# Effects of Ethanol-Diesel on the Combustion and Emissions from a Diesel Engine at a Low Idle Speed
## 1 Introduction
[17] applied diesel blended with 5%, 10%, 15% and 20% ethanol by volume to a single-cylinder direct injection diesel engine, and conducted experiments on five engine load conditions (25%, 50%, 75%, 90% and 100%) and two engine speeds (the rated and maximum speed). The addition of ethanol reduced CO and NOx, and increased HC and BSFC. In the study of Author links open overlay panel [PERSON] et al. [18], 15% ethanol-diesel blended fuel was applied to a four-cylinder 3.2-L diesel engine, which demonstrated that CO and HC increased and NOx decreased. [PERSON] et al. [19] applied ethanol to diesel and biodiesel to confirm its impact. The concentrations of ethanol in the test fuels were 2, 4, 6 and 8% by volume. It was reported that the BTE improved as ethanol increased, while HC and CO decreased, but NOx increased. [PERSON] et al. [20] conducted a study using five types of ethanol-diesel blended fuels (0, 10, 20, 25 and 30% ethanol by volume). The BTE was reduced because the lower heating value (LHV) of ethanol is low, and the smoke was reduced. The CO decreased above the central load, but increased at low loads and low speeds. Furthermore, the HC increased. However, NOx had different emission trends depending on each fuel condition, engine load and engine speed condition. In addition to the studies of the application of ethanol with diesel, many studies are underway on the application of methanol, an alcohol-based fuel that is less-frequently mixed with diesel than ethanol, but is fully applicable. [PERSON] [21] and [PERSON] et al. [22] used various proportions of methanol and ethanol-diesel fuel to compare combustion and emission characteristics. In this study, bioethanol was blended with diesel fuel and applied to a four-cylinder common-rail direct injection diesel engine applied to a commercial passenger vehicle. Notably, this experiment was conducted in a low-speed idle condition. Low idling operation is one of the worst operating conditions of the engine, with poor combustion and high exhaust pollutants. [PERSON] et al. [23] explained that, during idling, the mixture of air and fuel is rich, and combustion is unstable due to the low operating temperature of the engine, resulting in the increased generation of exhaust pollutants, and more exhaust pollutants being emitted when devices such as air conditioners are operated. [PERSON] et al. [24] explained that the engine has a thermal efficiency of 30% under high-speed driving conditions, but only 3-11% at idle. Many researchers reported increased emissions of exhaust pollutants under idle conditions using heavy-duty engines. [PERSON] et al. [25] reported an increase in NOx under idle conditions, [PERSON] et al. [24] and [PERSON] et al. [26] showed an increase in HC and [PERSON] et al. [27] showed an increase in CO. The previous studies were conducted and researched with engines from heavy-duty trucks at high idle, over 1000 rpm. In the above mentioned high idle, the engine runs at a low rated speed with a low load. The experimental conditions of this study were carried out at low-idle speed, rather than a high-idle speed, with an engine for passenger cars. In addition, the fuel injection pressure was 280 bar, the lowest of the engine operating conditions, resulting in relatively poor fuel atomization. In these poor combustion conditions, at a low idle speed, the following objectives were intended to be carried out using bioethanol-diesel fuel, which is an oxygen fuel: (1) study of the effects of combustion due to high oxygen content, low density and low LHV, which are characteristics of bioethanol; (2) check the change in emission of bioethanol; (3) check the validity of bioethanol application.