Reliability Case Analysis of an Autonomous Air Cooling System (AACS) for Aerospace Applications 2018-01-1916
Current More Electric Aircraft (MEA) utilize Liquid Cooling Systems (LCS) for cooling on-board power electronics. In such LCS, coolant pipes around the structure of the aircraft are used to supply water glycol based coolant to sink heat from power electronics and other heat loads in the electronic bay. Subsequent extracted heat is then transferred to ram air through downstream heat exchanger/s.
This paper presents a reliability examination of a proposed alternative Autonomous Air Cooling System (AACS) for a twin engine civil MEA case study. The proposed AACS compared to the LCS, utilizes cabin air as the coolant which is in turn supplied using the electric Environmental Control System (ECS) within the MEA. The AACS consist of electrical blowers allocated to each heat load which subsequently drive the outflow cabin air through the heat sinks of the power electronics for heat extraction. No additional heat exchanger is required after this stage in which the heated air is directly expelled overboard. One key advantage is that higher levels of control are possible for the attainment of higher system efficiency. The other key advantage is the avoidance of liquid coolant leakage risks with the removal of liquid coolant from the MEA.
However, to justify the potential application of this new approach, the reliability is required to be in line with FAA/JAA reliability limits. As such, the provided reliability analysis in this paper covers the reliability of such AACS as well as the subsequent operation of safety critical components of the ECS and Electrical Power System (EPS) that the AACS is cooling. The case study results show such a proposed AACS can provide comparable reliability and within FAA/JAA reliability limits.
Chung man Fong, Patrick Norman
University of Strathclyde
Aerospace Systems and Technology Conference