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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.

Ignition delay of diesel sprays is a strong function of ambient temperature and pressure. However, the physical delay has not been modelled satisfactorily in the literature. In this paper, phenomenological calculations of the cooling of spray surface have shown that the physical parameters and fuel type influence the temperature of the mixture of air and the vapour produced by the first parcel of the injected fuel throughout its life upto ignition. A unique thin-ring like zone on the spray surface is postulated where the preflame reactions have reached a critical level beyond which uncontrolled reactions take place. The time at which the spray just touches the ring, ignition is predicted. However, due to turbulence, ignition will take place at only a few points in the neighbourhood of the ring. Decrease in hole-size and increase in injection quantity decrease the drop-size. Reduction in size increases the cooling rate and hence increases the ignition delay.