# Effects of Ethanol-Diesel on the Combustion and Emissions from a Diesel Engine at a Low Idle Speed
## 1 Introduction  
The development of next-generation internal combustion engines and new technologies to prevent air pollution and the depletion of resources is underway around the world. Many researchers [1; 2; 3] are studying the application of alternative fuels to improve the mechanical functioning and efficiency of internal combustion engines. [PERSON] et al. [1] and [PERSON] et al. [2] summed up the features of bio-diesel produced with various kinds of raw materials, and reported that biodiesel's were sufficient as a fuel for internal combustion engines and were likely to reduce emissions and prevent the depletion of fossil fuels. [PERSON] et al. [3] studied GTL (Gas-To-Liquid), a synthetic fuel in the form of a clean diesel fuel generated by the Fischer-Tropsch process, and reported its potential as a fuel for the diesel engine. The representative alternative fuel is biofuel, such as biodiesel and bioethanol, which is produced from vegetable or animal raw materials. Biodiesel and bioethanol have the advantage of containing oxygen in the fuel itself. Biodiesel contains oxygen, ranging from 10 to 12 percent [4; 5; 6; 7], and ethanol contains about 35 percent [8; 9]. Many studies have been conducted on the application of biodiesel todiesel engines that have confirmed biodiesel's positive effect on the reduction of pollutant emissions emitted from diesel engines [2; 10; 11; 12]. Ethanol is known to be an acceptable fuel for gasoline engines because it has a high octane number [13]. Pure ethanol cannot be used in diesel engines, but it can be used by in blends with diesel fuel. For use as a fuel in an internal combustion or diesel engine, ethanol has many favorable properties [14], such as low viscosity, high oxygen content, high H/C ratio, low sulfur content and high evaporative cooling, which improve its volumetric efficiency. Ethanol has a lower viscosity compared to diesel, which results in the superior atomization of fuel injected into cylinders, and improves the mixing with air when it is blended with diesel. Ethanol also has a high latent heat of evaporation, so using ethanol in a diesel engine by blending it with diesel or biodiesel fuel can increase the volume efficiency by the evaporative cooling of ethanol in the intake and compression strokes. There are three ways to apply ethanol to diesel engines [13; 15]. The first method is to supply ethanol fumigation to the intake air using a carburetor or an injector on the manifold. The second method is to build a dual injection system on the cylinder head by modifying the configuration of the system and mechanically changing the engine cylinder head. Lastly, ethanol can effectively be used in diesel engines by blending alcohol and diesel, while preventing phase separation, without modifying the engine system. Many studies have been conducted on the third approach of the above methods. [PERSON] et al. [16] compared the results of the experiment obtained by applying ethanol 10%-diesel and ethanol 30%-diesel fuels to a four-cylinder direct injection diesel engine. NOx, CO and smoke decreased when using the ethanol blends, but HC increased. [PERSON] et al. [13] experimented by blending 10% and 15% ethanol (by vol.%) with conventional diesel in a six-cylinder heavy-duty direct injection diesel engine. In that study, CO and NOx tended to decrease slightly, while HC increased. Furthermore, BSFC increased but BTE decreased with increasing alcohol concentration. [PERSON] [14] applied ethanol-diesel blends, which had 10% ethanol and 15% ethanol by volume, to a single-cylinder four-stroke engine to conduct an experiment with an engine load of 30 Nm at 1000 rpm and 1800 rpm. The results of the experiment showed that CO, HC and smoke opacity decreased, but NOx and BSFC increased. [PERSON] [15] tested the effect of a 15% ethanol-diesel blend on three engine speeds (1500, 2000, 2500 rpm) and several engine loads (BMEP 3.3, 5.0, 6.6, 8.3 bar), and reported an increase of pollutant emissions and BSFC. [PERSON] et al.