Biogenous Ethanol: CO2 Savings and Operation in a Dual-Fuel Designed Diesel Engine
To be published on September 9, 2019 by SAE International in United States
The usage of ethanol and two different mixtures of ethanol and gasoline (E85 and E65) was investigated on a modified diesel engine designed to work in a dual-fuel combustion mode with intake manifold alcohol injection. The maximum ratio of alcohol to diesel fuel was limited by irregular combustion phenomena like degrading combustion quality and poor process controllability at low load and knock as well as auto-ignition at high load. With rising alcohol amount, a significant reduction of soot mass and particle number was observed. At some testing points, substituting diesel with ethanol, E65 or E85 led to a reduction of NOx emissions; however, the real benefit concerning the nitrogen oxides was introduced by the mitigation of the soot-NOx trade-off. With regard to the engine efficiency aspect, the results show bidirectional behaviour: at low load points engine efficiency degrades, whereas the process becomes by up to 6 % (rel.) more effective at higher engine loads. Substituting diesel via manifold injected alcohol at higher mean effective pressures also enhances the EGR tolerance, making it possible to apply higher EGR rates without deteriorating engine efficiency or increasing soot emissions the same way as in diesel reference operation. Substituting diesel with intake manifold injected alcoholic fuels impressively lowered the engine CO2 emissions at medium and high load testing (by up to 7 % (rel)). A case study of the bioethanol production by the Austrian bioethanol producer AGRANA demonstrated the high ability of bioethanol to reduce the holistic well-to-wheel CO2 emissions of the dual-fuel powered diesel engine. Additionally, a simulation model is built for the test engine and selected operation points of the engine test bed measurements are implemented into the model. The discussion of the simulation results allows an efficiency analysis and therefore a better understanding of the findings of the engine stand experiments.