Question 674Steam Plants - Assistant Engineer

The correct answer is C) equalizing holes provided in the turbine wheel. The equalizing holes in the turbine wheel allow the pressure on both sides of the wheel to equalize, preventing any appreciable axial thrust from being imparted to the rotor. This is because the pressure drop across the moving blades is balanced by the pressure drop through the nozzle diaphragms, resulting in a net zero axial force on the rotor. The other answer choices are incorrect because: A) The dummy piston and cylinder arrangement is not the primary reason for the lack of axial thrust. B) The decreasing steam velocity through the nozzle diaphragms does not directly prevent axial thrust. D) The pressure drop through the moving blades is not the main factor in preventing axial thrust.