Flow Characteristics Study Of Isolator At Complicated Incoming Flow Conditions

The scramjet isolators will be interfered with incident shock waves and corner expansion waves in the actual work situation. While, most of the numerical simulation and experimental study on the isolator were under the symmetric or asymmetric coming flow conditions. The difference will produce a great impact on the flow characteristics. The author makes exploratory study on flow characteristics of isolator at complicated incoming flow conditions.First, analyzing the flow characteristics of the isolator at complicated incoming conditions and the isolator at asymmetric incoming conditions. The research shows: Compared with the asymmetric model,the total pressure recovery coefficient and shock-sustaining of the isolator at complicated incoming conditions decreased by 5.23%,14.52.In addition, Asymmetric flow Waltrup formula can predict the shock train length in the asymmetric flow isolator well, while for the isolator at complicated incoming conditions, most calculated data points were at the right side of the Waltrup curve. The applicability was poor.Secondly, using the method of numerical simulation to study the flow characteristics and characteristic parameter, impacted by shock strength of incident shock waves, the lip length. The research shows:the shock train length decreased with the increase of shock strength. At Ma4 condition, the change law is close to linear. While at Ma6 condition, when the back flow pressure is low, its change law also tend to be linear, but when the back flow pressure were high enough, the change law was closer to the quadratic curve. The shock-sustaining capability were greatly influenced by the strength of the incident shock waves. As the strength of the shock waves increased, the shock-sustaining’s largest increasing was almost close to 13.3%, 12.5%. At Ma4, Ma6 conditions. When the shock strength of incident shock waves remained same, the lip length increased the shock-sustaining capability of the isolator firstly increased and then reduced. There was a best lip length making the shock-sustaining capability of the isolator highest.Finally, studying the flow characteristics and characteristic parameter, impacted by internal contraction ratio. The essence of this impact is the impact of shock strength of incident shock waves and the lip length. The research shows: when the internal contraction ratio remained same. The shock strength of incident shock waves increased meanwhile the lip length increased. The shock-sustaining capability and the total pressure recovery coefficient of the isolator firstly increased and then reduced. There were best shock strength of incident shock waves and lip length to make isolator performance well. For the isolator at complicated incoming conditions with different internal contraction ratio 1.887, 2.041, 2.222, 2.439, the shock-sustaining’s largest increasing was almost close to 18.96%, 16.95%, 20.69%, 21.43%.