DSGN303 Mechanical System Design Module 9: Wind Energy Quiz

Why do wind turbines suffer from fatigue failure?

They do not have guyed tower support.
They experience natural resonance in the structure. (correct)
They have low power coefficient.
They use concentrators and diffusers.

What effect does the periodic variation of torque from the wind have on wind turbines?

It requires concentrators and diffusers.
It increases the power coefficient of the turbines.
It causes natural resonance in the structure.
It affects the output power of the turbines and causes cyclic load on the tower. (correct)

Why do high power turbines need guyed tower support?

To increase natural resonance in the structure.
To prevent fatigue failure. (correct)
Due to the lower power coefficient.
Because they require extra stability.

What is the role of concentrators around horizontal-axis wind turbines?

Concentrate wind from outside the rotor. (C) Signup and view all the answers

How does the solidity factor affect power generation turbines?

Lower solidity factor leads to fast shaft rotational speed. (B) Signup and view all the answers

What effect does increasing the length of blades have on power generation in wind turbines?

Higher power generated. (A) Signup and view all the answers

What is the formula for the maximum torque on a turbine rotor?

$\frac{1}{2} \rho A_b V_o^2 R^2$ (C) Signup and view all the answers

How is the static pressure difference (∆𝑝) calculated across the turbine using the Bernoulli equation?

$\Delta p = p_1 - p_2 = \rho V_o^2 - V_e^2$ (C) Signup and view all the answers

What does the axial thrust on the turbine depend on?

The blade area of the turbine (A) Signup and view all the answers

How is the actual rotor torque of a wind turbine calculated in reference to the maximum torque?

$T = \frac{C_T}{T_{max}}$ (B) Signup and view all the answers

What is the formula for the axial thrust on the turbine?

$F = \frac{V_o^2}{\rho A_b}$ (B) Signup and view all the answers

What is the primary factor in calculating the pressure variation across the wind turbine?

Blade radius of the turbine (D) Signup and view all the answers

What is the wind speed probability distribution function commonly approximated by?

Weibull distribution function (C) Signup and view all the answers

What is the value of k in the one-parameter Rayleigh distribution?

2 (C) Signup and view all the answers

What is the kinetic energy of an air stream having velocity Vo and density ρ?

1/2(ρQ)V_o2 (D) Signup and view all the answers

What is the formula for the wind power of an air stream available to wind turbines?

P_o = 1/8(ρAV_o3) (C) Signup and view all the answers

What is the rotor swept area also known as?

Scavenged area (A) Signup and view all the answers

What is the formula for the wind power of an air stream in terms of the diameter of the circular area swept by the turbine blades?

P_o = ρV_o3Db2/8 (C) Signup and view all the answers

What is the usual equivalent of the rated power of a generator?

The generator capacity that can be continuously maintained without overheating (B) Signup and view all the answers

What is the purpose of regulating the torque and power harnessed by a wind turbine?

To act on the lift force dependent on the angle α (D) Signup and view all the answers

What happens to the power generated by a turbine when 𝑉𝑜 > 𝑉𝑐𝑢𝑡−𝑜𝑢𝑡?

The turbine is disconnected using a mechanical brake (B) Signup and view all the answers

What is the effect of increasing the angle of attack α in passive stall control?

The angle of attack α increases with wind speed causing increased drag and progressive stall of the blades (D) Signup and view all the answers

What is the outcome of stall in a wind turbine?

Formation of a wake and loss of lift due to the loss of negative pressure (D) Signup and view all the answers

What is the common method of power control in wind turbines?

Passive stall (A) Signup and view all the answers

What is the primary cause of wind patterns at the global scale?

The pressure differential between the equator and the poles (C) Signup and view all the answers

What happens to the hot air at 30o to 60o latitudes?

It cools down and drops (D) Signup and view all the answers

What is affected by the Earth's rotational motion?

Both global and local wind patterns (B) Signup and view all the answers

What is the cause of prevailing westerlies in both hemispheres?

The cooling down and dropping of hot air (D) Signup and view all the answers

What is the characteristic of ocean surface water?

It has a larger thermal capacity than land (D) Signup and view all the answers

What is the effect of solar radiation on land masses?

It heats up faster than oceans (D) Signup and view all the answers