This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Horizontal Axis Wind Mill”.
1. In which of the following, does machine rotor drives through a step up gear box?
a) Horizontal axis with two aerodynamic blades
b) Horizontal axis propeller type wind mill
c) Horizontal axis multi bladed type wind mill
d) Sail type wind mill
View Answer
Explanation: In horizontal axis with two aerodynamic type windmill the machine rotor drives through a step up gear box. The blade rotor is designed to orient downwind of the tower. The components are mounted on bed plate which is attached on a pintle at the top of the tower.
2. The rotor blades are continuously flexed by unsteady aerodynamic gravitational and inertia loads.
a) True
b) False
View Answer
Explanation: The rotor blades are continuously flexed by unsteady aerodynamic gravitational and inertia loads, when the machine is in operation. If the blades are made using metal, flexing reduces their fatigue life.
3. Which type of the following consists of single blade?
a) Horizontal axis with two aerodynamic blades
b) Horizontal axis propeller type wind mill
c) Horizontal axis multi bladed type wind mill
d) Sail type wind mill
View Answer
Explanation: Horizontal axis propeller type wind mill consists of a long blade mounted on a rigid hub, induction generator and gear box. If extremely long blades are mounted on rigid hub, large blade root bending moments occur due to tower shadow, gravity and sudden shifts in wind directions.
4. Which windmill blades are made by an array of wooden slats?
a) Horizontal axis with two aerodynamic blades
b) Horizontal axis propeller type wind mill
c) Horizontal axis multi bladed type wind mill
d) Horizontal axis wind mill Dutch type
View Answer
Explanation: Dutch type wind mill is one of the oldest wind mills in designs. The blade surfaces are made from an array of wooden slats which rotates at high wind speeds. These types of wind mill are cheap to build since the wood is made use of to build.
5. Which type of windmill blades are made out of sheet metal or aluminum?
a) Horizontal axis with two aerodynamic blades
b) Horizontal axis propeller type wind mill
c) Horizontal axis multi bladed type wind mill
d) Sail type wind mill
View Answer
Explanation: Horizontal axis multi blade windmill is made from sheet metal or aluminum. The rotors have high strength to weight ratios. They have good power coefficient, high starting torque and added advantages of simplicity and low cost.
6. Which type of wind mills blade are made out of cloth?
a) Horizontal axis with two aerodynamic blades
b) Horizontal axis propeller type wind mill
c) Horizontal axis multi bladed type wind mill
d) Sail type wind mill
View Answer
Explanation: The blade surface of sail type wind mill is made of cloth, nylon or plastics arranged as mast and pole or sail wings. There is also variation in the number of sails used. Sails are found in different designs, from primitive common sails to the advances patent sails.
7. Which type of windmill has better performance?
a) Vertical type wind mills
b) Darrieus type machines
c) Magnus effect rotor
d) Horizontal type windmills
View Answer
Explanation: The horizontal axis mills generally have netter performance. They have been used for various applications including electric power generation, and pumping water. The latter introduces some complexity into the design as the mechanical energy has to be transmitted over a distance.
8. What does TSR stand for in design consideration of wind mills?
a) Tip speed ratio
b) Torque-synchronous ratio
c) Tip suspension ratio
d) Temporary speed restriction
View Answer
Explanation: The tip speed ratio, X, or TSR for wind turbines is the ratio between the tangential speed of the tip of a blade and the actual speed of the wind. The tip speed ratio is related to efficiency, with the optimum varying with blade design.
9. With upto how many propellers can windmills are built?
a) 4
b) 2
c) 7
d) 6
View Answer
Explanation: Wind turbines have been built with upto six propellers type blades but two and three bladed propellers are most common. A one bladed rotor with a balancing counter weight has some advantages, including lower weight and cost and simpler controls, over the multi-bladed type.
10. Turbines with how many propellers are used in order to avoid vibrations?
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: Turbines with three blades are used to avoid vibrations that occur due to the turning or yawing of the rotor in order to face in into the wind. However, this problem can be overcome by controlling the yaw rate.
11. What type of cross sections does wind turbine blades have?
a) Penta hedral cross section
b) Air foiled type cross section
c) Radar cross section
d) Turbo cross section
View Answer
Explanation: Wind turbine blades have an air foiled type of cross section and a variable pitch. They are slightly twisted from the outer tip to the root in order to reduce the tendency for the rotor to stall. The blades can also have constant chord length.
12. What does WECS stands for?
a) Wind energy conversion system
b) Wind engine control system
c) Wind energy combined system
d) Wind engine comparison system
View Answer
Explanation: A wind energy conversion system (WECS), or wind energy harvester is a machine that, powered by the energy of the wind, generates mechanical energy that can be used to directly power machinery or to power an electrical generator for making electricity.
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