Abstract:
According to the statistics about civil transportation aircraft Environmental
Control system (ECS), the three-wheel high pressure water separation system
(HPWS) and low pressure water separation system (LPWS) are the most
common choices for the 150-seat airliners. Although the former has become the
mainstream configuration for air conditioning pack, the latter is still used on
Boeing 737-600/700. In order to compare the two configurations and choose the
better one for a specific aircraft, simulation and analysis are done.
The cabin heat load is calculated at first in order to calculate required engine
bleed air mass flow. Then a specific aircraft is defined so that required structural
dimensions and cabin comfort indexes can be obtained based on Airbus 320.
Thirdly, the component models are built by Matlab/Simulink according to the
fundamental knowledge of heat transfer and aerodynamics, the working
principles and mechanical dimensions of the components, the ambient
environmental parameters and some data from Airbus 320. Consequently, the
complete system model can be assembled. After confirming the validity of the
model by checking the required ram air mass flow and temperature deviation of
the state points referred to Airbus 320, the simulation model is used to do
analyze the specific aircraft. Finally, through comparing the different values of
ram air mass flow and turbine expansion ratio, as well as the system mass,
economic cost and reliability, the better configuration is selected.
It can be summarized that the three-wheel LPWS requires less ram air mass
flow (0.012kg/s) and a little lower expansion ratio (0.02) than the HPWS, and it
also has lower weight (63% of HPWS), lower (83% of HPWS) cost and higher
reliability (140% of HPWS), thus it is the suitable configuration for the specific
aircraft.
