Turbomachinery MCQs 2026

Cavitation in turbines occurs at

1. Arunner outlet where pressure may drop below vapour pressure✓
2. Bonly inlet penstock high pressure always✓
3. Conly draft tube exit above atmospheric always preventing✓
4. Donly in air✓

Specific speed for hydraulic turbines classifies

1. Arunner type suitable for head and flow✓
2. Bonly electrical frequency✓
3. Conly coal ash content✓
4. Donly lubricant ISO grade✓

Kaplan turbine has

1. Aaxial flow runner with adjustable blades and guide vanes✓
2. Bonly fixed Pelton buckets✓
3. Conly steam nozzles✓
4. Donly gear pump lobes✓

Francis turbine is

1. Apure impulse jet only✓
2. Bonly vertical Kaplan only always✓
3. Cmixed-flow reaction turbine with adjustable wicket gates✓
4. Donly gas turbine✓

Pelton turbine is

1. Aimpulse turbine with tangential jets on buckets✓
2. Breaction runner fully submerged axial only always✓
3. Conly steam turbine condensing✓
4. Donly wind turbine✓

Hydraulic turbine converts

1. Aonly electrical to thermal✓
2. Bonly compressed air to vacuum✓
3. Cfluid energy (head) to mechanical shaft power✓
4. Donly chemical bond energy✓

Slip factor in centrifugal impeller accounts for

1. Arelative eddy reducing whirl component at exit✓
2. Bonly bearing friction✓
3. Conly paint thickness✓
4. Donly foundation vibration✓

Axial compressor used in

1. Aonly domestic water well exclusively✓
2. Bonly hydraulic press oil only✓
3. Conly boiler feed vacuum only✓
4. Dgas turbines and jet engines for high mass flow✓

Choke (stonewall) in compressor map is

1. Aminimum flow point✓
2. Bmaximum flow limited by sonic conditions at some section✓
3. Conly surge point✓
4. Donly shutoff head✓

Surge in centrifugal compressor is

1. Aflow instability with oscillation and possible damage✓
2. Bsteady maximum efficiency point always✓
3. Conly lubrication failure✓
4. Donly motor bearing grease colour✓

Polytropic efficiency of compressor accounts for

1. Aonly ideal isentropic without losses✓
2. Bonly mechanical bearing colour✓
3. Conly inlet filter mesh size aesthetic✓
4. Dreal irreversible compression path✓

Isothermal compression is more efficient than adiabatic because

1. Ano work is required ever✓
2. Bpressure never rises✓
3. Cheat is removed keeping temperature constant reducing work✓
4. Dvolume is constant✓

Reciprocating compressor achieves

1. Aonly very low pressure vacuum always without stages✓
2. Bhigh pressure ratio with staged cylinders✓
3. Conly axial flow without valves✓
4. Donly isothermal expansion without work✓

Centrifugal compressor is

1. Aonly reciprocating piston without valves✓
2. Bonly vacuum pump water ring exclusively always✓
3. Cdynamic compressor with radial or axial impellers✓
4. Donly heat exchanger✓

Compressor raises

1. Aonly liquid water head without density change much✓
2. Bonly solid particles✓
3. Conly vacuum without pressure rise✓
4. Dpressure of gas by doing work on it✓

Foot valve on pump suction prevents

1. Aonly discharge pressure rise✓
2. Bdrainback of liquid when pump stops✓
3. Conly motor overheating electrically always✓
4. Donly cavitation at discharge✓

Priming of centrifugal pump is needed because

1. Ait is positive displacement always✓
2. Bit cannot evacuate air effectively from suction to start pumping✓
3. Cimpeller is sealed without clearance✓
4. Donly when pumping mercury always✓

VFD on pump motor saves energy by

1. Aalways running at full speed✓
2. Bclosing suction valve✓
3. Creducing speed to match required duty point✓
4. Dincreasing static head artificially✓

Throttling control of pump discharge valve

1. Aalways improves efficiency at all points✓
2. Bchanges impeller diameter✓
3. Cchanges speed without VFD✓
4. Dreduces flow but wastes energy as valve loss✓

System curve for piping network represents

1. Ahead required versus flow from friction and static lift✓
2. Bonly pump efficiency✓
3. Conly impeller diameter✓
4. Donly motor slip✓

Pump characteristic curve plots

1. Aonly temperature versus time✓
2. Bhead versus flow rate at constant speed✓
3. Conly voltage versus current motor only✓
4. Donly stress versus strain metal✓

Axial flow pump is suited for

1. Avery high head low flow exclusively always✓
2. Bonly gases only✓
3. Chigh flow low head applications✓
4. Donly molten metal always✓

Gear pump is

1. Apositive displacement rotary pump with meshing gears✓
2. Bonly axial fan✓
3. Conly Francis turbine✓
4. Donly steam condenser✓

Reciprocating pump gives

1. Apulsating flow; needs accumulator sometimes✓
2. Bperfectly steady flow always without devices✓
3. Conly radial discharge✓
4. Donly vacuum without valves✓

Gas turbine compressor consumes

1. Azero power always✓
2. Bonly generates electricity without shaft power split✓
3. Conly heats water✓
4. Dsignificant portion of turbine output (high back work ratio)✓

Gas turbine cycle is

1. ARankine liquid only✓
2. BCarnot refrigerator only✓
3. CBrayton cycle (compressor, combustor, turbine)✓
4. DStirling regenerator only✓

Regenerative feedwater heating in steam cycle

1. Aonly rejects all heat to cooling tower✓
2. Bonly burns more coal without recovery✓
3. Conly compresses air✓
4. Dextracts steam from turbine to heat feedwater✓

Reheat cycle in steam plant

1. Aonly condenses all steam mid turbine✓
2. Bonly bypasses turbine entirely✓
3. Conly heats feedwater in deaerator exclusively✓
4. Dreturns steam to boiler for reheating between turbine sections✓

Pressure compounding (Rateau) drops pressure

1. Aonly once in condenser✓
2. Bin multiple nozzle stages each followed by moving blades✓
3. Conly in boiler drum✓
4. Donly in feedwater heater✓

Velocity compounding in steam turbine

1. Aonly one row without pressure drop✓
2. Bonly hydraulic Pelton✓
3. Cuses multiple moving blade rows with stationary reversing blades✓
4. Donly axial compressor✓

De Laval impulse steam turbine has

1. Aonly low speed Kaplan hydraulic✓
2. Bonly reciprocating piston✓
3. Csingle velocity-compounded or simple impulse wheel with high speed✓
4. Donly centrifugal pump✓

Steam turbine converts

1. Aonly chemical fuel without expansion✓
2. Bthermal energy of steam to shaft work✓
3. Conly water head hydraulic✓
4. Donly wind kinetic✓

Reaction turbine stage has pressure drop

1. Aonly in nozzles upstream of wheel completely✓
2. Bonly in condenser hotwell✓
3. Cin both fixed blades and moving blades✓
4. Donly in feed pump✓

Impulse turbine stage pressure drop occurs

1. Aentirely in runner blades submerged✓
2. Bonly in condenser✓
3. Cin fixed nozzles; runner at atmospheric pressure region✓
4. Donly in boiler✓

Draft tube on reaction turbine recovers

1. Aonly increases velocity deliberately wasting energy✓
2. Bonly filters sediment✓
3. Ckinetic energy at runner exit by decelerating flow✓
4. Donly lubricates bearings✓

Multistage centrifugal pump uses

1. Aseveral impellers in series on one shaft for high head✓
2. Bonly one impeller always✓
3. Conly gear teeth pumping✓
4. Donly steam ejector✓

Specific speed Ns of pump is indicator of

1. Aonly motor current✓
2. Bonly pipe colour✓
3. Conly oil viscosity without flow✓
4. Dpump type (radial, mixed, axial) best suited✓

Affinity laws: pump power varies with speed as

1. AN linearly✓
2. BN cubed✓
3. CN squared only✓
4. Dindependent of N✓

Affinity laws: pump head H varies with speed as

1. AN squared✓
2. BN linearly✓
3. CN cubed for head only wrong✓
4. Dindependent of N✓

Affinity laws for centrifugal pump when speed changes: flow Q varies

1. Awith N squared✓
2. Bdirectly with speed N✓
3. Cinversely with N✓
4. Dindependent of N✓

NPSH required (NPSHr) is

1. Aalways zero for all pumps✓
2. Bminimum suction energy margin needed by pump design✓
3. Csame as discharge head always✓
4. Donly boiler drum level✓

NPSH available (NPSHa) depends on

1. Asuction conditions and fluid vapour pressure✓
2. Bonly discharge valve colour✓
3. Conly motor paint✓
4. Donly foundation bolt torque only✓

Cavitation in pumps occurs when

1. Apressure always above atmospheric everywhere✓
2. Bonly at discharge flange high pressure✓
3. Clocal pressure drops below vapour pressure forming vapour bubbles✓
4. Donly in solids✓

Pump power required is approximately

1. Aonly Q without head✓
2. Bonly H without flow✓
3. Conly density without g✓
4. Dρ g Q H / efficiency✓

Pump head H represents

1. Aonly power in kW directly✓
2. Benergy per unit weight of fluid (m of fluid)✓
3. Conly torque in N·m without speed✓
4. Donly temperature rise °C only✓

Positive displacement pump delivers

1. Ainfinite flow at zero pressure always without limit✓
2. Bonly radial flow without moving parts✓
3. Conly steam expansion✓
4. Dnearly constant volume per cycle regardless of pressure (until relief)✓

Centrifugal pump imparts energy to fluid primarily by

1. Aonly positive displacement trapping volume✓
2. Bcentrifugal force and diffusion in volute/casing✓
3. Conly electromagnetic field on electrons in metal✓
4. Donly gravity alone without rotation✓

Turbomachinery includes machines that transfer energy between

1. Aonly solid gears without fluid✓
2. Bonly electrical resistors✓
3. Cfluid and rotor by dynamic action✓
4. Donly belt friction dry only✓

Fan differs from compressor in that fan has

1. Avery high pressure ratio multistage always✓
2. Bonly handles liquids✓
3. Conly generates vacuum below 0 absolute✓
4. Dlow pressure rise with high volume flow✓

Tip clearance in turbomachinery causes

1. Ainfinite efficiency gain✓
2. Bleakage reducing efficiency✓
3. Czero flow always✓
4. Donly structural strengthening without loss✓

Blade twist in axial machines accommodates

1. Avarying relative flow angle along span✓
2. Bonly constant incidence at all radii without twist✓
3. Conly paint colour gradient✓
4. Donly bolt pattern✓

Degree of reaction for turbine stage is

1. Aalways zero for Francis✓
2. Balways 1 for Pelton impulse✓
3. Conly boiler efficiency✓
4. Dfraction of enthalpy drop in rotor versus total stage drop✓

Turbine isentropic efficiency compares

1. Aonly mechanical bearing loss✓
2. Bactual enthalpy drop to isentropic enthalpy drop✓
3. Conly generator copper loss✓
4. Donly cooling tower evaporation✓

Specific speed of a pump indicates whether the design is

1. Aonly electrical motor RPM nameplate only✓
2. Bcentrifugal radial, mixed-flow or axial type✓
3. Conly pipe diameter schedule only✓
4. Donly oil viscosity grade only✓

Cavitation erosion on impeller appears as

1. Apitting and material loss on low-pressure side of blades✓
2. Bonly uniform polishing beneficially✓
3. Conly paint peeling decorative✓
4. Donly magnetic scaling✓

Water hammer in piping is caused by

1. Asteady laminar flow only✓
2. Bonly water heating without motion✓
3. Csudden velocity change creating pressure surge✓
4. Donly air filtration✓

Series operation of pumps adds

1. Aheads at same flow (approximately)✓
2. Bflows at same head always✓
3. Conly temperatures✓
4. Donly electrical phases✓

Turbocharger on diesel engine uses

1. Aexhaust gas turbine driving compressor for intake boost✓
2. Bonly hydraulic pump for steering✓
3. Conly wind turbine on roof✓
4. Donly steam ejector✓

Choking in nozzle occurs when

1. Aflow is subsonic everywhere always✓
2. BMach number reaches unity at throat✓
3. Cpressure ratio is zero✓
4. Dtemperature is absolute zero✓

Stator blades in axial compressor

1. Aincrease pressure and direct flow to next rotor row✓
2. Bonly extract power from shaft✓
3. Conly add fuel✓
4. Donly condense steam✓

Nozzle guide vanes in gas turbine direct flow onto

1. Aonly compressor rotor exclusively without stator✓
2. Bonly combustor liner✓
3. Conly afterburner✓
4. Dturbine rotor blades at correct angle✓

Turbine blade cooling in gas turbines uses

1. Aonly water jacket like diesel engine block always✓
2. Bonly external ice spray✓
3. Conly vacuum insulation✓
4. Dbleed air from compressor through internal passages✓

Wear ring clearance increase in pump causes

1. Ahigher efficiency always✓
2. Blower NPSHr always beneficially without limit✓
3. Cinternal recirculation leakage reducing efficiency✓
4. Dzero vibration✓

Mechanical seal in pump prevents

1. Aonly radial flow in impeller✓
2. Bleakage along shaft at casing penetration✓
3. Conly cavitation inception✓
4. Donly suction air ingestion always✓

Balancing holes or drum in pump impeller reduce

1. Aradial seal wear only aesthetic✓
2. Bonly motor RPM✓
3. Caxial hydraulic thrust on bearings✓
4. Donly fluid viscosity✓

Double-suction impeller splits flow to

1. Aincrease axial thrust deliberately✓
2. Beliminate need for bearings✓
3. Creduce axial thrust and improve inlet area✓
4. Donly pump gases without liquid✓

Impeller eye diameter affects

1. Aonly discharge flange bolt pattern✓
2. Bsuction performance and NPSHr✓
3. Conly paint colour✓
4. Donly foundation rebar✓

Diffuser in compressor or pump casing converts

1. Akinetic energy to pressure energy✓
2. Bpressure to kinetic only wasting energy✓
3. Conly heat to work✓
4. Donly work to chemical energy✓

Cavitation number or Thoma sigma is used for

1. Aonly pump NPSH in all fluids identically without context✓
2. Bonly compressor surge margin✓
3. Conly boiler TDS✓
4. Dpredicting cavitation inception in hydraulic turbines✓

Synchronization of generator to grid requires

1. Aonly random connection timing✓
2. Bonly maximum current inrush deliberately✓
3. Conly disconnecting excitation✓
4. Dmatching voltage, frequency and phase sequence✓

Runaway speed of hydraulic turbine occurs when

1. Aload increases to maximum✓
2. Bwater flow stops instantly✓
3. Cwicket gates weld open only without overspeed✓
4. Dload is lost and flow continues accelerating runner✓

Turbine governing maintains

1. Aonly constant inlet temperature without control✓
2. Bonly maximum vibration✓
3. Cspeed or power output under varying load✓
4. Donly colour of lubricant✓

Jet pump (ejector) entrains fluid using

1. Aonly positive displacement piston✓
2. Bonly gear mesh trapping✓
3. Conly nuclear radiation✓
4. Dhigh-velocity motive fluid✓

Hydraulic ram pump uses

1. Awater hammer effect to lift portion of water without external power✓
2. Belectric motor always required✓
3. Csteam boiler always✓
4. Donly compressed air from factory✓

Pump turbine (reversible) in pumped storage

1. Aonly burns natural gas✓
2. Bpumps water uphill off-peak and generates on-peak✓
3. Conly compresses air without water✓
4. Donly distills water✓

Wind turbine extracts energy from

1. Akinetic energy of moving air✓
2. Bonly geothermal steam underground✓
3. Conly tidal salinity gradient✓
4. Donly nuclear fission✓

Bypass ratio in turbofan is ratio of

1. Afuel to air ratio only✓
2. Bcompressor stages to turbine stages only✓
3. Cmass flow through fan bypass duct to core flow✓
4. Dinlet diameter to outlet only✓

Turbojet engine thrust arises from

1. Aonly propeller blade lift without exhaust✓
2. Bonly boiler steam pressure✓
3. Conly hydraulic ram force✓
4. Dmomentum change of exhaust gas plus pressure difference at nozzle✓

Blower provides

1. Aonly vacuum 0 absolute✓
2. Bonly filtration without pressure✓
3. Conly steam superheat✓
4. Dintermediate pressure rise between fan and compressor✓