On the Optimum Utilization of Water Hammer

Azoury, P. H.; Baasiri, M.; Najm, Habib N.

doi:10.1243/pime_proc_1988_202_035_02

Cited by 4 publications

(6 citation statements)

References 3 publications

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“…The following data were employed in the set-up: In the absence of experimental data for the exponent y related to the valve schedule, a value of 0.5 was chosen as being typical for quick-closing valves. (It has been shown by Azoury et al [29] that the optimum waterhammer wave strength is not overly sensitive to the valve schedule.) The value of was taken as 0.23, an average of the estimated experimental values [29].…”

Section: Model Validationmentioning

confidence: 95%

“…A numerical model for the hydraulic ram was introduced by Chiang and Seireg [28], which suffers, however, from too simplified an approach. Azoury et al [29] used the MOC to analyse, for a single pipeline discharging into the atmosphere, the effects of the valve closure schedule and the drive pipe length on the optimum water-hammer strength. A model that is somewhat more sophisticated than that of Chiang and Seireg was introduced by Verspuy and Tijsseling [30] and compared with experimental data on pressure heads generated in various sections of the ram.…”

Section: Review Of Previous Workmentioning

confidence: 99%

“…For reverse flow, the coefficient is set to unity. The reference velocity, u 0 , can be calculated as follows [29]:…”

Section: Reservoir At the Upstream End Of The Drive Pipementioning

confidence: 99%

“…(It has been shown by Azoury et al [29] that the optimum waterhammer wave strength is not overly sensitive to the valve schedule.) The value of was taken as 0.23, an average of the estimated experimental values [29]. The impulse valve closure time is about 0.1 s. The calculated wave speed is 1359 m/s, while T cl,IV =8.…”

Section: Model Validationmentioning

confidence: 99%

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Hydraulic ram analysis: a new look at an old problem

Najm

Azoury

Piasecki

1999

Proceedings of the Institution of Mechanical Engineers, Part A:

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The discretized method of characteristics was used to develop a new numerical model for the analysis of the wave processes in the hydraulic ram. The model encompasses all parts of the device including, for the first time, the air chamber and the delivery pipe. This in turn allows a comprehensive study of the unsteady flows in the unit as the air chamber extensively interacts with the supply side of the ram. The program accounts for all possible flow states of the ram, i.e. with impulse and discharge valves closed, with both valves open and with either of the valves closed or open. The state of the partially or fully open discharge valve requires extensive and careful treatment of all physical phenomena involved, namely the transient boundary conditions, relevant to the air chamber and its connection to the drive pipe. The treatment is for the special case of constant sonic velocity in each of the ram pipes. The numerical model was validated against experimental data obtained from various test set-ups. Comparing the velocity and pressure head variations from numerical and experimental tests at selected points along the ram supply pipe performed the most stringent test. Excellent agreement was shown to exist, validating the analytical approach.

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Section: Model Validationmentioning

confidence: 95%

Section: Review Of Previous Workmentioning

confidence: 99%

“…For reverse flow, the coefficient is set to unity. The reference velocity, u 0 , can be calculated as follows [29]:…”

Section: Reservoir At the Upstream End Of The Drive Pipementioning

confidence: 99%

Section: Model Validationmentioning

confidence: 99%

See 2 more Smart Citations

Hydraulic ram analysis: a new look at an old problem

Najm

Azoury

Piasecki

1999

Proceedings of the Institution of Mechanical Engineers, Part A:

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show abstract

“…Azoury et al (17) have demonstrated that ram performance is affected by a finite valve opening time only if this is comparable with the time taken by the pressure wave during pumping to travel up and down the drive pipe. With the rapidly operating valves typically found in practical rams, it is found that modifications to the theory would only be necessary for very short drive pipes ( < 5 m).…”

Section: Theorymentioning

confidence: 99%

Design of Hydraulic Ram Pump Systems

Young

1995

Proceedings of the Institution of Mechanical Engineers, Part A:

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Automatic hydraulic ram pumps are environmentally friendly devices using a renewable energy resource to pump water for domestic or agricultural use. Since being superseded by pumps using electrical or fossil fuel energy nearly a century ago, they are now coming back into favour in many parts of the developing world. I n the past, hydraulic ram pumps have been designed by rules-of-thumb having limited scientific basis. On-site adjustment has been used in the hope of rectifying the inevitable shortcomings of this process and ideal performance is rarely achieved. The present proposal for optimum design allows relevant system parameters (including the beat frequency) to be selected prior to installation. The paper shows how a ram pump system may be designed using two simple equations containing empirical factors dependent upon ram size, delivery head, material and wall thickness of the drive pipe and the configuration of the impulse valve. The design method is illustrated with reference to a number of existing tests. New experimental results for a 53 mm ram with Jive different impulse vdve strokes are also presented.Key words: automatic hydraulic ram pump design, empirical factors, effect of valve stroke, renewable energy NOTATION velocity ratio = uc/uo empirical factor in equation (5) (m-3) cross-sectional area of the drive pipe (m') valve flow area (m') empirical factor in equation (6) (s/m3) velocity of sound (m/s) discharge coefficient drive pipe diameter (m) friction factor acceleration due to gravity (9.8 m/s') delivery head (m) impulse valve head loss at closure (m) maximum delivery head (m) steady state head loss across impulse valve (m) supply head (m) total head prior to impulse valve closure (m) static head to close impulse valve (m) system loss coefficient constant (m/s) constant (s) length of drive pipe (m) impulse valve loss coefficient beat frequency (Hz) quantity delivered (m3/s) capacity of source (m3/s) steady state flow through impulse valve (m3/s) quantity wasted (m3/s) valve stroke (m, mm) wall thickness of drive pipe (m) cycle time (s) velocity to close impulse valve (m/s) steady state velocity (m/s) volume fraction of air trapped in drive pipe Rankine efficiency

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Design of Homologous Ram Pumps

Young

1997

Journal of Fluids Engineering

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The hydraulic ram pump was invented over 200 years ago but became obsolete with the availability of mains water. Ram pumps make use of a renewable energy resource and are environmentally friendly. They are particularly appropriate for use in the developing world as their construction is basic and robust and they are inexpensive and easy to install and maintain. Unfortunately, simple rational design procedures applicable to any size of pump are not available. The paper analyses the behavior of ram pumps under zero recoil conditions from which three nondimensional design relationships, applicable at any delivery head, are derived for beat frequency, quantity delivered, and source capacity in terms of the independent variables. These relationships incorporate constants consistent with existing experimental results. Recommendations are given for the maximum length of drive pipe which supersede traditional rules-of-thumb for the ratios L/D and L/H. The procedure allows selection of all system parameters, including the drive pipe length, for a set of homologous ram pumps.

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On the Optimum Utilization of Water Hammer

Cited by 4 publications

References 3 publications

Hydraulic ram analysis: a new look at an old problem

Hydraulic ram analysis: a new look at an old problem

Design of Hydraulic Ram Pump Systems

Design of Homologous Ram Pumps

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