Courtesy of Precision Combustion, Inc., USA

Precision Combustion, Inc. (PCI) recently completed a design optimization study for a new gas turbine combustor. Conventional land-based gas turbine combustors produce highly luminous and sooty flames with high liner wall temperatures. This makes them difficult to conceal during wartime and produces significant amounts of NOx in the primary combustion zone. PCI's alternative approach utilizes a catalytic torch integrated with an air-blast fuel injector along the injector centerline. The catalytic torch not only provides reliable ignition but also enhances combustor stability, allowing the primary zone to operate leaner, reducing harmful emissions.

The FLUENT study compared combustor performance with the catalytic torch for four different primary hole jet sizes to a baseline combustor performance that used spark plugs as the ignition source. Results showed that with the addition of more air through the primary jets, the catalytic torch provided a tremendous improvement in combustor performance. The mixing of hot gases was significantly improved, resulting in a dramatic flattening of the combustor exit temperature profile. Carbon monoxide (CO) and nitric oxide (NO) mass fraction distributions provided insight into the flame structure and extent of pollutant formation. The catalytic torch configuration provided more complete destruction of CO and substantially lowered NOx emissions. Soot model results showed that a leaner primary combustion zone was very effective at reducing soot concentrations.

The cost of testing each of the configurations would have been about ten times as high as the cost of the CFD analysis.

These detailed parametric studies provided engineers with critical insights for a small fraction of the cost and time required for traditional prototype testing. Evaluating the performance of the five different combustor designs using FLUENT took one person approximately one month and cost about $20,000. The cost of testing these configurations would have been about $200,000 and would have generated much less useful information.

PCI's novel combustor includes catalytic torch integrated with an air-blast fuel injector.

The CFD optimized design was built and tested. Experimental results matched the simulation very closely. Soot formation and NO emissions were substantially lower than in current engines. PCI engineers are now working on developing catalytic ignition solutions for a broad range of gas turbine and reciprocating engine applications.

The FLUENT studies showed that configuration changes could produce a more uniform exit temperature profile. Temperature predictions from three representative configurations are shown here.

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