UCCS PES/ENSC 2500: Renewable Energy Spring 2014 Test 3 name:

Transcription

1 UCCS PES/ENSC 2500: Renewable Energy Spring 2014 Test 3 name: 1. When a wind turbine is positioned between radio, television or microwave transmitter and receiver it can sometime reflect some of the in such a way that the reflected wave interferes with the original signal as it arrives at the receiver. a. Wind b. EM radiation c. Sound waves d. Visible light 2. Aerodynamic noise produced by wind turbines will tend to increase with the. a. Speed of rotation b. Speed of the wind c. Size of the tower d. Size of the nacelle 3. A wind farm at about a distance of 350 metres will have a noise level in db of approximately: a. 20 db b. 55 db c. 65 db d db 4. Wind Turbine noise which is produced by mechanical or electrical equipment, such as gearbox and the generator, is known as: a. Aerodynamic noise b. Swishing noise c. Mechanical noise d. White noise 5. Increasing the numbers of blades is likely to reduce. a. aerodynamic noise b. mechanical noise c. drag d. lift 6. The power output of a wind turbine varies with wind speed and every turbine has a characteristic. a. constant b. wind speed-power curve c. angular velocity d. tangential velocity 7. To control a turbine in high winds, rotor blades are designed so that above the rated wind speed they become less efficient because the angle of attack is approaching the. a. stall-control b. lift angle c. stall angle d. maximum velocity 8. If a wind turbine is rotating at a constant rotation speed, regardless of wind speed, and that the blade pitch angle is fixed. As the wind speed increases the tip speed ratio. a. Decreases b. Increases

2 Questions 9 13 refer to HAWT rotor blades wind forces and velocities. 9. When a HAWT blade is in motion, the direction from which the blade sees the relative wind velocity, W, is the resultant of the velocity, u, of the blade at that position and the wind velocity, V 1, at the rotor. a. angular b. radial c. centripetal d. tangential 10. Albert Betz showed in 1928 that the maximum fraction of the power in the wind that can be theoretically be extracted is. a. 27/16 b c. 100% d. 25% 11. The relative wind angle, Φ, is the angle that the relative wind makes with the blade (at a particular point with local radius r along the blade) and is measured from the. a. plane of rotation b. angle of rotation c. angle of attack d. Betz limit 12. The of the rotor in the plane of the rotor, in Nm on the blade is equal to the product of the net driving force in the plane of rotation (that is, the component of lift force in the plane of rotation minus the component of drag force in the rotor plane) and the local radius, r. a. inertia b. friction c. moment about the centre of rotation d. drag force 13. The magnitude and direction of the relative wind angle, Φ, varies along the length of the blade according to the local radius, r. This is because the, u, of a given blade element is equal to the rotor s angular velocity (Ώ) times the local radius, r, of the blade element. a. total torque b. driving force c. component of the drag force d. local tangential speed 14. The wind as seen from a point on a moving blade is known as the and its velocity is known as the relative wind velocity, W. a. relative wind b. relative wind angle c. lift d. drag

3 15. The angle from which the point on the moving blade see the relative wind is known as the, Φ, and is measured from the tangential velocity vector, u. a. relative wind b. relative wind velocity c. relative wind angle d. angle of attack 16. Each aerofoil has an angle of attack at which the lift to drag ration (C L / C D ) is at a. a. maximum b. minimum c. neutral point d. stall 17. occurs when the flow suddenly leaves the suction side of the aerofoil (when the angle of attack becomes too large), resulting in a dramatic loss in lift and an increase in drag. a. Drag b. Stall c. Lift d. Turbine shutdown 18. The angle which an object makes with the direction of airflow, measured against a reference line in the object, is called the. a. chord line b. lift c. drag d. angle of attack 19. The aero-foils are optimized to produce most lift when the underside of the aerofoil is closest to the direction from which the air is flowing. a. asymmetrical b. symmetrical 20. aero-foils are able to induce lift equally well (although in opposite directions) when the air flow is coming from either side of them. a. asymmetrical b. symmetrical 21. The faster the airflow, the lower the pressure (i.e. the greater the suction effect ). This phenomenon is known as the. The lift force thus acts as a suction or pulling force on the object, in a direction at right angles to the airflow. a. Venturi effect b. Darcy s Law c. Bernoulli effect d. Euler equation 22. The is the component that is at right angles to the direction of the air stream. a. drag force b. lift force c. chord line d. trailing edge

4 23. The is the component that is in line with the direction of the air stream. a. drag force b. lift force c. chord line d. trailing edge 24. The regions marked high and low relate to the atmospheric pressure and the contours represent lines of equal pressure are called. a. Westerlies b. Polar easterlies c. isobars d. Coriolis effects 25. As the Earth is rotating, the winds are subjected to a phenomenon known as (the). a. Venturi effect b. Bernoulli effect c. Coriolis effect d. doldrums 26. Flow is hyper-sonic when: a. Mach = 1 b. Mach < 1 c. Mach > 1 d. Mach >> Flow is super-sonic when: a. Mach < 1 b. Mach > 1 c. Mach >> 1 d. Mach = Winds moving East of West along parallels of latitude are called: a. Meridional flows b. Zonal flows c. Capricorn flows d. Cancer flows 29. A barometer that uses no liquid is called: a. Aneroid b. Baros c. Hg barometer d. Torricelli barometer 30. A low pressure belt (with cloudy and rainy weather patterns) is created at the equator due to warm humid air rising in the atmosphere until it reaches the. a. troposphere b. tropopause c. ionosphere d. trade winds

5 31. As the Earth rotates, North bound winds are caused to veer ( westerlies ) in the Northern Hemisphere. a. right b. left c. up d. down 32. South bound winds veer ( trade winds ) in the Northern Hemisphere. a. right b. left c. up d. down 33. Air that rises at the polar fronts moves poleward and sinks to the surface at the poles as it cools. It then returns to the 60-degree latitude region completing the circulation of what is known as the polar. a. Ferrel cell b. trade winds c. westerlies d. Hadley cell 34. Winds North or South along the longitudes are called: a. Zonal flows b. Bernoulli winds c. Venturi winds d. Meridional flows 35. The turbine uses nozzles aimed at cupped blades to develop rotational speeds up to 1300 rpm. a. Francis b. Kaplan c. Pelton d. Faraday 36. Water flow to the power plant from the dam is through a large pipe called the: a. head b. penstock c. Kaplan d. Pelton 37. Modern turbines are of two major types - the & the reaction. a. action b. fixed c. pitched d. impulse 38. Electricity that can be generated by small-scale or low-head units is sometimes referred to as: a. penstock b. Pelton c. Kaplan d. micro-hydro

6 39. Fourneyron s turbine is a machine. a. horizontal-axis b. vertical-axis c. super charged d. turbo charged 40. Fourneyron s turbine use to direct the water, on to the blades, considering the fact that the turbine runs completely submerged. a. Pelton runners b. breastshot wheels c. guide vanes d. undershot wheels