Effect research of fuel injection and pressurization pulse width on injection characteristics of ultra high pressure common rail system

喷油与增压脉宽对超高压共轨系统喷油特性的影响研究

¹ College of Power Engineering, Naval University of Engineering, Wuhan 430033, China
² Ship Comprehensive Test and Training Base, Navy University of Engineering, Wuhan 430033, China

Received: 6 December 2021

Abstract

Ultra high pressure common rail system can realize adjustable injection rate by controlling the relationship between fuel injection and pressurization timing, and then affect the fuel injection characteristics of diesel engine. In order to ascertain the effect law and its formation mechanism of the fuel injection and pressurization pulse width on the fuel injection characteristics of ultra high pressure common rail system, on the basis of introducing the mathematical model of the system, the simulation model of ultra high pressure common rail system was established, and the accuracy of the model was verified by performance experiment, the effect of fuel injection and pressurization pulse width on the fuel injection characteristics of the system under different common rail pressure were analyzed. The results show that with the increase of fuel injection pulse width, the shape of fuel injection rate curve is similar to saddle shape and the proportion of large fuel injection rate range in the whole injection process increases gradually. At the same time, the fuel injection opening delay remains unchanged, but the fuel injection closing delay increases significantly when the fuel injection pulse width is small (0.6~1 ms), while it remains basically unchanged when the fuel injection pulse width is large (1~1.4 ms). With the increase of pressurization pulse width, the shape of fuel injection rate curve is similar to saddle shape and remains unchanged under the condition of small injection pulse width, while the fuel injection rate curve shape may appear similar to the "inverted saddle-shaped" under the condition of large injection pulse width, this is due to the rapid decrease of pressurization pressure caused by the closing of the solenoid valve control signal in the pressure-amplifier device before the end of fuel injection.

摘要

超高压共轨系统能够通过控制喷油与增压时序之间的关系，实现可调喷油速率喷射，进而影响柴油机喷油特性。为探明喷油与增压脉宽对超高压共轨系统喷油特性的影响规律和成因机理，在介绍系统数学模型的基础上，建立了超高压共轨系统的仿真模型，并利用性能试验验证了模型的准确性，分析了在不同共轨压力下，喷油与增压脉宽对超高压共轨系统喷油特性的影响。结果表明：①随喷油脉宽的增加，喷油速率曲线形态均近似于靴形，且大喷油速率范围占整个喷油过程的比例逐渐增大，同时，喷油开启延迟保持不变，喷油关闭延迟在喷油脉宽较小时(0.6~1 ms)，增加幅度明显，而在喷油脉宽较大时(1~1.4 ms)，基本保持不变。②随着增压脉宽增加，在小喷油脉宽条件下，喷油速率曲线形态近似于靴形，且保持不变；但在大喷油脉宽条件下，喷油速率可能会出现类似于“倒靴形”的曲线形态，这是由于在喷油还未结束时，增压装置电磁阀控制信号的关闭造成增压压力迅速下降。