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Mechanical Interview Questions and Answers (Gas Turbine)

 Mechanical Interview Questions and Answers (Gas Turbine)

- What exactly is a gas turbine?

It's a four-step thermic machine that runs on admission, compression, combustion, and exhaust

- In a gas turbine, how many stages are there? 

Three phases

- How many stages does the compressor have?

17 levels

- What kind of compressor does the gas turbine have?

Compressor with axial flow.

- How many bleed valves does the compressor have?

There are four bleed valves.

- Air will be released through bleed valves at what stage of the compressor?

The compressor's eleventh stage.

- Why are bleed valves required for air bleeding?

Protection against pulsation during start-up

- When will these compressor bleed valves be shut off?

The speed relay (14HS) corresponds to a speed of 95 percent.

- In gas turbines, what is the minimum and maximum IGV position?

34 DGA is the minimum and 85 DGA is the maximum.

- When will IGV begin operations?

The speed relay (14HS) corresponds to a speed of 95%.

- In frames # 9 and # 6, how many combustion chambers are there?

There are 14 combustion chambers in Frame #9 and 10 combustion chambers in Frame #6.

- How many spark plugs are there?

2 pieces of spark plugs

- What kind of combustion system does a gas turbine have?

Type of reverse flow

- What is the location of spark plugs?

Nos. 13 and 14 combustion chambers

- What are the locations of flame detectors?

Nos. 4, 5, 10, and 11 are combustion chambers.

- What role does the combustion wrapper play?

The compressor discharge air flow is delivered to the combustion chambers through the combustion wrappers, which create a plenum. It serves as a supplemental support for the combustion chamber assembly.

The compressor discharge casing and the turbine shell, in turn, support the wrapping.

- Why are flame detectors necessary?

An indication of the presence or absence of flame must be given to the control system during the starting procedure.

- How do flame detectors function?

A lame sensor with a gas-filled detector makes up the UV flame sensor. The presence of UV

radiation released by a hydrocarbon flame sensitizes the gas within this flame sensor detector.

The amplifier impresses a D.C. voltage across the detector terminals.

If there is a flame, the ionization of the gas in the detector allows conduction in the circuit, which activates the electronic and produces a flame output. In the absence of flame, the output will be the polar opposite, defining "on flame."

- What exactly is the purpose of the gasoline nozzle?

The purpose of the fuel nozzle is to distribute liquid or gas fuel into the reaction zone of the

combustion liner in such a way that uniform quick and full combustion is achieved.

- What is the purpose of atomizing air?

To aid in the creation of a finely divided spray, atomizing air is combined with liquid fuel.

- What is transition pieces used for?

The hot gases are directed from the liners to the turbine's first stage nozzle by transition pieces. As a result, the hot gas flow is divided into 14 equal portions in the first nozzle area.

- What are the components of the combustion section?

Fuel nozzles, spark plug ignition, flame detectors, and crossfire tubes are all part of the combustion system.

- What are the components of the turbine section?

The turbine rotor, a turbine rotor, a turbine shell, nozzles, shrouds, exhaust frame, and exhaust diffuser are all part of the turbine section.

- What parts of the turbine rotor assembly are included?

Two wheel shafts, the first, second, and third stage turbine wheels with buckets, and two turbine spacers make up the turbine rotor assembly.

- What are diaphragms and what do they do?

Air leaking through the inner sidewall of the nozzles and turbine rotor is prevented by diaphragms. The nozzle diaphragms are attached to the inside diameters of both the second and third stage nozzle segments.

- What exactly is shroud?

Unlike the compressor blading, the turbine bucket tips run against annular curved segments called turbine shrouds rather than an inherent machined surface of the casing.

- What purpose do shrouds serve?

The shrouds' main purpose is to offer a cylindrical surface for reducing tip clearance leakage. The secondary purpose is to establish a high thermal barrier between the hot gases and the cooler shell.

The shell cooling load is considerably decreased, the shell diameter is controlled, the shell

roundness is maintained, and crucial turbine clearances are ensured by performing this duty.

- In a gas turbine, how many bearings are there?

Three bearings

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