Study of Unsteady Orifice Flow Characteristics in Hydraulic Oil Lines

1996 ◽  
Vol 118 (4) ◽  
pp. 743-748 ◽  
Author(s):  
Seiichi Washio ◽  
Satoshi Takahashi ◽  
Yonguang Yu ◽  
Satoshi Yamaguchi
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Pressure Loss ◽  
Flow Characteristics ◽  
High Fidelity ◽  
Flow Rates ◽  
Hydraulic Oil ◽  
Orifice Flow ◽  
Net Pressure ◽  
Clockwise Hysteresis

A technique to measure fluctuating differential pressures with high fidelity has been developed first. When applied to detecting differential pressures generated by an accelerated or decelerated liquid column, the technique turned out to be effective in finding unsteady flow rates. An experimental study has been carried out on periodically changing hydraulic oil flows through an orifice. The results support the validity of the traditional standpoint that characteristics of an unsteady orifice flow can be approximately represented by those of a steady-state one. When inspected in detail, however, a net pressure loss across an orifice in a periodical flow is delayed against a change of the flow rate. The resulting relation between the pressure loss and the flow rate describes a loop with a counter-clockwise hysteresis and a nonlinear twist along the steady-state one. Pressure recovery in a pulsating orifice flow varies with the flow rate almost along the steady-state relation, which is confirmed when the change is not fast.

Effects of short blades on performance and inner flow characteristics of a low-specific-speed centrifugal pump

2017 ◽  
Vol 231 (4) ◽  
pp. 290-302 ◽  
Author(s):  
Can Kang ◽  
Ning Mao ◽  
Chen Pan ◽  
Yang Zhu ◽  
Bing Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Low Flow ◽  
Back Surface ◽  
Flow Rates ◽  
Pump Operation ◽  
Low Specific Speed ◽  
Specific Speed

A low-specific-speed centrifugal pump equipped with long and short blades is studied. Emphasis is placed on the pump performance and inner flow characteristics at low flow rates. Each short blade is intentionally shifted towards the back surface of the neighboring long blade, and the outlet parts of the short blades are uniformly shortened. Unsteady numerical simulation is conducted to disclose inner flow patterns associated with the modified design. Thereby, a comparison is enabled between the two schemes featured by different short blades. Both practical operation data and numerical results support that the deviation and cutting of the short blades can eliminate the positive slope of pump head curve at low flow rates. Therefore, the modification of short blades improves the pump operation stability. Due to the shortening of the outlet parts of the short blades, velocity distributions between impeller outlet and radial diffuser inlet exhibit explicitly altered circumferential flow periodicity. Pressure fluctuations in the radial diffuser are complex in terms of diversified periodicity and amplitudes. Flow rate influences pressure fluctuations in the radial diffuser considerably. As flow rate decreases, the regularity of the orbit of hydraulic loads exerted upon the impeller collapses while hydraulic loads exerted upon the short blades remain circumferentially periodic.

An Experimental Study of the Flow of R-407C in an Adiabatic Spiral Capillary Tube

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
M. K. Mittal ◽  
R. Kumar ◽  
A. Gupta
Keyword(s):  
Experimental Data ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Flow Characteristics ◽  
Flow Rates ◽  
Tube Test ◽  
Mass Flow Rates ◽  
R 134A

The objective of this study is to investigate the effect of coiling on the flow characteristics of R-407C in an adiabatic spiral capillary tube. The characteristic coiling parameter for a spiral capillary tube is the coil pitch; hence, the effect of the coil pitch on the mass flow rate of R-407C was studied on several capillary tube test sections. It was observed that the coiling of the capillary tube significantly reduced the mass flow rate of R-407C in the adiabatic spiral capillary tube. In order to quantify the effect of coiling, the experiments were also conducted for straight a capillary tube, and it was observed that the coiling of the capillary tube reduced the mass flow rate in the spiral tube in the range of 9–18% as compared with that in the straight capillary tube. A generalized nondimensional correlation for the prediction of the mass flow rates of various refrigerants was developed for the straight capillary tube on the basis of the experimental data of R-407C of the present study, and the data of R-134a, R-22, and R-410A measured by other researchers. Additionally, a refrigerant-specific correlation for the spiral capillary was also proposed on the basis of the experimental data of R-407C of the present study.

scholarly journals Numerical Investigation of Mixing Characteristic for CH4/Air in Rotating Detonation Combustor

2020 ◽  
Vol 10 (4) ◽  
pp. 1298
Author(s):  
Shan Jin ◽  
Qingyang Meng ◽  
Zhiming Li ◽  
Ningbo Zhao ◽  
Hongtao Zheng ◽  
...  
Keyword(s):  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Ignition Energy ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Critical Ignition ◽  
Rotating Detonation

The mixing process of fuel and oxidizer is a very critical factor affecting the real operating performance of non-premixed rotating detonation combustor. In this paper, a two-dimensional numerical study is carried out to investigate the flow and mixing characteristics of CH4/air in combustor with different injection structures. On this basis, the effect of CH4/air mixing on the critical ignition energy for forming detonation is theoretically analyzed in detail. The numerical results indicate that injection strategies of CH4 and air can obviously affect the flow filed characteristic, pressure loss, mixing uniformity and local equivalence ratio in combustor, which further affect the critical ignition energy for forming detonation. In the study for three different mass flow rates (the mass flow rates of air are 12.01 kg/s,8.58 kg/s and 1.72 kg/s, respectively), when air is radially injected into combustor (fuel/air are injected perpendicular to each other), although the mixing quality of CH4 and air is improved, the total pressure loss is also increased. In addition, the comparative analysis also shows that the increase of mass flow rate of CH4/air can decrease the difference of the critical ignition energy for forming detonation at a constant total equivalence ratio. The ignition energy decreases with the decrease of the total flow rate and then increases gradually.

Experimental Study of Entrance Effects on Laminar Gas Flow Through Silicon Orifices

2005 ◽  
Author(s):  
Aaron J. Knobloch ◽  
Joell R. Hibshman ◽  
George Wu ◽  
Rich Saia
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Flow Area ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Flow Models ◽  
Entry Length ◽  
Orifice Flow ◽  
Measured Flow ◽  
Flow Through

This study summarizes a fundamental investigation of flow through an array of silicon micromachined rectangular slots. The purpose of the study is to evaluate the effect of entrance pressure, flow area, orifice thickness, slot length, and slot width of the orifice on flow rate. These orifices were fabricated using a simple frontside through wafer DRIE process on a 385 μm thick wafer and wafer bonding to create thicker orifices. The dies were then packaged as part of a TO8 can and flow tested. To complement the results of this experimental work, two simple flow models were developed to predict the effect of geometrical and entrance conditions on the flow rate. These models were based on macroscale assumptions that were not necessarily true in the case of thin orifices. One relationship was based on Pouiselle flow which assumes fully developed flow conditions. Calculation of the entry length required for fully developed flow indicate that in the low Reynolds Number regime (32-550) evaluated, the entry flow development requires 2-8 times the thickness of the thickest orifices used for this study. Therefore, calculations of orifice flow based on a Pouiselle model are an overestimate of the actual measured flow rates. Another model examined typical orifice relationships using head loss at the entrance and exit of the slots did not accurately capture the particular flow rates since it overestimated the expansion or constriction losses. A series of experiments where the pressure was varied between 75 and 1000 Pa were performed. A comparison of the Pouiselle flow solution with experimental results was made which showed that the Pouiselle flow model overpredicts the flow rates and more specifically, the effect of width on the flow rates. The results of these tests were used to develop a transfer function which describes the dependence of flow rate on orifice width, thickness, length, and inlet pressure.

Four-port hydraulic transformer with inlet and outlet equal flow and its flow characteristics

2021 ◽  
pp. 095440622110316
Author(s):  
Chu Zhang ◽  
Lianquan Zhou ◽  
Xiaonan Bo ◽  
Weiwei Qu ◽  
Panpan Zang
Keyword(s):  
Theoretical Analysis ◽  
Flow Rate ◽  
Hydraulic System ◽  
Measurement Data ◽  
Flow Characteristics ◽  
Remarkable Feature ◽  
Flow Rates ◽  
Instantaneous Flow ◽  
Hydraulic Transformer ◽  
System A

Without changing the original valve control hydraulic system, a kind of hydraulic transformer, called four-port hydraulic transformer (FHT), is proposed to recover the energy loss caused by system throttling. The remarkable feature of FHT is that the flow rate at inlet and outlet ports are equal. This means that FHT can be connected into the load circuit of hydraulic system to recovery energy without refreshing flow rate. This paper investigates the flow characteristics of FHT, including instantaneous flow rates, average flow rates and flow pulsations in each port. The relationships between the structure of port plate and the flow characteristics are given. The variation rule of number of plungers connected to four ports is shown, and the relationship between the variation and the flow pulsation is revealed. The simulation results show that the flow rates and displacements of symmetrical ports are same, and the instantaneous flow rate of symmetrical ports has the same rule. The results also show the frequent changes of the number of plungers connected with each port lead to more flow jump points in instantaneous curves, and the jump point is the basic cause of its loud noise. The test shows that the flow rates of measurement data of the experiment are very close to the theoretical analysis, proved the theoretical analysis of flow characteristics for FHT are appropriate and reasonable, which has a certain reference for the development and energy-saving application for FHT.

Work With Chemical Additives Advances Understanding of Relative Permeability Shifts

2021 ◽  
Vol 73 (09) ◽  
pp. 37-38
Author(s):  
Chris Carpenter
Keyword(s):  
Steady State ◽  
Relative Permeability ◽  
Flow Rate ◽  
Pressure Difference ◽  
Effective Permeability ◽  
Constant Flow ◽  
Chemical Additives ◽  
Flow Rates ◽  
Steady State Method ◽  
Tight Rocks

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 201520, “Advances in Understanding Relative Permeability Shifts by Imbibition of Surfactant Solutions Into Tight Plugs,” by Mohammad Yousefi, Lin Yuan, and Hassan Dehghanpour, SPE, University of Alberta, prepared for the 2020 SPE Annual Technical Conference and Exhibition, originally scheduled to be held in Denver, Colorado, 5–7 October. The paper has not been peer reviewed. Various chemical additives have been proposed recently to enhance imbibition oil recovery from tight formations during shut-in periods after hydraulic fracturing operations. In the complete paper, the authors develop and apply a laboratory protocol mimicking leakoff, shut-in, and flowback processes to evaluate the effects of fracturing-fluid additives on oil regained permeability. A conventional coreflooding apparatus is modified to measure oil effective permeability (koeff) before and after the surfactant-imbibition experiments. Methodology Proposed Technique for Measuring Oil Effective Permeability. Despite the simplicity of the steady-state method, measuring permeability of tight rocks with this technique is challenging because of its time-consuming nature and the fact that accurate measurement is necessary of extremely low flow rates corresponding to low injectivity of tight rocks. The authors use a pair of plugs from a well drilled in the Montney formation that is a stratigraphic unit of the Lower Triassic age in the western Canadian sedimentary basin located in British Columbia and Alberta. It is mainly a low-permeability siltstone reservoir. In the modified coreflooding apparatus, the authors reduce the effect of compressibility in order to reduce the duration of the transient period by approximately one order of magnitude. Because monitoring changes in pressure is much easier and more accurate than monitoring flow-rate changes, a constant flow-rate mode is used and pressure is recorded with time. Oil is injected at different constant flow rates (qo), and the inlet pressure is monitored. The stable pressure difference across the plug is recorded for each flow rate. After steady-state conditions are reached based on the pressure profile, the qo is increased. This process is repeated until four stable pressure differences corresponding to four different qo are obtained. After the highest qo is reached, it is decreased in similar steps to check the repeatability of each data point. The permeability is calculated with the Darcy equation and slope of the qo vs. stable pressure difference across the plug.

Catheter position and blood gases during constant-flow ventilation

1987 ◽  
Vol 62 (2) ◽  
pp. 513-519 ◽  
Author(s):  
A. S. Slutsky ◽  
A. S. Menon
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Blood Gases ◽  
Constant Flow ◽  
Arterial Blood Gases ◽  
Catheter Position ◽  
Flow Rates ◽  
Arterial Blood ◽  
Tracheal Carina ◽  
Co2 Elimination

We studied the effect of catheter position and flow rate on gas exchange during constant-flow ventilation (CFV) in eight anesthetized, paralyzed dogs. The distal tips of the insufflation catheters were positioned 0.5, 2.0, 3.5, and 5.0 cm from the tracheal carina. Flow rates were varied between 10 and 55 l/min and steady-state arterial blood gases were measured. At a given flow rate, arterial CO2 pressure (PaCO2) decreased as CFV was administered further into the lung up to a distance of 3.5 cm from the carina; there were no significant differences in PaCO2 at 3.5 and 5.0 cm. For a given catheter position, PaCO2 decreased with increasing flow rate up to a flow rate of 40 l/min. Further increases in flow rate had no significant effect on PaCO2. Arterial O2 pressure (PaO2) was relatively constant at all flow rates and catheter positions. We conclude that, up to a point, CO2 elimination can be improved by positioning the catheters further into the lung; advancing the catheters further than 3.5 cm from the carina may cause over-ventilation of specific lung regions resulting in a relative plateau in CO2 elimination and relatively constant PaO2's. Positioning the catheters further into the lung permits the use of lower flow rates, thus potentially minimizing the risk of barotrauma.

scholarly journals An Experimental Study of the Flow Field Inside the Diffuser Passage of a Laboratory Centrifugal Pump

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Qiaorui Si ◽  
Patrick Dupont ◽  
Annie-Claude Bayeul-Lainé ◽  
Antoine Dazin ◽  
Olivier Roussette ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Design Flow ◽  
Low Flow ◽  
Mean Flow ◽  
Local Pressure ◽  
Flow Rates ◽  
Piv Measurement ◽  
Measurement Results

Measurements are processed on a centrifugal pump model, which works with air and performs with the vane-island type diffuser of a real hydraulic pump, under five flow rates to investigate the internal flow characteristics and their influence on overall pump performance. The mean flow characteristics inside the diffuser are determined by using a miniature three-hole probe connected to an online data acquisition system. The flow structure at the inlet section of the diffuser is analyzed in detail, with a focus on the local pressure loss inside the vaneless gap and incidence angle distributions along the hub-to-shroud direction of the diffuser. Some existing calculations, including leakage effects, are used to evaluate the pressure recovery downstream of the impeller. Furthermore, particle image velocimetry (PIV) measurement results are obtained to help analyze the flow characteristics inside the vane-island diffuser. Each PIV measuring plane is related to one particular diffuser blade-to-blade channel and is analyzed by using the time-averaged method according to seven different relative positions of the impeller. Measurement results show that main loss is produced inside the vaneless part of the diffuser at low flow rates, which might have been caused by the strong rotor–stator interaction. When the impeller flow rate is greater than the diffuser design flow rate, a large fluctuating separated region occurs after the throat of the diffuser on the pressure side. Mean loss originates from the unsteady pressure downstream of the diffuser throat. For better characterization of the separations observed in previous experimental studies, complementary unsteady static pressure measurement campaigns have been conducted on the diffuser blade wall. The unsteadiness revealed by these measurements, as well as theirs effects on the diffuser performance, was then studied.

Enhanced Impingement Heat Transfer: The Influence of Impingement X/D for Interrupted Rib Obstacles (Rectangular Pin Fins)

2004 ◽  
Author(s):  
G. E. Andrews ◽  
R. A. A. Abdul Hussain ◽  
M. C. Mkpadi
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Pressure Loss ◽  
Smooth Wall ◽  
Flow Rates ◽  
Impingement Heat Transfer ◽  
Main Effect ◽  
Pin Fins ◽  
Hole Arrays ◽  
Square Hole

Impingement flat wall cooling, with 15.2 mm pitch square hole arrays, was investigated in the presence of an array of interrupted rib obstacles. These ribs took the form of rectangular pin-fins with a 50% blockage to the crossflow. One side exit of the air was used and there was no initial crossflow. Three hole diameters were investigated, which allowed the impingement wall pressure loss to be varied at constant coolant mass flow rate. Combustor wall cooling was the main application of the work, where a low wall cooling pressure loss is required if the air is subsequently to be fed to a low NOx combustor. The results showed that the increase in surface average impingement heat transfer, relative to that for a smooth wall, was small and greatest for an X/D of 3.06 at 15%. The main effect of the interrupted ribs was to change the influence of crossflow, which produced a deterioration in the heat transfer with distance compared with a smooth impingement wall. With the interrupted ribs the heat transfer increased with distance. If the heat transfer was compared at the trailing edge of the test section, where the upstream crossflow was at a maximum, then at high coolant flow rates the increase in heat transfer was 21%, 47% and 25% for X/D of 4.66, 3.06 and 1.86 respectively.

Steady-State Tilting-Pad Bearing Performance Under Reduced Oil Supply Flow Rates

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Bradley R. Nichols ◽  
Roger L. Fittro ◽  
Christopher P. Goyne
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Flow Rate ◽  
Flow Model ◽  
Leading Edge ◽  
Input Power ◽  
Flow Rates ◽  
Flow Models ◽  
Oil Supply ◽  
Tilting Pad

Reduced oil supply flow rates in fluid film bearings can cause cavitation, or lack of a fully developed hydrodynamic film layer, at the leading edge of the bearing pads. Reduced oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses and is commonly referred to as starvation. This study looks at the effects of oil supply flow rate on steady-state bearing performance and provides increased experimental data for comparison to computational predictions. Tests are conducted on a five-pad tilting-pad bearing positioned in a vintage, flooded housing with oil supply nozzles. Pad temperatures, sump temperature, journal operating position, and motor input power are measured at various operating speeds ranging from 2000 to 12,000 rpm and various oil supply flow rates. Predicted results are obtained from bearing modeling software based on thermoelastohydrodynamic (TEHD) lubrication theory. A starved flow model was previously developed as an improvement over the original flooded flow model to more accurately capture bearing behavior under reduced flow conditions. Experimental results are compared to both flow models. The starved bearing model predicts significantly higher journal operating positions than the flooded model and shows good correlation with the experimental data. Predicted pressure profiles from the starved bearing model show cavitation of the upper unloaded pads that increase in severity with increasing speed and decreasing oil supply flow rate. The progressive unloading of these top pads explains the rise in shaft centerline position and helps further validate the starvation model.

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