滑流层对轴对称外压式进气道稳定性的影响

 本文论述了在来流M1.72条件下,一个可变中心锥外压式进气道,强度为5～11％的六种滑流层在各种位置上进入唇口时对进气道稳定性的影响。 试验证明,强度低于10％的滑流层在唇口附近进入该轴对称进气道,并没有引起进气外罩内侧的附面层分离 强度直至11％的滑流层可以在进口处任意位置上进入该进气道,而不产生喘振。文献表明,强度仅为6～7％的滑流层就可以导致二元进气道的喘振,从而显示了轮对称进气道对滑流层进入所引起的喘振有较强的抵抗能力。

EFFECT OF A SHEAR LAYER ON STABILITY OF AN AXISYMMETRIC EXTERNAL COMPRESSION AIR INTAKE

The purpose of this investigation is to find out the effect of shear layers with various strength on stability of an axisymmtric external compression supersonic air intake.Although A.Ferri's theory on stability of an air intake is well known,it does not tell how strong the shear layer has to be in order to produce a noticeable effect on an air intake.S.A.Fisher's work shows that for a side intake,a shear layer with a strength about 6% to 7% is required to induce a buzz in the two-dimensional intake.Here "strength" is defined as the ratio of total pressure difference between the two sides of a shear layer to the total pressure of incoming flow.But,for an axisymmetric intake,it is still necessary to find out how it responds to action of a shear layer with a specific strength. Experiments were carried out in a free stream wind tunnel with a fixed Mach number M=1.72.Six central bodies with different cone angles were used to produce shear layers with strength ranging from 5% to 11% of total pressure of upstream flow.Experiments indicated that shear layers with strength lower than 10% were strong enough to cause separation of the boundary layer from the inside surface of the cowl.They also showed that shear layers with strength lower than 11% were unable to induce buzz in the axisymmetric intake tested,while,according to literature,a shear layer with much lower strength could cause a two-dimensional intake to buzz.The experiments also testified that the effect of a shear layer depended on its distance from lip of the cowl,and the effect was the most noticeable at its distance equal to 10% to 18% of the cowl radius.It is possible to conclude that a two-dimensional intake is more sensitive than an axisymmetric one to the effect of a shear layer.