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Effectiveness of Exhaust Gas Recirculation on Low-Load Combustion Efficiency of a Reactivity Controlled Compression Ignition Engine
Journal Article
04-16-02-0008
ISSN: 1946-3952, e-ISSN: 1946-3960
Sector:
Topic:
Citation:
Khedkar, N. and Sarangi, A., "Effectiveness of Exhaust Gas Recirculation on Low-Load Combustion Efficiency of a Reactivity Controlled Compression Ignition Engine," SAE Int. J. Fuels Lubr. 16(2):81-101, 2023, https://doi.org/10.4271/04-16-02-0008.
Language:
English
Abstract:
Reactivity controlled compression ignition (RCCI) is a potential low-temperature
combustion (LTC) technique for running intrinsically efficient compression
ignition engines while reducing the oxides of nitrogen (NOx) and
particulate matter (PM) emissions. However, poor low-load combustion efficiency
is a major challenge in the RCCI strategy. In this work, a combination of
injection strategy and cold and hot exhaust gas recirculation (EGR) strategies
were investigated to improve the low-load combustion efficiency of a production
light-duty compression ignition engine operating in the gasoline-diesel
dual-fuel RCCI mode. The engine was operated at a low load of 3 bar gross
indicated mean effective pressure and at an engine speed of 1500 rpm with wide
ranges of single and multiple fuel injection strategies. Significant improvement
in combustion efficiency was achieved by targeting the directly injected diesel
fuel in the piston lip region. Multiple fuel injection strategy in which more
than 50% of the diesel fuel was targeted in the squish region was beneficial in
terms of NOx, total hydrocarbon (THC), and soot emissions. RCCI
operation with cold EGR, at the optimum injection timing, resulted in more than
96% reduction in engine-out NOx emissions (<20 ppm, 0.4 g/kWh)
with near-zero soot (0.001 g/kWh) emissions with indicated thermal efficiency
(46%), similar to conventional diesel combustion (CDC). Increasing the
reactivity of the gasoline-air mixture, with the optimum distribution of the
diesel fuel between the piston bowl and squish regions, reduced THC emissions by
75% and carbon monoxide (CO) emissions by 30% and improved the combustion
efficiency by ~25.3% points compared to the baseline dual-fuel operation.