| Gas turbine has been widely utilized in gas power industry to achieve a better efficiency of power convert rate.Film cooling is a technique to deal with high turbine inlet temperature and solve turbine cooling issues.In order to achieve a higher overall efficiency for the next generation of gas turbomachinery,this dissertation focuses on traditional manufacture technique and 3D pringting,to unveil the influence of their accuracy upon heat transfer and fluid features of film cooling.The tradition manufacture technique causes geometry deviation of film cooling hole.Here,an Uncertainty Quantification(UQ)method is introduced to analysis this deviation.Several typical film cooling geometry deviation models and a called PCE method UQ analysis platform are firstly created.Key parameters of round film cooling hole – hole size,hole location deviation,shape deviation-are successfully and precisely tested both experimentally and numerically for their influence on heat transfer and flow-field.The data illustrate that sensitivity of those parameters is in an order of hole diameter.The reason is that when increasing film cooling hole diameter,the momentum of flow is increasing.Wall melting roughness is the key factor to create geometry deviation upon film cooling effectiveness.Due to the block of those melting roughness in the hole,turbulence impulse of cooling air is getting weak as well as its lateral spreading ability.This dissertation is based on high accuracy CT scan digital cloud data,through reverse simulating analysis to achieve a high accuracy modeling method for film cooling hole using 3D prototype.Here,multiple 3D printing methods and post-processing for round film cooling hole are considered.It is believed that different printing directions result sedimentation randomly within the hole,and leading edge of the roughed round hole performs a divergent film cooling effect.Post-processing does not change the overall cooling feature of the 3D printing hole.A platform,combines 3D printing,CT scan,reverse modeling,and CFD simulating,is developed to analysis the influence of 3D printing on film cooling.The research also considers 3D printing direction on fan-shape hole,and the influence of geometry deviation on film cooling.The varying locations of the roughness caused by printing result in a difference of cooling effectiveness.A roughed leading edge causes a forward shift separating bubble as well as the pressure gradient from leading edge to trailing edge pushes the flow to the side,resulting in a branching cooling air passage on target surface and low cooling effectiveness for the center part.A roughed trailing edge preforms oppositely.Cooling air is compressed to the flow passage center,causing a stronger cooling effect along the center and lower cooling effects along the sides.For the numerical analysis,LES is utilized for the roughed fan shape film cooling hole fluid structure.It is said that there is unique high temperature invade the outlet area of the roughed hole.Vortex around the turning area region of leading edge is together with high temperature main stream merges into the downstream boundary layer,causing an elevating of wall temperature,which illustrate that 3D printing is a key mechanism to diminished fan-shape film cooling effectiveness.This dissertation helps understanding the accuracy of 3D printing,and contributes the 3D printing method on promoting cooling effective structures. |
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