scholarly journals Methods of Determining Pressure Drop in Internal Channels of a Hydraulic Motor

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5669
Author(s):  
Pawel Sliwinski ◽  
Piotr Patrosz
Keyword(s):  
Pressure Drop ◽  
Experimental Studies ◽  
Experimental Tests ◽  
High Flow ◽  
Low Flow ◽  
Hydraulic Motor ◽  
Flow Rates ◽  
Pressure Losses ◽  
Face To Face ◽  
New Methods

In this paper, new methods for determining the pressure drop in internal channels of a hydraulic motor are proposed and described. Mathematical models of pressure losses in internal channels have also been described. Experimental tests of the satellite motor were carried out according to one of the proposed methods. The tests were carried out for two liquids, i.e., water and mineral oil. Experimental studies have shown that at a high flow rate in the motor supplied with water the pressure losses are a dozen or so percent greater than in the motor supplied with oil. However, at low flow rates is the inverse, that is, the pressure losses in the motor supplied with water are about ten percent lower than in the motor supplied with oil. The CFD calculation of the pressure drop in the internal channel of the motor was also conducted. It was assumed that holes in the commutation unit plate are placed face to face and that the liquid did not cause changes in the working chambers’ volume. In this way, it has been proven that those simplified assumptions can have up to a 50% difference in relation to the experimental tests.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

Leach Behavior of SRL TDS-131 Defense Waste Glass in Water at High&Low Flow Rates

1983 ◽  
Vol 26 ◽  
Author(s):  
Aaron Barkatt ◽  
William Sousanpour ◽  
Alisa Barkatt ◽  
Morad A. Boroomand ◽  
Pedro B. Macedo
Keyword(s):  
Contact Time ◽  
Protective Layer ◽  
High Flow ◽  
Low Flow ◽  
Matrix Elements ◽  
Flow Rates ◽  
Low Concentrations ◽  
Controlling Mechanism ◽  
The Matrix ◽  
Leach Behavior

ABSTRACTLeach tests carried out on SRL TDS-131 Defense Waste Class indicate that at high flow rates the controlling mechanism is simple corrosion. The matrix elements (Si, Al) are leached out at rates similar to those of the leaching of the alkalis and of boron, and the leaching process is nearly linear with time. At slow flow rates (below 1 m/yr) leaching becomes controlled by the build-up of a protective layer. Al and most of the Si remain in the leached surface layer. The leach rates decrease in the course of the test before leveling off at constant values which are almost inversely proportional to the contact time, indicating that leachate concentrations have become solubility-limited. The low concentrations observed at this stage indicate the formation of alteration products.

scholarly journals Adapting the Forchheimer equation for the flow of air through wheat straw beds

2016 ◽  
Vol 20 (suppl. 2) ◽  
pp. 463-470
Author(s):  
Djordjije Doder ◽  
Biljana Miljkovic ◽  
Borivoj Stepanov ◽  
Ivan Pesenjanski
Keyword(s):  
Experimental Investigation ◽  
Pressure Drop ◽  
Wheat Straw ◽  
Measurement Methods ◽  
High Flow ◽  
Biomass Combustion ◽  
Inertial Effects ◽  
Forchheimer Equation ◽  
Flow Rates ◽  
Straw Bale

The paper presents the results of an experimental investigation of air pressure drop while flowing through wheat straw beds. According to Darcy?s law, the smaller the porosity of the bed is, the bigger the pressure drop will be. The investigation was conducted using three different porosities (or three bed densities), and for two different air flow rates. After determining porosity (which is directly measurable), the permeability of straw could be found. For high flow velocities, such as the velocity of air flowing through a straw bale, the Forchheimer equation becomes more relevant as a correction of Darcy?s law with inertial effects included. Otherwise, the permeability tensor depends only on the geometry of the porous medium. With permeability known, the Forchheimer equation coefficients can be easily estimated. These results may be important for the future development of efficient biomass combustion facilities. The measurement methods and facility characteristics are described in more detail.

scholarly journals The Influence of Water and Mineral Oil On Volumetric Losses in a Hydraulic Motor

2017 ◽  
Vol 24 (s1) ◽  
pp. 213-223 ◽  
Author(s):  
Pawel Śliwiński
Keyword(s):  
Mathematical Model ◽  
Rotational Speed ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Mineral Oil ◽  
Hydraulic Motor ◽  
Small Constant ◽  
Influence Of Water ◽  
The Difference ◽  
Lubricating Properties

Abstract In this paper volumetric losses in hydraulic motor supplied with water and mineral oil (two liquids having significantly different viscosity and lubricating properties) are described and compared. The experimental tests were conducted using an innovative hydraulic satellite motor, that is dedicated to work with different liquids, including water. The sources of leaks in this motor are also characterized and described. On this basis, a mathematical model of volumetric losses and model of effective rotational speed have been developed and presented. The results of calculation of volumetric losses according to the model are compared with the results of experiment. It was found that the difference is not more than 20%. Furthermore, it has been demonstrated that this model well describes in both the volumetric losses in the motor supplied with water and oil. Experimental studies have shown that the volumetric losses in the motor supplied with water are even three times greater than the volumetric losses in the motor supplied with oil. It has been shown, that in a small constant stream of water the speed of the motor is reduced even by half in comparison of speed of motor supplied with the same stream of oil.

Experimental Tests With Centrifugal Pumps: Degradation of Performance, Instability and Dynamic Phenomena With Non-Newtonian Suspensions of Kaolin in Water

2019 ◽  
Author(s):  
Matteo Occari ◽  
Enrico Munari ◽  
Valentina Mazzanti ◽  
Michele Pinelli ◽  
Francesco Mollica ◽  
...  
Keyword(s):  
Experimental Tests ◽  
Newtonian Fluids ◽  
Low Flow ◽  
Time Varying ◽  
Centrifugal Pumps ◽  
Strong Reduction ◽  
Flow Rates ◽  
Specific Speed ◽  
Dynamic Phenomena ◽  
Newtonian Behavior

Abstract The performance of pumps when working with non-Newtonian fluids significantly change with respect to water. In several experimental tests with non-Newtonian fluids, significant deration of head and the presence of head instability were observed. The present work aims to better understand this phenomenon since the reasons that originate it are not clear. Two small size centrifugal pumps were experimentally tested with different mixtures of kaolin-in-water, which showed a verified non-Newtonian behavior. The rheology of the mixtures and the particle size distribution of kaolin powder were measured to characterize the fluids. Similar to previous tests, a strong reduction of head and the appearance of instability were observed at low flow rates and, in some cases, also at higher flow rates. This behavior was related to the presence of air trapped into the fluid that, within the pump, generated a phenomenon known as gas-locking, which in literature it has been studied in detail with water but not with non-Newtonian fluids. Moreover, in some working conditions, non-stable time-varying phenomena are observed and their consequence on performance commented. Comparing the two pumps, characterized by a similar specific speed but by a different geometry, the head drop manifested itself with different intensity.

Effects of Taper Configurations on Heat Transfer and Pressure Drop in Single-Phase Flows in Microgaps

2020 ◽  
Author(s):  
Debora C. Moreira ◽  
Gherhardt Ribatski ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Single Phase ◽  
Bubble Nucleation ◽  
Low Flow ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Inlet Section ◽  
Flow Rates

Abstract This paper presents a comparison of heat transfer and pressure drop during single-phase flows inside diverging, converging, and uniform microgaps using distilled water as the working fluid. The microgaps were created on a plain heated copper surface with a polysulfone cover that was either uniform or tapered with an angle of 3.4°. The average gap height was 400 microns and the length and width dimensions were 10 mm × 10 mm, resulting in an average hydraulic diameter of approximately 800 microns for all configurations. Experiments were conducted at atmospheric pressure and the inlet temperature was set to 30 °C. Heat transfer and pressure drop data were acquired for flow rates varying from 57 to 485 ml/min and the surface temperature was monitored not to exceed 90 °C to avoid bubble nucleation, so the heat flux varied from 35 to 153 W/cm2 depending on the flow rate. The uniform configuration resulted in the lowest pressure drop, and the diverging one showed slightly higher pressure drop values than the converging configuration, possibly because the flow is most constrained at the inlet section, where the fluid is colder and presents higher viscosity. In addition, a minor dependence of pressure drop with heat flux was observed due to temperature dependent properties. The best heat transfer performance was obtained with the converging configuration, which was especially significant at low flow rates. This behavior could be explained by an increase in the heat transfer coefficient due to flow acceleration in converging gaps, which compensates the decrease in temperature difference between the fluid and the surface due to fluid heating along the gap. Overall, the comparison between the three configurations shows that converging microgaps have better performance than uniform or diverging ones for single-phase flows, and such effect is more pronounced at lower flow rates, when the fluid experiences higher temperature changes.

scholarly journals An In Vitro Evaluation of the Red Cell Damage and Hemocompatibility of Different Central Venous Catheters

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Alojz Ihan ◽  
Stefan Grosek ◽  
David Stubljar
Keyword(s):  
Blood Cell ◽  
Flow Rate ◽  
Blood Cells ◽  
Cell Damage ◽  
Central Venous Catheters ◽  
High Flow ◽  
High Flow Rate ◽  
Low Flow ◽  
Central Venous ◽  
Flow Rates

Background. The aim of our study was to evaluate the damaging impact of characteristics of the central venous catheters (CVCs) on red blood cells. Methods. CVCs from three different manufacturers were analyzed, including the presence of coating, tunnel geometry, length, lumen diameter, and number of lumens with two respective flow rates (33 mL/min and 500 mL/min). Blood cell damage was defined by analyzing microparticle (MP) and hematologic analysis. MPs were isolated by ultracentrifugation of erythrocyte concentrate and analyzed on a flow cytometer. Results. Characteristics of catheters were not associated with blood cell damage at a low flow rate but showed an effect with a high flow rate. CVCs with a polyhexanide methacrylate coating have caused statistically less blood cell damage than noncoated CVCs. The length of lumens, diameter, and geometry of the tunnel showed no differences in blood cell damage. Meanwhile, the number of lumens was predicted to have a greater effect on the erythrocyte damage, which was revealed with the formation of MPs and hematological parameters. CVCs with five lumens caused significantly less damage to the blood cells than CVCs with a single lumen. Moreover, a high flow rate of 500 mL/min caused less damage to the blood cells than a low rate of 33 mL/min. Conclusion. Properties of CVCs are an important factor for quality patient care, especially when transfusing blood with high flow rates, as we want to provide a patient with high-quality blood with as few damaged cells as possible.

Computational and Experimental Studies of UV/Titania Photocatalytic Oxidation of VOCs in Honeycomb Monoliths

1998 ◽  
Vol 3 (3) ◽  
Author(s):  
Robert J. Hall ◽  
Peggy Bendfeldt ◽  
Timothy N. Obee ◽  
Joseph J. Sangiovanni
Keyword(s):  
Pressure Drop ◽  
Photocatalytic Oxidation ◽  
Specular Reflection ◽  
Experimental Studies ◽  
High Flow ◽  
Design Constraint ◽  
Uv Illumination ◽  
Photocatalytic Destruction ◽  
Important Design ◽  
Gaseous Contaminants

AbstractThe use of honeycombs as monolith supports for UV/Titania photocatalysis of volatile organic compounds (VOCs) has been investigated theoretically and experimentally. A theoretical model based on analysis of the UV intensity distribution, transport of gaseous contaminants to the catalyzed surface, and surface photocatalytic destruction has been developed. Both diffuse and specular reflection models have been developed for the UV illumination calculations. The model uses measured intrinsic photocatalytic destruction rates determined in a research reactor which gives the concentration-, humidity-, and UV intensity-dependences of the rates. Model predictions have been compared to measurements in a high-flow, staged monolith, demonstration purifier for several gaseous contaminants of interest. Agreement between modeling and experiment is generally quite good. The sensitivity of purifier efficiency to monolith pore size and illuminated contact time is discussed. The performance obtained with honeycombs is comparable to that with porous foams, but with much reduced weight, pressure drop, and cost. The conclusion of this research is that honeycomb monoliths are attractive for use in practical UV/Titania photocatalytic devices, particularly at very high flow rates where pressure drop is a concern, and for those situations where monolith weight is an important design constraint.

Rheological Effects of Blood in a Nonplanar Distal End-to-Side Anastomosis

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Qian-Qian Wang ◽  
Bao-Hong Ping ◽  
Qing-Bo Xu ◽  
Wen Wang
Keyword(s):  
Flow Rate ◽  
Stokes Equations ◽  
Bypass Graft ◽  
High Flow ◽  
Secondary Flows ◽  
Newtonian Fluids ◽  
Low Flow ◽  
Flow Rates ◽  
Flow Recirculation ◽  
Low Flow Rate

This study investigates rheological effects of blood on steady flows in a nonplanar distal end-to-side anastomosis. The shear-thinning behavior of blood is depicted by a Carreau–Yasuda model and a modified power-law model. To explore effects of nonplanarity in vessel geometry, a curved bypass graft is considered that connects to the host artery with a 90deg out-of-plane curvature. Navier–Stokes equations are solved using a finite volume method. Velocity and wall shear stress (WSS) are compared between Newtonian and non-Newtonian fluids at different flow rates. At low flow rate, difference in axial velocity profiles between Newtonian and non-Newtonian fluids is significant and secondary flows are weaker for non-Newtonian fluids. At high flow rate, non-Newtonian fluids have bigger peak WSS and WSS gradient. The size of the flow recirculation zone near the toe is smaller for non-Newtonian fluids and the difference is significant at low flow rate. The nonplanar bypass graft introduces helical flow in the host vessel. Results from the study reveal that near the bed, heel, and toe of the anastomotic junction where intimal hyperplasia occurs preferentially, WSS gradients are all very big. At high flow rates, WSS gradients are elevated by the non-Newtonian effect of blood but they are reduced at low flow rates. At these locations, blood rheology not only affects the WSS and its gradient but also secondary flow patterns and the size of flow recirculation near the toe. This study reemphasizes that the rheological property of blood is a key factor in studying hemodynamic effects on vascular diseases.

Control of Self-Excited Flow Oscillations in Vaneless Diffuser of Centrifugal Compression Systems

1982 ◽  
Author(s):  
A. N. Abdelhamid
Keyword(s):  
Flow Field ◽  
Performance Improvement ◽  
High Flow ◽  
Low Flow ◽  
Flow Oscillation ◽  
Vaneless Diffuser ◽  
Flow Area ◽  
Flow Measurements ◽  
Flow Rates ◽  
Flow Oscillations

Experiments were conducted to evaluate the effectiveness of axisymmetric diffuser exit throttle in delaying the occurrence of self-excited flow oscillation in vaneless diffusers. Sharp edge rings were installed at diffuser exit in order to change the exit flow area. Tests were carried out with the rings attached to one or both of the diffuser walls. Steady and unsteady flow measurements were used to determine the flow field in the diffuser at the onset of the flow oscillations. Results showed that the occurrence of flow oscillation was continuously delayed as the diffuser exit flow area was reduced for all these configurations and impeller speeds. Comparison between the performance of the compression system with and without diffuser exit blockage indicated that although large losses occur at high flow rates, the use of diffuser exit rings resulted in overall diffuser performance improvement at low flow rates. Retractable diffuser exit rings would therefore be ideal for centrifugal compression systems with vaneless diffuser.

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