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Hydrogen internal combustion engine

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The hydrogen combustion engine was once the hope of modern mobility. While there were notable successes on the engine side, energy efficiency and storage of liquid hydrogen posed problems. For Mercedes and BMW reason enough to put the project to rest. Mazda, however, continues to believe in success and research, albeit modest, the rotary engine. And Aston Martin hopes for fast lap times with hydrogen combustion.

Hydrogen internal combustion engine

The fuel of the future will one day be made from fruits, from apples, weeds or sawdust. That sounds like "Back to the Future," but was circulated by Henry Ford many years before Bob Gale's screenplay - in an interview with The New York Times [1]. Ford firmly believed it. After all, he originally designed his Ford Model T, built from 1908 to 1927, on the basis "that ethanol is the fuel of the future, which at the same time would give agriculture new impetus for growth." A misjudgment.
The research vehicle 230 HP with hydrogen drive from Daimler-Benz (© Daimler-Benz)
The petroleum-based fuels such as gasoline and diesel won the race. Especially because the price was low due to the high availability and because the company Standard Oil used its influence on politics. Although numerous alternative gasoline fuels have been tested over time, the dilemma remained with the emissions of the combustion of fuels. In particular, CO 2 , CO and nitrogen oxides were difficult for the engine developers in the stomach. Until hydrogen was discovered as the solution to nearly all emissions problems in the internal combustion engine. The project "Hydrogen Drive" was suddenly a federal matter in the early 1980s.


Although Mazda is still researching the hydrogen rotary engine, it is still on the backburner (© Mazda)




Alternative energy for the road

Now, the Federal Ministry of Research and Technology has generously promoted the hydrogen-burning engine. To the delight of Daimler-Benz. The carmaker participated in several demonstrations and research programs on alternative energy sources for road transport, which ran until the end of 1982. Based on the vehicle types Mercedes-Benz 230 TE and 280 TE tested the Stuttgart on the standard built 2.3-liter gasoline engine, the fuel alternative. 

Linde presented a forklift truck with a water-based internal combustion engine in 2008 (© Linde)




Noteworthy: In hydrogen operation, the engine delivered a rated output of approximately 65 kW at a compression ratio of 9: 1. As Daimler reported at the time, the car could drive in city traffic with a refueling about 130 km. Around 6 kg of hydrogen were stored in a magnesium hydride storage facility weighing about 300 kg. That corresponded to a gasoline equivalent of just over 20 liters. An actually bleak energy efficiency, which ultimately put an end to the "project", as the company announced on request. "The H 2 burner has half the efficiency of the H 2 fuel cell," says Daimler, adding the advice: "If you want to use hydrogen as a fuel, the fuel cell is the most sensible way."

Bavaria's prestigious project Hydrogen 7

But the Stuttgart were still optimistic in the 1980s and reported five years later that they have successfully completed their "large-scale experiment in Berlin, Mercedes-Benz production vehicles with hydrogen, successfully completed." In the 1988 annual report, they also announced new projects "for the use of hydrogen energy in the vehicle". The hydrogen they wanted to win together with Canadian and Norwegian institutions from hydropower, transport by tanker to Germany and in this country "use for bus fleets." It stayed with the announcement.
The engine of BMW's Hydrogen 7 ran successfully, but was discontinued due to problems with the liquefied gas tank (© BMW)
Years later, BWM also wanted to prove with Hydrogen 7 that this fuel is an attractive alternative to conventional fuel. In spring 2006, the company presented the first luxury sedan powered by a hydrogen combustion engine. Suitable for everyday use, as a company spokesman stressed at the time. And also the Bavarian engine developers were confident. In particular, the 750hL type 750hL specimens tested on the basis of the former 750i (E38) and the experience with the hydrogen prototype H 2 R from 2004 were promising. Because the hydrogen combustion engine of the Hydrogen 7 was technically almost identical to the engine of the 760i, the development costs were kept within limits. Already minor changes were enough.

Hydrogen burns up to three times faster

Mainly the intake tract of the engine had to be modified. Thus, in addition to the direct injection of petrol, the engineers integrated a supply line to the hydrogen tank. Special injection valves should always supply the right amount of hydrogen to the intake air. The valve opening times and the valve control had to be adapted to the new requirements. "A necessity, because hydrogen burns up to three times faster compared to conventional fuels", as Professor Hermann Rottengruber explains.
The Head of Department Energy Conversion Systems for Mobile Applications at the Institute for Mobile Systems of the Otto von Guericke University Magdeburg is closely linked to the development of the hydrogen engine. For several years, he was responsible for the drive advanced development of BMW AG for H 2 combustion processes - most recently as the overall responsible for hydrogen combustion processes in advanced drive development. During this time he also got to know the pitfalls of hydrogen combustion. Due to the low activation energy of hydrogen, unwanted explosions often occurred in the early development phase. But it managed to tame the engine.




Thomas Korn, CEO of Keyou, next to the prototype hydrogen combustion engine (© Keyou)

That's why the Hydrogen 7 project failed

This is also reflected in the performance figures. Powered by hydrogen, the Hydrogen 7 engine achieves only 191 kW and a torque of almost 390 Nm. On the other hand, there are the 327 kW and 600 Nm of the conventionally driven 760i. With a tank capacity of 8 kg was at that time a range of about 200 km possible. But why did the project fall into disfavor? Just when it succeeded to construct a successor engine, which had similar performance values as a gasoline engine.
On the one hand, the liquid hydrogen storage caused great headaches. The stored fuel at extremely low temperatures disappeared after some time despite extensive insulation. Crucial, however, was in addition to the lack of infrastructure and the verdict of the California Environmental Protection Agency EPA, the Hydrogen 7 not as a Zero Emission Vehicle (ZEV) recognize. It was feared that lubricating oil could get into the combustion chamber. Disappointed announced in 2009, the then BMW Development Board Klaus Draeger the Handelsblatt: "There will be no new hydrogen test fleet for the time being" [4].

Mazda holds on hydrogen rotary engine

But the hydrogen combustion engine is not finished yet. As Mazda announces on request, the Japanese OEM continues to research and develop hydrogen-powered internal combustion engines. "However, most of the resources are needed to develop our next generation of gasoline and diesel engines," says Mazda. This is another reason why only a relatively small engineering team continues to work on rotary piston hydrogen engines. That only this unit is used, has good reasons. "The Wankel engine offers clear principle-related advantages over conventional piston engines, especially in hydrogen operation," explains the company. Already 35 years ago, experiments have confirmed this.
In cooperation of Audi NSU, Neckarsulm, and the Research Association for Energy Technology and Combustion Technology (FEV), Aachen, "the advantage of the high power density of the rotary engine EA 871 was confirmed", as reported in 1983 [4]. In addition, the "necessary to adapt the engine measures are much easier than with reciprocating engines," wrote the authors. In their contribution, they showed, among other things, that the efficiencies of both engine types were about the same size, but that the "rotary engine has advantages in terms of nitrogen oxide emissions and power density". In addition, irregular burn phenomena such as pre-ignition or knocking were better controlled.



Industrial truck with charged hydrogen combustion engine

By the way, the engine developers at Volkswagen also have successes in the field of H 2 burning. In co-operation with the Industrial Engines division, Group research has developed a supercharged hydrogen direct injection engine for directing industrial trucks [5]. For Linde a prestigious project. In May 2008, it was able to present the unit for the first time in a forklift worldwide.
Although composting Gruber "holds in the near future highly unlikely" a renaissance of the hydrogen internal combustion engine for use in passenger car: he niche applications in places where hydrogen in large quantities is available (such as a process by-product), can certainly endorse. By the way, the truck has another advantage for those responsible for Volkswagen gasoline engine research: "Internal combustion engines can utilize this possibly 'contaminated' hydrogen, which is thus unsuitable for fuel cells,".




Aston Martin focuses on hydrogen in motorsport

With a different intention, the Institute of Internal Combustion Engines and Thermodynamics and Aston Martin approached the topic of hydrogen engine. For the 24-hour race at the Nürburgring, they have developed a twelve-cylinder naturally aspirated engine that will lead an Aston Martin Rapide S to victory. Although the Hybrid Hydrogen could not reach the top positions in Nürburg in May 2013. But the project "to operate the engine in hydrogen operation at partial load with a high air ratio and thus to produce no toxic nitrogen oxide emissions" was successful [6].
While the maximum 303 kW in hydrogen mode could be stably achieved according to the authors, the maximum torque decreased to 610 Nm at 4500 rpm. What was remarkable about the Hybrid Hydrogen project, however, was "that a racing car can be put on the road relatively quickly with components already available on the market".


Kovarik, B .: Henry Ford, Charles F. Kettering and the Fuel of the Future. In: Automotive History Review, 32: pp. 7-27
Carter, T .: Hydrogen drive for automobiles. In: MTZ 44 (1983), No. 6, p. 211
Annual Report 1988, Daimler-Benz AG
Fasse, B .: BMW loses faith in the hydrogen drive. In:
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December, 2009, accessed on February 6, 2017
Willand, J .; Grote, A .; Dingel, O .: The Volkswagen hydrogen combustion engine for industrial trucks. In: ATZoffhighway, June 2008, pp. 24-35
Luef, R .; Heher, P .; Hepp, C .; Schaffer, K .; Sporer H .; Eichlseder, H .: Conception and development of a hydrogen gasoline engine for racing. 8th Conference "Gas Vehicles", Stuttgart, 31 October 2013

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