Mahle Turns to Ammonia as ‘Clean’ Diesel Replacement

Mahle Powertrain is proposing the use of ammonia as a green fuel to replace the use of commercial diesel for heavy duty combustion engines.

The plan was put forward during a UK government funded competition to find an alternative to the heavy discounted ‘red diesel’ permitted for certain off-road industries, such as agriculture, mining, quarrying and construction.

As part of a project funded by the Department for Business, Energy & Industrial Strategy, Mahle, working with partners including Clean Air Power and the University of Nottingham, is trying to develop technologies to replace diesel with ammonia. It says the production and transportation infrastructure of ammonia is well developed and a prime candidate for decarbonization using renewable energy. This makes it a readily available, zero-carbon fuel for hard to decarbonize sectors which have energy demands that a pure-electric approach will struggle to meet.

Mahle suggests a two-pronged approach: in the near term, a retro-fit, dual-fuel arrangement is being tested on a six-cylinder turbodiesel genset engine. Additional injectors added to the air intake introduce ammonia as the main source of energy. The second approach is being developed using the company’s own single-cylinder engine and uses Mahle Jet Ignition (MJI) – a form of pre-chamber ignition – replacing the traditional spark plug to ignite the ammonia, eliminating the need for a fossil-fuel ignition source.

MJI consists of a small chamber in the cylinder head that, once ignited, forces the resulting hot gas through small orifices into the main combustion chamber as a series of jets that quickly and uniformly ignite the remaining mixture. The technology claims clean, efficient combustion throughout the chamber with little or no pollutants such as nitrogen oxides being produced. The combustion speed increase enabled deals with one of the challenges of using ammonia which typically burns at a comparatively slow rate.

Jonathan Hall, Mahle Powertrain’s head of research and advanced engineering projects, said: “Off-highway industries such as mining, quarrying and construction remain a significant challenge in the transition towards a more sustainable transport sector. These sectors have demanding energy and utilization requirements and are often in hazardous environments far from a power grid connection, making them difficult to electrify. Exploring other power sources such as ammonia has considerable potential, especially because there’s the opportunity to decarbonize the large numbers of vehicles and equipment already in operation and using diesel.”

— Paul Myles is a seasoned automotive journalist based in Europe. Follow him on Twitter @Paulmyles_

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