Question

If there are no guide vanes, \( C_1 \) will be radial (\( \alpha_1 = 90^\circ \)), then this particular condition is expressed as

• A. pre-whirling
• B. surging
• C. zero whirl
• D. stalling

Hint:

Zero whirl occurs when the absolute velocity enters radially.

Answer 1

The Correct Option is C

In the context of aerospace engineering, particularly in turbine machinery, the absence of guide vanes leads to a condition where \( C_1 \), the absolute velocity of the fluid entering the wheel, is radial. This means the inlet flow angle \( \alpha_1 \) is \( 90^\circ \). In such a scenario, there is no component of velocity in the tangential direction, which means that no whirl is imparted to the fluid by the incoming flow. Consequently, this condition is known as zero whirl. This terminology indicates that the fluid enters the turbine without any rotational momentum imparted before contact with the rotor, which distinguishes it from other conditions like pre-whirling, surging, or stalling.