An Enabling Study of Low Temperature Combustion With Ethanol in a Diesel Engine

Abstract

An Enabling Study of Low Temperature Combustion With Etbanoi in a Diesei EnginePrevious research indicates that the low temperature combustion (LTC) is capable of producing ultra-low nitrogen oxides (NOx) and soot emissions. The LTC in diesel engines can be enabled by the use of heavy exhaust gas recirculation (FGR) at moderate engine loads. However, when operating at higher engine loads, elevated demands of both intake boost and EGR levels to ensure ultra-low emissions make engine controllability a challenging task. In this work, a multifuel combustion strategy is implemented to improve the emission performance and engine controllability at higher engine loads. The port fueling of ethanol is ignited by the direct injection of^ diesel fuel. The ethanol impacts on the engine emissions, ignition delay, heat-release shaping, and cylinder-charge cooling have been empirically analyzed with the sweeps of different ethanol-to-diesel ratios. Zerodimensional phenomenological engine cycle simulations have been conducted to supplement the empirical work. The multifuel combustion of ethanol and diesel produces lower emissions of NOx and soot while maintaining the engine efficiency. The experimental setup and study cases are described, and the potential for the application of an ethanolto-diesel multifuel system at higher loads has been proposed and discussed.

Clean combustion enabling with ethanol on a dual-fuel compression ignition engine

“…In the RCCI combustion mode, early and multiple diesel injections are typically applied to stratify the cylinder charge and thus organize the combustion event in a controllable manner. [24][25][26][27][28] For the fuel combination of ethanol and diesel, previous studies on the DF application often indicated a maximum ethanol fraction existed for successful engine operation. [29][30][31][32] In Tsang et al, 29 Rodrı´guez-Ferna´ndez et al, 30 and Himabindu et al, 31 for instance, the upper limit of ethanol ratio was 15%-20% due to drastically increased pressure rise rates.…”

Impacts of multiple pilot diesel injections on the premixed combustion of ethanol fuel

“…The combustion at higher engine loads has been reported in past publications. 4, 23 Therefore, this set of experiments focuses on the study of the ignition ability and the engine performance with a single diesel fuel injection at low to medium engine loads.…”

“…The overall trends for the emissions were as expected and agreed with those reported in previous publications. 23,28 With an increased engine load, the premixed in-cylinder charge was richer and tended to burn more completely. The high combustion temperature promoted the oxidation of CO and THC, and the formation of NO x .…”

“…8,19,20 A high fuel volatility and a medium to low reactivity to compression ignition are found to be the key enablers for combustion with low emissions and a high efficiency. 21 Diesel and biodiesel are often employed as the high-reactivity fuels to guarantee ignition, 22,23 and gasoline, ethanol and other high-octane-rating fuels are used as the low-reactivity fuels to regulate the burning rate. [23][24][25] These fuels can be prepared as premixed fuel blends delivered with the original direct-fuel-injection systems, 22,24,25 or mixed inside the cylinder using two individual fuel delivery systems to achieve reactivity-controlled compression ignition (RCCI) 26 or dual-fuel combustion 23 with various fuel injection strategies.…”

“…21 Diesel and biodiesel are often employed as the high-reactivity fuels to guarantee ignition, 22,23 and gasoline, ethanol and other high-octane-rating fuels are used as the low-reactivity fuels to regulate the burning rate. [23][24][25] These fuels can be prepared as premixed fuel blends delivered with the original direct-fuel-injection systems, 22,24,25 or mixed inside the cylinder using two individual fuel delivery systems to achieve reactivity-controlled compression ignition (RCCI) 26 or dual-fuel combustion 23 with various fuel injection strategies. The primary advantage of in-cylinder fuel mixing over fuel blending is the flexibility of fuel ratio modulations which can be achieved on a cycle-to-cycle basis according to the requirements of different engine operation conditions.…”