Exhaust Gas Recirculation in a Lean-Burn Natural Gas Engine

1998 ◽  
Author(s):  
Sumit Bhargava ◽  
Nigel Clark ◽  
M. Wayne Hildebrand
2019 ◽  
pp. 146808741986473 ◽  
Author(s):  
Chris A Van Roekel ◽  
David T Montgomery ◽  
Jaswinder Singh ◽  
Daniel B Olsen

Due to the market presence that natural gas has and is expected to have in the future energy sector, research and development of novel natural gas combustion strategies to increase power density, lower total emissions, and increase overall efficiency is warranted. Dilution whether by excess air or by exhaust gas recirculation has historically been implemented on diesel, natural gas, and gasoline engines to mitigate various regulated emissions. In the large industrial natural gas engine industry, excess air dilution or ultra-lean-burn operation has afforded lean-burn engines increased power density and reduced NO x emissions. This advance in technology has allowed lean-burn engines to compete in markets such as electrical power generation which previously they had not been able. However, natural gas engines utilizing a non-selective catalytic reduction system or three-way catalyst must operate under stoichiometric conditions and thus are limited in power density by exhaust gas temperatures. In previous gasoline small engine research, a novel exhaust gas recirculation technique called dedicated exhaust gas recirculation was shown to have a positive impact on engine-out emissions of NO x and unburned hydrocarbons while also lowering exhaust component temperatures. This work seeks to understand the consequences of implementing a dedicated exhaust gas recirculation system on a multi-cylinder stoichiometric industrial natural gas engine. The results of this initial evaluation demonstrate reductions in engine-out NO x and CO emissions and improvements in engine-out exhaust gas temperatures with the dedicated exhaust gas recirculation technique. However, in a low-turbulence combustion chamber, dedicated exhaust gas recirculation significantly lowers the overall rate of combustion and results in significant differences in cylinder-to-cylinder combustion.


2021 ◽  
Author(s):  
Scott Bayliff ◽  
Bret Windom ◽  
Anthony Marchese ◽  
Greg Hampson ◽  
Domenico Chiera ◽  
...  

Author(s):  
Hailin Li ◽  
Ghazi A. Karim

A variety of gaseous fuels and a wide range of cooled exhaust gas recirculation (EGR) can be used in turbo-charged spark ignition (S.I.) gas engines. This makes the experimental investigation of the knocking behavior both unwieldy and uneconomical. Accordingly, it would be attractive to develop suitable effective predictive models that can be used to improve the understanding of the roles of various design and operating parameters and achieve a more optimized turbo-charged engine operation, particularly when EGR is employed. This paper presents the simulated performance of a turbo-charged S.I. natural gas engine when employing partially cooled EGR. A two-zone predictive model developed mainly for naturally aspirated S.I. engine applications of natural gas, described and validated earlier, was extended to consider applications employing turbo-chargers, intake charge after-coolers, and cooled EGR. A suitably detailed kinetic scheme involving 155 reaction steps and 39 species for the oxidation of natural gas is employed to examine the pre-ignition reactions of the unburned mixtures that can lead to knock prior to being fully consumed by the propagating flame. The model predicts the onset of knock and its intensity once end gas auto-ignition occurs. The effects of turbo-charging and cooled EGR on the total energy to be released through auto-ignition and its effect on the intensity of the resulting knock are considered. The consequences of changes in the effectiveness of after and EGR-coolers, lean operation and reductions in the compression ratio on engine performance parameters, especially the incidence of knock are examined. The benefits, limitations, and possible penalties of the application of fuel lean operation combined with cooled EGR are also examined and discussed.


Author(s):  
Yoshifuru Nitta ◽  
Dong-Hoon Yoo ◽  
Sumito Nishio ◽  
Yasuhisa Ichikawa ◽  
Koichi Hirata ◽  
...  

The need for reductions of nitrogen oxides (NOx), sulfur oxides (SOx), and carbon dioxide (CO2) emissions has been acknowledged on the global level. However, it is difficult to meet the strengthened emissions regulations by using the conventional marine diesel engines. Therefore, lean burn gas engines have been recently attracting attention in the maritime industry. Because they use natural gas as fuel and can simultaneously reduce both NOx and CO2 emissions. On the other hand, since methane is the main component of natural gas, the slipped methane, which is the unburned methane emitted from the lean burn gas engines, might have a potential impact on global warming. The authors have proposed a combined exhaust gas recirculation (C-EGR) system to reduce the slipped methane from the gas engines and NOx from marine diesel engines by providing the exhaust gas from lean burn gas engine to the intake manifold of the marine diesel engine using a blower. Since the exhaust gas from the gas engine includes slipped methane, this system could reduce both the NOx from the marine diesel engine and the slipped methane from the lean burn gas engine simultaneously. This paper introduces the details of the proposed C-EGR system and presents the experimental results of emissions characteristics on the C-EGR system. As a result, it was confirmed that the C-EGR system attained more than 75% reduction of the slipped methane in the intake gas. Additionally, the NOx emission from the diesel engine decreased with the effect of the exhaust gas recirculation (EGR) system.


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