High pressure common rail system can precisely control the injection time and injection pressure to improve the thermal efficiency of the engine. The injection characteristics of the system can affect the combustion and emission process of the engine. Injection stability is defined as variation characteristics of injection. This could have an unignored influence on combustion and engine output, while few study has been published. The primary objective is to establish evaluation systems and methods for injection stability. Then to study injection stability of the high pressure common rail system. Firstly, several parameters that have an important influence on the emission and combustion are identified. Based on the characteristics data obtained, it is verified that the stability parameters are in accordance with the normal distribution. Then, the five characteristic stability parameters of close speed of injection, cycle injection mass, injection delay, maximum injection rate and open speed of injection were quantitatively analyzed by using range, relative range, kurtosis and variance. It is found that the close speed of injection is greatly depend on injection pressure, the range of close speed varies from 1.8 to 5.1 mg/ms when rail pressure varies from 60 MPa to 160 MPa at 0.6 ms energizing time. The stability of injection mass depends on energizing time, the relative range in short energizing time can be four times than long energizing time. The maximum injection rate has similar characteristics with injection mass, it is also depends on energizing time. The range of maximum injection rate is reduced from the average of 0.6–0.7 mg/ms to 0.3 or even 0.2 mg/ms with the increase of energizing time. The injection delay and open speed of injection seems to be greatly affected by pressure fluctuation, since the observed data present complex rules. Pressure fluctuation in common rail can affect injection stability a lot.

高压共轨系统可以精确控制喷射时间和喷射压力，提高发动机的热效率。系统的喷射特性会影响发动机的燃烧和排放过程。喷射稳定性定义为喷射的变化特性。这可能会对燃烧和发动机输出产生不可忽视的影响，但目前发表的研究很少。主要目标是建立注射稳定性评价体系和方法。然后研究高压共轨系统的喷射稳定性。首先，确定了对排放和燃烧有重要影响的几个参数。根据获得的特征数据，验证了稳定性参数符合正态分布。然后利用极差、相对极差、峰度和方差对注射关闭速度、循环注射质量、注射延迟、最大注射速率和注射开启速度5个特征稳定性参数进行定量分析。研究发现，注射闭合速度很大程度上取决于注射压力，当轨压从60 MPa变化到160 MPa、通电时间为0.6 ms时，闭合速度变化范围为1.8～5.1 mg/ms。注射质量的稳定性取决于通电时间，短通电时间的相对范围可以是长通电时间的四倍。最大注射速率与注射质量具有相似的特性，它也取决于通电时间。随着通电时间的增加，最大注射速率范围从平均0.6~0.7 mg/ms减小到0.3甚至0.2 mg/ms。注射延迟和注射开启速度似乎受压力波动影响很大，因为观察到的数据呈现出复杂的规律。共轨压力波动对喷射稳定性影响很大。