Core size

Core size is a parameter used in aeroengine performance engineering to enable a size comparison between jet engine (e.g. turbofan) cores.

The alternative core power parameter is more difficult to compute, but has the advantage that it takes into account not only the basic flow size of the device, but also the impact of core supercharging and turbine rotor inlet temperature.

There are several definitions of core size in use, but the following definition is fairly popular:

$\textrm{core~size} = w_{2} * {\frac{\sqrt{T_{3}}}{P_{3}}}$

where:

• $w_{2}\,$ ~ (HP) compressor entry mass flow
• $P_{3}\,$ ~ (HP) compressor exit total pressure
• $T_{3}\,$ ~ (HP) compressor exit total temperature

High Pressure (HP) compressor entry flow (rather than exit flow) is used in the calculation, because core size is then unaffected by any changes in HP compressor interstage bleed during the engine development programme.