Influence of rake number on steady-state distortion characteristics measurement of intake tract

In relevant tests of modern fighter intake tracts, due to complex factors such as low-speed auxiliary inlet opening, stealth of large S-bend pipes, and high angles of attack sideslip flight attitude, flow field distortion in the intake tract is large, and the test results from different numbers of rakes differ greatly. There are many studies on the measurement and calculation of steady-state distortion of outlet flow in the intake tract at home and abroad, but few comprehensive comparative studies have been conducted for the influence of the rake number on the measurement of steady-state distortion in the intake tract. In this study, by measuring the large pressure gradient region, low pressure region and steady-state distortion in the intake tract, a comparative study is conducted on the commonly used forms of 6 and 8 rakes in the intake wind tunnel test, full-scale advance joint bench test, and advance matching flight test. The research results show that, for complex shaped fighter inlet, the measurement of outlet flow field of the intake tract requires as many as 8 measuring rakes to achieve satisfactory results. Particularly, in the shipboard environment, flow in the intake tract is more complex due to factors such as bow inflow and deflector reflection, and the engine requires more stringent requirements for the stability of the advance matching as operated in a special reheating state; thus, it is more necessary to adopt the measurement with 8 rakes under this circumstance.