CIVL 315 - Lab 2 (Power House Design) Manual 2023 (1)

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Dec 6, 2023

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CIVL315 Lab 3 1 MEMO To: CIVL 315 Students From: Max Flowe, P.Eng. Subject: Powerhouse Design Project: 315-Lab-2 The board has accepted the contract and we would like to begin work on the Seeville, BC powerhouse as soon as possible. NEARCreek expects more of these projects in the future and would like to determine if experimental validation of each design is necessary or if theoretical calculations can be relied upon. The testing procedures for the scale model are attached along with the required deliverables for this project. Please forward a copy of your report in pdf format on the Canvas system within two weeks. Regards, Max Flowe Maxwell Q. Flowe, MASc, PEng Regional Manager (Hydraulics) NEARCreek Industries Ltd. Note: NEARCreek is not a real company. It was created for the purpose of CIVL315/316 courses.

CIVL315 Lab 3 2 Scope Jet Impact Measurements Use the apparatus equipment to develop relationships between flow, pressure head, velocity head, input and jet power, frictional losses. Use these relationships to make comments on their engineering applications Pelton Turbine Measurements Using the pelton wheel apparatus, develop relationships between bucket speed, jet speed, output power, efficiency, and turbine speed. Use these relationships to make comments on engineering applications. Theoretical and Experimental Results Calculate theoretical force and power in the impact and pelton wheel setups respectively and compare that to your measured results. Comment on any discrepancies and where error may be coming from. Engineering Design With your collected data, predict the turbine sizing for the Seeville Power project and make recommendations on how to reduce energy losses. Deliverables The consultant shall provide to Nearcreek a report that contains the following content and analysis: • Analysis of jet impact data in the context of momentum flux: a. Relationships between flow, pressure head, velocity head, input power, jet power and frictional losses. b. Relationship between measured and theoretical force. c. Recommendation on the use of momentum flux methods in engineering applications. • Analysis of performance of the Pelton turbine: a. Relationships between bucket speed, jet speed, output power, efficiency, and turbine speed. b. Recommendation on the use of theoretical methods in the estimation of pelton turbine performance. • Discussion of the transfer and conversion of energy throughout the entire system including the relative magnitudes of energy dissipations. • Mechanisms to reduce losses and increase efficiency in the full-scale generation system. • Predicted turbine sizing and output for the Seeville Power project with a peak flow of 8m 3 /s and 23.3m of head available.

CIVL315 Lab 3 3 Background Information Theoretical Force on a Flat Plate When a water jet strikes a plate and is deflected through an angle , the speed of the water is not appreciably changed, however the velocity of the water in the original direction is reduced from to . The force exerted on the plate is: ࠵? = ࠵?࠵?࠵?(1 − cos ࠵?) where F is the force exerted on the plate, is the density of water, Q is the flow rate, V is the velocity of the water in the jet relative to the plate. Pelton Turbine: Theoretical Power Relationships A Pelton wheel is an impulse turbine in which the wheel is rotated by the action of one or more jets striking specially curved vanes fixed to the periphery of the wheel. Pelton was the name of the man who first developed this type of turbine; he also set up a company in California to manufacture them. Recall that power is given by the following formula: ࠵? = ࠵?࠵?࠵?࠵? where P is power, Q is the flow rate , H is the total energy head in the flow. This power equation will be compared with the measured power output. The flow of water to the wheel is controlled by a needle valve. Since the needle valve is considered to be part of the turbine, the input power is calculated using the total head measured upstream of the needle valve. The velocity of water in the supply pipe to the needle valve is quite low, thus the total head can be approximated by the pressure head. The theoretical force developed at the rim of the Pelton wheel is ࠵? = ࠵?࠵?࠵?(࠵? − ࠵?)(1 − cos ࠵?) where u is the bucket velocity. Note that this is the same equation for the force developed on a flat plate, except that u = 0 in the flat plate case. The theoretical power developed by the wheel is ࠵? = ࠵?࠵?࠵?(࠵? − ࠵?)(1 − cos ࠵?) This theoretical power will be less than that given by ࠵?࠵?࠵?࠵? , and will also be compared with the measured power. Observe that if = 180º, the power developed is at a maximum. In practice, cannot be any θ V V cos θ ρ θ θ

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CIVL315 Lab 3 4 larger than about 170º to avoid having the water turning right round on itself and interfere with the jet. Assume that 170º is the deflection angle for the model Pelton wheel. Apparatus The apparatus consists of a self-contained water circulating system, which has a pump, a tank, valves and gauges. A needle valve provides a controlled jet, which can be directed either at a flat plate or the model Pelton wheel (Figures 1 and 2). The pitot tube on the flat plate apparatus allows for measurement of the velocity head of the jet. The static load cell allows the force on the plate to be measured. With the Pelton wheel in place the torque produced can be measured by a brake, which is a tensioned band acting on a rotating drum. The net force acting on the drum is the difference in band tension as measured by the applied weight and static load cell; and the torque is this force multiplied by the radius of the drum (see Figure 3 for the free body diagram). The power output is obtained by multiplying the torque by the angular velocity. ࠵? = 2࠵?࠵?࠵?(࠵? ! − ࠵? " ) where T 1 , T 2 are the spring scale readings, r is the brake drum radius, N is the rotating speed of the drum (rps) , and is the angular velocity of the wheel. Figure 1 - Schematic of the Flat Plate Apparatus 2 π N = ω

CIVL315 Lab 3 5 Figure 2 - Schematic of the Pelton Wheel Apparatus Figure 3 - Freebody diagram of the brake drum. T 2 T 1 mg Torque

CIVL315 Lab 3 6 Figure 4 - The needle valve and gauge. Figure 5 - Load cell and buffer tank.

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CIVL315 Lab 3 7 Procedure Equipment List • Reservoir/Pump assembly • Pelton wheel attachment • Force plate attachment • Box of weights • Tachometer and silver sticker on friction wheel • Hoist Safety Considerations • Closed-toed shoes are required in the Hydrotechnical Lab • Safety glasses are required in the Hydrotechnical Lab • Incorrect use of the apparatus may cause water hammer and burst pipes. • Friction wheel may be hot. • Do not use the hoist for objects heavier than the Pelton assembly. • The gasket between the Pelton wheel and the reservoir assembly can stick lift the whole assembly. • Overloading the hoist. • If the gasket sealing the Pelton wheel and the reservoir is sticking consult a technician • Perform whichever test Jet Impact or Pelton Wheel is already setup first when you arrive. • The display for the load cells has an error where the bottom level of the screen is shifted for some screens. • The friction of the belt varies depending on temperature so the stopping weight will vary. Jet Needle 1. Check that the reservoir is sufficiently full and clean. Very dirty water can damage the pressure gauge. 2. Check that the pump output valve is closed and turn on the pump. 3. Open the pump output valve completely. Needle valve pressure should read ~30 PSI. If it is not ~30 PSI, allow the system to run for 1-5 minutes to flush any air out of the system. Jet Impact Apparatus 4. Open the needle valve one turn. 5. Record the pressure in the needle valve gauge (Figure 4) 6. Close the drainage valve from the top reservoir.

CIVL315 Lab 3 8 7. Time how long it takes to fill the tank to measure flow from the needle valve. The measuring instrument along the side of the tank is already calibrated in ft 3 . 8. Open the upper drainage valve after the measurement to avoid overflow. 9. Lower the pitot tube into the stream to measure the velocity of the jet. It can be difficult to properly align the tube. The higher the water level in the buffer tank the better the alignment. If there is air in the tube leading up to the pressure gauge the reading will be inaccurate. The reading from the pitot tube should almost match the pressure reading of the needle gauge valve (Figure 4). 10. Remove the pitot tube from the jet. 11. Close the needle valve. 12. Place the calibration weight on the arm opposite the load cell. The load cell does not output accurate readings when it is slack. 13. Check that the alignment indicators line up on the force plate bearings. 14. On the Load cell output select “Measure” then “Impact”. If the output is not zero, select Exit -> Setup - >Yes -> Impact . 15. Press Measure -> Impact to check that the output value has been calibrated to 0. 16. Record the force on the load cell due to the jet. 17. Repeat steps 6-14 until you have data for 2,3,4,5 full turns of the needle valve. 18. Close the needle valve. 19. Close the pump output valve. 20. Turn off the pump. Switching Setup 21. Remove the pre tensioning weight from the load cell. 22. Unscrew the six nuts attaching the jet impact apparatus and the reservoir assembly. The jet assembly can be lifted by hand. For the Pelton wheel use the hoist. 23. Lift the Pelton wheel off the stand with the hoist. 24. Place removed assembly on blocks on the cabinet. Do not leave the assembly hanging from the crane while performing the lab. 25. Lower the Pelton wheel onto the bolts. Ensure the cups are pointing towards the jet. 26. Attach and secure the bolts with the wrench attached to the assembly.

CIVL315 Lab 3 9 Pelton Wheel 27. Add the round pre tensioning weight to the load cell. 28. On the Load cell output select “Measure” then “Torque”. If the output is not zero select Exit -> Setup - >Yes -> Torque . There is a glitch with the screen so you can’t see what each button does. Use trial and error. 29. Turn on the pump. 30. Open the pump outlet valve fully. Pressure at the needle valve should be approximately. 30 Psi. 31. Open the needle valve one and a half turns. You want to maximize the power output by varying RPM. You want the splashes to be perpendicular to the direction of travel to achieve maximum inertia transfer. So, the more perpendicular the splash is relative to the original jet direction the better. 32. With no weight attached to the rope record the wheel RPM with the tachometer. This can be done two ways: a. Point the tachometer at the reflective sticker on the friction wheel. Average this measurement over several times to check accuracy. b. Attach the rubber cone to the tachometer and set it in the centre of the friction wheel. Press and hold the “MEAS” button to record the RPMs. This can be averaged over multiple values to improve accuracy. 33. Add weight to the rope until the wheel stalls in 0.5 Kg increments. Record the weight and load cell reading for each incremental weight. If the wheel does not stall, contact a TA. 34. Remove 0.5 kg from the rope. 35. Record the weight on the rope. 36. Record the load cell reading. 37. Record the tachometer reading. 38. Repeat steps 29-32 until no weight is left on the rope. 39. Measure the radius of the friction wheel. 40. Measure the radius of the Pelton wheel. 41. Close the needle valve. 42. Close the pump outlet valve. 43. Turn off the pump.

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