In gas turbine starting what is the relation between IGV angle and exhust temperature?

Exhaust temperature is directly proportional to IGV to referenced

temperature within certain limit to the compressor

The IGV temperature control reference is basically the same as the CPD-biased exhaust temperature control reference. (Some older units had a 5-10 deg F offset, making the IGV exhaust temp control reference slightly lower.

Exhaust temperature is directly proportional to IGV angle. If IGV angle is large, there will be high exhaust temperature.

The IGV ( INLET GUIDE VANE) controls the amount of inlet air entering the gas turbine. Depend of the speed control system air to fuel ratio will be adjusted,IGV operates -30 to +5 angle roataion, the IGV opens to keep exhaust more and speed up the turbine speed

The IGV controls the amount of inlet air entering the gas turbine. Thus, if the amount of air to fuel ratio is not constant. Then the higher the IGV, the lower the exhaust temperature. 

Using this principle, the IGV opens to keep exhaust temperature rerferenced within certain limit.

igv modulate in order to keep const exhaust temp doesnot exceed limit520 cent grade for various loadind requirements .