Measuring the pitch angle — Lesson 1

This lesson covers the measurement of flow angles using mechanical probes, particularly in the context of turbo machines. It explains the importance of flow angles in characterizing the turbo machines flow field and their direct relation to the phenomenon of work interchange. The lesson also discusses the calibration of mechanical probes and the operational principle of these probes. It further explains the use of three-hole, four-hole, and five-hole probes, emphasizing that three-hole probes cannot measure pitch characteristics, which are crucial for turbo machines. The lesson concludes by outlining the procedures for using pressure probes to measure flow angles and the importance of calibration.

Video Highlights

02:18 - Importance of measuring the changes in flow angle using mechanical probes
03:58 - Use of mechanical probes in measuring pitch angle
07:21 - Use of pressure probes in measuring the flow angles of turbo machines
13:50 - Calibration of probes and the importance of calibration in experimental fluid dynamics
23:24 - Construction and operational principle of five-hole probes
52:53 - Null method and the second method in measuring flow direction using probes

Key Takeaways

- Flow angles are crucial in characterizing the turbo machines flow field and are directly related to the phenomenon of work interchange.
- Mechanical probes, specifically three-hole, four-hole, and five-hole probes, are used to measure these flow angles.
- Three-hole probes cannot measure pitch characteristics, which are important for turbo machines.
- Before using a probe, it must be calibrated to ensure its sensitivity to the change in flow direction.
- The calibration process involves using a free jet of fluid produced by a nozzle placed at the exit of a large plenum chamber.
- The pitch and yaw angles can be measured during calibration by rotating the test probe about its axis.