Controlling Gasoline Low Temperature Combustion by Diesel Micro Pilot Injection

Abstract

The simultaneous reduction of fuel consumption and pollutant emissions, namely NOx and soot, is the predominant goal in modern engine development. In this context, low temperature combustion concepts are believed to be the most promising approaches to resolve the above mentioned conflict of goals. Disadvantageously these combustion concepts show high peak pressures or high rates of pressure rise due to early ignition and high reaction rates especially at high loads. Furthermore, there are still challenges in controlling combustion phasing. In this context using a small amount of pilot Diesel injected directly into the combustion chamber to ignite a highly diluted gasoline air mixture can overcome the aforementioned difficulties. As the gasoline does not ignite without the Diesel, the pilot injection timing can be used to control combustion phasing. By increasing dilution even high loads with low rates of pressure rise and without knocking are possible. This paper shows the results of experimental investigations carried out on a heavy duty boosted single cylinder Diesel engine. Based on the indicated cylinder pressure, the combustion process is characterised by performing knock analyses as well as thermodynamic analyses. Furthermore an optically accessible engine has been set up to investigate both the Diesel injection and the combustion process by means of digital high speed imaging. Together with the thermodynamic analyses the results of these optical investigations make up the base for the presented theoretical model of this combined Diesel gasoline combustion process. To show the load potential of this Dual-Fuel-CAI concept, the engine was operated at 2100 1/min with an IMEP of 19 bar. NOx emissions did not exceed 0.027 g/kWh.

Comparisons of particle size distribution from conventional and advanced compression ignition combustion strategies

“…In the heavy-duty engine industry, diesel pilot injection (DPI) is a commonly used dual-fuel combustion strategy that reduces directly injected fuel, and thus PM/ NO x emissions. [19][20][21] The directly injected fuel acts as the ignition source to eliminate the need for a spark plug. DPI utilizes premixed low-reactivity fuel (e.g.…”

“…The stock piston with a reentrant piston bowl was utilized. The literature has shown that PM emission for LTC can be reduced an order of magnitude or more by utilizing optimized piston bowl geometry, 20 but for the purpose of consistency the stock piston was used in the current study. The engine has four valves per cylinder with a dual overhead camshaft valve actuation arrangement.…”

Hybrid-Electric Vehicle with Natural Gas-Diesel Engine

“…Instead of using a spark plug for ignition, the premixed air-gas mixture is ignited with a small amount of directly injected Diesel fuel. Combustion in dual-fuel engines has been studied by various researchers, see for example [5][6][7][8][9][10][11].…”

Diesel-Minimal Combustion Control of a Natural Gas-Diesel Engine

“…This sign change is typical for natural gas-diesel engines [4,7,10]. It can be explained by the strong dilution of the diesel if it is injected very early, which leads to a low local equivalence ratio towards the end of the compression phase and therefore to a longer ignition delay of the diesel [15]. The sign change can also be observed in other dual-fuel engines that use diesel to ignite the mixture, for example, if gasoline or ethanol is used as the primary fuel, see [15] or [16], respectively.…”