| Abstract: | A high-pressure natural gas direct injection engine can achieve lean combustion and diffusion combustion of natural gas, which can reduce the emission level and improve power performance. However, the transient gas injection rate of the injector directly affects the combustion rate. In order to optimize engine performance, it is essential to focus on the technology used to measure the transient injection rate. Therefore, in this study, a method is developed to measure the transient flow rate of a high-pressure natural gas pulse injector. First, experiments were conducted to locate the optimum position for sensor installation, thereby ensuring the quality of the signal. Subsequently, a mass flow meter and schlieren imaging method was used to verify the injection mass and injection start/end timing. Finally, the common working conditions of a certain type of injector are measured. Results indicated that the test error of the cycle injection mass and injection start/end timing did not exceed 4% and 2.1%, respectively. As the injector energizing time increased, the injection rate curve changed from triangle to trapezoid. As the injection pressure increased, the injection start delay time decreased and end delay time increased. Measurement of the main and post injection strategy indicates that the main injection has a significant impact on the injection mass and injection rate curve for post injection. When the interval between the two injections is short, the injection rate curves merge. This increases the injection duration. The total injection mass of the main injection and post injection mass is found to be significantly higher than the sum of the two independent injections. |
