Numerical modeling of laminar-turbulent transition in an interconnecting compressor duct
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Typ
Examensarbete för masterexamen
Program
Modellbyggare
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Sammanfattning
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.
Beskrivning
Ämne/nyckelord
Turbulence transition model, intermediate compressor duct (ICD), heat exchanger, hydrogen.