Research Article Enhancing the Supersonic Wind Tunnel Performance Based on Plenum Temperature Control A. Nazarian Shahrbabaki, M. Bazazzadeh, A. Shahriari, and M. Dehghan Manshadi Department of Mechanical & Aerospace Engineering, Malek-Ashtar University of Technology, Shahin Shahr, Isfahan 83145/115, Iran Correspondence should be addressed to A. Nazarian shahrbabaki; a.n.shahrbabaki@gmail.com Received 9 February 2014; Accepted 4 March 2014; Published 2 April 2014 Academic Editors: E. J. Avital and Y. Shi Copyright © 2014 A. Nazarian shahrbabaki et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te application of fuzzy logic controllers (FLCs) to the control of nonlinear processes, typically controlled by a human operator, is a topic of much study. In this paper, the design and application of a FLC is discussed to control the plenum chamber temperature for a blowdown supersonic wind tunnel (BSWT) with the aim of achieving the accurate and desired results. In this regard, frst, a nonlinear mathematical model of special BSWT is developed in Matlab/Simulink sofware environment. Next, an artifcially intelligent controller is designed using fuzzy logic approach. For this purpose, a proportional-derivative FLC (PD-FLC) system is developed in the Simulink toolbox to control the plenum stagnation temperature using a heater upstream of the plenum chamber. Finally, the system simulation results inside of the temperature and pressure controllers in comparison with the experimental run are presented. Te results for Mach 2.5 blowdown run show the great performance of the Wind Tunnel Simulator Model and its temperature controller system. 1. Introduction Blowdown supersonic wind tunnels (BSWTs) deliver fow at constant stagnation temperature and pressure. Te stagnation temperature is generally regarded to be equal to the plenum temperature which is controlled by heater upstream of the plenum chamber. During a blowdown run, the storage tank temperature and pressure that supplies plenum chamber fow decrease continuously. Tus, to maintain a constant plenum pressure as close as possible to a setpoint pressure signal, the regulator or control valve must open progressively. Besides, to maintain a constant stagnation temperature in the plenum chamber, a heater must operate continuously during a supersonic run [1–3]. Te controller must operate at diferent stagnation pressures and Mach numbers and has to be robust to accommodate the varying pressure and mass fow requirements safely. New concepts for control are under implementation with the goal of reducing transition phase and overall loads on the models [4, 5]. Te block diagram of the control systems in the proposed BSWT is illustrated in Figure 1. Fuzzy logic has been the area of heated debate and much controversy during the last decades. Te frst paper in fuzzy set theory, which is now considered to be the seminar paper of the subject, was written by Zadeh et al. [6], who is considered the founding father of the feld. In that work, Zadeh was implicitly advancing the concept of approximate human reasoning to make efective decisions on the basis of the available imprecise, linguistic information. In the 1970s, King and Mamdani [7] studied the applica- tion of FLCs to the control of nonlinear industrial processes that typically can only be controlled successfully by a human operator. Te idea of FLCs has become a common solution in recent years, with applications ranging from automation of industrial processes to control of electronic devices in consumer products. Te design and application of a FLC for the control of plenum chamber temperature in several wind tunnels at NASA’s Langley Research Center (LaRC) in Hampton, VA, is described [8]. Te intelligent controlling approaches like fuzzy logic (FL) will provide the required scope for wind tunnels to be more efcient, safe, and economic. Te approaches will help to enable a level of performance that far exceeds that of today’s wind tunnel in terms of reduction of harmful emissions, maximization of run time, and minimization of noise, while improving system afordability and safety. Hindawi Publishing Corporation ISRN Aerospace Engineering Volume 2014, Article ID 317049, 6 pages http://dx.doi.org/10.1155/2014/317049