Abstract
This study investigates using tailor-developed combustion and air-handling system concepts to achieve high-efficiency, clean gasoline compression ignition (GCI) combustion, aimed at addressing a future heavy-duty ultralow NOx standard of 0.027 g/kWh at the vehicle tailpipe and the tightening CO2 limits around the world by combining GCI with a cost-effective engine aftertreatment system. The development activities were conducted based on a 15 L heavy-duty diesel engine. By taking an analysis-led design approach, a first-generation (Gen1) GCI engine concept was developed and tested, encompassing tailor-designed piston bowl geometry, fuel spray pattern, and swirl motion paired with a customized, fixed-geometry, two-stage turbocharging system and a high-pressure EGR loop with two-stage cooling. Across four key steady-state operating points, the Gen1 GCI concept demonstrated 85–95% lower smoke and 2–3% better diesel-equivalent gross indicated fuel consumption compared to the diesel baseline at 1 g/kWh engine-out NOx. By upgrading to a Gen2 air-handling concept that was composed of a prototype, single-stage, variable-geometry turbocharger and a less restrictive EGR loop, 1D system-level analysis predicted that the pumping mean effective pressure was reduced by 43–54% and the diesel-equivalent brake-specific fuel consumption was improved by 2–4%, thereby demonstrating the performance enhancement potential of refining the air-handling system.
Highlights
The commercial transport sector is facing rising regulatory demand for near-zero criteria pollutants and significantly lower CO2 emissions
The engine performance was clearly sensitive to the engine-out NOx, suggesting that the air-handling system of the base engine that was developed for 4 g/kWh engine-out NOx may not be a good fit for engine operation under substantially lower NOx conditions
When applying the 93 Research octane number (RON) gasoline on the Gen1 engine, the smoke reduction was extended to 90% (Figure 14b), while the ISFCg-D benefit was enhanced to 2.8% (Figure 14d) through the custom-designed partially premixed compression ignition (PPCI)–diffusion combustion process
Summary
The commercial transport sector is facing rising regulatory demand for near-zero criteria pollutants and significantly lower CO2 emissions. The CO2 emissions standards are tightening around the world [3]. Addressing these challenges is likely to incur increased costs and complexity for commercial engines and aftertreatment systems. Combustion strategies that can cost-effectively enhance the NOx/soot tradeoff while achieving diesel-like or better fuel consumption will be of interest to engine manufacturers. For this purpose, gasoline compression ignition (GCI) has the potential to produce low-engine-out criteria pollutants and high fuel efficiency by harnessing gasoline’s low oxidation reactivity and unique spray behavior to enhance in-cylinder fuel–air mixing
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