Hydraulic Laboratory Experimient - Lab Report Example

Hydraulics By Table of Contents Objectives 3 Introduction 3 Experimental 5 Gradually Varied Flow 5 Performance Teston a Centrifugal Pump 6 Sluice Gate – Hydraulic Jump 6 Tabulated observations 7 Performance Test on a Centrifugal Pump 7 Gradually Varied Flow 9 Rapid Varied Flow 9 Hydraulics Objectives The objectives of the experiment were: To establish a drawdown curve in the channel, record variation in depth along and compare the curve with the predicted by gradually varied flow thory To establish the relationship between head, discharge, speed, power, efficiency, for a single stage double centrifugal pump. To confirm the theory relating to the flow under sluice gates and formation of a Rapid varied flow in a rectangular channel Introduction The flow in open channel is usually non-uniform as a result of many factors. This includes; 1. Man-made obstruction as a result of structures bridge piers, dams, and other various hydraulic structures. 2. Existence of irregularities in channel cross-section 3. Unsteadiness due to of caused by dynamic control structures. Production of uniform flow is impossible even in the laboratory since the length of the flume is not usually sufficient enough to establish uniform flow regime. Non uniform flow varies with spatial positions in the open channel flow. Occurrence of non-uniform flow over a relatively short distance results in rapid variation of flow velocity and depth. From this, one can conclude that rate of depth change and velocity with distance is very large. This flow is referred to as hydraulic jump also known as rapidly varied flow. Rapidly Varied flow is characterized by neglecting skin friction effects and to solve this, the mass conservation law and momentum equation can be applied. In rapidly varied flow, momentum is conserved but energy is not conserved. Conversely, gradually varied flow skin friction resistance has significant influence on the surface profiles. To quantitatively describe Gradually Varied Flow integration of either equations of continuity and momentum and energy are required. In most cases, non-uniform flow in open channels represents combination of both gradually varied flow and rapidly varied flow. In a rapidly varied flow, the rate of flow changes from supercritical with high speed to subcritical with low speed. The definition of these regimes is as illustrated in the equations blow. Subcritical flow occurs when Critical flow occurs when Supercritical flow which occurs when Where Vw refers to wave speed, Fr is the Froude’s number. In this flow, there is considerable loss of energy. The figure below shows the general pattern in which the definition depths, velocities, and the velocity profile. To analyse this, application of momentum and continuity equation is done to control volume around the hydraulic jump. This experiment is aimed at studying both Rapidly Varied Flow and gradually varied flow. Also, theoretical values will be compared with experimentally measured surfaces profiles Experimental Gradually Varied Flow The channel was set to a gradient of 0.2% i.e. 1 in 500 by adjusted the jack at the end of the channel. The pump was then switched on and water admitted into the channel by operation of the valve. The flow rate was then adjusted to its maximum and recorded using the measuring tank. The conditions were then allowed to settle and the depth of the flow at intervals of 0.2 at a length of 3.6 m from the outfall end of the channel recorded. Performance Test on a Centrifugal Pump The discharge valve was fully opened and the motor switched on. The motor speed was then set to 2800 revs per second using the motor speed control switch and the portable tachometer. The following were recorded: suction pressure head, delivery pressure head, torque, water level over the V-notch using the depth gauge. The flow rate was then reduced in stages by adjusting the discharge valve at each stage and recording the flow rate. The procedure was then repeated again with a speed of 1800 revolutions per minute. Sluice Gate – Hydraulic Jump The sluice gate was fixed in position using a suitable opening with the channel bed horizontal. The required number of blocks was then placed at the upstream end of the channel. The water was admitted into the channel and the flow rate adjusted to give a hydraulic jump just downstream of the sluice. The flow was then allowed to steady and the depths y1, y2, y3, recorded Tabulated observations Performance Test on a Centrifugal Pump 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Static Torque Ts (Nm) Recorded Torque Tr (Nm) Actual Torque TA (Nm) TR - Ts Revs Per Min Revs per Sec N Suction Pressure Head Ps (m) - Discharge pressure Head Pd (m) + Total Head H (m) Pd - Ps Head Over Notch (mm) Flow Ql liters /min Flow Qm m3/sec x10-4 Input Power Pi (watts) 2piNTa Output power Po (watts) pgQmH Efficiency (%) Po/Pi x100 4 0.58 -3.42 2800 46.7 -1.8 14 15.8 90 311 0.01 -319 0.08 -2611 4 0.58 -3.42 2795 46.6 -1 18 19 80 374 0.01 -319 0.12 -3769 4 0.5 -3.5 2790 46.5 -0.2 21 21.2 70 417 0.01 -326 0.15 -4794 4 0.47 -3.53 2799 46.7 0 22 22 60 433 0.01 -329 0.16 -5223 4 4.4 0.4 2799 46.7 0 22 22 50 433 0.01 37.3 0.16 592 4 4.1 0.1 2808 46.8 0 22 22 40 433 0.01 9.36 0.16 148 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Static Torque Ts(NM) Recorded Torque Tr NM) Actual Torque Ta(Nm) TR - Ts Revs Per Min Revs per Sec N Suction Pressure Head Ps (m) Discharge Pressure head Pd (m) + Total Head H (m) Pd - Ps Head Over notch (mm) Flow QL Liters per min Flow Qm m3/sec x10-4 Input power Pl (watts) 2piNTA Output Power Po (watts) pgQmH Efficiency n (%) Po/P1 x100 3.4 4.3 0.9 1.8 0.03 -1 4 5 90 81 9.91 0.17 487.80 2877 3.4 4.1 0.7 1802 30.03 -0.2 7 7.2 80 70 11.90 132.11 842.92 6.38 3.4 3.9 0.5 1804 30.07 0 8 8 70 60 12.54 94.47 987.24 10.45 3.4 3.7 0.3 1808 30.13 0 8.7 8.7 60 50 13.08 56.81 1119.61 19.71 3.4 3.6 0.2 1801 30.02 0 8.7 8.7 50 40 13.08 37.72 1119.61 29.68 3.4 3.5 0.1 1801 30.02 0 8.7 8.7 40 25 13.08 18.86 1119.61 59.36                             The pump is efficient when operating at a speed of 2800 revolutions per second. This because ths efficiency at 2800 revs per second is optimum as compared to the rvolutions when it is punping at a rate of 1800 revolutions per second. Gradually Varied Flow Distance Depth 0 37.5 0.2 42.5 0.4 43.4 0.6 49.5 0.8 45.5 1.0 47 1.2 48 1.4 48.5 1.6 50 1.8 51 2.0 52 2.2 53 2.4 53 2.6 53 2.8 53 3.0 53 3.2 53 3.4 53 3.6 53 3.8 55 Rapid Varied Flow Rate of flow y1 y2 y3 194.5 12.0 65.5 =24 The measured values are does not correspond to the calculated values. This is as a result of both major and minor losses. The minor losses include losses due to entry and exit, losses due to the valves and fixes. The major losses are the fictional losses. Read More