Critical review on recent progress of ethanol fuelled flex‐fuel engine characteristics

Abstract

Summary Ethanol‐powered spark ignition (SI) engines have the potential to mitigate the twin crisis of fossil fuel depletion and exhaust emissions. However, the successful promotion of ethanol is hindered due to the restriction of fuel blend diversity and design features in the conventional SI engine. The fuel flexibility can be overcome by the use of flex‐fuel engine (FFE) technology with appropriate changes in engine design features for a wide range of ethanol blends. The understanding of FFE based on various technical aspects has greater potential in the automotive sector. Therefore, this review paper provides a holistic approach to critically analyze the various technical aspects of FFE. In this work, the application of ethanol blends on FFE output characteristics is reviewed critically considering the effects of engine operating conditions and parameters. Further, the impact of ethanol blends on material compatibility, cold starting characteristics, and unregulated emissions are analyzed. The outcome of the study shows that combustion and performance characteristics such as cylinder pressure(CP), heat release rate (HRR), and brake thermal efficiency (BTE) are improved in FFE operation due to the clean‐burning characteristics of ethanol blends. Also, carbon monoxide(CO) and hydrocarbon (HC) emissions decreased without any significant improvement in nitrogen oxides (NOx) emissions with a wide range of ethanol shares in FFE. Finally, this study summarizes the present status of research in FFE and creates a route towards the direction of multidisciplinary research need in the future that supports the application of different types of biofuels in FFE.

Modelling the end-use performance of alternative fuel properties in flex-fuel vehicles

“…Additionally, fuel pumps and injectors of FFVs are designed to operate at higher flows due to the lower calorific content of ethanol. Another aspects of high ethanol blends are related to cold start issues which in modern FFVs are resolved by advanced injection strategies [23]. The technological advancements of FFVs lead to a significant increase in energy conversion efficiency as well as to the reduction of greenhouse gas emissions [24].…”

“…In practice, the Engine Management System (EMS) of FFVs receives the signals from the lambda sensor as well as from the sensor of ethanol concentration in the fuel tank. Based on that data, EMS adjusts engine operating parameters including boosting pressure, injection timing and quantity, ignition timing, intake and exhaust flow handling systems, and Exhaust Gas Recirculation (EGR) system [23]. Such optimizations allow FFVs to utilize more efficiently high ethanol content fuels (e.g.…”

“…In 2022, FFVs are continuously produced by manufacturers, however, their market share and penetration remain low. When looking at the development trends of FFVs, G. Azhaganathan, and A. Bragadeshwaran classified them into six generations (produced from 2003, 2006, 2008, 2009, 2013, and 2019) [23]. In general, progressively with FFV generations, higher ranges of compression ratios were introduced along with improvements in engine power and torque.…”