Combustion Mode Design with High Efficiency and Low Emissions Controlled by Mixtures Stratification and Fuel Reactivity

Abstract

(2015) Combustion mode design with high efficiency and low emissions controlled by mixtures stratification and fuel reactivity. Front. Mech. Eng. 1:8. doi: 10.3389/fmech.2015.00008 Combustion mode design with high efficiency and low emissions controlled by mixtures stratification and fuel reactivity This paper presents a review on the combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixture stratification that have been conducted in the authors' group, including the charge reactivity controlled homogeneous charge compression ignition (HCCI) combustion, stratification controlled premixed charge compression ignition combustion, and dual-fuel combustion concepts controlled by both fuel reactivity and mixture stratification. The review starts with the charge reactivity controlled HCCI combustion, and the works on HCCI fueled with both high cetane number fuels, such as dimethyl ether and n-heptane, and high octane number fuels, such as methanol, natural gas, gasoline, and mixtures of gasoline/alcohols, are reviewed and discussed. Since single fuel cannot meet the reactivity requirements under different loads to control the combustion process, the studies related to concentration stratification and dual-fuel charge reactivity controlled HCCI combustion are then presented, which have been shown to have the potential to achieve effective combustion control. The efforts of using both mixture and thermal stratifications to achieve the auto-ignition and combustion control are also discussed. Thereafter, both charge reactivity and mixture stratification are then applied to control the combustion process. The potential and capability of thermal-atmosphere controlled compound combustion mode and dual-fuel reactivity controlled compression ignition/highly premixed charge combustion mode to achieve clean and high efficiency combustion are then presented and discussed. Based on these results and discussions, combustion mode design with high efficiency and low emissions controlled by fuel reactivity and mixtures stratification in the whole operating range is proposed.

An Experimental Study of Operating Range, Combustion and Emission Characteristics in an RCCI Engine Fueled with Iso-Propanol/n-Heptane

“…The effects of fuels with different premixed ratios on the in-cylinder pressure, heat release rate (HRR) and integrated heat release (IHR) at an IAT of 50 • C in RCCI combustion mode are shown in Figures 4 and 5. In RCCI, the ignition timing is delayed with the increase in low-reactivity fuel, resulting in a reduction in in-cylinder pressure [48]. When the data obtained at a 2500 rpm engine speed and lambda value of 2.40 are analyzed, it can be stated that the maximum in-cylinder pressure increases with the use of a premixed fuel (PR25) with higher reactivity.…”

Research Directions for Homogenous Charge Combustion Ignition Engine

“…Turbo-charging can be a good option to increase the amount of air available for combustion and volumetric efficiency can also be increased. [22] For RCCI engines, the stable operation can be achieved by high charge reactivity under low load conditions. On the contrary Peak Pressure Rise rate can be suppressed by use of low charge reactivity.…”

“…The early and late direct and port fuel injection strategies have already been discussed in table 1. Reitz et al, Paykani et al and Wang et al[20][21][22] studied the articles related to the development of RCCI engines.…”

Current trends on combustion control methods using fuel reactivities

“…Supplying two fuels which have different combustion characteristics (reactivities) can be used to control the combustion phasing, combustion duration and engine knock [51][52][53]. This is called as Reactivity Controlled Compression Ignition (RCCI), one of the techniques used in HCCI mode.…”

“…High reactive fuel is generally the one that has high cetane number to initiate combustion. Low reactive fuel is being port injected which generally has high octane number to bear the engine compression ratio in order to reduce knock [53]. It was reported that gasoline has high octane number-100 [57] and it can be used as low reactive fuel.…”