Development of a Diagnostic Tool to Trouble Shoot LM2500 Performance and Controls Problems

Abstract

A diagnostic tool (computer program) has been developed by the US Navy to provide the operators of LM2500 gas turbines (which are used as main propulsion on 6 ship classes in the USN) and the supporting technical staff, an assessment of the performance of this engine and the calibration of the engine control system. Typically, USN LM2500s do not mechanically degrade to the point where they will physically not be capable of making the required power. Instead, drift or lack of calibration of the engine sensors or its signal conditioning, mechanical wear and drift in the engine fuel scheduling control will cause the engine, after a period of time, either to not meet its performance expectations or report a performance level that is different from the actual condition. This can cause the engine to fail to meet the performance expectations of the propulsion control system, whether it is a real problem or a reporting problem (due to sensor mis-calibration), and in the worst case can cause an engine failure. To address these issues a performance diagnostic tool was developed that allowed the troubleshooter to compare engine performance, as reported by engine sensors etc., against what should be expected from the engine. Based on any differences, the tool provides the investigator guidance on the most likely source for the problem. To make such a tool, required integrating engine steady state performance models, with knowledge of the engine control loops as well as engine sensor, signal conditioning accuracy and calibration requirements. At present the diagnostic tool is being used by Fleet Technical Support Center Pacific to diagnose engine and controls problems. The goal is to provide ship’s force with the capability to diagnose most of their own problems and to provide a history of a particular engine’s performance.