Equilibrium Chemistry Calculations for Assessment of NOx Abatement Strategies in IC Engines

2011 ◽  
Author(s):  
S. M. Aithal
Keyword(s):  
Natural Gas ◽  
Temporal Variation ◽  
Nox Reduction ◽  
Air Separation ◽  
Working Fluid ◽  
Nitrogen Enrichment ◽  
Nox Formation ◽  
Modeling Tools ◽  
Natural Gas Engines ◽  
Crank Angle

Nitrogen Enriched Air (NEA) has shown great potential in NOx reduction without the drawbacks of exhaust gas recirculation (EGR). Use of NEA in stationary natural gas engines has shown up to 70% NOx reduction with a modest 2% nitrogen enrichment. However, nitrogen enrichment beyond a point leads to degradation in engine performance in terms of power density, brake thermal efficiency and unburned hydrocarbons. Optimizing the nitrogen enrichment levels to reduce NOx without performance degradation of the engine would greatly benefit the advancement of the air separation membrane technology. Development of fast and robust modeling tools to compute the temporal variation of the incylinder engine pressure, temperature and NOx formation can aid experimental efforts in determining the optimum enrichment levels for a given engine operating condition. This work presents a methodology to compute engine-out NOx for engines with and without nitrogen enrichment. Temporal variation of in-cylinder engine pressure and temperature can be obtained by a solution of the energy equation. Using these temperature and pressure values, along with the instantaneous composition of the working fluid, one can evaluate the equilibrium concentration of the combustion products. Since the NOx formation freezes a few crank angle degrees after the completion of combustion, it is instructive to examine whether the equilibrium computation can provide a reasonable estimate of engine-out NOx. To this end, engine-out NOx computed by using the above-mentioned procedure was obtained as a function of equivalence ratio for cases with nitrogen enrichment of 2% and no nitrogen enrichment. The results showed that the equilibrium NOx concentrations a few crank angle degrees after end of combustion were close to those reported experimentally in stationary natural gas engines. These results suggest that it would be possible to use equilibrium chemistry computations to evaluate various NOx mitigation strategies.

Low Temperature Combustion Using Nitrogen Enrichment to Mitigate NOx From Large Bore Natural Gas Fueled Engines

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Munidhar S. Biruduganti ◽  
Sreenath B. Gupta ◽  
Raj Sekar
Keyword(s):  
Low Temperature ◽  
Natural Gas ◽  
Power Density ◽  
Nox Reduction ◽  
Air Separation ◽  
Nitrogen Enrichment ◽  
Nox Emissions ◽  
Low Temperature Combustion ◽  
Lean Burn ◽  
Temperature Combustion

Low temperature combustion is identified as one of the pathways to meet the mandatory ultra low NOx emissions levels set by the regulatory agencies. Exhaust gas recirculation (EGR) is a well known technique to realize low NOx emissions. However, EGR has many built-in adverse ramifications that negate its advantages in the long term. This paper discusses nitrogen enrichment of intake air using air separation membranes as a better alternative to the mature EGR technique. This investigation was undertaken to determine the maximum acceptable level of nitrogen enrichment of air for a single-cylinder spark-ignited natural gas engine. NOx reduction as high as 70% was realized with a modest 2% nitrogen enrichment while maintaining power density and simultaneously improving fuel conversion efficiency (FCE). Any enrichment beyond this level degraded engine performance in terms of power density, FCE, and unburned hydrocarbon emissions. The effect of ignition timing was also studied with and without N2 enrichment. Finally, lean burn versus stoichiometric operation utilizing nitrogen enrichment was compared. Analysis showed that lean burn operation along with nitrogen enrichment is one of the effective pathways for realizing better FCE and lower NOx emissions.

Performance of a Natural Gas Engine Using Variable Air Composition

2005 ◽  
Author(s):  
Munidhar S. Biruduganti ◽  
Sreenath B. Gupta ◽  
Steve McConnell ◽  
Raj Sekar
Keyword(s):  
Natural Gas ◽  
Nox Reduction ◽  
Air Separation ◽  
The Other ◽  
Polymeric Membrane ◽  
Nitrogen Enrichment ◽  
Nox Emissions ◽  
Ignition Timing ◽  
Other Hand ◽  
Separation Membrane

A comparative analysis of nitrogen and oxygen enriched combustion is presented in this paper. Nitrogen enrichment of intake air is proposed as an alternative to Exhaust Gas Recirculation (EGR). NOx reduction by EGR is not very promising due to engine reliability concerns and increased maintenance costs. Air separation membrane, on the other hand, is a potential strategy for NOx reduction due to uncompromised reliability of engine performance. Oxygen-rich and nitrogen-rich streams are produced by passing air through a nonporous polymeric membrane. Nitrogen Enriched Air (NEA) reduces NOx formation by lowering in-cylinder combustion temperatures but with a compromise in Fuel Conversion Efficiency (FCE). However, advanced ignition timing improves FCE considerably. Oxygen Enriched Air (OEA), on the other hand, improves FCE due to the availability of extra oxygen for better combustion which results in higher bulk gas temperatures and NOx emissions. This behavior could be controlled by retarding the ignition timing. Experimental results of nitrogen and oxygen enriched combustion of a Kohler M12 generator (converted to operate with natural gas) is presented in this paper. A 68% reduction in NOx and a 0.8% drop in FCE were observed at −30 ATDC ignition timing (IT) with 2.1% N2 enrichment (40 slpm). A 9% O2 enrichment (40 slpm) at −30 ATDC IT improved FCE by 1% but with higher NOx emissions. The increase in NOx emissions was minimal with a 2% improvement in FCE at −10 ATDC IT and 9% O2 enrichment (40 slpm). Some of the drawbacks encountered were engine misfire at higher concentrations of nitrogen enriched air and retarded ignition timing resulting in poor FCE. This paper discusses both the approaches and highlights the benefits of nitrogen enrichment using an air separation membrane over its counterpart for NOx reduction.

Low Temperature Combustion Using Nitrogen Enrichment to Mitigate NOx From Large Bore Gas-Fueled Engines

2008 ◽  
Author(s):  
Munidhar S. Biruduganti ◽  
Sreenath B. Gupta ◽  
Raj Sekar
Keyword(s):  
Low Temperature ◽  
Power Density ◽  
Nox Reduction ◽  
Engine Performance ◽  
Air Separation ◽  
Nitrogen Enrichment ◽  
Nox Emissions ◽  
Low Temperature Combustion ◽  
Lean Burn ◽  
Temperature Combustion

Low Temperature Combustion (LTC) is identified as one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. This phenomenon can be realized by utilizing various advanced combustion control strategies. The present work discusses nitrogen enrichment using an Air Separation Membrane (ASM) as a better alternative to the mature Exhaust Gas Re-circulation (EGR) technique currently in use. A 70% NOx reduction was realized with a moderate 2% nitrogen enrichment while maintaining power density and simultaneously improving Fuel Conversion Efficiency (FCE). The maximum acceptable Nitrogen Enriched Air (NEA) in a single cylinder spark ignited natural gas engine was investigated in this paper. Any enrichment beyond this level degraded engine performance both in terms of power density and FCE, and unburned hydrocarbon (UHC) emissions. The effect of ignition timing was also studied with and without N2 enrichment. Finally, lean burn versus stoichiometric operation utilizing NEA was compared. Analysis showed that lean burn operation along with NEA is one of the effective pathways for realizing better FCE and lower NOx emissions.

CFD Modeling of NOx Reduction Technologies in Utility Boilers

2000 ◽  
Author(s):  
Marc A. Cremer ◽  
Bradley R. Adams ◽  
David H. Wang ◽  
Michael P. Heap
Keyword(s):  
Nox Reduction ◽  
Electric Utility ◽  
Cfd Modeling ◽  
Nox Formation ◽  
Modeling Tools ◽  
Chemical Mechanisms ◽  
Utility Boilers ◽  
Clean Air ◽  
Nox Control ◽  
Selective Noncatalytic Reduction

Abstract This paper discusses the development and application of CFD modeling tools that have been utilized to assess and design NOx reduction systems that are currently being evaluated by the electric utility industry. Stringent limits on NOx emissions have been imposed by the Clean Air Act Amendments, and a number of NOx reduction technologies are available to help meet these limits including selective noncatalytic reduction (SNCR) and reburning, as well as various combinations of these. This paper discusses the development and implementation of global and reduced chemical mechanisms for NOx formation/destruction into a comprehensive CFD code so that these various options for NOx control can be evaluated. Also, some examples showing the application of these tools to full-scale utility boilers utilizing low-NOx burners, air staging, and SNCR are presented.

NOx Emissions Reduction Using Air Separation Membranes for Different Loads in Gas-Fired Engines

2009 ◽  
Author(s):  
Munidhar Biruduganti ◽  
Sreenath Gupta ◽  
Bipin Bihari ◽  
Raj Sekar
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Nox Reduction ◽  
Engine Performance ◽  
Air Separation ◽  
Nox Emissions ◽  
Low Temperature Combustion ◽  
Lean Burn ◽  
Gas Combustion ◽  
Separation Membranes

Air Separation Membranes (ASM) could potentially replace Exhaust Gas Recirculation (EGR) technology in engines due to the proven benefits in NOx reduction but without the drawbacks of EGR. Previous investigations of Nitrogen Enriched Air (NEA) combustion using nitrogen bottles showed up to 70% NOx reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single cylinder spark ignited natural gas engine. Low Temperature Combustion (LTC) is one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA for different engine loads. Enrichment beyond this level degraded engine performance in terms of power density, Brake Thermal Efficiency (BTE), and unburned hydrocarbon (UHC) emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. The parasitic loss associated with the usage of ASM technology is presented. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio (Ψ) increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA could pave the pathway for realizing lower NOx emissions with a slight penalty in BTE.

Air Separation Membranes: An Alternative to EGR in Large Bore Natural Gas Engines

2009 ◽  
Author(s):  
Munidhar Biruduganti ◽  
Sreenath Gupta ◽  
Bipin Bihari ◽  
Steve McConnell ◽  
Raj Sekar
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Nox Reduction ◽  
Engine Performance ◽  
Air Separation ◽  
Nox Emissions ◽  
Low Temperature Combustion ◽  
Lean Burn ◽  
Gas Combustion ◽  
Separation Membranes

Air Separation Membranes (ASM) could potentially replace Exhaust Gas Recirculation (EGR) technology in engines due to the proven benefits in NOx reduction but without the drawbacks of EGR. Previous investigations of Nitrogen Enriched Air (NEA) combustion using nitrogen bottles showed up to 70% NOx reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single cylinder spark ignited natural gas engine. Low Temperature Combustion (LTC) is one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA. Enrichment beyond this level degraded engine performance in terms of power density, Brake Thermal Efficiency (BTE), and unburned hydrocarbon (UHC) emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. Subsequently, conventional spark ignition (SI) was replaced by laser ignition (LI) to extend lean ignition limit. Both ignition systems were studied under a wide operating range from ψ: 1.0 to the lean misfire limit. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio (Ψ) increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA and alternative ignition source such as LI could pave the pathway for realizing lower NOx emissions with a slight penalty in BTE.

Air Separation Membranes: An Alternative to EGR in Large Bore Natural Gas Engines

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Munidhar Biruduganti ◽  
Sreenath Gupta ◽  
Bipin Bihari ◽  
Steve McConnell ◽  
Raj Sekar
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
Nox Reduction ◽  
Engine Performance ◽  
Air Separation ◽  
Nox Emissions ◽  
Low Temperature Combustion ◽  
Lean Burn ◽  
Gas Combustion ◽  
Separation Membranes

Air separation membranes (ASMs) could potentially replace exhaust gas recirculation (EGR) technology in engines due to the proven benefits in NOx reduction but without the drawbacks of EGR. Previous investigations of nitrogen-enriched air (NEA) combustion using nitrogen bottles showed up to 70% NOx reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single-cylinder spark-ignited natural gas engine. Low temperature combustion is one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA. Enrichment beyond this level degraded engine performance in terms of power density, brake thermal efficiency (BTE), and unburned hydrocarbon emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. Subsequently, conventional spark ignition was replaced by laser ignition (LI) to extend lean ignition limit. Both ignition systems were studied under a wide operating range from ψ:1.0 to the lean misfire limit. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio (Ψ) increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA and alternative ignition source, such as LI, could pave the pathway for realizing lower NOx emissions with a slight penalty in BTE.

Nitrogen Enriched Combustion of a Natural Gas Engine to Reduce NOx Emissions

2004 ◽  
Author(s):  
Munidhar S. Biruduganti ◽  
Sreenath B. Gupta ◽  
Steven McConnell ◽  
Raj Sekar
Keyword(s):  
Natural Gas ◽  
Nox Reduction ◽  
Nitrogen Enrichment ◽  
Nox Emissions ◽  
Ignition Timing ◽  
Engine Operation ◽  
Natural Gas Engine ◽  
Full Load ◽  
Spark Timing ◽  
Gas Recirculation

Nitrogen enrichment of intake air is proposed as an alternative to Exhaust Gas Recirculation (EGR). Experimental results of nitrogen enriched combustion of a Kohler M12 engine (converted to operate with natural gas) are presented in this paper. A 70% reduction in NOx emissions was observed at full load (4 kW) and ignition timing (IT) equal to −20 ATDC with 2.1% NO2 enrichment (40 slpm). However, NOx reduction was minimal at lower loads. The effect of spark or ignition timing along with nitrogen enrichment is also reported for full load. It is recognized that advancing the ignition timing from conventional values has more advantages than retarding the same. A 68% reduction in NOx and a 0.8% drop in Fuel Conversion Efficiency (FCE) were observed at −30 ATDC ignition timing. However, the maximum ignition timing advance with stable engine operation was limited to −40 ATDC. Some of the drawbacks encountered were engine misfire at higher concentrations of nitrogen-rich air and retarded spark timing resulting in poor FCE.

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