Exploration of flame characteristics of gasoline engine fuelled by gasoline-pentanol blends using combustion endoscopy

Alcohol-based fuels have shown high compatibility with spark-ignition (SI) engines, which require improvements in fuel efficiency and emissions reduction to meet modern environmental standards. While extensive research has been conducted on ethanol and other lower-order alcohols, there has been comparatively limited investigation into higher-order alcohols like butanol and pentanol as fuel alternatives. Previous studies on pentanol-gasoline blends in SI engines have demonstrated improved engine performance and reduced emissions. Building on this, the present study focuses on analyzing the flame characteristics-specifically speed and distribution-of pentanol-gasoline blends within the engine. In this study, pentanol was blended with gasoline by the volume of 10%, 20%, and 30%, namely 1-PNL10, 1-PNL20, and 1-PNL30, and tested in a twin-cylinder gasoline engine with an MPFI system at various load conditions. The study has focused on investigating the flame propagation of gasoline-pentanol blends by examining the in-cylinder flame image. The in-cylinder combustion evolution was visualized and captured by using an AVL Visio scope camera. Flame characteristics such as spatial flame distribution and flame speed were evaluated from the captured flame images for pentanol-gasoline blends and compared with sole gasoline. The flame study indicates that the addition of pentanol favored to increase in the flame speed, which in turn improved the combustion rate. The flame intensity and distribution area increased with the addition of pentanol in gasoline, demonstrating improved in-cylinder combustion with increased peak in-cylinder pressure and heat release rate. The insights on the flame characteristics of pentanol-gasoline blends were used to rationalize the discussion on engine performance and emissions. The performance of the engine was enhanced while increasing the proportion of Pentanol in the gasoline. The 30% Pentanol gasoline blend showed 5.71% higher BTE than gasoline at full load condition. Emissions like CO and HC also decreased at the same time, and NO emission increased. From the test results, it can be concluded that Pentanol can be blended with gasoline up to 30% without any engine modifications.