication etc. to uphold the durability of valve train components. Most of the genset and industrial engines running at medium speed use type 5 valve train. In this paper, our study involves about crack induced “wear” due to Hertzian stress on rocker toe and the process followed to resolve the problem for a medium speed diesel engine We experienced the problem of rocker toe crack resulting in toe wear in field and on test bed. Our investigations led us to evaluate the life of a rocker toe by specifically developing a test cycle to reproduce the wear due to induced cracks as well as to assess the durability.

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 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.

A major task ahead of engine manufacturers today is to extract the maximum power output from the engine while improving the reliability and durability, this is even more significant in case of applications such as power generation where engine experiences high loads for a prolonged period of time. Durability of valve train components in such cases greatly affects the overall engine life and service intervals. Majority of power generation engines running at medium speed employ pushrod type valve train. The high valve train inertia along with continuous operation at high loads poses as different set of problems for such engines. A significant amount of wear can occur at various valve train part interfaces which eventually leads to change in valve lash. A large change in valve lash beyond a certain point deteriorates the engine performance and emissions; it also accelerates the wear further.

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.