<p>Tip clearance flow is not only the source of undesirable noise but also a potential indicator for critical operating conditions with rotating stall or surge. It can also induce blade vibration, which would cause premature blade failure when the vibration is strong enough. The paper presents experimental studies on the effects of tip clearance on the stall inception process in a low-speed high-load single stage fan with different tip clearance. From the point of view of flow range, it has been proved by experiments and computations that there is an optimal gap value, and an explanation is given according to different stall mechanisms of large and small tip clearance. However, the experiment of no tip clearance is not easy to achieve. In this experiment, a wearable soft wall casing is used to achieve "zero clearance", and a clearer conclusion is obtained. The pressure rise and efficiency are improved at small tip clearance. Instantaneous Casing Pressure Field Measurement was carried out: instantaneous casing pressure fields in one rotor passage region were measured by 32 high response pressure transducers mounted on the casing wall. At the near stall point with large tip clearance, a narrow band increase of the amplitudes in the frequency spectrum at roughly half of the blade passing frequency can be observed according to the spectrum of static pressure at a point on the endwall near the leading edge. Before rotating stall, with the throttling process, the center frequency of the hump moves to high frequency and the amplitude increases. This phenomenon is explained from two aspects: tip clearance flow structure and pressure signal mode decomposition.</p>

Experimental Study on Different Tip Clearance of Low-Speed Axial Fan

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.