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High-Pressure Direct-Injection Hydrogen Engine Achieves Efficiency of 42%; On Par with Turbodiesels

H2BVplus hydrogen combustion engine. Click to enlarge.

The BMW Group Forschung und Technik, in cooperation with researchers in Graz and Vienna, Austria, has developed a dedicated (i.e., monovalent) hydrogen combustion engine with diesel-like geometry and progressive H2 high-pressure direct-injection technology. The result is an efficiency level of up to 42%, on par with that of the best turbodiesel engines.

The “H2BVplus” project is aimed at investigating a hydrogen self-ignition combustion process. Current hydrogen combustion engines are spark-ignited. Sponsored by Austria’s Federal Ministry for Transportation, Innovation and Technology (BMVIT), project partners include BMW, the Institute for Internal Combustion Engines and Thermodynamics at Graz University of Technology, HyCentA Research GmbH in Graz, as well as HOERBIGER ValveTec GmbH in Vienna.

A combustion system employing hydrogen self-ignition opens up new opportunities concerning both efficiency and power output for alternative automotive propulsion systems.

High efficiency is targeted in H2 vehicles on economic and energy grounds, as well as to minimize the space required for the fuel tank. The need for high power density is better satisfied in a hydrogen engine due to the excellent ability for turbocharging, especially compared to spark-ignited engines, given that combustion anomalies such as knocking and backfiring may be ruled out. An additional and significant increase in compression ratio is possible.

The absence of a particulate emission limit, which forces conventional diesel-type engines to be operated at lean mixture, allows for operation at a stoichiometric air/fuel ratio to provide both maximum mixture calorific value and, subsequently, mean effective pressure (BMEP). The injection of hydrogen within the high-pressure phase of the engine cycle additionally boosts BMEP.

In terms of compression ratio, efficiency and consequently vehicle operating range, the self-ignition combustion system is expected to be superior to actual H2 -Otto-type IC engines. The project earlier was able to realize some self-ignited operating points with induction air heating assistance and an increased compression ratio on an Otto-type research engine inherited from earlier H2-related projects, and also to devise promising layouts for combustion chamber and injector nozzle geometries via the extensive use of 3D CFD simulation tools. Based on these design proposals, the completely new diesel-type research engine and the related high-pressure injection units were realized in hardware.

The main challenge for a combustion of hydrogen with self-ignition is the high auto-ignition temperature. Other challenges include maximum pressure increases and ignition pressures, the impact of high EGR rates and NOx formation rates.

The newly developed combustion system combines the strengths of spark-ignition and diesel concepts, while utilizing the favorable combustion properties of hydrogen to achieve the efficiency values.

The engineers based their work on the joint EU “HylCE” project, during which maximum specific powers of up to 100 kW per liter of displacement were demonstrated for a spark-ignition hydrogen combustion process.

3D-CFD simulation of hydrogen high-pressure injection. Click to enlarge.

Engineers from the BMW Group Forschung und Technik developed a new cylinder head for hydrogen operation based on a production diesel engine. The combustion chamber of the engine was configured jointly by BMW and the Graz University of Technology using numerical flow simulation. HOERBIGER ValveTec GmbH designed high-pressure injectors for direct injection of hydrogen into the combustion chamber with pressures of up to 300 bar (30 MPa or 4,351 psi). These injectors were tested and calibrated at the Hydrogen Center Austria, which also provided the hydrogen infrastructure.

H2BVplus HOERBIGER hydrogen high-pressure injectors. Click to enlarge.

Extensive test runs on the test benches of the Institute for Internal Combustion Engines and Thermodynamics of the Graz University of Technology have shown that a combination of spark-ignition and diesel combustion systems using surface ignition subsequently followed by a diffusion type of combustion is the ideal solution with respect to engine efficiency. As a result, the entire characteristic engine map range of a typical passenger car engine can be covered and top level efficiency values are achieved.

Attendant benefits are the increase in specific power and reduction of fuel consumption. Thus, even in an early concept phase, this combustion system matches the efficiency values of the currently best turbodiesel engines at a maximum of 42%. As the exhaust gas heat of internal combustion engines can be used well due to the high temperature levels, further increases in overall efficiency will be possible in the future as a result of waste heat utilization.

BMW Forschung und Technik GmbH is a 100% subsidiary of BMW AG and has been responsible for research within the BMW Group since 2003. Its subject areas cover Vehicle Technology, Clean Energy (hydrogen technology), EfficientDynamics (intelligent energy management/alternative drive systems), ConnectedDrive (driver assistance/active safety) and IT Drive (IT and communications technology).

HOERBIGER ValveTec GmbH is a company of the HOERBIGER Group. HOERBIGER is active throughout the world as a leading player in the fields of compression technology, automation technology and drive technology. The focal points of its business activities include key components and services for compressors, gas-powered engines, and turbomachinery, hydraulic systems and piezo technology for vehicles and machine tools, as well as components and systems for shift and clutch operations in vehicle drive trains of all kinds.

The core objective of the Institute for Internal Combustion Engines and Thermodynamics at the Graz University of Technology is to carry out innovative and internationally recognized teaching and research within the interrelated fields of energy, engine, transport and environment, and in particular to contribute to solving environmental problems.

The HyCentA (Hydrogen Center Austria) promotes the use of hydrogen as a regenerative energy carrier. With its hydrogen test center and the first hydrogen delivery station in Austria, the HyCentA acts as a focal point and information platform for hydrogen-oriented research and development activities.




Hydrogen fuel cell peak efficiency - 50%
Hydrogen fuel cell cost - £100,000

Hydrogen ICE peak efficiency - 42%
Hydrogen ICE cost - £2,000

I feel sorry for the folks at Ballard....


I wouldnt worry the fuel cell is moving forward quite well. The main point of the fuel cell is making electric power and this h2 ice engine wouldnt be anywhere near as good as a fuel cell at doing that.


For a car, an ICE might be more appropriate than a fuel cell and less futuristic... The advantage of an ICE is that it could work either on Gazoline or H2 then making it flex fuel and then marketable even if the distribution network of H2 is very scarce in its infancy. And asides of the price this is a killing advantage compared to fuel cell that you won't seel until there is a fuel network of distribution (ok you could have a H2 generationg station at home but there are poorly efficiency since making H2 from electricity is a dead end because of the overwhole poor well to wheel efficiency, H2 has to be generated from heat, biomass or coal or nat gaz to be efficiently produced not from electricity.

Given the properties of H2 they should be able to hit close to 50% efficiency on a ICE.


Reminds me of the $398 million Bridge to Nowhere.


Actualy treehugger a home h2 fuel generator makes sense in alot of places.

At 10 cents per kwh night rate a modern h2 generator will make and compress it for between 4.5-5 bucks a kg compressed to 5k psi.

Given the milage rates of fuel cell cars thats about 5-7 cents a mile.

And many places in the us can get night rates as low as 4 even 2 cents per kwh. Giving costs as low as 1 cent per mile.

None of these cars will break the energy bank realy anytime soon as they wont pass 1 million cars for years and wont pass 10 million for years more. Even at 10 million cars filling h2 with cheapest night power shouldnt require anything magical industry wise.

And if finding refill stations is all that hard they can always have 2 tanks and a 6-800 mile range. If oil goes way up in cost im sure people wont mind a little less trunk space. And mass produced a fuel cell is cheaper then an engine and 6 speed hybrid tranny... smaller too.



Cost is not the right way to look at it. Keep in mind taht 50% of electricity is mad from coal in this country so a H2station at home might me sense in term of $/mile but makes absolute no sense in term of EROI and environment, since an H2 car powered this way would be more duty and CO2 incorrect than a gazoline car. Electricity from coal might be cheap because you don't take into account the cost of the degradation to environment to it, put it in it and it is a sink. Again : electricity is not the right way to generate H2 (think again what sense it makes to transform Coal to electricity then to H2 then compresse it then make electricity again then to mechanic energy again). Starting fromn Coal, the right way would be C + H20 = CO + H2, burn CO into CO2 to produce electricity and burry it , store H2 for car use, that is still not satisfying since Coal is finite resource and need to be mined but you can do the same thing using biomass.


"...and NOx formation rates"

Internal combustion creates these and fuel cells do not.


Um treehugger at night most power in california is nuke based. California is where the main rollout will be. Also japan again mostly nuke at night and iceland mostly hydro.

So nope it doesnt matter.

Besides the big rollout seems to be china and they wont listen to any of us nor care what we think so realy it doesnt matter again.

By the time h2 and bev migrate widely coal will either be clean or gone and the power grid will be much cleaner then now... or we will all be dead or mutated into icky thingies or too fat and obsessed with playing wow III to move.


electricity at night is nuke yes but if everybody start to make its own H2 at home the nuke base load won't be enough and then back to coal. Again H2 from electricity is not the right approach even if it come from nuke, nuke is not that efficient at making electricity to start with so generaty H2 after all the losses in line to compress it and retransform it to electricity in the fuel cell is not efficient, which means it will have a cost.


Its more then good enough for the first 10-15 years. And besides we likely as not dont have a choice in the matter. Batteries arnt likely to get good enough fast enough to handle everything and biofuels just wont cover it.

As for the cost as I said before its lower then oil very quickly.


I still question the viability of hydrogen as a transportation fuel due to its very low volumetric energy density, regardless of whether it's used in an ICE or fuel cell.


A big stationary turbo-diesel, 4-stroke engine can attain a mechanical efficiency of 48.5 %
much higher than 42%.
And a big 2-stroke diesel can attain 52% efficiency!!


Add exhaust heat recovery (another BMW specialty) to the ICE and you're up to 50% efficiency no bother.


I see no difference from H2 HCCI operation and gasoline HCCI combustion. Both raise OTTO cycle efficiency to the same range as Diesel cycle efficiency.

So what else is new? You start with a barrel of oil in both cases, and waste lots of energy in processing and weight in a LDV to runH2. Today with PZEV cleanup technology now so avialble (56 models in 2008 model year) there is no difference out the tailpipe. So where is the benefit?

There is none.




Everyone and his brother talking about fuel and energy.
How about mandatory telecommuting for all information workers?
How about energy efficient houses?
How about eating food from a 10 miles radius?
How about becoming rational?
This crisis can't be wasted.



Thermal efficiency is what determines an engines fuel consumption and gas and diesel barely break 20% and very few do that. Ethanol and Hydrogen have both attained thermal efficiency ratings of 42 to 43% making both considrably better than gas or diesel not to mention that they both put out 90 to 99% less pollution when compared to gas or diesel.



The Prius 'Atkinson' cycle engine manages 36% peak thermal efficiency as a result of the 13:1 expansion ratio. Much better than Otto cycle gasoline engines with ~10:1 expansion ratio.

Most road-going VW TDi engines are in the 42-43% thermal efficiency range and their 3L lupo engine was alledged to be closer to 50% thermal efficient. They manage this mainly by having a large expansion ratio (~17-20:1).

The point is it's not the type of fuel that matters, but the expansion ratio of the engine used to burn them that largely dictates thermal efficiency.



That wasn't really my point, but now that you mention it, I would argue that "well-to-wheels" energy consumption is what you actually need to consider, and diesel-hybrids (DHEVs) have been shown to be at least as efficient as the best fuel cells, and in many cases more efficient, from a well-to-wheels perspective, based on all studies I've seen. This is also true of fuels derived from biomass (source: Well-to-Wheel Efficiency For Alternative Fuels From Natural Gas or Biomass, Ecotraffic (Sweden)).

I just question the wisdom of going to a gaseous fuel (e.g., hydrogen) for transportation, which will require a new infrastructure, when little or no efficiency will be gained over the best liquid-fueled vehicles (little or no infrastructure change required), at least in the foreseeable future.


Actually, VW claimed the peak BTE of the Lupo TDI engine was 51% ( ).


How about direct injection CNG. If the new Ford EcoBoost for engines were dual fueled with CNG or gasoline, they would get good mileage, have good performance, clean up the air and reduce oil imports.

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