Which statement is correct about the flow in a divergent jet engine inlet I The static pressure remains constant in flow direction II The total temperature remains constant in flow direction ? Experience > lift > off
I incorrect ii correct.
Which of these statements about compressor stall are correct or incorrect I A compressor stall is most likely to occur in a compressor designed for a high pressure ratio operating at low RPM II A ?
Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at low rpm ii a compressor stall most likely to occur when air flow stagnates in rear stages of compressor I correct ii correct. Like stall of a wing compressor stall caused a breakdown of airflow
if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur
a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow
when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow)
you can prevent this dumping some late stage air to atmosphere (via bleed valves).
In a compressor stage if the axial air velocity increases more than the rotor blade velocity the ?
In a compressor stage if axial air velocity increases more than rotor blade velocity Stall margin increases.
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
a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow
when incoming air flow speed high blade angle of attack will be low stall margin increases (there less risk to encounter a compressor stall). Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at high rpm ii a compressor stall most likely to occur when air flow stagnates in rear stages of compressor I incorrect ii correct. Like stall of a wing compressor stall caused a breakdown of airflow
if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur
a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow
when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow)
you can prevent this dumping some late stage air to atmosphere (via bleed valves). With regard to a twin spool turbofan an abortive start hung start will result in N2 speed stabilising at a lower than normal rpm a subsequent increase in egt.
after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall
hung starts may be caused
starter air pressure too low to accelerate engine to self sustaining speed
premature starter deactivation
fod (foreign object debris) to compressor
faulty pressurizing valves not opening at scheduled fuel pressure setting
incorrect scheduling of hp compressor igv variable stators
turbine section damage. Which of following statements correct about flow in a divergent subsonic gas turbine engine intake i the dynamic pressure increases in flow direction ii the static temperature increases in flow direction I incorrect ii correct.
after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall
hung starts may be caused
starter air pressure too low to accelerate engine to self sustaining speed
premature starter deactivation
fod (foreign object debris) to compressor
faulty pressurizing valves not opening at scheduled fuel pressure setting
incorrect scheduling of hp compressor igv variable stators
turbine section damage. One of functions of a gas turbine engine subsonic intake to Decrease airflow velocity.
after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall
hung starts may be caused
starter air pressure too low to accelerate engine to self sustaining speed
premature starter deactivation
fod (foreign object debris) to compressor
faulty pressurizing valves not opening at scheduled fuel pressure setting
incorrect scheduling of hp compressor igv variable stators
turbine section damage. 8 One of advantages of multiple spool jet engine designs that A smaller air starter driving only a single spool can be used.
the air starter motor possibly most popular starting system presently in use it light simple to use very economical utilizing low pressure air the air starter motor fastened to accessory gearbox of engine the sources of air available engine start in order of preference they are the aircraft apu
the ground power unit
a cross bleed start where air from an already started engine used
air from one of these sources fed through an electrically controlled start valve to air inlet to rotate turbine rotor is then exhausted
on a multiple spool jet engine a small air starter motor can drive a single spool which when started permits to start other spools. 9 Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at high rpm ii a compressor stall most likely to occur when air flow stagnates in front stages of compressor I incorrect ii incorrect. Like stall of a wing compressor stall caused a breakdown of airflow
if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur
a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow
when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow)
you can prevent this dumping some late stage air to atmosphere (via bleed valves). 10 After a successful start of a high bypass turbofan engine air starter Is disengaged the coupling between engine n2 spool starter the use of centrifugal forces. Air starting used on most commercial some military jet engines it has many advantages over other starting systems is comparatively light simple economical to operate 10 an air starter motor transmits power through a reduction gear clutch to starter output shaft which connected to engine
the starter turbine rotated air taken from an external ground supply an auxiliary power unit (a p u ) or as a cross feed from a running engine the air supply to starter controlled an elec trically operated control pressure reducing valve that opened when an engine start selected is automatically closed at a predetermined starter speed the clutch also automatically disengages as engine accelerates up to idling rpm the rotation of starter ceases. 11 Both gas turbine and piston engines use a cycle made up of induction compression combustion and exhaust phases which of these statements about a gas turbine are correct or incorrect i the process in a gas turbine engine continuous ii theoretically combustion occurs at constant volume I correct ii incorrect.
piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder
turbine engine combustion process continuous occurs at constant pressure. 12 Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at low rpm ii a compressor stall most likely to occur when air flow stagnates in front stages of compressor I correct ii incorrect. Like stall of a wing compressor stall caused a breakdown of airflow
if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur
a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow
when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow)
you can prevent this dumping some late stage air to atmosphere (via bleed valves). 13 The following problems may occur when starting a twin spool turbofan engine No n rotation although n2 may accelerate normally.
during engine start compressor very inefficient if engine experiences more than usual difficulty accelerating (due to such problems as early starter cut out fuel mis scheduling or strong tailwinds) engine may spend a considerable time at very low rpm (sub idle) normal engine cooling flows will not be effective during sub idle operation turbine temperatures may appear relatively high this known as a hot start. 14 Both gas turbine and piston engines use a cycle made up of induction compression combustion and exhaust phases which of these statements about a gas turbine are correct or incorrect i the process in a gas turbine engine intermittent ii theoretically combustion occurs at constant pressure I incorrect ii correct.
piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder
turbine engine combustion process continuous occurs at constant pressure. 15 The most unfavourable conditions adequate inlet air flow of a turbofan engine are Maximum take off thrust zero forward speed strong crosswind conditions.
piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder
turbine engine combustion process continuous occurs at constant pressure. 16 If a twin spool gas turbine engine controlled a conventional n2 control system rupture of lp shaft may result in Overspeed of lp turbine. In a twin spool engine lp turbine connected to lp compressor hp turbine connected to hp compressor the lp turbine drives lp compressor if a rupture occurs it may result in an overspeed of lp turbine. 17 The rotor blades of an axial compressor of a gas turbine engine are often mounted on a disk or drum using a 'loose fit' because this Limits damage to blades due to vibration. In a twin spool engine lp turbine connected to lp compressor hp turbine connected to hp compressor the lp turbine drives lp compressor if a rupture occurs it may result in an overspeed of lp turbine. 18 For a turbine engine self sustaining speed relates to minimum rpm at which engine Will continue to operate without any starter motor assistance. In a twin spool engine lp turbine connected to lp compressor hp turbine connected to hp compressor the lp turbine drives lp compressor if a rupture occurs it may result in an overspeed of lp turbine. 19 The primary function of diffuser located between compressor and combustion chamber of a gas turbine engine to Decrease flow velocity. Before combustion can proceed air velocity must be greatly reduced
air leaves compressor through exit guide vanes which convert radial component of air flow out of compressor to straight line flow the air then enters diffuser section of engine which a very divergent duct the primary function of diffuser structure aerodynamic the divergent duct shape converts most of air's velocity (pi) into static pressure (ps) as a result highest static pressure lowest velocity in entire engine at point of diffuser discharge combustor inlet other aerodynamic design considerations that are important in diffuser section arise from need a short flow path uniform flow distribution low drag loss. 20 A fadec on a gas turbine engine Is single fault tolerant. Single input data failure will not affect normal operation (a 'full authority digital engine contro single fault tolerant)
a fadec an engine control system in which primary functions use digital electronics the electronic engine control (eec) unit has full range authority over engine power or thrust. Exclusive rights: Content under private and protected license, reproduction prohibited and prosecuted.
