Porsche has engaged in a virtual study, using energy performance simulations, for a hydrogen combustion engine and reported back with encouraging results.
On 18 August, it revealed that Porsche Engineering had virtually tested a hydrogen engine on the Nürburgring Nordschleife using a digital twin. While work is ongoing worldwide on hydrogen engines, this is mainly being done for commercial vehicles, with a relatively low specific output of around 50kW per litre of displacement. This would be insufficient for the passenger car sector, with Porsche therefore setting out to develop a hydrogen combustion engine that can match the power and torque of the current high-performing petrol engines as a concept study. It also aimed to achieve low fuel consumption and ensure emissions are kept at the same level as ambient air.
Using an existing 4.4-litre eight-cylinder petrol engine as a starting point, it modified it with a higher compression ratio and combustion adapted to hydrogen, as well as incorporating a new turbocharging system. Explaining the reasoning for this, Vincenzo Bevilacqua, Porsche Engineering’s Senior Expert in Engine Simulation, said: “For clean combustion of hydrogen, the turbochargers have to, on the one hand, provide around twice as much air mass as they do in gasoline engines. On the other hand, however, the lower exhaust gas temperatures result in a lack of energy for their propulsion on the exhaust side.” This is something conventional turbochargers cannot do.
The eventual concept for Porsche’s hydrogen engine, therefore, had an output of around 440kW, making it on par with the original petrol unit. It then tested it virtually in a luxury-segment reference vehicle with a relatively high total weight (2,650kg) around Nürburgring Nordschleife. It recorded a lap time of 8 minutes, 20 seconds, a maximum speed of 261km/h and demonstrated high potential when it comes to driving dynamics.
To optimise emissions by the hydrogen engine, Porsche Engineering’s focus was on nitrogen oxides – neither hydrocarbons or carbon monoxide are released during hydrogen combustion, with particulates not playing a role either. The engine’s operating strategy went through extensive optimisation rounds to ensure the cleanest possible combustion, mainly through the means of extremely lean and colder combustion. This made it possible to dispense with an exhaust aftertreatment system.
According to Matthias Böger, Specialist Engineer Engine Simulation at Porsche Engineering, the nitrogen oxide emissions were “well below” the limits set by the Euro 7 standard and close to zero across the entire engine map. In short, operating the hydrogen engine was found to have no significant impact on the environment.
It was also found to offer high efficiency in the WLTP (Worldwide Harmonized Light Vehicles Test Procedure) measurement cycle and customer-relevant cycles through its lean combustion, meaning Porsche was able to fulfil its safe-imposed project goal of “the development of a clean, economical and sporty hydrogen engine, across the board”. It added that the cost of a hydrogen powertrain in series production could be comparable to that of a gasoline engine, with the lack of a need for an exhaust gas aftertreatment offsetting the more complex number of mechanical components and turbocharger system that would be required.
The hydrogen engine will, in all likelihood, not enter production in its current form, though the main goal of the project was to examine the technical potential of this alternative drive technology and expand capabilities of existing engineering tools. Porsche has been able to gain valuable insights when it comes to developing high-performance hydrogen engines, as well as add models and methods that are specifically for hydrogen to its virtual simulation methodology.
