Knock and Combustion Characteristics of CH4, CO, H2 and Their Binary Mixtures

Li, Hailin; Karim, G. A.; Sohrabi, A.

doi:10.4271/2003-01-3088

Cited by 16 publications

(4 citation statements)

References 16 publications

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“…Rafael and Sher [17] found that H 2 retarded the autoignition of n-butane owing to a reduction in the OH concentration in the second stage of reactions that provides OH for the main combustion stage. Li et al [18] found that the excellent knock resistance property of CO deteriorated significantly with the presence of small amounts of H 2 , CH 4 ,o rH 2 O. Hence, it is not expected that RG will not benefit from the high knocking resistance of dry CO owing to the presence of H 2 O in the recirculated exhaust gases.…”

Section: Previous Researchmentioning

confidence: 99%

Natural gas spark ignition engine efficiency and NO_x emission improvement using extreme exhaust gas recirculation enabled by partial reforming

Hosseini

Checkel

Neill

2008

Proceedings of the Institution of Mechanical Engineers, Part D:

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Natural gas spark ignition engine efficiency and NOx emission improvement using extreme exhaust gas recirculation enabled by partial reforming Hosseini, V.; Checkel, M. D.; Neill, W. S.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en Natural gas spark ignition engine efficiency and NO x emission improvement using extreme exhaust gas recirculation enabled by partial reforming Abstract: Natural-gas (NG), spark ignition (SI) engines have widespread application in the power generation and upstream oil and gas industries. The manufacturers of these engines are being challenged to meet increasingly stringent nitrogen oxide (NO x ) emission regulations without sacrificing fuel conversion efficiency.SI engines may be operated with air-fuel mixtures lean of stoichiometric to achieve higher thermal efficiency and to reduce NO x emissions. Compared with new combustion strategies such as homogeneous charge compression ignition, however, lean SI combustion suffers from a somewhat limited tolerability to mixture dilution and high cyclic variations. Alternatively, NO x emissions may be reduced by using exhaust gas recirculation (EGR) to dilute a stoichiometric air-fuel mixture. This paper investigates the application of reformer gas (RG) to enable a higher mixture dilution of an NG SI engine using EGR.It was found that RG enrichment allows an increase in the EGR dilution of a stoichiometric NG-air mixture from 12 per cent to more than 35 per cent. The optimal level of RG enrichment directly compensates for the combustion phasing retardation effect of EGR. Increasing the RG fraction in the mixture beyond the optimal value adversely affected the combustion process and fuel conversion efficiency. The experimental data suggest that NO x emissions comparable with the forthcoming 2010 US Environmental Protection Agency heavy-duty diesel engine regulations may be achieved using EGR, RG enrichment, and a three-way catalytic converter (TWC).An energy balance showed that there is the potential to increase the overall system fuel conversion efficiency slightly owing to a more optimized combustion process after taking into account the energy losses associated with fuel reforming. The approach of EGR, fuel reforming, and a TWC is suitable for retrofits because it can be accomplished without modifying the engine geometry.

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Section: Previous Researchmentioning

confidence: 99%

Natural gas spark ignition engine efficiency and NO_x emission improvement using extreme exhaust gas recirculation enabled by partial reforming

Hosseini

Checkel

Neill

2008

Proceedings of the Institution of Mechanical Engineers, Part D:

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“…There are still large concentrations of unconverted CH 4 emissions in the exhaust indicating that flame propagation still cannot reach the CNG/air mixture away from the pilot diesel vicinity [8]. This is supported by the emissions of unburned CH 4 observed at low loads especially when the CH 4 concentration in the mixture is low [9]. The increased amounts of CO emissions are from mechanisms similar to Region I and pre-ignition reactions of the CNG/air mixture [8].…”

Section: The Combustion Processmentioning

confidence: 97%

“…The minimum amount of CO emissions indicates complete combustion with the CH 4 emissions able to oxidize almost completely to CO 2 [8]. These results indicate that flame propagation can be improved by increasing CNG concentrations and therefore the fuel/air equivalence ratio [9]. The minimum concentration of CNG homogeneously mixed with air in which flame propagation reaches all of the mixture within the cylinder is considered the flame spread limit [8].…”

Section: The Combustion Processmentioning

confidence: 99%

Investigation of the Dual-Fuel Conversion of a Direct Injection Diesel Engine

Smallwood¹

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Investigation of the Dual-Fuel Conversion of a Direct Injection Diesel Engine John S. Smallwood The transportation sector is the second largest energy-consuming sector in the United States. With heavy-duty vehicles comprising 20% of the sector and petroleum products being used as 93% of the sector's fuel, alternatives fuels continue to be investigated to offset petroleum usage. Natural gas is increasingly being considered as a fuel source due to its abundance in the Marcellus Shale Formation. Compressed natural gas (CNG) is a promising energy source for dual-fuel combustion. It appears to benefit the environment and the economy. With the ability to reduce oxides of nitrogen (NOx) emissions, carbon dioxide (CO 2) emissions, and particulate matter (PM) emissions, dual-fuel operation is environmentally viable. CNG costs less than petroleum derived diesel and would enable the United States to reduce its dependence on oil imports. Thus, dual-fuel operation promises to be economically practical. Dual-fuel operation reduces the amount of diesel fuel used during combustion and replaces it with an energy-equivalent amount of CNG. CNG is injected into the intake air stream during the intake stroke of the dual-fuel converted diesel engine's four-stroke cycle. CNG is utilized as the main energy source while diesel fuel is direct injected to initiate the ignition process due to its compression ignition characteristics. The objective of this work was to investigate dual-fuel combustion characteristics and resultant emissions to determine if the partial replacement of diesel fuel with CNG is an applicable technology in the transportation industry. To fulfill this objective, a dual-fuel capable 2005 Mercedes OM-460LA 12.8 liter engine outfitted with incylinder pressure and exhaust emissions measurement capabilities was operated at steady-state conditions. Combustion characteristics and resultant emissions were compared between the dualfuel and diesel operations. To certify a dual-fuel conversion kit with the Environmental Protection Agency's (EPA's) Clean Alternative Fuel Conversion Program, research and development work was also completed on a 2005 Mack AC-460P 12.0 liter engine. Exhaust emissions were collected over steady-state and transient conditions. In-use operation cost comparisons and fuel efficiencies between dual-fuel operation and diesel-only operation were completed with the certified conversion kit. The combustion characteristics that most affected emission formations were decreased combustion efficiencies (≤ 39.9%) and decreased maximum in-cylinder gas temperatures (≤ 15.2%). With the dual-fuel conversion kit meeting certification requirements, NOx emissions decreased for steady-state (10.1%) and transient (7.29%) operations while PM emissions increased for steady-state (14.2%) operation and decreased for transient (27.4%) operation. CO 2 emissions decreased for steady-state (8.87%) and transient (7.81%) operations while carbon monoxide (CO) emissions increased for steady-state (754%) and transient (836%) operatio...

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“…Therefore, the higher CR, combined with lean operation, permits a more effective utilization of the available fuel energy. Also, lean-burn operation is a cost-effective way to control engine-out emissions in modern SI engines [22,23]. While a three-way catalyst is effective to simultaneously reduce NOx, CO, and HC emissions, it is relatively expensive and requires strict fuel-air control at or near stoichiometric equivalence ratio to work properly [24].…”

Section: Natural Gas Engine Considerationsmentioning

confidence: 99%

Investigation of Combustion Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition Operation

Liu¹

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The conversion of existing diesel engines to natural-gas spark ignition operation by adding a gas injector in the intake manifold for fuel delivery and replacing the diesel fuel injector with a spark plug to initiate and control the combustion process can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. As the conventional diesel combustion chamber (i.e., flat head and bowl-in-piston) creates high turbulence, the engine can operate leaner, which would increase its efficiency and reduce emissions. However, natural gas combustion in such retrofitted engines presents differences compared to that in conventional spark ignited engines. Subsequently, the main goal of this study was to investigate the characteristics of natural gas combustion inside a diesel-like, fast-burn combustion chamber using a unique array of experimental and numerical tools. The experimental platform consisted of a heavy-duty single-cylinder diesel engine converted to natural-gas spark ignition and operated at a low-speed, lean equivalence ratio, and medium-load condition. The engine can also operate in an optical configuration (i.e., the stock piston and cylinder block can be replaced with a see-through piston and an extended cylinder block), which was used to visualize flame behavior. The optical data indicated a thick and fast-propagated flame in the piston bowl but slower flame propagation inside the squish region. In addition, a 3D numerical model of the optical engine was built to better explain the geometry effects. The simulation results suggested that while the region around the spark plug location experienced a moderate turbulence that helped with the ignition process, the interaction of squish, piston motion, and intake swirl created a highly-turbulent environment that favored the fast burn inside the bowl and stabilized the combustion process. However, the squish region experienced a much lower turbulence, which, combined with the reduced temperature and pressure during the expansion stroke and its higher surface-to-volume ratio, reduced the burning velocity and the flame propagation, but also avoided knocking. Consequently, the bowl-in-piston geometry separated the leanburn natural gas combustion into two distinct events. To extend the optical findings, the metal engine configuration was used to investigate the effects of gas composition, spark timing, equivalence ratio, and engine speed on the two-stage combustion. The results suggested that operating conditions controlled the magnitude and phasing of the two combustion events. Moreover, 3D CFD simulations of the metal engine configuration showed that the squish region contained an important mixture fraction that would burn much slower and can increase the phasing separation between the two combustion events to a point that a second peak would appear in the heat release rate. Moreover, the rapidburn event in such an engine was much shorter compared to its traditional definition (i.e., the time in crank angle degrees between the 10% and 90% energy-releas...

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Knock and Combustion Characteristics of CH4, CO, H2 and Their Binary Mixtures

Cited by 16 publications

References 16 publications

Natural gas spark ignition engine efficiency and NO_x emission improvement using extreme exhaust gas recirculation enabled by partial reforming

Natural gas spark ignition engine efficiency and NO_x emission improvement using extreme exhaust gas recirculation enabled by partial reforming

Investigation of the Dual-Fuel Conversion of a Direct Injection Diesel Engine

Investigation of Combustion Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition Operation

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