HyDie, Dual-Fuel-Bus - Hydrogen-Diesel Dual fuel drive for fast reduction of CO² emissions in public transport

In an 18-month research project an effective conversion of an urban-bus typical diesel engine to the hydrogen-diesel dual-fuel operation was, for the first time worldwide, analyzed. Among other parameters, the CO² reduction potential (based on the substitution of the diesel fuel with hydrogen), the diesel-combustion-typical pollutants emission reduction, and powertrain‘s efficiency were measured in order to evaluate the advantages of this technology.

Short Description

Starting point / Motivation

For heavy-duty traffic, diesel engines with high power and torque are usually in use. Mainstream alternative propulsion technologies, such as some already developed for passenger vehicles, are not effectively applicable today on the transport sector.

Both battery electric- and fuel cell electric vehicle concepts cannot meet the necessary energy- and power-densities requirements of heavy-duty vehicles and are far from fulfilling its durability expectations. Moreover, the high costs associated to those powertrain technologies are anyway working against its spread introduction in the market.

In 2012, Alset (a technology and engineering company) initiated a feasibility study on hydrogen-diesel dual-fuel combustion process, converting and investigating a 6-cylinders-inline 3L diesel engine. The results confirmed the high potentials of the technology, and the urban bus has been selected as the most logic market start-up application.

Different bus operators have meanwhile showed great interest in the HyDie Dual-Fuel bus propulsion technology, which was furthermore investigated by the means of this study.

Contents and goals

Within the context of this research project, a preliminary assessment was performed in order to characterize the potential of applying the hydrogen-diesel dual-fuel technology in a commercial vehicle engine. To do so the focus was set on following targets:

  • Unimpaired power performance
  • Up to 80% of diesel fuel savings (up to 80% CO²-reduction using renewably produced hydrogen)
  • Efficiency optimization
  • Considerable reduction of soot particles emissions
  • Considerable reduction of hydrocarbon emissions
  • Reduction of NOX-emissions in the part load operational range

The combination of hydrogen with biodiesel fuel actually represented a zero CO² solution.


The basis for the hydrogen-diesel dual-fuel operation was created through specific mechanical modifications on the Intake and Exhaust systems, based on 1D-Flow Simulation calculations. The other important change was implemented on the engine management side, with the implementation of the new required functionalities and controls for precise hydrogen port fuel injection, load exchange and combustion.

The basic layout simulation demanded the creation of an appropriate 1D-Gas Exchange model. Implementation effectiveness was then tested with real components, while back feeding variations on the simulation could be carried for further optimization.

The definitive constructive solution for hydrogen metering into the intake manifold (H2-Rail, H2-Injectors integration), the control adjustment of the exhaust gas (including Turbo-charger), as well as all sensor adaptations, was then integrated in a prototype assembly. It was assumed that the adaptation of the combustion chamber geometry might also be beneficial for hydrogen-diesel operation (e.g. variation of compression ratio and piston bowl geometry).

Results and Conclusions

Within the framework of this project, the scientific prerequisites for the upgrade of the commercial vehicle engines with an dual-fuel as well as the commercial basis for an economical implementation, even with small unit numbers, were created. Although a retrofitting of mechanical components on the motor is necessary, these modifications are limited to the exchange of individual components.

Once the potential of the technology is fully confirmed, the subsequent step is to further develop the hydrogen-diesel technology in order to build and integrate a HyDie prototype engine in an urban bus for real-life road testing.


Project Partners

Project manager

Ao.Univ.-Prof. Dr. Peter Sturm, Research Institute for combustion engines and thermodynamics mbH

Project partner

  • Dr. Peter Grabner, TU Graz – Institute of internal combustion engines and thermodynamics
  • DI Gonzalo Auil, Alset GmbH

Contact Address

Research company for combustion engines and thermodynamics mbH
Ao.Univ.-Prof. Dr. Peter Sturm
Tel.: +43 (316) 873-30200
E-mail: office@fvt.at

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