Study on numerical method for transient thermal coupling through particle deposit layer and wall based on mesh morphing in a turbine cascade

Abstract With particle-laden air ingested into a turbine cascade, the particles could deposit on the blade wall after hitting, so that a particle layer gradually forms on the wall, which modifies the profile of the passage. The presence of a particle layer also changes the near-wall flow structure and heat transfer pattern through the boundary. In this study, a method is proposed to couple mesh morphing with the particle deposition. The cells where particles deposit are identified and assigned the thermal conductivity of the particle to transiently predict the effect of deposit layer on thermal boundary, considering both heat conduction and convection. After the validation of the numerical method, it is employed to predict conjugate heat transfer of particle deposition and mesh morphing in a cascade. The results show that particles with larger diameters tend to deposit near the trailing edge on the pressure side. When coupled with mesh morphing, the deposited layer forms a ridge which narrows the passage, increases the velocity, and causes fluctuations in the static pressure coefficient. Due to the much lower thermal conductivity of the particles, the existence of the particle deposit layer acts as a thermal resistance to decelerate the heat transfer from the mainstream gas to the blade wall. Consequently, the upper temperature of the deposit layer becomes relatively higher.