The fuel burned in a gas turbine engine sets the compressor running line and also has to be used in 'non-dimensional' form to show its effect on engine operation. It is used as a ratio with combustor pressure when shown on a compressor map. Corrected fuel flow is shown as w fuel = w / θ θ δ δ . Although both air and fuel are flows of fluid their non-dimensional parameters are different, w θ θ / δ δ and w / θ θ δ δ , because non-dimensional airflow is a form of fluid Mach number while fuel is flow of an incompressible energy source. The dimensions of airflow are M/t and those of fuel-flow are ML /t, where M, L and t are mass, length and time.