NASA Logo, External Link
Facebook icon, External Link to NASA STI page on Facebook Twitter icon, External Link to NASA STI on Twitter YouTube icon, External Link to NASA STI Channel on YouTube RSS icon, External Link to New NASA STI RSS Feed AddThis share icon
 

Record Details

Record 1 of 3644
Automatic control of cryogenic wind tunnels
Availability: Go to Request Form
Author and Affiliation:
Balakrishna, S.(NASA Langley Research Center, Hampton, VA, United States)
Abstract: Inadequate Reynolds number similarity in testing of scaled models affects the quality of aerodynamic data from wind tunnels. This is due to scale effects of boundary-layer shock wave interaction which is likely to be severe at transonic speeds. The idea of operation of wind tunnels using test gas cooled to cryogenic temperatures has yielded a quantrum jump in the ability to realize full scale Reynolds number flow similarity in small transonic tunnels. In such tunnels, the basic flow control problem consists of obtaining and maintaining the desired test section flow parameters. Mach number, Reynolds number, and dynamic pressure are the three flow parameters that are usually required to be kept constant during the period of model aerodynamic data acquisition. The series of activity involved in modeling, control law development, mechanization of the control laws on a microcomputer, and the performance of a globally stable automatic control system for the 0.3-m Transonic Cryogenic Tunnel (TCT) are discussed. A lumped multi-variable nonlinear dynamic model of the cryogenic tunnel, generation of a set of linear control laws for small perturbation, and nonlinear control strategy for large set point changes including tunnel trajectory control are described. The details of mechanization of the control laws on a 16 bit microcomputer system, the software features, operator interface, the display and safety are discussed. The controller is shown to provide globally stable and reliable temperature control to + or - 0.2 K, pressure to + or - 0.07 psi and Mach number to + or - 0.002 of the set point value. This performance is obtained both during large set point commands as for a tunnel cooldown, and during aerodynamic data acquisition with intrusive activity like geometrical changes in the test section such as angle of attack changes, drag rake movements, wall adaptation and sidewall boundary-layer removal. Feasibility of the use of an automatic Reynolds number control mode with fixed Mach number control is demonstrated.
Publication Date: Nov 01, 1989
Document ID:
19900006641
(Acquired Nov 06, 1995)
Accession Number: 90N15957
Subject Category: RESEARCH AND SUPPORT FACILITIES (AIR)
Document Type: Conference Paper
Publication Information: AGARD, Special Course on Advances in Cryogenic Wind Tunnel Technology; p. 15 p
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: NASA Langley Research Center; Hampton, VA, United States
Description: 15p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution within the U.S. granted by agreement
NASA Terms: AUTOMATIC CONTROL; CONTROL THEORY; CRYOGENIC WIND TUNNELS; FLOW CHARACTERISTICS; SHOCK WAVE INTERACTION; TRANSONIC WIND TUNNELS; CONTROLLERS; CRYOGENIC TEMPERATURE; DATA ACQUISITION; DRAG; DYNAMIC PRESSURE; MACH NUMBER; REYNOLDS NUMBER; SAFETY; SCALE EFFECT; TEMPERATURE CONTROL; TRAJECTORY CONTROL; WIND TUNNEL WALLS
Imprint And Other Notes: In AGARD, Special Course on Advances in Cryogenic Wind Tunnel Technology 15 p (SEE N90-15939 08-09)
› Back to Top
Find Similar Records
NASA Logo, External Link
NASA Official: Gerald Steeman
Site Curator: STI Program
Last Modified: August 27, 2013
Contact Us