Flow machine performance modelling

A non-transitory computer readable storage medium comprising machine readable instructions for a data processor to determine performance characteristics of a flow machine having a rotor interacting with a flow field, by:

• receiving performance data for the flow machine comprising data values of a performance parameter of the rotor and mass flow for the flow machine at one or more defined rotor condition, the performance data defining a two-dimensional array of data in which points for a common rotor condition are identifiable;
• determining or receiving exit mass flow values for the flow downstream of the rotor;
• identifying one or more point in the received performance data;
• and,
• interpolating from the one or more point to a corresponding one or more point at a sub-idle rotor condition based on a correlation of the exit mass flow values for the points.

A system for analysing flow machine behaviour, comprising:

• a flow machine having a rotor configured to interact with a flow field and a plurality of sensors for sensing performance parameter values for the rotor and an operational rotor condition;
• and,
• a data processor configured to
• receive the performance parameter values data values and mass flow values for the flow machine at one or more defined rotor condition value, the performance parameter and mass flow values defining a two-dimensional array of data in which points for a common rotor condition are identifiable,
• determine or receive exit mass flow values for the flow downstream of the rotor,
• identify one or more point in the received performance data,
• interpolate from the one or more point to a corresponding one or more point at a sub-idle rotor condition based on a correlation of the exit mass flow values for the points, and output the corresponding one or more points for the sub-idle rotor condition.