Browse Publications Technical Papers 2008-01-1787

Experimental Investigation of the Effects of Combined Hydrogen and Diesel Combustion on the Emissions of a HSDI Diesel Engine 2008-01-1787

The effects of load, speed, exhaust gas recirculation (EGR) level and hydrogen addition level on the emissions from a diesel engine have been investigated. The experiments were performed on a 2.0 litre, 4 cylinder, direct injection engine with a high pressure common-rail injection system. Injection timing was varied between 14° BTDC and TDC and injection pressures were varied from 800 bar to 1400 bar to find a suitable base point. EGR levels were then varied from 0% to 40%. Hydrogen induction was varied between 0 and 6% vol. of the inlet charge. In the case of using hydrogen and EGR, the hydrogen replaced air. The load was varied from 0 to 5.4 bar BMEP at two engine speeds, 1500 rpm and 2500 rpm.
For this investigation the carbon monoxide (CO), total unburnt hydrocarbons (THC), nitrogen oxides (NOx) and the filter smoke number (FSN) were all measured. The in-cylinder pressure was also captured to allow the heat release rate to be calculated and, therefore, the combustion to be analysed.
The experimental data showed that although CO, FSN and THC increase with EGR, NOx emissions decrease drastically. Inversely, CO, FSN and THC emissions decrease with hydrogen, but NOx increases. This inverse relationship will allow the combination of EGR and hydrogen induction to be optimised to minimise both FSN and NOx. When hydrogen was introduced the peak cylinder pressure was increased, as was the rate of cylinder pressure rise. The position of the peak cylinder pressure was delayed as hydrogen addition increased. This together with the obtained heat release patterns shows an increase in ignition delay, and a higher proportion of premixed combustion.


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