Author: Zhang, Kuo
Title: Closed-loop control of a round jet using two pulsed microjects
Degree: M.Sc.
Year: 2013
Subject: Jets -- Fluid dynamics.
Fluid mechanics
Hong Kong Polytechnic University -- Dissertations
Department: Department of Mechanical Engineering
Pages: ix, 77 leaves : ill. ; 30 cm.
Language: English
Abstract: In this thesis, closed-loop control of an air round jet using two radial pulsed air microjets was investigated experimentally. The jet control setup consists of main-jet and microjet modules, the latter including a stationary and a rotating disk both drilled with orifices 17mm upstream from the main jet exit. The rotating disk was drived using a servo motor. Once a stationary and a rotating orifice are aligned, an unsteady microjet emits towards the main jet centreline. Reynolds number based on main jet exit diameter was 8000. Hot wire and Particle Image Velocimetry (PIV) techniques were implemented. Basing on the dependences of jet decay on the mass flow rate and excitation frequency of microjets in open-loop control, a closed-loop control has been developed and the best control performance charaterized by the jet decay rate can be achieved automatically, suggesting the robustness of the technique. An optimal controller was established using the dSAPCE system combined with Matlab software. The fundemental control algorithm is a non-model-based optimal parameter seeking approach, which can be regarded as a black block with the input u and the output y without an input-output relation y = f(u) identified initially. And the input u can be online adjusted so that the optimal output y* can be automatically achieved, that is, y* = f(u*), where u* is the input value corresponding to the optimal output. In present study, the input of the controller is instantaneous signal of hot wire and the output signal excitation frequency of microjets. The control performance in closed-loop control is compared with those obtained in open-loop control.
Rights: All rights reserved
Access: restricted access

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