Cooling characteristics of the trailing-edge slot downstream from internal multi-ribbed channel

Abstract

To investigate the cooling characteristics of the trailing-edge slot fed by the coolant channel with the straight ribs arranged at small pitch, the effects of the straight rib height and blowing ratio on the adiabatic cooling effectiveness and convective heat transfer coefficient of expanded cutback surface were studied by using the steady pressure sensitive paint technology and transient thermochromic liquid crystal technology, respectively. The cutback discharge coefficient and cooling performance under the multi-ribbed channel were analyzed and discussed, then the heat flux ratio was introduced to evaluate the optimal cooling structure. The experimental results showed that the discharge coefficient of trailing-edge slot increases slightly with the increase of blowing ratio, which is opposite to the increase of rib-height. At low blowing ratio (M≤0.50), the increase of the rib-height significantly strengthens the degree of jet disarray. As the coolant core region upstream of the slot-exit changes, a region with low adiabatic cooling effectiveness appears in the downstream. At the excessive blowing ratio(M=0.75), the adiabatic cooling effectiveness of the ribbed case with low height shows an abnormal trend opposite to the increase of blowing ratio. As the flow loss (based on the discharge coefficient) of the large height case is intensified, the instability of the cold vortex is strengthened, which cancels out the dominance of the flow field. The case with multi-ribbed channel can significantly improve the heat transfer performance of the region near the slot-exit. At large blowing ratio(M≥1.00), the high heat transfer coefficient area near the slot-exit develops into a core region with the high heat transfer coefficient, which can be extended to the downstream of the flow direction for the low height case. The optimal case with rib height of h/H=0.3 can improve the overall cooling effectiveness of the cutback surface by 20∼50%.