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.

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.

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.

Development of an Open Path Laser Ignition System for a Large Bore Natural Gas Engine: Part 1 — System Design

2005 ◽  
Author(s):  
David L. Ahrens ◽  
Azer P. Yalin ◽  
Daniel B. Olsen ◽  
Gi-Heon Kim
Keyword(s):  
Natural Gas ◽  
Pollutant Emissions ◽  
Electrode Erosion ◽  
Laser Ignition ◽  
Ignition System ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Spark Plug ◽  
Engine Part ◽  
Beam Delivery

Using a laser, as opposed to a conventional (electrical) spark plug, to create a combustion initiating spark is potentially advantageous for several reasons: flexibility in choosing and optimizing the spark location, in particular to move the spark away from solid heat sinks; production of a more robust spark containing more energy; and obviation of electrode erosion problems. These advantages may lead to an extension of the lean limit, an increase in engine thermal efficiency, and the concomitant benefits of reduced pollutant emissions. This paper presents the design of a laser ignition system appropriate for a large bore natural gas engine. Design considerations include: optimization of spark location, design of beam delivery system and optical plug, and mitigation of vibration and thermal effects. Engine test results will be presented in the second paper of this two-paper series.

Laser Ignition of Natural Gas Engines Using Fiber Delivery

2005 ◽  
Author(s):  
Azer P. Yalin ◽  
Morgan W. Defoort ◽  
Sachin Joshi ◽  
Daniel Olsen ◽  
Bryan Willson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Past Research ◽  
Spark Ignition ◽  
Laser Source ◽  
Laser Ignition ◽  
Ignition System ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Design Concepts

A practical impediment to implementation of laser ignition systems has been the open-path beam delivery used in past research. In this contribution, we present the development and implementation of a fiber-optically delivery laser spark ignition system. To our knowledge, the work represents the first demonstration of fiber coupled laser ignition (using a remote laser source) of a natural gas engine. A Nd:YAG laser is used as the energy source and a coated hollow fiber is used for beam energy delivery. The system was implemented on a single-cylinder of a Waukesha VGF 18 turbo charged natural gas engine and yielded consistent and reliable ignition. In addition to presenting the design and testing of the fiber delivered laser ignition system, we present initial design concepts for a multiplexer to ignite multiple cylinders using a single laser source, and integrated optical diagnostic approaches to monitor the spark ignition and combustion performance.

Performance Analysis of a Natural Gas Generator Using Laser Ignition

2004 ◽  
Author(s):  
Munidhar S. Biruduganti ◽  
Sreenath B. Gupta ◽  
Bipin Bihari ◽  
Gregory Klett ◽  
Raj Sekar
Keyword(s):  
Natural Gas ◽  
Optical Fibers ◽  
High Pressures ◽  
Gasoline Engine ◽  
Pressure Rise ◽  
Laser Pulses ◽  
Laser Ignition ◽  
Solid Core ◽  
Gas Generator ◽  
Ignition Characteristics

A single cylinder spark ignited gasoline engine was modified to operate with natural gas. In such an engine, laser ignition was successfully demonstrated while transmitting the high-power laser pulses via solid core optical fibers. Subsequently, ignition studies were performed while using laser ignition (LI) and conventional spark ignition (SI). However, due to limitations imposed by the engine hardware the adverse conditions for ignition could not be simulated, i.e., of lean operation and high-pressures. As a result, the scope of the study was limited to comparing LI and SI ignition characteristics at various ignition timings. It was observed that both LI and SI resulted in reliable combustion over all ignition timings. Furthermore, LI resulted in higher rates of pressure rise and higher peak cylinder pressures. However, the higher NOx emissions resulting from such conditions might not be representative as the final performance of an engine as it is determined by optimizing ignition timing and other operating parameters.

On Comparative Engine Performance Testing With Fiber Delivered Laser Ignition and Electrical Ignition

2012 ◽  
Author(s):  
Nick Wilvert ◽  
Sachin Joshi ◽  
Azer Yalin
Keyword(s):  
Beam Quality ◽  
Engine Performance ◽  
Performance Testing ◽  
Laser Ignition ◽  
Solid Core ◽  
Oxides Of Nitrogen ◽  
Successful Operation ◽  
Natural Gas Engines ◽  
Nanosecond Pulses ◽  
Spark Plug

Laser ignition of natural gas engines has shown potential to improve many facets of engine performance including brake thermal efficiency, exhaust emissions, and durability as compared with traditional spark ignition. We present proof of concept of a novel fiber optic delivery approach using solid core multimode step index silica fibers with large cladding diameters (400 m core, 720 m cladding). The fibers were able to deliver high beam quality 25 nanosecond pulses of 1064 nm light with 7–10 mJ energy; sufficient to consistently ignite the engine at various air-fuel ratios and loads. Comparative tests between the laser spark plug and a traditional J-gap spark plug were performed on a single cylinder Waukesha Cooperative Fuel Research (CFR) engine running on bottled methane. Performance was measured in terms of the Coefficient of Variation (COV) of Net Mean Effective Pressure (NMEP), fuel specific efficiency, and emissions of oxides of nitrogen (NOx), carbon monoxide (CO), and total hydrocarbons (THC). Tests were run at three different NMEPs of 6, 8, and 12 bar at various air-fuel ratios. Results indicate successful operation of the fiber and improved engine performance at high NMEP and lean conditions.

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.

Development of a Fiber Delivered Laser Ignition System for Natural Gas Engines

2006 ◽  
Author(s):  
Azer P. Yalin ◽  
Adam R. Reynolds ◽  
Sachin Joshi ◽  
Morgan W. Defoort ◽  
Bryan Willson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Fiber Optics ◽  
High Efficiency ◽  
Low Cost ◽  
Laser Pulses ◽  
Hollow Fibers ◽  
Laser Source ◽  
Laser Ignition ◽  
Design Development ◽  
Natural Gas Engines

Laser ignition is viewed as a potential future technology for advanced high-efficiency low-emission natural gas engines. However, in order to make laser ignition systems more practical, thereby enabling them to transition from the laboratory to industrial settings, there is a need to develop fiber optically delivered ignition systems. Recent work at Colorado State University has shown the possibility of using coated hollow fibers for spark delivery and has demonstrated laser ignition and operation of a single engine cylinder using hollow fiber delivery. In order to practically operate a multiple cylinder engine, we envisage a simple and low-cost system based upon a single laser source being delivered (“multiplexed”) through multiple fibers to multiple engine cylinders. In this paper, we report on the design, development, and initial bench-top testing of a multiplexer. Bench-top testing showed that the multiplexer can be positioned with the required accuracy and precision for launching into fiber optics, and can be switched at the relatively high switching rates needed to operate modern natural gas engines. Another test employed the multiplexer to alternately launch laser pulses into a pair of hollow fibers in a way that allows spark creation downstream of the fibers.

scholarly journals Prechamber Equipped Laser Ignition for Improved Performance in Natural Gas Engines

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Bader Almansour ◽  
Subith Vasu ◽  
Sreenath B. Gupta ◽  
Qing Wang ◽  
Robert Van Leeuwen ◽  
...  
Keyword(s):  
Natural Gas ◽  
Soot Formation ◽  
Single Point ◽  
Spark Ignition ◽  
Laser Ignition ◽  
Efficiency Gain ◽  
Lean Burn ◽  
Single Cylinder ◽  
Natural Gas Engines ◽  
Improved Performance

Lean-burn operation of stationary natural gas engines offers lower NOx emissions and improved efficiency. A proven pathway to extend lean-burn operation has been to use laser ignition (LI) instead of standard spark ignition (SI). However, under lean conditions, flame speed reduces, thereby offsetting any efficiency gains resulting from the higher ratio of specific heats, γ. The reduced flame speeds, in turn, can be compensated with the use of a prechamber to result in volumetric ignition and thereby lead to faster combustion. In this study, the optimal geometry of PCLI was identified through several tests in a single-cylinder engine as a compromise between autoignition, NOx, and soot formation within the prechamber. Subsequently, tests were conducted in a single-cylinder natural gas engine comparing the performance of three ignition systems: standard electrical spark ignition (SI), single-point laser ignition (LI), and PCLI. Out of the three, the performance of PCLI was far superior compared to the other two. Efficiency gain of 2.1% points could be achieved while complying with EPA regulation (BSNOx < 1.34 kWh) and the industry standard for ignition stability (coefficient of variation of integrated mean effective pressure (COV_IMEP) < 5%). Test results and data analysis are presented identifying the combustion mechanisms leading to the improved performance.

Effects of Pulsed Nd:YAG Laser Energy on Teeth: A Three-Year Follow-up Study

1993 ◽  
Vol 124 (7) ◽  
pp. 45-51 ◽  
Author(s):  
Joel M. White ◽  
Harold E. Goodis ◽  
James C. Setcos ◽  
W. Stephan Eakle ◽  
Bruce E. Hulscher ◽  
...  
Keyword(s):  
Nd:Yag Laser ◽  
Laser Energy ◽  
Pulsed Nd:Yag Laser ◽  
Follow Up Study
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