Development of a Very High Pressure Injection System for Diesel Engines

为了减少柴油机排放的氮气颗粒物和氧化物，人们正在努力实现高压喷射系统。这是因为在远高于普通柴油机的压力下喷射，有效地促进了喷射的燃料与周围空气的混合，从而减少了极大地影响碳烟和碳质物质形成的不均一性。然而，将普通喷油系统改装为高压系统时，通常会遇到燃油泄漏和喷油异常等困难。即使在单元喷油器和使用增压活塞的新型喷射系统中，也存在类似的困难。在本研究中，提出了一种新的喷射系统，以消除实现高压喷射的这些困难。基本上，该系统使用液压闸板来增压，依靠进口截面积较大的锥形收敛管和sm…。插座横截面积更大。在入口处的低流体动力阻抗能够强烈地加速驱动柱塞的自由活塞锤，这导致在较高阻抗的另一端产生非常高的液压。这项研究的第一部分是关于收敛管如何在安装喷嘴的出口处提升液压。分析是基于一维波传播的特征线法。结果表明，柱塞效应可以成功地作为喷油系统的增压元件。其次，针对半液压和全液压两种类型的自由活塞式锤片泵，对采用收敛管的高压喷射系统进行了计算机仿真研究，考虑了各种动态效应。这两种泵的特点都是通过电磁控制来启动锤子的运动，从而能够精确地控制喷射定时。这些结果很好地表明了获得超高压注射的能力，并且与传统的注射系统相比也显示出许多优点。较少

To reduce particulates and oxides of nitrogen emitted from diesel engines, much efforts are being made to realize the high pressure injection systems. This is because injection at pressures much higher than those of ordinary diesel engines effectively promotes mixing of the injected fuel and the surrounding air, thereby reducing the heterogeneity which greatly affects the formation of soot and carbonaceous matter. However, it is usual that one confronts difficulties, such as fuel leakage and abnormal injections, when an ordinary injection system is converted to a high-pressure system. Similar difficulties are associated even at novel injection systems such as unit injectors and ones that use a booster piston.In the present study, a new injection system is proposed to remove these difficulties in attaining high-pressure injection. Basically, this system uses the hydraulic ram in boosting pressure, relying on a tapered convergent pipe that has a larger inlet cross-sectional area and a sm … More aller outlet cross-sectional area. A low fluid-dynamic impedance at the inlet affords to strongly accelerate a free-piston hammer by which a plunger is driven, and this leads to a very high hydraulic pressure at the other end of a higher impedance. The first part of this study deals with how the convergent tube boosts the hydraulic pressure at the outlet where the injection nozzle is installed. The analysis is based on the method of characteristics for one-dimensional wave propagation. The results show that the ram effect can successfully be used as a pressure booster in the injection system. Next, the high-pressure injection system that uses a convergent tube is studied based on computer simulation taking into account every dynamic effect, for two types of free-piston hammer pumps operated semi- and full-hydraulically. Both pumps are featured by an electro-magnetic control to initiate the motion of the hammer, to enable precise control of injection timing. The results well suggest a capability of attaining a very high pressure injection and also exhibit many advantages compared to conventional injection systems. Less