Periodic Reporting for period 1 - C-ALM AOHE (Compact - Additive Layer Manufactured Air Oil Heat Exchanger) Reporting period: 2019-05-01 to 2020-10-31 Summary of the context and overall objectives of the project ObjectivesThe Compact - Additive Layer Manufactured Air Oil Heat Exchanger (C-ALM AOHE) project will design, develop, manufacture and test a compact air-oil heat exchanger for next generation geared VHBR/UHBR turbofan engines. It will deliver a fully validated air-oil heat exchanger to TRL6, MCRL4 and MRL6 with a heat load of 80kW and a dry weight of significantly less than 10kg that can directly flow into follow on flight demonstrator and NPI programmes.ContextAdvanced, high efficiency thermal management is an enabling technology for the next generation of VHBR/UHBR (Very- and Ultra-High Bypass Ratio) aero engines. These new engine architectures will incorporate a power gearbox to drive the fan, generating additional heat load, and will improve specific heat consumption, reducing the fuel available as a heat sink. C-ALM AOHE will deliver the step-change air-oil heat exchanger technology required to manage the thermal load of VHBR/UHBR engines with the over-arching goal of the project being to position Europe to be the world‘s number one in the technology and sales of gas turbine aero engine air-oil heat exchangers; a market segment that is forecast to be worth more than €1.5 bn over the next twenty years, with a higher growth rate than average for aerospace.The advent of Additive Layer Manufacture (ALM) in aerospace allows for new, innovative, highly complex heat exchanger topologies and geometries to be manufactured. ALM aluminium capability has accelerated over recent years with significant advances including build chamber size, thin wall manufacturing capability, powder removal and cleaning techniques, internal surface finish and the “design for ALM” capabilities. The consortium believes that ALM aluminium capability has now developed to a point where a robust programme for the next three years could fully prove the technology to TRL6, MCRL4 and MRL6 such that it could then move into a flight test demonstrator programme.The C-ALM AOHE project contributes to meeting the overall objectives defined for the Clean Sky 2 LPA Platform 1.5 Work Package ―Applied Technologies for Enhanced Aircraft Performance “Development of technologies which enable the physical integration of large-sized, ultra-efficient turbofan engines to the wing in a symbiotic manner such that the overall performance benefit of the whole configuration (wing/engine) is maximised”. By delivering a 0.5X reduction in volume per kW of heat transferred, and by delivering the capability for conformal shaping of the heat exchanger, the C-ALM-AOHE project will enable the AOHE to be moved off the engine fan case and onto the engine core. This is an enabling technology for slim-line nacelles that are required to enable an acceptable outer diameter of the podded VHBR/UHBR engines for integration with the wing.ApproachALM opens up the heat exchanger design space by enabling the manufacture of complex structures that could not previously be built with any conventional manufacturing process. However, it is critical that these new complex structures are developed to not only have step change thermal, pressure loss and air side mass flow performance; but also must have the mechanical integrity to meet all life requirements and the requisite unit cost and through life cycle costs to make sound business cases for both supplier and customer.The ALM technology selected for this project is laser powder bed fusion (L-PBF). L-PBF ALM technology is not currently proven to MCRL4 for the manufacture of aerospace ALM components thus this capability will be developed during the project.The C-ALM AOHE project will focus on aluminium alloy as the material for the manufacture of the design based on the requirements related to heat transfer, mass efficiency, cost and a maximum surrounding air temperature of 220 °C. The route to market for the C-ALM AOHE project technology will be via MAL, part of Meggitt Plc, a global aerospace engineering and manufacturing group that currently provides heat exchangers to leading civil and defence engine programmes. TWI will exploit its C-ALM AOHE output through further research at TWI that will build on the aluminium L-PBF ALM technology and manufacturing process capability. TWI is a membership based research organisation and as such is ideally placed to further exploit and disseminate its C-ALM AOHE research with its members for wider applications beyond the aerospace sector. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far The first steps in the project were collaboration between Meggitt’s engineers and TWI’s ALM experts to fully understand the design freedom offered by ALM in order to harness the benefits in a novel design of AOHE. A number of varied novel AOHE concepts were then generated and evaluated, considering performance and manufacture cost, resulting in one being selected to be developed into a real AOHE design during this project. A mathematical thermal model was developed based on Meggitt’s long experience in heat exchanger technology, allowing the selected concept to be refined into a design to meet the Topic Manager’s specification. A patent application has been submitted for this design. The complex geometric design has been rigorously explored and several iterations of the fluid flow channels have been simulated using computational fluid dynamics (CFD), and validated by physical testing of subscale parts. An AOHE concept demonstrator unit has been designed to prove out the design’s thermal and structural performance. The build and test of this part will provide evidence for achieving TRL4 and MCRL3, and performance data will allow full validation of the thermal modelling and CFD.The aluminium alloy AlSi10Mg was selected as the material for the novel AOHE, since its material properties meet the project specification especially with regard to operating temperature. Following procurement the powder was fully characterised. The development of appropriate L-PBF parameters to achieve the required density and geometry for thick and thin material sections was completed though a detailed manufacturing study. For the L-PBF method of additive manufacture, the precise set of laser parameters influences the mechanical properties of the material. A programme of material characterisation with over 150 test points has been undertaken to produce a comprehensive Materials Datasheet for AlSi10Mg, including data across the operating temperature range of the AOHE in a VHBR/UHBR engine application. The complex geometry of the novel AOHE design is pushing the boundaries of the existing L-PBF technology requiring significant innovation in the laser scan strategy, exploiting TWI’s expertise in this area. Meeting this technical challenge has involved manufacture of iterations of subscale models of elements of the novel design concept for evaluation using XCT scanning and physical test. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) The novel AOHE is currently predicted to meet some of the performance attribute targets, and with the understanding gained by the concept demonstrator testing it is expected that a design to fully meet all the project targets will be achieved within the project. A key benefit of the novel concept is the lightweight structure, resulting in a lighter unit for engine installation. Meggitt logo TWI logo
