Effect of heat exchanger integration in aerodynamic optimization of an aggressive S-duct

Paper in proceeding, 2022

Intercooling the core flow in the compression process using bypass air can potentially reduce fuel consumption in commercial aviation. However, one of the critical challenges with intercooling is the installation and weight penalty due to complex ducting and large surface area for air-to-air heat exchangers (HEX). The recent interest in cryogenic hydrogen (LH2) as a potentially carbon-neutral fuel for commercial aviation expands the propulsive
system’s design space due to the vastly different fuel properties between classical Jet-A and LH2. Regarding intercooling, LH2 adds a formidable heat sink with a high specific heat capacity and low storage temperature at 20K and, if utilised in the intercooling process, should allow for increased cooling power density with less installation penalties than an air-to-air HEX. Furthermore, the heat is transferred to the fuel instead of ejected
into the bypass air which has potential thermodynamical benefits. The HEX can further be synergistically used to radial turn the core flow in the ICD.
This paper presents the integration of a compact air-to-LH2 heat exchanger inside the gas path of the intermediate compressor duct (ICD) as the shape of a truncated cone. Axisymmetric numerical simulations areutilised to evaluate the duct performance and optimise hub and shroud lines for minimal pressure drop andoutlet uniformity. The HEX sizing was based on a preliminary system model of an LH2 commercial aviation engine with 70,000 lbs of thrust.