Laboratory Report on
Axial Flow Pump Test
By
Walson Onyemobi Student No: 08836256 Module: CN225, Hydraulics Course: MEng, Civil Engineering, Level 2
Date of Experiment: 7th March 2011
Submission Deadline: 20th March 2011
Table of Contents: 1
INTRODUTION .................................................................................................... 3
2
MATERIALS AND METHOD ............................................................................... 4 2.1
3
Method ......................................................................................................... 4
THEORY AND RESULTS.................................................................................... 5 3.1
Theoretical Analysis ...................................................................................... 5
3.2
Analysis of Results ........................................................................................ 6
4
SOURCES OF ERROR ..................................................................................... 11
5
CONCLUSION ................................................................................................... 12
6
REFERENCES .................................................................................................. 12
Table of Figures: Figure 1: Graph of Hm (m) Against Q (m3/s) .............................................................. 9 Figure 2: Graph of Efficiency (%) Vs Discharge (m3/s)............................................... 9 Figure 3: Graph of PH (Joules) against Q (m3/s)......................................................... 9 Figure 4: Graph of H1200 (Joules) against Q1200 (m3/s) ............................................. 11 Figure 5: Graph of Q (m3/s) against P1200 (joules) .................................................... 11
Table of Tables Table 1: Table 1: Details of the Experimental Values Obtained For Different Pump Speeds.........................................................................................................................6 Table 2: Total Head at N = 1200rpm...........................................................................7 Table 3: Total Head at N = 1300rpm...........................................................................7 Table 4: Total Head at N = 1400rpm...........................................................................7 Table 3: Discharge Values across the Pipe for the Three Different Pump Speeds....8 Table 4: Values of PH, PE, and η for each of the Three Pump Speed........................9 Table 5: values of head, discharge, and hydraulic power under a 1200rpm base speed.........................................................................................................................11
1 INTRODUTION The concept of axial flow pump with respect to its performance, uses and industrial applications as opposed to centrifugal pump is quit enormous. Due to the fact that axial machines have more limited suction capacity than centrifugal pumps [3], it therefore follows that the flow generated around the section of axial machine blade becomes very sensitive to low pressure. Hence, a low intake of pressure in an axial flow pump results to flow separation and consequent loss of energy. In order to determine the flow of fluid in an axial pump which is dependent on the fluid pressure, electrical power, head across the pump etc an characteristics performance curves will be constructed,thus,the aim of the experiment; to construct the characteristics curves for an axial flow pump test.
2 MATERIALS AND METHOD The following materials were provided for use in the experiment. 1. 2. 3. 4.
415 volts of an AC motor with a maximum speed of 1400rpm Motor speedometer, measured in rev/min Current meter (Amps) consumed by the motor. Sets of manometers and a dall tube: used to measure pressure (in mm Hg) and the discharge (Q) through the pipe respectively. 5. Measuring tape – used to measure the downstream distances (Z 1 and Z2).
2.1 Method The following steps were carried out during the experiment. Step 1 – the downstream and upstream distances (Z1 and Z2) were measured and recorded. Step 2 – the valves connected from the manometers to the main pipe were fully closed. The gate valve fully opened. Step 3 – the pump was started with an increased sped of 1100rpm and the valves opened with the gate valve now closed. Step 4 – after reading manometer #2, the gate valve was now fully reopened and adjusted so that manometer #2 is reduced by ~ 10mm. Step 5 – the pump control was adjusted to maintain a constant speed of 1200rpm. Step 6 – the current meter and manometers readings were measured and recorded. Step 7 – the experiment was repeated from step 4 for two different pump speeds (N = 1300 & 1400 rpm’s).Table 1 shows the experimental data obtained.
3
THEORY AND RESULTS
3.1 Theoretical Analysis An axial flow pump is a type of pump that consists of a propeller, which in some instances can be driven directly by a sealed motor in a pipe (as in the case of CN225 lab) or mounted to the pipe from the outside or by a right-angle drive shaft that pierces the pipe. Axial pump always follow an axial type of flow (i.e. the flow is longitudinal) thereby producing the smallest dimensions in comparison to other pump types. This small dimensions results to the development of low head and steeply descending efficiency curve as illustrated in figure 2. In other to determine the efficiency of the pump, the power output (hydraulic power PH) and input (electrical power PE) needs to be evaluated. The efficiency (n) of the pump is given by the relation;
⁄ Where P (hydraulic power) = (in Joules), and P (electrical power) = Amps × H
E
Volts in watts. The discharge (Q) is given by Where
⁄
are the manometer readings (in mm).
The total hydraulic head (Hm) across the pump can be calculated knowing the pressure upstream and downstream of the pump. The relationship that governs the total head is expressed below;
( ) Using the information above, the characteristics performance curve for the axial flow pump can be constructed. A base speed of 1200rpm is used to construct the graph of the relations in equations 4,5 and 6.This is to compare the results when the pump is operating at different speeds.
⁄ ⁄ ⁄ 6 Given equations 1,2 and 3 above, the relationships between the total head (HM),Hydraulic power (PH),efficiency (η) and the discharge (Q) can be established graphically, with an iso-efficiency line drown on the H M-Q graph showing how efficient or the level of performance of the axial flow.N is the pump operating speeds. Details of the calculations and graphs are given in the ‘results analysis’ section of this report (page 5).
3.2 Analysis of Results Given that the total head (Hm) across the pump is related to the pressure supplied across the pipe and the manometers by the equation 3, page 4, where Z1 and Z2 are the downstream distances, Rright and Rleft are the two manometer readings at a given pump speed (N).Rho ( and ) are densities of water and mercury respectively
given as 1000kg/m 3 & 13600kg/m3.
Table 1, below gives the experimental values obtained in the lab. Z1 = 1.46m Reading
Z2 = 1.58m Current meter(Amps)
1 2 3 4 5 6 7 8 9 10 11
16 17 18 18.5 19 18 17 17.5 17 18 29.5
1 2 3 4 5 6 7 8 9 10 11
16.5 17.5 18.5 19 20 21.5 22 21 19.5 21 28
1 2 3 4 5 6 7 8
18.5 21 22 24 24.5 25 24.5 23.5
R0 = 9mm Manometer #1 (m)
Rleft Rright Pump Speed 1200rpm 0.34 0.26 0.32 0.28 0.31 0.29 0.30 0.30 0.29 0.31 0.27 0.34 0.26 0.34 0.26 0.34 0.26 0.34 0.24 0.36 0.11 0.48 Pump Speed 1300rpm 0.36 0.235 0.35 0.25 0.29 0.28 0.26 0.31 0.25 0.34 0.24 0.35 0.24 0.36 0.24 0.36 0.22 0.38 0.22 0.48 0.11 0.08 Pump Speed 1400rpm 0.36 0.24 0.33 0.27 0.30 0.29 0.25 0.34 0.24 0.35 0.32 0.37 0.22 0.38 0.22 0.39
Manometer #2 (Ri)in mm.
155 140 125 110 95 80 65 50 35 20 10 210 190 170 150 130 110 90 70 50 30 10 240 216 192 168 144 120 98 72
9 23 0.21 0.43 48 10 27 0.16 0.54 24 11 30 0.05 0.05 10 Table 6: Details of the Experimental Values Obtained For Different Pump Speeds
From equation 3 above, the total head (Hm) across the pump for each manometer readings (Rright & Rleft) and at different pump speeds is calculated below (table 2); Thus; for pump speed of 1200rpm, substituting relevant values in the equation,
H = . m
Therefore, following the calculations above, different Hm’s can be obtained for each N and at different manometer readings.Z1, Z2, and are all constant throughout.
Reading Hm (m)
1 2.032
2 2.536
Pump Speed (N) = 1200rpm 3 4 5 6 7 2.788 3.04 3.292 3.922 4.048
8 4.048
9 4.048
10 4.552
11 7.702
Table 7: Total Head at N = 1200rpm.
Reading Hm (m)
1 1.465
2 1.780
Pump Speed (N) = 1300rpm 3 4 5 6 7 2.914 3.670 4.174 4.426 4.552
8 4.552
9 5.056
10 6.316
11 7.450
8 5.182
9 5.308
10 6.442
11 9.214
Table 8: Total Head at N = 1300rpm Reading Hm (m)
1 1.528
2 2.284
Pump Speed (N) = 1400rpm 3 4 5 6 7 2.914 4.174 4.426 3.670 5.056
Table 9: Total Head at N = 1400rpm Tables 2, 3 & 4 above shows the total heads across the pump at different pump operating speeds. This implies that as the pump operates (delivers fluid) at a constant speeds of 1200,1300 & 1400rpm’s there is an increase in the total head across the pump, thereby resulting to a loss in the hydraulic energy. From equation 2 above, the discharge across the p ump for each pump speed can be computed.
⁄. Where R and R are the manometer #2 readings and its initial reading respectively .e.g. √ ⁄ i
0
Reading Q (m3/s)
1 0.160
Reading Q(m3/s)
1 0.1879
Reading Q(m3/s)
1 0.2014
Pump Speed (N) = 1200rpm 2 3 4 5 6 0.1512 0.1 0.13 0.12 0.11 43 3 3 2 Pump Speed (N) = 1300rpm 2 3 4 5 6 0.17 0.16 0.15 0.14 0.13 83 81 73 58 32 Pump Speed (N) = 1400rpm 2 3 4 5 6 0.19 0.17 0.16 0.15 0.13 06 92 71 40 96
7 0.09 9
8 0.08 48
9 0.06 76
10 0.04 39
11 0.01325
7 0.11 93
8 0.10 35
9 0.08 48
10 0.06 07
11 0.01325
7 0.12 5
8 0.10 52
9 0.08 27
10 0.05 13
11 0.01325
Table 10: Discharge Values across the Pipe for the Three Different Pump Speeds The amount of hydraulic power (PH) (in joules), electrical power (PE) in watts and the efficiency (η) generated by the pump at each operating speed is given by the relations and , PE = Amps x Volts, where and g are 3 2 density (1000kg/m ) and gravity (9.81m/s ) respectively. Q and Hm values for each pump speed are given in tables 5 and 4 respectively, No. of Volts = 415. Amps values are given in table 1, while PH and PE values are given in table 6
⁄
Readings PH(joules) PE(watts)
1 3189 6640
Pump Speed (N) 2 3 3762 3911 7055 7474
η (%)
48
53.3
PH(joules) PE(watts)
2700 6848
η (%)
39.4
PH(joules)
= 1200rpm 4 5 3966 4263 7719 7885
6 4309 7470
7 3931 7055
8 3367 7263
9 2684 7055
10 1960 7470
57.7
55.7
46.4
38.1
26.2
5783 8923
5327 9130
4622 8715
4702 8093
3761 8715
64.8
58.3
53.0
51.9
43.2
3019
42.9 62.6 71.8 71.9 Pump Speed (N) = 1400rpm 4271 5123 6842 6687
968.4 1162 0 8.33
5026
6200
5348
4306
3242
1198
PE(watts)
7678
8715
9130
9960
10165
10375
10168
9753
9545
11205
η (%)
39.3
49.0
56.1
68.7
65.8
48.4
60.9
54.8
45.1
28.9
1245 0 9.62
52.3 51.4 54.1 Pump Speed (N) = 1300rpm 3113 4805 5663 5970 7263 7678 7885 8300
Table 11: Values of PH, PE, and η for each of the Three Pump Speed The values in tables 5 and 6 implies that at each pump operating speed, the hydraulics power, electrical power and the efficiency of the pump follows a variable sequence. That is, the values increase decreases and latter increases. This is replicated in the graphical relationships between these parameters. The pump speeds also affects the flow rate.
11 1001 1224 3 8.18
η (%) Vs Q (m3/s)
80
η (%)1200 η (%)1300
70
) 60 % ( 50 y c n40 e i c30 i f f E20
η (%)1400
0.112
10
0.143
0.16
0.084
0 0
0.02
0.04
0.06
0.08 0.0860.1 Q (m3/s)
0.118
0.12
0.14
0.16
0.18
Figure 1: Graph of Efficiency (%) Vs Discharge (m3/s)
Hm Vs Q
Hm1200
10 9
iso - efficiency lines
8
Hm1300
7
) 6 m ( 5
Hm1400
1400rpm
m
H4 3
1300rpm
1200rpm
2 1 0 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
(m3/s)
Q Figure 3: Graph of Hm (m) Against Q (m3/s) PH Vs Q
PH1200
8000 PH1300
7000
PH1400
6000
) s5000 e l u4000 o j ( H3000
P
2000 1000 0 0
0.02
0.04
0.06
0.08
0.1
0.12
Q (m3/s) Figure 23: Graph of PH (Joules) against Q (m3/s)
0.14
0.16
0.18
Figures 1, 2 and 3 above shows the characteristics performance curve of the pump for the Head (Hm), Hydraulic power (P H), and Efficiency ( η (%)) against the Discharge (Q m3/s) for each of the three pump speeds. The curve at each figure does not follow a consistent format, as it varied without a regular rythm.This may be due to experimental error. It can be shown that axial pumps provide higher head but lower discharge. This factor can thus affect the use of axial pumps in some application. Figure 2 explains the effect of a decreasing flow rate as it increases the momentum force of the motor. The efficiency on the pump increases until a point before starting to decrease. The iso – efficiency lines shows the efficiency of the pump at a given pump speeds.
H1200
1.248
1.517
H1200
1.123
1.678
Q1200
0.160
0.1512
Q1200
0.173
0.164
For N = 1200rpm,H m at 1200rpm (table 2) 2.788 3.04 3.292 3.922 4.048 For N = 1300rpm,Hm at 1300rpm (table 2) 2.483 3.127 3.557 3.771 3.879 For N = 1400rpm,Hm at 1400rpm (table 2) 2.141 3.067 3.252 2.696 3.715 For N = 1200rpm,Q at 1200rpm (table 3) 0.143 0.133 0.123 0.112 0.099 For N = 1300rpm,Q at 1300rpm (table 3) 0.155 0.145 0.135 0.123 0.11
0.163
For N = 1400rpm,Q at 1400rpm (table 3) 0.154 0.143 0.132 0.119 0.107
H1200
Q1200
2.032
0.173
2.536
P1200
3189
3762
P1200
2124
2448
For N = 1200rpm,P H at 1200rpm (table 4) 3911 3966 4263 4309 3931 For N = 1300rpm,P H at 1300rpm (table 4) 3779 4454 4696 4548 4190
2690
For N = 1400rpm,P H at 1400rpm (table 4) 3226 4309 4211 3165 3904
P1200
1901
4.048
4.048
4.552
7.702
3.879
4.308
5.382
6.348
3.809
3.899
4.733
6.769
0.0848
0.0676
0.0439
0.01325
0.095
0.078
0.056
0.0122
0.091
0.071
0.044
0.011
3367
2684
1960
1001
3635
3698
2958
761.7
3368
2712
2042
609.8
Table 12: values of head, discharge, and hydraulic power under a 1200rpm base speed .
H Vs Q 9 8 H1200
7
H1300
6
) 5 m ( H4
H1400
3 2 1 0 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
(m3/s)
Q Figure 4: Graph of H1200 (Joules) against Q1200 (m3/s) P Vs Q 5000 4500 4000 3500 3000 S '
2500
P
2000 1500
P1200
1000
P1300
500
P1400
0 0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Q (m3/s) Figure 5: Graph of Q (m3/s) against P1200 (joules) Figures 4 and 5 show the respective relations between the Head and the power output against discharge when the pump is operating at a constant speed of 1200rpm.There are not much differences between performance curves of the pump when the pump is operating at different speeds (figs.1, 2, 3 ) and when set at a base speed of 1200rpm (4, 5). The formal depicts the irregularity of the flow at each head while the later shows a near constant straight line and a varying flow rate as the momentum of the motor increases.
4 SOURCES OF ERROR Due to the complexity of the experiment, the probability that errors are likely to be made/occur are highly likely, especially at the calculation part of the report. Sources of errors include reading the manometer (parallax), stiffness of the gate valve thereby slowing the process, sudden stoppage of the AC motor due to overheating.
But that notwithstanding, accurate measures where applied during the experiment, and the results gotten as well as materials and method are still valid and the report a resourceful piece of material.
5 CONCLUSION The experiment was a success and the results gotten fairly ok because they are within the range of the experimental expectation. From table 1, the results for the manometers readings and the currents tends to follow a similar pattern of varying values for the three pump speeds. The same scenario follows for the hydraulic heads of the pump at each pump speed. As the speed increases from 1200 rpm to 1400rpm,the values of the head (Hm),manometer readings ,discharge, hydraulic power ,efficiency ,electrical power and all other parameters involved increases initially, then maintains a near constant value at the middle then finally decreases. The plots obtained for the pump performance curves was as result of the experimental values, which was quite (curve) unexpected due to the irregularity of the values obtained for the head and the discharge. The efficiency of the pump tends to increase as the speed increases (fig.3). Hence, in general the performance of the pump was fairly ok with an average percent (50-60%) of efficiency.
6
REFERENCES 1) Laboratory Report Instruction Sheet/Manual By Dr.Kaiming She 2) A.J Chadwick et al : Hydraulics in Civil and Environmental Engineering, 4th Edition, [P.205, 209], Spon Press, 2005. 3) http://www.ahm531.com/lab-reports/hydraulicslab/reports/1/Axial%20pumps.pdf accessed 20/03/11
