Impact of Geometric Compression Ratio and Variable Valve Actuation on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

2021 ◽  
Author(s):  
Yu Zhang ◽  
Praveen Kumar ◽  
Meng Tang ◽  
Yuanjiang Pei ◽  
Brock Merritt ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Compression Ratio ◽  
Compression Ignition ◽  
Heavy Duty ◽  
Variable Valve Actuation ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel ◽  
Variable Valve ◽  
Valve Actuation

Impact of Geometric Compression Ratio and Variable Valve Actuation on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

2020 ◽  
Author(s):  
Yu Zhang ◽  
Praveen Kumar ◽  
Meng Tang ◽  
Yuanjiang Pei ◽  
Brock Merritt ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Premixed Combustion ◽  
Compression Ignition ◽  
Heavy Duty ◽  
Variable Valve Actuation ◽  
Partially Premixed Combustion ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel ◽  
Variable Valve ◽  
Valve Actuation

Abstract Gasoline compression ignition (GCI) is a promising powertrain solution to simultaneously address the increasingly stringent regulation of oxides of nitrogen (NOx) and a new focus on greenhouse gases. GCI combustion benefits from extended mixing times due to the low reactivity of gasoline, but only when held beneath the threshold of the high temperature combustion regime. The geometric compression ratio (GCR) of an engine is often chosen to balance the desire for low NOx emissions while maintaining high efficiency. This work explores the relationship between GCR, variable valve actuation (VVA) and emissions when using GCI combustion strategies. The test article was a Cummins ISX15 heavy-duty diesel engine with an unmodified production air and fuel system. The test fuel was an ethanol-free gasoline with a market-representative research octane number (RON) of 91.4–93.2. In the experimental investigation at 1375 rpm/10 bar BMEP, three engine GCRs were studied, including 15.7, 17.3, and 18.9. Across the three GCRs, GCI exhibited a two-stage combustion process enabled through a split injection strategy. When keeping both NOx and CA50 constant, varying GCR from 15.7 to 18.9 showed only a moderate impact on engine brake thermal efficiency (BTE), while its influence on smoke was pronounced. At a lower GCR, a larger fraction of fuel could be introduced during the first injection event due to lower charge reactivity, thereby promoting partially-premixed combustion and reducing smoke. Although increasing GCR increased gross indicated thermal efficiency (ITEg), it was also found to cause higher energy losses in friction and pumping. In contrast, GCI performance showed stronger sensitivity towards EGR rate variation, suggesting that air-handling system development is critical for enabling efficient and clean low NOx GCI combustion. To better utilize gasoline’s lower reactivity, an analysis-led variable valve actuation investigation was performed at 15.7 GCR and 1375 rpm/10 bar BMEP. The analysis was focused on using an early intake valve closing (EIVC) approach by carrying out closed-cycle, 3-D CFD combustion simulations coupled with 1-D engine cycle analysis. EIVC was shown to be an effective means to lengthen ignition delay and promote partially-premixed combustion by lowering the engine effective compression ratio (ECR). By combining EIVC with a tailored fuel injection strategy and properly developed thermal boundary conditions, simulation predicted a 2.3% improvement in ISFC and 47% soot reduction over the baseline IVC case while keeping NOx below the baseline level.

Full-Load HCCI Operation with Variable Valve Actuation System in a Heavy-Duty Diesel Engine

2007 ◽  
Author(s):  
Yuuichi Kodama ◽  
Izumi Nishizawa ◽  
Takumi Sugihara ◽  
Norihiko Sato ◽  
Tadashi Iijima ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Heavy Duty ◽  
Full Load ◽  
Variable Valve Actuation ◽  
Actuation System ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel ◽  
Variable Valve ◽  
Valve Actuation

A Computational Investigation of Piston Bowl Geometry and Injector Spray Pattern Effects on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

2019 ◽  
Author(s):  
Yu Zhang ◽  
Yuanjiang Pei ◽  
Meng Tang ◽  
Michael Traver
Keyword(s):  
Diesel Engine ◽  
Fuel Efficiency ◽  
Compression Ignition ◽  
Swirl Ratio ◽  
Heavy Duty ◽  
Load Range ◽  
Spray Pattern ◽  
Piston Bowl ◽  
Heavy Duty Diesel Engine ◽  
Heavy Duty Diesel

Abstract This study computationally investigates the potential of utilizing gasoline compression ignition (GCI) in a heavy-duty diesel engine to address a future ultra-low tailpipe NOx standard of 0.027 g/kWh while achieving high fuel efficiency. By conducting closed-cycle, full-geometry, 3-D computational fluid dynamics (CFD) combustion simulations, the effects of piston bowl geometry, injector spray pattern, and swirl ratio (SR) were investigated for a market gasoline. The simulations were performed at 1375 rpm over a load range from 5 to 15 bar BMEP. The engine compression ratio (CR) was increased from 15.7 used in previous work to 16.5 for this study. Two piston bowl concepts were studied with Design 1 attained by simply scaling from the baseline 15.7 CR piston bowl, and Design 2 exploring a wider and shallower combustion chamber design. The simulation results predicted that through a combination of the wider and shallower piston bowl design, a 14-hole injector spray pattern, and a swirl ratio of 1, Design 2 would lead to a 2–7% indicated specific fuel consumption (ISFC) improvement over the baseline by reducing the spray-wall interactions and lowering the in-cylinder heat transfer loss. Design 1 (10-hole and SR2) showed a more moderate ISFC reduction of 1–4% by increasing CR and the number of nozzle holes. The predicted fuel efficiency benefit of Design 2 was found to be more pronounced at low to medium loads.

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