A hot start during starting of a turbine power plant is most likely caused by which of the following?

A hot start during starting of a turbine power plant is most likely caused by which of the following?

• A. The fuel/air mixture was excessively rich
• B. The ambient air temperature was too high
• C. The engine oil viscosity was too high
• D. The starter motor failed to supply enough rotations

Answer: (A)

Fuel-air balance during start controls how hot the combustion process will run. When the mixture is excessively rich, there is more fuel than the available air can completely burn. The extra fuel burns quickly and releases more energy in a shorter time, driving combustion and turbine inlet temperatures to unsafe levels. That rapid, high-temperature combustion is what defines a hot start, and it risks overheating components or tripping safety limits, so the control system will back off fuel to restore a proper balance. Other conditions affect starting in different ways. A high ambient temperature changes air density but doesn’t inherently cause the excessive heat of a hot start. A oil that’s too viscous makes the starter work harder and can slow rotation, but it doesn’t raise combustion temperature once ignition occurs. If the starter doesn’t deliver enough rotations, you’d see a failed or hung start rather than the characteristic overheating of a hot start.

Fuel-air balance during start controls how hot the combustion process will run. When the mixture is excessively rich, there is more fuel than the available air can completely burn. The extra fuel burns quickly and releases more energy in a shorter time, driving combustion and turbine inlet temperatures to unsafe levels. That rapid, high-temperature combustion is what defines a hot start, and it risks overheating components or tripping safety limits, so the control system will back off fuel to restore a proper balance.

Other conditions affect starting in different ways. A high ambient temperature changes air density but doesn’t inherently cause the excessive heat of a hot start. A oil that’s too viscous makes the starter work harder and can slow rotation, but it doesn’t raise combustion temperature once ignition occurs. If the starter doesn’t deliver enough rotations, you’d see a failed or hung start rather than the characteristic overheating of a hot start.