Benefits of E85 versus gasoline as low reactivity fuel for an automotive diesel engine operating in reactivity controlled compression ignition combustion mode

Abstract

This work shows the capabilities of E85 fuel to be used as low reactivity fuel in a high compression ratio light-duty diesel engine (17.1:1) running under reactivity controlled compression ignition concept. To do this, experimental steady-state engine maps are obtained in a single-cylinder engine with diesel-E85 fuel combination. The engine mapping was performed following the same procedure used in previous works with other fuel combinations to allow the results comparison. Considering the mechanical and emissions limits imposed during the engine mapping, it was found that with diesel-E85 the combustion concept is limited to the region defined from 2 to 7 bar at 1000 rpm, and from 1.5 to 9 bar indicated mean effective pressure at 3000 rpm. This operating region was satisfied with nitrogen oxides, soot and pressure rise rate levels below 0.4 g/kWh, 0.01 g/kWh and 10 bar/CAD, respectively. The reactivity controlled compression ignition maps with diesel-E85 were obtained taking as reference the total fuel energy used in a previous work to map the engine with diesel-gasoline. The direct comparison of both combustion concepts (diesel-E85 and diesel-gasoline) revealed that E85 allows to extend the engine map around 2 bar indicated mean effective pressure towards the high load region. Moreover, the minimum load achieved at high engine speeds was decreased down to 1.5 indicated mean effective pressure. Finally, the differences in terms of emissions and performance between both reactivity controlled compression ignition concepts are highlighted by doing the difference between the maps of several variables.

Fuel consumption and engine-out emissions estimations of a light-duty engine running in dual-mode RCCI/CDC with different fuels and driving cycles

“…The two dual-mode concepts studied combine CDC and RCCI combustion regimes to cover the whole engine map. The unique difference between them is the LRF used under RCCI, gasoline [38] or E85 [39]. In both cases, the HRF used is diesel EN590.…”

“…On the other hand, the low load RCCI region is extended with E85 because of its higher oxygen content compared to gasoline. The extra oxygen content with E85 allows using a higher diesel fraction in the low load region without exceeding the soot limitation, which contributes to reduce the HC and CO levels [39]. In both cases, the RCCI region was completed with NOx and soot emissions levels below 0.4 g/kWh and 0.01 g/kWh, respectively.…”

“…The dual-mode concept emerges as strategy to complete the engine map region in which the RCCI operation becomes critical either for excessive HC and CO emissions (low load) or MPRR and P max (high load) [38]. This is done by switching to another combustion mode, typically CDC if a high CR is used [39]. From the technological standpoint, the modifications needed on the engine architecture to implement the dual-mode RCCI/CDC can be only justified if the aftertreatment necessities are reduced and the fuel economy is improved versus single CDC.…”

Potential of RCCI Series Hybrid Vehicle Architecture to Meet the Future CO2 Targets with Low Engine-Out Emissions

“…Some approaches have been investigated to overcome these issues and complete the engine map whenever the RCCI is unable to run properly. The low level of geometric and hardware modifications allow switching the combustion mode to, typically, CDC [32]. Nonetheless, such a strategy is difficult to justify from a technological standpoint.…”

Experimental investigation on RCCI heat transfer in a light-duty diesel engine with different fuels: Comparison versus conventional diesel combustion

“…Recent studies investigated the use of E85 as LRF fuel for RCCI, reporting better or worse indicated efficiencies than using gasoline fuel depending on the operating conditions [48]. In order to understand the main reasons for this difference, a comparison of the energy usage with both fuels at a matched load and CA50 condition is performed in this subsection.…”