1 Flashcards
(26 cards)
The product of the force exerted on a steam turbine blade and the distance through which it moves determine the:
A: power
B: acceleration
C: work done
D: steam velocity
E: efficiency
C: work done
The velocity of the steam from a turbine nozzle is 500 m/s. The angle of the nozzle to blade motion is 20 degrees and the blade entrance angle is 33 degrees. What would be the blades linear velocity so that the steam enters without shock? Note: Use a velocity vector diagram.
A: 186 m/s
B: 180 m/s
C: 206.5 m/s
D: 192 m/s
E: 194.6 m/s
C: 206.5 m/s
From the following information on a single stage impulse turbine calculate the inlet angle of the moving blades. Nozzles inclined at 20 degrees to the plane of the wheel.
Steam exit from nozzles at 500 m/s
Blade ring mean diameter = .95m
Rotation speed = 3600 rpm
Note: use a velocity-vector diagram.
A: 34 degrees 24’
B: 36 degrees 22’
C: 39 degrees 20’
D: 39 degrees 45’
E: 30 degrees 28’
E: 30 degrees 28’
For what type of steam turbine does steam leakage across blade tips represent a loss of work?
A: reheat
B: back pressure
C: condensing units
D: impulse
E: reaction
E: reaction
In terms of steam turbine nozzles, shock or turbulent waves at the outlet of a nozzle result:
A: from the outlet pressure being lower than the critical pressure
B: when superheated steam is used
C: when the nozzles have considerable wear.
D: when the steam has become saturated
E: from a sudden reduction of load
A: from the outlet pressure being lower than the critical pressure
Steam turbines are employed to drive generators:
A: are back pressure machines
B: are condensing machines
C: frequently practice velocity compounding with reheat
D: combine condensing, reheating and non-automatic extraction steam flows
E: have reheating and compounding sections
D: combine condensing, reheating and non-automatic extraction steam flows
At the inlet or high pressure stages of an impulse turbine a:
A: large number of nozzles are used each with a large pressure drop
B: small number of nozzles are used each with a large pressure drop
C: small number of nozzles are used each with a small pressure drop
D: large number of nozzles are used each with a small pressure drop
E: singular large nozzle is most common
B: small number of nozzles are used each with a large pressure drop
Tandem-compound steam turbines:
A: have only one shaft
B: one high, one intermediate and a low pressure cylinder
C: usually have two and sometimes three shafts
D: have two shafts
E: have more than one shaft
A: have only one shaft
Correct steam turbine alignment is maintained under all operating conditions by provisions made to allow for:
A: axial expansion of the thrust and journal bearings
B: expansion of the journal bearings
C: axial and radial expansion
D: expansion of the turbine casing
E: movements of the steam piping to and from the turbine
C: axial and radial expansion
Bending moments and centrifugal forces:
A: control the output of the turbine
B: impose the maximum length of the turbine rotor
C: are not a factor with impulse turbine blading
D: place great strain on the root of the blades
E: place great strain on the tip of the blades
D: place great strain on the root of the blades
Steam leaves the nozzle of a single stage impulse turbine at a velocity of 450 m/s at 21 degrees to the plane of rotation of the blades. The blades linear velocity is 225 m/s. Assuming the steam leaves the blades in an axial direction what is the outlet blade angle? note: neglect friction, use a velocity-vector diagram.
A: 12 degrees 17’
B: 19 degrees 12’
C: 21 degrees 31’
D: 27 degrees 16’
E: 29 degrees 9’
D: 27 degrees 16’
The outlet velocity of steam from a turbine nozzle is 600 m/s, directed on to the blades at 20 degrees to the direction of blade movement. If the steam enters without shock when the linear velocity of the blades is 240 m/s what will be the inlet angles of the blades? Note: A velocity-vector diagram is essential. Neglect friction.
A: 39 degrees 11’
B: 39 degrees 22’
C: 41 degrees 17’
D: 40 degrees 15’
E: 32 degrees 22’
E: 32 degrees 22’
Partitions between pressure stages of an impulse turbine hold nozzles and seals between stages. These are called:
A: stage separators
B: labyrinth
C: diaphragms
D: shrouds
E: steam chest
C: diaphragms
In terms of steam turbine nozzles, shock or turbulent waves at the outlet of a nozzle result:
A: from the outlet pressure being lower than the critical pressure
B: when superheated steam is used
C: when the nozzles have considerable wear
D: when the steam has become saturated
E: from a sudden reduction of load
A: from the outlet pressure being lower than the critical pressure
The critical pressure ratio for superheated steam through a turbine nozzle is:
A: 1.05
B: 0.58
C: 1
D: 0.55
E: 0.97
D: 0.55
What controls the shafts axial position to maintain clearances between stationary and moving elements of each stage?
A: sliding feet
B: flexible couplings
C: journal and thrust bearings
D: sliding keyways
E: thrust bearings
E: thrust bearings
Double-flow principle, balance piston, coupling together in tandem of the high intermediate units, and causing steam to flow through each in opposite directions are all methods to eliminate the need for:
A: thrust bearings in impulse steam turbines
B: thrust bearings in reaction steam turbines
C: large thrust bearings in impulse steam turbines
D: journal bearings
E: large thrust bearings in reaction turbines
E: large thrust bearings in reaction turbines
The convergent-divergent steam nozzle has clearly defined named sections: inlet, throat, and outlet. The divergent nozzles:
A: have the throat near the inlet
B: have throat near the outlet
C: have no throat
D: consider the inlet as a throat
E: consider the outlet as a throat
C: have no throat
What is used to reduce the load on steam turbine thrust bearings?
A: dummy pistons
B: flexible couplings
C: ridged couplings
D: pressure-fed bearings
E: sliding keyways
A: dummy pistons
Turbines that use special governors and valves between selected turbine stages to control extracted-steam pressure at desired levels are called:
A: bleeder turbines
B: extraction turbines
C: topping turbines
D: mixed pressure turbines
E: automatic extraction turbines
E: automatic extraction turbines
Dry steam at 650 kPa absolute flows through a nozzle. The outlet pressure is 400 kPa absolute. What type of nozzle would be used:
A: convergent
B: fixed guide blades
C: rings of fixed blading
D: convergent-divergent
E: curtis nozzle
I feel that the answer is divergent
A: convergent
Axial thrust on steam turbine rotors is caused by:
A: deterioration of thrust bearings
B: governor hunting
C: overloading of the turbine
D: unstable running caused from low load conditions
E: pressure and velocity differences across the rotor blades
E: pressure and velocity differences across the rotor blades
A convergent steam turbine nozzle is used if:
A: the outlet pressure is typically greater than about 0.5 of the inlet pressure for both saturated and superheated steam
B: the steam quality was inconsistent
C: very wet steam is being used
D: high pressure steam is being used
E: the outlet pressure is to be less than 0.5 of the inlet pressure
A: the outlet pressure is typically greater than about 0.5 of the inlet pressure for both saturated and superheated steam
For high temperature blades on large steam turbines to achieve the required strength and oxidation-erosion resistance what material is used?
A: carbon steel
B: alloyed chrome steel
C: modified stainless steel
D: leaded nickel-brass
E: mechanite
B: alloyed chrome steel
