An Investigation On Cold Flow Characteristics Of An Integrated Afterburner

With the increasing demands of engine performance,the military engines of new generation,are required not only to have specific thrust and high flying Mach number,but also to have the superiorities of low fuel consumption and long cruising endurance.However,the conventional turbofan engine and turbojet engine equipped with afterburner are not able to satisfy both requirements.Meanwhile,because of the weight,the loss of flow resistance and some other disadvantages,the traditional design of afterburner would not accommodate to equip the advanced fighters.In this thesis,the integrated afterburner under variable cycle mode was chosen as the study object,and the characteristics of cold flow field of the integrated afterburner would be researched.Firstly,according to the working structural characteristics of variable cycle engine as turbojet mode and turbofan mode,numerical study of the cold flow field in the integrated afterburner under both single and double culvert modes was carried out,and the influence of different structural parameters on the flow field characteristics was analyzed.The results show: under the single culvert mode,the velocity on both sides of the long supporting plate/ stabilizer is higher than that of the short one,and the value of the velocities at the recirculation zones after the stabilizers were similar for both supporting plates;within a certain range,the larger the circumferential inclination of the stabilizer,the smaller the low velocity zone behind the stabilizer;with stabilizer radial inclination of 70 degree,the flow field has the best performance;the blade profiles of supporting plate did not have apparent influence on the rearflow field of stabilizer,but the configuration with C7 blade profile had the minimum total pressure loss;with the increase of separation blade height,the total pressure recovery coefficient at the afterburner outlet reduced,the rear recirculation area of stabilizer became small and the flow field in the concave cavity became unstable.Under the double culvert mode,compared with the single culvert mode,the total pressure loss and high velocity area were mainly concentrated at the area behind the rear culvert ejector,the velocity had a large change and the flow field was unstable in front and behind the rear culvert ejector;with the increase of the plate length of the rear culvert ejector,the total pressure recovery coefficient at the afterburner outlet decreased,the backflow area behind the stabilizer changed in location and kept nearly the same in value;with the increase of the installation distance of the rear culvert ejector to the afterburner inlet,the total pressure recovery coefficient at the afterburner outlet increased,the recirculation area became larger;with the increase of the separation blade height,the position of the backflow area changed,and the recirculation zone area in the concave cavity became larger,the high velocity area in the concave cavity became smaller.Secondly,based on the similarity criterion,a set of scaling down design scheme from full size afterburner to scaled down experimental configuration was studied,and its corresponding criterion was formed in the paper.In order to keep the similarity of flow fields for full size and scaled down afterburner,numerical comparison of flow field characteristics of the integrated afterburner before and after scaled down was analyzed.Results indicated that the scaled down model had the similar flow field with the calculated flow field of the original dimensional model.Finally,the test article and test scheme of the scaled down integrated afterburner was designed,and the influence of wall on the flow field and the flow resistance loss of the sector model test article was studied numerically.