Dual fuel ethanol port injection in a compression ignition diesel engine: Technical analysis, environmental behavior, and economic viability

The increase in prices, dependence on fossil fuels, and concerns about greenhouse gas emissions, and strict emissions regulations have motivated researchers to look for low carbon renewable fuels for internal combustion engines. Ethanol is one of these fuels due to its presence in the energy matrix of several countries. Among the methods applied to use ethanol in compression ignition engines, the primary technique currently studied is port fuel injection (PFI). This research studies the feasibility of using ethanol as a partial fuel in a generator set analyzed beyond the technical and environmental parameters and the economic aspect. The experiments were conducted in a diesel single-cylinder engine, with its original diesel fuel direct injection system, and added an auxiliary PFI system for the ethanol supply. The research gap is based on the lack of studies that include, in addition to the analysis of performance parameters and gaseous emissions, the economic viability assessment for the studied engine, which is also a fundamental factor in an actual application. The engine was tested under different conditions of six progressive replacements of diesel fuel by ethanol, starting only with diesel fuel (baseline test) and increasing ethanol mass fraction up to 0.634. The measured data showed that ethanol effectively increased ignition delay and reduced combustion duration, which did not lead to increased efficiency and reduced fuel consumption. The maximum in-cylinder pressure was 71.3 bar in the baseline test and dropped progressively to 51.6 bar when in the most significant substitution. The rate of heat release increased by about 92.5% with ethanol concerning the baseline test. When ethanol was used, the CO emissions decreased by up to 43%, resulting in about 2.4 g/kWh, while NOx emissions reduced by up to 20% compared to the baseline test, achieving 0.69 g/kWh. The economic analysis made it clear that the operational cost increased when the engine worked with ethanol replacing partially diesel fuel. However, with a slight increase in operational cost, especially in São Paulo (SP) state, it is possible to reduce pollutant emissions. For the baseline test, the operating cost was 0.354 U$/kWh. The specific fuel cost reaches a maximum of 0.441 U$/kWh, 25% higher than the respective baseline test, increasing ethanol fraction.