A CFD and experimental study on cavitation in positive displacement pump : benefits and drawbacks of the "full" cavitation model
01 Jan 2016-Engineering Applications of Computational Fluid Mechanics (Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University)-Vol. 10, Iss: 1, pp 57-71
TL;DR: In this paper, a comprehensive and transient Computational Fluid Dynamics (CFD) model of a Positive Displacement (PD) pump, simulating the cavitation arising during the suction stroke, was created.
Abstract: To fill the lack of literature in the numerical study of Positive Displacement (PD) pumps in cavitating condition, a comprehensive and transient Computational Fluid Dynamics (CFD) model of a PD pump, simulating the cavitation arising during the suction stroke, was created. The “full” cavitation model was utilised to study its capability on PD pumps cavitation. A set of three plunger speeds were simulated. Using the highest plunger speed an assessment was made of the effect of 1.5, 3, 4.5 and 15 ppm of air mass fraction on pump performance and cavitation. An experimental test rig, replicating the CFD model, was designed and built in order to validate the numerical model and find its weaknesses. CFD modelled, in a consistent way, the fluid dynamics phenomena related to cavitation (chamber pressure approaching the vapour pressure, the vaporization/condensation and the pressure spike occurrence at the end of the suction stroke marking the end of cavitation). On the other hand the CFD pressure trends calculated appeared stretched along the time axis with respect to the experimental data and this highlighted issues in the multiphase and cavitation models: the vaporization/condensation rate calculated by CFD did not follow the real dynamics correctly because the non-condensable gas expansion was overestimated. This was seen when comparing the CFD/experiments where the simulated pressure drop gradient, at the beginning of the suction stroke and the pressure peaks as the valve closed, exhibited a delay in their occurrence. The simulation results were sensitive to the dissolved air mass fraction as the delay depended on the amount of air dissolved in the water. Although the influence of the air mass fraction was considered consistent, the 3 ppm CFD case was the closest to the experiment results whereas the analyst expected the 15 ppm case to be more accurate.
Citations
More filters
TL;DR: The comparison between numerical results and the experimental performance curves has confirmed the accuracy of the model and the correct mesh selection in the small gaps and passages of the pump internal geometry and suggested the convenience of the development of a full-unsteady 3D model in the near future.
21 citations
TL;DR: In this article, an axial piston pump was tested using a confocal laser scanning microscope, by comparing the surface on the valve plate before and after the endurance life testing, and the results showed that the fluid velocities closely relate to the area of erosion damage.
Abstract: Erosion damage affects the reliability and durability of axial piston pumps An axial piston pump was tested using endurance life testing method The phenomenon of erosion damage on the valve plate was observed using a confocal laser scanning microscope, by comparing the surface on the valve plate before and after the endurance life testing A CFD turbulence model inclusive of the cavitation effects was developed to predict the flow physics The flow physics in the axial piston pump were presented and analyzed, including the fluid velocities, velocity fields, the total volume fraction fields of gas and vapor, and pressure fields Two causes of erosion damage were found, the appearances of large amount of vapor, and directly hitting by the jetting flow The first one is the cause of erosion damage on the surface near the transition region from the inlet port to the outlet port, and the second one is the cause of erosion damage on the surface near the transition region from the outlet port to the inlet port Besides, the findings show that the fluid velocities closely relate to the area of erosion damage The study provides insights into the occurrence of erosion damage in axial piston pumps
16 citations
TL;DR: A full 3D unsteady numerical model with dynamic meshes is developed to simulate the fluid–structure interaction in the non-returning valves of air-operated diaphragm volumetric pumps, providing a more accurate description of the flow patterns and a superior evaluation regarding the dynamic response of the valves motion.
13 citations
TL;DR: Gaseous and vaporous cavitation have extremely harmful effects on hydraulic axial plunger pumps, reducing flowrate and increasing flow pulsation as discussed by the authors, and the collapse of vapor bubbles strongly impacts the...
Abstract: Gaseous and vaporous cavitation have extremely harmful effects on hydraulic axial plunger pumps, reducing flowrate and increasing flow pulsation. The collapse of vapor bubbles strongly impacts the ...
13 citations
TL;DR: In this article, a systematic review of cavitation models with thermodynamic effect in simulations of cavitating flows is presented, and the features of the cavitation model are characterised and criticized, and their drawbacks are identified.
Abstract: Organic Rankine cycle (ORC) power plants are considered as one of the most promising technologies to generate power from low temperature heat sources such as biomass combustion, industrial waste heat, geothermal heat, and solar thermal energy. A feed pump is a key component of an ORC power plant to circulate the working fluid within the system. Owing to the low boiling temperature of most organic fluids, the feed pumps of ORC power plants are more vulnerable to suffer from cavitation. Cavitation of the organic fluid in the feed pump in an ORC system can degrade the evaporator performance and cause instabilities in the systems’ operation. Properly determining the required net positive suction head or subcooling for the pump is critical for the ORC system design and operation. Thus, this paper presents a systematic review of cavitation models with thermodynamic effect in simulations of cavitating flows. Methods for implementing thermodynamic effect were summarised. The features of the cavitation models were characterised and criticized, and their drawbacks were identified. A number of newly established cavitation models were explained and discussed in detail. Homogeneous mixture cavitation models have advantages such as less computational effort and easier implementation of thermodynamic effect in comparison with fully coupled multiscale models. However, when the thermodynamic effect is considered in the existing cavitation models, the cavitation regimes are not distinguished and applied properly. Nucleation cavitation models for organic fluids in ORC systems should be developed in terms of experimental nuclei profile and non-condensable gas concentration in future.
13 citations
References
More filters
TL;DR: In this paper, the authors present the full cavitation model, which accounts for all the first-order effects of cavitation and is called as the full-cavitation model and the phase change rate expressions are derived from a reduced form of Rayleigh-Plesset equation for bubble dynamics.
Abstract: Cavitating flows entail phase change and hence very large and steep density variations in the low pressure regions. These are also very sensitive to: (a) the formation and transport of vapor bubbles, (b) the turbulent fluctuations of pressure and velocity, and (c) the magnitude of noncondensible gases, which are dissolved or ingested in the operating liquid. The presented cavitation model accounts for all these first-order effects, and thus is named as the full cavitation model. The phase-change rate expressions are derived from a reduced form of Rayleigh-Plesset equation for bubble dynamics. These rates depend upon local flow conditions (pressure, velocities, turbulence) as well as fluid properties (saturation pressure, densities, and surface tension). The rate expressions employ two empirical constants, which have been calibrated with experimental data covering a very wide range of flow conditions, and do not require adjustments for different problems. The model has been implemented in an advanced, commercial, general-purpose CFD code, CFD-ACE+
1,329 citations
"A CFD and experimental study on cav..." refers background in this paper
...The reason why the air expansion in the mixture is not predicted correctly lies in the assumptions and simplifications made by the cavitation model of Singhal et al. (2002)....
[...]
01 May 1997
TL;DR: In this article, a distributed parameter model of pipeline transmission line behaviour is presented, based on a Galerkin method incorporating frequency-dependent friction, which is readily interfaced to an existing model of the pumping dynamics of a plunger pump to allow time-domain simulations of pipeline pressure pulsations in both suction and delivery lines.
Abstract: A distributed parameter model of pipeline transmission line behaviour is presented, based on a Galerkin method incorporating frequency-dependent friction This is readily interfaced to an existing model of the pumping dynamics of a plunger pump to allow time-domain simulations of pipeline pressure pulsations in both suction and delivery lines A new model for the pump inlet manifold is also proposed
31 citations
01 May 1991
TL;DR: The performance of reciprocating pumps with self-acting valves is dependent upon the dynamic characteristics of the valves as discussed by the authors, particularly when the pumps are working at high speed, delays in valve op...
Abstract: The performance of reciprocating pumps with self-acting valves is dependent upon the dynamic characteristics of the valves. Particularly when the pumps are working at high speed, delays in valve op...
31 citations
"A CFD and experimental study on cav..." refers methods in this paper
...Many authors (Johnston, 1991; Shu, Burrows, & Edge, 1997) in the past have studied PD pumps by means of analytic methods such as 1D lumped parameter models....
[...]
DOI•
01 Jan 2008
TL;DR: Tackett as discussed by the authors has 39 years of experience in the design, application, and maintenance of reciprocating power and direct acting pumps and has been a member of ASME since 1991.
Abstract: Product Manager for Union Pump Company, in Battle Creek, Michigan. He has 39 years of experience in the design, application, and maintenance of reciprocating power and direct acting pumps. Prior to Mr. Tackett’s current position in Aftermarket Product Development, he served as R&D Engineer, Field Service Engineer, and new equipment order Engineer, in addition to several positions in Reciprocating Pump Sales and Marketing. He has been a member of ASME since 1991.
27 citations
DOI•
01 Jan 1994
TL;DR: The operating principles of positive displacement (PD) pumps differ from centrifugal pumps, and the range of operating conditions is presented in several examples to illustrate problems that can be overcome with a properly specified pump.
Abstract: The operating principles of positive displacement (PD) pumps differ from centrifugal pumps. This basic difference is evident in the pump's response to a system's head/flow curve. Several pump applications are presented to illustrate the selection process needed to insure pump reliability. The performance overlap region, where both pump types should be considered, is presented with guidelines to evaluate proper selection decisions. The data that must be supplied in PD pump specifications are detailed both in definition of terms and their significance. Many engineering courses devote considerable emphasis to centrifugal pumps and system response but omit positive displacement discussion. Specifying a positive displacement pump without prior training is a difficult task. Technical requirements, performance limitations and terminology are presented to assist the person specifying a PD pump. The PD pump range of operating conditions is presented in several examples to illustrate problems that can be overcome with a properly specified pump. Fluids with large gas fractions or high viscosities can not be moved with standard centrifugal designs. PD pumps allow a wider range of liquids, slurries and foams to be transported without product degradation. Understanding where PD pumps can be used may lead to opportunities to improve processes.
26 citations
"A CFD and experimental study on cav..." refers background in this paper
...Positive displacement (PD) pumps have been overlooked by most users for years, even though they may offer significant opportunities to improve processes, enhance efficiency and reduce costs (Parker, 1994)....
[...]