A Study on the Spray Characteristics of an 800kPa CNG Port Injector
Keywords:
Spray characteristics, Spray penetration and cone angle, CNG port injectorAbstract
This paper investigated the spray characteristics of an 800 kPa compress natural gas (CNG) port injector which was developed in the domestic Korea. The CNG port injector with multi-holes, employed in this experiment, was designed to inject CNG in manifold at high pressure of 800 kPa. The spray macroscopic visualization test was carried out via Schlieren photography to study fuel-air mixing process. The fundamental spray characteristics, such as spray penetration, spray cone angle and spray velocity, were evaluated in the constant volume combustion chamber (CVCC) with varying the constant back pressure in CVCC from 0 to 1.8 bar. For the safety reason, nitrogen (N2) and an acetone tracer were utilized as a surrogate gas fuel instead of CNG. The surrogate gas fuel pressures were controlled at 3, 5.5 and 8 bar, respectively. Injection durations were set at 5 ms throughout the experiment. The simulating events of the low engine speed were arranged at 1,000 rpm. The spray images were recorded by using a high-speed camera with a frame rate of 10,000 f/s at 512 x 256 pixels. The spray characteristics were analyzed by using the image processing (Matlab). The results showed the significant difference that higher injection pressure had more effect on the spray shape than the lower injection pressure. When the injection pressure was increased, the longer pray penetration occurred. Moreover, the linear relation between speed and time are dependent on the injection pressure as well.
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