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Optimized direct-injection hydrogen engine estimated to exceed 2016 CAFE fuel economy targets at Tier 2 Bin 2 emission levels

The H2-DI engine was estimated to exceed 2016 CAFE targets with engine out Tier 2 Bin 2 (SULEV) emission levels. The team sees further potential for fuel economy improvement with engine downsizing. Source: Wallner 2011. Click to enlarge.

A project led by Dr. Thomas Wallner from Argonne National Laboratory has optimized a spark-ignited direct injection combustion system for a hydrogen engine (H2-DI). The engine delivers peak BTE of 45.5% and 33.3% BTE at the world wide mapping point (WWMP), and 14.3 bar BMEP. These results exceed the US Department of Energy (DOE) 2010 efficiency goals (45% peak, 31% BTE at WWMP).

Estimated drive-cycle fuel economy and emissions—based on the single-cylinder 0.66L research engine efficiency and emissions maps—was 32.4 mpg US city, 51.5 mpg US highway, 38.9 mpg US combined (7.26 L/100km, 4.57 L/100km and 6.05 L/100km, respectively), with NOx emissions of 0.017 g/mile. At that level of performance, the H2-DI engine would exceed 2016 CAFE fuel economy targets, along with delivering Tier 2 Bin 2 (SULEV) emissions levels without aftertreatment. (Emissions other than NOx are negligible for hydrogen combustion.)

Brake thermal efficiency results. Click to enlarge.   NOx emissions results. Click to enlarge.

For the estimates, the vehicle was assumed to be a mid-size sedan weighing 1,553 kg (3,424 lbs), outfitted with a 3.0L H2-DI engine and a 5-speed automatic transmission. Simulating the same midsize sedan with a 2.0L H2-DI showed a combined cycle fuel economy improvement to 45.4 mpg US (5.18 L/100km) as the engine was pushed into a more efficient operating range. However, the corresponding NOx increased to 0.028 g/mile which falls outside the SULEV II range but is still well within a Tier 2 Bin 5 DOE target.

Using direct injection to stratify the fuel-air mixture properly stratify resulted in high engine performance coupled with low NOx emissions. The mixture stratification target was to deliver a hydrogen-rich mixture around the spark plug, with lean mixtures close to the combustion chamber walls.

3D-CFD simulation assisted the injection strategy development. Nozzle design significantly influenced jet penetration pattern and mixture formation. (The team ended up using a 4-hole design.) Start of injection (SOI) influences stratification, and later injection is desirable to reduce compression work.

Among the factors contributing to the performance of the engine were an optimized bore/stroke ratio of 89 mm/105.8 mm stroke—increased engine stroke enables higher flame speeds and reduced quenching distance—and an increased compression ratio (12.9:1). An upgraded injection system (provided by Westport Innovations) used fast-acting Piezo injectors.

Collaborators and partners in the project included Ford, Westport, Sandia and Lawrence Livermore National Laboratories; international team members came from BMW, Graz University of Technology, and Ghent University.

The DOE-funded project concluded in September. Wallner and his colleagues are working on two follow-up publications, one with SAE, the other to be published in an IMech journal.




BFD hydrogen is NOT a fuel.

Roger Pham

Now, put this H2 engine in a full HEV like the Prius III, and one can see an improvement in hwy mpge of another 15-20% more, due to the use of Atkinson cycle and lower friction in the transmission. So, one can be expected to obtain a hwy mgpe of over 60 mpge, and a combined mpge of 65-70 mpge. Why is this number significant?

It means that an H2-HEV only need a 2kg-2-1/2-kg tank to be able to drive for 130-160 mile range for daily commute, while the same tank can be filled with natural gas in order to extend the driving range almost 3 folds for long-distance trips. Burning a mixture of 15% H2 and 85% NG, lean flammability should be drastically improved, such that the Hythane mixture should be able to deliver almost the same fuel economy as running pure H2.

Where does the H2 come from? Why, from H2 filling stations at every neighborhoods, put there to support the upcoming release of FCV's by 2015.

How is this H2 produced? From excess solar and wind electricity fed into the electrolyzers and storage tank built right into the H2 station. Net work communication will tell the electrolyzers when there is excess of renewable grid electricity to start H2 production. The mass adoption of renewable energy transportation may arrive a lot sooner than expected!


Im interrested to buy.


Wherever we get a H2 infrastructure, I would urge tax credits to convert existing ICE vehicles to run on hydrogen. I am sure it would be much less expensive for me to convert my 12 year old truck to run on H2 than to buy a new vehicle.


Without the DI system and higher compression, your performance on H2 would be very disappointing. BMW proved that with its dual-fuel V12 effort a few years ago.

Stan Peterson

Did anyone notice that no power or torque readings were offered or produced.

Once again governmental dweebs undertake a R&D project,wasting lots of money to NO AVAIL. They have produced an engine suitable for a lawnmower engine that get all of 40 mpg.

GEE Whiz!!! Be still my beating heart!


Ha! DOE still on the old school combustion kick? Be it H2, NG, or methane, burning stuff is outdated. We're going to use a new fire that's got the combustion geeks trembling. At least the FC movement declines combusting H2.

Roger Pham

The BMEP and the bore and stroke were given. From that info, one can calculate the hp and torque. At 5000 rpm at 13 bar BMEP with a bore of 89mm and stroke of 105mm, I calculate a bhp of 199 hp for a 4-cylinder version (2liter displacement?). May be a little less bhp if it can't develop 13 bar BMEP at 5000 hp, but it should.

Pretty good!


High compression ratio engines should be a good match for NG fuels and 50mpg vehicles will mean the lower energy density of NG will be some what overcome

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