Numerical modeling of laminar-turbulent transition in an interconnecting compressor duct

Abstract

With the purpose of meeting the challenging environmental targets set by the Euro pean Union (EU) in 2019, new sustainable fuels need to be inserted in the aviation industry [1]. Hydrogen stands out to be a promising candidate to be adapted into the aviation fuel mix due to its CO2-free combustion, and higher energy density com pared to kerosene.Nevertheless, due to its poor volumetric energy density, hydrogen (H2) storage requires higher aircraft volumes that leads to poorer aerodynamic per formances. Liquid hydrogen (LH2) offers a two-fold increase in volumetric energy density to that of highly compressed H2. This makes LH2 a prime candidate for aviation since it decreases the required volume by half. However, to fulfil the low weight requirements set by aircraft, the liquid hydrogen must be stored at cryogenic temperatures at a pressure close to or slighter higher than ambient. As a conse quence, adequate tank insulation technology needs to be developed. In addition, with the goal of increasing the effective heating value of hydrogen, heat exchanger technology must be included in the fuel distribution system. Up to the present time, different heat exchanger technologies placed in the vicinity of the engine have been investigated [2] This project focuses on how to model the vane surfaces of an Intermediate Compres sor Duct (ICD) using CFD for the purpose of intercooling to support and prepare for future validation work using the Chalmers low pressure compressor rig. This study will analyze the behavior of different CFD transition models in the prediction of laminar-turbulent transition, mesh dependency, impact of wall temperature as well as theoretical validation of the results. CFD simulations using the Gamma-Theta and Intermittency transition models showed very similar results and highlighted the need of well-refined computational grids in order to reach mesh independence for pressure loss, heat flow, and tran sition onset and duration. A parametric study where the vane wall temperatures were decreased showed that transition was delayed for decreasing wall temperatures and that the length of the transition zone decreased as well. Moreover, flat plate correlations employed to validate the results turned out to not be accurate enough in the prediction of transition.