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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Performance of a Laser Ignited Multicylinder Lean Burn Natural Gas Engine

[+] Author and Article Information
Bader Almansour

Department of Mechanical and
Aerospace Engineering,
University of Central Florida,
4000 Central Florida Boulevard,
Orlando, FL 32816
e-mail: bader@knights.ucf.edu

Subith Vasu

Department of Mechanical and
Aerospace Engineering,
University of Central Florida,
4000 Central Florida Boulevard,
Orlando, FL 32816
e-mail: subith@ucf.edu

Sreenath B. Gupta

Argonne National Laboratory,
362-G212, 9700 South Cass Avenue,
Lemont, IL 60439
e-mail: sgupta@anl.gov

Qing Wang

Princeton Optronics, Inc.,
1 Electronics Drive,
Mercerville, NJ 08619
e-mail: qwang@princetonoptronics.com

Robert Van Leeuwen

Princeton Optronics, Inc.,
1 Electronics Drive,
Mercerville, NJ 08619
e-mail: rleeuwen@princetonoptronics.com

Chuni Ghosh

Princeton Optronics, Inc.,
1 Electronics Drive,
Mercerville, NJ 08619
e-mail: cghosh@princetonoptronics.com

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 3, 2016; final manuscript received April 19, 2017; published online June 6, 2017. Assoc. Editor: Eric Petersen.The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States government purposes.

J. Eng. Gas Turbines Power 139(11), 111501 (Jun 06, 2017) (7 pages) Paper No: GTP-16-1480; doi: 10.1115/1.4036621 History: Received October 03, 2016; Revised April 19, 2017

Market demands for lower fueling costs and higher specific powers in stationary natural gas engines have engine designs trending toward higher in-cylinder pressures and leaner combustion operation. However, ignition remains as the main limiting factor in achieving further performance improvements in these engines. Addressing this concern, while incorporating various recent advances in optics and laser technologies, laser igniters were designed and developed through numerous iterations. Final designs incorporated water-cooled, passively Q-switched, Nd:YAG microlasers that were optimized for stable operation under harsh engine conditions. Subsequently, the microlasers were installed in the individual cylinders of a lean-burn, 350 kW, inline six-cylinder, open-chamber, spark ignited engine, and tests were conducted. The engine was operated at high-load (298 kW) and rated speed (1800 rpm) conditions. Ignition timing (IT) sweeps and excess-air ratio (λ) sweeps were performed while keeping the NOx emissions below the United States Environmental Protection Agency (USEPA) regulated value (brake-specific NOx (BSNOx) < 1.34 g/kW h), and while maintaining ignition stability at industry acceptable values (coefficient of variation of integrated mean effective pressure (COV_IMEP) < 5%). Through such engine tests, the relative merits of (i) standard electrical ignition system and (ii) laser ignition system were determined. A rigorous combustion data analysis was performed and the main reasons leading to improved performance in the case of laser ignition were identified.

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Figures

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Fig. 1

(a) Schematic and (b) photograph of the laser igniter equipped with water-cooled VCSEL pumped microlaser

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Fig. 2

View of (left) standard spark ignition systems, (right) laser ignition system as seen from cylinder#1 of the engine

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Fig. 3

Efficiency, COV_IMEP and BSNOx variation with ignition timing

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Fig. 4

(left) BSNOx versus brake thermal efficiency tradeoff, (right) COV_IMEP versus brake thermal efficiency. Allowable limits for NOx emissions and ignition stability are marked with horizontal red arrows (see figure online for color).

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Fig. 5

Rate of heat release in cylinder#4 for SI and 2P-LI

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Fig. 6

(a) Ignition delay, (b) combustion duration, and (c) MFB50% in cylinder#4 for SI and 2P-LI

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Fig. 7

ROHR plots for the optimal operational point with the use of 2P-LI

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Fig. 8

Brake-specific carbon monoxide (BSCO) and brake-specific hydrocarbon (BSHC) emissions for SI (λ = 1.6) and 2P-LI (λ = 1.68). Circles mark the ideal conditions for either ignition system.

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