Gas turbine engines

Question 1

gas turbine components

Answer 1

compressor, combustion chamber, turbine. components

Question 2

compressor

Answer 2

draws in air and compresses it

Question 3

combustion chamber

Answer 3

fuel pumped in and ignited burning compressed air

Question 4

turbine

Answer 4

hot gasses converted to work. drives compressor and external load

Question 5

radial flow compressors

Answer 5

Pros: simple design, not as expensive, good for low compression ratios.
Cons: difficult to stage, less efficient

Question 6

axial flow compressors

Answer 6

Pros: most common, more compact, has multi-stage high compression ratios, more efficient
cons: expensive, vulnerable to foreign object debris/damage (FOD) via intakes

Question 7

compressed air usage

Answer 7

primary (30%) secondary air (65%) film cooling air (5%)

Question 8

primary air

Answer 8

passes directly to combustor for combustion process. 30%

Question 9

secondary air

Answer 9

passes through perforated holes of inner shell & mixes with combustion gasses. cools gassesfrom the combustor to the turbine. prevents heating damage to the turbine. 60%

Question 10

film cooling air

Answer 10

insulates /cool turbine blades. 5%

Question 11

CAN combustion chamber type

Answer 11

centrifugal compressor

Question 12

ANNULAR combustion chamber type

Answer 12

larger, axial compressors (LM2500)

Question 13

CAN-ANNULAR combustion chamber type

Answer 13

smaller gas turbine engines

Question 14

gas turbines

Answer 14

converts kinetic energy of hot combustion gas to rotational energy. Uses vanes (nozzles) and blades similar to the turbine. drives the compressor and an external load. self-sustaining after start-up

Question 15

starter

Answer 15

on accessory gear box. process sequence: rotate compressor shaft using compressed air, fuel injected into combustor, electric spark provides initial ignition, combustion self sustaining after start

Question 16

auxiliaries

Answer 16

on accessory gear box. essential systems for operation: lube oil, fuel pump, generator (some platforms)

Question 17

Brayton cycle

Answer 17

intake, compression, combustion, expansion, exhaust. cycle

Question 18

GTE advantages

Answer 18

can burn two types of fuel, greater fuel efficiency (compared to diesels), high reliability (GTE on ships are from planes), less vibration, little or no cooling water required, power-to-weight ratio, quicker response time (faster acceleration/deceleration), rapid start time, reduced manning requirements

Question 19

GTE disadvantages

Answer 19

many components cannot be repaired in place (diesel repaired on deployment), do not do well in sandy/high salt areas, high pitched noise, inefficient at low or partial loads, large quantities of hot exhaust (huge IR target) new stacks cool exhaust, many parts under high stress, need large quantities of air

Question 20

single shaft design

Answer 20

power coupling on same shaft as turbine, same shaft drives compressor rotor and engine power components.

Efficiently operates at constant speeds, maintains fairly constant load , no rpm changes needed

Question 21

split shaft design

Answer 21

gas generator turbine drives compressor. a separate power turbine, driven by exhaust from gas generator turbine, drives the power coupling

used in propulsion, GTE is AERODYNAMICALLY coupled to power turbine NOT mechanically both turbines operate AT INDEPENDENTLY efficient speeds

Question 22

changing speed controllable pitch GTE

Answer 22

prop blade pitch, lower speed changes 0-13(5) knots (at the pier), shaft RPM higher speed changes typically 13-30+

Question 23

turboshaft

Answer 23

rotors driven entirely by power turbine, no thrust from engine exhaust. MH-60 seahawk and MH-53 sea stallion

Question 24

turboprop

Answer 24

single shaft, turbine drives propeller thru gearbox. some additional thrust from engine exhaust. P-3 ORION, C-2 GREYHOUND, E-2 HAWKEYE

Question 25

turbojet

Answer 25

thrust achieved solely through exhaust. ex: mid range missiles, variations of Tomahawk cruise missiles

Question 26

turbofan

Answer 26

thrust from engine exhaust, additional thrust from fan. More efficient than turbojet in most application. F/A -18 HORNET, EA-18 GROWLER, joint strike (JSF) & poseidon