Bipin M.. Kanth - Captronic Systems
Anu Kalidas - Captronic Systems
The DAQ system consists of a server and multiple client programs developed using LabVIEW. The system is incorporated in the main server PC for the acquisition of 1024 channels and NI PCI-6052E E Series DAQ cards are used for multiplexed data acquisition. Acquired parameters include temperature, pressure, speed, flow, and vibration. The parameters are conditioned using SCXI signal conditioning modules and the acquired data are stored on the PC for future analysis. Multiple clients can view predetermined acquisition parameters during and after the engine run.
The expandability and modularity of SCXI made the signal conditioning requirements simple for the high-channel-count DAQ system. Also, because SCXI is a programmable signal conditioning system, the channel configuration is flexible. The operator can expand the systems capabilities with no additional programming – making changes is as simple as plugging in another module to include additional signals
The DAQ system has a main server that has a PCI-6052E DAQ card to acquire data from sensors connected at different locations of the engine undergoing test. The acquired data is converted to corresponding engineering units and displayed on the main server for the operator to view and, if the value is beyond an allowable limit, take necessary action. The acquired data is also transmitted to main server clients and intermediate server clients.
Challenges for Testing Gas Turbines
The gas turbine engine is subjected to tests for studying the behavior of various parameters including temperature, pressure, speed, flow, and vibration in various sections of the engine. This requires software that can quickly calibrate up to one thousand channels and provide reliable data for correct analysis during and after the test.
Additionally, the successful working of a gas turbine engine involves many departments; therefore, during engine testing, the test parameters should be available for all the departments without much delay. Consequently, apart from being processed and displayed in the operator room, the acquired data also needs to be distributed at the same time to various clients separated geographically.
These departments (clients) have their own set of channels that are of interest and need to be given the option to configure channels according to their requirements before viewing the data. Also, because clients need a pictorial representation of the parameters with respect to any section of the engine for better understanding, mimics and trends are provided for client displays. Additionally, calibration utility is provided for each parameter type to ensure correct conversion of voltage to engineering unit values.
The entire DAQ system can be divided into four subsections:
- Main section
- Main server clients
- Intermediate server
- Intermediate server clients
The main server and server clients are housed in the main operator room. They provide the operator with correct information regarding critical test parameters and status.
The main server acquires all the signal-conditioned physical channels according to the channel configuration that the operator selects before the test starts. The main server displays all 1024 channels during the run. There are four clients to the main server – called main server clients – that have dedicated displays to help the operator quickly identify variations in critical parameters of the engine during the run.
The entire set of acquired data is sent to the intermediate server without processing when it is acquired. The intermediate server clients display the data, MIMIC diagrams, or trends as desired by the user. It also converts the channels acquired according to the channel configuration in the main server and sends all the data to the intermediate server clients. The intermediate server has provision to store data if required and removes the overhead of transmitting acquired data to many clients from the main server. The number of intermediate server clients can be up to 15 and each client can be configured to a selected channel according to the requirements.
The most crucial aspect in the DAQ system is to provide a quick and efficient method to calibrate and configure all the channels before the tests start. We provided a method to assign the modules used to acquire specific parameters according to the requirements of the operator. This allowed for scalability in terms of accommodating additional modules in the future and making the engine run less dependant on hardware.
Before configuring software channels, an assignment must be made specifying the mapping of physical channels to the channels in the SCXI modules. The user only needs to reassign the physical and software channels when there is a change in the SCXI hardware. This ensures that a change in hardware does not affect the association of corresponding channels during acquisition.
Apart from physical channels there are also some computed channels called virtual channels. These channels are computed based on applying mathematical calculations on physical channels. The operator can assign virtual channels in the configuration screen by specifying the physical channel and the formula used to determine the calculated channel.
Along with acquiring all the channels and processing at a specified rate, the processed data needs to be transmitted to all the clients with minimum delay; hence, the TCP/IP program was optimized to transmit data as fast as possible and handle errors when needed by providing the user the correct run status. To test the communication between the main server and all the clients, a utility named data rigging is provided. Data rigging is done with information stored in the base configuration file.
During the engine run, data is displayed on multiple pages containing 40 channels each where the user can select the order of channels displayed. Provision is given to navigate through the 26 displayed pages and the operator can jump to any page, from any page. The data displayed is indicated in different colors depending on the allowable, caution, and warning limits. As the data displayed crosses each range, the color changes for that channel, which helps the operator quickly take necessary action such as aborting the run.
After the engine run is completed, the operator can replay previous test data. This is used for post-run analysis of the engine data. During replay, data is also transmitted to the main server clients. The operator can read data from any specified portion of run. The run data can be skipped in accordance to the number of frames selected by the operator and read backwards in time. The run can also be paused at any frame. Additionally, four types of reports can be generated for each run for any of the required channels.
The DAQ system provides simultaneous accessibility of engine run data for many departments and significantly reduced the time taken for the calibration of 1024 channels with an option to easily upgrade the system to include additional channels. In addition, significant time savings were achieved as custom reports are generated immediately upon completion of the run to allow the user to make changes to the engine before the next run.
Bipin M.. Kanth
Alie Arcade, No 19 7th Main Road