Performance Evaluation of Dedicated EGR on a 12 L Natural Gas Engine

Fueling a compression-ignition engine with premixed natural gas offers the potential to combine a clean-burning, low-carbon fuel with a high compression ratio, high-efficiency engine. This work describes the development of a multi-cylinder 6.7 L diesel engine converted to run stoichiometric diesel micro-pilot/ natural gas premix combustion with a maximum diesel contribution target of 5% of the total fuel energy and a three-way catalyst aftertreatment system. Results are given by comparing the stoichiometric combustion to the diesel baseline operation, showing combustion characteristics differences, including the rapid two stage heat release. A high load output of 23 bar brake mean effective pressure was obtained with diesel-like brake thermal efficiency of 41%. This operating condition enabled a brake specific CO2 emissions reduction of up to 25% when compared to diesel. It was observed that the low load output is limited by combustion stability when operated at stoichiometric condition. The three-way catalyst is observed to run at peak efficiency with an equivalence ratio of 1.01. Injector fouling was observed through the inspection of the nozzle and its internal parts, indicating carbon build-up similar to that seen in injector coking mechanisms. A comparison of the developed engine to other engine technologies is given, showing that the diesel micro-pilot natural gas engine performance is in good standing among other diesel and gas engines in the market.

Section: Resultsmentioning

confidence: 99%

Development of a medium-duty stoichiometric diesel micro-pilot natural gas engine

Vinhaes

Yang

McTaggart-Cowan

et al. 2022

“…Currently, research on fuel reforming to improve engine performance mostly focuses on in-cylinder thermochemical reforming and fuel steam reforming. [25][26][27][28][29][30] In-cylinder thermochemical reforming is the process of circulating reformed gas from the reformer cylinder under rich combustion conditions to other cylinders via EGR. 25,26 The reforming cylinder cycle to cycle variation usually increases when the engine is running at a low load because of the rich combustion state of the reforming cylinder.…”

Section: Introductionmentioning

confidence: 99%

“…[25][26][27][28][29][30] In-cylinder thermochemical reforming is the process of circulating reformed gas from the reformer cylinder under rich combustion conditions to other cylinders via EGR. 25,26 The reforming cylinder cycle to cycle variation usually increases when the engine is running at a low load because of the rich combustion state of the reforming cylinder. 26 The thermal efficiency of natural gas engines also can be improved by steam fuel reforming.…”

Section: Introductionmentioning

confidence: 99%

Effects of excess air ratio and spark timing on performance and gaseous pollutant emissions of fuel reforming natural gas engine

Zheng

Zhou

Zheng

et al. 2022

The combustion and emission characteristics as well as the economic performance of partial oxidation fuel reforming (POFR) natural gas engines were investigated by adjusting the fuel reforming ratios and the engine load. The performance of the POFR engine with a 12% fuel reforming ratio was compared with that of the original engine. The results showed that the fuel-partial-reforming was effective in reducing the cycle-to-cycle variations over the whole range of the operating conditions. The THC and NOX emissions decreased at almost all operating conditions, but showed different decreasing trends at different loads and equivalence ratios, while the CO emissions increased at all operating conditions. It was found that reducing the advancement of ignition timing of the POFR-engine can further reduce the gaseous pollutant emissions without reducing the economic performance of the engine. In conclusion, blending reforming gas improved the overall performance of the natural gas engine at low to medium load conditions.

“…Two publications, one by Van Roekel et al 13 and another by Mitchell and Kocsis 20 have demonstrated dedicated EGR implemented on multi-cylinder natural gas engines. The work by Mitchell and Kocsis 20 was done on a 6-cylinder, 12 L Cummins ISX G engine. Two of the six cylinders were designated as ‘dedicated’ cylinders for a nominal 33% EGR rate.…”

Section: Introductionmentioning

confidence: 99%

“…Further fundamental work by SWRi focused on fuel anti-knock index in an engine equipped with dedicated EGR 19 and characterizing engine performance as the composition of recirculated exhaust gases is changed. 10 Two publications, one by Van Roekel et al 13 and another by Mitchell and Kocsis 20 have demonstrated dedicated EGR implemented on multi-cylinder natural gas engines. The work by Mitchell and Kocsis 20 was done on a 6-cylinder, 12 L Cummins ISX G engine.…”

Section: Introductionmentioning

confidence: 99%

Response surface method optimization of a natural gas engine with dedicated exhaust gas recirculation

Roekel

Montgomery

Singh

et al. 2021

Stoichiometric industrial natural gas engines rely on robust design to achieve consumer driven up-time requirements. Key to this design are exhaust components that are able to withstand high combustion temperatures found in this type of natural gas engine. The issue of exhaust component durability can be addressed by making improvements to materials and coatings or decreasing combustion temperatures. Among natural gas engine technologies shown to reduce combustion temperature, dedicated exhaust gas recirculation (EGR) has limited published research. However, due to the high nominal EGR rate it may be a technology useful for decreasing combustion temperature. In previous work by the author, dedicated EGR was implemented on a Caterpillar G3304 stoichiometric natural gas engine. Examination of combustion statistics showed that, in comparison to a conventional stoichiometric natural gas engine, operating with dedicated EGR requires adjustments to the combustion recipe to achieve acceptable engine operation. This work focuses on modifications to the combustion recipe necessary to improve combustion statistics such as coefficient of variance of indicated mean effective pressure (COV of IMEP), cylinder-cylinder indicated mean effective pressure (IMEP), location of 50% mass fraction burned, and 10%–90% mass fraction burn duration. Several engine operating variables were identified to affect these combustion statistics. A response surface method (RSM) optimization was chosen to find engine operating conditions that would result in improved combustion statistics. A third order factorial RSM optimization was sufficient for finding optimized operating conditions at 3.4 bar brake mean effective pressure (BMEP). The results showed that in an engine with a low turbulence combustion chamber, such as a G3304, optimized combustion statistics resulted from a dedicated cylinder lambda of 0.936, spark timing of 45° before top dead center (°bTDC), spark duration of 365 µs, and intake manifold temperature of 62°C. These operating conditions reduced dedicated cylinder COV of IMEP by 10% (absolute) and the difference between average stoichiometric cylinder and dedicated cylinder IMEP to 0.19 bar.