Drive Control Experimental Studies on the Injection Characteristics of a Self-Pressurized Injector

Abstract

As a miniaturized direct-injection (DI) solution, a self-pressurized injector is of great significance for small aviation piston engines, such as the spark-ignited two-stroke heavy-fuel engines. Accurate control of the timing and amount of injections is an important application prerequisite. In this paper, a high-speed camera is employed to study the spray characteristics, injection delay and fuel injection duration under three drive modes in a constant-volume bomb environment. The results show that the 8-A constantcurrent drive mode ensures the minimum injection dead zone and linearity of the flow characteristic curve, and the spray characteristics are close to those under a peak current of 10 A and holding current of the 8-A drive mode, which indicates that the drive circuit can be simplified. Ambient pressure increase leads to an increased injection delay and shortened injection duration. Therefore, it is recommended to apply the 10-A constant-current drive mode to reduce the impact of the ambient pressure. The double-injection characteristics of the self-pressurized injector are also studied, and the results demonstrate that when the interval time is reduced to 2 ms, the spray characteristics of the secondary injection are affected, and when the interval time is reduced to 0.2 ms, the spray characteristics of the primary injection are also affected. To ensure consistency of the spray characteristics, the minimum spray interval should be longer than 3 ms. INDEX TERMS aviation aircraft, direct injection, spray characteristics, piston engine, self-pressurized injector.