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.

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 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.

Strategies for Reduced NOx Emissions in Pilot-Ignited Natural Gas Engines

2002 ◽  
Author(s):  
Sundar R. Krishnan ◽  
Kalyan K. Srinivasan ◽  
Weidong Gong ◽  
Scott Fiveland ◽  
Satbir Singh ◽  
...  
Keyword(s):  
Natural Gas ◽  
Fuel Injection ◽  
Nox Reduction ◽  
Engine Performance ◽  
Injection Timing ◽  
Nox Emissions ◽  
Pilot Injection ◽  
Engine Operation ◽  
Performance And Emissions ◽  
Inlet Conditions

The performance and emissions of a single-cylinder, natural gas fueled engine using a pilot ignition strategy have been investigated. Small diesel pilots (2–3 percent on an energy basis), when used to ignite homogeneous natural gas-air mixtures, are shown to possess the potential for reduced NOx emissions while maintaining good engine performance. The effect of pilot injection timing, intake charge pressure, and charge temperature on engine performance and emissions with natural gas fueling was studied. With appropriate control of the above variables, engine-out brake specific NOx emissions could be reduced to the range of 0.07–0.10 g/kWh from the baseline diesel (with mechanical fuel injection) value of 10.5 g/kWh. For this NOx reduction, the decrease in fuel conversion efficiency from the baseline diesel value was approximately 1–2 percent. Total unburned hydrocarbon (HC) emissions and carbon monoxide (CO) emissions were higher with natural gas operation. Heat release schedules obtained from measured cylinder pressure data are also presented. The importance of pilot injection timing and inlet conditions on the stability of engine operation and knock are also discussed.

Modeling the Performance of a Turbo-Charged Spark Ignition Natural Gas Engine With Cooled Exhaust Gas Recirculation

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Hailin Li ◽  
Ghazi A. Karim
Keyword(s):  
Natural Gas ◽  
Exhaust Gas Recirculation ◽  
Spark Ignition ◽  
Exhaust Gas ◽  
Engine Operation ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Auto Ignition ◽  
Wide Range ◽  
Gas Recirculation

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.

Strategies for Reduced NOx Emissions in Pilot-Ignited Natural Gas Engines

2003 ◽  
Vol 126 (3) ◽  
pp. 665-671 ◽  
Author(s):  
S. R. Krishnan ◽  
K. K. Srinivasan ◽  
S. Singh ◽  
S. R. Bell ◽  
K. C. Midkiff ◽  
...  
Keyword(s):  
Natural Gas ◽  
Fuel Injection ◽  
Nox Reduction ◽  
Engine Performance ◽  
Injection Timing ◽  
Nox Emissions ◽  
Pilot Injection ◽  
Engine Operation ◽  
Performance And Emissions ◽  
Inlet Conditions

The performance and emissions of a single-cylinder natural gas fueled engine using a pilot ignition strategy have been investigated. Small diesel pilots (2–3% on an energy basis), when used to ignite homogeneous natural gas-air mixtures, are shown to possess the potential for reduced NOx emissions while maintaining good engine performance. The effects of pilot injection timing, intake charge pressure, and charge temperature on engine performance and emissions with natural gas fueling were studied. With appropriate control of the above variables, it was shown that full-load engine-out brake specific NOx emissions could be reduced to the range of 0.07–0.10 g/kWh from the baseline diesel (with mechanical fuel injection) value of 10.5 g/kWh. For this NOx reduction, the decrease in fuel conversion efficiency from the baseline diesel value was approximately one to two percentage points. Total unburned hydrocarbon (HC) emissions and carbon monoxide (CO) emissions were higher with natural gas operation. The nature of combustion under these conditions was analyzed using heat release schedules predicted from measured cylinder pressure data. The importance of pilot injection timing and inlet conditions on the stability of engine operation and knock are also discussed.

Experimental Investigation of a Heavy-Duty Compression-Ignition Engine Retrofitted to Natural Gas Spark-Ignition Operation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Jinlong Liu ◽  
Hemanth Kumar Bommisetty ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Heavy Duty ◽  
Compression Ignition Engine ◽  
Engine Operation ◽  
Cycle Variation ◽  
Spark Timing ◽  
Ci Engines

Heavy-duty compression-ignition (CI) engines converted to natural gas (NG) operation can reduce the dependence on petroleum-based fuels and curtail greenhouse gas emissions. Such an engine was converted to premixed NG spark-ignition (SI) operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. Engine performance and combustion characteristics were investigated at several lean-burn operating conditions that changed fuel composition, spark timing, equivalence ratio, and engine speed. While the engine operation was stable, the reentrant bowl-in-piston (a characteristic of a CI engine) influenced the combustion event such as producing a significant late combustion, particularly for advanced spark timing. This was due to an important fraction of the fuel burning late in the squish region, which affected the end of combustion, the combustion duration, and the cycle-to-cycle variation. However, the lower cycle-to-cycle variation, stable combustion event, and the lack of knocking suggest a successful conversion of conventional diesel engines to NG SI operation using the approach described here.

Lean Blowout Limit and NOx-Production of a Premixed Sub-ppm NOx Burner With Periodic Flue Gas Recirculation

2004 ◽  
Author(s):  
Jochen R. Kalb ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Flue Gas ◽  
Gas Content ◽  
Stable Operation ◽  
Reacting Flow ◽  
Nox Emissions ◽  
Lean Blowout ◽  
Fresh Mixture ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

The technological objective of this work is the development of a lean-premixed burner for natural gas. Sub-ppm NOx emissions can be accomplished by shifting the lean blowout limit (LBO) to slightly lower adiabatic flame temperatures than the LBO of current standard burners. This can be achieved with a novel burner concept utilizing periodic flue gas recirculation: Hot flue gas is admixed to the injected premixed fresh mixture with a mass flow rate of comparable magnitude, in order to achieve self-ignition. The subsequent combustion of the diluted mixture again delivers flue gas. A fraction of the combustion products is then admixed to the next stream of fresh mixture. This process pattern is to be continued in a cyclically closed topology, in order to achieve stable combustion of e.g. natural gas in a temperature regime of very low NOx production. The principal ignition behavior and NOx production characteristics of one sequence of the periodic process was modeled by an idealized adiabatic system with instantaneous admixture of partially or completely burnt flue gas to one stream of fresh reactants. With the CHEMKIN-II package a reactor network consisting of one perfectly stirred reactor (PSR, providing ignition in the first place) and two plug flow reactors (PFR) has been used. The effect of varying burnout and the influence of the fraction of admixed flue gas have been evaluated. The simulations have been conducted with the reaction mechanism of Miller and Bowman and the GRI-Mech 3.0 mechanism. The results show that the high radical content of partially combusted products leads to a massive decrease of the time required for the formation of the radical pool. As a consequence, self-ignition times of 1 ms are achieved even at adiabatic flame temperatures of 1600 K and less, if the flue gas content is about 50%–60% of the reacting flow after mixing is complete. Interestingly, the effect of radicals on ignition is strong, outweighs the temperature deficiency and thus allows stable operation at very low NOx emissions.

Achieving Fast Catalyst Light-Off from a Heavy-Duty Stoichiometric Natural Gas Engine Capable of 0.02 g/bhp-hr NOX Emissions

2018 ◽  
Author(s):  
Ian Smith ◽  
James Chiu ◽  
Gordon Bartley ◽  
Eugene Jimenez ◽  
Thomas Briggs ◽  
...  
Keyword(s):  
Natural Gas ◽  
Nox Emissions ◽  
Heavy Duty ◽  
Gas Engine ◽  
Natural Gas Engine
Sign in / Sign up

Export Citation Format

Share Document