Turbomachinery velocity triangle problem

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SUMMARY

The discussion centers on solving a turbomachinery velocity triangle problem involving incompressible air flow across a rotor. The absolute velocity increases from 15 m/s to 25 m/s, and the torque is zero, indicating that the device is a pump rather than a turbine. Using Euler's Torque equation, the outlet velocity was calculated to be 20.57 m/s. The direction of the absolute velocity at the outlet needs to be determined using velocity triangles.

PREREQUISITES
  • Understanding of Euler's Torque equation
  • Knowledge of velocity triangles in turbomachinery
  • Familiarity with the concepts of pumps and turbines
  • Basic trigonometry for calculating angles and velocities
NEXT STEPS
  • Study the application of Euler's Torque equation in turbomachinery
  • Learn how to construct and analyze velocity triangles in fluid dynamics
  • Research the differences between pumps and turbines in terms of fluid mechanics
  • Explore the implications of torque in rotor dynamics and its effect on performance
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Mechanical engineers, students studying fluid dynamics, and professionals involved in turbomachinery design and analysis will benefit from this discussion.

MacLaddy
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Homework Statement



Air (assumed incompressible) flows across the rotor shown in the figure such that the magnitude of the absolute velocity increases from 15 m/s to 25 m/s. Measurements indicate that the absolute velocity at the inlet is in the direction shown. Determine the direction of the absolute velocity at the outlet if the fluid puts no torque on the rotor. Is the rotation CW or CCW? Is this device a pump or a turbine?

Homework Equations



Euler's Torque equation

T=\dot{m}(r_2V_{\theta2}-r_1V_{\theta1})

The Attempt at a Solution


[/B]
As torque = 0

T=\dot{m}(r_2V_{\theta2}-r_1V_{\theta1})=0

(r_2V_{\theta2})=(r_1V_{\theta1})

V_{\theta2}=V_{\theta1}*\frac{r_1}{r_2}=15\sin{60}*\frac{1.9}{1.2}=20.57 m/s

No idea where to take it from here. I can't tell from the problem statement if the direction of V_2 is as indicated.

If there is no torque, as indicated, then I would assume that this must be a pump--as the fluid isn't doing any work on the rotor. However, I believe I need to prove this with velocity triangles and the like.

Any help would be appreciated.
Mac
 
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It looks like you found the velocity in the same direction as V1. The problem gives you the full velocity. You can complete the triangle using the Pythagorean thm, and find the angle from that.
 

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