PIT has evaluated many hydrogen injection systems over the years. Contrary to manufacturer claims, none of these technologies has shown any ability to reduce vehicle fuel consumption. In addition, long term operational assessments of similar systems have shown that device reliability is a significant problem. In fact, we can legitimately question the usefulness of hydrogen injections into diesel engines. Hydrogen has higher energy content than regular fuels and its combustion theoretically produces no pollutants. These engines are closely related to natural gas or propane systems which substitute some of the diesel energy with another fuel. Unlike hydrogen, natural gas and propane have similar properties to diesel or gasoline and are thus more liable to be used in engines using those fuels. A joint study by Pahang University in Malaysia and the Indonesian Science Institute has demonstrated that the use of hydrogen injection systems actually degrades performances. The study also shows a correlation between an increase in the rate of hydrogen injection and a reduction in the peak pressure inside the cylinder along with reduced engine output under engine load test.
For systems with onboard hydrogen generators, one of the problems is the efficiency of the process: burning hydrogen creates insufficient energy to reach the energy threshold for producing the gas. Another potential hurdle is that today’s vehicles and engines are extremely complex machines that need to be carefully adjusted to meet stringent emissions standards: injecting another gas into the engine intake could conflict with the engine’s initial settings. Therefore, the engine control unit could consider the fuel-air mixture too weak and increase the amount of fuel injected, which would cancel the possible positive potential effects of hydrogen injection.
Ref.: W.B. Santosoa, b, R.A. Bakara, A. Nurb, Combustion Characteristics of Diesel-Hydrogen Dual Fuel Engine at Low Load, International Conference on Sustainable Energy Engineering and Application, November 2012, Yogyakarta