This invention relates generally to detecting leaks and blockages in a network of pipes and more particularly to detecting leaks and blockages in the steam cooling circuit of a gas turbine engine. 
A gas turbine engine includes a compressor that provides pressurized air to a combustion section where the pressurized air is mixed with fuel and ignited for generating hot combustion gases.  These gases flow downstream to a multi-stage turbine.  Each turbine stage includes a plurality of circumferentially spaced apart blades or buckets extending radially outwardly from a wheel that is fastened to a shaft for rotation about the centerline axis of the engine.  The hot gases expand against the turbine buckets causing the wheel to rotate.  This in turn rotates the shaft that is connected to the compressor and may be also connected to load equipment such as an electric generator.  Thus, the turbine extracts energy from the hot gases to drive the compressor and provide useful work such as generating electricity.  One common application of a gas turbine engine is a combined cycle power generation system in which the exhaust of the gas turbine is used to generate steam in a heat recovery steam generator.  This steam is used to drive a steam turbine to generate additional electricity. 
It is well known that raising the turbine operating temperature can increase the efficiency of gas turbine engines.  As operating temperatures are increased, the thermal limits of certain engine components, such as the turbine buckets, nozzles and shrouds, may be exceeded, resulting in reduced service life or even material failure.  In addition, the increased thermal expansion and contraction of these components adversely affects clearances and their interfitting relationship with other components.  Thus, it is common to provide cooling to such components to keep their temperatures within design limits. 
In combined cycle power generation systems, it has recently been demonstrated that steam can be extracted from the heat recovery steam generator to cool the at risk components of the gas turbine engine.  Typically, the extracted steam is passed through internal passages formed in the buckets, nozzles and shrouds of the first two turbine stages so as to remove heat therefrom.  The heated steam is then returned to a different stage of the heat recovery steam generator or directly to the inlet of the steam turbine.  Because the steam is heated in the cooling process and then used in the steam turbine, the overall thermal efficiency of the combined cycle power generation system is increased. 
However, this steam cooling circuit, particularly the internal passages of the buckets, nozzles and shrouds, can be susceptible to leaks and blockages.  A leak or blockage that deprives one or more of the turbine components of adequate coolant flow can result in failure of the affected components.  It is thus desirable to provide the steam cooling circuit with leak and blockage detection so that preventative measures can be taken if a leak or blockage is detected.  However, detecting leaks and blockages inside the turbine is difficult with conventional detection methods because pressure, temperature and flow measurements are not generally available inside the turbine. 
Accordingly, there is a need for a system and method for detecting leaks and blockages using readily available external measurements. 
The above-mentioned need is met by the present invention which provides a fault detection and isolation system for detecting leaks and blockages in a fluid handling system having at least one component through which fluid flows.  The fault detection and isolation system includes sensors for measuring fluid conditions upstream and downstream of the component.  The sensors generate signals that are representative of the upstream and downstream fluid conditions and are fed to a control algorithm.  The control algorithm uses the measured fluid conditions to generate estimates of an inlet state for the component and an outlet state for the component.  The control algorithm also calculates innovation sequences for the estimated inlet and outlet states, and then compares the innovation sequences to predetermined thresholds to detect leaks and blockages. 
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.