Optimization Of A Variable Geometry Chin Inlet Adjusted By Throat Slider

The supersonic chin inlet of missile has many advantages such as high compression efficiency,small external drag and high degree of fusion with the missile body.However,in order to take the performance at low Mach numbers into account,conventional fixed geometry schemes often lead to lower performance at high Mach numbers,while the special curved structure of chin inlet makes variable geometric adjustment difficult.Aiming at the working requirements of Ma2.5～4.0 for chin inlet,a simple scheme of the variable geometry adjustment is proposed and designed.The throat size at high and low Mach numbers is changed by moving the slider forth and back so that the inlet can meet the compression requirements at high and low Mach numbers.First of all,the design of the axisymmetric isentropic compression profile is developed.Based on the adjustment principle,the matching design between slider profile and inlet internal channel profile is conducted,meanwhile,the key design parameters of the slider are studied and a scheme with good performance is obtained.The performance of variable geometry chin inlet is compared with that of conventional fixed geometry scheme.Numerical simulation results show that the height of the slider depends on the width of the working range.Leading edge angle δ and rear wedge angle β of the slider are also important parameters that affect the design of chin inlet,both of them should be as small as possible under the premise of satisfying the structure requirements The aerodynamic performance of variable geometry chin inlet is obviously better than fixed geometry scheme,which is 14.4%improved in exit critical total pressure recovery coefficient at cruise point of Ma4.0,6 degree angle of attack.Secondly,according to the three-dimensional effect of the external compression section of chin inlet,the influence of the side plate on the inlet performance is studied.Based on the characteristics of the flow field,the optimization study of the external compression section and lip configuration is carried out.Study shows that the side plate can significantly inhibit the overflow of chin inlet.Compared with the case without side plate,the flow coefficient of chin inlet with side plate at design and cruise point is increased by 4.2% and 5.1% respectively.The optimization of the isentropic compression profile of the external section can improve the critical total pressure recovery coefficient at the cruise point of inlet by 10.4%.Within the working range,both pre-lip and space curve lip optimization schemes can improve the flow coefficient.Compared with the pre-lip scheme,the total pressure recovery at throat area of the space curve lip configuration at cruise point is higher.Finally,in order to further suppress the lateral overflow of the external compression section of chin inlet,and to improve the uniformity of the flow field at the entrance of internal compression section,as for the design angles of attack of 0 degree and 6 degree,the integrated design of waverider forebody and chin inlet as well as practical modification are conducted.Research result shows that the use of waverider for external compression section can improve the flow field at the entrance of internal compression section.Also,the flow coefficient and overall performance are significantly improved.The 6 degree design angle of attack waverider increases the flow coefficient of chin inlet by 3.6% and 9.7% at high and low Mach numbers respectively,and the exit critical total pressure recovery coefficient is increased by 9.6% and 5.2% respectively.The practical configuration reduces the size of the forebody on the basis of ensuring the performance of the inlet,which has practical engineering application value.