Thread Content
III. Multiple-choice questions: 1. The internal energy of a working substance depends on (C), that is, it depends on its state. (A) Temperature ； (B) Specific volume ； (C) Temperature and specific volume ； (D) Pressure. 2. The condensation process of steam inside the condenser can be regarded as (C) (A) an isochoric process ； (B) Isothermal process ； (C)) Isobaric process ； (D) Adiabatic process. 3. The necessary condition for improved thermal economy through intermediate reheat is (A) (A) the thermal efficiency of the reheat additional cycle being greater than that of the basic cycle ； (B) The thermal efficiency of the reheat additional cycle is lower than that of the basic cycle ； (C) The basic cycle thermal efficiency is greater than 40% ； (D) The thermal efficiency of the reheat additional cycle must not be too low. 4. After adopting the regenerative cycle, compared with a pure condensing cycle with the same initial parameters and power, its (B). (A) Reduced fuel consumption ； (B) Reduced heat consumption ； (C) The total enthalpy drop for work done increases ； (D) The coefficient of insufficient work increases. 5. The radiant power of an absolute black body is proportional to the (C) square of its absolute temperature. (A) Quadratic ； (B) Three times ； (C) Four times ； (D) Five times. 6. The applicable condition for the fluid energy equation is (A) (A) the fluid is in steady flow ； (B) The flow is compressible ； (C) The flow is unsteady ； (D) Neither of the two sections of the fluid chosen is in a gradually varying flow. 7. The digital electro-hydraulic control system is used as the (A) part of the coordinated control system. (A) Turbine actuator ； (B) Boiler actuator ； (C) Generator actuator ； (D) Coordinate instruction executor. 8. In the impulse stage of a steam turbine, the conversion of the thermal energy of steam into kinetic energy takes place in (A). (A) Nozzle ； (B) Moving blade ； (C) Stator blades ； (D) Cylinder. 9. The main characteristic of forced vibration is (A). A. The main frequency is equal to the rotor’s speed. B. The main frequency is equal to the critical speed. C. The main frequency is independent of the operating speed. D. The main frequency is independent of the critical speed. 10. During the adiabatic flow of steam with friction, its entropy is (A). (A) Increased ； (B) Reduced ； (C) Unchanged ； (D) All are possible. 11. The parameter tuning of automatic control systems generally uses two methods: (D). A. Computational method, trial-and-error method ； B. Trial and error method, engineering tuning method ； C. Limit sensitivity method, response curve method ； D. Calculation method, engineering tuning method. 12. To ensure the stability of the unit’s control system, the rate of change in the turbine’s speed should generally be set at (B) to be appropriate. A、1% – 2% ； B, 3% ?-6% ； C, 6% – 9% ； D, 9% – 12%. 13. When the unit loses load, the thermal stress generated on the surface of the turbine rotor is (C) stress. A. Tensile stress ； B. Alternating stress ； C. Compressive stress ； D. No stress is generated. 14. Compared with operation at constant pressure, the thermal efficiency of large units operating at variable pressure is lower at low loads (B). A、Lower ； B, Higher ； C. Equal ； D. Very poor. 15. The self-excited oscillation of a steam turbine generator set is (A). A. Underdamped oscillation ； B. Damped oscillation ； C. Infinite-damping oscillation ； D. No damped oscillations occur. 16. The differential expansion protection during turbine startup should be activated at (B). A、After full speed ； B、Before startup ； C. After being integrated into the power grid ； D. After startup. 17. Which of the following pumps has the highest specific speed (C)? A. Peristaltic pump ； B、Feed water pump ； C. Circulation water pump ； D. Condensate pump. 18. The relationship between the turbine speed and power under stable conditions is referred to as the (A) of the control system. A. Static characteristics ； B. Dynamic characteristics ； C. Dynamic and static characteristics ； D. Speed characteristics. 19. During the hot start of the turbine, the continuous turning of the rotor before starting up must last for no less than (B). A、6h ； B, 4h ； C、 ； 2h D, 1h. 20. At startup, when the rotor is below the first-order critical speed and the vibration level of the turbine bearings reaches (D), the machine must be stopped by shutting down the brakes. A、0.02mm ； B, 0.10mm ； C、0.05mm ； D, 0.04mm. 21. During the unit’s vacuum tightness test, the average rate of vacuum decline should not exceed (A). A、400Pa/min ； B, 300 Pa/min ； C, 350 Pa/min ； D, 500 Pa/min. 22. In power plants, the phase sequence of three-phase busbars is indicated by fixed colors, with red, green, and yellow being used to represent phase (A) respectively. A, C, B, A ； B, B, C, A, ； C, A, C, B ； D, A, B, C. 23. The basis for determining the state of fluid motion is (A). A. Reynolds number ； B. Moditu ； C. Nilenraztu ； D. Flow rate. 24. The reason why frequent start-stop of the unit increases wear and tear is (D). A. The temperature difference between the upper and lower cylinders may cause friction between the moving and stationary parts ； B、Excessive differential expansion ； C. Excessive alternating stress on the turbine rotor ； D. Fatigue damage of metal materials caused by thermal stress. 25. When it is necessary to follow central dispatch instructions to participate in grid frequency regulation, the unit should adopt (D) control mode. A. Machine and furnace ； B、Furnace follower ； C、Manual operation of the turbine and boiler ； D. Turbine and boiler coordination. 26. The subcooling degree of the condenser in large-scale units is generally (A). A、0.51℃ ； B, 2.3℃ ； C, 3.5℃ ； D. 4.0°C. 27. The purpose of using an inducer wheel in a water pump is (B). A. Improve efficiency ； B. Prevent cavitation ； C. Preventing noise ； D. Prevent vibration. 28. The Regulations on Technical Management in the Electric Power Industry require that turbines be equipped with the following protection devices: overspeed protection, (B), low lubricating oil pressure protection, and low vacuum protection. A. Differential expansion protection B. Axial displacement protection C. High vibration protection D. Water ingress protection. 29. It is most advantageous to maintain the condenser vacuum at (C) during the operation of the turbine. A. Operate under high vacuum ； B、Operate under low vacuum ； C、Operating in an economic vacuum ； D: Operate above the low vacuum alarm value. 30. Generally, the oil filling test after the maintenance of the turbine speed control system should be carried out after (D). A. Before the unit is connected to the grid ； B. After the unit is connected to the grid ； C. Before the overspeed test ； D. After the overspeed test. 31. The following statement regarding hot start is incorrect: （２） (1) During a hot start, the metal temperature of the cylinder is high, and there is a cooling process after steam enters the cylinder. (2) Warm-up is not required even for hot start ； (3) For hot start, the shaft seal should be activated first, followed by vacuum extraction ； (4) For hot start, the temperature is generally required to be 50–100°C higher than the metal temperature. 32. Which of the following statements about low-pressure heaters is incorrect? （１） (1) The flow directions of steam and feedwater are not always in counterflow ； (2) The heating surface of the heater is designed in two sections: a steam condensation section and a hydrophobic cooling section ； (3) The hydrophobic inlet end is sealed using a hydrophobic device; the hydrophobic valve is adjusted appropriately to maintain an appropriate level of water to achieve sealing ； (4) The heater is equipped with a stainless steel anti-impact plate to prevent the water and steam inside the housing from directly hitting the tubes. 33. Which of the following statements regarding the partial pressure of air in the condenser is incorrect? （２） （1) The partial pressure of air in the condenser is not constant ； (2) The partial pressure of air in the condenser decreases gradually from outside the tube bundle to the air cooling zone ； (3) The partial pressure of air and the partial pressure of steam in the air cooling zone are on the same order of magnitude ； (4) The partial pressure of air at the condenser vacuum measurement point is extremely small compared to the partial pressure of steam, and can be considered negligible. 34. The starting method that can be used for modern large-scale steam turbines is (３) (1) Starting at rated parameters ； (2) Partial-week steam injection start-up ； (3) Slip parameter pressure method ； (4) Slip-parameter vacuum method for starting up. 35. Scaling inside the copper tubes of a turbine condenser can cause (4) (1) an increase in heat transfer and a rise in tube wall temperature ； (2) Heat transfer is reduced, and the tube wall temperature decreases ； (3) Enhanced heat transfer, reduced wall temperature ； (4) Heat transfer decreases, and the tube wall temperature rises. 36. Which of the following is NOT a characteristic of reaction turbines? （２） （1) Reaction turbines have a large axial clearance ； (2) Reaction turbines have relatively low axial thrust ； (3) Reaction turbines do not have impellers ； (4) Reaction turbines do not have partitions. 37. Which of the following statements regarding the heat release coefficient is incorrect? (2) (1) The heat release coefficient for steam condensation is much larger than that for convection ； (2) The higher the pressure of saturated steam, the lower the heat release coefficient ； (3) The heat release coefficient of wet steam is much larger than that of saturated steam ； (4) The heat release coefficient due to the condensation of steam is greater than that due to the convection of moist steam. 38. In modern large-scale power units, which of the following situations cannot cause a drop in the condenser vacuum? （３） （1) Damage to the water seal of the condensate pump ； (2) Low water level in the condenser make-up water tank ； (3) Leakage in the steam pipes of #7 and #8 low-temperature heaters ； (4) Siphon failure of the condenser return water pipe. 39. For a steam turbine with nozzle control, the most critical operating condition for the governing stage occurs when (1) The first control valve is fully open, while the second control valve has not yet been opened ； (2) Condition when the control valve is fully open ； (3) When the first control valve has just been opened and the other valves have not yet been opened ； (4) When the first and second control valves are fully open and the third control valve has not yet been opened. 40. If, during the operation of the turbine, an increase in the current of the condensate pump, a decrease in the pressure of the condensate main, and a decrease in the condensate flow rate are observed, it should be determined as （４） （1) Leakage in the condensate main ； (2) Clogging of the inlet filter for the condensate pump ； (3) Air leakage in the condensate pump ； (4) Reverse rotation of the standby condensate pump. 41. The impeller friction loss is related to ____ D. A: Partial admission ； B: Residual velocity ； C: Leaf height ； D: Gap between the impeller and the baffle. 42. The correct statement is __ _D ___. A: Utilizing residual speed reduces the optimal speed ratio ； B: Utilizing residual speed reduces maximum efficiency ； C: Utilization of residual velocity deteriorates the off-design performance of the stage ； D: Utilizing residual speed optimizes the stage efficiency at the optimal speed ratio. The correct expression for the ideal energy at level 43 is ____ C _____. A: E0=△ht; B: E0=△ht*; C: E0=μ0c02/2+△ht-μ1c22/2; D: E0=μ1c22/2+△ht. 44. The part of the last-stage blades of a steam turbine that is most susceptible to erosion by moisture is ____A_____. A: Back arc on the steam inlet side at the blade tip; B: Inner arc on the steam outlet side at the blade tip; C: Back arc on the steam outlet side at the blade tip; D: Back arc on the steam inlet side at the blade root. 45. The maximum axial thrust in a back-pressure steam turbine generally occurs when _____ B ______. A: No load ； B: Some intermediate load ； C: Economic load ； D: Maximum load. 46. The stage in which the enthalpy drop changes while the reaction degree remains essentially constant under varying operating conditions is _____ C _____. A: Pure impulse stage; B: Compound speed stage; C: Reaction stage. 47. In a turbine with nozzle control, when each control valve is opened in sequence, the flow rate passing through the nozzle assembly downstream of the first control valve is _ D __. A: It keeps increasing; B: It increases when the first valve opens, and remains constant once it is fully open; C: It increases when the first valve opens, remains constant after full opening, and then increases again. D: It increases when the first valve opens, remains constant after full opening, and then decreases. 48. During the operation of the condenser, the more air that leaks in, then _____ C ______. A: The greater the heat transfer terminal difference, the smaller the supercooling; B: The smaller the heat transfer terminal difference, the greater the supercooling; C: The greater the heat transfer terminal difference, the greater the supercooling. 49. Based on the characteristics of the condenser under varying operating conditions, it can be seen that when the exhaust steam volume decreases, the vacuum will _____A______. A: Increase; B: Decrease; C: Unchanged. 50. The main cause of energy loss when a fluid flows is ____C_____. A The compressibility of the fluid B The expansibility of the fluid C The viscosity of the fluid 51. The basis for selecting an appropriate degree of steam injection is ____ A _____ . A: The sum of blade height loss and partial steam admission loss is minimized; B: The sum of steam leakage loss and partial steam admission loss is minimized; C: The sum of blower loss and steam rejection loss is minimized. 52. The indicator used to measure the operational efficiency of a steam turbine generator set is ____ B ____. A: Absolute electrical efficiency ηa,el; B: Relative electrical efficiency ηr,el; C: Relative internal efficiency ηri; D: Cycle thermal efficiency ηt. 53. Among the following losses, those that are intra-stage losses are ____ C ____. A: Steam leakage loss from the shaft seal; B: Throttling loss in the steam inlet mechanism; C: Steam leakage loss from the partition. 54. At the instability speed A, oil film oscillation does not occur. (nc stands for critical speed). A. Greater than the operating speed B. Greater than the first critical speed nc1 C. Greater than nc2 D. Greater than 2 nc1 55. If the overlap between the various control valves of the turbine is too small, it will cause the static characteristic curve of the control system to be B. A. The local speed variation rate is too low. B. The local speed variation rate is too high. C. The upward movement is excessive. D. The upward movement is insufficient. 56. During hot startup, A. A. Supply shaft seal steam first, then evacuate. B. Evacuate first, then supply shaft seal steam. C. Start the rotation first, then supply shaft seal steam. D. The order of evacuating and supplying shaft seal steam can be determined as convenient. 57. Rotor thermal bending is caused by C. A. The rotor heats up too quickly. B. Uneven heat transfer due to steam flow. C. Temperature difference between the upper and lower cylinders. D. Temperature difference between the inner and outer cylinders. 58. The bearing type most prone to oil film oscillation is B. A. Elliptical pad bearing B. Cylindrical pad bearing C. Three-oil- wedge bearing D. Tilted pad bearing 59. The valve that can reduce the oscillation of the control system when it is unloaded is A. A. Cone valve B. Ball valve C. Valve with pre-actuation valve D. Steam spring valve 60. The feed water pump increases pressure by compression; it can be considered as ____B____. A Isothermal process B Adiabatic process C Isobaric process 61. In the wet steam region of the enthalpy-entropy diagram, isobaric lines and isothermal lines ( ) A. Intersect B. Are perpendicular to each other C. Are two parallel straight lines D. Overlap. Answer: D, Overlap. 62. Heaters can be classified into different types based on their working principles: ( ). A. Surface type, mixed type ； B. Heaters, deaerators ； C. High-pressure heater, low-pressure heater ； D. Coiled tube type, horizontal ； Answer: A, surface type, mixed type. 63. The part of a centrifugal pump that is most susceptible to cavitation damage is ( ). A. Impeller or blade inlet ； B. Impeller or blade outlet ； C. Hub or blade exit ； D. Outer edge of the impeller. Answer: B, the outlet of the impeller or blades. 64. In a spray-type deaerator, the purpose of using multiple layers of sieve trays is ( ). A. For the temperature at which various deoxygenated waters are mixed together ； B. Increase the residence time of water in the tower, as well as the heating area and heating intensity ； C. To change the flow direction of the heating steam ； D. Increase flow resistance. Answer: B. Extend the residence time of water in the tower, and increase the heating area and heating intensity. 65. The main production systems in a thermal power plant are ( ). A. Coal conveying system, steam-water system, electrical system B. Steam-water system, combustion system, electrical system C. Coal conveying system, combustion system, steam-water system D. Water supply system, electrical system, coal conveying system Answer: B. Steam-water system, combustion system, electrical system. 66. The normal temperature of the oil outlet from the lubricating oil cooler in a running turbine generator set is (), and adjustments should be made if this value is not within the normal range. A, 35℃ ； B, 40℃ ； C, 45℃ ； D, 49°C. Answer: B, 40℃. 67. It is strictly prohibited to ( ) when the rotor is at rest, in order to prevent thermal bending of the rotor. A. Supply steam to the shaft seal ； B. Create a vacuum ； C. Carry out hydrogen charging and discharging operations on the generator ； D. Put the oil system into service. Answer: A. Supplying steam to the shaft seal. 68. Changes in the vacuum level of the turbine condenser will result in changes in the terminal difference of the condenser; generally, when the vacuum level of the condenser increases, the terminal difference ( ). A. Increase; B. Remain unchanged; C. Decrease; D. Increase first then decrease. Answer: C, decrease. 69. During sliding pressure operation of the deaerator, a sudden decrease in the unit’s load will result in an increase in the oxygen content of the deaerated feed water. A. Increase ； B. Reduce ； C. Fluctuations ； D. Unchanged. Answer: B, decrease. 70. The reason why the exhaust temperature rises when the load on the turbine is too low is ( ). A. Excessively high vacuum. B. Excessively high inlet steam temperature. C. The steam flow rate entering the turbine is too low, insufficient to cool the heat generated by frictional losses. D. Excessively high inlet steam pressure. Answer: C, the steam flow rate entering the turbine is too low, insufficient to cool the heat generated by frictional losses. 71. The reaction degree of the reaction stage (ρ=0.5) under varying turbine operating conditions is ＿＿＿＿＿＿＿＿＿. (C. Basically unchanged. ) A. Increase ； B. Decrease ； C. Basically unchanged. 72. Condensers can be classified into four types based on the direction of exhaust flow, and the type that is most commonly used at present is ＿＿＿＿＿＿＿. (D. Gas flow is lateral. ) A. Downward gas flow type ； B. Upward airflow type ； C. Centripetal flow ； D. Lateral airflow type. 73. Which of the following pumps has a higher specific speed? ＿＿＿＿＿ (B. Circulation pump. ) A. Feed water pump ； B. Circulation pump ； C. Condensate pump. 74. Intermediate reheat steam turbines must use ＿＿＿＿＿＿＿＿. (C. One machine per furnace or one machine with two furnaces unit system. ) A. One machine per furnace unit system ； B. One-machine-two-furnace unit system ； C. Unit system of one machine per furnace or one machine per two furnaces. 75. During startup, shutdown, and operation under varying conditions, in steam turbines, the temperature differences caused by metal components are related to ＿＿＿＿. (C. The heat transfer between steam and metal is proportional. ) A. The thickness of the metal components is proportional ； B. Metal temperature is proportional ； C. The heat transfer between steam and metal is proportional ； D. The metal temperature is inversely proportional. 76. The condensation process of steam in the condenser can be regarded as ＿＿＿＿. (C. Isobaric process. ) A. Isochoric process ； B. Isenthalpic process ； C. Isobaric process ； D. Adiabatic process. 77. Scaling inside the copper tubes of a turbine condenser can cause ＿＿＿＿＿＿＿＿＿＿＿＿. (D. Heat transfer decreases, and the tube wall temperature rises. ) A. Enhanced heat transfer, increased tube wall temperature ； B. Heat transfer is reduced, and the tube wall temperature decreases ； C. Heat transfer is enhanced, and the tube wall temperature decreases ； D. Heat transfer decreases, and the tube wall temperature rises. 78. For the same fluid, the heat transfer coefficient for boiling heat release is ＿＿＿＿ than that for convective heat release in the absence of any phase change. (B. Large. ) A. Small ； B. Large ； C. Equal. 79. The reason for the drop in condensate pump current to zero, the decrease in condensate pressure, the reduction in condensate flow rate, and the rise in the level of water in the condenser is ＿＿＿＿. (C. Power supply to the condensation pump is interrupted. ) A. Condensate pump failure ； B. Vaporization of the condensation pump ； C. Power failure to the condensate pump. 80. A turbine in which the overall direction of steam flow is roughly perpendicular to the axis of rotation is called ＿＿＿＿＿. (B. Radial flow steam turbine. ) A. Axial flow steam turbine ； B. Radial-flow steam turbine ； C. Circulating steam turbine. 81. Given the pressure P and temperature t of a medium, at that temperature when P is less than P_sat, the state of the medium is ＿＿. (D. Superheated steam. ) A. Unsaturated water ； B. Wet steam ； C. Dry steam ； D. Superheated steam. 82. The venturi tube device is used to measure the ＿＿＿＿＿＿ of the fluid in a pipe. (B. Volumetric flow rate. ) A. Pressure ； B. Volumetric flow rate ； C. Resistance. 83. The radiant power of a real object is ＿＿＿＿＿＿ compared to that of an absolute black body at the same temperature. (B. The former is less than the latter. ) A. The former is greater than the latter ； B. The former is smaller than the latter ； C. The two are equal. 84. At the boiling point, gas and liquid exist simultaneously, and the temperature of the gas and the liquid is ＿＿＿＿＿. (A. Equal. ) A. Equal ； B. Not equal ； C. The gas temperature is higher than the liquid temperature. 85. The actual net positive suction head at the pump inlet is called ＿＿＿＿＿＿. (A. NPSH of the unit. ) A. NPSH of the unit ； B. Allowable net positive suction head ； C. Minimum net positive suction head. 86. Which of the following pumps has a higher specific speed? ＿＿＿＿＿ (B. Circulation pump. ) A. Feed water pump ； B. Circulation pump ； C. Condensate pump. 87. When the ideal enthalpy drop of the impulse stage of a turbine (ρ<0.5) decreases, the reaction degree of the stage ____________. (Increase. ) A. Basically unchanged ； B. Decrease ； C. Increase. 88. During the operation of the high-pressure heater, the pressure on the water side is ＿＿＿＿ the pressure on the steam side. To ensure the safe operation of the steam turbine unit, an automatic bypass protection device is installed on the high-pressure water inlet side. (C. Higher than) A. Lower than ； B. equals ； C. Higher. 89. When salt scale forms on the flow passages of the turbine, the axial thrust ＿＿＿＿. (A. Increase. ) A. Increase ； B. Decrease ； C. Basically unchanged. 90. The ratio of the effective total head to the theoretical head is called the ＿＿＿＿＿＿ of a centrifugal pump. (C. Hydraulic efficiency. ) A. Mechanical efficiency ； B. Volume efficiency ； C. Hydraulic efficiency. 91. The pressure relief valve belongs to ＿＿＿＿＿. (C. Safety door. ) A. Shut-off door ； B. Control valve ； C. Safety door. 92. When the load of the steam turbine generator remains constant and the temperature of the circulating water at the inlet stays unchanged, an increase in the circulating water flow rate results in a ＿＿＿＿＿＿ exhaust temperature. (C. Decrease. ) A. Unchanged ； B. Increase ； C. Decrease. 93. When the axial thrust of a condensing steam turbine increases, its thrust bearings ＿＿＿＿＿. (A. The temperature rises as work increases by 100 units. ) A. Increase in the temperature of the working tile ； B. Increase in temperature of non-working tiles ； C. The temperatures of both the working tiles and the non-working tiles increase. 94. During the startup, shutdown, and operation under varying conditions of a steam turbine, the temperature differences caused by metal components and ＿＿＿＿. (C. The heat transfer between steam and metal is proportional. ) A. The thickness of the metal components is proportional ； B. Metal temperature is proportional ； C. The heat transfer between steam and metal is proportional ； D. The metal temperature is inversely proportional. 95. To reduce the deflection of the condenser cooling water tubes and improve the vibration characteristics of the copper tubes during operation, an intermediate support tube sheet is installed between the two tube sheets, so that the middle section of the cooling water tubes is ＿＿＿＿＿ than the ends. (C. Height 5–10 mm. ) A. 5–10 mm lower ； B. 10–20 mm lower ； C. Height: 5–10 mm ； D. Height: 10–20 mm. 96. The pitot tube device is used to measure the ＿＿＿＿＿ of the fluid in a pipeline. (C. Flow rate. ) A. Pressure ； B. Resistance ； C. Flow rate. 97. In turbines with nozzle regulation, the most critical operating condition for the regulating stage occurs at ＿＿＿＿＿. (C. When the 1st control valve is fully open and the 2nd control valve has not yet been opened. ) A. Condition when the control valve is fully open ； B. When the 1st and 2nd control valves are fully open and the 3rd control valve has not yet been opened ； C. When the 1st control valve is fully open and the 2nd control valve has not yet been opened. 98. When boiling, both vapor and liquid are present; the temperature of the vapor and the liquid is __________. (A. Equal. ) A. Equal ； B. Not equal ； C. The gas temperature is higher than the liquid temperature. 99. In a surface-type heat exchanger, when the cold fluid and the hot fluid flow parallel to each other in opposite directions, it is called ＿＿＿＿. (B. Counter-current type. ) A. Hybrid ； B. Counterflow type ； C. Co-current. 100. When the ideal enthalpy drop of the impulse stage of a turbine (ρ<0.5) decreases, the reaction degree of the stage ___________. (c increases. ) A. Basically unchanged ； B. Decrease ； C. Increase. 101. The condensation process of steam inside the condenser can be regarded as (D). A. Isochoric process ； B. Isenthalpic process ； C. Adiabatic process ； D. Isobaric process. 102. The fatigue life of a turbine rotor is usually expressed by (A). A. Number of strain cycles B. Creep limit curve C. Fatigue limit D. Fatigue curve 103. The stress generated on the surface of the rotor’s central hole during the cold start of a steam turbine is (B). A. Compressive stress ； B. Tensile stress ； C. Pull first, then press ； D. Press first, then pull. 104. The connection method between the speed-regulated feedwater pump motor and the main feedwater pump is (C) A. Rigid coupling ； B. Flexible coupling ； C. Hydraulic coupling ； D. Semi-flexible coupling. 105. In the wet steam region of the enthalpy-entropy diagram, the isobaric lines and isothermal lines (D). A. They intersect; B. They are perpendicular to each other; C. They are two parallel lines; D. They coincide. 106. The comprehensive economic indicator for measuring condensing units refers to ( ). A. Fuel consumption rate B. Heat consumption rate C. Electrical efficiency D. Relative electrical efficiency. 107. The main reason for a negative thermal expansion difference during the hot start of a turbine is (B). A. Excessively high steam temperature during startup B. Excessively low main steam temperature during startup C. Excessively long warm-up time D. Excessively short warm-up time 108. During the overspeed test after major repairs, each safety device should be tested (B) times. A. 1 ； B. 2 ； C. 3 ； D. 4. 109. During the startup of a turbine, phenomenon (B) occurs, and the turbine components may experience the greatest thermal shock. A. Convective heat transfer ； B. Beaded condensation heat transfer ； C. Film condensation heat transfer ； D. Radiative heat transfer. 110. When the turbine operates under varying conditions, the (D) load regulation method is used, and the temperature change in the flow-through section of the high-pressure cylinder is the greatest. A. Variable voltage operation ； B. Partial valve fully open for variable voltage operation ； C. Throttling control for constant-pressure operation ； D. Nozzle adjustment for constant pressure operation. 111. The Rankine cycle is composed of (B). A. Two isothermal processes, two adiabatic processes ； B. Two isobaric processes, two adiabatic processes ； C. Two isobaric processes, two isothermal processes, ； D. Two isochoric processes, two isothermal processes. 112. The factor that causes metal fatigue failure is (D). A. Magnitude of alternating stress ； B. Duration of exposure to alternating stress ； C. Number of alternating stress cycles ； D. The magnitude of the alternating stress and the number of cycles. 113. The phenomenon in which metal parts are damaged due to repeated exposure to alternating thermal stresses is called (D). A. Thermal shock ； B. Thermal brittleness ； C. Thermal deformation ； D. Thermal fatigue. 114. The frequency regulation function of the governor for the power grid is ( A ). A. Single-frequency modulation ； B. Secondary frequency modulation ； C. Primary and secondary frequency modulation ； D. Frequency modulation is not possible. 115. The material of valve components is determined by the (B) of the working medium. A. Flow and pressure ； B. Temperature and pressure ； C. Flow and temperature ； D. Temperature and viscosity. 116. During the tightness tests of the main steam valve and the throttle valve, the test steam pressure should not be lower than (D)% of the rated steam pressure. A. 80 ； B. 70 ； C.60 ； D. 50. 117. The stage prone to overload when the condenser vacuum increases is (C). A. Regulation stage ； B. Intermediate level ； C. Final stage ； D. Level 1 118. When the load and main steam parameters of an impulse turbine unit remain unchanged, as the condenser vacuum decreases, the axial thrust (A) increases. A. Increase ； B. Reduce ； C、Unchanged ； D. Uncertain. 119. Adopting the intermediate-pressure cylinder startup method ensures that the high-pressure cylinder has (C) during prolonged idling. A. Higher efficiency B. Larger expansion difference C. Lower temperature level D. Temperature level exceeding the specified limit. 120. Two centrifugal water pumps are operated in series, ( D ). A. The head of the two water pumps should be the same ； B. The head of the two water pumps should be the same, with the total head being the sum of the heads of the two pumps ； C. The head of the two water pumps can be different, but the total head is 1/2 of the sum of the heads of the two pumps ； D. The head of the two water pumps can be different, but the total head is the sum of the heads of the two pumps. 121. To prevent cavitation in the pump, it is necessary that the pump’s net positive suction head hr and the system’s net positive suction head ha satisfy (B). A、hr> ha B、hr< ha C、hr=ha D、hr=ha+0.3 122、When the tightness of the condenser’s vacuum system decreases, the heat transfer temperature difference of the condenser ( C ). A. Unchanged B. Decreased C. Increased D. Uncertain 123. The losses caused by vortices at the base and top of the turbine nozzles and blade rows are referred to as (B). A. Fan loss B. Blade height loss C. Impeller friction loss D. Cascade loss 124. The relative internal efficiency of a steam turbine is (A). A. The ratio of the effective enthalpy drop to the ideal enthalpy drop; B. The ratio of the power at the turbine shaft to the ideal power; C. The ratio of the generator’s output power to the turbine’s ideal power; D. The ratio of the generator’s output power to the power at the turbine shaft. 125. When the operating conditions of a turbine change, if the enthalpy drop per stage increases, then the reaction degree of that stage (B). A. Unchanged B. Decreased C. Increased D. Uncertain 126. Compared with a pure condensing steam turbine, a heat-supply steam turbine has a higher steam consumption rate (C). A. Unchanged B. Decreased C. Increased D. Uncertain 127. In the DEH control system, if the “Speed Input” light is on, it indicates (A). A. The turbine participates in primary frequency regulation of the power grid. B. The turbine participates in secondary frequency regulation of the power grid. C. Maintain a constant speed for the turbine. D. During the acceleration process of the turbine, ensure that its actual speed remains consistent with the set value. 128. To ensure the stability of the unit’s control system, the rate of speed change should generally be set at (B) as appropriate. A、1%–2% B、3%–6% C、10%–15% D、6%–9% 129. When a fluid flows through a throttling device, its flow rate is proportional to the ( C ） generated before and after the throttling device. A. The square of the pressure difference B. The cube of the pressure difference C. The square root of the pressure difference D. The pressure difference 130. When a unit operates in coordinated mode, the turbine (C). A. Adjust only power B. Adjust only pressure C. Adjust power primarily, with pressure as a secondary factor D. Adjust pressure primarily, with power as a secondary factor 131. The process of steam condensing inside the condenser can be regarded as (A). A. Isobaric process B. Adiabatic process C. Isothermal process D. Isochoric process 132. The main characteristic of forced vibration is (A). A. The main frequency is consistent with the rotor’s speed. B. The main frequency is consistent with the critical speed. C. The main frequency has no relation to the operating speed. D. The main frequency is half of the operating speed. 133. (B) is not a characteristic of unit systems. A. Simple system, cost-saving investment ； B. The furnace, machinery, and electrical systems are closely interconnected vertically; their start-up and shutdown processes influence one another and restrict each other ； C. Enables the most economical start-stop with sliding parameters ； D. Strong adaptability to loads. 134. In a thermodynamic cycle, the adiabatic process of the feed water pump can be represented by a single point on the T-S diagram; this is applicable to (B), otherwise the error would be too large. A. High temperature and high pressure B. Low temperature and low pressure C. Ultra-high pressure D. Subcritical 135. When stopping the feed water pump from operating in standby mode, it is necessary to (C). A. Stop the pump first, then close the outlet valve. B. Close the outlet valve first, then stop the pump. C. Close the outlet valve first, then stop the pump and open it again. D. Stop the pump first, then close the outlet valve and open it again. 136. After going through a series of processes, the working substance returns to its initial state; the change in entropy is (C). A. Greater than zero B. Less than zero C. Unchanged D. Uncertain 137. The head of a pressure tube can vary along the flow path (C). A. Only increase B. Only decrease C. May decrease or increase D. Remain unchanged 138. When the pump’s head remains constant, increasing the impeller’s (A) can relatively reduce the wheel diameter. A. Rotational speed B. Flow rate C. Power D. Efficiency 139. In an operating motor, when the voltage decreases, its current ( C ). A. Unchanged B. Decreased C. Increased D. Uncertain 140. For a three-phase asynchronous motor, given that its rated power is 11 KW, rated voltage is 380 V, and rated power factor is 0.8, its rated current is ( A ) A. A、50.3 B、36.2 C、28.9 D、20.9 142、Heaters can be classified into different types based on their working principles: (A). A. Surface type, mixed type ； B. Heaters, deaerators ； C. High-pressure heater, low-pressure heater ； D. Coiled tube type, horizontal ； 143. In a thermal power plant, the turbine is a device that converts (D). A. Thermal energy is converted into kinetic energy ； B. Conversion of thermal energy into electrical energy ； C. Conversion of mechanical energy into electrical energy ； D. Conversion of thermal energy into mechanical energy. 144. The function of the exhaust pump is to remove (D) from the condenser. A. Air, B. Steam, C. Mixture of steam and air ； D. Air and non-condensable gases 145. To prevent vaporization at the lowest point within the pump, the effective NPSH (D) must be greater than the required NPSH. A, equal to ； B, less than ； C, slightly less than ； D. Greater than 146; the normal value for the oil outlet temperature of the lubricating oil cooler in a running steam turbine generator set is (C), and adjustments should be made if this value is different. A, 35℃ ； B, 40℃ ； C, 45℃ ； D, 49°C. 147. It is strictly prohibited to (A) when the rotor is at rest, to prevent thermal bending of the rotor. A. Supply steam to the shaft seal ； B. Create a vacuum ； C. Carry out hydrogen charging and discharging operations on the generator ； D. Put the oil system into service. 148. Changes in the vacuum level of the turbine condenser will result in changes in the terminal difference of the condenser. Generally, when the vacuum level of the condenser increases, the terminal difference (C) decreases. A. Increase; B. Remain unchanged; C. Decrease; D. Increase first then decrease. 149. The power output of a steam turbine is primarily regulated by changing the turbine’s (C). A. Rotational speed ； B. Operation mode ； C、Steam inlet volume ； D. Steam extraction rate. 150. During normal operation of a condensing steam turbine, as the main steam flow increases, its axial thrust (B) . A. Unchanged; B. Increase; C. Decrease; D. Decrease first then increase. 151. To ensure the stability of the unit’s control system, the rate of change in turbine speed should generally be set at (B) as an appropriate value. A、1%～2% ； B. 3%–6% ； C. 6%–9% ； D. 9%–12%. 152. The steam seal for turbine diaphragms generally uses (A). A. Combed-tooth steam seal ； B, J-shaped steam seal, C, fir-tree-shaped steam seal ； D. Labyrinth steam seal. 153. The relative internal efficiency of a turbine is the ratio of the turbine’s (C) to ( ). A. Shaft power/Ideal power ； B. Electrical power/Ideal power ； C. Internal power/Ideal power ； D. Input power/Ideal power 154. Under the same capacity and parameters, when comparing a regenerative cycle turbine with a pure condensing turbine: (B) A. The steam consumption rate increases, and the heat consumption rate also increases ； B. Steam consumption rate increases, heat consumption rate decreases. C. Steam consumption rate decreases, heat consumption rate increases ； D. The steam consumption rate decreases, and the heat consumption rate also decreases. 155. The main reason for negative differential expansion during the hot start of a turbine is (B). A. The steam temperature is too high during startup ； B. The main steam temperature is too low during startup ； C、Excessive warm-up time ； D. The warm-up time is too short. 156. When an increase in the conductivity of condensate is observed during the operation of a steam turbine, it should be judged as (C). A. Low condensate water pressure ； B、Supercooling of condensate water ； C. Condenser copper tube leakage ； D. Air leakage on the steam side of the condenser. 157、When the pressure increases while the temperature of the new steam remains unchanged, the steam in the last stages of the unit ( D ). A. Temperature decreases ； B. Rising temperature ； C. Decrease in humidity ； D. Increased humidity. 158. Under load, the thermal stress generated on the rotor surface is (A) stress. A. Tensile stress ； B. Compressive stress ； C. Alternating stress ； D. No stress is generated ； 159. The reason why the exhaust temperature rises when the turbine load is too low is (D) A. Excessively high vacuum B. Excessively high inlet steam temperature ； C. Excessively high steam inlet pressure. D. Insufficient steam flow into the turbine to cool the heat generated by blowdown friction losses. 160. With the initial temperature increased and all other conditions remaining unchanged, the relative internal efficiency of the turbine (A) A increases B decreases C remains unchanged D increases first and then decreases. 161. During the coastdown process after the turbine is shut down, due to the blowing effect and Poiseuille effect, there is a (A) sudden increase in the high and medium pressure rotors. A. Positive expansion difference B. Negative expansion difference ； C. It will not occur ； D. Sudden change in differential expansion. 162. Among heat, internal energy, humidity, superheat, and joule, the state parameters are _ D __. A. Everything except heat B. Only internal energy and superheat C. Only superheat D. Only internal energy E. Superheat and humidity. 163. The temperature before and after adiabatic throttling is __ D _. A. Increase B. Decrease C. Remain unchanged D. Not necessarily 164. The method for precisely regulating the power grid frequency is _ B _. A. Primary frequency modulation B. Secondary frequency modulation C. Differential regulation 165. In a control system, the effect of feedback on the slide valve is opposite to that of the governor on the slide valve; this is referred to as __ A. A. Negative feedback B. Positive feedback C. Dynamic feedback D. Static feedback 166. A slide valve that enables the control valve to open more dynamically when the grid frequency decreases, as well as to close it more dynamically in such situations, is called _ D _. A. Accelerator B. Regulator C. Safety device D. Corrector 167. The flow coefficient through the nozzle is defined as ___ A __. A: The ratio of the actual flow rate to the critical flow rate under the same initial and final parameters. B: The ratio of the actual flow rate to the ideal flow rate under the same initial and final parameters. C、The ratio of the critical flow rate to the maximum critical flow rate under the same initial and final parameters. D、The ratio of the critical flow rate to the ideal flow rate under the same initial and final parameters. 168. Using the steam consumption rate to measure the thermal efficiency of a turbine can be considered ___D__. A: The lower the steam consumption rate of the turbine, the higher its economic efficiency. B. For condensing units, the lower the steam consumption rate, the higher the economic efficiency. C. For back-pressure units as well, the lower the steam consumption rate, the higher the economic efficiency. D. For units of the same type, the lower the steam consumption rate, the higher the economic efficiency. 169. The force that easily causes damage to the turbine blades during operation is __C___. A. Centrifugal force generated by the blade mass B. Thermal stress C. Bending stress caused by steam D. Alternating stress due to steam flow. 170. When using a thermocouple for temperature measurement, the heat conduction error is related to the way in which the thermocouple makes contact with the surface being measured; among the four possible contact methods, the one that results in the greatest heat conduction error is __A__. A. Point contact B. Surface contact C. Isotherm line contact D. Discrete contact 171. The following statement regarding the criterion is incorrect: _C_. A. The larger the Nu value according to the Nusselt criterion, the stronger the heat transfer. B. The higher the Reynolds number Re, the relatively stronger the inertial force. C. The higher the Reynolds number Re, the lower Nu is, and the stronger the heat transfer. D. The value of the Reynolds number Re is related to the inertial force and viscous force of the fluid.