Comparison of Ethanol and Butanol as Additives in Soybean Biodiesel Using a Constant Volume Combustion Chamber

Abstract

To investigate the effects of different alcohol additives in biodiesel fuel on the spray, combustion characteristics, and soot formation and oxidation, a detailed comparative study between the butanolÀbiodiesel blend and the ethanolÀbiodiesel blend was carried out in an optical constant volume combustion chamber. Two different volumetric blend fuels were tested in this study with different ambient temperatures at the start of injection (from 800 to 1200 K). The volumetric ratios were the 20% butanol/80% soybean biodiesel referred to as B20S80 and 20% ethanol/80% soybean biodiesel referred to as E20S80. Results demonstrated that the microexplosion occurred for B20S80 and E20S80 fuels at 800 and 900 K ambient temperature because of the volatility difference between the additives (butanol or ethanol) and the base fuel (biodiesel). The E20S80 fuel presented higher peak pressure and shorter combustion duration compared to the B20S80 fuel. The autoignition was earlier for the B20S80 fuel at 1000 and 1200 K ambient temperature, while the autoignition of the B20S80 and E20S80 fuels was nearly the same at 800 K ambient temperature. The E20S80 fuel had a lower flame luminosity compared to the B20S80 fuel. The soot distribution was increased downstream of the spray jet with a higher ambient temperature for both tested fuels, and E20S80 had a lower value of normalized time-integrated soot mass (NTISM). Therefore, E20S80 has more advantages to reduce the soot emission compared to the B20S80 fuel. Also, increasing the ambient temperature from 800 to 1200 K led to a rapid increase in the value of NTISM for both tested fuels. Therefore, a lower ambient temperature with the piston at top dead center (TDC) should have more advantages to combustion and soot control in a real diesel engine.

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

“…The flame lift-off length was defined as the position closest to the injector where significant flame luminosity was observed. The analysis was restricted to a cone around the spray axis and the threshold was set to a certain percentage of the maximum pixel value occurring along the flame centerline [31,32]. In the present paper, the threshold was set at 10 percent of the maximum.…”

“…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.…”

Experimental investigations on nucleation, bubble growth, and micro-explosion characteristics during the combustion of ethanol/Jet A-1 fuel droplets

“…The overall benefits of the disruptive burning in emulsions has also been confirmed and visualized in spray flow and engines [27][28].…”

“…In practice, the occurrence of micro-explosions has the potential to enhance fuel atomization in the combustion chamber, which is considered as an effective way of promoting efficient combustion in an engine. Several numerical and experimental studies have been performed to understand the micro-explosion behavior of emulsified fuel droplets [19][20][21][22][23][24][25][26][27][28].…”

Optical characterization of Diesel and water emulsion fuel injection sprays using shadowgraphy

“…The Diesel fuel emulsion is then utilized in the CI engine as normal. The use of Diesel fuel emulsions has been shown to reduce NO x , CO, soot, hydrocarbons (HC) and PM emissions when used in a CI engine [3][4][5][6][7][8][9][10]. Diesel fuel emulsions have also been shown to slightly improve the brake thermal efficiency of a CI engine [8,[10][11][12].…”