Experimental and numerical investigation of heat transfer for an obliquely impingement

An experimental and numerical study is performed to investigate heat transfer and pressure loss characteristics for an obliquely impingement. Experimental heat transfer is measured by the thermosensitive liquid crystal. The CFD model uses a steady state RANS approach and the shear stress transport (SST). The effect of Reynolds number (15000-100000), inclination (30,45,60) and the number of the impingement plenums on the obliquely impingement is investigated in the present study. Local Nusselt number as well as area and line average values are gotten experimentally and numerically. Besides, numerical simulations provide the detailed flow characteristics of the problem and complement experimental measurements. The results show that the heat transfer increase with Reynolds number increasing. But the distribution of local heat transfer is the same qualitatively with different Reynolds number, when it is sensitive to inclination angle. The number of the impingement plenums has little effect on the heat transfer. INTRODUCTION In order to get higher efficiency of aircraft engines, higher gas turbine temperature is needed. Turbine inlet temperature ranges from about 1800K to 2100K for aircraft propulsion or power generation. And the maximum material temperature ranges from 1300K to 1600K. The increasing inlet temperature has already exceeded the maximum material temperature. In order to prolong the turbomachinery component’s lifetime and ensure safe operation, the effective cooling technique is necessary. Impingement cooling is widely used as an impactful cooling method, as it is relatively simple to apply. Besides, impingement cooling is also an effective method to improve the local heat transfer. Jet impingement can get a great heat transfer enhancement near the stagnation. There are many studies on impingement cooling having been carried out continuously, including experimental and numerical methodology. Goldstein et al.[1] established a correlation equation for the average heat transfer coefficient of a single hole impinging jet in 1986. Then Downs and James summed up the circular hole and slot jet correlations in 1987. Huang et al.[2] studied the heat transfer characteristics of an inclined jet in 1996 using transient liquid crystal technology. The results show that the heat transfer coefficient of the inclined jet is lower than that of the straight impingement on the target due to the influence of the crossflow. Matt Goodro et al. [3] studied the influence of temperature on impingement cooling, and put forward the relevant correlation formula. Simon Schurren et al.[4] studied the heat transfer characteristics of inclined impingement cooling using different shapes of the hole. By numerical method combined with the experiment, the heat transfer characteristics of circular holes and cone holes were compared. Sebastian Schulz et al.[5] studied the influence of the thermal mixing in the inclined impingement hole by using transient liquid crystal technology. The flow field measurement has been carried out by PIV. It is found that the distribution of efficiency is independent of Reynolds number. Florian Hoefler et al. [6] studied the difference between smooth target and rib target surface on oblique impingement, and researched the influence of fins with different heights on heat transfer. Combining experiment and numerical calculation, it was found that the average heat transfer coefficient of surface with ribs was lower than that without ribs, However, the total heat flux of the rib surface was higher because the ribs increase the heat transfer area.