High Discharge Pressure Research Articles

Study on the impact of turbulent spatiotemporal propagation in the outlet passage on the performance of vertical axial flow pumps.

Abstract Pumping station engineering is crucial for our country’s national economy as a part of water conservancy infrastructure. The vertical axial flow pump commonly used in pumping station construction features a high flow rate and low discharge pressure. Understanding the impact of turbulence on the flow of water entering and leaving the pump unit is crucial for the efficient and reliable operation of a pumping station. This paper examines the internal flow and hydraulic characteristics of the device for vertical axial flow pump at a pumping station through numerical simulation technology and experimental validation. It is inferred that turbulent flow develops in the outlet flow passage while the pump device is currently functioning, impacting the impeller’s outlet bend and guide vane. This leads to the formation of vortices, backflow, and folding flow at the guide vane and outlet bend. As water flows out through the outlet passage, bias and backflow develop, causing erosion on both sides of the outlet pool and impacting the pump unit’s overall head and efficiency.

(Invited) PEM Water Electrolysis Stack Development and Related Characterization Tools

For decades, proton-exchange membrane (PEM) water electrolysis (WE) has been mainly used for oxygen generation in anaerobic environments. Over the past two decades, however, it has been increasingly used for hydrogen generation in the industrial sectors at various scales. The PEMWE technology is also considered a key in the ongoing energy transition, if the process of hydrogen generation by means of WE is linked to renewable energy sources, such as wind, solar, etc.The following key elements enable the operation of a PEM WE plant for hydrogen production: a PEM-based WE stack and the balance of plant. The related system includes, but not limited to such key modules as the water and oxygen management systems, hydrogen gas management system, water input system, safety system, power electronics and electrolysis cell stack power supply, control system, and some other.A WE stack comprises several cells connected in series with electrically conductive bipolar plats and end plates. General design principles for the stack involve reducing efficiency losses, while aiming at lower costs and increase in durability. WE stacks should be designed in such a way, that an even current distribution is maintained, the water feed is optimized, suitable compression ratios are achieved, and preferably high discharge pressure of hydrogen can be enabled. For the stack level, in simple terms, efficiency is benchmarked by the total applied voltage, which includes the Nernst potential, anode and cathode overpotentials, and ohmic overpotentials due to the membrane ionic resistance and interfacial resistance at given current density. Overpotential represents inefficiencies in a cell stack, and some of stack design efforts focus on reducing these overpotential contributions. However, a compromise has to be found between (a) costs reduction challenges (that are often associated with the reduction of PGM-based catalyst loading, attempts to replace Ti as a key material for the bipolar plates, and the less expensive SPE membrane), (b) sufficient durability, (c) performance of the stack, (d) increase in power density of a stack.This talk will focus on the WE stack, and its subcomponents review, as well as characterization methods for both, a single cell and a stack and also challenges of the large-scale stack manufacturing. The key components of the WE stack include ion-conductive solid polyelectrolyte membranes (SPE), anode and cathode catalyst layers (CL), bipolar plates and current collectors/ gas diffusion layers (porous transport layers).In order to gain fundamental understanding of the relationships between electrical loses, degradation of the stack components and strategies to increase power density of the stacks, advanced characterization and modelling tools need to be used. These include, but not limited to electrochemical impedance spectroscopy (EIS), current interrupt (CI), dynamic compression measurements with piezoelectric senor plates, current mapping, gas cross-over analysis, computational fluid dynamics (CFD) simulations modelling, various visualization tools, etc. For example, CFD could assist in understanding and improving fluid flow dynamics in a WE stack as it is a complex challenge that requires a detailed examination of the geometry, channel design, and operating conditions within the stack. As for EIS, the usage of the distribution of relaxation times (DRT) approach would potentially allow to focus on the direct analysis of the data rather focusing on the equivalent circuit development.Approximately 15 years ago the South African Government approved a national program HySA: Hydrogen South Africa, which resulted in the development of the expertise and capacity to conduct research, development, and earlier commercial activities around green hydrogen production by means of water electrolysis. These activities include the development of local IP at the components, stack, and system levels.

Improvement of Thick Coal Seam Gas Drainage Efficiency Using Highly Pressurized Multidischarge CO2 Gas Fracturing Technique.

Thick coal seam fracture stimulations were conducted to enhance pre-gas drainage efficiency through the use of a highly pressurized multidischarge carbon dioxide gas fracturing technique. This method also offers potential as a strategy for carbon dioxide sequestration, aiding in the reduction of atmospheric carbon dioxide levels and thereby contributing to the fight against climate change. This paper discusses findings from both field experiments and numerical simulations. Data from the field show that the multidischarge fracturing approach significantly improves permeability in thick coal seams, thereby boosting gas drainage effectiveness. Additionally, the impact of increasing the number of fracturing devices is more pronounced at distances of 2.5 or 7.5 m from the borehole but becomes more complex at 12.5 m or further. The numerical simulations reveal that this technique primarily enhances coal seam gas drainage by improving the seam permeability and establishing a gas pressure gradient within the seam. It is noted that the radius of failure around the borehole wall expands with higher discharge pressures, while the radius of effective drainage narrows as the gap between discharge heads increases. Moreover, adding more discharge sets significantly influences the deformation and permeability of the coal seam within a 5 m radius of the fracturing borehole, but the influence is not obvious after 10 m from the fracturing borehole.

(Invited) Component Design and Electrode Optimization for AEM Electrolyzers

The massive international investment in water electrolysis has accelerated the need to reduce cost and increase durability. In recent years, Anion exchange membrane electrolyzers (AEMELs) have been touted as a possible low-cost option to supplant traditional alkaline electrolyzers and proton exchange membrane electrolyzers because they promise to combine the benefits of both – namely high current density operation, high discharge pressure, the use of noble-metal free catalysts, and the ability to use a wider range of materials for other cell components. As AEMELs are still early in their developmental stage, much of the reported work in the literature has dealt with the development of new catalysts or membranes for these devices and have worried less about engineering aspects of AEMEL design such as loading optimization, the structure and composition of the porous transport layers (PTL), the balance of IEC between the cathode, membrane and anode, etc. This presentation intends to take the audience through a systematic optimization of the anode and cathode electrodes for AEMELs. Some of the variables to be discussed are: i) IEC and cross-linker content of the ionomers; ii) ionomer physical structure; iii) catalyst loading; iv) PTL density and thickness; and v) number of layers that comprise the catalyst layer. The balance and sometimes compromise between performance and durability will also be discussed. By the end of the presentations of electrodes will be demonstrated that were integrated into AEMELs and are able to show very low voltage operation on both deionized water (1.9 V @ l.0 A/cm2) and 0.3 M KOH (1.65 V @ 1.0 A/cm2 and < 2 V @ 3.0 A/cm2) as well as stable operation for as much as 720 hours (30 days).

Energetic and entropy analysis of a novel transcritical CO2 two-stage compression/ejector refrigeration cycle for shipboard cold chamber

The adverse effects of global warming and climate change require critical measures for marine refrigeration technology because of its impact on GHG emissions. A novel transcritical CO2 two-stage compression/ejector refrigeration cycle for shipboard cold chamber is proposed in this research. A comparative analysis was conducted between the basic transcritical CO2 two-stage compression cycle and the cycle equipped with a two-phase ejector considering the COP. Meanwhile, the refrigeration cycle was analyzed using entropy analysis to elucidate the distribution of irreversible losses in each component of the two-stage compression/ejector refrigeration cycle, and the effects of system parameters such as the evaporating and gas cooler outlet temperatures as well as the intermediate and discharge pressures on the cycle were investigated. The results showed that the ejector had the largest power capability loss, accounting for 26.95 % of the overall system, which is followed by the low pressure compressor with 26.06%. The COP of basic and ejector system significantly increase as the gas cooler outlet temperature and intermediate pressure decrease as well as the evaporating temperature increases. Furthermore, the entropy production of the system components decreases gradually with increasing evaporating temperature, with the greatest reduction in the ejector. In addition, the entropy production of the two-phase ejector remains constant with the increase of the high pressure side discharge pressure and gas cooler outlet temperature.

Fluid dynamic analysis of a cryogenic piston pump

Cryogenic piston pumps are commonly found in cryogenic systems to pressurize low-temperature liquefied fuels, such as liquified natural gas (LNG) or hydrogen, which are then gasified and stored in high-pressure vessels. The main challenges to be tackled in the design of these machines concern the low operating temperatures, high discharge pressures, and especially the need to avoid liquid evaporation, as this can lead to a reduction of volumetric efficiency or even to the shutdown of the pump. Two effects can cause the formation of vapor bubbles: cavitation, i.e., when the static pressure falls below the saturation value during the suction phase, and evaporation due to a temperature increase of the cryogenic liquid.In this study, a numerical analysis of a cryogenic single-piston pump is carried out. In the first part of the activity, the suction phase is studied through three-dimensional, steady-state CFD simulations. The performance of the pump in terms of pressure losses is evaluated and possible improvements to the suction geometry are identified.Then, two-phase steady-state Eulerian-Eulerian simulations are performed. The Rayleigh-Plesset model is used in order to evaluate the onset of cavitation. The minimum inlet pressure conditions that avoid cavitation are identified for two different geometries underlining the positive effect of the introduced modifications. Results show that the methodology applied in this work can lead to improvements in cryogenic pump design, reducing the static pressure losses and hence limiting the risk of cavitation.

Experimental investigation on the start-up behaviors of a Joule–Thomson refrigeration system with pressure control

• Start-up behaviors of the J-T refrigeration system with pressure control were explored. • Reducing the pressure control time could accelerate pull-down rate. • Increasing control pressure and expansion valve opening decreases pull-down time. • Reducing compressor speed and R1150 concentration could reduce pull-down time. The excessively high discharge pressure of mixture-based Joule–Thomson (J–T) refrigeration system for low-temperature freezers at the start-up process without active control leads to the reduction of operation reliability of compressors. Start-up characteristics of a J–T refrigeration system with an expansion tank for pressure control were investigated in this study. The binary mixture R1150/R600a was selected as the working fluid, and influences of the control pressure, compressor speed, throttle valve opening, and mixture concentration on the system’s dynamic performances were experimentally explored. Results demonstrated that the discharge pressure could be effectively limited below the compressor’s safety pressure with an expansion tank. Meanwhile, the close relationship between pull-down rate and time of the pressure control phase was associated with the control pressure, compressor speed, throttle valve opening, and mixture concentration. The pull-down rate can be accelerated by increasing the control pressure and throttle valve opening and reducing the compressor speed and the R1150 concentration at the start-up process. The excessively rich R1150 concentration caused the continuous action of the pressure switch and the malfunction of the low-temperature freezing at an acceptable time range. The build-up of the heat recuperation played a significant role in pressure control time and freezing temperature reduction rate.

Virgin olive oil processing by high voltage electrical discharge or high hydrostatic pressure

We test the application of two emerging technologies to virgin olive oil (VOO) processing. high voltage electrical discharge (HVED) was tested at 20 kV and about 100 kJ/kg of VOO. High-pressure processing (HPP) was applied for 360 s at about 600 MPa. VOO quality indices were evaluated immediately after treatment and after 6 months. The HPP treatment was found to have no negative influence on any aspect (p > .05 according to General Linear Model and the Tukey HSD test). The HVED treatment did not affect conventional quality indices (p > .05), but was consistent with the appearance of secondary oxidation products (anisidine value increment of about 50% and rDigs increment of roughly 200%, both at p ≤ .05), a significant fall in biophenol concentrations roughly from 5 to 10% at p ≤ .05; and a decrease of about 15% at p ≤ .05 in positive volatiles. Overall, HVED processing appears to negatively impact VOO quality. Novelty impact statement For the first time, high voltage electrical discharge (HVED) has been tested on virgin olive oil (VOO) in comparison to high-pressure processing (HPP) over a storage period While HPP was entirely safe for VOO quality, HVED determines a potential detrimental effect Our findings support the application of these technologies to food containing VOO, or for its direct treatment, for instance, to protect against microbial spoilage.

Experimental research on refrigeration performance of air conditioning system of pure electric passenger cars with economizer

Aiming at solving the problems of the high compressor discharge temperature, the high discharge pressure, the insufficient cooling capacity, and the reduced system efficiency in the air-conditioning system of pure electric passenger cars in the summer high temperature environment, this paper develops a low pressure economizer using the principle of the quasi-two-stage compression cycle. The heat pump air conditioning system of the air-supplemented pure electric passenger car is set up to study its refrigeration performance. The results show that in a high environment temperature of 50?C, compared with the non-supplemented system, the discharge temperature in the low pressure supplemental gas system drops by 13.54?C, the refrigeration capacity reduces by 2.0%, the compressor power drops by 3.4%, and the refrigeration coefficient increases by 1.4%.

The Piston Ring-Cylinder Bore Interface Leakage of Bent-Axis Piston Pumps Based on Elastohydrodynamic Lubrication and Rotation Speed

The bent-axis piston pump is the core component of electrohydrostatic actuators (EHA) in aerospace applications, and its wear of key friction interfaces is greatly related to the healthy operation of pumps. The leakage of the piston ring-cylinder bore interface (PRCB), as the important part of the return oil flow of the pump house that commonly assesses the wear of key friction interfaces in piston pumps, is changed with the rotation speed. Thus, the wear of key friction interfaces is usually inaccurate by using the leakage of PRCB. In order to obtain the relationship between the PRCB leakage and the rotation speed, an elastohydrodynamic lubrication model is proposed. First, the proposed model includes a minimum film thickness model of PRCB to analyze the dynamic change of oil film of PRCB when subject to the elastohydrodynamic lubrication. After that, a mathematical model of PRCB is induced by combining the minimum film thickness model with the flow equation, which helps produce the effects of the oil film on the leakage of PRCB. The proposed model is verified by numerical simulation and experiment. The results show that the leakage of PRCB has a negative effect on the return oil flow of the pump case in the range of rotation speed of 700–1300 r/min and discharge pressure of 10–20 MPa. Furthermore, the leakage of PRCB is proportional to the rotation speed, but the return oil flow of the pump case is decreased. The effects of rotation speed are enhanced under the high discharge pressure conditions.

Performance analysis of a U-Vane compressor

A new rotary compressor, named ‘U-Vane compressor’ (UVC) has been introduced with the motivation of reducing the size of the cylinder and housing in a swing compressor. The compressor can be used for air and refrigerant compression. In this paper, the dynamics, internal leakages and frictional losses aspects of UVC are modelled. A physical prototype has been fabricated and measurements have been conducted with an open air-test-circuit for verification of the mathematical model. Good agreement is obtained between the predicted and measured power inputs with an average discrepancy of 3.8%. However, the discharge mass flow rate tends to be under-predicted at high operating speeds and low discharge pressures situations. Nevertheless, the mathematical model is capable of predicting the performance of UVC with acceptable accuracy.

Multistage aqueous and non-aqueous extraction of bio-molecules from microalga Phaeodactylum tricornutum

A multi-step aqueous and non-aqueous extraction procedure was applied to recovery bio-molecules from Phaeodactylum tricornutum. The process include that physical pre-treatments (high voltage electrical discharges (HVED, 40 kV/cm, 1–8 ms, HVED samples) or high pressure homogenization (HPH, 1200 bar, 10 passes, P samples)) (1st step); aqueous extraction (2nd step); pigments extraction in ethanol (3rd step); and lipids extraction in CHCl3/MeOH (4th step). The extractability of ionics, carbohydrates, proteins, pigments and lipids for untreated, HVED and P samples were evaluated. The results evidenced that HVED allowed selective extraction of water soluble ionic products at 1st and 2nd steps. The maximum ionic concentrations were found for HVED samples. However, P samples resulted in higher contents of extracted components as compared to HVED samples (≈1.5-fold of carbohydrates, ≈2.5-fold of proteins, ≈5-fold of carotenoids, and ≈3-fold of chlorophylls). Moreover, the non-aqueous extraction (3rd and 4th steps) allowed supplementary extraction of pigments and lipids. Industrial relevancePre-treatments by high voltage electrical discharge (HVED) or high pressure homogenization (HPH) allowed effective extraction of different bio-molecules from microalga biomass. The combination of HVED/HPH, aqueous and non-aqueous extraction allowed selective recovery of target molecules. The paper also presents a multistage extraction procedure allowed reducing the amount of toxic solvents, increasing the extraction efficiency, and reducing the energy consumption. These approaches opened the doors to high-efficiency recovery of valuable compounds from microalgae relevant for industrial application.

Dynamic characteristics of a swing compressor for an air conditioning system at different discharge pressures

Abstract Swing compressors have received significant attention due to their ability to function under the high discharge pressure resulting from the use of alternative refrigerants. The goal of this study is to analyze the dynamic characteristics of a swing compressor under different discharge pressures. D'Alambert principle is used to analyze the dynamics of compressor components, and then the dynamic characteristics and mechanical properties of a swing compressor are investigated under different discharge pressures. The results show that with increased discharge pressure, the swing compressor exhibits less of a decrease in mechanical efficiency than the rolling piston compressor. In a working cycle, the performance of the swing compressor during the discharge and mixing phases is limited by greater force and wear. In addition, the sum of the friction losses between rotor and eccentric, eccentric shaft and bearings, and swing rod and guide accounts for more than 80% of the total friction loss. The results provide guidance for the structural design of the swing compressor.

A new integrated numerical modeling approach toward piston diaphragm pump simulation: Three-dimensional model simplification and characteristic analysis

Piston diaphragm pumps are used worldwide to transport abrasive and aggressive slurries against high discharge pressures in the mining, mineral processing, and power industries. Intermittent suction and drainage of the diaphragm, however, can lead to pulsating output pressure, which has caused major problems in the application of these pumps. To improve the accuracy of simulations of piston diaphragm pumps and to enable better simulation of their pressure pulsation behavior, it is necessary to carry out a three-dimensional fluid–structure interaction simulation of the pump fluctuation characteristics. This article proposes a simplified simulation model based on the periodic motion characteristics of a piston diaphragm pump, where a ZMB240 piston diaphragm pump serves as the research object. By simplifying the numerical simulation of the model, we are able to analyze the deformation characteristics and the fluctuation characteristics of the piston diaphragm pump under different initial conditions for the pressure-stabilizing air chamber.

Experimental investigation of a prototype R-600 compressor for high temperature heat pump

This research experimentally investigates a prototype compressor in a high temperature heat pump for industrial waste heat recovery from 50 °C to heat delivery at 115 °C. Compressors are the limiting component in the development of high temperature heat pumps due to the high discharge pressure and temperature. The prototype compressor is tested with butane due to its favourable thermodynamic properties within the operating conditions. The compressor allows the heat pump to provide heating for industrial processes such as pasteurization, drying, sterilization and other processes which require high temperature heat. The heat pump will replace the heating capacities of low-pressure steam boilers. It will also provide cooling for industrial waste heat or other cooling demands, replacing cooling capacities from cooling towers. The experimental setup consists of a 20 kW heat pump designed with the flexibility for multiple operating conditions applicable to different industrial applications. The compressor is designed to enable suction and discharge temperatures up to 80 °C and 140 °C respectively. It is found to have a total compressor efficiency of 74% and a volumetric efficiency of 83%. The results showed good operating parameters (temperature, pressure) and the potential for even higher temperature heat delivery.

A comparative performance analysis of direct, with battery, supercapacitor, and battery-supercapacitor enabled photovoltaic water pumping systems using centrifugal pump

To operate centrifugal pump against higher discharge pressure and to achieve specific speed for delivering the water, the level of irradiance required is quite high. Therefore, by knowing the operating pressure this problem may be minimized by using energy storage devices like battery or supercapacitor operated in parallel with the SPV module. Here is the need to select a proper configuration of solar PV water pumping system (SPVWPS) using energy storage devices for the economic application. Therefore, a new approach is made towards studying different configurations of 7SPVWPS with battery and supercapacitors under varying discharge pressure and evaluate the performance parameters. Four different configurations of SPVWPS using centrifugal pump are considered, namely, directly coupled, with battery, with the supercapacitors and with a battery-supercapacitor hybrid, to determine the optimum configuration for higher system performance. The experiment have been carried out on a small scale SPVWPS with 2 m and 3 m dynamic head of the pump on sunny days at Haldia, India. The comparison of the performance for the different configurations have been reported. The study reveals that the supercapacitor based configuration give highest instantaneous efficiency. The centrifugal pump powered by SPVWPS using battery delivers a maximum of 2964 L per day for 2 m dynamic head whereas for 3 m dynamic head SPVWPS using supercapacitor delivers a maximum of 1826 L per day. An economic comparison is also done for the different topologies.

High Current Audio Frequency (Ion/Electron) Source

Simple technique is used for production of high ion / electron current from an Audio Frequency (AF) (10 – 50 kHz) discharge source. Small size plasma bottle (ϕ = 30 mm, L = 35 mm) with capacitive electrode of AF antenna immersed inside it. The source is working at high discharge pressure ~ 0.2 Torr., without the need of high vacuum system. The extraction system is concentric hemisphere electrodes which allow self-beam focusing by adjusting the beam minimum size and its position from the source exit. The ion species used are nitrogen and argon, the discharge power (100 – 500 W) and the extraction voltage is (100 – 600 V). The AF discharge shows a high discharge cross-section of ionization at certain frequency of the AF supply. The behavior of the AF discharge acts similar to the D.C. discharge explained by known Paschen's curve. The maximum extracted Ar electrons and ions currents are 10 and 2.4 mA respectively, while for Nitrogen are 12.5 and 2.7 mA. Beam simulation by SIMION program shows a good agreement with the analytical study of the hemi-sphere electrodes extraction system.

Экспериментальное исследование рабочих процессов тихоходных длинноходовых бессмазочных поршневых компрессорных ступеней при высоких отношениях давлений нагнетания к давлению всасывания

Экспериментальное исследование рабочих процессов тихоходных длинноходовых бессмазочных поршневых компрессорных ступеней при высоких отношениях давлений нагнетания к давлению всасывания

Experimental comparison between R409A and R437A performance in a heat pump unit

AbstractThis paper reports an experimental comparison between the use of the refrigerants R409A and R437A in a heat pump unit designed and developed to work with R12. Although the use of both refrigerants in new equipments were abolished in EU and US according the new F-Gas Regulation of EU and SNAP, they still being used as options for R12 in old equipments, especially in developing countries. Both refrigerants were studied for the same test conditions, according to two groups of tests: group A (variation of the heat source temperature) and group B (variation of refrigerant flow rate). The results obtained showed that the R437A presents a higher discharge pressure and a lower discharge temperature. The heating and cooling capacities of both refrigerants were similar, as well as the exergetic efficiency. For the group A of tests the COP of both refrigerants was similar and for the group B of tests the R409A presented an average COP 15% higher. According to the results obtained it is recommended the use of R409A in old equipments (as transition refrigerant) until the acquisition of equipments operating with refrigerants with low-GWP becomes technically and economic feasible.

Extraction of ions and electrons from audio frequency plasma source

Herein, the extraction of high ion / electron current from an audio frequency (AF) nitrogen gas discharge (10 – 100 kHz) is studied and investigated. This system is featured by its small size (L= 20 cm and inner diameter = 3.4 cm) and its capacitive discharge electrodes inside the tube and its high discharge pressure ∼ 0.3 Torr, without the need of high vacuum system or magnetic fields. The extraction system of ion/electron current from the plasma is a very simple electrode that allows self-beam focusing by adjusting its position from the source exit. The working discharge conditions were applied at a frequency from 10 to 100 kHz, power from 50 – 500 W and the gap distance between the plasma meniscus surface and the extractor electrode extending from 3 to 13 mm. The extracted ion/ electron current is found mainly dependent on the discharge power, the extraction gap width and the frequency of the audio supply. SIMION 3D program version 7.0 package is used to generate a simulation of ion trajectories as a reference to compare and to optimize the experimental extraction beam from the present audio frequency plasma source using identical operational conditions. The focal point as well the beam diameter at the collector area is deduced. The simulations showed a respectable agreement with the experimental results all together provide the optimizing basis of the extraction electrode construction and its parameters for beam production.