Research on Cooling Method in Surfacing Repair Process of Aero Compressor Blade

Abstract

For the cooling method in surfacing repairing, most of the research focuses on the method based on the fixture structure. However, due to the low thermal conductivity and ultrathin alloy blade, the heat transfer speed from the molten pool to fixture is slow. When the heat is transferred to the fixture, most of the molten pool has solidified and absorbed or segregated out some impurities. Therefore, how to cool the welding area directly is more critical. For this reason, the thermal cycle characteristics of typical points of the blade and the heat transfer process of the key area of the fixture are analyzed, the original cooling time is calculated, and two innovative cooling methods based on lateral forced convection cooling and vertical jet impact forced convection cooling are proposed. For lateral forced cooling, with “AF-field” lateral convection cooling modeling, the cooling effects of characteristic points and sections under different flow velocities are calculated. For vertical jet impact cooling, the pressure, flow rate, and convective heat flux distribution on the wall under different impact heights and nozzle diameter are calculated. The influence of different inlet flow rates on cooling performance is influenced, based on the analysis results of impact modeling, the moving heat sink model is established, and the cooling effect under different heat sink-source distances is calculated. The heat transfer rules of two methods are analyzed in detail through modeling and simulations. The results show that both methods can improve the cooling effect and the vertical jet impact cooling method has an effect that is more obvious. When the nozzle radius is 2 mm, the impact height is 4d, the inlet flow velocity is 35 m/s, and the distance is 7 mm, and the cooling time under the vertical jet impact method is shortened by 12.5%, which can achieve better cooling effect. The experiment further validates the effectiveness of the modeling and simulations.

Modeling of additive height and numerical analysis of cooling parameters for aero blade remanufacturing

“…Due to the temperature of the contact surfaces between the copper bonds and the blade being less than 427 • C, the thermal radiation resistance can be neglected (Bahrami et al, 2004a). The thermal contact resistance model can be seen to in other works (Zheng et al, 2014;Shi et al, 2018;Tariq et al, 2016;Yovanovich et al, 2006;Grujicic et al, 2005;Bahrami et al, 2004b) and our previous research (Dai et al, 2020b).…”

“…Because the test piece is very thin, there is a certain degree of horizontal error in the manual polishing of the upper surface before welding, so the morphology after surfacing has a certain degree of tilt. According to the experimental parameters obtained from previous studies (Gong et al, 2019;Dai et al, 2020a), the cross section morphology of the additive zone of two kinds of wire-feeding speeds (6 in min −1 (2.54 mm s −1 ) and 8 in min −1 (3.39 mm s −1 )) was measured by software. The results show that, although the cross sectional morphology is inclined to a certain extent, the roundness of the additive morphology of the two wire-feeding speeds is good, which is consistent with the theoretical model.…”

An Advanced Flexible Multiflow Path Fixture Cooling Method for Additive Manufacturing Repair of Aero Blades

“…According to the analysis of the heat conduction mechanism of the fixture in previous research [4], the heat exchange is mainly concentrated between the test piece and the copper bond. The rear of the copper bond and the specific base and cover of the fixture have little effect on the heat dissipation process.…”

“…The fluid flow should be considered in addition to the overall heat transfer characteristics [2,3]. Forced cooling of fluid is an effective cooling method in welding, which mainly includes air jet impact cooling [4], liquid gas cooling and water cooling.…”