Please help me
 

Hi guys
I am simulating 20 degree combustor geometry in fluent.I am specifying the mass flow inlet condition at the inlet and giving operating pressure as 1730kPa but after solution I am getting inlet pressure as 1697kPa so why the pressure is becoming low inspite of specifying its value?
Please help thanks in advance

"Physically, specifying the mass flux permits the total pressure to vary in response to the interior solution. This is in contrast to the pressure inlet boundary condition (see Section 7.3), where the total pressure is fixed while the mass flux varies. "
This is from the Fluent help: Mass Flow Inlet Boundary Conditions.

Incompressible flow require pressure difference. And therefore when we specify operating pressure we are specifying a reference pressure. You can refer the user guide for this section further on how to give the input parameters.