Experimental Study on Injection Stability of Common Rail Injector Based on Spray Momentum Method
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摘要:
为研究共轨喷油器各喷孔喷油规律，根据动量法研发了多孔喷油器喷油规律测量装置；在不同的负荷工况下，使用研发的装置测量喷油器各喷孔的喷油量差异性，并与商业单次喷射仪EMI 2的测量结果进行对比；在不同的喷油压力下，针对单一喷孔进行喷孔喷油稳定性研究. 研究结果表明：在低喷油压力下，喷油量波动率随着喷油脉宽的增加而降低，整体上喷油量波动率为10%～20%，此时针阀无法完全打开，针阀-针阀座之间燃油的不稳定流动会造成较大的喷油量波动；在高喷油压力下，针阀更容易达到最大升程，喷孔参数间的不一致性是导致喷孔喷油量波动的关键因素，在0.5～2.0 ms的喷油脉宽范围内，喷油量波动率处于5%之内，远小于相同条件低喷油压力下的喷孔喷油量波动率，针阀无法达到最大升程是导致共轨喷油器喷油不稳定性的主要原因.
Abstract:In order to study the injection law of each nozzle hole of the common rail injector, an injection pattern measuring device for multi-hole injectors was developed based on the momentum method. Under different load conditions, the developed device was used to measure the injection rate of each nozzle hole of the injector, and the difference was compared with the measurement results of the commercial single injection instrument EMI 2. Under different injection pressures, the injection stability of the single injection hole was studied. The research findings indicate that at low injection pressure, the fluctuation rate of the injection decreases with increasing injection pulse width, with an overall fluctuation rate of 10%–20%. At this point, the needle valve cannot fully open, leading to significant fluctuations in the injection due to unstable fuel flow between the needle valve and its seat. At high injection pressure, the needle valve is more likely to reach maximum lift, and thus the inconsistency in nozzle hole parameters becomes the key factor causing fluctuations in the nozzle hole injection. Within the range of injection pulse width of 0.5–2.0 ms, the fluctuation rate of the injection is within 5%, much lower than the fluctuation rate of nozzle hole injection under low injection pressure conditions. This indicates that the inability of the needle valve to reach maximum lift is the primary cause of injection instability in common rail injectors.
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图 5 研发的测量装置和EFS喷射仪测量结果对比
Figure 5. Comparison of measurement results between developed measuring device and EFS injector
图 7 各喷孔喷油速率实验结果对比
Figure 7. Comparison of experimental results of injection rate of each nozzle hole
图 8 在低喷油压力下喷油速率随喷油脉宽的变化
Figure 8. Variation of injection rate with injection pulse width under low injection pressure
图 9 低喷油压力下喷油量波动率随喷油脉宽的变化
Figure 9. Variation of fluctuation rate of injection with injection pulse width under low injection pressure
图 10 高喷油压力下喷油速率随喷油脉宽的变化
Figure 10. Variation of injection rate with injection pulse width under high injection pressure
图 11 在高喷油压力下喷油速率随喷油脉宽的变化
Figure 11. Variation of injection rate with injection pulse width under high injection pressure
表 1 力传感器主要性能指标
Table 1. Main performance indicators of force sensor
指标 数值 量程/N 0～20 输出精度/% 0.05 响应频率/kHz 10 工作温度/℃ −20～80 
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