Research On Film Cooling Characteristics From Pin-fin Mesh-fed Slot

As an effective means of thermal protection,film cooling has been widely used in the cooling of gas turbine engines.It is well known that the two-dimensional slot is an ideal film cooling structure,which can form a uniform film layer over the protected surface.However,due to many practical constraints in turbine design,it is impractical to be used on the surface of a hot turbine component.In recent years,some scholars have combined the near-wall cooling with the surface slot film cooling.At present,the research on the new cooling method is very lacking.Based opon the background mentioned above,the characteristics of film cooling from pin fin mesh-fed slot is investigated numerically and experimentally in the present study.Firstly,numerical simulations are performed on the adiabatic cooling characteristics of film cooling from pin fins mesh-fed slot.Some geometric and aerodynamic factors,such as lip bevel angle,shapes of pin fins and blowing ratio are taken into considerations for illustrating their affecting roles.The results show that the distribution of coolant air velocity around the exit of pin fins mesh-fed slot is very non-uniform,and the lip angle has a great effect on the cooling effectiveness and the interaction between the primary flow and the coolant jet flow.Compared with circular pin fins,the oval-shaped and droplet-shaped pin fins perform better adiabatic film cooling effectiveness and lower flow resistance or better flowing capacity inside the pin fin mesh-fed slot.Film cooling effectiveness is improved a certain with the increase of blowing ratio.By adding pin fins into the slot film cooling structure,not only the downstream wall could be cooled,but also upstream wall could be cooled too.Therefore,numerical simulation on the overall cooling characteristics of this slot film cooling structure is performed.The data during the calculation is analyzed to study how the factors affect the overall cooling characteristics,such as shapes of pin fins,length of pin fins channel,diameter of pin fins and blowing ratio.The results indicate that for the upstream wall circular pin fins perform better in overall cooling effectiveness compared with the oval-shaped and droplet-shaped pin fins.However,for the downstream wall the situation is opposite,in which oval-shaped and droplet-shaped pin fins perform better than circular pin fins.As the length of pin fins channel gets shorter,the cooling scope of upstream wall becomes smaller but the cooling of downstream wall bacomes better and the discharge coefficient becomes smaller,which indicates that the flowing capacity of film channel is better.The overall cooling characteristics and discharge coefficient becomes better with the decrease of diameter of pin fins.With the increase of blowing ratio,the overall cooling effectiveness is well improved.On the basis of numerical simulation,experimental tests on the adiabatic and overall cooling effectiveness under different shapes of pin fins are carried out.It is demonstrated that the experimental results are in good agreements with the corresponding numerical results.