Tech Insider / AVL RACETECH H 2 ICE ydrogen may not be flavor of the month for car makers, either in fuel cell or ICE form. Despite this, one area in which it will almost certainly play a key role in decarbonization is racing. The heat of competition is where AVL, best known for its test benches, measurement devices, simulation tools and a long history of engine development, hopes the engine shown here will come into play. There is considerable discussion in the upper echelons of motorsport around the use of hydrogen; an H₂ class is due at Le Mans in 2027, accommodating both fuel cell and ICE, while Extreme H, an off-road race series, will arrive in 2025. However, it is the lower leagues that AVL Racetech, the motorsport arm of the company, is targeting with this effort. Specifically, classes based around the TCR rule set – touring cars based on roadgoing machines with 2.0-liter, production-based engines. Cost is a major driver in this category but, sooner or later, the current ICE engines could be outlawed in some regions. AVL feels H₂ can provide the answer: all the emotion of ICE without the emissions. It was against this backdrop that the performance targets for the engine were set: a power output of 300kW, 500Nm of torque, at a reasonable cost. H COMPRESSED SCHEDULE AVL’s Rene Heindl, senior development engineer for spark ignition engines, takes up the story: “The project has been completed in roughly one year. It was a real challenge, 300kW out of a two-liter engine, which is a huge output for a hydrogen engine, especially with the somewhat unconventional approach we have chosen – stoichiometric combustion of hydrogen.” The engine is based around an existing production unit, with many of the mechanical components remaining stock, though there is some mixing and matching of components from the same engine family. In addition to simulation-based selection and replacement of some standard parts with motorsport-specific components, it is on the combustion system that AVL has concentrated its efforts, using direct injection of gaseous H 2 coupled with a port-based water injection system. While many H 2 engines are developed with lean running in mind, AVL’s engine runs at a stoichiometric ratio to maximize efficiency. This choice was made in order to hit the 300kW power target without the need for expensive, bespoke turbocharging technology. The air mass needed to achieve the target output with lean H 2 combustion would have required a much greater mass airflow than could be obtained with a traditional, single-stage turbocharger. “You would need to redesign the entire engine to push the air needed through it,” says Heindl. “From the very beginning, we said we did not want any exotic turbocharging technology, which ruled out multistage systems and electrified turbos.” Though using a stoichiometric ratio means it is possible to achieve similar levels of responsiveness from a hydrogen engine compared with gasoline – a very important consideration for racing applications – it does require what Heindl calls “moderation” of the You need to calm down the combustion so that you do not heavily pre-ignite all the time” 1 combustion. “You need to calm down the combustion so that you do not heavily pre-ignite all the time.” Enter the water injection system. The addition of water to the inlet charge helps to reduce the speed and temperature of combustion to manageable levels. EGR dilution could also be used to achieve this calming effect, but Heindl explains this approach is not appropriate for a racing application: “The advantage of water is that it can be done almost cycle by cycle and you can be very quick regulating the combustion. This is not possible with an EGR system; you can’t get the response.” The water injection system relies on eight injectors, two per cylinder, with the water playing a dual role: moderating combustion in the cylinder while also 1 & 2. CALMING WATERS Two sets of water injectors are employed in order to precisely meter the correct amount to ensure combustion is kept under control 3 12 www.automotivepowertraintechnologyinternational.com / March 2024