H 2 Internal Combustion Engine (ICE) Technology

First deployed in mobile applications in the late 19 th century the internal combustion engine is - apart from the wheel - the most indispensable technological precondition for today's road transportation. Over 100 years of research and technological developments have made the ICE the most reliable and affordable, though still environmentally challenging, propulsion system. This obstacle can however be overcome by using an appropriate fuel - a fuel such as hydrogen that oxidises almost only to pure water during the combustion process.

All internal combustion engines depend on the exothermic chemical process of combustion or burning: the reaction of a fuel with the ambient air oxygen taking place inside the engine's combustion chamber.

While most common fuels used today are made up of hydrocarbons and are derived from crude oil (such as diesel, gasoline and liquefied petroleum gas) or from natural gas, also liquid and gaseous biofuels (such as ethanol) or even hydrogen (either in compressed form as CGH 2 or in liquefied form such as LH 2 ) can be used.

Using hydrogen as a fuel in internal combustion engines means benefiting from a number of advantages that hydrogen provides in comparison to conventional fuels:

  • When using hydrogen in ICE, exhaust gas emissions are extremely low. The MAN-engine currently used in the HyFLEET:CUTE project vehicles is already way below the EU's future emission limits. The values are for nitrogen oxide (NO X ) about 0.2 g/kWh (in comparison Euro 5: 2.00 g/kWh), for hydrocarbons (HC) 0.04 g/kWh (0.46) and for particulate matter (PM) less than 0.005 g/kWh (0.02). Carbon monoxide emissions remain below measurable limits (all values according to the European Stationary Cycle, ESC).
  • No greenhouse gases are emitted whatsoever, due to the absence of carbon material.
  • Depending on the fuel production paths, hydrogen ICEs can be operated fully independently of fossil fuels.
Pic.: MAN hydrogen ICE H 2876 UH01 with 150 kW


Hydrogen internal combustion engines are typically based on ICEs designed for the combustion of natural gas (CNG). However, substantial research and fundamental adjustments are necessary to make them powerful components in powerful vehicles. But as most components are identical with those used in conventional diesel engines, the costs at present remain much lower than those for fuel cell propulsion systems.

The hydrogen internal combustion engines used within HyFLEET:CUTE are 4-stroke 6-cylinder engines made by MAN. While the first four buses will be equipped with a naturally aspirated Otto engine with a maximum output of 150 kW the engine will continue to be developed within the framework of the project. The next 10 buses will be powered by a new and more efficient 200 kW lean burn engine with exhaust gas turbo charging and intercooling.

Pic.: Future generation hydrogen ICE MAN H 2876 LUH01 with 200 kW
Pic.: New injection valve of the naturally aspirated hydrogen ICE H 2876 UH01 with 150 kW


The most important characteristics of the current engine generation comprise:

•  External mixture formation with electro-magnetic injection valves

•  Sequential intake-manifold fuel injection

•  Spark ignition

•  Quantitative power regulation with throttle valve

•  Engine management system Bosch ME7 GAS1

•  4-stroke Otto engine, naturally aspirated

•  6 cylinders inline, horizontally installed

•  Maximum torque: 760 Nm 1000 - 1400 rpm

•  Maximum power: 150 kW @ 2200 rpm

•  Exhaust gas after treatment with NOx reduction catalyst

Source: MAN July 2006

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