Combustion Analysis of a Natural Gas Engine

2003 ◽  
Author(s):  
Seref Soylu
Keyword(s):  
Natural Gas ◽  
Burning Rate ◽  
Equivalence Ratio ◽  
Operating Conditions ◽  
Engine Fuel ◽  
Ignition Timing ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Rate Analysis ◽  
Propagation Period

A two-zone thermodynamic model was developed for a spark ignition natural gas engine. The model was used to calculate instantaneous mass burning rate and thermodynamic state of burned and unburned zones of the combustion chamber content. Cylinder pressure data was collected at various engine operating conditions. Natural gas and natural gas–propane mixtures were used as engine fuel. From the burning rate analysis various combustion characteristics, such as flame initiation period (FIP) and flame propagation period (FPP) were calculated at various engine operating conditions. It was observed that both the FIP and FPP decrease with increasing equivalence ratio for lean mixtures. While the retarded timing decreases the FIP, the FPP has a tendency to increase. Addition of propane to natural gas reduces the FPP although the FIP is not affected. Unburned and burned gas temperatures are significantly raised with increase in equivalence ratio. However, ignition timing and propane fraction do not influence the temperatures as much as equivalence ratio does.

Performance and Combustion Investigation of a Lean Burn Natural Gas Engine Using CFD

2018 ◽  
Author(s):  
Sridhar Sahoo ◽  
Srinibas Tripathy ◽  
Dhananjay Kumar Srivastava
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Spark Ignition Engine ◽  
Engine Fuel ◽  
Lean Burn ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Spark Timing ◽  
Combustion Duration ◽  
Wide Range

Natural gas is widely used in sequentially port fuel injection engine to meet stringent emission regulation. Lean burn operation is one of the ways to improve spark-ignition engine fuel economy. The instability in the combustion process of the lean burn engine is one of the major challenges for engine research. In this study, the performance and combustion characteristics of a lean burn sequential injection compressed natural gas (CNG) engine were investigated numerically using computational fluid dynamics (CFD) modeling over a wide range of air/fuel equivalence ratio. A detailed chemical kinetic mechanism was used for natural gas combustion along with laminar flame speed model to capture lean burn operating condition within the combustion chamber. Combustion pressure, indicated mean effective pressure (IMEP), and heat release were analyzed for performance analysis, whereas flame development angle (CA 10), combustion duration, thermal efficiency were taken for combustion analysis. The results show that on increasing air/fuel equivalence ratio at a given spark timing, IMEP decreases as the lean burn mixture produces less amount of gross power output due to insufficient available energy. Moreover, lower burning velocity characteristic of natural gas extends the combustion duration, where a substantial amount of total energy released after top dead center. It is also seen that optimum spark timing (MBT) for maximum IMEP advances with an increase in air/fuel equivalence ratio due to late ignition timing under lean burn condition. CFD model successfully captures the effect of dilution to illustrate the considerations to design future combustion engine for spark ignited natural gas engine.

The scavenging timing of pre-chamber on the performance of a natural gas engine

2020 ◽  
pp. 146808742096087
Author(s):  
Xue Yang ◽  
Yong Cheng ◽  
Pengcheng Wang
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Injection System ◽  
Maximum Pressure ◽  
Ignition Process ◽  
Main Chamber ◽  
Ignition Timing ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine

The pre-chamber ignition system scavenged with natural gas can effectively improve the in-cylinder combustion process and extend the lean-burn limit of natural gas engines. The scavenging process affects the flow field and fuel-air mixture concentration distribution in the pre-chamber and affects the combustion process in the pre-chamber as well as the ignition process in the main chamber. This has a significant influence on the performance of natural gas engines. It is supposed that the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing affects the combustion process in the pre-chamber. To verify this suppose, an independent injection system for injecting natural gas into the pre-chamber is designed and experiments are carried out on a single-cylinder natural gas engine. The ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing is adjusted by changing the injection start angle of the scavenging process. The combustion process in the pre-chamber and the main chamber are analyzed using the in-cylinder pressures. The results indicate that, with the delay of the injection start angle, the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing increases, the combustion process in the pre-chamber is enhanced, the maximum pressure difference between two chambers increases and appears earlier. The energy of the hot jets and the penetration of the jets increase, which enhances the combustion process in the main chamber.

Impacts of Ignition and Jet Timing on Natural Gas Engine Start Process

2014 ◽  
Vol 1070-1072 ◽  
pp. 1748-1751
Author(s):  
Bo Wen Zou ◽  
Jing Bo Li ◽  
Jun Gang Liu
Keyword(s):  
Natural Gas ◽  
Engine Speed ◽  
Direct Injection ◽  
Ignition Timing ◽  
Gas Engine ◽  
Idle Speed ◽  
Natural Gas Engine ◽  
Hc Emissions ◽  
Start Process ◽  
Engine Start

Based on modified natural gas direct injection engine, we studied the impacts of ignition timing and jet timing on natural gas engine start process in this paper. The results shows that: when the first jet ignition occurs in the first compression stroke, the engine reaches idle speed 400rpm fastest; as the jet timing is delayed, emissions during engine start is gradually reduced, but when the jet late, HC surge occurs, the emissions deteriorates; with the ignition advance angle increasing, the engine speed growth accelerates, the peak moves forward; with the ignition advance angle increasing, HC emissions peak increases, the peak moves forward.

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

2021 ◽  
pp. 146808742199652
Author(s):  
Chris A Van Roekel ◽  
David T Montgomery ◽  
Jaswinder Singh ◽  
Daniel B Olsen
Keyword(s):  
Natural Gas ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
Effective Pressure ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Indicated Mean Effective Pressure ◽  
Surface Method ◽  
Rsm Optimization ◽  
Gas Recirculation

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.

An Investigation of Lean Combustion in a Natural Gas-Fueled Spark-Ignited Engine

1996 ◽  
Vol 118 (2) ◽  
pp. 145-151 ◽  
Author(s):  
M. Gupta ◽  
S. R. Bell ◽  
S. T. Tillman
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Operating Conditions ◽  
Engine Fuel ◽  
Performance And Emission ◽  
Lean Combustion ◽  
Indicated Mean Effective Pressure ◽  
Light Duty ◽  
Spark Timing ◽  
Transportation Applications

Natural gas has been used extensively as an engine fuel in gas pipeline transmission applications and, more recently, as a fuel for transportation applications including both light-duty and heavy-duty vehicles. The objective of this work was to investigate the performance and emission characteristics of natural gas in an original equipment manufacturer (OEM), light-duty, spark-ignited engine being operated in the lean fueling regime and compare the operation with gasoline fueling cases. Data were acquired for several operating conditions of speed, throttle position, air-fuel equivalence ratio, and spark timing for both fuels. Results showed that for stoichiometric fueling, with a naturally aspirated engine, a power loss of 10 to 15 percent can be expected for natural gas over gasoline fueling. For lean operation, however, power increases can be expected for equivalence ratios below about φ = 0.80 with natural gas fueling as compared to gasoline. Higher brake thermal efficiencies can also be expected with natural gas fueling with maximum brake torque (MBT) timings over the range of equivalence ratios investigated in this work. Coefficient of variation (COV) data based on the indicated mean effective pressure (IMEP) demonstrated that the engine is much less sensitive to equivalence ratio leaning for natural gas fueling as compared to gasoline cases. The lean limit for a COV of 10 percent was about φ = 0.72 for gasoline and φ = 0.63 for natural gas. Lean fueling resulted in significantly reduced NOx levels where a lower plateau for NOx concentrations was reached at φ near or below 0.70, which corresponded to about 220 ppm. For natural gas fueling, this corresponded to about 1.21 gm/(kW-h). Finally, with MBT timings, relatively short heart release durations were obtained for lean fueling with natural gas compared to gasoline.

An Experimental and Theoretical Study of Fuel Composition on Noxious Emissions in a Natural Gas Engine Operating on Wellhead Gas

2015 ◽  
Author(s):  
Stephen Christensen ◽  
Kayode Ajayi ◽  
Duane Abata ◽  
Kevin Carlin
Keyword(s):  
Natural Gas ◽  
Computer Model ◽  
Strong Dependence ◽  
Fuel Composition ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Gas Recovery ◽  
Rate Analysis ◽  
Burn Rate ◽  
Natural Gas Recovery

The use of natural gas in spark-ignited internal combustion engines optimized for minimum emissions has repeatedly shown a significant reduction in exhaust emissions over that of gasoline. Pronounced variations in unprocessed natural gas composition can however present an emissions problem for engines used in natural gas recovery where unrefined wellhead gas is used as the fuel. This study is twofold involving both experimental analysis and theoretical development with a computer model that simulates wellhead gas combustion. On the experimental side, Fourier transform infrared spectroscopy (FTIR) was used to analyze emissions of a 2.4L four-cylinder spark-ignited natural gas engine operating on fuels of varying composition. A comparative assessment is made between CO, NO, THC, CH4, and CH2O emissions of the engine operating on refined pipeline natural gas and those of the engine operating on the same gas with added CO2, N2, and C3H8 diluents. Diluents were added to the fuel individually to isolate the effect of each and to approximate wellhead gas. Additionally, a burn rate analysis was conducted which shows changes in the rate of fuel energy liberation with changes in diluent concentration. On the theoretical side, a two zone computer model of engine operation was developed that would simulate operation of the engine under varying fuel composition as found in various natural gas recovery wells throughout the United States. Results show that exhaust concentrations of NO and THC were strongly affected by addition of both inert and reactive diluent due to their strong dependence on in-cylinder temperature. Emissions of CO, CH4, and CH2O were also found to depend on diluent concentration; however, to a much lesser extent with emissions of CO being seemingly unaffected by addition of N2 for the compositions tested. Burn rate analysis shows that the introduction of inert constituents to the fuel decreases the fuel burn rate while addition of propane increases the burn rate. The whole of the analysis indicates a strong dependence of emissions on fuel composition and that significant potential exists for emissions reduction of engines operating on unprocessed natural gas.

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