Being a multidisciplinary initiative, the EVAL project combined desk research, design and manufacturing activities, experimental studies and advanced numerical simulation. Therefore, the AMBEC team was particularly focused on the planning and implementation of the following technical activities:
• An extensive assessment of 782 chemical substances that are used as working fluids in different thermal management systems was performed to identify one(s) that is able to comply with the requirements for heat dissipation in a harsh environment, ensure efficient LHP operation and meet the aeronautical standards.
• Four shortlisted candidate fluids (methanol, toluene, acetone, and 1,2-dichlorobenzene) were deeply investigated incl. lifetime study of chemical stability and compatibility with LHP wick material (SS 316L stainless steel) at high operational temperatures. Based on the data processing, toluene was selected as the working fluid for the EVAL demonstrator of the LHP-based passive cooling system.
• The toluene-based LHP demonstrator was designed and manufactured through an iterative process in close collaboration with the EVAL Topic Manger Liebherr to develop a demonstrator that meets all UHBR engine bleed system criteria, including (1) the valve geometry, dimensions, free space available around, (2) temperature and heat flux conditions within the engine compartment, and (3) parameters of the secondary airflow.
• In parallel, a numerical simulation of the LHP demonstrator operating in a harsh environment was launched with the aim of developing a methodology for LHP performance prediction. Acceptance numerical simulation was provided to investigate the influence of the type of insulation and the LHP orientation. The acceptance simulation was run for the two engine flight cases (“Engine start” and “Take Off”) with different heat rejection conditions.
• Also, a sophisticated test bench that enabled the LHP demonstrator’s testing in an environment relevant to the real one within the UHBR engine compartment was designed and developed. Being originally planned to be implemented in Ukraine, the LHP demonstrator validation and testing campaign was transferred to Latvia due to the Russian invasion of Ukraine in February 2024.
• The test campaign included 180+ test points to assess the LHP operation and insulation efficiency in case of different combinations of heat load and operation temperatures for different orientations in the gravity field. The results demonstrate that the proposed LHP design is effective in addressing the cooling requirements of critical components in the engine. The LHP provides stable operation and reliable heat dissipation within the specified temperature limits (less than 200°C) in almost all ranges of the heat sink temperature and the LHP heat load.
• Finally, the second LHP demonstrator was manufactured by Allatherm company following the knowledge obtained during the research, design, manufacturing and, most importantly, testing of the first LHP demonstrator. The second LHP demonstrator was sent to the EVAL Topic Manager (Liebherr) for further testing in the target environment.
Project results were presented at the 11th and 13th EASN International Conference on Innovation in Aviation & Space. Two peer-reviewed open-access publications were prepared to disseminate the knowledge generated and approaches developed (1 published and 1 submitted for publication). Basic project information is stored on the project website (
https://eval.khai.edu(odnośnik otworzy się w nowym oknie)).
