An intercooled turbofan engine was proposed within the EU Framework 6 New Aero Engine Core Concepts (NEWAC) programme. Intercooler heat exchangers are inserted between the intermediate and high pressure compressors for the cooling of the engine core flow, which uses the flow in the bypass duct (BPD) as the heat sink. A cooling flow passage was incorporated into the turbofan engine to convey some of the BPD flow to the intercooler (figure 1). An annular zigzag heat exchanger arrangement using cross-corrugated primary heat transfer surface matrices was adopted for the current application where the heat exchanger matrices are angled to the oncoming flow (figure 2). In this configuration, the inlet of the cold side of the matrices is subjected to a cross flow which passes tangentially across the inlet plane and a through-flow which is ingested into the matrices as the cooling flow. The concept of a turning vane integrated into the inlet of the matrix to reduce the entry losses. In this paper the aerothermal performance of the cross-corrugated inlet integral turning vanes is characteriesed. The local heat transfer coefficient distribution measurements using transient liquid crystal (TLC) technique and the local pressure drop in a large scale model of the cross-corrugated passage are reported; the geometry is representative of a single passage of a cross-corrugated heat exchanger proposed for the NEWAC intercooled turbofan engine. A key purpose of the experimental campaign was to determine the heat transfer enhancement in the first few corrugations of the heat exchanger, where the local heat transfer coefficients can deviate significantly from the fully developed value, which is also reported for comparison to existing data in the literature. This was useful in identifying the flow structures driving heat transfer in the passages. In addition, the heat transfer pattern on the side walls of a cross-corrugated passage were reported for the first time. Tests were performed over a range of Reynolds numbers (1300 ＜ Re ＜ 8200) and cross-flow to through-flow velocity ratios (0.4 ＜ u_X/u_T ＜ 3.8) which represent engine operating conditions. The pressure drop through each of the corrugated passages is also reported and shows that entrance features are capable of recovering much of the flow dynamic head at high cross-flow to through-flow ratios. The results also show significant heat transfer enhancement in the entrance region at high cross-flow to through-flow ratios, and provide, for the first time, comparative heat transfer levels between the entrance and fully developed flow regions. The heat transfer data are averaged and correlated on a row by row basis to provide appropriate input for heat exchanger optimisation studies .
展开▼
