Thrust degradation from dirty fan

[orion1210]

We are all aware that gas turbine engine performance can be reduced as a result of compressor and turbine deposits in terms of increased fuel burn resulting in increased turbine temperatures.

Aside from this, I wondered if anybody could put any figures on potentially reduced thrust output or the resulting cruise speed penalty as a result of a dirty and therefore a less efficient fan, assuming that a given N1 can still be obtained without being turbine temp limited?

Thanks