Suction Flow Research Articles

Prediction of cavitation using machine learning techniques on centrifugal pump

Abstract When the local static pressure drops below the fluid’s vapour pressure at that particular temperature, a dynamic process known as cavitation takes place in the liquid. Due to cavitation, the performance (total head and flow rate) of the pump will deteriorate, and hence the vibration and noise will develop. Both the performance and cavitation investigations are carried out for a low-specific-speed pump as per the testing standards. The results obtained during cavitation studies are extracted to train the machine learning algorithms. The flow rate, speed, torque, suction head, and delivery head are considered as input variables for machine learning, with total head, Net Positive Suction Head (NPSH), efficiency, and noise magnitude being output variables. The current studies employ four machine learning techniques: random forest, support vector machines, extreme gradient boosting, and linear regression. In the analysis, notable performance was observed for the random forest and extreme gradient boosting algorithms among others consistently demonstrated superior predictive capabilities for the output parameters of the pumps. For linear regression, random forest, and extreme gradient boosting, the coefficient correlation values are around one for all output parameters except for noise. Similar observation is depicted for coefficient of determination and normalized root mean squared error. These ensure the level of noise during cavitation is very dynamic. These findings will enable the pump user to incorporate AI techniques for the diagnosis of centrifugal pump operation with reference to the nominal flow rate (best efficiency flow). Through this technology, preventive and predictive maintenance of pumps can be adapted with less downtime in process industries, power plants, chemical industries, oil and gas refineries, and so on.

A new aerosol delivery approach for enhanced long-term respiratory care in resource-poor settings

Continuous aerosol therapy is safe, superior, and the mainstay in the therapy of patients with severe asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), and coronavirus disease (COVID-19). However, continuous nebulization has been perceived as highly expensive and labor-intensive, which often requires specialized medical equipment. Moreover, it is difficult to maintain consistent aerosol output and particle size delivery over an extended period without operator intervention. This work proposes a simple and reliable continuous nebulization method using a conventional gas jet nebulizer and intravenous (IV) bottle/bag. The present work reports detailed experimental studies on a gas jet nebulizer with Particle image velocimetry (PIV), Particle/droplet Imaging Analysis (PDIA), and Mie scattering techniques to demonstrate the feasibility of the proposed technique. The preliminary investigation shows that the proposed method provides continuous liquid output delivery without external supervision. The liquid delivery rate and mass median diameter (MMD) of the nebulizer mainly depend on the gas flow rate and suction height. The MMD of the primary generated droplets is reported to vary between 100 and 230 μm for a ± 10 cm suction height and 500–1000 mlph nebulization gas flow rate. Most importantly, the nebulizer spray angle, stability, droplet size distribution, and the axial and radial velocities of the droplets are marginally affected by the suction height. Therefore, the proposed system is a versatile, safe, and cost-effective method of continuous nebulization therapy, especially in resource-poor countries or contagious disease outbreak situations.

Energy and exergy analysis and performance optimization of buildings integrated with transpired solar collectors and phase change materials

Transpired solar collectors (TSCs) are one of the cost-effective air heating technologies that can be easily installed on building facades to provide heated fresh air to condition indoor space. The economics of TSCs can be further enhanced by integrating with phase change materials (PCMs). This study presents the performance investigation and optimization of a building-integrated TSC and PCM system (TSC-PCM). The interactions between PCM thermal properties, their locations in the building envelope, and TSC design parameters were investigated. Based on the modeling of the TSC-PCM by using energy balance and enhanced enthalpy method, a series of orthogonal tests, which varied PCM type, thickness, and location within building envelopes, and TSC suction flow rate were conducted. Multivariate testing, through the Taguchi method, was then applied to identify the optimal design combination. The results showed that the suction flow rate of the TSC-PCM on the external wall showed the highest influence on enhancing indoor thermal performance (up to 77.6%), followed by PCM location on the external wall (up to 9.2%). The optimized TSC-PCM system improved the thermal comfort increase index (TCI) to 3.7 and achieved a maximum thermal efficiency of 401.8%, with an exergy improvement of 26.9% in comparison with the use of the TSC-only. The optimized TSC-PCM system increased the average indoor room temperature to 18.8 oC, which was 6.8% and 18.2% higher than the use of the TSC-only and a baseline without using PCM and TSC, respectively.

Prediction of inlet gas volume fraction of rotary vane pump under variable operational conditions with 1DCNN-TL model utilizing vibration signals

The Rotary vane pump (RVP) exhibits promising potential in the lubricating oil system of aircraft engines. The entrainment of air into the lubricating oil flowing through the pump affects the suction and discharge flow rates of the RVP. Therefore, understanding the inlet gas volume fraction (IGVF) of the RVP is crucial to assess its capability to deliver sufficient lubricating oil for ensuring the safe operation of aircraft engines. This study presents a one-dimensional convolutional neural networks (1DCNN)-based transfer learning (TL) (1DCNN-TL) prediction model to predict IGVF for the RVP using experimental data from gas-liquid two-phase flow in the RVP. The model is pre-trained using the vibration signals under a specific differential pressure between the pump inlet and outlet to enable predictions of the IGVF under varying differential pressures. The 1DCNN serves as pre-trained model for analyzing the outcomes of different transfer tasks. The effect of different frozen layer numbers on training time and prediction accuracy of the neural network is explored. Subsequently, the influence of varied source domain data on prediction accuracy is investigated, revealing that for optimal TL results, stable condition data at 200 kPa should be preferred as the source domain. Then the 1DCNN-TL prediction model of IGVF of RVP under variable operational conditions is determined. The results indicate varying iteration convergence rates of the pre-trained model under a differential pressure of 200 kPa across different transfer tasks, with a final goodness of fit exceeding 0.958 after fine-tuning the model. The model demonstrates the high prediction accuracy and applicability, which can contribute to improving the reliability and safety of aircraft engines.

Flow physics of a subcritical carbon dioxide jet in a multiphase ejector

Existing literature on ejectors, different researchers utilized different turbulence models by their choice, neither analyzing the physics of turbulence nor providing any sufficient optical diagnostics of the flow field. In this article, the physics captured by the Unsteady Reynolds Averaged Navier–Stokes (URANS) and Large Eddy Simulation (LES) are compared based on well-posed boundary conditions obtained experimentally from a carbon dioxide (CO2) vapor compression cycle with an error ≤2.5%. The experimental results utilized for this study are at Reynold’s number (Re) 1.2e5 at the high-pressure inlet (motive flow) maintaining CO2 in subcritical state. The low-pressure inlet (suction flow) is maintained at Re = 9.8e4 with CO2 in vapor state, providing a pressure lift ratio of 1.2 at the diffuser outlet. Comparison of flow topologies with different URANS models reveals that only standard, Shear Stress Transport (SST) k−ω, and Reynold’s Stress Model-Shear Stress Gradient (RSM-SSG) are the suitable URANS models capturing a linearly increasing anisotropy tensor component with increasing strain in the flow. LES also predicted the similar physics. However, standard k−ω overpredicted the suction pressure beyond the acceptable uncertainty limits, which made it inapplicable. For the first time, a spatio-temporal representation of the flow topology with LES revealed the actual jet morphology of a CO2 ejector. Specifically, finger-like structures are key features to entrain more surrounding warm fluid into the colder dense core fluid at the cost of destabilizing and breaking up the jet by stretching the streamwise vortices and obstructing the increase in pressure-lift ratio.

Quantitative study on the flow control of a 1:2 rectangular cylinder based on the leading-edge suction

The present study employed the leading-edge suction flow control on a 1:2 rectangular cylinder to control its unsteady aerodynamics. To study the suppression on aerodynamic forces, the surface pressures were measured at the Reynolds number of 1.28 × 104. A dimensionless suction momentum coefficient (Cμ) was defined to quantify the suction flow rate. The detailed flow visualization was conducted on the wake flows as well as the leading-edge separated flows to reveal the control mechanism. The proper orthogonal decomposition (POD) analysis was conducted on the wake flows to study the modal transformations. Results show that the leading-edge suction flow control could significantly affect the flow separation-reattachment characteristics and the present control processing could be divided into five stages with increasing Cμ. The lift fluctuation could reach a maximum reduction of 66.4%. Meanwhile, the flow separation at the leading edge was gradually suppressed and eliminated with increasing Cμ. The wake flow was compressed in the transverse region and suppressed in the turbulent kinetic energy (TKE) as well as the Reynolds shear stress (RSS), which should be responsible for the suppression on the lift fluctuation.

Study on the influence of collecting parameters of deep-sea seafloor massive sulfide on ore collecting characteristics

The commercialization of deep-sea mining has put forward strict requirements for ore collection output, ore collection efficiency, and environmental disturbance. However, the research of seafloor massive sulfide collection is in the initial stage. The influence of ore-collecting working parameters on the ore-collecting performance is not clear. In order to realize the commercial exploitation of deep-sea minerals, it is urgent to carry out the analysis and research on the influence of ore-collecting parameters on ore-collecting characteristics. The computational fluid dynamics-discrete element method is adopted in this paper to carry out numerical simulation research. Through the qualitative and quantitative analysis method, the influence law of six ore collecting parameters on ore collecting characteristics was analyzed. On this basis, the prediction model of ore-collecting characteristics and the optimal selection of ore-collecting parameters are proposed. Through the research, it is suggested to select 133.2 kg/s flow suction for ore collecting hard pipe; 60 rpm rotation speed is recommended for the mining head. It is recommended to select mining areas with the mineral density of 3000 kg/m3 for collection. The collection stage should be broken as far as possible to the 25 mm chip size. The recommended cutting depth is 224 mm if the strength and system metrics are met. The research of this paper provides a theoretical basis for the practice of deep-sea ore collection and has guiding significance for the selection of ore collection parameters, structural optimization design, and other engineering problems.

Effect of injector on flow characteristic and hydraulic performance in aero-fuel centrifugal pump

In the fuel system of an aircraft engine, aero-fuel centrifugal pumps are widely utilized as boost pumps. In this research, we propose the integration of an inlet injector with an aero-fuel centrifugal pump to optimize its flow characteristics and enhance performance. The key geometric parameters of the impeller, volute, and injector are meticulously designed. The effectiveness of our approach is validated through a combination of experimental and numerical analysis, which involves comparing simulation results with experimental data. The findings demonstrate that the presence of the injector significantly impacts the flow characteristics and hydraulic performance of the pump. Specifically, it effectively reduces flow losses in the specific channels of the impeller and volute. Furthermore, the injector enhances the regulation of the inlet flow fields by adjusting the inlet pressure and controlling the suction flow direction. Consequently, the pump’s efficiency is enhanced when equipped with the injector compared to its performance without it. Therefore, incorporating an injector in an aero-fuel centrifugal pump has a positive effect on regulating flow characteristics and improving hydraulic efficiency.

Numerical study of the coupling collection flow field and collecting mechanism of swirling flow and negative pressure suction flow in deep sea mining

The ore collection mechanism of seafloor massive sulfide has not been paid enough attention. In order to achieve collection efficiency, it is necessary to study the ore collection mechanism. Aiming at the ore collection model of the 'KTII' deep-sea mining vehicle, this paper carried out the analysis of the flow field characteristics of the coupled collection, the swirling flow collection and the negative pressure suction flow collection, and the role of each power source in the ore collection process. Finally, the relationship between swirling flow and negative pressure suction flow in the ore collection process is summarized, and the ore collection mechanism is analyzed. The results show that the rotation of the mining head will produce swirling flow, triggering the "inward winding effect", which can ensnare the ground surface fluid into the virtual cutting rotary cavity. The negative pressure suction flow of the collecting hard pipe can suction the liquid in the small-scale range of the throat surface. However, swirling flow and negative pressure suction flow both have advantages and disadvantages in collecting and the two power sources are complementary and inseparable. The research results of this paper have certain guiding significance for the engineering practice of deep-sea mining.

Experimental study on radial suction flow and its effect in water vortex unit

A water vortex unit is a non-contact adsorption unit that utilizes water as a flowing medium. Negative pressure is generated on the adsorbed surface through the high-velocity rotation of the fluid, resulting in suction force. In comparison to the air vortex unit, the water vortex unit exhibits a substantial increase in suction force and has the capability to deliver greater power. However, the presence of the central bubble in the water vortex unit weakens the suction force. To address the impact of the central bubble, a suction hole was introduced on the vortex unit to remove them. Experimental results indicate that solely removing the central bubble has almost no effect on the radial pressure gradients in the gap flow path and chamber center of the water vortex unit. However, in the cylindrical neighborhood, the radial pressure gradient increases, leading to a certain degree of improvement in suction force. Further increasing the suction flow rate induces inward radial flow within the vortex chamber. This flow field further enhances the suction force. To analyze the reasons for this pressure distribution, we indirectly obtained the radial velocity distribution by examining the relationship between the pressure gradient and tangential velocity. The results of the tangential velocity distribution indicate that the radially inward suction flow significantly increases the rotational velocity of the fluid in the chamber center, enhancing the centrifugal inertial effect. This further reduces the negative pressure, resulting in a significant improvement in the suction of the vortex unit.

Simplified modeling of scroll compressors with vapor injection

Semi-empirical models for predicting the suction flow rate, injection flow rate, input power consumption, and discharge temperature are proposed for scroll compressors with vapor injection. A data set containing four compressors wherein each compressor was tested over a range of operating conditions is used to evaluate the models. The fitted parameters of the models and the prediction errors of each data set are discussed. The accuracy and generalizability of applying the models to the same compressor with and without vapor injection are also discussed.

Proper Orthogonal Decomposition Based Response Analysis of Inlet Distortion on a Waterjet Pump

This study addresses the challenge of performance degradation in waterjet pumps due to non-uniform suction flow. Utilizing the Proper Orthogonal Decomposition (POD) method, it decomposes and reconstructs the flow features within a waterjet pump under non-uniform inflow into a series of modes ranked in descending order of energy. By analyzing the modes with dominant energy, which contain complex information about the flow field, it is revealed that modes 1 and 2 predominantly represent the formation of a concentrated vortex, whereas modes 3 and 4 illustrate its spatial offset. Notably, in the hub section, mode 3 exhibits a delayed flow separation caused by the reduction of circumferential vortex (CV), with a consequent lift in blade loading at the leading edge and a higher head compared to mode 1. In the shroud section, the delayed flow separation in mode 3 suppressed reverse flow and the concentrated separation vortex (CSV) and then increased the blade loading, ultimately enhancing the pump head. The findings provide significant insights into optimizing waterjet pump performance by detailing the interactions between various flow structures and pump components, effectively filling a knowledge gap in applying dimensionality reduction techniques within the distorted flow fields of water jet pumps.

Effects of bleed pressure on shock-wave/boundary-layer interactions in a transonic compressor stator with suction holes

Abstract This paper numerically investigated the influence of bleed pressure on the shock-wave/boundary-layer interaction in a transonic compressor stator with a row of suction holes. These suction holes are arranged on the suction surface in the spanwise direction. Six different bleed pressure ratios are studied at an inlet Mach number of 1.0. Results show that the reduction in the pressure loss increases as the bleed pressure decreases, and the maximum relative decline is 36.4 % when the flow loss caused by the suction flow path is taken into account. The bleeding of suction holes changes the shock wave structure, and the modified shock wave structure is three-dimensional. As the bleed pressure decreases, the tangential momentum of boundary layer increases. A strong spanwise variation in the boundary layer is observed downstream of the suction hole. Turning the flow direction and creating a favorable pressure gradient are key reasons for controlling boundary layer separation.

Passive control of the condensing flows in the three-dimensional steam turbine blade using a suction technique

A great amount of thermodynamic losses and mechanical damages in industrial equipment occur due to the condensation phenomenon and two-phase flows in such equipment. In this study, supercooled vapor suction has been passively used in the 3D (three-dimensional) steam turbine stationary blade. Supercooled vapor suction is one of the techniques used in turbines for resisting corrosion and erosion. For the supercooled flow suction, the design is as follows: an embedded channel inside the turbine blade in the nucleation zone, which has the utmost non-equilibrium mode; furthermore, the impacts of the location and surface of the channels devised in the turbine blade for supercooled vapor suction on the following parameters have been investigated: the two-phase flow, the suction ratio, condensation losses, erosion ratio, the average droplet growth, and kinetic energy. Based on the results, in the optimal case (case F), the condensation losses, erosion ratio, average droplet radius, and kinetic energy decrease by 3%, 24%, 6.5%, and 2%, respectively; also, the suction ratio is 3.6%. The present research reveals that the supercooled vapor suction, due to a decrease in the surface necessary for the condensation, decreases turbine blade corrosion and erosion. This fact can provide the turbine designers with beneficial information.

An Individual Barrier Enclosure Actively Removing Aerosols for Airborne Isolation: A Vacuum Tent.

Aerosol barrier enclosure systems have been designed to prevent airborne contamination, but their safety has been questioned. A vacuum tent was designed with active continuous suctioning to minimize risks of aerosol dispersion. We tested its efficacy, risk of rebreathing, and usability on a bench, in healthy volunteers, and in an ergonomic clinical assessment study. First, a manikin with airway connected to a breathing simulator was placed inside the vacuum tent to generate active breathing, cough, and CO2 production; high-flow nasal cannula (HFNC) was applied in the manikin's nares. Negative pressure was applied in the vacuum tent's apex port using wall suction. Fluorescent microparticles were aerosolized in the vacuum tent for qualitative assessment. To quantify particles inside and around vacuum tent (aerosol retention), an airtight aerosol chamber with aerosolized latex microparticles was used. The vacuum tent was tested on healthy volunteers breathing with and without HFNC. Last, its usability was assessed in 5 subjects by 5 different anesthesiologists for delivery of full anesthesia, including intubation and extubation. The vacuum tent was adjusted until no leak was visualized using fluorescent particles. The efficacy in retaining microparticles was confirmed quantitatively. CO2 accumulation inside the vacuum tent showed an inverse correlation with the suction flow in all conditions (normal breathing and HFNC 30 or 60 L/min) in bench and healthy volunteers. Particle removal efficacy and safe breathing conditions (CO2, temperature) were reached when suctioning was at least 60 L/min or 20 L/min > HFNC flow. Five subjects were successfully intubated and anesthetized without ergonomic difficulties and with minimal interference with workflow and an excellent overall assessment by the anesthesiologists. The vacuum tent effectively minimized aerosol dispersion. Its continuous suction system set at a high suction flow was crucial to avoid the spread of aerosol particles and CO2 rebreathing.

Suction and discharge flow controls of a co-rotating scroll hydrogen circulation pump

The purpose of this paper is to reveal the relationship between the suction, discharge flow control and self-designed co-rotating scroll hydrogen circulation pump (CSHCP) aerodynamic performance and irreversible flow loss. The effect of five suction angles and five discharge spoiler positions on the performance and flow loss of a CSHCP was firstly revealed using the computational fluid dynamics (CFD) three-dimensional numerical simulation method combined with entropy production (EP) theory and omega vortex identification methods. The optimized suction angle and discharge spoiler position of CSHCP were identified through comparing with isentropic and volumetric efficiency, EP, vortex distribution and flow pulsation intensity. Subsequently, the performance and flow loss difference of CSHCP are further distinguished before and after optimization of suction and discharge spoiler structure under designed or variable rotational velocities. The results demonstrate that the optimized suction angle and discharge spoiler position angle are 22.5° and 45°, respectively. After the combination optimization of suction and discharge spoiler structure, the total EP and discharge temperature pulsation intensity of CSHCP are reduced by about 13.2% and 67.5% respectively. The research results provide a reference for the efficient and stable operation of HCP for fuel cell system.

Experimental and Numerical Investigation of Cavitation Assessment for Runner Blades in a Francis Turbine

Cavitation in hydro turbines causes component deterioration that requires continuous and costly maintenance in the hydroelectric power generation stations. The Tarbela Dam Hydel Project (TDHP) in Pakistan is facing a cavitation problem in the Francis Turbine components, such as the runner and draft tube. Simulation work has been performed to examine and quantify the cavitation rate as a function of the suction head (SH) and flow velocity (FV) by utilizing a homogeneous cavitation model. The result shows that pressure fluctuation is maximum for overcrowded conditions and minimum for rated load conditions. Moreover, a higher cavitation rate is found for the part and overcrowded conditions compared to the rated load condition. Additionally, the cavitation rate becomes 50% higher when the SH increases from 5.54 to 12.34 m. Moreover, SEM results have verified the CFD results that higher FV and SH enhance the cavitation rate. Furthermore, the numerical work is validated by simplified hydrofoil geometry. The computational fluid dynamics results presented a good arrangement with the experimental data.

Wind Flow and Its Interaction with a Mobile Solar PV System Mounted on a Trailer

Efficient implementation of clean energy technologies is paramount, with mobile solar PV systems on trailers (MSPTs) emerging as pivotal solutions, particularly in regions with limited power grid access. This endeavour is vital for meeting escalating electricity demands and aligning with the UN Sustainable Development Goal (SDG), aimed at ensuring dependable and sustainable energy provision in developing countries. This study investigates the aerodynamic behaviour of a designed MSPT using numerical simulation and experimental methods, thereby offering optimization potential for MSPT design and enhancing overall performance and reliability. Specifically, the study focuses on the effects of wind velocity and tilt angles on the drag and lift forces, as well as drag and lift coefficients on the panel used in the MSPT system. The overall wind force on the entire MSPT, including nine large solar PV panels, is scrutinised, considering combined wind flow and system geometry effects. The numerical investigations were conducted using ANSYS-Fluent software (version 2022/R2) and experimental testing was performed within the C15-10 Wind Tunnel, utilizing scaled-down models to validate the accuracy of the simulation. The findings from the numerical investigations showed an increased turbulence caused by gaps between panels, resulting in almost 62% higher suction flow velocity and 22% higher suction pressure compared to a single panel. Drag and lift forces on the entire MSPT were approximately 6.7 and 7.8 times greater than those on a single panel with the same 30-degree tilt angle, respectively. The findings revealed that scaling forces on a single panel is insufficient for accurately predicting the aerodynamic forces on the entire MSPT. The insights and the knowledge from this study pave the way for further improvements in mobile solar PV technology.

Optimizing jet pump efficiency via drag reducing polymers and enhanced efficiency definitions

Liquid jet pumps are widely used in various industrial applications for fluid mixing, circulation, and transport. The efficiency and performance of liquid jet pumps play a crucial role in determining their overall effectiveness and economic viability. The performance of liquid jet pumps is primarily affected by parameters such as motive fluid pressure, nozzle design, and entrainment ratio. Liquid jet pumps exhibit a notable drawback in terms of comparatively lower efficiency when compared to alternative pump types. The reduced overall efficiency of liquid jet pumps stems primarily from energy dissipation incurred during the entrainment process. To address this obstacle, a water-water loop system was implemented in conjunction with a liquid jet pump, followed by the introduction of drag-reducing polymers (DRPs) into the suction flow of the liquid jet pump using a specific configuration. This configuration led to a significant reduction in drag within the liquid jet pump, raising its efficiency in some cases from 13.8% to 26.7% with a drag reduction of 46%, subsequently improving its overall performance. The resulting enhancement was evaluated using various efficiency models documented in the existing literature to comprehensively assess the overall performance of the liquid jet pump. A new interpretation of jet pump efficiency has been shared, along with a comparison of the various efficiencies.

Design improvement for suction shape in rotary compressor

Rotary compressors applied to heating and cooling cycles accounts for a large proportion of the total energy consumed in the system. Therefore, improving compressor efficiency is crucial in order to reduce energy consumption. Design review and improvement efforts have primarily focused on compression and discharge parts with high pressure. However, due to the limitations in design improvements for the compression and discharge parts, enhancements for other components are necessary to further increase compressor efficiency. In this study, the design of the suction part of the rotary compressor was modified using FSI (Fluid-Structure Interact) analysis scheme. In order to improve the design of the suction shape, new suction shape types were devised as alternatives to the existing through type. Both the newly devised C-type and E-type suction shapes presented an increase in cooling capacity due to reduced suction resistance, with the E-type demonstrating greater improvement compared to the C-type. Consequently, a verification of the effect based on the detailed design dimensions was further conducted for the E-type suction shape. The final selected improved model increased the suction flow rate by approximately 2.5% compared to the base model. This indicates that significant improvement for the compressor efficiency can be achieved through modifying designs in parts other than the compression and discharge sections. In addition, a design improvement process was established to analyze internal flow using FSI analysis.