Ignition Delay in a Diesel Engine
| Autor: | Yogesh V. Aghav, P. A. Lakshminarayanan |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | Mechanical Engineering Series ISBN: 9789811667411 Mechanical Engineering Series ISBN: 9789048138845 |
| Popis: | The ignition delay in a diesel engine is defined as the time interval between the start of injection and the start of combustion. This delay period consists of (a) physical delay, wherein atomisation, vaporization and mixing of air fuel occur and (b) of chemical delay attributed to pre-combustion reactions. Physical and chemical delays occur simultaneously. To reduce NOx, the method adapted in modern engines is to reduce the ignition delay. For predicting heat release in modern engines, therefore, the estimation of ignition delay is no more important. However, the ceiling on NOx is dipping to such a low level that accurate prediction of ignition delay has become important even if it is small. 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 chapter, 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 up to 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, the ignition is predicted. However, due to turbulence, ignition will take place at only a few points in the neighbourhood of the ring. Detailed consideration of droplet formation, evaporation fuel and preflame reaction has enabled prediction of delay period and location of the ignition accurately within the experimental errors and errors in the input to the calculations. |
| Databáze: | OpenAIRE |
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