University of Tennessee at Chattanooga

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1 University of Tennessee at Chattanooga Operating Curve Engineering 39 By Red Team (Allen, Michael) Course: ENGR39 Section: 1 Date: 1/3/9 1 1//9

2 Instructor: Dr. Jim M. Henry 1//9

3 Introduction: In the filter wash station a control system is used to control the flow of water to three different filter washing nozzles. The pump controls the flow rate by varying motor speeds. For this experiment the pump is run at user specified speeds while recording flow data vs. time. To obtain the steady state operating curve (SSOC) several tests were run at 1% intervals. The data is then processed to determine the SSOC, time-averaged flow rate to the nozzles. The objective of this experiment is to determine the SSOC of the flow system to observe the system response to motor speed. This report has been divided into five sections; Background and Theory, Procedures, Results, Evaluation, Conclusions and Recommendations. The Background and Theory will set the stage for an understanding of the system and how it is used along with technical issues within the experiment. The Procedures section will cover step-by-step instructions to complete this experiment. The Results section covers the outcome of the experiments while the Evaluation section handles the analysis. The Conclusions and Recommendations section will overview the whole experiment to tie everything together. Following will be the appendix which will include any supporting documentation or graphs not directly used in the report. Background and Theory: This experiment has been created to provide an understanding of the relevance of a SSOC for use in system control. Electronic sensors provide data to the data acquisition system on the computer and a time-averaged value can be determined using excel spreadsheet software. The flow system schematic is shown in figure //9

4 Figure 1. Flow System Schematic To control the flow of water to the nozzles this system must complete three basic steps; measurement, decision and action. The flow rate transmitter (FT 31) acquires the signal from the computer and relays it to the flow rate recording control (FRC 31) mounted on the control board. These two devices take care of the measurement while the computer program handles the decision making. The flow control actuator (FCZ 31) operates the pump drive or inlet for the water flow completing the action stage of the control system. 1//9

5 The block diagram shows a basic breakdown of the flow system. Figure. Block Diagram of System The green arrow leading to the left side of the system represents the manipulating function that controls the input motor power shown as a percentage of capable power. The red portion of the diagram leading to the right represents the controlled function, this is the output flow which is directly related to motor speed. Procedure: 1. Open the LabVIEW program associated with constant power input.. Determine the step size you plan to use. 3. Enter in Input percentage you wish to operate experiment with.. Save txt document. 5. Repeat steps 3 and until you have reached 1% input. 6. Import each txt file to a separate excel spreadsheet to analyze the data. 7. Create a scatter-plot graph of the motor input and flow output vs. time. 8. Using the graph determine the position where enough time has elapsed to consider the system in steady state. 9. Use the excel function =AVERAGE(:) to compute the average of the output flow measurements in the steady state region. 5 1//9

6 1. Use the excel function =STDDEV(:) to compute the standard deviation of the output flow measurements in the steady state region. 11. Compile the average values and input percentages into one spreadsheet and create a scatter-plot graph relating input percentage to output flow. 1. This graph represents the SSOC where the function is continuous. Determine which area of the graph is considered steady state for the system. Results: With the experiments completed and the data ready to be analyzed we import that data into excel for further calculation. A graph comparing Input and Output with respect to time lets us determine the steady state region for a given motor operation speed. This sample graph in Figure 3 illustrates what indicates a steady state region. Input (75%) and Output vs Time Inpu Flow Average Flow Rate = lb/min 1 Standard Deviation =..3 lb/min CBD 9//9 Figure 3. Input Percentage and with respect to time at 75% motor power. 6 1//9

7 Once the steady state region has been designated it is possible to calculate the average output flow rate for the specific input. For this instance (75%) the time interval from 1 to 1 seconds is considered steady state. All data before the steady state region can be disregarded for this experiment due to its unsteady response. Thus we take the flow rates between 1 to 1 seconds and compute the average and standard deviation, which can be seen on figure 3. Eight separate experiments were run starting at 35% increasing by 1% up to 1%. Experiments under 35% were rejected due to minimal flow rate output. The data and graphs for all of these experiments can be found in the appendix. Upon completion of all experiments all averages and standard deviations were compiled into a single sheet. This data can also be found in the appendix. A plot comparing Motor input percentage and Flow Rate was constructed to view the steady state operation. Operating Curve for the Flow System 16 Flow Rate y = 16.5x R = % 5% 55% 65% 75% 85% 95% Input Flow Rate We will use this range since it appears to be continuous. CBD 9//9 Figure. Operating Curve for the Flow System. 7 1//9

8 The SSOC for this system appears to be unstable below 55% perhaps 5% at best. This information leads us to resolve that the steady state operating region for this system is from 55% to 1% with an output flow rate range from 8 to 15 lb/min. Using a linear fit trend line we find that the SSOC for this system is linear. 8 1//9

9 Discussion: The results from these experiments indicate that at a constant pump speed this flow system has a linear steady state operating curve from 55% to 1%. The range would be considered the operating range of the system because of its predictability. For steady state analysis we must discard data at the start-up of the test due to inconsistencies. Since the highest standard deviation is 3.5% we can assume that the mean values are adequate representations of the total data sets. Conclusion and Recommendation: The purpose of this experimentation was to determine the steady state operating curve by running several experiments a different constant input power levels. Using LabVIEW and other data acquisition hardware we were able to run experiments to determine the SSOC. The results showed that the experiments provided accurate data and helped determine the optimum operating range for this system. Shown by the SSOC we know that the optimal operating range is 55% to 1%. However, inconsistencies have to be weeded out during startup of each evaluation. It would be unwise to operate this system out of its operation range due to inconsistencies and poor efficiency. This system can now be used with confidence that it is being used at most favorable conditions. 9 1//9

10 APPENDIX Figure 1. Flow System Schematic Figure. Block Diagram of System 1 1//9

11 Input (75%) and Output vs Time Inpu Flow Average Flow Rate = lb/min 1 Standard Deviation =..3 lb/min CBD 9//9 Figure 3. Input Percentage and with respect to time at 75% motor power. Operating Curve for the Flow System 16 Flow Rate y = 16.5x R =.9998 Flow Rate We will use this range since it appears to be continuous. 35% 5% 55% 65% 75% 85% 95% Input CBD 9//9 Figure. Operating Curve for the Flow System. 11 1//9

12 Input (35%) and Output vs Time Input Average Flow Rate = 6.66 lb/min Standard Deviation =.3 lb/min Flow Figure 5. Input Percentage and with respect to time at 35% motor power CBD 9//9 Input (5%) and Output vs Time Input 1 Average Flow Rate = 3.59 lb/min Standard Deviation =.9 lb/min Figure 6. Input Percentage and with respect to time at 5% motor power. 1 Flow CBD 9//9 1//9

13 Input (55%) and Output vs Time Inpu Flow 1 Average Flow Rate = 7.9 lb/min 1 Standard Deviation =.9 lb/min CBD 9//9 Figure 7. Input Percentage and with respect to time at 55% motor power. Input (65%) and Output vs Time Input Flow Average Flow Rate = 9.8 lb/min 1 Standard Deviation =..35 lb/min CBD 9//9 Figure 8. Input Percentage and with respect to time at 65% motor power. 13 1//9

14 Input (95%) and Output vs Time Inpu Average Flow Rate = 1. lb/min Standard Deviation =.33 lb/min Flow Figure 9. Input Percentage and with respect to time at 85% motor power CBD 9//9 Input (85%) and Output vs Time Input Average Flow Rate = 1.83 lb/min Standard Deviation =.3 lb/min Flow Figure 1. Input Percentage and with respect to time at 95% motor power CBD 9//9 1 1//9

15 Input (1%) vs Input Average Flow Rate = lb/min Standard Deviation =.3 lb/min Flow Rate CBD 9//9 Figure 11. Input Percentage and with respect to time at 1% motor power //9

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