Smoke Emission Reduction during Startup of a Standby Gas Turbine Generator Set

Abstract

Smoke emissions during startup of a standby gas turbine generator set were reduced by improvements of fuel control logics. A tested engine was mainly composed of two- stage centrifugal compressor, three-stage axial turbine and a single can combustor. A fully electronic controlled liquid fuel valve is used to adjust the flow rate of heavy fuel oil A. Smoke emissions in the exhaust gas were measured using an opacity smoke meter. Traditionally, a fuel control valve is instantaneously opened to avoid ignition failures at engine startup period. And high fuel pressure is required to obtain fine fuel spray. However, they cause fuel rich combustion during the startup, and thereby much black smoke emission. At our test rig, smoke emissions can be seen at exhaust duct exit during the period. For reducing the smoke emissions, two modifications were tested. First, a start point of fuel injection was delayed to wait for increase of air flow. And the fuel flow rate was reduced at the initial injection. They could shift to lean combustion condition at the ignition point. Secondly, fuel flow rate was gradually ramped with an increase of compressor rotational speed. Therefore, fuel flow rate could be kept under ignitable region even if ignition delay occurred. Smoke emissions reduction during engine startup was achieved by the two modifications without ignition stability loss.