Pump Casing Research Articles

CFD Predictions of Dense Slurry Flow in Centrifugal Pump Casings

CFD Predictions of Dense Slurry Flow in Centrifugal Pump Casings

Dynamic behavior of gear pumps: effect of variations in operational and design parameters

This work presents a wide number of results about the influence that variations in terms of operational and design parameters play on the dynamic behavior of external gear pumps. These results are obtained by using a non-linear lumped-parameter kineto-elastodynamic model developed and experimentally assessed with the aim of including all the important dynamic effects. On the one hand, the effects of variations in the operational parameters—namely output pressure, rotational speed and oil viscosity—are analysed; on the other hand, the effects of modifications of some design parameters are shown: clearances and relief groove dimension. The results in terms of gear eccentricity, pressure evolution, pressure forces, gear accelerations and variable forces exciting the pump casing enlighten the dynamic behavior of gear pumps and give useful indications for design improvements and vibration and noise reduction. As regards specifically gear accelerations as well as forces exciting the casing, they strongly increase with both output pressure and rotational speed, but variations in rotational speed in the operational range give lower effects. Conversely, the modifications of the clearances give negligible effects, while the relief groove dimension is very important: the larger the relief grooves are, the higher the gear accelerations and forces exciting the casing become.

Peristaltic Flow of a Maxwell Model Through Porous Boundaries in a Porous Medium

In the present investigation we have presented the peristaltic flow of a linear Maxwell model through porous boundaries in a porous medium. The governing non-dimensional partial differential are solved in wave frame by using regular perturbation method and assumed form of solution. We have discussed the problem only for free pumping case. The effects of various physical parameters involved in the problem have been investigated and shown graphically.

Evaluation of the Impeller Shroud Performance of an Axial Flow Ventricular Assist Device Using Computational Fluid Dynamics

Generally, there are two types of impeller design used in the axial flow blood pumps. For the first type, which can be found in most of the axial flow blood pumps, the magnet is embedded inside the impeller hub or blades. For the second type, the magnet is embedded inside the cylindrical impeller shroud, and this design has not only increased the rotating stability of the impeller but has also avoided the flow interaction between the impeller blade tip and the pump casing. Although the axial flow blood pumps with either impeller design have been studied individually, the comparisons between these two designs have not been conducted in the literature. Therefore, in this study, two axial flow blood pumps with and without impeller shrouds were numerically simulated with computational fluid dynamics and compared with each other in terms of hydraulic and hematologic performances. For the ease of comparison, these two models have the same inner components, which include a three-blade straightener, a two-blade impeller, and a three-blade diffuser. The simulation results showed that the model with impeller shroud had a lower static pressure head with a lower hydraulic efficiency than its counterpart. It was also found that the blood had a high possibility to deposit on the impeller shroud inner surface, which greatly enhanced the possibility of thrombus formation. The blood damage indices in both models were around 1%, which was much lower than the 13.1% of the axial flow blood pump of Yano et al. with the corresponding experimental hemolysis of 0.033 g/100 L.

Computational Study of Magnetically Suspended Centrifugal Blood Pump (The First Report: Main Flow and Gap Flow)

Artificial heart pumps have attracted the attention of researchers around the world as an alternative to the organ used in cardiac transplantation. Conventional centrifugal pumps are no longer considered suitable for long-term application because of the possibility of occurrence of blood leakage and thrombus formation around the shaft seal. To overcome this problem posed by the shaft seal in conventional centrifugal pumps, the magnetically suspended centrifugal pump has been developed; this is a sealless rotor pump, which can provide contact-free rotation of the impeller without leading to material wear. In Europe, clinical trials of this pump have been successfully performed, and these pumps are commercially available. One of the aims of our study is to numerically examine the internal flow and the effect of leakage flow through the gap between the impeller and the pump casing on the performance of the pump. The results show that the pressure head increases compared with the pump without a gap for all flow rates because of the leakage of the fluid through the gap. It was observed that the leakage flow rate in the pump is sufficiently large; further, no stagnant fluid or dead flow regions were observed in the pump. Therefore, the present pump can efficiently enhance the washout effect.

Pump monitoring: unusual incidents

Condition monitoring tests are beneficial in improving both the operation and maintenance of pumping systems. Here, Ray Beebe of Monash University uses a slurry pump case study to illustrate the value of basic head–flow tests for a system where restricted access made conventional flow measurements difficult.

Spin-dependent pump current and noise in an adiabatic quantum pump based on domain walls in a magnetic nanowire

We study the pump current and noise properties in an adiabatically modulated magnetic nanowire with double domain walls (DW). The modulation is brought about by applying a slowly oscillating magnetic and electric fields with a controllable phase difference. The pumping mechanism resembles the case of the quantum dot pump with two-oscillating gates. The pump current, shot noise, and heat flow show peaks when the Fermi energy matches with the spin-split resonant levels localized between the DWs. The peak height of the pump current is an indicator for the lifetime of the spin-split quasistationary states between the DWs. For sharp DWs, the energy absorption from the oscillating fields results in side-band formations observable in the pump current. The pump noise carries information on the correlation properties between the nonequilibrium electrons and the quasi-holes created by the oscillating scatterer. The ratio between the pump shot noise and the heat flow serves as an indicator for quasi-particle correlation.

The Wall Properties Effect on Peristaltic Transport of Micropolar Non‐Newtonian Fluid with Heat and Mass Transfer

The problem of the unsteady peristaltic mechanism with heat and mass transfer of an incompressible micropolar non‐Newtonian fluid in a two‐dimensional channel. The flow includes the viscoelastic wall properties and micropolar fluid parameters using the equations of the fluid as well as of the deformable boundaries. A perturbation solution is obtained, which satisfies the momentum, angular momentum, energy, and concentration equations for case of free pumping (original stationary fluid). Numerical results for the stream function, temperature, and concentration distributions are obtained. Several graphs of physical interest are displayed and discussed.

A Fourier Series Approach to Analyze Pump Modulation Induced Noise in Raman Amplifiers With TDM Pumps

In this letter, Raman amplifiers (RAs) with time-division-multiplexed (TDM) pumps are analyzed using a computational cost-effective Fourier series approach. Analytical approximate formulas are derived based on this model. These formulas bring deep insight into the pump modulation induced noise (PMIN) in TDM pumped RAs. Moreover, the approach allows the analytical analysis of the TDM pumped RAs with multiple pumps while previous analytical studies mostly focused on the single pump and single signal channel case. By optimizing the pumping order of the multiple pumps, more than 3-dB reduction of the PMIN can be achieved. For short fibers, by properly choosing the modulation frequency, more than 3-dB reduction of the PMIN can be realized.

Analytical Design Curves to Maximize Pumping or Minimize Injection in Coastal Aquifers

Explicit algebraic equations are derived to determine approximate maximum pumping rates or minimum injection rates to limit sea water intrusion to a prespecified distance from the coastline. The equations are based on Strack's (1976) single-potential solution. The maximum pumping rates and minimum injection rates applied at wells with uniform spacing to control the inland movement of the fresh water-salt water interface in a coastal aquifer could be calculated from Strack's (1976) solution without the need of a numerical optimization algorithm. When wells are distributed in a simple fashion, the maximum intrusion location can be identified precisely for pumping cases and approximately for injection cases. For pumping cases, critical points are the limit of allowable salt water intrusion, whereas no such limit exists for injection cases. Once an application site is identified, a series of design curves for pumping and injection rates can be developed for arbitrary intrusion limits. When a user is interested only in the largest pumping rates associated with critical points, one design curve can yield complete information.

Axial Magnetic Bearing Development for the BiVACOR Rotary BiVAD/TAH

A suspension system for the BiVACOR biventricular assist device (BiVAD) has been developed and tested. The device features two semi-open centrifugal impellers mounted on a common rotating hub. Flow balancing is achieved through the movement of the rotor in the axial direction. The rotor is suspended in the pump casings by an active magnetic suspension system in the axial direction and a passive hydrodynamic bearing in the radial direction. This paper investigates the axial movement capacity of the magnetic bearing system and the power consumption at various operating points. The force capacity of the passive hydrodynamic bearing is investigated using a viscous glycerol solution. Axial rotor movement in the range of +/-0.15 mm is confirmed and power consumption is under 15.5 W. The journal bearing is shown to stabilize the rotor in the radial direction at the required operating speed. Magnetic levitation is a viable suspension technique for the impeller of an artificial heart to improve device lifetime and reduce blood damage.

Munitions and Dredging Experience on the United States Coast

AbstractA number of dredging projects have unknowingly and unfortunately encountered munitions and explosives of concern (MEC). MEC have been discovered on dredges (e.g., in dragheads, cutterheads, pump casings) and at the dredged material placement site. Detonations have occurred that have either damaged the dredge plant or have even sunk the dredging vessel. A number of recent dredging projects have proactively addressed MEC issues before the start of construction, thereby greatly reducing overall risk and MEC cleanup costs. This paper explains common dredging equipment, discusses techniques useful in reducing the inherent risks of dredging in sediments containing MEC, and discusses lessons learned during various dredging projects involving MEC.Application of MEC avoidance and exclusion techniques during dredging operations is minor compared to the enormous cost of post-dredging MEC cleanup. Most importantly, it is possible to avoid exposing the public to explosive safety hazards and minimize those to workers with proper planning and execution.

Erosion–corrosion performance of high-Cr cast iron alloys in flowing liquid–solid slurries

In many slurry transportation systems, such as in FGD (Flue Gas Desulphurization) and chemical processing applications, corrosion and erosion are the two main mechanisms of material degradation of the pump wet-end components including pump casing, impeller and liners. The performance of a selected material is mostly dependent upon its relative corrosion and erosion resistance to the service environment. In these cases erosion, corrosion and the related synergistic effects can be very complicated since they are affected by numerous factors including solid and slurry properties, chemical contents, hydraulic conditions and temperatures. In this experimental study, sliding Coriolis erosion testing has been performed with various corrosion factors such as pH value, chlorides content and temperature to evaluate the erosion–corrosion resistance of some high-alloyed white cast irons containing different levels of chromium and other elements. Optical microscope and SEM-EDS have also been used to examine microstructure and surface conditions of tested materials. Results indicated that material loss due to corrosion factors increased as acidity-chlorides and temperature increased. At relatively high corrosion intensity, the white cast irons with higher alloy content (especially chromium) clearly showed improved corrosion resistance and combined erosion–corrosion resistance over those with lower alloy content. Under certain corrosion and hydraulic conditions, particle size is perhaps the single most influential factor on erosion–corrosion rate of the high-Cr cast iron alloys. Relatively large particles are much more effective than small ones at removing both the corroded surface layer and the fresh material, causing substantially higher rate of material loss. Some other related factors have also been addressed.

Mechanisms of fatigue crack initiation and propagation in cast aluminum alloy AL5 of hydropumps NP-89D in aircraft Tu-154M

The paper demonstrates results of quantitative fractographic analyses of in-service fatigued cast AL5 Al-based alloy of hydropumps NP-89D. A model based on Vickers hardness of metal matrix and the area of defects (the “ area model”) has been introduced. It describes microcracks threshold originating from cast porosities. Crack growth period estimated by the result of meso-beach marks spacing measurements and stress equivalent calculated by the “ area model” are used to discuss causes of the in-service cracking of the pump casing. It is shown that damping of self-oscillations with simultaneous decrease in an equivalent stress level of the hydrounit will allow increasing the operating time up to pump probable failure corresponding to more than 10 10 cycles. It will lead to an increase in the period of operation of casings without their fatigue cracking by more than of two orders.

The “Tea Cup Effect” and Removal of Suspended Solids from Water

Suspended solids problem in water is an issue as old as water treatment itself. Suspended solids can be causativeto eroding through abrasion of impellers, pump casings, pipes and other water works related appurtenances.It is therefore appropriate that suspended solids must be removed as early as possible in the water workstreatment facilities. It is usually done at the river/lake intakes to reduce the coarse particulate matter thatwould otherwise adversely affect the water works thereafter. The fine particles that will escape the entrapmentat the intake works would therefore require further and more effective system that would remove this fraction.By and large this removal process is achieved by chemically aided process such as coagulation/flocculationunit operation. This process is expensive and demands high level trained personnel to man them. In the samevein then a simple and effective system is proposed. This is a swirl or grit removal system that does not needany chemicals, moving parts or even highly trained personnel to operate them. This paper is looking at thetheory of the “Tea Cup Effect” and how it has been used in practice to remove or reduce suspended solids fromwater. The paper gives some examples where such devices have been used and how effective they have been.

An integrated qualitative trend analysis approach to identify process abnormalities: A case of oil export pumps in an offshore oil and gas production facility

Oil and gas production can be largely benefited by minimizing unwanted production losses. This can be done by effective identification of system anomalies and faults. In standard control systems these abnormalities can be observed as gradually deviating trends from the norms. Available tools for monitoring these trends, in some cases, may not be enough to reveal hidden faulty features. In order to interpret these changes accurately, measured data must be visualized as a combination of multiple sensor signals within a particular domain. This article suggests an approach to effectively utilize integrated data from multiple sources, and defines a set of 12 fault features. The approach, in principle, encodes real plant data in the form of logical IF-THEN rules in Microsoft Excel. Confidence values are set based on these interpretations to differentiate between normal and abnormal conditions exhibited by the system. This is to provide an opportunity for the process and maintenance engineers to effectively identify the equipment's health based on the early identification of developing abnormalities.

Transient and nonlinear analysis of slow-light pulse propagation in an optical fiber via stimulated Brillouin scattering

We investigate slow-light pulse propagation in an optical fiber via transient stimulated Brillouin scattering. Space-time evolution of a generating slow-light pulse is numerically calculated by solving three-wave coupled-mode equations between a pump beam, an acoustic wave, and a counterpropagating signal pulse. Our mathematical treatments are applicable to both narrowband and broadband pump cases. We show that the time delay of 85% pulse width can be obtained for a signal pulse of the order of subnanosecond pulse width by using a broadband pump, while the signal pulse is broadened only by 40% of the input signal pulse. The physical origin of the pulse broadening and distortion is explained in terms of the temporal decay of the induced acoustic field.

Experimental Study of the Shaft Motion in the Journal Bearing of a Gear Pump

The movement of the shaft of a driven gear in a gear pump is experimentally studied. Three different methods are considered, and the use of a laser micrometer measurement method is validated. In order to use the laser micrometer, some modifications are made to the gear pump. Experimental results for different working pressures and rotational velocities are shown. For a low nondimensional working pressure, defined in a similar way as the Sommerfeld load, experimental and numerical results agree very well for relative eccentricity. Nevertheless, experimental results made clear that the role of the lateral plate of the pump is very important for high nondimensional working pressure. A value of 100 is given for the critical nondimensional working pressure in order to avoid wear and slant in the lateral plate. Frequency analysis of the outlet pressure, as well as the precise measurement of the wear in the pump case, support experimental observation of the inability of the journal to retain the shaft for high nondimensional pressure.

Signature of the microcavity exciton–polariton relaxation mechanism in the polarization of emitted light

We have performed real and momentum space spin-dependent spectroscopies of spontaneously formed exciton polariton condensates for a nonresonant pumping scheme. Under a linearly polarized pump, our results can be understood in terms of spin-dependent Boltzmann equations in a two-state model. This suggests that relaxation into the ground state occurs after multiple phonon-scattering events and only one polariton-polariton scattering. For the circular pumping case, in which only excitons of one spin are injected, a bottleneck effect is observed, implying inefficient relaxation.

Approaches to stable operation of shaftless centrifugal pump

The shaft-less impeller of the centrifugal pump, which is driven by the magnetic induction, was developed. The impeller rotates under the floating condition without any control device. The floating condition of the impeller is realized by utilizing the pressure in pump casing. The pump performance and the rotational behavior of the impeller were investigated experimentally. It has found that the floating position of the impeller become quite unstable in a partial flow rate operation. And the pressure distribution at the casing wall affects the rotational posture of the impeller. This paper presents the effect of the casing treatment on the rotational posture of the impeller and the pressure distribution. The reasonable casing treatment is available for the stable rotational posture of the impeller.