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Question 1
ప్రశ్న 1
Which statement best describes the fundamental working principle of a centrifugal pump?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A centrifugal pump is a rotodynamic machine that receives mechanical power through its shaft. The rotating impeller transfers energy to the liquid through its blades. This increases the liquid's angular momentum and total mechanical energy. Part of the velocity energy leaving the impeller can subsequently be converted into pressure energy in the casing or diffuser. Therefore Option A is correct.
వివరణ:
Question 2
ప్రశ్న 2
Which statement correctly describes the roles of the impeller and the volute or diffuser casing in a centrifugal pump?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The impeller is the rotating component through which shaft work is transmitted to the liquid. Water leaves the impeller with increased pressure and velocity. A volute or diffuser provides an expanding passage downstream of the impeller. The reduction in velocity through this passage permits part of the kinetic energy to be recovered as static pressure. Therefore Option A is correct.
వివరణ:
Question 3
ప్రశ్న 3
Why is priming generally required before starting an ordinary centrifugal pump that is not self-priming?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A conventional centrifugal pump is normally intended to operate with its casing filled with liquid. If air occupies the casing, its low density prevents the impeller from developing the pressure difference required to lift water effectively through the suction pipe. Priming removes this air and fills the pump and suction passage with liquid. A foot valve is often used to help retain liquid in the suction line after priming. Therefore Option A is correct.
వివరణ:
Question 4
ప్రశ్న 4
At the design condition of a centrifugal pump without inlet guide vanes, what assumption is commonly made regarding the inlet whirl velocity Vw1?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A simple centrifugal pump usually does not have inlet guide vanes imparting deliberate prewhirl. At the intended design condition, the liquid therefore approaches the impeller with negligible tangential velocity. The inlet whirl component Vw1 is consequently taken approximately as zero. This assumption simplifies the Euler pump equation considerably. Therefore Option A is correct.
వివరణ:
Question 5
ప్రశ్న 5
Under the usual sign convention for a centrifugal pump, which expression gives the ideal Euler head imparted to the liquid?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The Euler turbomachinery equation is obtained from the change in angular momentum of the fluid. For a pump, energy is transferred from the rotating impeller to the liquid. The work per unit mass is therefore U2Vw2 - U1Vw1 under the stated convention. Dividing this specific work by gravitational acceleration gives the corresponding Euler head. Therefore Option A is correct.
వివరణ:
Question 6
ప్రశ్న 6
For a centrifugal-pump impeller with backward-curved outlet blades, let beta2 be the blade angle measured from the tangent in the backward direction. Which ideal velocity-triangle relation is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For backward-curved blades, the outlet relative velocity has a tangential component opposite to impeller motion. From the outlet velocity triangle, tan(beta2) equals Vf2 divided by U2 minus Vw2. Rearranging this relation gives Vw2 = U2 - Vf2 cot(beta2). The relation assumes that the liquid follows the blade direction ideally and that slip is neglected. Therefore Option A is correct.
వివరణ:
Question 7
ప్రశ్న 7
A centrifugal-pump impeller has an outside diameter D2 = 0.40 m and rotates at N = 1200 rpm. What is its peripheral speed U2 approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Peripheral speed is U2 = pi D2 N/60. Substitution gives U2 = pi × 0.40 × 1200/60. This evaluates to approximately 25.13 m/s. The quantity represents the tangential speed of the impeller tip at the outlet radius. Therefore Option B is correct.
వివరణ:
Question 8
ప్రశ్న 8
A centrifugal-pump impeller has D2 = 0.40 m, outlet width b2 = 0.030 m and discharge Q = 0.060 m³/s. Neglect blade thickness and blockage. What is the outlet flow velocity Vf2 approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The flow area normal to the radial velocity at the impeller outlet is approximately pi D2 b2. This area is pi × 0.40 × 0.030 = approximately 0.03770 m². Continuity gives Vf2 = Q/(pi D2 b2). Substitution gives 0.060/0.03770 = approximately 1.592 m/s. Therefore Option B is correct.
వివరణ:
Question 9
ప్రశ్న 9
For a centrifugal pump, U2 = 25.13 m/s, Vf2 = 1.592 m/s and the backward-curved outlet blade angle beta2 = 30 degrees. Neglect slip. What is Vw2 approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For backward-curved blades, Vw2 = U2 - Vf2 cot(beta2). Since cot(30 degrees) is approximately 1.732, the correction term is 1.592 × 1.732 = approximately 2.757 m/s. Therefore Vw2 = 25.13 - 2.757 = approximately 22.38 m/s. The whirl component is smaller than U2 because the blades are backward curved. Therefore Option B is correct.
వివరణ:
Question 10
ప్రశ్న 10
A centrifugal pump has U2 = 25.133 m/s and Vw2 = 22.376 m/s. The liquid enters without prewhirl, so Vw1 = 0. What ideal Euler head is imparted to the liquid? Take g = 9.81 m/s².
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
With zero inlet whirl, the Euler head becomes HE = U2Vw2/g. Substitution gives HE = 25.133 × 22.376/9.81. The numerator represents the specific work transferred to the liquid in J/kg. The resulting ideal head is approximately 57.33 m. Therefore Option C is correct.
వివరణ:
Question 11
ప్రశ్న 11
What is the manometric head of a centrifugal pump?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Manometric head is the actual increase in total mechanical head produced by the pump. It includes the changes in pressure head, velocity head and elevation head between the selected suction and delivery sections. When suction and delivery pipes have the same diameter and negligible elevation difference across the pump, it may be approximated by the rise in pressure head. It is normally lower than the Euler head because of hydraulic losses. Therefore Option A is correct.
వివరణ:
Question 12
ప్రశ్న 12
At a pump suction flange, the gauge pressure is -40 kPa, velocity is 2 m/s and elevation is 0 m. At the delivery flange, the gauge pressure is 250 kPa, velocity is 3 m/s and elevation is 3 m. For water, what manometric head does the pump develop approximately? Take rho = 1000 kg/m³ and g = 9.81 m/s².
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Manometric head equals the rise in pressure head plus the rise in velocity head plus the elevation difference. The pressure-head increase is 290000/(1000 × 9.81) = approximately 29.56 m. The velocity-head increase is (3² - 2²)/(2 × 9.81) = approximately 0.255 m. Adding the elevation difference of 3 m gives approximately 32.82 m. Therefore Option C is correct.
వివరణ:
Question 13
ప్రశ్న 13
Which expression correctly defines the manometric efficiency of a centrifugal pump?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Euler head represents the ideal work head imparted by the impeller according to angular momentum. Manometric head is the actual increase in total head measured across the pump. Hydraulic losses make the manometric head smaller than the ideal Euler head. Their ratio is termed the manometric efficiency. Therefore eta_man = Hm/HE and Option A is correct.
వివరణ:
Question 14
ప్రశ్న 14
A centrifugal pump has an Euler head of 57.33 m and develops a manometric head of 50.0 m. What is its manometric efficiency approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Manometric efficiency is the ratio of manometric head to Euler head. Thus eta_man = 50.0/57.33. The result is approximately 0.872. Expressed as a percentage, this is about 87.2 percent. Therefore Option C is correct.
వివరణ:
Question 15
ప్రశ్న 15
Which expression gives the useful hydraulic output power of a centrifugal pump delivering discharge Q against manometric head Hm?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Each unit weight of liquid gains an amount of energy equal to the manometric head. The weight flow rate of the liquid is rho g Q. Multiplying weight flow rate by head gives power. Therefore useful hydraulic output power is rho g Q Hm. Hence Option A is correct.
వివరణ:
Question 16
ప్రశ్న 16
A centrifugal pump delivers Q = 0.080 m³/s against a manometric head of 35 m. What useful water power does it produce? Take rho = 1000 kg/m³ and g = 9.81 m/s².
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Useful hydraulic power is rho g Q Hm. Substitution gives 1000 × 9.81 × 0.080 × 35 W. This equals 27468 W. Expressed in kilowatts, the result is approximately 27.47 kW. Therefore Option B is correct.
వివరణ:
Question 17
ప్రశ్న 17
Which expression correctly defines the overall efficiency of a centrifugal pump?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A pump receives mechanical power at its shaft. After mechanical and hydraulic losses, only part of this power appears as useful hydraulic energy in the delivered liquid. The useful output is rho g Q Hm. Overall efficiency is therefore useful water power divided by shaft input power. Hence Option A is correct.
వివరణ:
Question 18
ప్రశ్న 18
A pump supplies 27.468 kW of useful hydraulic power with an overall efficiency of 75%. What shaft input power is required?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Overall efficiency is useful hydraulic power divided by shaft input power. Therefore shaft power equals useful water power divided by overall efficiency. Substitution gives 27.468/0.75 kW. The result is 36.624 kW. Therefore Option C is correct.
వివరణ:
Question 19
ప్రశ్న 19
Neglecting leakage and defining mechanical efficiency as power imparted by the impeller to the liquid divided by shaft input power, which efficiency relationship is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Mechanical efficiency accounts for mechanical losses between the shaft and the energy transferred by the impeller. Manometric efficiency accounts for the loss between Euler energy imparted by the impeller and useful manometric head. Multiplying the two ratios cancels the intermediate impeller power. The remaining ratio is useful hydraulic power divided by shaft input power. Therefore eta_o = eta_m eta_man under the stated assumptions and Option A is correct.
వివరణ:
Question 20
ప్రశ్న 20
A centrifugal pump has a manometric efficiency of 80% and a mechanical efficiency of 90%. Neglect leakage. What is the overall efficiency?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Under the stated assumptions, overall efficiency equals mechanical efficiency multiplied by manometric efficiency. Thus eta_o = 0.90 × 0.80. This gives 0.72. Expressed as a percentage, the overall efficiency is 72 percent. Therefore Option B is correct.
వివరణ:
Question 21
ప్రశ్న 21
At centrifugal-pump impeller inlet, the liquid enters without whirl with flow velocity Vf1 = 5 m/s, while the blade speed is U1 = 10 m/s. If the inlet blade angle beta1 is measured from the tangent in the backward direction, what angle gives shockless entry?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
With zero inlet whirl, the absolute inlet velocity consists only of the flow component. The relative velocity therefore has a backward tangential component of magnitude U1 and a flow component Vf1. For shockless entry, the blade must align with this relative velocity. Hence tan(beta1) = Vf1/U1 = 5/10 = 0.5. This gives beta1 = approximately 26.6 degrees, so Option B is correct.
వివరణ:
Question 22
ప్రశ్న 22
A centrifugal-pump impeller must pass Q = 0.080 m³/s at outlet diameter D2 = 0.40 m with outlet flow velocity Vf2 = 2.0 m/s. Neglect blade thickness. What outlet width b2 is required approximately?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
At the impeller outlet, Q = pi D2 b2 Vf2 when blockage is neglected. Therefore b2 = Q/(pi D2 Vf2). Substitution gives 0.080/(pi × 0.40 × 2.0). This equals approximately 0.03183 m. Thus the required width is about 31.8 mm and Option B is correct.
వివరణ:
Question 23
ప్రశ్న 23
An ideal centrifugal pump has radial entry with zero inlet whirl and radial outlet blades. The impeller outer diameter is 0.50 m and speed is 900 rpm. Neglect slip. What is the Euler head approximately? Take g = 9.81 m/s².
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
For radial outlet blades, beta2 is 90 degrees and the ideal outlet whirl velocity equals U2. The peripheral speed is U2 = pi × 0.50 × 900/60 = approximately 23.56 m/s. With radial entry, Vw1 is zero, so the Euler head is U2²/g. Substitution gives approximately 56.59 m. Therefore Option C is correct.
వివరణ:
Question 24
ప్రశ్న 24
What is the principal effect of slip caused by a finite number of impeller blades in a centrifugal pump?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
An ideal velocity triangle assumes that the fluid follows the impeller blade direction perfectly. With a finite number of blades, the flow does not exactly follow that ideal geometry. The resulting slip generally reduces the actual whirl component at impeller outlet. Because Euler head depends directly on U2Vw2, the energy transfer and theoretical head are reduced. Therefore Option A is correct.
వివరణ:
Question 25
ప్రశ్న 25
Consider the following statements about a centrifugal pump: I. At normal design entry without prewhirl, Vw1 is approximately zero. II. For backward-curved outlet blades under ideal guidance, Vw2 = U2 - Vf2 cot(beta2). III. Manometric head is normally smaller than Euler head because of hydraulic losses. IV. Overall efficiency is useful hydraulic output power divided by shaft input power. Which option is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Statement I is the standard design assumption for a centrifugal pump without deliberate inlet prewhirl. Statement II follows from the outlet velocity triangle for backward-curved blades under the stated angle convention. Statement III correctly recognizes that actual manometric head is reduced below ideal Euler head by hydraulic losses. Statement IV is the correct definition of overall pump efficiency. Therefore all four statements are correct and Option D is the valid answer.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: A. The impeller transfers mechanical energy to the liquid, increasing its angular momentum and total head సమాధానం: A.
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Question 2 ప్రశ్న 2Answer: A. The impeller adds energy to the liquid, while the casing or diffuser collects the flow and converts part of its velocity head into pressure head సమాధానం: A.
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Question 3 ప్రశ్న 3Answer: A. To fill the pump casing and suction line with liquid and remove air so that the rotating impeller can establish the required suction and pressure rise సమాధానం: A.
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Question 4 ప్రశ్న 4Answer: A. Vw1 is approximately zero because the liquid enters the impeller substantially radially or axially without appreciable prewhirl సమాధానం: A.
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Question 5 ప్రశ్న 5Answer: A. HE = (U2Vw2 - U1Vw1)/g సమాధానం: A.
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Question 6 ప్రశ్న 6Answer: A. Vw2 = U2 - Vf2 cot(beta2) సమాధానం: A.
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Question 7 ప్రశ్న 7Answer: B. 25.13 m/s సమాధానం: B.
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Question 8 ప్రశ్న 8Answer: B. 1.592 m/s సమాధానం: B.
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Question 9 ప్రశ్న 9Answer: B. 22.38 m/s సమాధానం: B.
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Question 10 ప్రశ్న 10Answer: C. 57.33 m సమాధానం: C.
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Question 11 ప్రశ్న 11Answer: A. The increase in total head of the liquid between the pump suction and delivery sections సమాధానం: A.
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Question 12 ప్రశ్న 12Answer: C. 32.82 m సమాధానం: C.
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Question 13 ప్రశ్న 13Answer: A. eta_man = Hm/HE = gHm/(U2Vw2 - U1Vw1) సమాధానం: A.
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Question 14 ప్రశ్న 14Answer: C. 87.2% సమాధానం: C.
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Question 15 ప్రశ్న 15Answer: A. Pwater = rho g Q Hm సమాధానం: A.
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Question 16 ప్రశ్న 16Answer: B. 27.47 kW సమాధానం: B.
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Question 17 ప్రశ్న 17Answer: A. eta_o = useful hydraulic output power/shaft input power సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: C. 36.62 kW సమాధానం: C.
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Question 19 ప్రశ్న 19Answer: A. eta_o = eta_m eta_man సమాధానం: A.
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Question 20 ప్రశ్న 20Answer: B. 72% సమాధానం: B.
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Question 21 ప్రశ్న 21Answer: B. 26.6 degrees సమాధానం: B.
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Question 22 ప్రశ్న 22Answer: B. 31.8 mm సమాధానం: B.
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Question 23 ప్రశ్న 23Answer: C. 56.6 m సమాధానం: C.
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Question 24 ప్రశ్న 24Answer: A. The actual outlet whirl velocity is generally smaller than the ideal infinite-blade value, reducing the Euler head developed సమాధానం: A.
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Question 25 ప్రశ్న 25Answer: D. I, II, III and IV సమాధానం: D.