Periodic Reporting for period 3 - UTOPEA (UHBR Engine Technology for aircraft OPeration, Emissions and economic Assessments)
Reporting period: 2022-11-01 to 2023-11-30
To achieve Flightpath 2050 targets, the nearer-term aviation technology developments being targeted by Clean Sky2 are largely aimed at improving the overall efficiency of the integrated airframe and propulsion system, and consequently a reduction in fuel consumption and the aviation industry’s overall environmental footprint through reduced emissions. Consequently, a number of key design modifications on the aero gas turbine are being researched and pursued. Some of these include:
‒ Achieving higher propulsive efficiency through very low specific thrust engines i.e. significantly higher bypass ratios.
‒ Advanced materials for the hot section to enable higher core temperatures
‒ Utilisation of alternative fuels to reduce environmental emissions
The design transition to significantly higher BPRs, as in Ultra High Bypass Ratio (UHBR) turbofans, accompanied with the utilisation of ceramic matrix composite (CMC) blades and alternatives fuels, while promising exceptional benefits, will be a transition from traditional aeronautical propulsion system design, engineering and asset utilisation. The implications of these design improvements need to be better understood in the context of possible design limitations, operational feasibility and economic viability. Based on this, and in the context of UHBR engines, the overall objectives of the project include
‒ Establishing a methodology to predict operability challenges at the preliminary design phase and further identify and assess issues related to compressor stability
‒ Assessment of the impact of use of new materials such as Ceramic Matrix Composites (CMC) for hot section components
‒ Assessment of the potential of alternative fuels and corresponding combustion technologies to reduce NOx emissions
Based on these objectives the work in the project has been divided between three distinct but inter-connected Research Themes (RTs)
‒ Achieving higher propulsive efficiency through very low specific thrust engines i.e. significantly higher bypass ratios.
‒ Advanced materials for the hot section to enable higher core temperatures
‒ Utilisation of alternative fuels to reduce environmental emissions
The design transition to significantly higher BPRs, as in Ultra High Bypass Ratio (UHBR) turbofans, accompanied with the utilisation of ceramic matrix composite (CMC) blades and alternatives fuels, while promising exceptional benefits, will be a transition from traditional aeronautical propulsion system design, engineering and asset utilisation. The implications of these design improvements need to be better understood in the context of possible design limitations, operational feasibility and economic viability. Based on this, and in the context of UHBR engines, the overall objectives of the project include
‒ Establishing a methodology to predict operability challenges at the preliminary design phase and further identify and assess issues related to compressor stability
‒ Assessment of the impact of use of new materials such as Ceramic Matrix Composites (CMC) for hot section components
‒ Assessment of the potential of alternative fuels and corresponding combustion technologies to reduce NOx emissions
Based on these objectives the work in the project has been divided between three distinct but inter-connected Research Themes (RTs)
In the period under report the following tasks have been undertaken
RT 1 - Engine Impacts on Aircraft Operational Capabilities
Detailed Compressor Aerodynamic Design and Analysis (Task 1) : In the context of this task, an existing in-house code (C-BLADE) has been adapted and further developed to generate compressor performance characteristics for any user specified design. The code includes the ability to incorporate variable geometry and bleed schedules and estimate compressor weight. The code has been validated against public domain data and used to perform studies on compressor stability for different designs (e.g. loading magnitude and distribution).
RT 2- Engine Impacts on Aircraft Operational Capabilities
A detailed literature review on
‒ Ceramic Matrix Composites available for UHBR engines: This included a detailed technical review of all available CMCs for both stationary and rotating applications, and for both low and high temperatures , low and high pressure applications, and available materials in terms of their mechanical and thermal properties.
‒ Manufacturing processes for CMCs: This included classification and assessment of the manufacturing processes in terms of their manufacturing cost, reliability, repeatability, quality and flexibility using the well accepted manufacturing decision making attributes. The review also included the mapping of the processes to applications and potentially to engine components.
RT 3- Impact of Fuel Characteristics on Engine Design and Performance
‒ Adaptation of data from a performance model for a UHBR engine created in Research Theme 1(NTUA) to provide boundary conditions for combustor modelling.
‒ A detailed literature review on suitable emissions prediction models which included review of emissions prediction models/methods for LDI-PP aero engine combustion systems
‒ An overview of different methodologies for NOx emissions prediction (including correlation based, physics based reactor network (stirred-reactor) and CFD methods) with details of their relative advantages and drawbacks (for preliminary design and optimisation of advanced engine cycles)
‒ Development of an analytical reactor network model to assess emissions based on previous Cranfield in-house codes.
RT 1 - Engine Impacts on Aircraft Operational Capabilities
Detailed Compressor Aerodynamic Design and Analysis (Task 1) : In the context of this task, an existing in-house code (C-BLADE) has been adapted and further developed to generate compressor performance characteristics for any user specified design. The code includes the ability to incorporate variable geometry and bleed schedules and estimate compressor weight. The code has been validated against public domain data and used to perform studies on compressor stability for different designs (e.g. loading magnitude and distribution).
RT 2- Engine Impacts on Aircraft Operational Capabilities
A detailed literature review on
‒ Ceramic Matrix Composites available for UHBR engines: This included a detailed technical review of all available CMCs for both stationary and rotating applications, and for both low and high temperatures , low and high pressure applications, and available materials in terms of their mechanical and thermal properties.
‒ Manufacturing processes for CMCs: This included classification and assessment of the manufacturing processes in terms of their manufacturing cost, reliability, repeatability, quality and flexibility using the well accepted manufacturing decision making attributes. The review also included the mapping of the processes to applications and potentially to engine components.
RT 3- Impact of Fuel Characteristics on Engine Design and Performance
‒ Adaptation of data from a performance model for a UHBR engine created in Research Theme 1(NTUA) to provide boundary conditions for combustor modelling.
‒ A detailed literature review on suitable emissions prediction models which included review of emissions prediction models/methods for LDI-PP aero engine combustion systems
‒ An overview of different methodologies for NOx emissions prediction (including correlation based, physics based reactor network (stirred-reactor) and CFD methods) with details of their relative advantages and drawbacks (for preliminary design and optimisation of advanced engine cycles)
‒ Development of an analytical reactor network model to assess emissions based on previous Cranfield in-house codes.
The areas in which RT will make progress beyond the current state of the art and expected results are as follows:
RT 1: Engine Impacts on Aircraft Operational Capabilities
‒ Full integration of axial turbomachinery component aerodynamic design and analysis with thermodynamics at the same modelling level and within the same simulation platform
‒ Prediction of idle performance requirements and constraints during engine design
‒ More realistic fuel burn assessments of UHBR GTF engines through a multi-disciplinary approach considering simultaneous
‒ multi-disciplinary and multi-point engine design at high and low power conditions and limitations imposed by engine transient performance
RT 2: Engine Impacts on Aircraft Use and Economic Competitiveness
‒ Thorough assessment of CMC materials for hot engine applications
‒ Establish deterioration / degradation models for CMC materials for hot engine section environments
‒ Establish Remaining Useful Life (RUL) models for both static and rotating components
‒ Assessment of the impact of introducing CMCs in the hot section of engines on both the life cycle and operation of aircraft
RT 3: Impacts of fuel characteristics on engine design and performance
Higher fidelity studies of the hydrogen micromix and dual-fuel combustion systems
Hydrogen Micromix Combustion
‒ Utilising a validated design methodology for the combustion system, a bespoke Hydrogen Micromix Combustion system will be designed for the UHBR engine based on the combustors boundary conditions and geometry constraints. The design of other combustion system components such as combustor dome, liner cooling and casing will also be conducted.
‒ Dual Fuel Combustors
Within the UTOPEA a dual fuel combustor will also be conceptualised. One of the main tasks will be to assess the changes in engine performance, weight and emissions of the dual-fuel combustor compared to Jet-A1 LDI-PP combustion systems. An LDI_PP system designed for a kerosene fuelled aero engine will be used instead of a pure lean-premixed pre-vaporised system to reduce flashback and auto-ignition risks for safety considerations. Injector design changes will be investigated in order to incorporate gaseous fuel combustion and its influence on the combustor performance, operability and emissions will also be assessed via high-fidelity CFD analysis.
The key impacts of UTOPEA will include the following:
1. Develop knowledge and results that will have the potential to:
‒ Be commercially exploited as products or services by the industry
‒ Lay the foundation for further research and innovation (e.g. new knowledge, methods and data)
‒ Accelerate the development of technologies that have the potential to significantly reduce the impact of civil aviation on the environment
2. Integration and delivery of advanced numerical tools, methods and established best practices for the preliminary design of more efficient, more economically competitive and lower emissions UHBR engines specifically with respect to:
‒ Compressor stability, idle performance and mission fuel burn assessments for very low specific thrust (UHBR) engines
‒ Utilisation of advanced CMC materials and their impact on life and cost
‒ Preliminary designs for non-drop-in and dual-fuel low emissions combustion systems
RT 1: Engine Impacts on Aircraft Operational Capabilities
‒ Full integration of axial turbomachinery component aerodynamic design and analysis with thermodynamics at the same modelling level and within the same simulation platform
‒ Prediction of idle performance requirements and constraints during engine design
‒ More realistic fuel burn assessments of UHBR GTF engines through a multi-disciplinary approach considering simultaneous
‒ multi-disciplinary and multi-point engine design at high and low power conditions and limitations imposed by engine transient performance
RT 2: Engine Impacts on Aircraft Use and Economic Competitiveness
‒ Thorough assessment of CMC materials for hot engine applications
‒ Establish deterioration / degradation models for CMC materials for hot engine section environments
‒ Establish Remaining Useful Life (RUL) models for both static and rotating components
‒ Assessment of the impact of introducing CMCs in the hot section of engines on both the life cycle and operation of aircraft
RT 3: Impacts of fuel characteristics on engine design and performance
Higher fidelity studies of the hydrogen micromix and dual-fuel combustion systems
Hydrogen Micromix Combustion
‒ Utilising a validated design methodology for the combustion system, a bespoke Hydrogen Micromix Combustion system will be designed for the UHBR engine based on the combustors boundary conditions and geometry constraints. The design of other combustion system components such as combustor dome, liner cooling and casing will also be conducted.
‒ Dual Fuel Combustors
Within the UTOPEA a dual fuel combustor will also be conceptualised. One of the main tasks will be to assess the changes in engine performance, weight and emissions of the dual-fuel combustor compared to Jet-A1 LDI-PP combustion systems. An LDI_PP system designed for a kerosene fuelled aero engine will be used instead of a pure lean-premixed pre-vaporised system to reduce flashback and auto-ignition risks for safety considerations. Injector design changes will be investigated in order to incorporate gaseous fuel combustion and its influence on the combustor performance, operability and emissions will also be assessed via high-fidelity CFD analysis.
The key impacts of UTOPEA will include the following:
1. Develop knowledge and results that will have the potential to:
‒ Be commercially exploited as products or services by the industry
‒ Lay the foundation for further research and innovation (e.g. new knowledge, methods and data)
‒ Accelerate the development of technologies that have the potential to significantly reduce the impact of civil aviation on the environment
2. Integration and delivery of advanced numerical tools, methods and established best practices for the preliminary design of more efficient, more economically competitive and lower emissions UHBR engines specifically with respect to:
‒ Compressor stability, idle performance and mission fuel burn assessments for very low specific thrust (UHBR) engines
‒ Utilisation of advanced CMC materials and their impact on life and cost
‒ Preliminary designs for non-drop-in and dual-fuel low emissions combustion systems