Dual injection: An effective and efficient technology to use renewable fuels in spark ignition engines

Abstract

Modern spark ignition engines mostly use one injection system to deliver gasoline into the combustion chamber, using either direct injection or port fuel injection. Both technologies have their respective advantages. To integrate their advantages and to promote the use of renewable fuels, dual injection engines are in development in recent years. Dual injection represents an advanced combustion system and is a novel technology to address the urgent issues of sustainability and environmental protection. This study reviews the state-of-the-art research on dual injection spark ignition engines with a focus on renewable fuels, their advantages and engine performance. The main advantages of dual injection include greater control flexibility, enhanced cooling effect, knock mitigation, engine downsizing, extended lean-burn limits, higher thermal efficiency and reductions of several emission species. The most promising renewable fuels for dual injection are ethanol, methanol and hydrogen. Each renewable fuel is aimed at different advantages of dual injection.Alcohol-gasoline dual injection provides great anti-knock ability by taking advantage of alcohols' large enthalpies of vaporisation and high octane numbers, while hydrogen-gasoline dual injection provides extended lean-burn limits by taking advantage of hydrogen's low ignition energy, wide flammability limit and high flame speed. Direct injection of renewable fuels is the optimal injection strategy because it effectively utilises the strong cooling effect of alcohols or avoids the volumetric efficiency reduction and preignition of hydrogen. Dual injection generally demonstrates higher thermal efficiency than single injection.In addition, dual injection effectively reduces particulate emissions while there are usually trade-offs among gaseous emissions.

Optimising microscopic spray characteristics and particle emissions in a dual-injection spark ignition (SI) engine by changing GDI injection pressure

“…Gasoline Direct Injection (GDI) engines have been a preferred selection by the automotive industry in recent years due to the advantages of improved fuel economy, transient response and power performance [1][2][3][4][5][6][7][8]. However, particles emitted by GDI engines not equipped with Gasoline Particulate Filter (GPF) are recognised higher than that of Port Fuel Injection (PFI) engines and some diesel engines with the Diesel Particulate Filter (DPF) [9][10][11][12][13][14].…”

“…Nowadays, particle emissions from vehicles powered by GDI engines negatively affecting air quality and human health have attracted more attention from researchers [15] [16]. The emission standards have also been more stringent for the restrictions of particle emissions [10] [11] [14]. In 2014, Euro 6b standard released and first limited the Particle Number (PN) emissions from vehicles powered by GDI engines to 6×10 12 /km.…”

Exploring the potential benefits of Ethanol Direct Injection (EDI) timing and pressure on particulate emission characteristics in a Dual-Fuel Spark Ignition (DFSI) engine

“…With the advantages of superior volumetric efficiency, thermal efficiency, power output, and transient response, Gasoline Direct Injection (GDI) engine has become an increasingly prevalent option for ICE and vehicle manufacturers [10] [11]. However, compared to Port Fuel Injection (PFI) engine, particulate emissions of GDI engine are usually higher owing to higher spray impingement possibility and shorter air-fuel mixing time [12]. Moreover, the regulations for particulate emissions of GDI-powered vehicles have become more stringent in recent years.…”

“…Moreover, the regulations for particulate emissions of GDI-powered vehicles have become more stringent in recent years. For example, in 2014 and 2017, Euro 6b and Euro 6c standards limit the particulate number of GDI-powered vehicles to 6×10 12 /km and 6×10 11 /km, respectively.…”

Effects of Water Injection Strategies on Oxy-Fuel Combustion Characteristics of a Dual-Injection Spark Ignition Engine

“…In 2005, an advanced technology named dual-injection was commercially applied to SI engines by Toyota [36]. Furthermore, with the advantages of flexible fuel injection, dual-injection SI engines have been a hot topic for researchers in recent years [37][38][39][40][41][42]. The thermal efficiency, gaseous and particulate emissions have been investigated in this type of engine by using gasoline plus various fuels such as methanol, ethanol and 2,5-dimethylfuran.…”