The potential of carbon-neutral diesel replacement fuels

  • RĂ©mon M.W. van Dijk

Student thesis: Master


In this research, the potential future fuels ammonia and dimethyl ether (DME) have been examined for their possibility to (partially) replace diesel within a compression ignition (CI) engine. Their characteristics could reduce the contribution of the transport sector to global warming. DME should have been analyzed in a constant volume combustion chamber, however, injection of DME was unsuccessful. Due to its strong resistance against auto-ignition, ammonia was tested in a naturally aspirated single-cylinder CI engine in a dual-fuel concept. In which diesel remained as a pilot fuel and gaseous ammonia was injected into the intake manifold. A fixed quantity of pilot diesel fuel was directly injected, after which higher loads were achieved by increasing the ammonia flow. This was repeated a second time with a larger pilot diesel quantity. Combustion properties show a delayed start of combustion for ammonia dual-fuel, presumably due to the decreased intake charge temperature. The combustion duration also increased in dual-fuel operation, as the ammonia-air mixture burns in a flame-propagation mode after being ignited by the various pilot diesel flames. CO emissions increase with ammonia, but this can only be a diesel contribution. The ammonia-air mixture probably results in an oxygen shortage around the diesel. On the other hand, HC emissions did not differ much from regular diesel operation. Looking at the CO2 emissions, a significant decrease can be noticed due to the carbon-free nature of ammonia. At low load, NOx emissions were elevated compared to regular diesel operation, probably due to the fuel bound nitrogen introduced by ammonia injection. However, at higher loads, the low flame temperature of ammonia seemed to result in a decrease in NOx emissions. Due to the presence of diesel as a pilot fuel, the soot emissions remained present in dual-fuel mode, but did not increase with an increase in load and fuel mass-flow. Finally, NH3 emissions were significant which would result in the requirement of additional exhaust aftertreatment measures. It is recommended to continue the study of ammonia/diesel dual-fuel with a direct liquid injection of ammonia to increase efficiency and decrease emissions even further.
Date of Award8 Oct 2021
Original languageEnglish
SupervisorNoud C.J. Maes (Supervisor 1) & Michel C.M. Cuijpers (Supervisor 2)

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