Research on Combustion and Emission Characteristics of a N-Butanol Combined Injection SI Engine

Abstract

Using n-butanol as an alternative fuel can effectively alleviate the increasingly prominent problems of fossil resource depletion and environmental pollution. Combined injection technology can effectively improve engine combustion and emission characteristics while applying combined injection technology to n-butanol engines has not been studied yet. Therefore, this study adopted butanol port injection plus butanol direct injection mode. The engine test bench studied the combustion and emission performance under different direct injection ratios (NDIr) and excess air ratios (λ). Results show that with increasing NDIr, the engine torque (Ttq), peak in-cylinder pressure (Pmax), peak in-cylinder temperature (Tmax), and the maximum rate of heat release (dQmax), all rise first and then drop, reaching the maximum value at NDIr = 20%. The θ0-90 and COVIMEP decrease first and then increase as NDIr increases. NDIr = 20% is considered the best injection ratio to obtain the optimal combustion performance. NDIr has little affected on CO emission, and the NDIr corresponding to the lowest HC emissions are concentrated at 40% to 60%, especially at lean burn conditions. NOx emissions increase with increasing NDIr, especially at N20DI, but not by much at NDIr of 40–80%. With the increase in NDIr, the number of nucleation mode particles, accumulation mode particles, and total particle decrease first and then increase. Therefore, the n-butanol combined injection mode with the appropriate NDIr can effectively optimize SI engines’ combustion and emission performance.

The Influence of N-Butanol Addition in Gasoline on the Combustion in the Spark Ignition Engine

“…Small butanol quantities, until 20%, ensure a slight rise in the maximum pressure during combustion for all air-fuel ratios, but a 40% butanol ratio leads to a similar maximum pressure that is achieved when gasoline is used. An higher butanol ratio, 60-100%, leads to a reduction in combustion pressure for all used air-fuel ratios, and the reduction was more significant during lean mixture operations [6]. A similar tendency appears in terms of the variation between the maximum temperature and the butanol ratio at different air-fuel ratios.…”

“…Shang used different butanol injection ratios 20-100%, and different air-fuel ratios λ = 0.9-1.3. [6]. At a 20% butanol injection ratio, the maximum pressure and temperature during combustion starts to increase, in conjunction with the increase in the heat release rate.…”

“…Currently, because ethanol is used in blends with gasoline on a large scale, marketed under the name of gasohol, many studies have investigated its use in internal combustion engines. Today, due to its good combustion properties, butanol can be a viable alternative fuel for internal combustion engines, for diesel engines [3,4] and for spark ignition engines [5,6]. Butanol can be blended with diesel fuel or with biodiesel; the amelioration of the biodiesel's combustion properties at butanol use can assure the improvement of the diesel engine operation [3,4].…”

“…Lapuerta et al [5] recommend the substitution of ethanol with butanol to compensate for the engine cold starting issues that occur in ethanolgasoline fueled engines, especially in the case of E70 fuels, which contain large volume percentages of ethanol. Shang et al [6] used normal butanol as fuel in a spark ignition engine and they evaluated the combustion and emission characteristics using a regime of 1500 1/min speed and 10% engine load. Shang used different butanol injection ratios 20-100%, and different air-fuel ratios λ = 0.9-1.3.…”

“…The use of 100% butanol leads to an increase in combustion duration with almost a 10-20 crank angle degree comparative to classic fueling, especially when lean mixtures are used, λ = 1.2-1.3, depending on the quality of the mixture. For rich and stoichiometric mixtures, the influence of the butanol ratio on combustion is reduced [6]. The COV value of the IMEP starts to decrease for low butanol rates, around 20%, but a further increase in the butanol ratio to 100% leads to the increase in the IMEP cyclic variability with ~1% at λ = 1.2 and with ~11% at λ = 1.3, in correlation with the influence of the butanol ratio on the angle of the combustion end [6].…”