Gas Turbine Handbook : Principles and Practices

Detectable Problems 185
These curves are drawn relative to either corrected gas turbine power
output (or load), corrected turbine inlet temperature, or corrected rotor
speed. Power and turbine temperatures are the most used “reference”
parameters. For our discussion we will use corrected power as
the “reference” parameter. The first step in analyzing engine data is
converting it to standard conditions. Table 12-1 lists the correction
factors and their use:
Table 12-1. Performance Correction Factors.
————————————————————————————————
Pressure Correction Factor ≡ δ ≡ P x
/29.92
Temperature Correction Factor ≡ θ ≡ T x
/520
Pressure Corrected ≡ P X corr
≡ P X obs
/δ
Temperature Corrected ≡ T X corr
≡ T X obs
/θ
Speed Corrected ≡ N X corr
≡ N X obs
/√θ
Fuel Flow Corrected ≡ W f corr
≡ W f obs
/δ√θ
Specific Fuel Consumption Corrected ≡ SFC corr
≡ SFC X obs
/√θ
Airflow Parameter Corrected ≡ W a corr
≡ W a obs
√θ/δ
BHP Corrected ≡ BHP corr
≡ BHP /δ√θ obs
————————————————————————————————
where the subscript ‘x’ represents the particular stage or location of
the measurement and the subscript “obs” represents the observed
data. For example, ‘x = Amb’ designates ambient pressure and temperature
and P Amb
/29.92 and T Amb
/520 indicates that all corrections
are referenced back to ambient conditions. The standard day has
been defined as 59°F, 29.92"HGA by the International Organization
of Standardization (ISO). Hence this is referred to as the ISO
Standard. When inlet air treatment (heating or cooling) is used, it is
sometimes more convenient to correct to the ‘standard’ temperature
and pressure conditions at the inlet to the compressor. This value
must be decided upon by the owners, operators, manufacturers, etc.
For the purposes of this discussion we will use ISO Standard.
Compressor Discharge Pressure Corrected = CDP/δ = P 3
/δ