Characterization of Erosion Mechanisms of Natural Gas Engine Spark Plugs

2004 ◽  
Author(s):  
Roger K. Richards ◽  
David M. Layton ◽  
Hua-Tay Lin ◽  
Michael P. Brady
Keyword(s):  
Natural Gas ◽  
Base Alloy ◽  
Oxide Phase ◽  
Intergranular Cracking ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Ni Alloy ◽  
Center Electrode ◽  
Erosion Mechanisms ◽  
A Site

J-type spark plugs composed of Ni-base alloy electrodes with a pure Ir tip in the center electrode and a Pt-W alloy tip in the ground electrode were examined as-manufactured and after use in natural gas reciprocating engines by spectroscopic and metallurgical techniques. The spectroscopic examination indicated Ni emission from the Ni alloy electrodes in new plugs, but a strong Ca signal in engine used plugs. This was confirmed by metallurgical examination, which showed the presence of Ca containing glassy oxide phase(s) (with the electrode alloy components) in the used spark plug electrodes. Intergranular cracking was observed on the Ir and Pt-W alloy electrode insert tips. The interface between the Pt-W insert and the Ni alloy ground electrode also became a site for extensive cracking and oxidation during service. These oxidation/corrosion and metallurgical issues may represent a significant component of the wear mechanism of these plugs in natural gas engines.

Evaluation of Spark Plug and Timing Configurations on the Fuel Consumption, Combustion Stability, and Emissions of a Large-Bore, Two-Stroke, Natural Gas Engine

2016 ◽  
Author(s):  
Derek Johnson ◽  
Marc Besch ◽  
Nathaniel Fowler ◽  
Robert Heltzel ◽  
April Covington
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Combustion Engine ◽  
Engine Performance ◽  
Combustion Stability ◽  
Oxides Of Nitrogen ◽  
Natural Gas Engines ◽  
Fuel Delivery ◽  
Spark Plug ◽  
Trade Offs

Emissions compliance is a driving factor for internal combustion engine research pertaining to both new and old technologies. New standards and compliance requirements for off-road spark ignited engines are currently under review and include greenhouse gases. To continue operation of legacy natural gas engines, research is required to increase or maintain engine efficiency, while reducing emissions of carbon monoxide, oxides of nitrogen, and volatile organic compounds such as formaldehyde. A variety of technologies can be found on legacy, large-bore natural gas engines that allow them to meet current emissions standards — these include exhaust after-treatment, advanced ignition technologies, and fuel delivery methods. The natural gas industry uses a variety of spark plugs and tuning methods to improve engine performance or decrease emissions of existing engines. The focus of this study was to examine the effects of various spark plug configurations along with spark timing to examine any potential benefits. Spark plugs with varied electrode diameter, number of ground electrodes, and heat ranges were evaluated against efficiency and exhaust emissions. Combustion analyses were also conducted to examine peak firing pressure, location of peak firing pressure, and indicated mean effective pressure. The test platform was an AJAX-E42 engine. The engine has a bore and stroke of 0.216 × 0.254 meters (m), respectively. The engine displacement was 9.29 liters (L) with a compression ratio of 6:1. The engine was modified to include electronic spark plug timing capabilities along with a mass flow controller to ensure accurate fuel delivery. Each spark plug configuration was examined at ignition timings of 17, 14, 11, 8, and 5 crank angle degrees before top dead center. The various configurations were examined to identify optimal conditions for each plug comparing trade-offs among brake specific fuel consumption, oxides of nitrogen, methane, formaldehyde, and combustion stability.

Extending the Lean Limit of Natural Gas Engines

2008 ◽  
Author(s):  
R. L. Evans
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Lean Burn ◽  
Stratified Charge ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Charge Mixture ◽  
Cyclic Variations ◽  
Lean Limit ◽  
The Stability

Two different methods to improve the thermal efficiency and reduce the emissions from lean-burn natural gas fuelled engines have been developed, and are described in this paper. One method used a “squish-jet” combustion chamber designed specifically to enhance turbulence generation, while the second method provided a partially stratified-charge mixture near the spark plug in order to enhance the ignition of lean mixtures of natural gas and air. The squish-jet combustion chamber was found to reduce Bsfc by up to 4.8% in a Ricardo Hydra engine, while the NOx – efficiency tradeoff was greatly improved in a Cummins L-10 engine. The partially stratified-charge combustion system extended the lean limit of operation in the Ricardo Hydra by some 10%, resulting in a 64% reduction in NOx emissions at the lean limit of operation. Both techniques were also shown to be effective in increasing the stability of combustion, thereby reducing cyclic variations in cylinder pressure.

Effects of Spark Plug Number and Location in Natural Gas Engines

1992 ◽  
Vol 114 (3) ◽  
pp. 475-479 ◽  
Author(s):  
R. C. Meyer ◽  
D. P. Meyers ◽  
S. R. King ◽  
W. E. Liss
Keyword(s):  
Natural Gas ◽  
Thermal Efficiency ◽  
Cylinder Pressure ◽  
Natural Gas Engines ◽  
Single Cylinder Engine ◽  
Spark Plug ◽  
Combustion Duration ◽  
Peak Cylinder Pressure ◽  
Wide Range ◽  
Pressure Peak

Combustion experiments were conducted on a spark-ignited single-cylinder engine operating on natural gas. A special open chamber cylinder head was designed to accept as many as four spark plugs. Data were obtained to investigate the effects of spark plug quantity and location on NOx, HC, CO emissions, brake and indicated thermal efficiency, MBT timing, combustion duration, ignition delay, peak cylinder pressure, peak cylinder temperature, and heat release over a wide range of equivalence ratios.

Solutions for Improving Spark Plug Life in High Efficiency, High Power Density, Natural Gas Engines

2006 ◽  
Author(s):  
Maria-Emmanuella McCoole ◽  
Luigi Tozzi ◽  
Daniel L. Tribble
Keyword(s):  
Natural Gas ◽  
Power Density ◽  
High Power ◽  
Electrode Surface ◽  
High Efficiency ◽  
High Power Density ◽  
Electrode Gap ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Engine Power

Short spark plug life, resulting in increased engine downtime and operating costs, is the primary factor limiting the power density and thermal efficiency in lean burn natural gas engines. Fundamentally, as engine power density increases, spark plug life decreases. Common approaches to increasing spark plug life include use of high melting temperature electrode materials and increased electrode surface area. However, future targets for engine efficiency and power density require more effective system solutions. In order to achieve these system solutions, work has been focused on developing an empirically derived electrode erosion model. This model quantifies spark plug life as a function of spark discharge characteristics, spark plug electrode design, and flow fields in the vicinity of the spark plug gap for different engine power densities. Furthermore, quenching effects resulting from large surface electrodes and smaller spark gaps have been included to verify ignitability for given in-cylinder charge density and air/fuel ratio conditions. A good agreement between experimental data and model predictions has been demonstrated. Finally, a solution for extending spark plug life in high efficiency, high power density, natural gas engines has been proposed. This solution combines high spark power with a spark plug design consisting of small electrode gap, large electrode surface, and with enhanced flow fields at the electrode gap.

Use of Railplugs to Extend the Lean Limit of Natural Gas Engines

2004 ◽  
Author(s):  
Hongxun Gao ◽  
Ron Matthews ◽  
Sreepati Hari ◽  
Matt Hall
Keyword(s):  
Natural Gas ◽  
Stability Limit ◽  
High Energy ◽  
Lean Burn ◽  
Ignition System ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Spark Plug ◽  
Lean Mixtures ◽  
Ignition Characteristics

Ignition of extremely lean mixtures is a very challenging problem, especially for the low speed, high load conditions of large-bore natural gas engines. This paper presents initial results from testing a high energy ignition system, the railplug, which can assure ignition of very lean mixtures by means of its high energy deposition and high velocity jet of the plasma. Comparisons of natural gas engine tests using both a spark plug and a railplug are presented and discussed in this paper. The preliminary engine test show that the lean stability limit (LSL) can be extended from an equivalence ratio, φ, of ∼0.63 using a spark plug down to 0.56 using a railplug. The tests show that the railplug is very promising ignition system for lean burn natural gas engines and potentially for other engines that operate with very dilute mixtures. The ignition characteristics of different railplug geometric and circuit designs are also discussed.

scholarly journals Lean-Burn Stationary Natural Gas Reciprocating Engine Operation With a Prototype Miniature Diode Side Pumped Passively Q-Switched Laser Spark Plug

2008 ◽  
Author(s):  
Dustin L. McIntyre ◽  
Steven D. Woodruff ◽  
Michael H. McMillian ◽  
Steven W. Richardson ◽  
Mridul Gautam
Keyword(s):  
Natural Gas ◽  
Laser System ◽  
Lean Burn ◽  
Engine Operation ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Laser Spark ◽  
Laser Systems ◽  
Laser Design ◽  
Engine Testing

To meet the ignition system needs of large bore lean burn stationary natural gas engines a laser diode side pumped passively Q-switched laser igniter was developed and used to ignite lean mixtures in a single cylinder research engine. The laser design was produced from previous work. The in-cylinder conditions and exhaust emissions produced by the miniaturized laser were compared to that produced by a laboratory scale commercial laser system used in prior engine testing. The miniaturized laser design as well as the combustion and emissions data for both laser systems was compared and discussed. It was determined that the two laser systems produced virtually identical combustion and emissions data.

Extending the Lean Limit of Natural-Gas Engines

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
R. L. Evans
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Lean Burn ◽  
Stratified Charge ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Charge Mixture ◽  
Cyclic Variations ◽  
Lean Limit ◽  
The Stability

Two different methods to improve the thermal efficiency and reduce the emissions from lean-burn natural-gas fueled engines have been developed and are described in this paper. One method used a “squish-jet” combustion chamber designed specifically to enhance turbulence generation, while the second method provided a partially stratified-charge mixture near the spark plug in order to enhance the ignition of lean mixtures of natural gas and air. The squish-jet combustion chamber was found to reduce brake specific fuel consumption by up to 4.8% in a Ricardo Hydra engine, while the NOx efficiency trade-off was greatly improved in a Cummins L-10 engine. The partially stratified-charge combustion system extended the lean limit of operation in the Ricardo Hydra by some 10%, resulting in a 64% reduction in NOx emissions at the lean limit of operation. Both techniques were also shown to be effective in increasing the stability of combustion, thereby reducing cyclic variations in cylinder pressure.

Laser Ignition of Methane-Air Mixtures at High Pressures and Diagnostics

2005 ◽  
Vol 127 (1) ◽  
pp. 213-219 ◽  
Author(s):  
Herbert Kopecek ◽  
Soren Charareh ◽  
Maximilian Lackner ◽  
Christian Forsich ◽  
Franz Winter ◽  
...  
Keyword(s):  
Natural Gas ◽  
Nd:Yag Laser ◽  
High Pressures ◽  
Laser Energy ◽  
Spectroscopic Technique ◽  
Laser Ignition ◽  
Pulsed Nd:Yag Laser ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Induced Ignition

Methane-air mixtures at high fill pressures up to 30 bar and high temperatures up to 200°C were ignited in a high-pressure chamber with automated fill control by a 5 ns pulsed Nd:YAG laser at 1064 nm wavelength. Both, the minimum input laser pulse energy for ignition and the transmitted fraction of energy through the generated plasma were measured as a function of the air/fuel-equivalence ratio (λ). The lean-side ignition limit of methane-air mixtures was found to be λ=2.2. However, only λ<2.1 seems to be practically usable. As a comparison, the limit for conventional spark plug ignition of commercial natural gas engines is λ=1.8. Only with excessive efforts λ=2.0 can be spark ignited. The transmitted pulse shape through the laser-generated plasma was determined temporally as well as its dependence on input laser energy and properties of the specific gases interacting. For a first demonstration of the practical applicability of laser ignition, one cylinder of a 1 MW natural gas engine was ignited by a similar 5 ns pulsed Nd:YAG laser at 1064 nm. The engine worked successfully at λ=1.8 for a first test period of 100 hr without any interruption due to window fouling and other disturbances. Lowest values for NOx emission were achieved at λ=2.05 NOx=0.22 g/KWh. Three parameters obtained from accompanying spectroscopic measurements, namely, water absorbance, flame emission, and the gas inhomogeneity index have proven to be powerful tools to judge laser-induced ignition of methane-air mixtures. The following effects were determined by the absorption spectroscopic technique: formation of water in the vicinity of the laser spark (semi-quantitative); characterization of ignition (ignition delay, incomplete ignition, failed ignition); homogeneity of the gas phase in the vicinity of the ignition; and the progress of combustion.

Analysis of the Rotating Arc Spark Plug in a Natural Gas Engine

2005 ◽  
Author(s):  
Jim Tassitano ◽  
James E. Parks
Keyword(s):  
Natural Gas ◽  
Fuel Efficiency ◽  
Cost Effective ◽  
Combustion Stability ◽  
Engine Operation ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Spark Plug ◽  
Rotating Arc

Large natural gas engines are durable and cost-effective generators of power for distributed energy applications. Fuel efficiency is an important aspect of distributed generation since operating costs associated with fuel consumption are the major component of energy cost on a life-cycle basis; furthermore, higher fuel efficiency results in lower CO2 emissions. Leaner operation of natural gas engines can result in improved fuel efficiency; however, engine operation becomes challenging at leaner air-to-fuel ratios due to several factors. One factor in combustion control is ignition. At lean air-fuel mixtures, reliable and repeatable ignition is necessary to maintain consistent power production from the engine, and spark plug quality and durability play an important role in reliability of ignition. Here research of a novel spark plug design for lean natural gas engines is presented. The spark plug is an annular gap spark plug with a permanent magnet that produces a magnetic field that forces the spark to rotate during spark discharge. The rotating arc spark plug (RASP) has the potential to improve ignition system reliability and durability. In the study presented here, the RASP plug was operated in a small natural gas engine, and combustion stability (measured by the coefficient of variation of indicated mean effective pressure (IMEP)) was measured as a function of air-to-fuel ratio to characterize the ignition performance at lean mixtures. Comparisons were made to a standard J-plug spark plug.

Laser Ignition of Methane-Air Mixtures at High Pressures and Diagnostics

2003 ◽  
Author(s):  
Herbert Kopecek ◽  
Soren Charareh ◽  
Max Lackner ◽  
Christian Forsich ◽  
Franz Winter ◽  
...  
Keyword(s):  
Natural Gas ◽  
Nd:Yag Laser ◽  
High Pressures ◽  
Laser Energy ◽  
Spectroscopic Technique ◽  
Laser Ignition ◽  
Pulsed Nd:Yag Laser ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Induced Ignition

Methane-air mixtures at high fill pressures up to 30 bar and high temperatures up to 200 °C were ignited in a high pressure chamber with automated fill control by a 5 ns pulsed Nd:YAG laser at 1064 nm wavelength. Both, the minimum input laser pulse energy for ignition and the transmitted fraction of energy through the generated plasma were measured as a function of the air/fuel-equivalence ratio (λ). The lean side ignition limit of methane-air mixtures was found to be λ = 2.4. However, only λ < 2.2 seems to be practically usable. As a comparison, the limit for conventional spark plug ignition of commercial natural gas engines is λ = 1.8. Only with excessive efforts λ = 2.0 can be spark-ignited. The transmitted pulse shape through the laser-generated plasma was determined temporally as well as its dependence on input laser energy and properties of the specific gases interacting. For a first demonstration of the practical applicability of laser ignition, one cylinder of a 1 MW natural gas engine was ignited by a similar 5 ns pulsed Nd:YAG laser at 1064 nm. The engine worked successfully at λ = 1.8 for a first test period of 100 hours without any interruption due to window fouling and other disturbances. Lowest values for NOx emission were achieved at λ = 2.05 (NOx = 0.22 g/KWh). Three parameters obtained from accompanying spectroscopic measurements, namely water absorbance, flame emission and the gas inhomogeneity index have proven to be a powerful tool to judge laser-induced ignition of methane-air mixtures. The following effects were determined by the absorption spectroscopic technique: formation of water in the vicinity of the laser spark (semi-quantitative); characterization of ignition (ignition delay, incomplete ignition, failed ignition); homogeneity of the gas phase in the vicinity of the ignition and the progress of combustion.

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