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Research Papers: Internal Combustion Engines

Extending the Lean Limit of Natural-Gas Engines

[+] Author and Article Information
R. L. Evans

Department of Mechanical Engineering, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada

J. Eng. Gas Turbines Power 131(3), 032803 (Feb 12, 2009) (5 pages) doi:10.1115/1.3043814 History: Received June 12, 2008; Revised June 19, 2008; Published February 12, 2009

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.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

UBC 1C squish-jet combustion chamber

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Figure 2

MBT ignition advance

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Figure 3

Brake specific fuel consumption

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Figure 4

Brake specific NOx emissions

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Figure 5

NOx versus efficiency trade-off

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Figure 6

The partially stratified charge sparkplug

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Figure 7

Extension of the lean limit

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Figure 8

NOx reduction with PSC operation

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Figure 9

IMEP distribution with respect to crank-angle

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