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Concerning the fuel system high pressure shut off valve HPSOV of a gas turbine engine ? Test > topography

exemple question 173
Ignition activated before fuel delivered the hpsov to fuel nozzles.


Derated or reduced take offs save engine life primarily due to ?

exemple question 174
Derated or reduced take offs save engine life primarily due to Reduced low cycle fatigue damage. Low cycle fatigue where stress high enough deformation to occur this deformation will occur in turbine since it most sensitive to high temperatures.


The diagram shown in annex represents a twin spool turbofan Positions before and after air intake are located at numbers 1054 ?

exemple question 175
The diagram shown in annex represents a twin spool turbofan positions before and after air intake are located at numbers 1054 Reduced low cycle fatigue damage. Low cycle fatigue where stress high enough deformation to occur this deformation will occur in turbine since it most sensitive to high temperatures.


exemple question 176
What the average compression ratio of a centrifugal compressor Reduced low cycle fatigue damage. axial compressor radial compressor a centrifugal compressor will provide a compression ratio of 5 1 per stage (maximum) which relatively high compared to an axial compressor that achieves a ratio of only 1 2 1 per stage.


exemple question 177
If engine compressor air bled off engine anti icing or a similar system turbine temperature Reduced low cycle fatigue damage. Gorny21 the ratio of tertiary airflow around combustion flame tube that cools turbine decreases thus less cooling flow as warm air diverted anti icing so egt will increase as a result.


exemple question 178
Increasing frequency of variations in thrust setting during normal operation detrimental to life of hp turbine blades because Low cycle fatigue damage more severe. It commonly known that a metal subjected to repetitive or flunctuating stress will fail at a stress much lower than its ultimate strength failures occuring under cyclic loading are generally termed 'fatigue' the endurance of gas turbine engine to high temperature particularly marked the creep resistance of hp turbine blade alloy in turbine engines low cycle fatigue generally caused repeated loading cycles caused operation (i e starting or takeoff conditions) if a turbine blade goes through one takeoff max power setting it may be fine if it subjected to 8000 of them it may fail due to fatigue.


exemple question 179
An axial compressor when operating below its design speed has A tendency to stall in front stages. axial compressor radial compressor the stall of a blade occurs in same way as a wing stalls if angle of attack exceeds a set value blade/wing will stall the first stage of blades on a compressor are rotor blades when it turns air push rearwards increasing velocity onto blades behind but also pressure if horizontal flow low it results in a large angle of attack as this most likely at front of compressor it will tend to stall at front.


8
The compressor blades in a rotating gas turbine engine are held in position The mountings the resultant of aerodynamic centrifugal forces. axial compressor radial compressor the stall of a blade occurs in same way as a wing stalls if angle of attack exceeds a set value blade/wing will stall the first stage of blades on a compressor are rotor blades when it turns air push rearwards increasing velocity onto blades behind but also pressure if horizontal flow low it results in a large angle of attack as this most likely at front of compressor it will tend to stall at front.


9
Some gas turbine engines have multiple stages in hp and lp turbines Because one stage does not generate sufficient shaft power. axial compressor radial compressor the stall of a blade occurs in same way as a wing stalls if angle of attack exceeds a set value blade/wing will stall the first stage of blades on a compressor are rotor blades when it turns air push rearwards increasing velocity onto blades behind but also pressure if horizontal flow low it results in a large angle of attack as this most likely at front of compressor it will tend to stall at front.


10
In which part of a gas turbine engine are high temperature requirements most critical the materials used The combustion chamber front part of hp turbine. Usually titanium alloy the material used the combustion chamber high pressure turbine.


11
A twin spool engine with an inlet air mass flow of 500 kg/s and a hp compressor mass flow of 250 kg/s has a bypass ratio of The combustion chamber front part of hp turbine. bypass ratio = bypass mass flow / hp compressor mass flow 500 250 = 250 250 / 250 = 1.


12
A 'fan' stage of a ducted fan turbine engine driven The low pressure turbine. bypass ratio = bypass mass flow / hp compressor mass flow 500 250 = 250 250 / 250 = 1.


13
The oil supply to gas turbine engine bearings maintained in event of main oil filter becoming clogged Differential pressure opening bypass valve of main oil filter. bypass ratio = bypass mass flow / hp compressor mass flow 500 250 = 250 250 / 250 = 1.


14
One of purposes of compressor bleed valves to Decrease airflow across rear compressor stages whilst that across early stages increased. Bleed valves are fitted to prevent compressors stalling like stall of a wing compressor stall caused a breakdown of airflow the bleed valve removes excesss volume of air at low compressor speeds to increase flow over front compressor blades reduce flow over latter stages as speed of compressor increases bleed valve closes.


15
Turbine blade stages may be classed as either 'impulse' or 'reaction' in an impulse blade section pressure i across nozzle guide vanes ii across rotor blades (i) drops (ii) remains constant. nozzle guide vanes = stator the pressure drops across stator blades remains constant across rotor blades.


16
One advantage of having three instead of two spools in some high bypass turbofan engine that Fewer variable stator vanes variable inlet guide vanes are required to prevent compressor stall at low rotor speeds. Variable inlet guide vanes (v i g v s) are fitted to engines which have a particular problem with inherent compressor stall at low rpm or during engine acceleration or deceleration the vanes are fitted just in front of first rotor stage they can be automatically pivoted around their own axis to vary path of airflow going into compressor so maintaining proper relationship between compressor rotational speed airflow in front compressor stages at low compressor speeds v i g v s are angled to impart greatest amount of swirl to air thereby correcting relative airflow to obtain optimum angle of attack over rotor blades this optimum angle of attack allows a smooth rapid engine acceleration on a three spools high bypass turbofan engine an additional intermediate pressure compressor stage added reduces risk of compressor stall at low rotor speeds.


17
The compressor surge effect during acceleration prevented the Fuel control unit (f c u ). With modern engines there are various ways to control surge one of them the use of blow off valves (also called compressor bleed valves) on all modern turbine engines with electronic fuel control systems valves are controlled the fuel control unit the end result will be that blow off valve will reduce pressure in compressor to prevent surge.


18
Creep in a gas turbine engine The permanent increase in length of metal parts due to a combination of tensile stress high temperatures over a prolonged period. With modern engines there are various ways to control surge one of them the use of blow off valves (also called compressor bleed valves) on all modern turbine engines with electronic fuel control systems valves are controlled the fuel control unit the end result will be that blow off valve will reduce pressure in compressor to prevent surge.


19
About a twin spool compressor The low pressure spool runs at a lower rpm than high pressure spool. With modern engines there are various ways to control surge one of them the use of blow off valves (also called compressor bleed valves) on all modern turbine engines with electronic fuel control systems valves are controlled the fuel control unit the end result will be that blow off valve will reduce pressure in compressor to prevent surge.


20
In addition to providing 'customer' bleed aeroplane systems air may be bled from compressors of a turbofan engine to increase stall margin The low pressure spool runs at a lower rpm than high pressure spool. During engine starts most turbojet/turbofan engines use engine bleed air to reduce possibility of compressor stalls compressor stall occurs when compressor sucks too much air the turbine wheels to handle excessive pressure then builds aft of compressor the compressor blades stall (also happens with centrifugal type compressor) bleeding air from an engine (air bled just aft of compressor) relieves that excessive pressure the compressor can more easily 'push' sucked air behind him.



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