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Question 1
ప్రశ్న 1
What is the conventional physical interpretation of turbine specific speed?
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Explanation:
Turbine specific speed is a characteristic parameter associated with a homologous family of turbines. Conventionally, it is interpreted as the speed of a geometrically similar turbine that would develop unit power under unit head. It therefore provides information about runner shape and the operating range for which a turbine family is suitable. It is not the actual maximum or runaway speed of the installed turbine. Therefore Option B is correct.
వివరణ:
Question 2
ప్రశ్న 2
Under the commonly used metric convention with turbine speed N in rpm, turbine output power P in kW and net head H in metres, which expression defines turbine specific speed?
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Explanation:
The conventional turbine specific-speed expression uses rotational speed, turbine output power and net head. Under the stated metric convention it is written as Ns = N sqrt(P)/H^(5/4). The power term distinguishes the conventional turbine formula from the conventional pump formula. Specific-speed values should always be compared using the same system of units and convention. Therefore Option A is correct.
వివరణ:
Question 3
ప్రశ్న 3
A turbine operates at 300 rpm, produces 5000 kW and works under a net head of 100 m. Using Ns = N sqrt(P)/H^(5/4), what is its turbine specific speed approximately?
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Explanation:
The square root of 5000 is approximately 70.711. The quantity 100^(5/4) is approximately 316.228. Hence Ns = 300 × 70.711/316.228. This gives approximately 67.08. Therefore the closest answer is 67.1 and Option C is correct.
వివరణ:
Question 4
ప్రశ్న 4
Which statement correctly distinguishes conventional turbine specific speed from conventional pump specific speed?
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Explanation:
For a turbine, the usual practical specific-speed expression is formed from N, output power P and head H. For a pump, the corresponding conventional quantity is formed from N, discharge Q and head H. The two parameters serve analogous similarity and selection purposes but are not the same algebraic quantity. Their conventional dimensional forms are also different. Therefore Option A is correct.
వివరణ:
Question 5
ప్రశ్న 5
Which statement about the conventional turbine specific speed Ns = N sqrt(P)/H^(5/4) is correct?
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Explanation:
The commonly quoted practical turbine specific speed is not inherently dimensionless. Its numerical value therefore depends on the particular unit convention used for speed, power and head. Dimensionless forms of specific speed can also be defined from similarity analysis. These dimensionless parameters should not be confused with the traditional engineering Ns value. Therefore Option C is correct.
వివరణ:
Question 6
ప్రశ్న 6
Which ordering generally represents increasing turbine specific speed when all values are expressed using the same convention?
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Explanation:
Pelton turbines are associated mainly with relatively high heads and smaller discharges and consequently have relatively low specific speeds. Francis turbines occupy an intermediate range. Kaplan and propeller turbines handle comparatively large discharges under lower heads and have relatively high specific speeds. The exact numerical ranges depend on the specific-speed convention and turbine details. Therefore Option B is correct.
వివరణ:
Question 7
ప్రశ్న 7
A hydroelectric site has a very high available head and comparatively small discharge. Which turbine type is generally the most appropriate starting choice?
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Explanation:
A high-head site contains substantial energy per unit weight of water but may have a comparatively modest discharge. Pelton turbines are impulse machines particularly suited to such conditions. Their nozzles efficiently convert the available pressure head into high-speed jets. Kaplan and propeller turbines are normally associated with much lower heads and larger flows. Therefore Option A is correct.
వివరణ:
Question 8
ప్రశ్న 8
A hydroelectric site has a low head but a very large available discharge. Which turbine is generally most suitable?
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Explanation:
Low-head installations require large quantities of water to produce substantial power. Kaplan turbines are axial-flow reaction turbines capable of handling large discharges efficiently. They also have relatively high specific speeds compared with Francis and Pelton turbines. Their adjustable runner blades provide useful part-load performance. Therefore Option B is correct.
వివరణ:
Question 9
ప్రశ్న 9
For an installation with an intermediate head and moderate-to-large discharge, which turbine is commonly selected when its specific-speed range is appropriate?
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Explanation:
Francis turbines occupy a broad intermediate region between high-head Pelton turbines and low-head Kaplan turbines. They are mixed-flow reaction machines and can accommodate substantial discharge. Actual selection depends on head, power, rotational speed, cavitation requirements and efficiency characteristics. Specific speed provides a useful initial selection parameter. Therefore Option A is correct.
వివరణ:
Question 10
ప్రశ్న 10
As the design specific speed of reaction turbines increases, which general runner-design trend is expected?
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Explanation:
Higher turbine specific speed is generally associated with lower head and relatively greater discharge. To accommodate the larger flow efficiently, reaction-turbine runner geometry progressively favors more axial flow. Francis designs therefore evolve toward more axial-flow configurations as specific speed rises. The Kaplan turbine represents the high-specific-speed axial-flow reaction-turbine class. Therefore Option A is correct.
వివరణ:
Question 11
ప్రశ్న 11
Which set gives the conventional unit quantities for a given hydraulic turbine operating under head H at homologous conditions?
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Explanation:
For corresponding operation of the same turbine, speed varies approximately as the square root of head. Discharge also varies as the square root of head. Power varies as head raised to the three-halves power when efficiency remains comparable. Dividing the actual quantities by these head dependencies reduces them to unit-head quantities. Therefore Option A is correct.
వివరణ:
Question 12
ప్రశ్న 12
A turbine rotates at 400 rpm under a head of 64 m. What is its unit speed Nu = N/sqrt(H)?
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Explanation:
Unit speed is Nu = N/sqrt(H). The square root of 64 is 8. Therefore Nu = 400/8. This gives 50 rpm under the conventional unit-head representation. Hence Option B is correct.
వివరణ:
Question 13
ప్రశ్న 13
A turbine passes Q = 8.0 m³/s under a head of 64 m. What is the unit discharge Qu = Q/sqrt(H)?
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Explanation:
Unit discharge is defined as Qu = Q/sqrt(H). For H = 64 m, sqrt(H) equals 8. Dividing the actual discharge of 8.0 m³/s by 8 gives 1.00 m³/s. This is the discharge corresponding to unit head for the assumed similar operating condition. Therefore Option B is correct.
వివరణ:
Question 14
ప్రశ్న 14
A turbine develops 4096 kW under a head of 64 m. What is its unit power Pu = P/H^(3/2)?
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Explanation:
Unit power is defined as Pu = P/H^(3/2). Since 64^(3/2) equals 64 × 8 = 512, the denominator is 512. Dividing 4096 kW by 512 gives 8 kW. This is the corresponding power reduced to unit head under similar conditions. Therefore Option B is correct.
వివరణ:
Question 15
ప్రశ్న 15
The same turbine operates at corresponding similar conditions with approximately unchanged efficiency. At H1 = 100 m it runs at 500 rpm, passes 10 m³/s and develops 5.0 MW. What are N2, Q2 and P2 when H2 = 64 m?
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Explanation:
For homologous operation of the same turbine, N and Q vary as sqrt(H), while P varies as H^(3/2). The head ratio is 64/100 = 0.64 and its square root is 0.8. Therefore N2 = 500 × 0.8 = 400 rpm and Q2 = 10 × 0.8 = 8.0 m³/s. The power ratio is 0.64^(3/2) = 0.512, giving P2 = 5.0 × 0.512 = 2.56 MW. Hence Option A is correct.
వివరణ:
Question 16
ప్రశ్న 16
Which statement correctly describes the usual main characteristic or constant-head test of a hydraulic turbine?
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Explanation:
Main characteristic curves are also commonly called constant-head characteristic curves. For a particular test, head and gate opening are maintained essentially constant. The turbine speed is changed by varying the applied load. Corresponding discharge, power and efficiency values are then obtained and may be expressed using unit quantities. Therefore Option A is correct.
వివరణ:
Question 17
ప్రశ్న 17
Operating characteristic curves of a hydraulic turbine are commonly referred to as which type of curves?
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Explanation:
A turbine connected to an electrical generator is normally required to operate at nearly constant synchronous speed. Its practical operating behaviour is therefore commonly studied at constant speed while load and flow conditions change. Such performance plots are known as operating characteristic curves. Gate opening is adjusted as required to regulate flow and output. Therefore Option A is correct.
వివరణ:
Question 18
ప్రశ్న 18
What is the principal purpose of hydraulic-turbine characteristic curves?
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Explanation:
A hydraulic turbine rarely operates permanently at one exact combination of head, load and gate opening. Characteristic curves show how performance variables change as operating conditions vary. They are used to identify efficient regions, part-load behaviour and suitable operating limits. Model-test data can also be expressed through unit or dimensionless quantities to predict prototype performance. Therefore Option A is correct.
వివరణ:
Question 19
ప్రశ్న 19
What is the basic objective of governing a hydraulic turbine connected to an electrical generator?
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Explanation:
Generator frequency is directly related to rotational speed. When electrical load changes, the resisting torque on the turbine-generator shaft also changes. Without corrective action the rotational speed would therefore vary. A governor adjusts the water-energy input so that driving torque again balances the required load. Hence the basic objective is speed regulation and Option A is correct.
వివరణ:
Question 20
ప్రశ్న 20
Which statement correctly describes governing of Francis and Kaplan turbines?
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Explanation:
Reaction turbines regulate water flow using adjustable guide vanes or wicket gates. Francis governing primarily changes the guide-vane opening to match flow to the load. Kaplan turbines add adjustable runner-blade pitch to the guide-vane regulation. Coordinated adjustment improves efficiency over a wider range of discharge and load. Therefore Option A is correct.
వివరణ:
Question 21
ప్రశ్న 21
What is cavitation in a hydraulic turbine?
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Explanation:
Cavitation begins when the local absolute pressure falls sufficiently close to the vapour pressure of water at the operating temperature. Vapour-filled cavities or bubbles then form in the liquid. As these cavities move into regions of higher pressure they can collapse violently. Repeated collapse can produce noise, vibration, surface pitting and performance deterioration. Therefore Option A is correct.
వివరణ:
Question 22
ప్రశ్న 22
In a reaction turbine, where is cavitation commonly of particular concern because pressure may reach its minimum value?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
The pressure in a reaction turbine generally decreases through part of the runner. A particularly low-pressure region commonly occurs near the runner outlet and entrance to the draft tube. This location is therefore highly important in cavitation design. The absolute pressure must remain sufficiently above the vapour pressure under operating conditions. Therefore Option A is correct.
వివరణ:
Question 23
ప్రశ్న 23
Which statement best describes the hydraulic function of a draft tube in a reaction turbine?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
A draft tube connects the reaction-turbine runner outlet to the tailrace. Its increasing area reduces the mean flow velocity and converts part of the exit kinetic energy into pressure head. It also allows the runner to be positioned some distance above the tail-water surface without losing the corresponding elevation head. However, excessive setting height can lower runner-exit pressure too much and increase cavitation risk. Therefore Option A is correct.
వివరణ:
Question 24
ప్రశ్న 24
Which statement about Thoma's cavitation parameter and reaction-turbine setting is correct?
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Explanation:
Thoma's cavitation parameter provides a nondimensional measure of the available cavitation margin relative to turbine head. For satisfactory operation, the available value should exceed the critical cavitation parameter appropriate to the turbine. Raising a reaction turbine farther above the tail water reduces the available pressure margin and generally increases cavitation risk. Critical cavitation requirements tend to become more demanding as turbine specific speed increases. Therefore higher-specific-speed reaction turbines generally require careful and relatively low setting, making Option A correct.
వివరణ:
Question 25
ప్రశ్న 25
For a simplified reaction-turbine cavitation calculation, let the available Thoma parameter be sigma = (Ha - Hv - Hs)/H, where Ha = 10.3 m of water, Hv = 0.3 m, turbine setting Hs = 3.0 m above tail water and turbine head H = 50 m. If the critical value for the turbine is sigma_c = 0.12, which result is correct?
Select an option first. || ముందుగా ఒక సమాధానాన్ని ఎంచుకోండి.
Explanation:
Using the stated simplified expression, the available head above vapour pressure after allowing for setting is 10.3 - 0.3 - 3.0 = 7.0 m. Dividing by the turbine head of 50 m gives sigma = 7/50 = 0.14. The given critical cavitation parameter is 0.12. Since the available value 0.14 exceeds the critical value, the stated cavitation criterion is satisfied. Therefore Option A is correct.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: B. The speed of a geometrically similar turbine that would develop unit power under unit head సమాధానం: B.
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Question 2 ప్రశ్న 2Answer: A. Ns = N sqrt(P)/H^(5/4) సమాధానం: A.
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Question 3 ప్రశ్న 3Answer: C. 67.1 సమాధానం: C.
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Question 4 ప్రశ్న 4Answer: A. Turbine specific speed is based on N, P and H, whereas pump specific speed is commonly based on N, Q and H సమాధానం: A.
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Question 5 ప్రశ్న 5Answer: C. It is a dimensional conventional parameter, distinct from a properly defined dimensionless specific speed సమాధానం: C.
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Question 6 ప్రశ్న 6Answer: B. Pelton, Francis, Kaplan సమాధానం: B.
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Question 7 ప్రశ్న 7Answer: A. Pelton turbine సమాధానం: A.
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Question 8 ప్రశ్న 8Answer: B. Kaplan turbine సమాధానం: B.
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Question 9 ప్రశ్న 9Answer: A. Francis turbine సమాధానం: A.
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Question 10 ప్రశ్న 10Answer: A. The flow tends to become more axial and the runner accommodates greater discharge for a given general power scale సమాధానం: A.
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Question 11 ప్రశ్న 11Answer: A. Nu = N/sqrt(H), Qu = Q/sqrt(H), Pu = P/H^(3/2) సమాధానం: A.
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Question 12 ప్రశ్న 12Answer: B. 50 rpm సమాధానం: B.
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Question 13 ప్రశ్న 13Answer: B. 1.00 m³/s సమాధానం: B.
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Question 14 ప్రశ్న 14Answer: B. 8 kW సమాధానం: B.
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Question 15 ప్రశ్న 15Answer: A. 400 rpm, 8.0 m³/s and 2.56 MW సమాధానం: A.
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Question 16 ప్రశ్న 16Answer: A. Head and gate opening are held constant while speed is varied by changing the load, and corresponding discharge, power and efficiency are determined సమాధానం: A.
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Question 17 ప్రశ్న 17Answer: A. Constant-speed curves సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: A. To predict turbine behaviour, efficiency, discharge and power over operating conditions different from a single design point సమాధానం: A.
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Question 19 ప్రశ్న 19Answer: A. To maintain approximately constant rotational speed as electrical load changes by controlling the water-energy input సమాధానం: A.
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Question 20 ప్రశ్న 20Answer: A. Francis turbines are commonly governed by adjusting guide-vane opening, while Kaplan turbines can coordinate guide-vane opening with runner-blade pitch సమాధానం: A.
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Question 21 ప్రశ్న 21Answer: A. Formation of vapour cavities when local absolute pressure falls to the liquid vapour pressure, followed by collapse when the cavities reach higher-pressure regions సమాధానం: A.
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Question 22 ప్రశ్న 22Answer: A. Near the runner outlet and draft-tube inlet సమాధానం: A.
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Question 23 ప్రశ్న 23Answer: A. It acts as a diffuser that recovers part of the runner-exit kinetic energy and allows the runner to be set above tail-water level within cavitation limits సమాధానం: A.
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Question 24 ప్రశ్న 24Answer: A. Cavitation is avoided when the available Thoma parameter exceeds the critical value for the turbine, and high-specific-speed turbines generally require more conservative setting nearer the tail water సమాధానం: A.
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Question 25 ప్రశ్న 25Answer: A. sigma = 0.14, and the stated criterion indicates an adequate cavitation margin because sigma > sigma_c సమాధానం: A.