scholarly journals Design of a new-concept conical positive displacement slurry pump for continuous de-clogging

2019 ◽  
Vol 287 ◽  
pp. 01017
Author(s):  
G. Vasileiou ◽  
N. Rogkas ◽  
S. Tsolakis ◽  
V. Spitas ◽  
P. Zalimidis
Keyword(s):  
Mass Flow ◽  
Aggregate Size ◽  
Axial Direction ◽  
Mixture Flow ◽  
Screw Pump ◽  
Velocity Increase ◽  
Positive Displacement ◽  
Continuous Mixture ◽  
Novel Concept ◽  
Concrete Pump

Slurry pumps are extensively used in the construction industry while positive displacement screw pumps are used in most mobile concrete pump applications. The aggregate size is known to significantly affect pump performance in terms of clogging. Large aggregates tend to be trapped against the stator-rotor interface, blocking the continuous and smooth operation of the screw pump. In order to avoid the development of excessive stress values able to damage the rotor-stator mechanism of the pump, the typical de-clogging mechanism deployed by most positive displacement screw slurry pumps includes reversing the rotation of the pump driving motor thus allowing the aggregates to be carried away with the mixture, so that the pump can soon resume its operation. This procedure causes frequent start-stops of the pump resulting in dis-continuation of the pumped mixture lasting a few seconds, that while being of little importance in most construction applications, can be of significance in applications requiring higher levels of accuracy and continuous mixture flow. In the context of this work, a novel concept of positive displacement screw slurry pump is presented, including a continuous de-clogging mechanism, without the need to reverse the rotation of the driving motor. This de-clogging operation is achieved through the modification of the geometry of both the rotor and stator introducing a conical form along the axial direction. This configuration of the rotor-stator, allows for small displacements along the axial direction, which in turn increases the size of the cavities facilitating the de-clogging of the pump. Variable pitch is also introduced to both the rotor and stator in order to ensure constant mass flow of the mixture throughout the length of the screw pump covering for the velocity increase as a result of the conical geometry. The axial movement of the rotor in relation to the fixed stator, is achieved through the elastic support of the rotor in the axial direction, that allows for small axial displacements, when stresses induced from trapped aggregates exceed the stiffness of the support. The proposed concept comprises a passive real-time de-clogging mechanism that greatly reduces pump idle time compared to the conventional mechanism described earlier, providing smoother operation and stable mass flow of the mixture.

Design and Development of a Specially Modified Positive Displacement Rotary Screw Pump and Relevant Hydraulic Circuit to Enhance “Entrained Air Handling” Capability in a Closed Loop Lube Oil System

2013 ◽  
Author(s):  
Simone Berti ◽  
Pietro Fracassi ◽  
Alessandra Mattioli ◽  
Varuna Reddy Potula ◽  
Cristiano Lotti
Keyword(s):  
Numerical Data ◽  
Oil And Gas Industry ◽  
Critical Parameters ◽  
Circulation System ◽  
Design And Development ◽  
Screw Pump ◽  
Positive Displacement ◽  
Corrective Actions ◽  
Entrained Air ◽  
Rotary Screw

Rotary screw type positive displacement (RSPD) pumps are commonly used in Oil and Gas Industry for pumping of mineral lube oil in services where they can be mechanically driven by gears coupled to a train driver. Installation of these pumps is critical and should be designed jointly by vendors and users according to project specific restrictions (i.e. the arrangement of the entire oil circulation system). This paper describes a real case in which restrictions due to lube oil system arrangement have produced low pump suction head and have amplified the influence of air bubbles that remained entrained in oil despite lube oil tank degassing. The investigations have been directed toward the mathematical modeling of the aeration phenomenon coupled with experimental measurements of critical parameters taken on the shop plant. Among corrective actions identified and considered there are reduction of quantity of air entering the lube oil system and revamping of the entire lube oil system with changes in piping, tank and also in pump model together with special modifications of internal path to enhance air handling capabilities. In order to validate pump behavior with reference to resistance to aeration (monitoring noise and vibration) a special simulation set-up was jointly developed by end user and manufacturer on a pilot test bench to carry out the various performance tests. The numerical data collected during shop aeration test have confirmed that the pump was able to handle the expected amount of entrained air with noise and vibrations within industrial limits. The pumps tested in the pilot bench were installed at user’s site and the effectiveness of the synergic corrective actions listed above was successfully verified. The study concludes that an early estimation of entrained air in the lube oil system is critical for design and development of either the RSPD pump or the entire lube oil circuit of a motor compressor train. When a critical quantity of entrained air is likely to be reached at pump suction (near 10% in volume), pump manufacturers and end users should apply some basic rules related to “design for aeration” of the pump and agree on a non-routine test to be performed at manufacturer’s shop before pump installation at site. This will serve as a reliable prediction of pump air handling capabilities, without which effective operation, reliability and durability of the pump could be jeopardized.

Analysis of flowrates as a basis for the simulation of dry-running rotational positive displacement pumps

2002 ◽  
Vol 216 (12) ◽  
pp. 1197-1205 ◽  
Author(s):  
K Kauder ◽  
D Wenderott
Keyword(s):  
Mass Flow ◽  
Characteristic Number ◽  
Operational Reliability ◽  
Simulation System ◽  
Positive Displacement ◽  
Market Situation ◽  
Flow Through ◽  
The One ◽  
New Applications ◽  
Operational Behaviour

New applications improve the market situation of dry-running positive displacement pumps. The mostly empirically based design of these pumps has to take into account partly competing viewpoints. These viewpoints are energetic process optimization, on the one hand, and operational reliability, on the other hand. A simulation system can be used to solve this problem. The simulation system uses an energy and a mass balance in order to simulate the operational behaviour of the vacuum pumps. Therefore knowledge of the different states of flow through clearances in a vacuum is essential. The experimental examination of the flow is done by flood curve measurements, to describe the mass flow integrally using the characteristic number of the standardized mass flow. The results for some possible plain clearance shapes are discussed.

Design and Development of a Specially Modified Positive Displacement Rotary Screw Pump and Relevant Hydraulic Circuit to Enhance “Entrained Air Handling” Capability in a Closed Loop Lube Oil System

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Simone Berti ◽  
Pietro Fracassi ◽  
Alessandra Mattioli ◽  
Varuna Reddy Potula ◽  
Cristiano Lotti
Keyword(s):  
Numerical Data ◽  
Oil And Gas Industry ◽  
Critical Parameters ◽  
Circulation System ◽  
Design And Development ◽  
Screw Pump ◽  
Positive Displacement ◽  
Corrective Actions ◽  
Entrained Air ◽  
Rotary Screw

Rotary screw type positive displacement (RSPD) pumps are commonly used in oil and gas industry for pumping of mineral lube oil in services where they can be mechanically driven by gears coupled to a train driver. Installation of these pumps is critical and should be designed jointly by vendors and users according to project specific restrictions (i.e., the arrangement of the entire oil circulation system). This paper describes a real case in which restrictions due to lube oil system arrangement have produced low pump suction head and have amplified the influence of air bubbles that remained entrained in oil despite lube oil tank degassing. The investigations have been directed toward the mathematical modeling of the aeration phenomenon coupled with experimental measurements of critical parameters taken on the shop plant. Among corrective actions identified and considered there are reduction of quantity of air entering the lube oil system and revamping of the entire lube oil system with changes in piping, tank and also in pump model together with special modifications of internal path to enhance air handling capabilities. In order to validate pump behavior with reference to resistance to aeration (monitoring noise and vibration) a special simulation setup was jointly developed by end user and manufacturer on a pilot test bench to carry out the various performance tests. The numerical data collected during shop aeration test have confirmed that the pump was able to handle the expected amount of entrained air with noise and vibrations within industrial limits. The pumps tested in the pilot bench were installed at user's site and the effectiveness of the synergic corrective actions listed above was successfully verified. The study concludes that an early estimation of entrained air in the lube oil system is critical for design and development of either the RSPD pump or the entire lube oil circuit of a motor compressor train. When a critical quantity of entrained air is likely to be reached at pump suction (near 10% in volume), pump manufacturers and end users should apply some basic rules related to “design for aeration” of the pump and agree on a nonroutine test to be performed at manufacturer's shop before pump installation at site. This will serve as a reliable prediction of pump air handling capabilities, without which effective operation, reliability and durability of the pump could be jeopardized.

Mathematical modeling of processes in the human respiratory system

2015 ◽  
Vol 9 (2) ◽  
pp. 0-0 ◽  
Author(s):  
Канунникова ◽  
A. Kanunnikova ◽  
Ивахно ◽  
N. Ivakhno ◽  
Федоров ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Mass Flow ◽  
Respiratory System ◽  
Breathing Circuit ◽  
Stress Component ◽  
Respiratory Muscles ◽  
Axial Direction ◽  
Flow Diagram ◽  
Cylinder Wall ◽  
Human Respiratory System

Scientific relevance and purpose. This research looks at the urgent task of modeling the structure of the human respiratory system and processes occurring in it, in order to predict the changes in physiological parameters occurring under different mechanical actions. Results. This paper suggests mathematical model based on the description of equations of the mass flow and mass flow rate in the pulmonary channels in cases, when airways are branched in accordance with the prin-ciple of regular dichotomy with regard to the equations of work dynamics of the respiratory muscles and the ability to model different stresses in the breathing circuit, caused by trainers. The research examined the stresses generated by muscles in the radial and axial direction of the equivalent hollow cylinder, which represented the chest with regard to the elastic stress component in the cylinder wall and variable muscle stress in the circumfe-rential direction. The paper contains the results of mathematical modeling of breathing without stress, the graphs of volume and mass flow in lungs generations and pressure-flow diagram. Conclusions. The developed mathematical models enable more precise multi-parameter modeling of the dynamics of functioning of complex biotech system "respiratory muscles trainer - human", which enables the implementation of the prediction of shifts of physiological and mechanical properties from the values of the normal process and to adjust the control actions on this basis

Combination of CFD and DOE to Analyze and Improve the Mass Flow Rate in Urinary Catheters

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Patrick Frawley ◽  
Marco Geron
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Urinary Catheter ◽  
Patient Comfort ◽  
Efficient Manner ◽  
Plastic Tube ◽  
Catheter Design ◽  
Input Variables ◽  
Novel Concept

The urinary catheter is a thin plastic tube that has been designed to empty the bladder artificially, effortlessly, and with minimum discomfort. The current CH14 male catheter design was examined with a view to optimizing the mass flow rate. The literature imposed constraints to the analysis of the urinary catheter to ensure that a compromise between optimal flow, patient comfort, and everyday practicality from manufacture to use was achieved in the new design. As a result a total of six design characteristics were examined. The input variables in question were the length and width of eyelets 1 and 2 (four variables), the distance between the eyelets, and the angle of rotation between the eyelets. Due to the high number of possible input combinations a structured approach to the analysis of data was necessary. A combination of computational fluid dynamics (CFD) and design of experiments (DOE) has been used to evaluate the “optimal configuration.” The use of CFD couple with DOE is a novel concept, which harnesses the computational power of CFD in the most efficient manner for prediction of the mass flow rate in the catheter.

scholarly journals Experimental and Numerical 3-D Investigations of the Flow Field Behind the Trailing Edge of a Cooled Turbine Guide Vane

1996 ◽  
Author(s):  
Dieter E. Bohn ◽  
Volker J. Becker ◽  
Klaus D. Behnke
Keyword(s):  
Mass Flow ◽  
Gas Flow ◽  
Guide Vane ◽  
Density Ratio ◽  
Axial Direction ◽  
Cold Test ◽  
Experimental Investigations ◽  
Trailing Edge ◽  
Hot Gas ◽  
Calculated Velocity

Experimental investigations have been carried out to analyze the hot gas flow and cooling gas flow in the direct vicinity of the trailing edge of a modern gas turbine vane, with cooling gas ejection through the trailing edge. The investigations were performed in one of the institute’s test turbines. The experimental set-up is designed to establish variable blowing ratios between cooling gas mass flow and hot gas mass flow. An alternative density ratio between hot gas and cooling gas was established by the use of CO2 instead of air as the cooling gas for cold test runs. The experimental investigations have been carried out for different radial positions. The measurement plane was located 0.2mm to 0.5mm downstream of the trailing edge (trailing edge width 1.6mm). Local regions of high anisotropic turbulence were detected in the mixing zone. For low blowing ratios, the trailing edge pressure side in the tip vicinity was found to be subjected to direct hot gas contact. The trailing edge ejection has an influence of at least one chordlength in axial direction. The experimental investigations were accompanied by 3-D Navier-Stokes computational simulations. The calculated velocity distributions were found to be quite consistent with the experimental results. The calculated flow angles differed locally from the measurements. This may be due to the turbulence model employed.

Investigation of Tip-Flow Based Stall Criteria Using Rotor Casing Visualization

2008 ◽  
Author(s):  
Matthew A. Bennington ◽  
Joshua D. Cameron ◽  
Scott C. Morris ◽  
Camille Legault ◽  
Sean T. Barrows ◽  
...  
Keyword(s):  
Mass Flow ◽  
Flow Direction ◽  
Leading Edge ◽  
Axial Direction ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Momentum Balance ◽  
Reverse Direction ◽  
Axial Component ◽  
Stall Inception

Recent stall inception investigations have indicated that short-length scale stall initiates when the interface between the tip gap flow and the approach flow spills forward of the leading edge of the adjacent blade. This hypothesis was investigated in the present work using both numerical and experimental results from a range of compressor geometries and speed. First, full annulus unsteady computations of R35 were used to generate contours of entropy at the casing. It was found that a large gradient in entropy, which marked the leakage fluid, was aligned with the leading edge plane at the stalling mass flow. It was also observed that the flow direction in the region of increased entropy was in the reverse axial direction. The interface between the approach fluid and the reverse-direction leakage flow was related to a region in which the axial component of the wall shear stress was zero. The axial location of this line was measured experimentally using a surface streaking method using two separate facilities. It was found that the location of this line is determined by a momentum balance between the approach fluid and the tip leakage fluid. Measurements were acquired with varied tip clearance, radial distortion, and centerline offset to support these conclusions. In all cases the zero axial shear line was found to move upstream with decreased flow coefficient, and was in close proximity to the rotor leading edge at the stalling mass flow.

Developing an Optimal Helix Angle As a Function of Pressure for Helical Groove Seals

2017 ◽  
Author(s):  
Cori Watson ◽  
Houston G. Wood
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Helix Angle ◽  
Pressure Differential ◽  
Lower Pressure ◽  
Inlet Pressure ◽  
Circumferential Velocity ◽  
Labyrinth Seals ◽  
Screw Pump ◽  
Helical Groove

Helical groove seals are non-contacting annular seals used in pumps between impeller stages and at the balance drum. These seals have helically machined grooves on the surface of the rotor and/or stator. They work to sustain a pressure difference given a mass flow rate of the impeller through two flow phenomena which can be characterized by their flow direction. Fluid flowing axially dissipates kinetic energy through turbulent mixing as fluid is pushed through the jet stream region and mixes in the larger groove region, thus producing a pressure differential. Fluid flowing in the groove direction rotates with the rotor wall and is positively displaced toward the high pressure region, essentially acting as a screw pump. Previous work with optimization of helical groove seals has shown that the ideal helix angle of the seal is steeper for lower pressure applications and shallower for higher pressure applications. This is due to lower pressure applications having higher circumferential velocity in the grooves. In high pressure applications, the groove circumferential velocity has even been shown to be negative, and therefore the fluid leaks out the end of the grooves. The objective of this study is to use computational fluid dynamics simulations to find the optimal helix angle of the seal given the pressure differential. To accomplish this goal, simulations were run in ANSYS CFX for various inlet pressures, given zero gauge outlet pressure, and the helix angle of the grooves are varied. The helical grooves seals in this study have grooves on only the stator surface. The number of grooves is varied with the angle to keep the axial cross section of the seal consistent. By doing this, the study is able to focus in on the pumping mechanism of the helical groove seal without substantially changing the energy dissipation. The mass flow rates from each simulation for a given inlet pressure are plotted and quadratic regression was used to calculate an optimal helix angle as a function of inlet pressure. This study also answers the question of whether is there a limit where circumferentially grooved, i.e. labyrinth, seals outperform helical groove seals for very high pressures. Results comparing the powerloss of helical groove seals versus labyrinth seals and the effect of helix angle on powerloss are also given.

Transient Flow of the Oil-Refrigerant Mixture Through the Radial Clearance in Rolling Piston Compressors

1999 ◽  
Author(s):  
José L. Gasche ◽  
Rogério T. S. Ferreira ◽  
Álvaro T. Prata
Keyword(s):  
Mass Flow ◽  
Transient Flow ◽  
Tangential Velocity ◽  
Radial Clearance ◽  
Compression Process ◽  
Mixture Flow ◽  
Important Conclusion ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Rolling Piston

Abstract Unsteady flow of oil and refrigerant gas through radial clearance in rolling piston compressors has been modeled as a heterogeneous mixture, where the properties are determined from the species conservation transport equation coupled with momentum and energy equations. Time variations of pressure, tangential velocity of the rolling piston and radial clearance due to pump setting have been included in the mixture flow model. Those variables have been obtained by modeling the compression process, rolling piston dynamics and by using geometric characteristics of the pump, respectively. An important conclusion concerning this work is the large variation of refrigerant concentration in the oil-filled radial clearance during the compression cycle. That is particularly true for large values of mass flow rates, and for those cases the flow mixture cannot be considered as having uniform concentration. In presence of low mass flow rates homogeneous flow prevail and the mixture tend to have a uniform concentration. In general, it was observed that for calculating the refrigerant mass flow rate using the difference in refrigerant concentration between compression and suction chambers, a time average value for the gas concentration should be used at the clearance inlet.

Analysis on slot-type casing treatment injection flow in an axial transonic compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 792-804 ◽  
Author(s):  
Mingmin Zhu ◽  
Xiaoqing Qiang ◽  
Wensheng Yu ◽  
Jinfang Teng
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Direction ◽  
Stall Margin ◽  
Rotating Speed ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Injection Flow ◽  
Flow Through

The purpose of this work is to understand the properties of the injection flow through slots opening surfaces with steady and unsteady simulations. The feasibility of evaluating slot effectiveness by steady results is demonstrated. Transient features of injection flow are detailed investigated. Numerical investigations are carried out in a 1.5 axial transonic compressor stage at a specified rotating speed with seven kinds of slot-type casing treatments. Comparisons between steady/unsteady results show that differences of overall performance and injection mass flow rate are dependent on simulation methods, rather than slot configurations. Thus, correlation analysis by steady results of seven slot configurations is considered valid and reveals strong linear correlation between injection mass flow and stall margin improvements/efficiency drops. Therefore, it is practical to evaluate the effectiveness of a specific slot configuration in this compressor with steady results by calculating injection mass flow rate. Afterwards, unsteady simulations are performed with a specific configuration of arc-curve skewed slots. It is clarified that the dividing locations between suction/injection regions moves along the axial direction based on the relative rotor/slots location. Exchanging flow through slots opening surfaces displays periodic variations over time. The variation cycle for one single slot equals blade passing period T. For summation of mass flow through all slots, the cycle equals to T divided by slots number in one passage. The net flow rate through all opening surfaces is always less than zero during a blading passing period, i.e. injection mass flow rate is larger than suction flow all the time.

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