Tech Insider / AVL RACETECH H 2 ICE 1 Similarly, the spark plugs must be specially designed, and this is an area where AVL is reluctant to divulge too much detail. However, Heindl reveals, “You cannot just pick the coldest plug, as you would do with a gasoline engine, if you expect high thermal loads. That’s not enough for hydrogen.” Another challenge for AVL was finding hydrogen injectors that were up to the task. Though several manufacturers have prototype units on the market, Heindl points out that these are designed for heavy-duty engines and thus are not suitable for packaging within a compact IL4. “Everything available for passenger car engines are prototypes with insufficient mass flow, so we have contacted a supplier for development of injectors with a high enough mass flow for our needs. I don’t think that these currently exist anywhere other than on our engine,” says Heindl. These injectors need to be able to provide the required flow to the cylinder but also currently still need to operate with the aid of external lubrication, which would normally be provided by the lubricating action of gasoline or diesel fuel. “Hydrogen has no lubrication ability. Even CNG carries a bit of oil because it comes from the [gas] grid and goes through compressor stations,” Heindl outlines, adding, “But hydrogen comes from the chemical industry and is completely pure. That is why the injectors have a dedicated lubrication system, but the suppliers are working to get rid of that need because bringing oil into the combustion chamber creates the perfect source for pre-ignition.” Similarly, to ensure long-term engine durability, developments are needed, for example, to the valve seats and valve materials, as well as the piston-to-bore interface, to operate in the stressful environment of even moderated hydrogen combustion. “That is a mechanical challenge that needs to be met if you want to go to the track or road. It needs to be addressed in conjunction with parts manufacturers. When we tested our engine, we definitely saw some wear on, for example, the valves. They endured the testing phase but for longer-term reliability it needs addressing,” summarizes Heindl. 2 GAS DYNAMICS Of course, the injection event is very different with gas from how it is with a liquid fuel injected in a spray. This means the dynamics within the combustion chamber are also unique, says Heindl. “Due to the low density of hydrogen, the injectors need a very big opening, with a large cross-section to deliver the correct amount of energy to the combustion chamber. That means they have to be outward opening, unlike a gasoline injector, where you have multiple holes and can target your injection and adapt it to the aerodynamics of the incoming air.” The dynamics of the incoming air have a notable, but not dominating, effect on the formation of the gas cone from the injector. According to Heindl, although the injector design would lead one to expect a broad cone pattern, there is a Coand˘ a effect within the jet itself and between the jet and the combustion chamber surrounding, meaning this cone is never fully formed. “This is very different from a liquid fuel and the gas jet influences the charge motion to a much greater degree than conventional liquid fuel jets,” says Heindl. “So the main influence in the combustion chamber on charge motion and turbulence generation is that high-pressure gas jet and its side effects.” Extensive CFD simulation, combined with AVL’s existing experience with H₂ ICEs, was used to find an injector location that best mitigated these effects and gave the best mixture preparation. ˘ EFFECT 1. COANDA The high-speed gas jet from the injector has a major role to play in the charge motion within the combustion chamber of the engine 2. LOW EMISSIONS There is great potential for green hydrogen to cut the carbon footprint of motorsport 3. POWERHOUSE Graphs showing the BMEP, efficiency, excess air ratio and power outputs of AVL’s H 2 engine 4. H 2 SPECIFIC AVL has invested heaviliy in updating its test bench facilities for use with hydrogen fuel 14 www.automotivepowertraintechnologyinternational.com / March 2024