Prospects of Dual-Fuel Injection System in Compression Ignition (CI) Engines Using Di-Methyl Ether (DME)

Abstract

Governments worldwide have imposed strict emission regulations to control GHG emissions from the road transport sector. The industry is under stress to find alternative fuels and technologies to cope with these stringent emission regulations. E-Fuels are the kind of alternative fuels whose production aim towards storing electrical energy from renewable energy sources in the form of chemical bonds of fuels. Soot and NOx emissions are the main problems in diesel-fuelled compression ignition (CI) engines. Using alternative fuels alone can solve the issues related to conventional Fuel, but it has its challenges. Optimization of fuel injection strategies along with the use of alternative fuels has been explored as a solution. The dual-fuel mode has shown superior control over the combustion and simultaneous reduction of soot-NOx in several studies. DME is one of the most promising ultra-clean, alternate CI engine fuels. DME is considered as an e-fuel if production occurs from renewable energy sources. Its superior atomization characteristics result in the homogeneous fuel–air mixture formation. Its higher cetane number (CN) and oxygenated nature help to achieve efficient in-cylinder combustion. This results in lower PM, soot, hydrocarbons (HC), and carbon monoxide (CO) emissions than baseline diesel. However, nitrogen oxides (NOx) and unregulated emissions are higher in DME direct injection (DI) engines. The operating range of DME homogeneous charge compression ignition (HCCI) engines is limited due to knock intensity; however, it can be widened using the dual-fuel mode. DME has ultra-low viscosity, high vapour pressure, and negligible self-lubrication characteristics, which create difficulties in the conventional fuel injection systems to handle the DME. These challenges can be overcome by using high octane number (ON) fuel as an ignition suppressor to reduce the chances of knocking and coefficient of variance (COV) of engine performance parameters with DME used in CI engines. This chapter explores different injection strategies and fuels in dual-fuel mode by considering DME as an E-Fuel. The combustion and emission characteristics of the DME dual-fuel engine are discussed.