Experimental Study of the Effect of Start of Injection and Blend Ratio on Single Fuel Reformate RCCI

Abstract

A new concept of single-fuel RCCI has been proposed through the catalytic partial oxidation reformation of diesel fuel. The reformed fuel mixture is then used as the low reactivity fuel and diesel itself is used as the high reactivity fuel. In this paper, two selected reformates mixture from the reformation of diesel were selected for further analysis. Each reformate fuel mixture contained a significant fraction of inert gases (89% and 81%). The effects of the difference in the molar concentrations of the reformate mixtures were studied by experimenting with diesel as the direct injected fuel in RCCI over a varying start of injection timings and different blend ratios (i.e., the fraction of low and high reactivities fuels). The reformate mixture with the lower inert gas concentration had earlier combustion phasing and shorter combustion duration at any given diesel start of injection timing. The higher reactivity separation between reformate mixture and diesel, compared with gasoline and diesel, causes the combustion phasing of reformate-diesel RCCI to be more sensitive to the start of injection timing. The maximum combustion efficiency was found at a CA50 before TDC, whereas the maximum thermal efficiency occurs at a CA50 after TDC. The range of energy-based blend ratios in which reformate-diesel RCCI is possible is between 25% and 45%, limited by ringing intensity (RI) at the low limit of blend ratios, and COV of IMEP and combustion efficiency at the high limit.

Reactivity controlled compression ignition engine: Pathways towards commercial viability

“…While initial RCCI studies were encouraging, further improvements have been undertaken to assess its ability to achieve future emissions reduction and assess its commercialization in automotive, stationary and marine applications (using natural gas-diesel for mid-speed marine engines) [28,29]. These developments are supported by new, single-fuel operation [30][31][32], optimized combustion system [33], variable valve timing [34], and new aftertreatment technologies [35,36]. RCCI combustion engines not only are useful in mobile applications but also they can be used in stationary applications such as power generator, particularly in hybrid configuration combined with fuel cells [37] and electric motors [38].…”

Improving the controllability of partial fuel stratification at low boost levels by applying a double late injection strategy

“…15–17 The downside of this combustion mode is that it requires two distinct fuels and fuel systems, which increases the complexity of operation and maintenance, and also raises the initial engine cost. 18,19 Another combustion mode that has been proposed recently is called thermally stratified compression ignition (TSCI). The heat release control approach in TSCI is based on the in-cylinder temperature stratification that is created by the evaporative cooling from the direct-injected fuel or from the direct injection (DI) of water.…”