Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

Fall 2011

Document Type


Degree Name

Master of Science (MS)


Department of Integrated Science and Technology


Since their invention, internal combustion engines have played a major role in the social and economic development of many countries by allowing people and goods to move from one place to another for longer distances and in shorter times. However, the negative environmental impacts of the widespread use of internal combustion engines in private and commercial vehicles have reached alarming values, with future prospects being much worse. In addition, fuel consumption and the dependency on oil imports of many countries have increased sharply in the past years as vehicle populations and use increased. The current trends are clearly unsustainable and thus new technologies are to be sought that can reduce both engine tailpipe emissions and fuel consumption. Hydrogen enhanced combustion has the potential of doing this. For this reason three engines – a carburetted petrol engine, a fuel injection petrol engine and a diesel engine – have been tested to investigate the effects of adding small amounts of hydrogen to the air intake of the engines on performance and HC, CO and CO2 emissions. The engines were tested at different engine speeds and loads to simulate normal on-the-road operating conditions. The hydrogen was produced from the electrolysis of a solution of distilled water and sodium hydroxide using two different electrolyser designs. Both the hydrogen and oxygen that were produced by electrolysis were added to the engine‘s intake during the tests. The results show that the addition of hydrogen-oxygen is most effective in stabilizing and enhancing the combustion of lean air-fuel mixtures inside the petrol injected engine, allowing for lower HC, CO and CO2 emissions. Thus hydrogen enhanced combustion could play a role in stabilizing lean burn petrol engines. However, it also transpired that a major drawback of the technology is the energy input required to produce the hydrogen, which in most cases was higher than the increase in output resulting from the more efficient combustion. Thus system optimization and alternative means of energy input would be required to ensure that a net positive effect is achieved.



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