Gas Turbine Lab: Facilities and Equipment
Facilities & Equipment
The GTL has several state of the art data acquisition systems and research facilities used to study the aerodynamics, heat transfer, aeromechanics and structural dynamics of turbomachinery including the:
- High Speed Signal Processing and Data Acquisition Systems
- Turbine Test Facility
- Compressor Spin Pit Facility
- Large Spin Pit Facility
- Large Fan Spin Tank
- Small Calibration Facility
The GTL also employs a machinist and designers to fabricate custom parts using its machine shop and 3D printers.
Accordions
The OSU GTL has several different digital data acquisition systems in place so that the necessary data can be obtained at the required sampling frequency. At the present time, four different data systems are available as follows:
- CAMAC System- 256-channels, 100-Khz/channel sampling frequency (no multiplexing), 12-bit simultaneous, full programmable with Anti-aliasing filters
- Spectral Dynamics System – 388-channels, 500-Khz/channel sampling frequency with no multiplexing (some channels will sample at 2-MHz/channel if desired), 16-bit simultaneous fully programmable with Anti-aliasing filters.
- National Instruments System – 212-channels, 250-Khz/channel sampling frequency with no multiplexing, 16-bit simultaneous fully programmable with anti-aliasing filters
- RTD system – 125-channels, (500 KHz max rate, sustained rate is about 6-KHz/channel), 16-bit. Used to monitor the low frequency response instrumentation.
Each of these systems has associated preamplifiers that are relatively high bandwidth (on the order of 3-MHz), low noise amplifiers and power conditioners.
Data acquisition and signal conditioners housed in GTL control room
The hot section of an operating turbine is one of the more complicated flow environments associated with any practical machine; the flow is always unsteady, it may be transonic, it is three dimensional, and it is subject to strong body forces. Further, the interaction of these factors means that to obtain realistic information about the flow behavior inside an engine, all of these factors must be replicated. The Turbine Test Facility (TTF) is a short-duration facility designed to do just that. It is capable of matching stage pressure ratio, flow function, corrected speed, Mach number, Reynolds number, and other important non-dimensional parameters--both with and without cooling flows.
The Turbine Test Facility was designed and constructed at the Calspan Corporation in 1983 to produce conditions representative of the inlet to a turbine stage. In 1995, the researchers who designed, constructed, and operated this facility moved to The Ohio State University to form the Gas Turbine Laboratory (GTL), and they purchased the facility from Calspan. It now resides in the 12,000 square foot GTL at Don Scott Airport in Columbus, Ohio.
The TTF consists of a 100 foot long shock tunnel attached to a 32 foot long by 9 foot diameter dump tank in which the turbine rig is mounted. It can operate in either shock or blowdown mode depending on the test conditions needed. Shock tunnel mode creates the appropriate temperature and velocity conditions, while blowdown mode only generates the desired velocity.
A full-scale turbine rig is mounted inside the dump tank. These rigs are built using real engine hardware and are heavily instrumented. High-speed data is collected on the fixed shrouds and stators as well as the rotating blades to provide a good characterization of the unsteady effects that are a critical part of any engine's operation. Past experimental programs have included pressure, temperature (static and total), heat flux, and strain measurements. In addition, rotational encoders are used to precisely track the speed of the rotor. The rotor's acceleration can then be combined with its rotational inertia to provide aeroperformance measurements.
The Compressor Spin Pit Facility (CSPF) is designed to investigate a range of aeromechanic and structural dynamic phenomena for gas turbine engine hardware rotating at full engine speed. Installed in early 1999, the CSPF is intended to generate the data needed to validate emerging modeling and design tools for the development of aircraft gas turbine engines. Currently, the facility is applied to the study of blade-casing rub-in-systems of the type used on contemporary gas turbines to improve the tip clearance behavior for the engine's entire life span.
The CSPF consists of an in-ground containment tank that supports a highly rigid spindle rated at 20,000 rpm. Engine rotors undergoing investigation are mounted on the spindle with an adapter and can carry a variety of sensors for the desired measurements. Transducer power and signals are transmitted to and from controlling equipment through a high speed slip-ring. Additional mechanisms required in the experiments are attached inside the containment tank.
The CSPF is capable of accommodating medium to large compressor and turbine rotors (maximum diameter 34-in). In the ongoing compressor disk investigation, the facility is equipped with a metric fast-acting mechanism that has been developed to perform blade rubs at full engine speed. The facility is designed to allow insertion of a segment of engine casing into the path of the single or multiple bladed disk with predetermined blade incursion into the casing. The casing sector is mounted on a metric unit based on three piezoelectric load cells and attached to a support ring that swivels in the horizontal plane. The single throw by a fast acting gas piston attached to a cam follower is coupled to the support ring and brings the casing in and out of the path of the rotating blade for a few rubs over a time interval of about 20 milliseconds. The incursion of the rubs is prescribed by setting the initial position of the mechanism in increments of 0.2 thousandths of an inch.
The Gas Turbine Laboratory added a second underground spin tank to handle larger bladed disks, the Large Spin Pit Facility (LSPF). Building on the intense interest in data from the Compressor Spin Pit (CSPF) and lessons learned about the experimental process, this new facility is large enough to accommodate scaled bladed rotors up to 60 inches in diameter. Like the CSPF, its primary purpose is to study the physics of blade tip-rubs and other aeromechanic events.
Compared to the CSPF, distinctive features of the LSPF are
- A progressive incursion mechanism that allows control of the incursion rate and depth instead of just depth and
- Optical access windows for high-speed imaging of the rub event.
In addition to continuing aeromechanics research, this facility can also be used for internal heat transfer experiments investigating the flow through large-scale blade cooling passages.
The newest facility at the Gas Turbine Laboratory is the Large Fan Spin Tank (LFST). This facility has an inside diameter of 172 inches and can hold a bladed disk 14 feet in diameter. Like the underground spin tanks this facility was developed for aeromechanics and structural dynamics research. In particular the initial programs that will be run in this facility are blade damping, mistuning, and excitation studies. Additional future studies include:
- tip/shroud rub
- whirl
- blade out
- foreign object ingestion
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Flat plate experiments provide a way to explore challenging concepts in a simpler environment than the full turbine. At the GTL, they are commonly used to explore new experimental or data processing techniques as well as for comparison to computational predictions. Codes that are not able to predict heat transfer to a flat plate will have a difficult time making predictions for an operating turbine.
