Impact of Inlet Filter Pressure Loss on Single and Two-Spool Gas Turbine Engines for Different Control Modes

Inlet filtration systems are designed to protect industrial gas turbines from air borne particles and foreign objects, thereby improving the quality of air for combustion and reducing component fouling. Filtration systems are of varying grades and capture efficiencies, with the higher efficiency systems filters providing better protection but higher pressure losses. For the first time, two gas turbine engine models of different configurations and capacities have been investigated for two modes of operation (constant turbine entry temperature (TET) and load/power) for a two- and three-stage filter system. The main purpose of this is to present an account on factors that could decide the selection of filtration systems by gas turbine operators, solely based on performance. The result demonstrates that the two-spool engine is only slightly more sensitive to intake pressure loss relative to the single-spool. This is attributed to higher pressure ratio of the two-spool as well as the deceleration of the high pressure compressor (HPC)/high pressure turbine (HPT) shaft rotational speed in a constant TET operation. The compressor of the single-spool engine and the low pressure compressor (LPC) of the two-spool shows similar behavior: slight increase in pressure ratio and reduced surge margin at their constant rotational speed operation. Loss in shaft power is observed for both engines, about 2.5% at 1000 Pa loss. For constant power operation there is an increase in fuel flow and TET, and as a result the creep life was estimated. The result obtained indicates earlier operating hours to failure for the three-stage system over the two-stage by only a few thousand hours. However, this excludes any degradation due to fouling that is expected to be more significant in the two-stage system.