Diagnosis of Gas Turbine Operating Conditions by Means of the Inverse Cycle Calculation

Abstract

This paper presents a method for the analysis of gas turbine operating state, which uses the Cycle-Deck developed by gas turbine manufacturers and the measurements taken by means of the standard machine instrumentation. The gas turbine operating condition analysis is performed “adapting” the characteristic geometric and performance parameters (i.e., characteristic flow passage areas and efficiencies of the compressor and turbine, combustor efficiency, etc …), used as inputs by the Cycle-Deck, until the computed estimates of the measurable parameters agree with the values measured on the gas turbine. This is done by minimizing an objective function built as the sum of the squared residuals between the computed and measured values of the same parameters. The analysis of the variations between computed and expected values of the characteristic parameters allows the localization of inefficient operations due to deterioration and faults.

Gas Turbine Health State Determination: Methodology Approach and Field Application

“…In fact, for example, a single failure can lead to the same effects (same measurement variations) as those that can be induced by a series of concurrent failures. Furthermore, some typologies of failures, as clearance increase or combustor malfunctioning, are usually detectable with difficulty [12]. So, only an adequate number of measured quantities can help to distinguish among different failures.…”

“…One of the main effects of deterioration and fault is the modification of compressor and turbine performance maps. Since detailed information about actual modification of component maps is usually unavailable, the effects of deterioration and fault are simulated by scaling the map itself, that is, by calculating the map scaling factors through the inverse solution of the CP, in order to reproduce the measurements taken on the gas turbine [9,12].…”

“…In this paper, a GPA tool, developed by the authors [12] and validated through testbench measurements [39], is used. By comparing the actual and the expected values of the HIs, it is possible to determine (i) how far the actual machine operating condition is from the expected one, (ii) which components are degraded, and (iii) the causes of malfunctioning.…”

“…The GPA-based diagnostic process uses gas turbine field measurements to determine, by means of a gas turbine thermodynamic cycle model (cycle program (CP)), the actual values of the parameters that are indices of the gas turbine health state (Health Indices (HIs)), such as efficiencies, characteristic flow passage areas and pressure drops along the gas path [9,12,[24][25][26][27]. One of the main effects of deterioration and fault is the modification of compressor and turbine performance maps.…”

“…Linear GPA techniques have been developed and applied since the seventies [8], while nonlinear GPA techniques have been applied since the nineties [9][10][11][12].…”