Porsche, a German automobile manufacturer, is prospecting a high-performance hydrogen combustion for passenger vehicles, recently completing a virtual test of a hydrogen-powered engine. Its engineering examined hydrogen as a potential alternative to the traditional use of fuels or synthetic fuels for powering combustion engines since various powertrain technology are being closely developed for enhancing future vehicles.
Although efforts are being made for hydrogen engines worldwide, this is usually conducted for low-output commercial vehicles with only around 50 kW per litre of displacement.
“For the passenger car sector, this is insufficient,” says Vincenzo Bevilacqua, Senior Expert Engine Simulation at Porsche Engineering. “We have therefore developed a hydrogen combustion engine that aims to match the power and torque of current high-performance gasoline engines as a concept study. At the same time, we also had the objective of achieving low fuel consumption and keeping emissions at the same level as ambient air. The starting point for our study was an existing 4.4-litre eight-cylinder gasoline engine – or rather, its digital data set, since we conducted the entire study virtually using engine performance simulations.”
Higher compression ratio, combustion adapted to hydrogen, and a new turbocharging system are part of the engine model modification. Bevilacqua explained, “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.” Porsche Engineering examined four alternatives, particularly turbocharging concepts, to resolve the discrepancies that conventional turbochargers cannot fix effectively.
“In the benchmark studies, each turbocharging system showed specific advantages and disadvantages. The choice of the right concept is therefore highly dependent on the requirements profile of the hydrogen engine in question,” says Bevilacqua.
The automaker used the powertrain to simulate a luxury car with a relatively high total weight of 2,650 kg driving around the Nurburgring Nordschleife, finishing the loop in eight minutes and 20.2 seconds. Porsche modified their 4.4-liter V8 as a starting point for the study to tolerate a higher compression ratio and combustion. The virtual test through a “digital twin” revealed that the car reached 162 mph (261 kilometers per hour).
“As it turned out, the nitrogen oxide emissions are well below the limits set by the Euro 7 standard currently under discussion and are close to zero over the entire engine map,” reports Matthias Böger, Specialist Engineer Engine Simulation at Porsche Engineering.
Böger compared the emissions test findings through the Air Quality Index, a tool used by government authorities and other organizations to evaluate the severity of air pollution. Generally, good air quality is defined as a nitrogen oxide concentration of about 40 micrograms per cubic meter. He added, “The hydrogen engine’s emissions are below this limit. Operating it therefore has no significant impact on the environment.”
The study helped Porsche learn valuable insights about high-performance hydrogen engines. According to Porsche’s calculation, the engine might adhere to Euro 7 emissions regulations. The hydrogen engine would not require an exhaust gas after-treatment system, although it is more complicated and expensive than a conventional petrol engine. With these insights, Porsche will be prepared to “efficiently handle future customer projects.”
