Comparative Analysis of the Combustion Stability of Diesel-Methanol and Diesel-Ethanol in a Dual Fuel Engine

Abstract

The co-combustion of diesel with alcohol fuels in a compression ignition dual fuel engine is one of the ways of using alternative fuels to power combustion engines. Scientific explorations in this respect should not only concern the combustion process in one engine cycle, which is most often not representative for a longer engine life, but should also include an analysis of multiple cycles, which would allow for indicating reliable parameters of engine operation and its stability. This paper presents experimental examinations of a CI engine with a dual fuel system, in which co-combustion was performed for diesel and two alcohol fuels (methanol and ethanol) with energy contents of 20%, 30%, 40% and 50%. The research included the analysis of the combustion process and the analysis of cycle-by-cycle variation of the 200 subsequent engine operation cycles. It was shown that the presence and increase in the share of methanol and ethanol used for co-combustion with diesel fuel causes an increase in ignition delay and increases the heat release rate and maximum combustion pressure values. A larger ignition delay is observed for co-combustion with methanol. Based on changes in the coefficient of variation of the indicated mean effective pressure (COVIMEP) and the function of probability density of the indicated mean effective pressure (f(IMEP)), prepared for a series of engine operation cycles, it can be stated that the increase in the percentage of alcohol fuel used for co-combustion with diesel fuel does not impair combustion stability. For the highest percentage of alcohol fuel (50%), the co-combustion of diesel with methanol shows a better stability.

Comparative Analysis of Combustion Stability of Diesel/Ethanol Utilization by Blend and Dual Fuel

“…For the mid-load condition, the substitution was increased to 63%; however, for low and high loads, higher ethanol fractions could not be used because of insufficient ignition energy at low loads and high values of pressure rise under high loads [7]. Similar results were obtained by other authors; all of them showed that the share of ethanol has a positive effect on soot emissions, while there are different opinions regarding NO x emissions [8][9][10][11]. On the one hand, ethanol reduces the temperature on the compressed load due to the high heat of vaporization.…”

“…Combustion process of blend was characterized by high increase in COV of IMEP. Already for 19% ethanol, energetic fraction COVIMEP exceeded 5%, which is a limit value for industrial engines [10]. In case of dual fuel technology, the COV of IMEP was below 5% and its maximal value was reached for 50% of ethanol fraction, equal to 3%.…”

“…In that combustion system, the ignition of nearly homogeneous mixture of air and fuel is realized by injection of diesel fuel 17 degree of crank angle before top dead center (TDC). This construction system requires the additional power supply by injector or injectors, tank with alternative fuel and other necessary equipment [10,11,22].…”

“…Due to omitting the heat transfer to walls, crevice volume, blow-by and the fuel injection effect, the resulted heat release rate is termed as the net heat release rate [8]. A detailed description of the research procedure and results development is included in our previous papers [10,11,14].…”

An Experimental Study on the Performance and Emission of the diesel/CNG Dual-Fuel Combustion Mode in a Stationary CI Engine

“…where N is the cycle index and p max is the mean value of maximum pressure of N cycle p maxi . One of the indicators enabling the assessment of the stability of operation of an internal combustion engine may also be the probability density of selected parameters of its operation [29]. The function that allows us to express the probability of obtaining or occurrence of a specific value of the analyzed parameter is the probability density function.…”