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.

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.

Experimental Examination of Prechamber Heat Release in a Large Bore Natural Gas Engine

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Daniel B. Olsen ◽  
Allan T. Kirkpatrick
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Equivalence Ratio ◽  
Dynamic Pressure ◽  
Pressure Rise ◽  
Main Chamber ◽  
Lean Burn ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Common Solution

A common solution in reducing NOx emissions to meet new emission regulations has been lean burn combustion. However, with very lean air∕fuel (A∕F) ratios, both carbon monoxide and hydrocarbon emissions become unacceptably high due to the spark misfiring and combustion instabilities. In order to mitigate this, a prechamber ignition system is often used to stabilize combustion at very lean A∕F ratios. In this paper, the heat release in a retrofit prechamber system installed on a large bore natural gas engine is examined. The heat release analysis is based on dynamic pressure measurements both in the main chamber and prechamber. The Woschni correlation is utilized to model heat transfer. Based on heat release modeling and test data analysis, the following observations are made. Main chamber heat release rates are much more rapid for prechamber ignition compared to spark ignition. During combustion in the prechamber, much of the fuel flows into the main chamber unreacted. About 52% of the mass in the prechamber, at ignition, flows into the main chamber during prechamber combustion. Prechamber total heat release, pressure rise, and maximum jet velocity all increase with increasing prechamber equivalence ratio. Prechamber combustion duration and coefficient of variation of peak pressure are minimized at a prechamber equivalence ratio of about 1.09.

Experimental Examination of Prechamber Heat Release in a Large Bore Natural Gas Engine

2007 ◽  
Author(s):  
Daniel B. Olsen ◽  
Allan T. Kirkpatrick
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Equivalence Ratio ◽  
Laminar Flame ◽  
Dynamic Pressure ◽  
Pressure Rise ◽  
Main Chamber ◽  
Lean Burn ◽  
Gas Engine ◽  
Natural Gas Engine

A common solution to reducing NOX emissions to meet new emissions regulations has been lean burn combustion. However, with very lean air/fuel (A/F) ratios, both carbon monoxide and hydrocarbon emissions become unacceptably high due to spark misfiring and combustion instabilities. In order to mitigate this, a prechamber ignition system is often used to stabilize combustion at very lean A/F ratios. In this paper, the heat release in a retrofit prechamber system installed on a large bore natural gas engine is examined. The heat release analysis is based on dynamic pressure measurements both in the main chamber and prechamber. The Woschni correlation is utilized to model heat transfer. Based on heat release modeling and test data analysis the following observations are made. Main chamber heat release rates are much more rapid for prechamber ignition compared to spark ignition. During combustion in the prechamber much of the fuel flows into the main chamber un-reacted. About 52% of the mass in the prechamber, at ignition, flows into the main chamber during prechamber combustion. Prechamber total heat release, pressure rise, and maximum jet velocity all increase with increasing prechamber equivalence ratio. Prechamber combustion duration and coefficient of variation of peak pressure are minimized at a prechamber equivalence ratio of about 1.09, which corresponds roughly to the equivalence ratio of highest laminar flame speed. The above performance optimum does not correspond to the equivalence ratio where the most prechamber energy is released.

Sign in / Sign up

Export Citation Format

Share Document