590 / 2019-01-19 20:11:52

Study on Diesel Spray Effective Injection Velocity under Varying Injection Rate

diesel spray characteristics; varying injection rate; one dimensional discrete spray model; entrainment wave

全体主题 > 数值模拟、建模与CFD

To investigate the diesel spray propagation under varying injection rate, a one-dimensional discrete spray model was modified to calculate effective injection velocity under varying injection conditions in this paper. The modified one-dimensional discrete spray model was validated by the measured spray penetrations in the experiment. Then the analysis of spray propagation with vary injection rate profiles was performed using this modified model. The calculated typical varying injection conditions mainly contain triangle shape, trapezoid shape and step shape. The changing trend between the effective injection velocity at the spray tip and injection velocity at the nozzle was obtained and then the spray development process under varying injection rate was summarized. The results revealed that the effective injection velocity, which is represented by the ratio of the momentum flux and fuel mass flow rate integrated over the tip cross-sectional area of the diesel spray was affected by instantaneous injection velocity. The effective injection velocity increases with the injection velocity increased during ramping-up process after a response time. Then the effective injection velocity becomes constant even during ramping-down injection process and after end-of-injection. The larger injection velocity peak and the larger injection velocity rising slope causes the larger final effective injection velocity.