Engineers from UNSW Sydney (Australia) have successfully converted a diesel engine to run as a dual-fuel hydrogen-diesel engine, reducing CO₂ emissions by more than 85% compared to conventional diesel. The team, led by Professor Shawn Kook from the School of Mechanical and Manufacturing Engineering, spent around 18 months developing the Hydrogen-Diesel Direct Injection Dual-Fuel System that allows existing diesel engines to run using 90% hydrogen as fuel.

The researchers say that any diesel engine used in trucks and power equipment in the transportation, agriculture and mining industries could ultimately be retrofitted to the new hybrid system in just a couple of months.

In a paper published in the International Journal of Hydrogen Energy, Prof. Kook’s team shows that using their patented hydrogen injection system reduces CO₂ emissions to just 90 g/kWh—85.9% below the amount produced by the diesel powered engine.

High indicated mean effective pressure (IMEP) of up to 943 kPa and 57.2% indicated efficiency was achieved at 90% hydrogen energy fraction, at the expense of NO_x emissions. The hydrogen injection timing directly controls the mixture condition and combustion mode. Early hydrogen injection timings exhibited premixed combustion behaviour while late injection timings produced mixing-controlled combustion, with an intermediate point reached at 40 °CA bTDC hydrogen injection timing.

At 90% hydrogen energy fraction, the earlier injection timing leads to higher IMEP/efficiency but the NO_x increase is inevitable due to enhanced premixed combustion. To keep the NO_x increase minimal and achieve the same combustion phasing of a diesel baseline, the 40 °CA bTDC hydrogen injection timing shows the best performance at which 85.9% CO₂ reduction and 13.3% IMEP/efficiency increase are achieved.

—Liu et al.

The Hydrogen-Diesel Direct Injection Dual-Fuel System features independent control of hydrogen direct injection timing, as well as diesel injection timing, enabling full control of combustion modes: premixed or mixing-controlled hydrogen combustion. Image from Prof. Shawn Kook

The UNSW team’s solution to the problem maintains the original diesel injection into the engine, but adds a hydrogen fuel injection directly into the cylinder.

The new Hydrogen-Diesel Direct Injection Dual-Fuel System does not require extremely high purity hydrogen which must be used in alternative hydrogen fuel cell systems and is more expensive to produce.

The research team hope to be able to commercialize the new system in the next 12 to 24 months and is keen to consult with prospective investors. The researchers say the most immediate potential use for the new technology is in industrial locations where permanent hydrogen fuel supply lines are already in place.

That includes mining sites, where studies have shown that about 30% of greenhouse-gas emissions are caused by the use of diesel engines, largely in mining vehicles and power generators. The Australian market for diesel-only power generators is currently estimated to be worth around $765 million.

Resources

• Xinyu Liu, Gabrielle Seberry, Sanghoon Kook, Qing Nian Chan, Evatt R. Hawkes (2022) “Direct injection of hydrogen main fuel and diesel pilot fuel in a retrofitted single-cylinder compression ignition engine,” International Journal of Hydrogen Energy, doi: 10.1016/j.ijhydene.2022.08.149