Upgrade Transonic Compressor Test Rig Data Acquisition System

New software programming using commercial off-the-shelf software for acquiring data, processing data, displaying results, and generating reports is implemented to improve the performance of a legacy system.

Figure 1. Transonic Compressor Test Rig Design.

The Naval Postgraduate School (NPS) has frequently used the transonic compressor test rig (TCR) to test new axial transonic compressor rotors and casings for design and performance improvements. Technology has improved the ability to create more detailed designs and has led to an increase in testing at NPS. While the rotors and casings produced are becoming more advanced, the data acquisition system (DAS) used to measure the performance of these products became slow and outdated in comparison to currently available DAS products.

Figure 2. Probe Positions of the Test Section.

Consequently, this work involves the procurement, design, and implementation of upgrades to the current DAS.

The TCR diagram in Figure 1 consists of a transonic axial rotor mounted on a single shaft with two opposed rotor, single stage air-operated drive turbines. The turbines are powered by supply air from an Allis Chalmers compressor. Atmospheric air is drawn into the inlet plenum and throttled via an electrically actuated butterfly valve; it then passes through the settling chamber, flow rate nozzle and finally to the transonic axial rotor where it is expelled back to the atmosphere.

Mass flow is measured by a flow rate nozzle placed just aft of the settling chamber depicted in Figure 1. Inlet stagnation pressure and stagnation temperature are measured with two combination-probes. A static pressure port measures inlet static pressure. Outlet stagnation pressure is measured with eleven Kiel pressure probes and nine combination-probes. Outlet stagnation temperature is measured by the nine combination probes. Static pressure is measured with four static pressure ports in the hub, and two static pressure ports in the casing. Inlet measurements are taken at AS1 and outlet measurements are taken at AS3, as shown in Figure 2.

Throughflow analysis of the TCR utilizes the stream-tube method. Probes measure streamlines of the stream-tube at stations AS1 and AS3. The probes are placed at various radial placements to create inlet and outlet pressure profiles. The stage or rotor performance is calculated using the mass flow rate and circumferentially mass averaged pressures and temperatures. The throughflow analysis provides the stagnation pressure ratio, isentropic efficiency, and power. The experimental results were compared to the isentropic, or idealized, results as a useful measure of the compressor’s performance.

This work was done by Thomas D. Belna for the Naval Postgraduate School. For more information, download the Technical Support Package (free white paper) at mobilityengineeringtech.com/tsp under the Test & Measurement category. NPS-0025

This Brief includes a Technical Support Package (TSP).
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Upgrade Transonic Compressor Test Rig Data Acquisition System

(reference NPS-0025) is currently available for download from the TSP library.

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