Demonstration of Better than Diesel Efficiency and Soot Emissions using Gasoline Compression Ignition in a Light Duty Engine with a Fuel Pressure Limitation

Compression-ignition (CI) engines can produce higher thermal efficiency (TE) and thus lower carbon dioxide (CO2) emissions than spark-ignition (SI) engines. Unfortunately, the overall fuel economy of CI engine vehicles is limited by their emissions of nitrogen oxides (NOx) and soot, which must be mitigated with costly, resource- and energy-intensive aftertreatment. NOx and soot could also be mitigated by adding premixed gasoline to complement the conventional, non-premixed direct injection (DI) of diesel fuel in CI engines. Several such “dual-fuel” combustion modes have been introduced in recent years, but these modes are usually studied individually at discrete conditions. This paper introduces a mapping system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. This system includes the conventional diesel combustion (CDC) and conventional dual-fuel (CDF) modes; the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a previously discovered but relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. Tests show that dual-fuel CI engines can simultaneously increase TE and lower NOx and/or soot emissions at high loads through the use of Partial HCCI (PHCCI). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NOx and/or soot emissions, albeit at slightly lower TE. These results lead to a “partial dual-fuel” multi-mode strategy of PHCCI at high loads and CDC at low loads, linked together by PDFC. Drive cycle simulations show that this strategy, when tuned to balance NOx and soot reductions, can reduce engine-out CO2 emissions by about 1% while reducing NOx and soot by about 20% each with respect to CDC. This increases emissions of unburnt hydrocarbons (UHC), still in a treatable range (2.0 g/kWh) but five times as high as CDC, requiring changes in aftertreatment strategy.

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INITIAL RESULTS ON A NEW LIGHT-DUTY 2.7L OPPOSED-PISTON GASOLINE COMPRESSION IGNITION MULTI-CYLINDER ENGINE

Journal of Energy Resources Technology ◽

10.1115/1.4053518 ◽

2022 ◽

pp. 1-8

Author(s):

Ashwin Salvi ◽

Reed Hanson ◽

Rodrigo Zermeno ◽

Gerhard Regner ◽

Mark Sellnau ◽

...

Keyword(s):

Pressure Rise ◽

Cost Effective ◽

Combustion Noise ◽

Combustion Stability ◽

Residual Fraction ◽

Compression Ignition ◽

Light Duty ◽

Peak Cylinder Pressure ◽

Near Term ◽

Initial Results

Abstract Gasoline compression ignition (GCI) is a cost-effective approach to achieving diesel-like efficiencies with low emissions. The fundamental architecture of the two-stroke Achates Power Opposed-Piston Engine (OP Engine) enables GCI by decoupling piston motion from cylinder scavenging, allowing for flexible and independent control of cylinder residual fraction and temperature leading to improved low load combustion. In addition, the high peak cylinder pressure and noise challenges at high-load operation are mitigated by the lower BMEP operation and faster heat release for the same pressure rise rate of the OP Engine. These advantages further solidify the performance benefits of the OP Engine and emonstrate the near-term feasibility of advanced combustion technologies, enabled by the opposed-piston architecture. This paper presents initial results from a steady state testing on a brand new 2.7L OP GCI multi-cylinder engine designed for light-duty truck applications. Successful GCI operation calls for high compression ratio, leading to higher combustion stability at low-loads, higher efficiencies, and lower cycle HC+NOX emissions. Initial results show a cycle average brake thermal efficiency of 31.7%, which is already greater than 11% conventional engines, after only ten weeks of testing. Emissions results suggest that Tier 3 Bin 160 levels can be achieved using a traditional diesel after-treatment system. Combustion noise was well controlled at or below the USCAR limits. In addition, initial results on catalyst light-off mode with GCI are also presented.

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Effects of the injection parameters on the premixed charge compression ignition combustion and the emissions in a heavy-duty diesel engine

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407017701023 ◽

2017 ◽

Vol 231 (7) ◽

pp. 915-926 ◽

Cited By ~ 2

Author(s):

Yingying Lu ◽

Wanhua Su

Keyword(s):

Single Injection ◽

Hydrocarbon Emissions ◽

Injection Timing ◽

Compression Ignition ◽

Crank Angle ◽

Heavy Duty Diesel Engine ◽

Soot Emissions ◽

Heavy Duty Diesel ◽

Compression Ignition Combustion ◽

Dead Centre

Numerous combustion strategies have been suggested for compression ignition engines in order to meet the stringent emission regulations with minimal sacrifice in the fuel economy. Premixed charge compression ignition combustion has the potential to reduce the nitrogen oxide emissions and the soot emissions while maintaining a high thermal efficiency and has become the research focus recently. Experiments and simulations were used to study the effects of the injection mode and the injection timing on the premixed charge compression ignition combustion and the emissions in a heavy-duty diesel engine at low and medium loads. The results reveal the following. At low loads, when the injection timing of a single injection is 35° crank angle before top dead centre because of the impinging position of the spray, the mixture is divided into two parts: the fuel above the chamber and the fuel in the piston bowl. This helps to utilize fully the in-cylinder air to form a homogeneous mixture. Also the nitrogen oxide emissions are the lowest. At medium loads, with a single injection, the injection mass is increased, the injection duration is prolonged and the mixing timing is reduced. As a result, the soot emissions, the carbon monoxide emissions and the unburned hydrocarbon emissions are increased dramatically; the best emissions are gained at an injection timing of 35° crank angle before top dead centre owing to the combined effect of the optimized mixing time and the optimized mixing space. At medium loads, with multiple injections, the injection mass is divided into four pulses, the mixing timings of which are all increased. The mixing space of the fuel–air mixture is also improved, and a more homogeneous mixture is obtained, which is beneficial to decreasing the soot emissions, the carbon monoxide emissions and the unburned hydrocarbon emissions in comparison with those for the single-injection case. When the injection timings of multiple injections are 80° crank angle before top dead centre, 65° crank angle before top dead centre, 50° crank angle before top dead centre and 35° crank angle before top dead centre, the best trade-off between the performance and the emissions can be achieved at medium loads.

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