Analysis of Diesel Sprays under Varying Injection Conditions

Abstract

Diesel engines are most widely used all over the world because of their efficiency, reliability and adaptability. In heavy duty engines we are more interested in the Torque produced rather than the speed of an engine, such engines that are being used in the Industries have low efficiency and high soot emissions due to inefficient combustion unlike high speed diesel engines that have wide commercial use. Fuel spray atomization is the key process that defines combustion efficiency, which further affects the Fuel Economy and Soot emissions. This research is focused on modelling Spray characteristics under various injection conditions and its effects on child droplet formation and spray characteristics under Direct Injection diesel engine conditions. The computational fluid dynamics (CFD) tools available in Ansys in which basic conservation equations of mass, momentum, energy and Species Transport equations are used. Fluid breakup is modelled using KH and KHRT model while the Collusion among the droplets is modelled using O’Rourke collusion model. Turbulence is incorporated using realizable  model. Fuel and air interaction in an Engine Cylinder is studied using Langrangian –Eularian Hybrid approach. Spray characteristics like Penetration length, Souter mean diameter (SMD), Average mean diameter, Axial Velocity, Cone angle are studied at various Injection conditions. The results revealed that greater penetration Length, high jet velocity and smaller drop diameters are observed at higher Injection pressures. ,Ambient pressure do no affects spray behavior at the early stages of spray but at later stage increasing the ambient pressure decrease penetration Length ,drop diameter and cone angle .Increasing the injection duration and mass flow rate causes the fuel to penetrate further in to the chamber and also increases the drop diameters.