Various drive options such as hybrid systems, electrical drives and effective combustion engines are presently being established in parallel for future lorries. As an option to standard fuels or artificial fuels (eFuels), hydrogen can likewise be thought about for usage in combustion engines, which was the topic of this research study and was examined by Porsche Engineering.
High efficiency hydrogen engine for automobile
Hydrogen engines are presently being utilized all over the world, however mainly for business automobiles with an extremely low output of around 50 kW per liter of displacement. “That’s inadequate for the automobile market. That’s why we established a hydrogen combustion engine as research study, which ought to supply power and torque at the level of present high-performance gasoline engines. At the exact same time, our objective was to accomplish using less fuel and keep emissions at ambient air level,” states Vincenzo Bevilacqua, engine simulation specialist at Porsche Engineering. “The beginning point for our examination was the 4.4-liter eight-cylinder gasoline engine– or to put it much better: its digital information set, since we did the whole research study utilizing simulation.”
Changes to the engine design consisted of, to name a few things, greater compression and customized combustion, however above all a brand-new turbocharging system. “For hydrogen to burn easily, turbochargers need to provide nearly two times as much air as in gasoline engines. On the other hand, due to the low temperature level of the exhaust gas, there is an absence of energy to drive them on the exhaust side,” discusses Bevilacqua. This confusion can not be fixed by standard turbochargers. Porsche Engineering has actually checked out 4 alternative principles, primarily with superchargers, some of which come from motorsport.
All systems consist of a number of electrically helped turbochargers, in some cases with extra control flaps in the air system or mechanical compressors. “In benchmark tests, each charging system revealed particular benefits and drawbacks. The option of the best principle for that reason depends quite on the need profile of the particular hydrogen engine,” states Bevilacqua. For the present engine research study, the advancement group selected a system of turbo and so-called reciprocating compressors. Its unique style function is a coaxial plan of 2 compressor phases, which are driven by a turbine or an electrical supporting motor through a common shaft. The procedure air streams through the very first compressor, it is fed into the intercooler and after that pressurized in the 2nd phase.
With an output of around 440 kW, the hydrogen engine is comparable to a natural gasoline engine. In order to much better define the cars and truck’s efficiency, Porsche Engineering checked the high-end class memory vehicle with an optimum weight of 2,650 kg on the Nürburgring-Nordschleife– nearly precisely: the cars and truck was made with the assistance of a so-called digital twin, i.e. a picture of the genuine vehicle on the computer system. With a lap time of 8 minutes 20 seconds, the automobile revealed excellent prospective in regards to driving characteristics. Due to its chemical structure, the combustion of hydrogen does not produce hydrocarbons or carbon monoxide gas, and natural particles do not contribute either. The professionals at Porsche Engineering for that reason concentrated on nitrogen oxides when increasing emissions from the hydrogen engine. In numerous optimization loops, they limited the engine’s operating technique for pure combustion. Their method: to keep the raw air level low with the aid of really lean and for that reason cooler combustion, so that an extra exhaust gas treatment system can be offered.
” As revealed, nitrogen oxide emissions are listed below the presently gone over limitation worths of the Euro 7 basic and are practically no over the whole speed variety,” reports Matthias Böger, engine simulation advancement engineer at Porsche Engineering. In order to much better categorize the outcomes of emissions tests, he compares them with the so-called air quality index. This is utilized as a standard for federal government companies and other organizations to evaluate the level of air contamination. In basic, a concentration of as much as 40 micrograms of nitrogen oxide per cubic meter is comparable to excellent air quality. “Emissions from a hydrogen engine are listed below this limitation. Its operation for that reason does not have a substantial influence on the environment,” states Böger.
Emissions at ambient air level
In addition to quantifiable emissions, the hydrogen engine provides high effectiveness in the WLTP test cycle and in customer-related usage cycles due to lean combustion. “Therefore we have actually totally accomplished the objective of the task we set for ourselves, the advancement of a tidy, cost-effective and stylish hydrogen engine,” sums up Bevilacqua. The expenses of a hydrogen automobile in series production are equivalent to those of a gasoline engine. The turbocharger system and other mechanical parts of the hydrogen engine are more intricate and for that reason more costly, the exhaust gas treatment needed for Euro 7 engines is kept.
The Porsche Engineering Team had the ability to perform all the tests thoroughly and for that reason really effectively. The basis was an end-to-end simulation procedure chain, with comprehensive experience in modeling and computation. “It took us just 6 months from the preliminary concept to the end of the research study,” states Bevilacqua. “This likewise consisted of basic work such as the advancement of brand-new computational designs that consider the various chemical and physical residential or commercial properties of hydrogen compared to gasoline.”
Use advantages of as much as 5 percent
The hydrogen engine most likely will not enter into series production in its existing type, however that wasn’t the objective of the task at all. Rather, the focus was on checking out the technical expediency of alternative storage and the growth of existing engineering tools. “The research study offered us important insights into the advancement of high-performance hydrogen engines and we included hydrogen-specific designs and strategies to our advancement pipeline,” discusses Bevilacqua. “With this understanding, we are prepared to effectively manage future client tasks.”
At a look: a simulated lap on the Nordschleife
Maximum speed: 261 km/h
Hours: 8: 20: 20 minutes
Simulated engine power: 440 kW
details
The text was very first released in Porsche Engineering Magazine, problem 2/2022
Author: Richard Backhaus
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