Experimental and numerical studies on the enhanced heat transfer performance and the flow resistance characteristics of the double-wall cooling structure with jet impingement holes and pin fins

Abstract

The double-wall cooling as one of the most important cooling techniques of the hot-end components of aero-engine, the heat transfer performance of double-wall cooling structure can be significantly enhanced by the combination of jet impingement cooling and pin fins. Therefore, the double-wall cooling structure with jet impingement holes and pin fins has very important engineering application value. For the double-wall cooling structures with jet impingement holes and pin fins, the experimental studies have been carried out based on various of geometrical and flow parameters. Furthermore, the corresponding numerical simulations have also been carried out according to the corresponding experimental study conditions. In order to approximate to the real double-wall enhanced heat transfer structure of the hot-end components of the aero-engine, in present experimental and numerical studies, the double-wall enhanced heat transfer structure with the double-side outflow channel and the advantage of structural symmetry is adopted. Based on the numerical simulation results, the internal flow field structure, the flow resistance characteristics and the interior enhanced heat transfer performance of the double-wall cooling structure with jet impingement holes and pin fins are analyzed in detail. In addition, the main reasons why the pin fins can enhance the heat transfer performance of the double-wall cooling structure that with jet impingement holes and pin fins are further revealed. Actually, the enhanced heat transfer performance of the double-wall cooling structure is the results of the interactions between the internal jet impingement cooling, the internal crossflow and the turbulent flow of pin fins. Moreover, the influences of the jet impingement Reynolds number (Re), the non-dimensional row spacing (X/D) and the non-dimensional hole pitch (Y/D) of jet impingement holes, and the dimensionless diameter (Dp/D) of the pin fins on the enhanced heat transfer performance, the internal flow characteristics, the distributions of local Nusselt number Nu and the flow resistance characteristics of the double-wall cooling structure with jet impingement holes and pin fins are further revealed. Importantly, for all numerical simulation conditions, the distribution differences of the enhanced heat transfer performances on the wall surface of the pin fins and on the wall surface of the jet impingement target plate with the variations of the geometrical parameters and the flow parameters are analyzed in detail. The numerical results indicate that the area-averaged Nusselt number Nu═ on the wall surface of the pin fins is higher than that on the internal wall surface of the jet impingement target plate. With the increase of the pin fins diameter Dp/D, the Nu═ on the whole internal wall surface of the double-wall cooling structure presents a tendency of firstly decrease and then gradually increase. In addition, the Nu═ on the entire interior wall surface of the double-wall cooling structure decreases with the increase of row spacing X/D, but it is not sensitive to the variation of hole pitch Y/D. Moreover, for the discharge coefficient of the double-wall cooling structure, it gradually increases with the increase of the jet impingement Reynolds number Re, the row spacing X/D and hole pitch Y/D of jet impingement holes, but it decreases with the increase of the diameter Dp/D of pin fins. Finally, for 3 ≤ X/D ≤ 5, 3 ≤ Y/D ≤ 5, 1≤Dp/D ≤ 2, and 9000 ≤ Re ≤ 30,000, a correlation of the area-averaged Nusselt number Nu═ is given, which is in good agreement with the experimental results.