Skip to main content
European Commission logo print header

ENABLing cryogEnic Hydrogen based CO2 free air transport (ENABLEH2)

Periodic Reporting for period 2 - ENABLEH2 (ENABLing cryogEnic Hydrogen based CO2 free air transport (ENABLEH2))

Période du rapport: 2020-03-01 au 2021-08-31

Liquid Hydrogen (LH2) has the potential to completely decarbonise civil aviation. Flightpath 2050 very ambitiously targets 75% CO2 and 90% NOx emissions reductions, relative to year 2000. It will be extremely challenging to meet these targets with carbon based fuels, despite large research efforts on disruptive airframe and propulsion technologies, even when coupled with improved asset and lifecycle management procedures. Even if we were able to meet these targets, this would not be sufficient for a fully sustainable future for civil aviation, particularly considering the rate at which other sectors are decarbonising. The unique environmental benefits of LH2 for aviation must exploited, with the transition starting as soon as possible. ENABLEH2 is providing thought leadership through revitalising enthusiasm in LH2 research for civil aviation by maturing key technologies to achieve zero mission-level CO2 and ultra-low NOx emissions, with long term safety and sustainability.

Key technologies being studied are:

1. H2 Micromix combustion

Jet A-1 has relatively narrow combustion flammability limits which presents several challenges for low NOx combustion technologies. H2 has much wider flammability limits enabling leaner (lower flame temperature) combustion. Additionally, the molecular diffusivity and high flame speed of H2 offer good mixing and lower residence times, therefore significant reductions in NOx are possible. Micromix (diffusion) combustion enables superior fuel and air mixing without the risks of auto-ignition and flashback associated with premixing. The improved mixing reduces local high flame temperature regions, leading to ultra-low NOx emissions. Within WP3, ultra-low NOx H2 Micromix combustion technology is being matured through a combination of numerical and experimental research comprising injector array, full annular combustor segment and altitude-relight studies.

2. Fuel system heat management

To exploit the formidable heat sink potential of LH2, to enable more-efficient disruptive propulsion technologies, WP2 is maturing technologies for compressor integrated cooling, intercooling and variable cooling concepts, fuel pumps, heat exchangers, turbines for expander cycles and cryogenic cooling for electric systems for turboelectric distributed propulsion. WP1 is maturing LH2 fuel tank design and integration.

In WP1, models are being developed to evaluate LH2-fuelled aircraft with respect to energy efficiency, emissions, life cycle CO2 and costs, for potential fuel price and emissions taxation scenarios. The benefits and economic viability of LH2 will be quantified relative to best-case scenario projections for Jet A-1, Biofuels and LNG. WP4 is generating best-practice safety guidelines for LH2 at aircraft, airport and operational level. WP5 will deliver comprehensive roadmaps for the introduction of LH2.

To maximise the technical rigour and impact of the project, ENABLEH2 also has a highly active Industry Advisory Board (IAB). The IAB comprises key civil aviation stakeholders including aircraft and propulsion system OEMs, airlines, energy and industry organisations. IAB members include: Abengoa, ACI, Airbus, Air Liquide, ATI (FlyZero), Clean Sky 2 JU, Dassault Aviation, EASA, easyJet, Gexcon, IAG, HyEnergy, IATA, ICAO, IMI, Infosys, Lufthansa Technik, MHPS, MOOG, MTU, Reaction Engines, Rolls-Royce, Siemens and Total
Key achievements:

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 and modelled (one “more conventional” and one “maximum synergy” configuration each for a typical short-medium range and long-range mission). Assessments of reference aircraft utilising Jet A-1, biofuels and LNG are also complete.

WP2 has developed tools for the conceptual design, performance and optimisation of fuel system components. Commissioning of the low-pressure compressor facility and safety tests are underway. The core-exhaust rig assembly is complete, pending the assembly of a new turbine rear structure and module. Numerical aerothermal performance analyses of the interconnecting ducts and turbine rear structure have been performed.

Within WP3, comprehensive CFD-based studies (comprising design space exploration, emissions and thermoacoustic assessments) have been completed. These models will be validated using the experimental data. The assembly of the Phase 1 (small-scale injector array) H2 combustion rig is complete. The experimental campaign is underway. The design of the Phase 2 (annular combustor segment) rig is being finalised. Modifications to adapt the Phase 1 test section for the Phase 3 (altitude relight) studies have been identified.

In WP4 a review of aeronautic and H2 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 to determine flammability limits, minimum ignition energy and burning velocity over a range of temperatures and pressures. The safety of LH2 at airports, has been assessed via a Preliminary Hazard Analysis workshop held at Heathrow. To cater for both early introduction and significant fleet penetration of H2 aircraft, two scenarios have been developed with significantly varying infrastructural and operational requirements.

In WP5, a dedicated project website and tool have been set up to engage with the IAB. Twelve key technology research strands have been identified for the introduction of LH2 for civil aviation as part of a preliminary roadmapping exercise. Feedback from partners and IAB members is being sought to inform and deliver the final roadmap.
Key deliverables expected by the end of the project:

1. Compressor integrated cooling, intercooling and variable cooling (TRL 4)
2. Fuel tank and fuel system model (TRL 2)
3. Ultra-low NOx annular micromix combustor segment design (TRL 3/4)
4. Verified aircraft, propulsion system, emissions and life cycle numerical models (TRL 2)
5. Quantified Technoeconomic Environmental Risk Assessments (TERA) at mission level
6. A comprehensive safety audit, characterizing and mitigating hazards to support integration and acceptance of LH2 at aircraft, airport and operational level
7. Life cycle costs and CO2 emissions relative to best case scenario projections for Jet-A1, bio-fuels and LNG for different fuel price and emissions taxation scenarios
8. Roadmaps for maturing the technologies to TRL 6 by 2030 – 2035 and also for the gradual introduction of LH2 for civil aviation including airport infrastructure development

Key impact indicators to date:

ENABLEH2 is developing technologies which will make a substantial contribution to meeting the ambitious environmental targets for civil aviation. By complementing research in other sectors the project will support transition towards a H2 economy. ENABLEH2 is revitalising enthusiasm in LH2 for civil aviation by engaging with key aviation stakeholders, alleviating public perception safety concerns and demonstrating the long-term environmental and economic case for LH2.
ENABLEH2 partners have participated in numerous conferences/workshops/outreach initiatives. ENABLEH2 has also featured in major reports, EU brochures, press articles, videos and more. Details are available on the ENABLEH2 project website.
ENABLEH2 - LSBU H2 Safety Experimental Refrigerated Cabinet and Pressure Vessel
ENABLEH2 - Maximum Synergy LH2 Aircraft Concept (LR)
ENABLEH2 - Chalmers Fuel System Heat Management Rig
ENABLEH2 - CU Phase 1 H2 Combustion Rig
ENABLEH2 - CU Low NOx Hydrogen Combustion Facility
ENABLEH2 - Maximum Synergy LH2 Aircraft Concept (SMR).jpg
ENABLEH2 - Lower Risk LH2 Aircraft (SMR)
ENABLEH2 - Lower Risk LH2 Aircraft (LR)
ENABLEH2 - CU Visualisation of H2 Micromix Flames Through Optical Access Windows