Hydrogen gas has been injected transversely into Mach 1.8 airflow between parallel channel walls from two circular sonic injectors which were mounted flush and placed in tandem along the centre line of the bottom wall...Hydrogen gas has been injected transversely into Mach 1.8 airflow between parallel channel walls from two circular sonic injectors which were mounted flush and placed in tandem along the centre line of the bottom wall plate of a test section. Both cold and hot airnow conditions, i.e. atmospheric and heated to max.1460K total temperature, were tested. In the cold flow experiments, detailed measurements were successful and the tandem injection resulted in a marked difference from the single injection with respect to the pattern of shock waves and the distribution of pressure and hydrogen concentration near the injector region. Upon changing the injection pressure ratio between the two injectors, it has been revealed that a prior injection upstream of the main injection would be beneficial in terms of the total pressure loss in the airflow and the hydrogen concentration near the injector region while maintaining the mixing performance. In general, the flow features showed little difference as the airflow temperature was raised until hydrogen burning was observed, whence the results became inevitably less quantitative. Against the expectation from the cold flow tests, a prior injection of cold hydrogen has resulted in quenching the main injector flame.展开更多
Experimental results from a series of injection tests of pressurized H2, N2 gases into Mach 1.8 airfiows between parallel channel walls through a flush-mounted circular sonic opening have been presented.Schlieren pict...Experimental results from a series of injection tests of pressurized H2, N2 gases into Mach 1.8 airfiows between parallel channel walls through a flush-mounted circular sonic opening have been presented.Schlieren pictures revealed complex interaction flow features including the occurrence of bow/separation shock waves due to the injection as well as the barrel shock/Mach disc structure inside the injected gas stream. The injectant penetration measured by the Mach disc height against the injection pressure showed a good agreement with the correlation curve based upon the "effective back pressure" concept. The reversed flow region beneath the separation shock wave, the injectant wake and its associated flow entraimment were also visualized by the oil paint method. Wall static pressure distributions around the injector were measured in detail, which corresponded very well to the above results of flow visualization.Gas samplings were also undertaken by using the pressure taps to confirm the presence of H2 gas in the separation region ahead of the injector. Traversing of total pressure and H2 gas concentration at the exit of the test channel showed monotonous increase of the loss while its profile was kept very similar with the injection pressure. The area indicating the loss and the presence of H2 gas almost coincided with each other, which remained to be small to indicate very slow gas mixing/diffusion with the main air flow. With the increase of airflow total temperature to 1200 K, a bulk flame was first observed at the exit section. Further increase up to 1460 K observed an ignition flame at the injector. However,the reflection of the bow shock wave was found to be a more likely trigger of the bulk flame ignition within the test section.展开更多
文摘Hydrogen gas has been injected transversely into Mach 1.8 airflow between parallel channel walls from two circular sonic injectors which were mounted flush and placed in tandem along the centre line of the bottom wall plate of a test section. Both cold and hot airnow conditions, i.e. atmospheric and heated to max.1460K total temperature, were tested. In the cold flow experiments, detailed measurements were successful and the tandem injection resulted in a marked difference from the single injection with respect to the pattern of shock waves and the distribution of pressure and hydrogen concentration near the injector region. Upon changing the injection pressure ratio between the two injectors, it has been revealed that a prior injection upstream of the main injection would be beneficial in terms of the total pressure loss in the airflow and the hydrogen concentration near the injector region while maintaining the mixing performance. In general, the flow features showed little difference as the airflow temperature was raised until hydrogen burning was observed, whence the results became inevitably less quantitative. Against the expectation from the cold flow tests, a prior injection of cold hydrogen has resulted in quenching the main injector flame.
文摘Experimental results from a series of injection tests of pressurized H2, N2 gases into Mach 1.8 airfiows between parallel channel walls through a flush-mounted circular sonic opening have been presented.Schlieren pictures revealed complex interaction flow features including the occurrence of bow/separation shock waves due to the injection as well as the barrel shock/Mach disc structure inside the injected gas stream. The injectant penetration measured by the Mach disc height against the injection pressure showed a good agreement with the correlation curve based upon the "effective back pressure" concept. The reversed flow region beneath the separation shock wave, the injectant wake and its associated flow entraimment were also visualized by the oil paint method. Wall static pressure distributions around the injector were measured in detail, which corresponded very well to the above results of flow visualization.Gas samplings were also undertaken by using the pressure taps to confirm the presence of H2 gas in the separation region ahead of the injector. Traversing of total pressure and H2 gas concentration at the exit of the test channel showed monotonous increase of the loss while its profile was kept very similar with the injection pressure. The area indicating the loss and the presence of H2 gas almost coincided with each other, which remained to be small to indicate very slow gas mixing/diffusion with the main air flow. With the increase of airflow total temperature to 1200 K, a bulk flame was first observed at the exit section. Further increase up to 1460 K observed an ignition flame at the injector. However,the reflection of the bow shock wave was found to be a more likely trigger of the bulk flame ignition within the test section.
