Abstract:
Combined
cycles are subject to degradations and hence performance deterioration.
According to the author's survey nothing was found in the open literature on this
subject. Therefore, it was anticipated that it would be of great achievement if a tool for
analysing and diagnosing the deterioration of combined cycle could be produced. So
this thesis
presents a procedure for combined cycle performance analysis and fault
diagnostic by way of simulation.
l order to
accomplish this task successfully it was necessary to developed two
pieces of software. These are STEAMOMATCH for steam cycle performance
deterioration
analysis, and GOTRESS for GPA of any system. STEAMOMATCH, which
is built on the basics of combined cycle thermodynamics, can simulate up to three levels
of
pressure with reheat. On the other hand GOTRESS uses a Gas Path Analysis
technique that enables the user the choice of conducting either linear or non-linear GPA
at the same time. I both cases single or multiple fault can be diagnosed. GOTRESS
was built in such a
way that it makes it a generalised code that can be used not only for
combined
cycle but to diagnose a wide range of power cycle plants.
The deterioration simulation results of the gas turbine power plant showed that the
isentropic efficiency deterioration of the turbine unit has the uppermost sever effect on
overall
gas turbine power output and thermal efficiency. This is also the case with
steam turbine
(bottoming) cycle power and Rankine efficiency. Also, the simulation
results obtained showed that the relationship between the gas turbine size and its
performance deterioration is almost constant, i.e. performance deterioration follows the
plant's size. Among the two major gas turbine parameters that affects the steam
bottoming cycle performance of a CCGT power plant, the gas turbine exhaust
temperature has a predominant effect on steam cycle efficiency over the exhaust mass
flow.' As a
general result, the obtained simulation results showed that the behaviour of
CCGT
power plant performance is more affected by gas turbine cycle conditions than
by steam turbine cycle conditions. The obtained results showed that GPA can be
successfully applied to either gas turbine cycle, steam turbine cycle, or the combination
of the two in a form of combined cycle. The GPA diagnostic results obtained showed
that it would be
possible to detect some faults that might occur within the gas turbine
that is a
part of a combined cycle power plant by monitoring the dependent parameters
of the steam turbine (bottoming) cycle such as live steam pressure and temperature and
steam turbine
power. In contrast, it would not been possible to detect the problems
(implanted faults) that might occur within the steam turbine by monitoring the
dependent parameters of the gas turbine unit.