Progress in WP2
Fuel System Heat Management
The density of liquid hydrogen (LH2), at the normal boiling point, is two times higher than that of highly compressed gaseous hydrogen. This makes LH2 the prime candidate for hydrogen storage in aviation. However, LH2 needs to be stored at cryogenic temperatures (-253 C) and therefore requires adequate tank and fuel line insulation, as well as the development of a dedicated heat management system to provide the fuel to the combustor with an adequate temperature. Nevertheless, the cooling capacity of cryogenic LH2 can be explored by more compact heat exchanger technology that can be easily integrated within the engine core.
Work-package 2 is focused around the development of the hydrogen fuel distribution and heat management systems. The main objectives of WP2 target the optimization of the entire system and the development of novel compact heat exchanger technology to TRL4. More specifically:
- Perform experimental work on integrated heat exchangers for synergistic components (synergistic compressor heat rejection and synergistic core exhaust heat recovery) to TRL4 (heat exchangers with integrated aerodynamic function).
- Set up conceptual design tools for the heat management subsystems based on obtained experimental results and existing correlations and provide a heat management system model to be integrated into top-level optimization.
- Develop safety-driven metrics and screening methodologies to support down-selection of heat management systems.
- Develop the down-selected heat management system to TRL2 and modelling to WP1 for top-level optimization.
Progress and significant results
Chalmers in-house propulsion system simulation environment GESTPAN (GEneral Stationary and Transient Propulsion ANalysis) is adapted to simulate the performance of cryogenically fuelled gas turbine engines. The tools required to design the propulsion system and heat management are in place. The methods were developed, or adapted, specifically for LH2 applications for the following components: pre-cooler; intercooler; expander cycle; turbine cooling; recuperation; combustion; fuel distribution and related sub-systems; gas properties modelling for combustion products. Figure 1 shows possible points for core heat rejection to the fuel.
Dedicated templates for LH2 engine models were developed to support the top-level assessment in WP1 and the conceptual design studies of WP2. The engine templates include all the technology and models developed at Chalmers. Switching between different architectures is achieved with component activation flags, supported by the heat-management-system control algorithm. The model is generic and may be used for JetA-1, a biofuel, LNG and LH2.
stage Low-pressure compressor
A vertically mounted low-speed 2.5 stage compressor facility is under construction at Chalmers University of Technology, laboratory of fluid and thermal sciences, see Figure 2. The rig is designed to operate continuously at rotor mid-span chord Reynold number up to 600,000, which is representative of a large-size future geared turbofan engine. The facility includes a coolant distribution system for the compressor outlet-guide-vane and strut-vane to support heat transfer measurements. Detailed aerothermal studies at TRL4 will be conducted to calibrate in-house design methods for radical core integrated heat exchangers. The facility is driven by a 147kW electric drive at a nominal speed of 1920 RPM. Traverse access is included in two 18-degree sectors for all the rotor-stator interfaces. At the upstream plane of the compressor outlet-guide-vane, four independent access traverse systems are included for a 360-degree access. Downstream, an ABB robot arm with a U-shaped probe mount provides full volume probing access in the exit compressor duct.
T. Grönstedt, H. Abedi, I. Jonsson, A. Rolt and V. Sethi. “Integration of cryogenic hydrogen and propulsion system for commercial aviation”. Presented at 9th EASN Conference on Innovation in Aviation and Space. 3rd – 6th September 2019, Athens Greece.
I. Jonsson, C. Xisto, H. Abedi, T. Grönstedt and M. Lejon. “Feasibility study of a radical vane-integrated heat exchanger for turbofan engine applications”. ASME Turbo Expo 2020, Turbomachinery Technical Conference and Exposition, 21-25 September 2020.
C. Xisto, I. Jonsson and T. Grönstedt. Development of fuel and heat management system for liquid hydrogen powered aircraft. To be presented at 10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens, 2-4 September 2020.
WP1 has reviewed developments in H2 production and infrastructure and made projections for the long-term costs of alternative fuels. Four LH2 aircraft configurations have been selected for detailed studies (one “more conventional” and one “maximum synergy” configuration each for a typical short-medium range and long range mission). These concepts were down-selected from several aircraft configurations via a rigorous quality function deployment exercise. Assessments of reference aircraft utilising Jet A-1, biofuels and LNG is almost complete.
Within WP3, comprehensive CFD-based studies (comprising design space exploration, emissions and thermoacoustic assessments) have been completed and have highlighted limitations, uncertainties and significant discrepancies between H2 and air mixing and combustion models of 3 state-of-the-art commercial combustion CFD codes. These models will be further evaluated, validated and calibrated based on the results obtained from the experiments. The design and commissioning of the rigs are underway.
In WP4 a review of aeronautic and H2 industry safety synergies, conflicts and knowledge gaps, and preliminary hazard analyses of laboratory and aircraft systems has been completed. A safety management plan has been issued. Experimental studies are currently underway. The safety of LH2 at airports, has been assessed via a Preliminary Hazard Analysis workshop held at Heathrow.
As part of WP5, a dedicated project website and community management tool have been set up to engage with the IAB members in a formal capacity. Twelve key technology research strands have been identified for the introduction of LH2 for civil aviation as part of a preliminary roadmapping exercise.