Flow Pump System Research Articles

A novel self-supervised representation learning framework based on time-frequency alignment and interaction for mechanical fault diagnosis

Recently, supervised learning methods for intelligent mechanical fault diagnosis have achieved considerable advancements, while they heavily rely on labeled information and neglect massive unlabeled signals. Consequently, some self-supervised research has emerged and employs contrastive learning to mine general knowledge from unlabeled samples. However, these methods emphasize independent feature extraction and lack deep feature interaction, which limits better representation learning. Furthermore, it also restricts the performance improvement of fault diagnosis. To fill this gap, a novel self-supervised representation learning framework based on time-frequency alignment and interaction (TFAI) is proposed to improve the diagnosis reliability under limited labeled data. Comprising a dual encoder and a cross-modal encoder based on Transformers, the proposed TFAI model takes paired time-frequency data as input for self-supervised pretraining. Two self-supervised learning strategies, namely time-frequency alignment and time-frequency interaction, are proposed to enable the model to gain valuable knowledge from unlabeled data. The former leverages a time-frequency contrastive loss to drive the dual encoder to extract profound features from unlabeled data. The latter involves utilizing a time-frequency matching loss to guide the cross-modal encoder to perform deep feature fusion in an unsupervised manner. The well pretrained TFAI model can learn informative representations and can be fine-tuned for specific downstream fault diagnosis tasks to improve the diagnosis accuracy. By conducting three experimental cases on an axial flow pump system and a public gearbox platform system, the effectiveness, generalizability, and domain adaptability of the proposed method are validated.

Microfluidic Assessment of T Cell Deformability and Capillary Network Occlusion

Introduction: Adoptive T cell therapies offer a new frontier of cancer treatment that disrupts the conventional chemotherapy paradigm. Naïve T cells can be genetically modified to directly target cancerous cells and have proven to be aggressively effective in fighting cancers resistant to chemotherapies. A major challenge that adoptive T cell therapies face is successfully delivering the cell products to the location of the target cells, which is particularly challenging in the case of solid tumors. A complete characterization of the biomechanical properties of T cell products would help researchers gain insight into the capacity of these engineered cells to navigate and extravasate through vasculature and tumor microenvironments. Previous studies have found that T cell volume, cortical tension, and dynamic resistance increase with activation (Waugh et al. Front Bioeng Biotechnol. 2023). A simple and reproducible method to easily quantify and assess such cellular properties has yet to be established. Presently, we describe a microfluidic assay for the rapid and robust characterization of the mechanical changes of T cells upon activation. Our assay models the microcapillaries through a gradient of micropillar arrays, which allows for the evaluation of T cells perfused through the network. The spacing between pillars is 12 µm at the first array, similar to small arterioles, and incrementally decreases to 3 µm spacing in the last array, mimicking small capillaries ( Figure 1A). Trafficking of adoptive T cell therapies through the microvasculature networks of this scale into their target tissues represents a persistent and major challenge facing these therapies (Marofi et al. Stem Cell Res. Ther. 2021). Methods: The microfluidic devices were fabricated by casting polydimethylsiloxane (PDMS) on a silicone wafer fabricated through photolithographic protocols. Devices contain arrays of pillars measuring 20 µm x 10 µm x 12 µm with gradient spacing beginning at 12 µm at the inlet and 3 µm at the outlet. Jurkat T cells were cultured in RPMI 1640 medium with 10% fetal bovine serum and used in a naïve state or activated via antibody stimulation of CD3 and CD28. T cells were then suspended in growth media at 1x10 6 cells/mL. Microchannels were wetted and cleaned with 100% ethanol perfused at 10 µL/min for 15 minutes followed by cell culture media at 10 µL/min for 15 minutes to block the non-specific binding sites on the PDMS and to create a biocompatible environment for the cell sample. The devices were connected to a digital pneumatic pressure-based flow pump system. The cell sample was perfused at 100 mBar for 7 minutes and a subsequent wash process with growth media at 100 mBar for 7 minutes was performed to flush non-occluded cells. Upon completion of the experiment, the channel was scanned using Phase and DAPI filters with an Olympus IX83 inverted motorized microscope, and occluded T cells were quantified using ImageJ. Results: Our assay showed distinct levels of T cell occlusion upon activation through CD3 and CD28 stimulation. Naïve T cells showed lower levels of occlusion in each of the first five arrays compared to activated T cells, while both groups showed high levels of occlusion in the final 3 µm array. Activated T cells showed approximately three times the amount of occlusion in the second through fifth arrays. To assess overall occlusion, we use the Occlusion Index (OI), which considers the density of pillars and the number of cells caught in each array. We found that activated T cells had a significantly higher OI when compared to non-activated T cell samples (p < 0.05, unpaired t-test). Naïve T cells had an OI mean of 24.4 ± 5.0 while activated T cells had a mean of 42.5 ± 5.6 ( Figure 1B). Conclusions: Our results show that there is a significant increase in resistance of activated T cells through a microvasculature-modeled environment compared to their naïve counterparts. As adoptive T cell therapies increase in popularity, a complete understanding of the biomechanical properties of these cell products will be necessary for effective design. Our microfluidic assay mimics the narrowing channels of the microvasculature and permits the study of how naïve and engineered T cells travel through these mechanically challenging spaces.

Investigation on the Influence of Flap Valve Area on Transition Process of Large Axial Flow Pump System

The large axial flow pump systems used in coastal pump stations are often required to add flap valves to the gates to improve the quality of the transition process. However, due to the unclear mechanism of the additional flap valve on the transition process of the large axial flow pump system, there are many difficulties in the design and application of this feature. In this paper, six kinds of flap valves with different areas are designed. On the basis of the secondary development of the Flomaster software, the transient simulation method is used to study the impact of flap valves with different areas on the large axial flow pump system synchronous start-up process, the asynchronous start-up process, the synchronous stop process and the asynchronous stop process. The research results show that when the AOF is less than 38% Ag during the asynchronous startup, increasing the AOF can significantly improve the shunt ability of the flap valve during startup. However, in the process of asynchronous starting, the working capacity of the flap valve is less affected by the AOF. During the asynchronous shutdown process, the additional flap valve can effectively delay the attenuation of the LAPS flow and reduce the instantaneous head and power. However, when the AOF reaches 38% Ag, further increasing the AOF has no obvious gain in reducing the maximum instantaneous head and power of the LAPS. When the AOF increases from 38% Ag to 49% Ag, the maximum instantaneous head and the power of the LAPS only decrease by 2.7% and 1.4%, respectively.

Experimental and numerical study of reverse power generation in coastal axial flow pump system using coastal water

Coastal areas require frequent drainage to prevent waterlogging, and are often equipped with axial flow pump systems to enable this. Reverse power generation from CAPS (coastal axial flow pump systems) using coastal water is an untapped but high-potential source of renewable energy. However, the design of CAPS usually considers only the pumping conditions; there isa huge difference in flow during the reverse power generation condition (TC) and the conventional pumping condition (PC). If such a CAPS were to operate under TC, there would be unknown risks to its hydraulic performance and operational stability. In this study a special experimental test bench is built for the evaluation of CAPS. Energy test and measurement of internal pressure field are carried out for TC and PC of CAPS under full flow condition. Then, the energy loss characteristics and the propagation law of CAPS under PC and TC are investigated by an unsteady numerical simulation, and the results of the simulation are compared with the experimental results. The flow field difference between the PC and TC is analyzed in detail, and the hydraulic performance, operation safety, and stability of CAPS under TC are evaluated. This paper is expected to be of reference value for the renewable utilization of low-head water resources in coastal areas.

Investigation on Start-Up Characteristics of Large Axial Flow Pump Systems Considering the Influence of Auxiliary Safety Facilities

A large number of operation practices show that the reliability and stability of large axial flow pump systems will face significant challenges during the start-up process. If the start-up control mode or safety auxiliary facilities of large axial flow pump stations are unreasonable, start-up failure will easily follow. In order to find a scientific control strategy for the start-up of large axial flow pump stations, the start-up characteristics of large axial flow pump stations must be fully understood first. In this paper, based on the secondary development of Flowmaster software, a simulation study of the start-up process of a large axial flow pump system equipped with different safety aids is carried out. It is found that it is a very dangerous start-up control mode to delay the opening of the rapid-drop gate to reduce the maximum reflux value and reflux duration when the pump system is initially started. When the rapid-drop gate opens with a delay of 4 s, the power overload coefficient reaches 23.49, indicating that the possibility of start-up failure of the large axial flow pump system increases sharply the longer the gate delay is opened. The method of adding a flap valve to the rapid-drop gate can significantly weaken the instantaneous impact power of the unit and prevent the unit from overload. When safety auxiliary facilities with an additional disc valve on the fast descending gate are adopted, the backflow coefficient is within 0.2, the impact head coefficient is within 2, and the power overload coefficient is less than 0. The research results will provide an important reference value for comprehensively understanding the start-up characteristics of large axial flow pump stations and finding scientific and safe start-up control strategies.

Numerical and Experimental Study on the Shutdown Transition Process of a Large Axial Flow Pump System Focusing on the Influence of Gate Control

Large axial flow pump systems (LAPS) are widely used in coastal pump stations. In the actual operation of a LAPS, various accidents often occur during shutdown due to the unreasonable control of stop flow measures such as the gate. In this paper, based on the secondary development of Flowmaster numerical software, a numerical simulation study was conducted on the shutdown process of a LAPS with different gate control laws. It was found that the MBV of the shutdown process was greater if the gate was closed more slowly after the unit was powered off. When a 30 s shutdown scheme was used, the MBV during shutdown was 1.63Qr. When a 60s long shutdown scheme was used, the MBV during shutdown was 1.67Qr, an increase of 2.45%. When the 150s long shutdown scheme was used, the MVV during the stopping process reached 1.68Qr, which is an increase of 3.07%. The shutdown method of closing the gate in advance can significantly improve the violent fluctuations of the KCPs of a LAPS during the shutdown transition and will effectively reduce the backflow and the reverse speed of the pump during the shutdown process. Taking the total gate closing time of 120 s as an example, when the 25% gate was closed in advance, the MBV and MRS during the shutdown process were reduced by 14.31% and 1.93%. When the shutdown scenario of preclosing 100% of the gates was adopted, the MBV and MRS during shutdown were reduced by 96.31% and 100%.

Study of Safety Auxiliary Facilities to Prevent the Start-Up Failure of Large Axial Flow Pump Systems under Gate Failure Working Conditions

Large axial flow pump systems are used in coastal pump stations. It is common and very dangerous for large axial flow pump systems to encounter the failure of the fast hydraulic gate during start-up operations. Methods for equipping LAPS with reasonable safety aids for start-up operations in order to deal with the unexpected situation that the quick gate cannot be opened, limiting the safety and stability of LAPS, have become a key focus of research. We aim to investigate the effect of safety aids on the LAPS’s start-up characteristics under gate rejection conditions and to find the best safety aid allocation method to solve the LAPS’s start-up failure problem. Based on the verification of the model test, a numerical simulation of the start-up process of the large axial flow pump system equipped with auxiliary safety features was carried out under the condition of gate rejection. The results show that under the condition of gate rejection, the auxiliary FLVA or OVHO can help LAPS reduce the risk of start-up failure to a certain extent. The FLVA will play the main protective role during the start-up operations of the LAPS if the LAPS is equipped with both the OVHO and FLVA of unrestricted size under the gate rejection condition. LAPS equipped with OVHO (1.27 Hm) and FLVA (49.1% Ag) and LAPS equipped with FLVA (49.1% Ag) have comparable start-up safety. The latter has an His of 1.783 Hr and a Pis of 1.30 Pr. The former has an instantaneous shock head of 1.772 Hr and a Pis of 1.30 Pr, which exhibit a decrease of 0.38% and 0 %, respectively. The research results will provide an important reference value for the prevention of pump station start-up failures under gate rejection conditions.

Abstract 13352: Differential Response of Healthy Endocardial Cells versus Endocardial Fibroelastosis-Derived Cells to Flow Alterations and Statins

Introduction: Endocardial Fibroelastosis (EFE) is a subendocardial thickening of organized collagen and elastin layers restricting the ventricle. It has been linked to flow disturbances in congenital heart defects. Endothelial-to-mesenchymal transition (EndMT) has been identified as the underlying mechanism for EFE and also plays a central role in other diseases such as atherosclerosis where statins (e. g. atorvastatin) have been successfully used as EndMT-inhibitors. This study sought to establish a causal relationship between flow and EndMT, and to determine the protective effects of atorvastatin. Methods: Healthy endocardial endothelial cells (EECs) and EFE-derived EECs were exposed to either flow stagnation (≤5dynes/cm 2 ) with and without atorvastatin (0.5μmol/l) or physiological flow (~10dynes/cm 2 ) using a flow pump system (ibidi). Active EndMT (double staining with αSMA and CD31/VE-Cadherin) and collagen production was determined by immunohistochemical staining. Results: In healthy EECs (n=4), flow stagnation induced EndMT and collagen production which was significantly ameliorated by physiological flow (n=3, p<0.001, Fig. 1A+C). In contrast, physiological flow resulted in an increase in collagen production by 89% (n=8, p<0.001, Fig. 1D) in EFE-derived EECs. Under flow stagnation, atorvastatin inhibited EndMT (reduction by 39%, p<0.001, Fig. 1A) and collagen production in healthy EECs (reduction by 9%, p<0.001, Fig. 1C). This effect was blunted in EFE-derived EECs regarding EndMT reduction (17%, p<0.001, Fig. 1B), with no effect on collagen. Conclusion: Physiological flow and atorvastatin protect healthy EECs from EndMT but only the latter is beneficial for EFE-derived EECs. Thus, statins potentially offer a preventative treatment for EFE patients with flow stagnation. This study revealed a profound difference in the response to flow of healthy and EFE-derived EECs, indicating an intrinsic predisposition to EndMT in these patients.

Influence of spiral flow on the hydraulic performance of a siphon outlet conduit in an axial flow pump system

In axial flow pump systems, not only are the flow rates typically large but the water leaving the guide vanes almost invariably possesses a residual rotation. Since such pumps often generate only low heads, the energy content of this residual rotation often has a notable influence on the hydraulic and economic performance of the outlet conduit. The hydraulic losses and flow fields associated with a specific siphon outlet conduit under different rotational speeds are herein studied both experimentally and using a 3D turbulent flow numerical simulation. In order to experimentally verify the simulation results, the hydraulic losses are measured and flow patterns are observed for a siphon outlet conduit with a series of different guide vanes. It is observed that as the rotational speed increases the hydraulic loss within this outlet conduit increases gradually until the rotation speed reaches 300 ; as the rotational speed surpasses this value, the hydraulic losses increase sharply. Yet surprisingly, residual swirl can have benefits, with the general trend being that larger rotational speeds are associated with a smaller vortex zones and a better flow field in the outlet conduit, an observation confirmed both numerically and experimentally. This research has considerable significance, both theoretically and practically, for the design of outlet conduits and guide vanes in axial flow pump system.

Investigation on hydrodynamic characteristics of coastal axial flow pump system model under full working condition of forward rotation based on experiment and CFD method

Axial flow pump system is widely used in marine jet propulsion equipment and pump stations along the river coastal areas. In order to explore the safety and reliability of axial flow pump system, especially the axial-flow pump system in pump stations in coastal areas, in response to various extreme conditions. In this paper, a high-precision full-feature test bench for axial flow pump system is built, and the axial flow pump system model in a coastal area is manufactured. The axial flow pump system is experimentally tested under various extreme conditions. Then a numerical model for predicting the full characteristics of axial flow pump system is proposed, and the numerical results are compared with the experimental results. The full working condition hydrodynamic characteristics of axial flow pump system are revealed, including pump condition, turbine condition, braking condition and various extreme operating conditions. The research results provide reference for the safe and stable operation of axial flow pump system, especially coastal axial flow pump stations under various extreme conditions.

Investigation of the hydrodynamic characteristics of an axial flow pump system under special utilization conditions

In actual operation, axial flow pump stations are often used for various special purposes to meet changing needs. However, because the hydrodynamic characteristics of axial flow pump systems are still unclear when used for special purposes, there are many risks when pump systems are used for special purposes. To explore the hydrodynamic characteristics of an axial flow pump system under special utilization conditions, a high-precision full-feature test bench for an axial flow pump system is established in this paper. For the first time, an energy characteristics experiment and a pressure fluctuation measurement for a pump are carried out for a large axial flow pump system model under zero head, reverse pump and reverse power generation conditions. Then, ANSYS CFX software is used to solve the continuous equation and Reynolds average Navier–Stokes equation, combined with the SST k–ω turbulence model, and the characteristic curve and internal flow field of the pump system under special conditions are obtained. Finally, the numerical simulation results are compared with the experimental results. The results show that the velocity gradient distribution in the pump is uniform under the near zero head condition (NZHC), and there is no obvious flow collision and reflux phenomenon in the pump. Compared with the designed condition (DC), the peak-to-peak value (PPV) of pressure pulsation at the inlet of the impeller decreased by 67.16%, and the PPV at the outlet of the impeller decreased by 8.14% at H = 0 m. The maximum value of the main frequency amplitude (MFA) in the impeller area appears at the impeller inlet. Under reverse pump conditions (RPC), the phenomenon of unstable flow in the pump system is obvious, and a large range of recirculation zones appears in the nonworking face of the blade. Compared with the DC, the PPV of the impeller inlet at the optimal point of RPC increased by 122.61%, and the impeller outlet PPV increased by 11.37%. The maximum value of MFA in the impeller area appears at the impeller inlet. Under the reverse power generation condition (RPGC), no obvious flow separation was found in the nonworking face of the impeller. Compared to the DC, the PPV of the impeller inlet at the optimal point of the RPGC increased by 65.34%, and the PPV of the impeller outlet increased by 206.40%.

Experiment on Pressure Pulsation of Axial Flow Pump System with Different Runaway Head

The runaway condition is a damage condition for pumps and turbines which can induce the wake vortex, reverse flow, and severe pressure pulsation. This study aimed to research the characteristics of pressure pulsation of axial flow pumps under different runaway conditions, and the runaway model test was performed with different blade angles and heads. Moreover, four pressure sensors were uniformly arranged at the impeller inlet section to eliminate the random error. The time domain and frequency domain analysis were the main methods to obtain the change regulations. Results showed that the pressure pulsation under the runaway condition are mainly influenced by the rotation frequency, blade passing frequency, and wake vortex frequency. The dimensionless pressure pulsation coefficient of rotation frequency and wake vortex frequency increased obviously with the runaway head increasing, but changed little with different blade angles. In addition, the dimensionless pressure coefficient of wake vortex frequency of the sensors around the impeller inlet section differed a lot, which means that the wake vortex core is not in center of the rotation axis. The average dimensionless pressure pulsation coefficient of wake vortex frequency is higher than that of rotation frequency with the same runaway head, owing to the severer wake vortex.

The composition of vulnerable plaque and its effect on arterial waveforms

Carotid plaque composition is a key factor of plaque stability and it carries significant prognostic information. The carotid unstable plaques are characterized by a thin fibrous cap (FC) ≤65μm with large lipid core (LC), while stable plaques have a thicker FC and less LC. Identifying the percentage of plaque compositions could help surgeons to make a precise decision for their patients’ treatment protocol. This study aims to distinguish between stable and unstable plaque by defining the relationship between plaque composition and arterial waveform non-invasively. An in-vitro arterial system, composed of a Harvard pulsatile flow pump and artificial circulation system, was used to investigate the effect of the plaque compositions on the pulsatile arterial waveforms. Five types of arterial plaques, composed of the LC, FC, Collagen (Col) and Calcium (Ca), were implemented into the artificial carotid artery to represent the diseased arterial system with 30% of blockage. The pulsatile pressure, velocity and arterial wall movement were measured simultaneously at the site proximal to the plaque. Non-invasive wave intensity analysis (Non-WIA) was used to separate the waves into forward and backward components. The correlation between the plaque compositions and the reflected waveforms was quantitatively analysed. The experimental results indicate that the reflected waveforms are strongly correlated with the plaque compositions, where the percentages of the Col are linearly correlated with the amplitude of the backward diameter (correlation coefficient, r = 0.74) and the lipid content has a strong negative correlation with the backward diameter (r = 0.82). A slight weak correlation exists between the reflected waveform and the percentage of Ca. The strong correlation between the compositions of the plaques with the backward waveforms observed in this study demonstrates that the components of the arterial plaques could be distinguished by the arterial waveforms. This finding might lead to a potential novel non-invasive clinical tool to determine the composition of the plaques and distinguish between stable and vulnerable arterial plaques at the early stage.

Shape Memory Tube Plug for Fine-control of Intraocular Pressure by Glaucoma Devices.

As a standard approach to treating glaucoma, a silicone tube device is inserted into the eye to drain water and thereby lower the intraocular pressure (IOP). However, the fixed diameter of the tube often results in too much initial water drain. Suture-sheaving of the outer tube wall also leads to random IOP drops over time. In this study, self-expansion of the inner tube diameter was achieved by inserting a shape memory tube into the silicone tube. The difference in controlling small to large IOP drops before and after tube diameter expansion was demonstrated via computational modeling, a flow pumping system, and rabbit experiments.

Real-Time 2-D Phased Array Vector Flow Imaging.

Echocardiography examination of the blood flow is currently either restricted to 1-D techniques in real-time or experimental offline 2-D methods. This paper presents an implementation of transverse oscillation for real-time 2-D vector flow imaging (VFI) on a commercial BK Ultrasound scanner. A large field-of-view (FOV) sequence for studying flow dynamics at 11 frames per second (fps) and a sequence for studying peak systolic velocities (PSVs) with a narrow FOV at 36 fps were validated. The VFI sequences were validated in a flow rig with continuous laminar parabolic flow and in a pulsating flow pump system before being tested in vivo, where measurements were obtained on two healthy volunteers. Mean PSV from 11 cycles was 155 cms-1 with a precision of ±9.0% for the pulsating flow pump. In vivo, PSV estimated in the ascending aorta was 135 cms-1 ± 16.9% for eight cardiac cycles. Furthermore, in vivo flow dynamics of the left ventricle and in the ascending aorta were visualized. In conclusion, angle independent 2-D VFI on a phased array has been implemented in real time, and it is capable of providing quantitative and qualitative flow evaluations of both the complex and fully transverse flow.

Effect of the flow in blade root-leakage on hydraulic characteristic in axial flow pump system

The clearance locate on blade root is almost 10~20 times than tip in adjustable axial flow pump, the flow in blade root clearance has obvious impact on the hydraulic characteristic in pump systems. In order to research the effect of blade root clearance on hydraulic characteristic in axial flow pump system, a vertical axial flow pump system is researched by numerical simulation and experiment. After considering the root clearance, the result has high precision under large and design flow condition. The simulation result shows with the effect of the blade root clearance, the velocity distribution from hub to shroud is trend bad, and the streamline near the blade root is changed greatly, under the same flow condition, the flow far away from the hub in the cascade is increasing, the work ability of blade is reducing, the head has a sharp fall. In this paper, only 0.5mm clearance exist, 2.9% blade surface area is loss, the head decrease 7.86%, shaft power decrease 6.35%, the efficiency from 76.04% down to 74.82%. The conversion formula between the pump station with and without gap clearance is gained by theoretical derivation.

Numerical analysis of the influence of vortex on the pressure pulsation in axial flow pump system based on the CFD

The pressure pulsation is one of the main causes of vibration and noise in axial flow pump, in order to study the mechanism of pressure fluctuation induced by vortex, several pressure pulsation monitoring points were stalled at the bottom of the pump sump, the horn mouth, the impeller inlet and outlet, the outlet of the guide vane. The flow rate of 1.2Qd ( Q=38.4L/s) was selected at the speed of 2200r/min. Realizable k- epsilon turbulence model is adopted with setting up different time calculation methods by using CFX software. Changing the time step, unsteady calculation of axial flow pump device is carried out, and the pressure values of different monitoring points at different time are obtained. The frequency domain characteristics of different feature sections are obtained by FFT. The results show that the vortex position at the bottom of the inlet of the flare tube is consistent with the position of the low pressure zone, and the main frequency of the pressure fluctuation is twice of the frequency of the impeller. The characteristics of pressure fluctuation at the bottom of the inlet of the horn are consistent with the experimental results. Under the influence of impeller rotation, the main frequency of pressure fluctuation at the inlet and outlet of impeller is 4 times of the impeller rotation frequency. The main frequency of pressure fluctuation at the guide vane outlet is 3 times of that of the impeller. The amplitude of pressure fluctuation increases gradually from the bottom of inlet to the inlet of impeller. On the whole, the maximum amplitude of pressure fluctuation is at the inlet of impeller, and the maximum amplitude of pressure fluctuation occurs at the center of the vortex belt. The Cp value of the pressure fluctuation at the center of the vortex belt is about 1.8-2 times of the Cp value of the pressure fluctuation at the non-central point.

Low-Dimensional Modeling of a Pumping Unit to Cope With Multiphase Flow

Pumping unit efficiency is highly disturbed by the presence of gas influx reducing the productivity and inducing unpredictable system response due to the change of its intrinsic properties such as the natural frequency. A poor estimation of those properties may affect the on-field crew and system safety as well as the production rate. The purpose of this paper is to construct a hydromechanical model describing the coupled multiphase flow-pumping unit system dynamics and to develop a procedure to control the pumping speed for safety assurance and oil production maximization. A coupled mechanical-multiphase flow model capturing the interplay between the gas void fraction (GVF) and the driving harmonic force of the pumping unit is developed. Specifically, the predicted downhole pressure is used to determine the sucker rod effective load. Consequently, a reduced-order model, capturing the dynamics of the sucker rod, is used to estimate the saddle bearings axial displacements which are function of polished rod loading. An error-driven adaptation using the difference between presumed bearing displacement with known GVF and the predicted bearing displacement from the proposed multiphysics model is employed to estimate the unknown downhole GVF. The obtained results prove that the adaptation allows an accurate evaluation of the pumped fluid's GVF, thereby circumventing the need for a costly and inaccurate measurement of the two-phase flow gas fraction. Based on this estimation, a control strategy is then proposed to regulate the pump speed while avoiding the resonance frequency of the sucker-rod system.

Wall-Less Flow Phantoms With Tortuous Vascular Geometries: Design Principles and a Patient-Specific Model Fabrication Example.

Flow phantoms with anatomically realistic geometry and high acoustic compatibility are valuable investigative tools in vascular ultrasound studies. Here, we present a new framework to fabricate ultrasound-compatible flow phantoms to replicate human vasculature that is tortuous, nonplanar, and branching in nature. This framework is based upon the integration of rapid prototyping and investment casting principles. A pedagogical walkthrough of our engineering protocol is presented in this paper using a patient-specific cerebral aneurysm model as an exemplar demonstration. The procedure for constructing the flow circuit component of the phantoms is also presented, including the design of a programmable flow pump system, the fabrication of blood mimicking fluid, and flow rate calibration. Using polyvinyl alcohol cryogel as the tissue mimicking material, phantoms developed with the presented protocol exhibited physiologically relevant acoustic properties [attenuation coefficient: 0.229±0.032 dB/( [Formula: see text]) and acoustic speed: 1535±2.4 m/s], and their pulsatile flow dynamics closely resembled the flow profile input. As a first application of our developed phantoms, the flow pattern of the patient-specific aneurysm model was visualized by performing high-frame-rate color-encoded speckle imaging over multiple time-synchronized scan planes. Persistent recirculation was observed, and the vortex center was found to shift in position over a cardiac cycle, indicating the 3-D nature of flow recirculation inside an aneurysm. These findings suggest that phantoms produced from our reported protocol can serve well as acoustically compatible test beds for vascular ultrasound studies, including 3-D flow imaging.

A High Performance Pulsatile Pump for Aortic Flow Experiments in 3-Dimensional Models.

Aortic pathologies such as coarctation, dissection, and aneurysm represent a particularly emergent class of cardiovascular diseases. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies, as well as for planning their surgical repair. In vitro experiments are required to validate the simulations against real world data, and the experiments require a pulsatile flow pump system that can provide physiologic flow conditions characteristic of the aorta. We designed a newly capable piston-based pulsatile flow pump system that can generate high volume flow rates (850mL/s), replicate physiologic waveforms, and pump high viscosity fluids against large impedances. The system is also compatible with a broad range of fluid types, and is operable in magnetic resonance imaging environments. Performance of the system was validated using image processing-based analysis of piston motion as well as particle image velocimetry. The new system represents a more capable pumping solution for aortic flow experiments than other available designs, and can be manufactured at a relatively low cost.