Periodic Reporting for period 2 - IMOTHEP (Investigation and Maturation of Technologies for Hybrid Electric Propulsion)
Periodo di rendicontazione: 2021-07-01 al 2022-12-31
To meet the goal of a carbon neutral growth of commercial aviation, the top-level objective of IMOTHEP is to achieve a key step in assessing the potential offered by hybrid electric propulsion (HEP) and, ultimately, to build the corresponding aviation sector-wide roadmap for the maturation of the technology.
The core of IMOTHEP is an integrated end-to-end investigation of hybrid-electric power trains for commercial aircraft, performed in close connection with the propulsion system and aircraft architecture. Aircraft configurations are selected based on their potential for fuel burn reduction and their representativeness of a variety of credible concepts, with a focus on regional and short-to-medium range missions. From the preliminary design of the aircraft, target specifications are defined for the architecture and components of the hybrid propulsion chain. Technological solutions and associated models are then investigated with a twenty-year timeframe perspective. In order to identify key technological enablers and technology gaps, the integrated performance of the electric components and power chain will be synthesized by assessing the fuel burn of the selected aircraft configurations, compared to conventional technologies extrapolated to 2035. The project will also address the infrastructures and tools required for HEP development, as well as the need for technology demonstrations or regulatory evolutions.
Eventually, all these elements will feed the research and technology roadmap of HEP, which will constitute the final synthesis of the project.
To achieve these ambitious goals, the four-year project is supported by 7 R&D institutes, 11 industrial partners (from aviation and electric systems), a service SME and 7 universities from 9 European countries, plus the CNRC in Canada.
The core of IMOTHEP is an integrated end-to-end investigation of hybrid-electric power trains for commercial aircraft, performed in close connection with the propulsion system and aircraft architecture. Aircraft configurations are selected based on their potential for fuel burn reduction and their representativeness of a variety of credible concepts, with a focus on regional and short-to-medium range missions. From the preliminary design of the aircraft, target specifications are defined for the architecture and components of the hybrid propulsion chain. Technological solutions and associated models are then investigated with a twenty-year timeframe perspective. In order to identify key technological enablers and technology gaps, the integrated performance of the electric components and power chain will be synthesized by assessing the fuel burn of the selected aircraft configurations, compared to conventional technologies extrapolated to 2035. The project will also address the infrastructures and tools required for HEP development, as well as the need for technology demonstrations or regulatory evolutions.
Eventually, all these elements will feed the research and technology roadmap of HEP, which will constitute the final synthesis of the project.
To achieve these ambitious goals, the four-year project is supported by 7 R&D institutes, 11 industrial partners (from aviation and electric systems), a service SME and 7 universities from 9 European countries, plus the CNRC in Canada.
During the first period of the project (January 2020 – June 2021), the following work had been performed:
- The first conceptual design “Loop 0” and performance evaluation of the four aircraft supporting configurations i.e. a conservative one and a radical one for both the regional and Short and Medium Range (SMR) missions;
- A preliminary design and low fidelity analysis of specific aerodynamic features of aircraft concept such as propeller design and integration, or boundary layer ingestion issues for inlet and fan design;
- The design and first assessment of the electric architecture for the four aircraft concepts; and
- The conceptual design of the various components of the electric power train from energy generation to electric machines.
The main achievement for the second period (July 2021 – December 2022) consisted of the second design loop of the project (“Loop 1”). During the second design loop, all the components of the power train were studied for the four configurations of hybrid aircraft supporting the project, based on the specifications issued from the preliminary aircraft design in Loop 0. Performance indicators were estimated for the proposed design of each component, such as specific power, efficiency and power density. In addition, geometric characteristics were provided. Electric architectures were defined as well. A safety / reliability analysis was performed for each of them and power management principles were investigated. The basis of a thermal management system were laid down. Aeropropulsive integration studies were carried out for the radical configurations using distributed propulsion and BLI.
All these information (except full representation of the thermal management system) were integrated in the second design loops of the configurations together with refined modelling, leading to a refined assessment of their performance in terms of fuel burn compared to the baseline aircraft for 2035.
In parallel, analysis of certification was initiated and a first exchange with EASA took place during spring 2022. Last but not least, a first synthesis of the results, together with a preliminary gap analysis and preliminary roadmap orientations, were issued in December 2022.
The third and last design loop ("Loop 2") was initiated towards the end of the period. It was decided to focus it on the radical configurations of aircraft for both the regional and SMR.
A second technical workshop was organised in September 2022 to share and discuss the results to date and organise the work of the third and last design loop (first technical workshop was organised in December 2021). For the first time since the kick-off meeting in January 2020, the meeting could take place physically in Eurocontrol’s premises in Brussels.
In addition, a number of presentations were given in various conferences during the second half of 2021 (AIAA, EASN, MEA, ICAS, ECCOMAS…) and in 2022 (3AF, EUCASS, EASN).
The objectives set for the end of Loop 1 were generally achieved. Regarding the planning however, the five to six months of delay observed at the end of the previous period caused by the Covid-19 pandemic could not be recovered.
- The first conceptual design “Loop 0” and performance evaluation of the four aircraft supporting configurations i.e. a conservative one and a radical one for both the regional and Short and Medium Range (SMR) missions;
- A preliminary design and low fidelity analysis of specific aerodynamic features of aircraft concept such as propeller design and integration, or boundary layer ingestion issues for inlet and fan design;
- The design and first assessment of the electric architecture for the four aircraft concepts; and
- The conceptual design of the various components of the electric power train from energy generation to electric machines.
The main achievement for the second period (July 2021 – December 2022) consisted of the second design loop of the project (“Loop 1”). During the second design loop, all the components of the power train were studied for the four configurations of hybrid aircraft supporting the project, based on the specifications issued from the preliminary aircraft design in Loop 0. Performance indicators were estimated for the proposed design of each component, such as specific power, efficiency and power density. In addition, geometric characteristics were provided. Electric architectures were defined as well. A safety / reliability analysis was performed for each of them and power management principles were investigated. The basis of a thermal management system were laid down. Aeropropulsive integration studies were carried out for the radical configurations using distributed propulsion and BLI.
All these information (except full representation of the thermal management system) were integrated in the second design loops of the configurations together with refined modelling, leading to a refined assessment of their performance in terms of fuel burn compared to the baseline aircraft for 2035.
In parallel, analysis of certification was initiated and a first exchange with EASA took place during spring 2022. Last but not least, a first synthesis of the results, together with a preliminary gap analysis and preliminary roadmap orientations, were issued in December 2022.
The third and last design loop ("Loop 2") was initiated towards the end of the period. It was decided to focus it on the radical configurations of aircraft for both the regional and SMR.
A second technical workshop was organised in September 2022 to share and discuss the results to date and organise the work of the third and last design loop (first technical workshop was organised in December 2021). For the first time since the kick-off meeting in January 2020, the meeting could take place physically in Eurocontrol’s premises in Brussels.
In addition, a number of presentations were given in various conferences during the second half of 2021 (AIAA, EASN, MEA, ICAS, ECCOMAS…) and in 2022 (3AF, EUCASS, EASN).
The objectives set for the end of Loop 1 were generally achieved. Regarding the planning however, the five to six months of delay observed at the end of the previous period caused by the Covid-19 pandemic could not be recovered.
IMOTHEP ambitions to provide a consolidated global picture of HEP for regional and Short and Medium Range (SMR) aviation, embracing the range of promising propulsion architectures and technologies. This should sustain the proposal of a comprehensive and timely roadmap for HEP development, taking into account synergies and scalability effects between the different missions.
Although a last more detailed iteration is scheduled on the radical configurations, IMOTHEP already brought significant progress in the assessment of various typical hybrid architectures. These could be investigated with well-controlled and homogeneous technology assumptions and a clear reference baseline for comparison with conventional propulsion projected to 2035. In addition, design could be proposed for the various components of the power train, the specifications of which were completely out of the scope of existing electric system in aviation. In a first step, this first design was generally performed with conservative technology assumption, which already allowed to go beyond the state of the art of electric machines and power electronics. The obtained performances could also be compared to performances projections to 2035 from the literature and experts’ judgement, evidencing performance gaps.
Preliminary findings on the potential of hybrid propulsion tend to show that aggressive technologies are required to bring an actual benefit compared to conventional propulsion. Short and Medium Range application is clearly longer term as it requires a huge step on electric systems. In addition, no clear promising configuration could be yet identified. For regional aircraft, it seems that high technology assumptions for batteries and a reduced range are required if parallel hybridization is envisaged. An interesting configuration was however identified making a radically different use of hybridization and leading to significant benefit.
Although a last more detailed iteration is scheduled on the radical configurations, IMOTHEP already brought significant progress in the assessment of various typical hybrid architectures. These could be investigated with well-controlled and homogeneous technology assumptions and a clear reference baseline for comparison with conventional propulsion projected to 2035. In addition, design could be proposed for the various components of the power train, the specifications of which were completely out of the scope of existing electric system in aviation. In a first step, this first design was generally performed with conservative technology assumption, which already allowed to go beyond the state of the art of electric machines and power electronics. The obtained performances could also be compared to performances projections to 2035 from the literature and experts’ judgement, evidencing performance gaps.
Preliminary findings on the potential of hybrid propulsion tend to show that aggressive technologies are required to bring an actual benefit compared to conventional propulsion. Short and Medium Range application is clearly longer term as it requires a huge step on electric systems. In addition, no clear promising configuration could be yet identified. For regional aircraft, it seems that high technology assumptions for batteries and a reduced range are required if parallel hybridization is envisaged. An interesting configuration was however identified making a radically different use of hybridization and leading to significant benefit.