Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model

Abstract

Common rail systems have been widely used in diesel engines due to the stricter emission regulations. The advances in injector technology and ultrahigh injection pressure greatly promote the development of multiple-injection strategy, leading to the shorter injection duration and more variable injection rate shape, which makes the mixing process more significant for the formation of pollutant emission. In order to study the mixing process of diesel sprays under variable injection rate shapes and find the optimized injection strategy, a one-dimensional spray model was modified in this paper. The model was validated by the measured spray penetrations based on shadowgraphy experiments with the varying injection rate. The simulations were performed with five injection rate shapes, triangle, ramping-up, ramping-down, rectangle and trapezoid. Their spray penetrations, entrainment rates and equivalence ratios along spray axial distance are compared. The potentials of multiple-injection and gas-jet after end-of-injection (EOI) to improve mixing process and emission reduction are discussed finally. The results indicated that ramping-up injection rate obtains the highest entrainment rate after EOI, and it needs 1.5 times of injection duration for the entrainment wave to arrive at the spray tip. For the other four injection rates, the sprays can be treated as a steady-like state, needing twice of injection duration from EOI to the time the entrainment wave reaches the spray tip. The multiple-injection with proper injection rate shape enhanced the entrainment rate, and the gas-jet after EOI affected the mixture distribution and entrainment rate in spray tail under ramping-down injection rate.

Experimental and Numerical Model Investigations of Oxygen-Enriched Characteristics in Air-Conditioned Rooms

“…The simulation results were compared with recently developed jet impingement flow formulas at the collisionless flow limits. Intarat Naruemon et al [37] employed an improved one-dimensional diesel spray model to analyze the potential of varying injection rate shapes to lower the pollutant emissions of diesel engines and find the optimized injection strategy.…”

Investigation of a method for online measurement of injection rate for a high-pressure common rail diesel engine injector under multiple-injection strategies

“…Besides, the strong fuel pressure fluctuation will cause the actual injection mass to deviate from the calibrated map. Therefore, the traditional open-loop control strategy could not realize the accurate control of the fuel injection process [17][18][19][20][21]. Hence, in the MIS, the precise control of the injection process is a bottleneck problem that needs to be solved.…”