| With the advantages of small wetted area,low resistance,light weight and high combustion efficiency,the cylindrical combustion chamber has become the main structure of the scramjet combustor in recent years.The cylindrical combustor is often combined with inward turning inlet and cylindrical isolator.However,the special configuration of the inward inlet makes the flow field in the cylindrical isolator present complex flow characteristics,which would affect the performance of the isolator.The author makes study on the characteristics of the isolator that based on asymmetric coming flow condition,which combined with inward turning inlet.Firstly,according to the formation mechanism of asymmetric flow field,the asymmetric flow field simulation method that based on direct connection mode is proposed.Furthermore,the influences of the key design parameters such as cowl line and shock wave configuration are studied.The best asymmetric flow field has less 5% deviation at Ma5 condition,and less than 6.5% deviation at Ma6 condition.According to the best design of asymmetric flow field,the experimental mode is carried out,and the wind tunnel test results show that the numerical results can perfectly coincided with experimental results.Secondly,based on the asymmetric flow field simulation method,the experimental and numerical study on Ma5 and Ma6 conditions for long and short isolators are carried out.The anti-pressure performances and quality of outlet flow field severely reduced.In the shorter isolator,the relationship between shock train length and back pressure is linear,while the ration increases faster and faster in the longer isolator.Compared with symmetric model,the shock-sustaining of the isolator is decreased by 37.3% at Ma5 condition,whose length to diameter ration is 7.6 and under asymmetric coming flow condition,besides,the exit Mach number and total pressure recovery are decreased by 23.2% and12.7%.To the isolator those length to diameter ration is 13,the shock-sustaining,exit Mach number and total pressure recovery are decreased by 25.4%,18.0% and 8.17%,while decreased by 49.4%,12.0%,27.9% for shorter isolator,and 34.1%,37.9%,42.3% for longer isolator at Ma6 condition.Compared with shorter isolator,the shock-sustaining of longer isolator is increased by 27.1% at Ma5 and asymmetric coming flow condition,while 40.0% at Ma6 condition.Under asymmetric flow condition,the spaces between shocks are longer in asymmetric shock train region,besides large energy loss in mixing region.The total pressure recovery efficient is inversely proportioned to back pressure with better linear law.The outlet Mach number and total pressure recovery coefficient are linear with lower back pressure,while the law tends to be gentle when the back pressure is larger.Finally,the applicability of Waltrup formula is analyzed.The influences of asymmetric coming flow on the length on shock train can be divided into two factors: the distance between the shock train and entrance of the isolator,and the coming flow distortion.In the short isolator,the shock train is close to the entrance,and the applicability of Waltrup formula is poor,and more serious at Ma6 condition.In the long isolator,when the shock train is shorter,the applicability of Waltrup formula is better,while poor for longer shock train. |
