Research On The Flow Structure Of Double-jet Film Cooling Hole And The Mixing With Mainstream

In order to study the flow field structure of mainstream mixed with flow field and the influence of the width of trenched double-jet film cooling holes,the flow character-istics of the basic Double-jet film cooling holes and trenched double-jet film cooling are tested by hot wire anemometer.The difference of trenched double-jet film cooling holes with different width(W)were compared.In this research,a typical compound angle of cylindrical film cooling hole is regarded as the object to measure downstream flow characteristics by using hot wire anemometer,and compared with the published results.The diameter of all three holes at the inlet was 10 mm.These holes were machined into flat aluminum test plates 30 mm thick.All three holes were inclined at 30 deg,giving a length-to-hole diameter ratio of L/D = 6,where L is measured along the hole centerline axis at the hole inlet.This experiment system is verified reliable.On this basis,to achieve flow field structure and rules of holes mixing with mainstream,double-jet film cooling hole and trenched-double-jet film cooling holes are measured at different blowing ratio(M=0.5?1.0?1.5)and different width(W=4D?4.5D?5D)of trench.By using hot wire anemometer,the velocity boundary layer thickness,transverse diffusion capacity,downward diffusion capability and the ability to penetrate the mainstream boundary layer can be obtained by analyzing these physical quantities,such as mean time and pulsating speed along the direction of flow field.It can be found that when the M = 0.5,the film of double-jet film cooling holes can effectively insulate the hot air from the surface of the flat wall.With the increasing of M,trenched-double-jet film cooling holes lateral expanding coverage wider than double-jet film cooling.In this paper,when the trench width is 4.5 times of the diameter,the best film cooling effect is reached.