The turbine used in this study is a large stage and one half (High Pressure Vane - HPV, High Pressure Blade-HPB, and Low Pressure Vane-LPV) machine, configured in a manner that replicates current placement of the airfoil rows in a modern engine (as opposed to a machine configured with the airfoil rows positioned to demonstrate some particular physics such as clocking). Since it is a modern machine, the airfoils are of very strong three-dimensional design and the total pressure ratio across the machine is in excess of 5.
A sketch of the rig is shown in Figure 3.3 with some of the main components highlighted. One can see at this scale the air-motor (used to drive the turbine up to speed at the beginning of the experiment), the two slip rings, the turbine stage, the inlet and the exit choke. The different colors represent the major sub-assemblies used during the build-up. A typical rig such as this generally has on the order of 100-200 part/assembly drawings associated with it. An actual picture of the rig is shown in Figure 3.4 (the direction of the rig is reversed from the sketch with the inlet being on the right side), with the Director of the Lab, Dr. Dunn, as the rig was ready to be installed into the TTF.
Originally, the model was designed to use a 200-channel slip ring unit in the front and a 300-channel slip ring in the rear, but a failure on the 300-channel slip ring required that the final rig be run with two 200-channel slip rings.
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3 6 12
0
Nozzle Inlet
(Not shown completely) Air Motor
Forward slip-ring Turbine Stage Aft slip-ring
Exit Choke
Figure 3.3 Sketch of Overall Rig
Figure 3.4 Picture of Rig (Reversed from Sketch) Ready to Go Into the Dump Tank
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In the picture, one can see the instrument cables exiting the rig. The long inlet is designed to position the intake to the model at the correct position in the expansion nozzle to obtain the design total pressure. The mass flow rate at the tunnel throat is on the order of 500 Kg/sec, whereas the mass flow through the rigs is on the order of 10-50 Kg/sec, so that most of the mass-flow is by-passed around the rig.
A more detailed sketch of the main turbine stage is shown in Figure 3.5.
Inlet Rakes Exit Rakes
Exit Choke (Movable)
HPV
HPB
LPV Flow Path
Figure 3.5 Main Flowpath
Here one can see the relative location of the airfoil rows. Scientifically, the region of the flow path under investigation is defined by the inlet and exit rakes. At each of these locations, there are two total temperature rakes (5 sensors each placed at the center of equal areas) and two total pressure rakes (5 sensors each, similar placement). In this rig there are 38 Vanes (both HP and LP) and 72 Blades. The exit choke is movable, so that a variety of pressure ratios are available.
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As mentioned earlier, this part of the research effort was composed of two separate entries. The first entry was intended to investigate the aerodynamics of the turbine stage and contained mostly pressure data and utilized only one slip ring. The second entry added rotor, rotor shroud, and low vane heat-flux sensors, rotor tip pressures and heat-flux, and the second slip ring. At the end of the second entry there were 485 instruments allocated as shown below (these do not include any special instruments used for instrument development, and not primarily for model data acquisition).
HFG Pressures RTDs TC's Heaters
Rotor (Actual) 99 65 8 8
High Vane 80 60 2
Rotor Shroud 12 8
Low Vane 34 49 2
Flowpath 26 12 20
Total numbers 225 208 24 20 8
Number of Facility channels 7
Main HFG Exp 276
Main pressure 247
Table 3.1 Instrument Count/Location
Each airfoil had sensors distributed at three span locations (15, 50, and 90% spans, with the exception of the LPV which was at 10, 50, and 90% spans), and there were heat-flux and pressure sensors mounted on the HPV inner and outer endwalls, and pressure sensors mounted in the area between the rotor and the LPV on the inner and outer endwalls. The rotor was instrumented with heat-flux sensors and pressure sensors on the platform, and on various blade-tip configurations in addition to the three spanwise locations noted above. There were also pressures and heat-flux sensors on the rotor shroud.
The pressure sensors where variants of the Kulite XCQ-062-100A sensors
mounted either as total pressures (for the rakes) static pressures (at the rake locations), or
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as chip sensors on the airfoils themselves. The Heat-Flux gauges were all built at OSU and are of similar type to the Calspan heat-flux gauges (effectively a thin platinum film on a Pyrex substrate).
Rotor position was determined using an encoder that generates 500 pulses per revolution and an index pulse, which generates a 1/rev location (a location relative to the trailing edge of a vane). Both entries used a similar 500 pulse encoder, but the second entry included extra electronics that took the quadrature signal of the encoder (usually an A and a B circuit, each generating 500 pulses per rev, but 1/4 pulse out of phase with each other) and passed it through an “exclusive or gate” to generate a pulse train of 1000 pulses to rev, thereby increasing the spatial resolution.