An Investigation On Jet Impingement Heat Transfer In A Typical Concave Cavity

The leading edge of the turbine blade is directly impacted by the high temperature gas,which is in an extremely harsh thermal environment.In order to ensure that the turbine blades operate normally under high temperature conditions,an efficient cooling method is essential.After vast research and exploration during the past decades,cooling technology has become increasingly sophisticated.Due to its high heat and mass transfer rates,jet impingement has been widely used in the internal cooling of the leading edge of the turbine blade.Based on the leading edge of turbine blade,this paper extracts the model of jet impingement on the internal surface of the confined cavity.The flow and heat transfer mechanism of jet impingement with four arrangements of the jet orifices are studied by numerical method.The effects of various parameters on the flow and heat transfer with jet-offset arrangement,jet-staggered offset arrangement and jet-tangential arrangement are mainly concerned.From the current study,the main conclusions are summarized as the followings:When the jet orifices are in offset arrangement,the impinging angle between the jet and the surface is reduced,leading to a decrease of heat transfer in the vicinity of the stagnation region.However,the attenuation speed of the wall jet velocity is reduced in the same time.With the reduction of the orifice diameter,the jet velocity is increased,resulting in a stronger jet impingement heat transfer on the target surface but also a larger flow loss.The change of jet angle causes the variation of the jet-to-surface distance,shows complicated influence on the heat transfer on the target surface.When the jet orifices are in staggered offset arrangement,the strong interaction coherence between the jets has a complex effect on the heat transfer.The influence of offset spacing on the heat transfer is tightly related to the change of the impinging angle and the angular vortex position.With the reduction of the orifice diameter,the wall jet flow is enhanced.As a consequance,a higher heat transfer is produced in the downstream region apart from the stagnation point.The axial distance between exhaust-hole and the jet orifice also has a significant influence on the overflow effect of the outflow from the exhaust holes.When the jet orifices are located tangentially,the rectangular orifice with a large aspect ratio is demonstrated to be more pronouncd for making the wall jet close to the surface and axial expansion,which is helpful for enhancing the convective heat transfer on the target surface.The change of the orifice diameter affects the jet velocity and the axial expansion of the jet,shows different influences on the heat transfer in the upstream and downstream regions.The axial distance between the exhaust hole and the jet hole has a great influence on the heat transfer in the zone between the adjacent jet holes,thus affects the overall heat transfer capacity on the entire target surface.In addition,the jet Reynolds number is the main factor affecting the jet impingement heat transfer.As the jet Reynolds number increases,the bulk-averaged heat transfer is increased gradually.On the basis of numerical simulation,experimental tests of jet impingement heat transfer on the confined concave target are carried out,under four different orifice arrangements.It is demonstrated that the experimental results are in good agreements with the corresponding numerical results.