Gas Turbine Handbook : Principles and Practices

Parameter Characteristics 111
utilizing rotor speeds are biased by temperature (Figure 7-4). On splitshaft
or dual-spool engines, rotor speeds vary as a function of engine
match changes between the compressor and the turbine. The complex
interplay of these components, as seen by the interaction between N 1
(low speed) and N 2
(high speed), is very subtle and difficult to define
without a detailed gas path analysis. On single-spool engines driving
generators, rotor speed is one of the controlled functions and in itself will
not change.
OIL PRESSURE AND TEMPERATURE
Measurement Methods
Oil pressure is indicative of the pressure drop across the filters and
external and internal leaks. External leaks will eventually become obvious,
but internal leaks can be difficult to detect. Internal leaks can result
in oil leaking into the hot gas path and may or may not be evidenced
by exhaust smoke. Care should be taken when the unit is down to determine
if oil is leaking within the engine by inspecting the engine inlet,
the exhaust duct and where possible a spot check (boroscope inspection)
of the compressor discharge or bleed air discharge.
Exhaust Gas Temperature (EGT)
Figure 7-3. Temperature measurement is a function of the number of
probes, their position and their sensitivity.