Can Hydrogen combustion engines replace diesels in trucks

by Premier Lubricants

A very interesting article in Transport operator, highlighting the research currently being done into hydrogen combustion engines to determine if they can replace diesels in trucks.

Mainstream manufacturers are now investigating ways in which internal combustion engines can continue to power heavy-duty long-range applications beyond the UK government’s proposed 2040 ban on diesel trucks.

First out of the traps is DAF, which has a hydrogen-powered internal combustion truck undergoing track testing, although it says production versions are at least five years away.

The H2 Innovation Truck, based on a 4×2 XF tractor unit, uses a modified version of DAF’s 13-litre MX engine with direct fuel-injection, spark ignition, and new cylinder liners, pistons and piston rings. Low engine speed torque is understood to be inferior to the parent diesel engine, so overall gearing is lowered to compensate.

An 800 km range is claimed – twice that of battery electric trucks – and refuelling is almost as fast as with diesel. In contrast, battery-electric trucks need hours to recharge, and payload is severely compromised by battery weight. Ron Borsboom, director of product development at DAF, said: “To cross the Alps you need 500 hp power, and due to distance and infrastructure that is now only possible with a combustion engine.”

Of the other mainstream European truck manufacturers, only MAN is known to be involved in a similar project, although its role as lead engine developer for Traton could see the technology cascaded down to Scania and Navistar. Remaining marques are concentrating on battery and fuel-cell solutions to power electric drivetrains.

But in the UK, Cummins and JCB are separately working on programmes to adapt existing diesel engine designs to run on hydrogen, while elsewhere in the world Deutz, Caterpillar and China Yuchai all have hydrogen-fuelled ICE projects underway.

Most of these companies have also been involved with projects to power electric vehicles or plant using hydrogen fuel cells, but it seems that growing realisations of the cost and fragility of such systems have convinced manufacturers to return to internal combustion. Not all the projects underway are primarily intended for truck and bus, but the technology would certainly be transferable from, for instance, static and mobile plant, to heavy-duty road vehicles.

Construction and agriculture equipment specialist JCB has taken the covers off a project which it says may see hydrogen-powered engines in commercial use at the end of this year. While JCB engines are unlikely to find their way into road vehicles in the near future, its hydrogen project illustrates how hydrogen engines could be developed to replace diesels in heavy-duty road-going applications.

With the exception of the pistons, its hydrogen engines use components common with the diesel engine from the cylinder-head down. Packaging the hydrogen engine into a machine designed for diesel is thus relatively easy.

Spark ignition is used to ignite the directly-injected hydrogen, and the engine’s compression ratio is reduced accordingly. A large variable-geometry turbo-charger (twice the size of the standard diesel unit) is specified for two reasons: one being that hydrogen does not disperse well in a confined cylinder so the momentum of a big slug of air is needed to mix the gas, and the other is that a generous supply of controllable intake air allows the torque characteristics of a conventional diesel engine to be replicated.

The exhaust gas consists mostly of water vapour from the combination of hydrogen and atmospheric oxygen. JCB says that NOx production during combustion is so low that no form of downstream exhaust treatment is required. Puffs of steam can be seen exiting the exhaust stacks of hydrogen-powered machines. The engines also run quieter than the equivalent diesel as there is no combustion ‘knock’.

Because there is no carbon in the combustion process, the lubricant of the hydrogen engine remains visually clean. However, water vapour passes the piston rings during the combustion process, and a specialist oil is required that can cope with this without emulsifying. Water contamination also strips additives from the lubricant, so regular oil changes are still required.

American engine manufacturer Cummins is using UK government funding to develop hydrogen combustion engines, based on its 6.7 and 15-litre engines, which would cover a broad spectrum of applications from city buses to long-haul heavy transport.

It said the engines will use new technologies to improve power density, reduce friction and improve thermal efficiency, avoiding the typical performance limitations and efficiency compromises associated with converting diesel or natural gas engines to hydrogen fuel. Following the proof-of-concept testing, the company plans to evaluate the engine in a variety of on- and off-highway applications, supporting the company’s efforts to accelerate the decarbonisation of commercial vehicles.

The hydrogen engines can use green hydrogen fuel, produced by Cummins-manufactured elec­trolisers, emitting near zero CO2 emissions through the tailpipe and near zero levels of NOx.

Caterpillar, a rival of both JCB and Cummins, although not currently active in the heavy-truck market, plans to have hydrogen-powered gensets available for demonstration by the end of the year.

Deutz’s TCG 7.8 H2 hydrogen engine is said to have passed initial bench tests with flying colours and is scheduled to go into full production in 2024. The six-cylinder TCG 7.8 H2 is based on an existing engine design and is rated at 200 kW. It will power electrical generators in service with a utility company before the end of this year.

Possibly the most advanced hydrogen engine so far is being developed in China. China Yuchai International, a leading manufac­turer and distributor of engines for on- and off-road applications in China through its main oper­ating subsidiary, Guangxi Yuchai Machinery Company Limited, an­nounced that the company’s YCK05 hydrogen-powered engine achieved stable ignition and op­eration in a demonstration at the Beijing Institute of Technology at the end of last year. The YCK05 engine is the first hydrogen en­gine for commercial vehicles in China, the world’s largest truck market.

The YCK05 hydrogen-powered engine adopts a number of ad­vanced special technologies such as high-pressure multi-point inlet injection technology, high-effi­ciency low-inertia turbocharging, and high-efficiency lean-burn combustion technology. The en­gine design upgrades the engine structure from its diesel parent, with new ignition and fuel-injec­tion systems.

In light-duty applications, Toyota, Mazda and Subaru, together with motorcycle and engine manufacturers Yamaha and Kawasaki, have joined forces to form a Team Japan dedicated to the future of internal combustion engines. Besides hydrogen, the companies are developing engines burning biomass-derived synthetic liquid fuels.

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