Combustion Characteristics and Soot Distributions of Neat Butanol and Neat Soybean Biodiesel

Abstract

The combustion characteristics and soot distributions of neat butanol and neat soybean biodiesel were explored in an optical constant-volume combustion chamber using natural flame luminosity and forward illumination light extinction methods under various ambient temperatures (800 and 1000 K) and oxygen concentrations (21%, 16%, 10.5%). Results demonstrated that butanol had a higher normalized peak pressure compared with the biodiesel. Soybean biodiesel autoignited earlier than butanol at 21% and 16% oxygen, while a reverse trend was found at 10.5% oxygen. The oxygen concentration had little effect on the autoignition timing for butanol when it was between 16% and 10.5% at 800–1000 K. The natural flame luminosity reduced with lowered oxygen concentration and the flame distribution was notably increased at 10.5% oxygen. At 800 K ambient temperature, there was no soot formation detected for butanol, while the net soot release for soybean biodiesel was reduced with the decrease of oxygen concentration. At 1000 K ambient temperature, the net soot release increased for both butanol and soybean biodiesel with the decrease of oxygen concentration. Compared with butanol, soybean biodiesel had a higher value of normalized time integrated soot mass (NTISM) under all conditions. The value of NTISM increased about 16 times from 800 to 1000 K for the soybean biodiesel at 10.5% oxygen, indicating that low oxygen concentration will deteriorate combustion and increase the difficulty of soot emissions control for the soybean biodiesel under a higher ambient temperature.

Impacts of acetone on the spray combustion of Acetone–Butanol–Ethanol (ABE)-Diesel blends under low ambient temperature

“…The natural flame luminosity is an important parameter as it is an indicator of soot formation [1,4,31,35]. It can be seen that the natural luminosity first appears at the region between the injector tip and the chamber wall.…”

“…Butanol has recently been identified as a feasible alternative to diesel fuel in CI engines [1][2][3][4]. Acetone-Butanol-Ethanol (ABE) fermentation is one of the major methods used to produce bio-butanol.…”

“…Studies [1,4,14,15] have also shown superior clean combustion capabilities of alcohol fuels, relative to diesel and biodiesel, particularly under LTC conditions.…”

Feasibility of using less viscous and lower cetane (LVLC) fuels in a diesel engine: A review

“…Liu et al [204] constructed a constant volume combustion chamber encompassing an electronically controlled unit injector, a pressure transducer, a flame luminosity measuring device to capture combustion, an electric heater to heat the cylinder wall, oil and fuel lines, and all other essential accessories in order to replicate the scenario of a diesel engine so as to operate butanol and soy biodiesel as neat fuel. For the reported experiment, two ambient temperatures of 800 K and 1000 K were maintained while at a specific air density, the concentration of oxygen was varied and kept at three different values of 21%, 16% and 10.5%, reflecting no EGR, medium EGR and heavy EGR conditions, respectively.…”

Experimental study on diesel conventional and low temperature combustion by fueling four isomers of butanol

“…Han et al [27] investigated the effects of different fuel properties and injection strategies on LTC and found that n-butanol was more suitable to enable LTC than diesel fuel as using the high-pressure direct injection strategy. Liu et al [28,29] investigated flame structure and soot quantitative distribution by using n-butanol and soybean biodiesel on a constant volume chamber and found that n-butanol presented more benefits than soybean biodiesel in LTC mode. This is because n-butanol has lower boiling point and viscosity, higher vaporization heat and these fuel properties can improve the mixing process and results in lower flame luminosity and soot concentrations.…”