Periodic Reporting for period 2 - EVAL (Aircraft Engine Valves Thermal Management with Advanced Loop Heat Pipe)
Periodo di rendicontazione: 2021-09-01 al 2023-11-30
An aircraft engine bleed system extracts the air from the compressor and supplies it to various locations within the aircraft for the purposes of cabin pressurisation and air conditioning, internal cooling of the engine, airframe anti-icing, etc. A new generation of turbojet engines with ultra-high bypass ratio (UHBR) will be more energy efficient and environmentally friendly, but their components will operate in a harsher environment due to increased compression ratio and gas temperature in front of the turbine.
Being funded by the Clean Sky 2 Joint Undertaking, the EVAL project aimed to develop and manufacture a demonstrator of a passive cooling system based on a loop heat pipe (LHP) technology for efficient thermal management of UHBR engine bleed system valves exposed to a very harsh environment. The EVAL demonstrator testing and validation in an aircraft engine representative environment showcased the advantages and drawbacks of LHP technology for the target application.
To achieve this aim, the EVAL consortium focused on three specific technical objectives:
• O.1: Selection of working fluid(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.
• O.2 Development and testing of a passive cooling system demonstrator, which needs to transfer 100 W of heat for the distance of 30 cm with or against gravity in case of hot source and heat sink temperatures equal to 200 °C and 100 °C respectively.
• O.3: Ensuring a passive cooling system demonstrator, whose weight and volume provides good accommodation with the elements of the UHBR engine bleed system.
These specific objectives and the overall project aim have been successfully achieved by the EVAL team.
Being funded by the Clean Sky 2 Joint Undertaking, the EVAL project aimed to develop and manufacture a demonstrator of a passive cooling system based on a loop heat pipe (LHP) technology for efficient thermal management of UHBR engine bleed system valves exposed to a very harsh environment. The EVAL demonstrator testing and validation in an aircraft engine representative environment showcased the advantages and drawbacks of LHP technology for the target application.
To achieve this aim, the EVAL consortium focused on three specific technical objectives:
• O.1: Selection of working fluid(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.
• O.2 Development and testing of a passive cooling system demonstrator, which needs to transfer 100 W of heat for the distance of 30 cm with or against gravity in case of hot source and heat sink temperatures equal to 200 °C and 100 °C respectively.
• O.3: Ensuring a passive cooling system demonstrator, whose weight and volume provides good accommodation with the elements of the UHBR engine bleed system.
These specific objectives and the overall project aim have been successfully achieved by the EVAL team.
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).
• 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).
The EVAL innovative approach consisted in a combination of:
(i) Toluene – non-standard working fluid for the LHP technology – that is able to meet the UHBR bleed system valve cooling requirements and aeronautical standards, and
(ii) the EU’s domestic patented technology of evaporator-reservoir modular unit (ALTOM), which makes it possible to create thermal management systems, which are superior in thermal performance, compact, lightweight, robust, reliable, easy-to-integrate and still cost-effective.
Within the EVAL project, new knowledge regarding the LHP application in harsh environment was generated including different working fluids applicability and validated methodology of the LHP operation modelling. This knowledge was partially disseminated through conference participation and peer-reviewed publications and will be further used by the EVAL partners and third-party experts in their R&D and academic activities.
As for the LHP demonstrator, the project activities were concentrated within the TRL 4–6 range and resulted in the validation and testing of the LHP demonstrator in the relevant environment. At the next stage, The EVAL Topic Manager (Liebherr) will launch further testing of the EVAL LHP demonstrator in the “target environment” in the frame of the Large Passenger Aircraft IADP activities of the Clean Sky 2 JU. In the future, the EVAL thermal management system – playing the role of “enabling technology” – will ensure accurate and precise regulation of the airflow in the UHBR engine, thus contributing to the reliable and efficient long-term operation of the engine as a whole.
(i) Toluene – non-standard working fluid for the LHP technology – that is able to meet the UHBR bleed system valve cooling requirements and aeronautical standards, and
(ii) the EU’s domestic patented technology of evaporator-reservoir modular unit (ALTOM), which makes it possible to create thermal management systems, which are superior in thermal performance, compact, lightweight, robust, reliable, easy-to-integrate and still cost-effective.
Within the EVAL project, new knowledge regarding the LHP application in harsh environment was generated including different working fluids applicability and validated methodology of the LHP operation modelling. This knowledge was partially disseminated through conference participation and peer-reviewed publications and will be further used by the EVAL partners and third-party experts in their R&D and academic activities.
As for the LHP demonstrator, the project activities were concentrated within the TRL 4–6 range and resulted in the validation and testing of the LHP demonstrator in the relevant environment. At the next stage, The EVAL Topic Manager (Liebherr) will launch further testing of the EVAL LHP demonstrator in the “target environment” in the frame of the Large Passenger Aircraft IADP activities of the Clean Sky 2 JU. In the future, the EVAL thermal management system – playing the role of “enabling technology” – will ensure accurate and precise regulation of the airflow in the UHBR engine, thus contributing to the reliable and efficient long-term operation of the engine as a whole.