Effects of ethanol on combustion and emissions of a gasoline engine operating with different combustion modes

Abstract

The introduction of fuel economy and CO2 emission legislations for passenger cars in many countries and regions has spurred the research and development of more efficient gasoline engines. The pumping loss at part-load operations is a major factor for the higher fuel consumption of spark ignition (SI) gasoline engines than the diesel engines. Various approaches have been identified to reduce the pumping loss at part-load operations, leading to improved fuel economy, including Early Intake Valve Closing (EIVC), Positive Valve Overlap (PVO) and Controlled Auto-Ignition (CAI) combustion. On the other hand, in order to reduce the CO2 emissions from the fossil fuel, ethanol produced from renewable resources is becoming widely used in the gasoline engine. In this paper, the performance, combustion and emissions were measured, analyzed and compared between gasoline and its mixture with ethanol (E15 and E85) at a typical part-load condition when a direct injection gasoline engine was operated with the CAI combustion by means of the negative valve overlap (NVO) and SI combustion by means of the intake throttled, EIVC and PVO. An electro hydraulic actuated camless system enabled the engine to be operated with CAI combustion and SI combustion of different valve timings and durations at the same load. The results showed that the CAI combustion reduces NOx emissions by more than 90%. The PVO results in better mixture preparations and improved combustion efficiency and best fuel economy compared to all the other modes. The EIVC operation led to a moderate improvement in the fuel conversion efficiency over the throttled SI operation but it was characterised by the slowest combustion and worst HC and CO emissions. Fewer and smaller particles numbers were detected in EIVC using E0 and E15 fuel blends. Using ethanol blends reduces the knocking combustion in CAI modes by about 50%. The use of E85 resulted in an increased number of particulate emissions in EIVC but increased ISFC in all the modes. The particulate emission results showed that soot is the dominant particle in the exhaust.

Blending Octane Number of Ethanol in HCCI, SI and CI Combustion Modes

“…This was attributed to the high latent heat of vaporization of ethanol and additional charge cooling benefits. Ojapah et al compared the performance, combustion process and emissions between four operating modes with gasoline and its blend with ethanol, E15 and E85 [22]. It was highlighted that multiple fuel injections and higher injection pressure can lead to reduction in the fuel consumption.…”

The Evaluation of Liquefied Petroleum Gas (LPG) Utilization as an Alternative Automobile Fuel in Nigeria

“…A state-of-the-art Ricardo single-cylinder electrohydraulic valve actuation (EHVA) camless engine with a compression ratio of 11.78 was used for the experiment that was used to validate the model built with the Ricardo WAVE. The model was validated using experimental data and results from Ojapah et al, 2016 [14]. The performance and the emission characteristics of the simulated engine were studied when fueled with different blend ratios of LPG and compared with RON95 fuel.…”

The Effect of Back Pressure Change on Exhaust Emissions According to the Confluence Geometry of a Dual Exhaust System in Idling

“…Thus, with respect to the valve overlap of the gasoline engine, various studies have been conducted on the effects of variable valve timing (VVT) and variable valve lift (VVL), i.e., devices related to the opening and closing of intake and exhaust valves inside cylinders, on exhaust gas emission [6][7][8][9][10][11][12].…”