Wärtsilä hydrogen research bears fruit

“We have successfully proven the concept and tested the addition of hydrogen in two different types of engines, at concentrations of up to 60% hydrogen,” Kaj Portin told the Motorship in early March.

The two engine types were spark-ignited gas engines and dual-fuel engines with a small micropilot. Wärtsilä had also successfully proven the concept of hydrogen addition in high-pressure gas engines, Portin noted.

The successful testing of engines based on the direct inclusion of hydrogen as a fuel represents an important step in the development of hydrogen technology for marine engines for the deep-sea market. Other alternatives, including hydrogen fuel cells, are at various stages of development but are unlikely to be suitable for use in deep-sea vessels in the medium term.

Directly including hydrogen requires engine designers to adapt to hydrogen’s particular properties, such as the need for tight control over lean air-fuel mixtures in order to avoid excessively fast burning (and the production of CO2 emissions), as hydrogen has a very high flame speed at stoichiometric ratios.

“An engine is a good basis on which to start,” Portin said, noting that building on existing gas and diesel engine technology permits developers to leverage existing research.

LNG research experience

One of the technical challenges posed by the introduction of hydrogen is its accelerating impact on combustion, which leads to higher accumulations on NOx and higher pressures which need to be resolved.

A related challenge is the gas’s relatively high autoignition temperature. This has important implications when a hydrogen-air mixture is compressed to higher pressures, as this complicates ignition.

Higher combustion chamber temperatures and pressures requires optimisation of the air flow to the cylinder, which in turn depends on improved visualisation of compression data and valve timings, as well as developments to optimise the combustion chamber design.

In fact, Wärtsilä has developed different controls to enable variable valve timings in its engine control panel. “We continue to look at optimising further in this area,” Portin said, noting that this will offer improved safety, as well as improved operational performance, via faster in-loading, and ignition control.

Portin notes that this is a complex area but that Wärtsilä developed significant experience in this area developing dual-fuel LNG engine technology, while recent advances in sensor and engine management control systems permit greater control.

Hydrogen research

Wärtsilä began blue sky research into the use of hydrogen as a fuel over 20 years ago but began a focused development programme in 2014.

The low temperatures required for hydrogen liquefication create pressures on operating machinery: compression pumps need to be able to withstand temperatures 100 degrees colder than LNG. Meanwhile, at higher concentrations, it is necessary to look at pipe sizes and leakage around the engine, Including the injection valve and return block.

“We do not envisage anyone running an engine fully on hydrogen, but we have been able to run test engines at concentrations of over 60%,” Portin said. “However, the engine requires certain modifications to efficiently run on mixtures containing above 60% hydrogen. It ceases to be a natural gas-fuelled engine and becomes a hydrogen engine.”

Dual-fuel ready?

The requirement for obtaining separate classification society type approval for a hydrogen-fuelled engine is likely to delay the introduction of hydrogen engines, leaving aside issues around the economics of hydrogen production or the development of hydrogen supply chains. In the short to medium term, class society rules are likely to impose a de facto 25% regulatory ceiling on hydrogen use.

However, Portin noted that because the engine modification requirements to introduce hydrogen into existing engines are comparatively simple, existing Wartsila dual-fuel LNG engines could be retrofitted to run on 10-15% hydrogen “relatively quickly”.

The introduction of hydrogen may require cylinder lubrication oils to withstand higher combustion temperatures but would requires lower BN cylinder lubricants as a clean burning fuel.

Environmental advantages

Kaj Portin noted that the market will require a range of different fuels to meet the demands of future regulations, and that the research into hydrogen formed part of Wärtsilä’s strategy.

The advantage of introducing hydrogen into the marine fuel market is that it will help the industry meet 40% reduction of carbon intensity per transport work by 2030. Wärtsilä is committed to helping the maritime sector meet its 2030 and 2050 commitments. Many different tools will be required to help the industry meet these objectives, including research in equipment and propulsion technology, Portin concluded.