Chapter 71- Gas Turbines Flashcards Preview

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Flashcards in Chapter 71- Gas Turbines Deck (53):
1

The three things a gas turbine is considered

*constant flow rotors engine * heat engine * prime mover

2

List two facts about early gas turbines

* handicapped by lack of metal that withstand high temps * air compressor and turbine had very love efficiency

3

____ of the power is used for the air compression on a gas turbine

2/3

4

Output power or ____ depends in _____

Power rating Mass of hot gas

5

Output increases in a gas turbine when using

Air of maximum density

6

An example of aero turbine

Jet engine

7

An open system gas turbine

Air drawn from atmosphere and returned

8

Air and hot gas are _____ from compressor to turbine

Ducted

9

Turbine has to be brought up to ___% speed before the fuel is turned on

20-30

10

The two types of gas turbine

Aero derivative Land based

11

A simple turbine system has no (3)

*heat exchanger *regenerator *intercooler

12

A single shaft gas turbine

Has only one shaft. Compressor and turbine are coupled together

13

What is the majority of gas turbines in industry

Simple Open single shaft

14

Five advantages of the gas turbine

*higher power to weight ratio *low installed coat *low maintenance and operating cost *minimum cooling water *rapid start up and loading

15

List four disadvantages of gas turbines

*low mechanical and thermal efficiency *high noise level *limited types of fuel *NOx emissions

16

Compared to a steam plant and gas turbine is

Smaller and lighter

17

Absence of reciprocating motion and min wear of moving parts results in

Low maintenance and operating cost

18

Gas turbines require Minimal cooling water and is ideal for

Areas where water is scarce

19

What type of fuel does a turbine use

Clean liquid or gaseous fuels

20

What's the purpose of regenerators

Improve efficiency by recovering heat

21

Regenerators are more efficient with

Cold air

22

Heat recovered from exhaust gas

Reduces fuel quality

23

What are two main benefits from combining a gas turbine with a steam plant

*plant economy improves * reduction in boiler size

24

Gas turbines combined with steam plants are referred to as

Combine cycles

25

What are the two things that are important for an operator to understand about gas turbines

How the ambient temp and atmospheric pressure effects it

26

Atmospheric pressure affects _______ in a gas turbine

Internal combustion engine and boiler performance

27

Air temperature changes

Air density

28

Define manual start up

Operator starts all auxiliary systems and takes gas turbine to minimum governor setting

29

Define semi automatic start ups

Only auxiliary system and automatic control takes gas turbine to minimum governor setting

30

Define automatic starting methods

Operator pushes button

31

What should you do if the engine of a turbine doesn't start up within 90 seconds

Abort start up

32

If 50% rpm is not reached in 60 seconds what should you do

Abort cranking

33

Large turbines are fitted with

Serval governors

34

The over speed trip device will

Cut off fuel immediately

35

Gas turbine load control depends upon

The load shaft speed

36

List the five gas turbine alarm singals

High vibration Generator stator high temp Ignition tripped High differential pressure air intake Low lub oil pressure

37

What do you do with high vibrations

Close fuel supply

38

No ignition will result in

Fire or explosion

39

High differential air pressure indicates

Dirty air inlet filters

40

Why is lubrication essential

Lube bearings Cooling of bearings

41

Define a major overhaul turbine maintenance

A total strip down and checking or replacing

42

Define short shutdown turbine maintenance

Clean and replace air inlet filters, wash compressor blading and replace bearings and coupling

43

Aging factor results in

.5% in power and efficiency loss for 1000 hours of services

44

Why do we cool the turbine blades?

So they don't melt

45

HRSG

Heat recovery steam generator

46

Sag in a turbine shaft is called

Bowing

47

What is a regenerator

Takes heat from the exhaust to heat compressed air in the turbine

48

Define cogeneration

Takes hot exhaust gasses to boil water to produce steam Highest efficiency available

49

A major drawback of the gas turbine

Nox emissions are high Low mechanical efficiency

50

The compressor chamber of a gas turbine

Can be driven by the load turbine

51

Many typical steam plant auxiliaries are eliminated with a gas turbine due to its

SIMPLICITY

52

The temperature to which the air can be raised at the turbine inlet is

A indication of the units efficiency

53

DP

Differential Pressure