The Challenge:

To develop a 1024 channel count data acquisition system that is used to monitor engine behavior during its development phase.

The Solution:

Use NI Signal Conditioning Extension for Instrumentation (SCXI) modules and Data acquisition (DAQ) card combined with the graphical features of LabVIEW to minimize development time and provide accurate result during testing gas turbine engine.

Introduction:

The data acquisition system consists of Server and multiple Client programs developed using NI Lab View 7.1. The Data Acquisition system is incorporated in the main server PC for acquisition of 1024 channels; PCI 6052E full-featured Data acquisition cards are used for multiplexed data acquisition. Acquired parameters include temperature, pressure, speed, flow, & vibration. The parameters are conditioned using SCXI signal conditioning modules. The acquired data is stored in 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 high channel data acquisition system. Also SCXI being a programmable signal conditioning system made the channel configuration very flexible for the operator by allowing future expandability with no additional programming and keeping it as simple as plugging in another module to include additional signals in future.

The data acquisition system has a main server, which has PCI-6052E DAQ card that is used to acquire data from sensors connected at different locations of the engine that is undergoing test. The acquired data is converted to corresponding engineering unit and displayed on the main server for the operator to view and take necessary action if the value is beyond allowable limit. The acquired data is also transmitted to main server clients and intermediate server clients.

Application:

The Gas turbine Engine has to be subjected to tests for studying the behavior of various parameters like temperature, pressure, speed, flow and vibration in various sections of the engine. This requires software that can quickly calibrate up to thousand channels and provide reliable data for correct analysis during and after the test.

The successful working of gas turbine engine involves many departments hence during the testing of the engine the test parameters should be available for all the departments without much delay. Hence the acquired data apart from being processed and displayed in the operator room also needs to be distributed simultaneously to various clients separated geographically. These departments (clients) will have their own set of channels that are of interest hence the clients are given option to configure channels according to their requirement before viewing the data. Also the clients will need pictorial representation of the parameter with respect to any section of the engine for better understanding hence mimics and trends are provided for client displays.

The Data acquisition system has additional utilities as explained below:

Calibration utility is provided for each parameter type to ensure correct conversion of voltage to Engineering Unit value. Open thermocouple detection for thermocouple channels helps in identifying open thermocouple channels.

System Design:

The Entire Data Acquisition system can be divided into four sub-sections. The pictorial representation of the entire system is shown in figure 1:

• MAIN SERVER
• MAIN SERVER CLIENTS
• INTERMEDIATE SERVER
• INTERMEDIATE SERVER CLIENT

The Main server and main server clients are housed in the main operator room thereby giving the operator correct information regarding critical test parameters and test status.

The main server acquires all the signal-conditioned physical channels according to the channel configuration selected by operator before start of test. The main server displays all the 1024 channels during the run. Also there is provision to acquire pressure signals from Scanivalve Electronic Pressure Scanners through Ethernet.

There are four clients to the main server, called as main server clients. The main server clients have dedicated displays that help the operator to quickly identify variations in critical parameters of the engine during the run.

The intermediate server has provision to display acquired data, MIMIC and trends of few parameters. The entire set of acquired data will be sent to the Intermediate server without processing as and when it is acquired. The intermediate server will convert the channels acquired according to the channel configuration in the main server and send all the data to the intermediate server clients. Intermediate server has provision to store data in the intermediate server if required. Intermediate server is used to remove the overhead of transmitting acquired data to many clients from main server.

The intermediate server clients will display data, MIMIC diagrams or trends as desired by the user. The number of intermediate server client can go up to 15. Each of the intermediate server clients can configure selected channel according to his or her requirement.

Software Implementation:

The most crucial aspect in the Data acquisition system was to provide a quick and efficient method to calibrate and configure all the channels before the start of run. We provided a method to assign the modules that are used to acquire specific parameters according to the requirement of the operator. This allowed for easy scalability in terms of accommodating additional modules in future and making engine run less dependant on hardware.

Before configuring software channels an assignment has to be made specifying the mapping of physical channel to the channels in the SCXI modules. This is a one-time configuration. The user has to reassign the physical and software channels only when there is any change in the SCXI hardware. This ensured that change in hardware will not effect the association of corresponding channels during acquisition. The software channel assignment front panel is shown in Figure 2.0.

Apart from physical channels there are some computed channels called as 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 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 status of run. To test the communication between the main server and all the clients a utility named as data rigging was provided. Data rigging is done with information stored in the base configuration file. The data rigging front panel is shown in Figure 3.0.

During the engine run, in the main server all the channel data are displayed. Data is displayed in multiple pages of 40 channels each; the user can select the order of channels to be displayed. Provision is given to navigate through the 26 pages of display. The operator can jump to any page from any page. The data displayed are indicated in different colors depending on allowable limit, caution limit and warning limit. As the data displayed crosses each range the color is changed for that channel which will help the operator to quickly take necessary action such as aborting the run.

After the Engine run is completed provision is given to replay previous test data. This is used for post run analysis of the engine data. During replay data will also be transmitted to main server clients. Provision is provided to read from any specified portion of run as desired by the operator. The run data can be skipped in accordance to the number of frames to be skipped selected by the operator. Provision is given to read the test data backwards in time and the run can be paused at any frame which is of interest to the operator

Report generation for existing test data is provided. Report is generated for channels that are required. There are four types of report that can be generated for each run.

Conclusion:

The Data acquisition system provided simultaneous accessibility of engine run data for many departments. The Data acquisition system significantly reduced time taken for calibration of 1024 channels with an option for easy upgradability to include additional channels in future. In addition significant time saving (in days) was achieved as custom reports are generated immediately on completion of the run to allow the user to make changes to the engine before the next run.