Showing papers on "Axial compressor published in 2001"

An Experimental and Numerical Investigation Into the Mechanisms of Rotating Instability

Abstract: This paper reports on an experimental and numerical investigation aimed at understanding the mechanisms of rotating instabilities in a low speed axial flow compressor. The phenomena of rotating instabilities in the current compressor were first identified with an experimental study. Then, an unsteady numerical method was applied to confirm the phenomena and to interrogate the physical mechanisms behind them. The experimental study was conducted with high-resolution pressure measurements at different clearances, employing a double phase-averaging technique. The numerical investigation was performed with an unsteady 3-D Navier-Stokes method that solves for the entire blade row. The current study reveals that a vortex structure forms near the leading edge plane. This vortex is the result of interactions among the classical tip-clearance flow, axially reversed endwall flow, and the incoming flow. The vortex travels from the suction side to the pressure side of the passage at roughly half of the rotor speed. The formation and movement of this vortex seem to be the main causes of unsteadiness when rotating instability develops. Due to the nature of this vortex, the classical tip-clearance flow does not spill over into the following blade passage. This behavior of the tip-clearance flow is why the compressor operates in a stable mode even with the rotating instability, unlike traditional rotating stall phenomena.Copyright © 2001 by ASME

Convective Heat Transfer and Aerodynamics in Axial Flow Turbines

Abstract: The primary focus of this paper is convective heat transfer in axial flow turbines. Research activity involving heat transfer generally separates into two related areas: predictions and measurements. The problems associated with predicting heat transfer are coupled with turbine aerodynamics because proper prediction of vane and blade surface-pressure distribution is essential for predicting the corresponding heat transfer distribution. The experimental community has advanced to the point where time-averaged and time-resolved three-dimensional heat transfer data for the vanes and blades are obtained routinely by those operating full-stage rotating turbines. However, there are relatively few CFD codes capable of generating three-dimensional predictions of the heat transfer distribution, and where these codes have been applied the results suggest that additional work is required. This paper outlines the progression of work done by the heat transfer community over the last several decades as both the measurements and the predictions have improved to current levels. To frame the problem properly, the paper reviews the influence of turbine aerodynamics on heat transfer predictions. This includes a discussion of time-resolved surface-pressure measurements with predictions and the data involved in forcing function measurements. The ability of existing two-dimensional and three-dimensional Navier-Stokes codes to predict the proper trends of the time-averaged and unsteady pressure field for full-stage rotating turbines is demonstrated. Most of the codes do a reasonably good job of predicting the surface-pressure data at vane and blade midspan, but not as well near the hub or the tip region for the blade. In addition, the ability of the codes to predict surface-pressure distribution is significantly better than the corresponding heat transfer distributions. Heat transfer codes are validated against measurements of one type or another. Sometimes the measurements are performed using full rotating rigs, and other times a much simpler geometry is used. In either case, it is important to review the measurement techniques currently used. Heat transfer predictions for engine turbines are very difficult because the boundary conditions are not well known. The conditions at the exit of the combustor are generally not well known and a section of this paper discusses that problem. The majority of the discussion is devoted to external heat transfer with and without cooling, turbulence effects, and internal cooling. As the design community increases the thrust-to-weight ratio and the turbine inlet temperature, there remain many turbine-related heat transfer issues. Included are film cooling modeling, definition of combustor exit conditions, understanding of blade tip distress, definition of hot streak migration, component fatigue, loss mechanisms in the low turbine, and many others. Several suggestions are given herein for research and development areas for which there is potentially high payoff to the industry with relatively small risk.

Model Development and Simulation of Transient Behavior of Heavy Duty Gas Turbines

Abstract: This paper describes models for the transient analysis of heavy duty gas turbines, and presents dynamic simulation results of a modern gas turbine for electric power generation. Basic governing equations have been derived from integral forms of unsteady conservation equations. Mathematical models of each component are described with the aid of unsteady one-dimensional governing equations and steady-state component characteristics. Special efforts have been made to predict compressor characteristics including the effect of movable vanes, which govern the operating behavior of a whole engine. The derived equation sets are solved numerically by a fully implicit method. A controller model that maintains constant rotational speed and target temperature (turbine inlet or exhaust temperature) is used to simulate practical operations. Component models, especially those of the compressor, are validated through comparison with test data, The dynamic behavior of a 150 MW class engine is simulated. The time-dependent variations of engine parameters such as power, rotational speed, fuel, temperature, and guide vane angles are compared with field data. Simulated results are fairly close to the operation data.

Mainstream Aerodynamic Effects Due to Wheelspace Coolant Injection in a High-Pressure Turbine Stage: Part I—Aerodynamic Measurements in the Stationary Frame

Abstract: The current paper deals with the aerodynamic measurements in the rotational frame of reference of the Axial Flow Turbine Research Facility (AFTRF) at the Pennsylvania State University. Stationary frame measurements of ‘‘Mainstream Aerodynamic Effects Due to Wheelspace Coolant Injection in a High Pressure Turbine Stage’’ were presented in Part I of this paper. The relative aerodynamic effects associated with rotor ‐nozzle guide vane (NGV) gap coolant injections were investigated in the rotating frame. Three-dimensional velocity vectors including exit flow angles were measured at the rotor exit. This study quantifies the secondary effects of the coolant injection on the aerodynamic and performance character of the stage main stream flow for root injection, radial cooling, and impingement cooling. Current measurements show that even a small quantity (1 percent) of cooling air can have significant effects on the performance and exit conditions of the high-pressure turbine stage. Parameters such as the total pressure coefficient, wake width, and three-dimensional velocity field show significant local changes. It is clear that the cooling air disturbs the inlet end-wall boundary layer to the rotor and modifies secondary flow development thereby resulting in large changes in turbine exit conditions. Effects are the strongest from the hub to midspan. Negligible effect of the cooling flow can be seen in the tip region. @DOI: 10.1115/1.1397303#

An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV

Abstract: Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to successfully control these events. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to simultaneously capture transient velocity and pressure measurements in the non-stationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique which is ideally suited for studying transient flow phenomena in high speed turbomachinery and has been used previously to successfully map the stable operating point flow field in the diffuser of a high speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.

Aerodynamic Tip Desensitization of an Axial Turbine Rotor Using Tip Platform Extensions

Abstract: Aerodynamic losses due to the formation of a leakage vortex near the tip section of rotor blades form a significant part of viscous losses in axial flow turbines. The leakage flow, mainly induced by the pressure differential between the pressure side and suction side of a rotor tip section, usually rolls into a streamwise vortical structure near the suction side part of the blade tip. The current study uses the concept of a tip platform extension that is a very short “winglet” obtained by slightly extending the tip platform in the tangential direction. The use of a pressure side tip extension can significantly affect the local aerodynamic field by weakening the leakage vortex structure. Phase averaged, time accurate total pressure measurements downstream of a single stage turbine facility are provided from a total pressure probe that has a time response of 150 kHz. Complete total pressure maps in all of the 29 rotor exit planes are measured accurately. Various pressure and suction side extension configurations are compared against a baseline case. The current investigation performed in the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University shows that significant total to total efficiency gain is possible by the use of tip platform extensions.Copyright © 2001 by ASME

Analysis of Unsteady Blade Row Interaction Using Nonlinear Harmonic Approach

Abstract: An efficient non-linear harmonic methodology has been developed for predicting unsteady blade row interaction effects in multistage axial flow compressors. Flow variables are decomposed into time averaged variables and unsteady perturbations, resulting in time averaged equations with deterministic stress terms depending on the unsteady perturbation. The non-linear interaction between the time averaged flow field and the unsteady perturbations are included by a simultaneous pseudotime integration approach, leading to a strongly coupled solution. The stator/rotor interface treatment follows a flux averaged characteristic based mixing plane approach and includes the deterministic stress terms due to upstream running potential disturbances and downstream running wakes, resulting in the continuous nature of all parameters across the interface. The basic computational methodology is applied to the three-dimensional Navier-Stokes equations and validated against several cases. Results show that this method is much more efficient than the non-linear time-marching methods while still modeling the nonlinear unsteady blade row interaction effects.Copyright © 2000 by ASME

Single rotor turbine engine

Abstract: There has been invented a turbine engine with a single rotor which cools the engine, functions as a radial compressor, pushes air through the engine to the ignition point, and acts as an axial turbine for powering the compressor. The invention engine is designed to use a simple scheme of conventional passage shapes to provide both a radial and axial flow pattern through the single rotor, thereby allowing the radial intake air flow to cool the turbine blades and turbine exhaust gases in an axial flow to be used for energy transfer. In an alternative embodiment, an electric generator is incorporated in the engine to specifically adapt the invention for power generation. Magnets are embedded in the exhaust face of the single rotor proximate to a ring of stationary magnetic cores with windings to provide for the generation of electricity. In this alternative embodiment, the turbine is a radial inflow turbine rather than an axial turbine as used in the first embodiment. Radial inflow passages of conventional design are interleaved with radial compressor passages to allow the intake air to cool the turbine blades.

Improving the Efficiency of the Trent 500 HP Turbine Using Non-Axisymmetric End Walls: Part II — Experimental Validation

Abstract: Part I of this paper described how the HP turbine model rig of the Rolls-Royce Trent 500 was redesigned by applying non-axisymmetric end walls to both the vane and blade passages, whilst leaving the turbine operating point and overall flow conditions unaltered. This paper describes the results obtained from testing of the model rig and compares them with those obtained for the datum design (with conventional axisymmetric end walls). Measured improvements in the turbine efficiency are shown to be in line with those expected from the previous linear cascade research at Durham University, see Harvey et al. [1] and Hartland et al. [2]. These improvements are observed at both design and off-design conditions. Hot wire traverses taken at the exit of the rotor show, unexpectedly, that the end wall profiling has caused changes across the whole of the turbine flow field. This result is discussed making reference to a preliminary 3-D CFD analysis. It is concluded that the design methodology described in part I of this paper has been validated, and that non-axisymmetric end wall profiling is now a major new tool for the reduction of secondary loss in turbines (and potentially all axial flow turbomachinery). Further work, though, is needed to fully understand the stage (and multistage) effects of end wall profiling.Copyright © 2001 by ASME

Compressor capacity control system

Abstract: A method of controlling a compressor in a transport temperature control unit having a prime mover providing power to the compressor. The compressor has a power requirement that varies depending on loading conditions. The method includes determining the maximum power available from the prime mover, determining the power requirement of the compressor, and adjusting the loading conditions of the compressor so that the power requirement of the compressor substantially equals the maximum power available from the prime mover. Preferably, the method includes starting the compressor at a low speed, varying the suction pressure as permitted by the maximum amount of power available until the suction pressure reaches a maximum suction pressure setting, and after the suction pressure reaches a maximum suction pressure setting, increasing the speed of the compressor as permitted by the maximum-amount of power available.

Multi-Blade Row Interactions in a Transonic Axial Compressor: Part I — Stator Particle Image Velocimetry (PIV) Investigation

Abstract: Multi-blade row interactions in an advanced design 1&1/2 stage axial-flow compressor are experimentally investigated at both subsonic and transonic rotor operating conditions using particle image velocimetry (PIV). Transonic rotor operation had a significant impact on the downstream stator unsteady flow field due to phenomena associated with the intra-stator transport of the chopped rotor wake segments. In the stator reference frame, the rotor wakes have a slip velocity relative to the mean flow that causes the low momentum wake fluid to migrate across the vane passage and accumulate on the stator pressure surface as the chopped wake segments are transported downstream. This results in the generation of counter-rotating vortices on each side of the chopped wake segment that convect downstream with the mean flow and act as an additional source of unsteadiness to the vane pressure surface. These interaction phenomena are not evident in the PIV data at the part-speed compressor operating condition due to the much lower velocity deficit and hence slip velocity associated with the subsonic rotor wakes.Copyright © 2001 by ASME

System for estimating turbocharger compressor outlet temperature

Abstract: A system for estimating turbocharger compressor outlet temperature includes an engine controller responsive to any two of corrected turbocharger speed, corrected fresh mass air flow and turbocharger compressor pressure ratio (compressor outlet pressure/compressor inlet pressure) to compute compressor outlet temperature based on a corresponding compressor outlet temperature model.

Performance prediction of axial flow compressors using stage characteristics and simultaneous calculation of interstage parameters

Abstract: A new method for predicting performance of multistage axial flow compressors is proposed that utilizes stage performance curves. The method differs from the conventional sequential stage-stacking method in that it employs simultaneous calculation of all interstage variables (temperature, pressure and flow velocity). A consistent functional formulation of governing equations enables this simultaneous calculation. The method is found to be effective, i.e. fast and stable, in obtaining solutions for compressor inlet and outlet boundary conditions encountered in gas turbine analyses. Another advantage of the method is that the effect of changing the angles of movable stator vanes on the compressor's operating behaviour can be simulated easily. Accordingly, the proposed method is very suitable for complicated gas turbine system analysis. This paper presents the methodology and performance estimation results for various multistage compressors employing both fixed and variable vane setting angles. The ef...

Short and Long Length-Scale Disturbances Leading to Rotating Stall in an Axial Compressor Stage With Different Stator/Rotor Gaps

Abstract: The transient processes of rotating stall evolution have been investigated experimentally in a low-speed axial compressor stage with three stator-rotor gaps. The pressure traces at 8 circumferential locations on the casing wall near the rotor leading edge have been analyzed by the wavelet transforms. With the appropriate mother wavelets, the evolution of short and long length-scale disturbances leading to the stall can be captured clearly.Behavior of these disturbances is different depending on the stator-rotor gap. For the large and middle gap, the stall inception is detected by a spiky short length-scale disturbance, and the number of spiky waves increases to generate the high frequency waves. They becomes the short length-scale part-span stall cells at the mild stall for the large gap, while they turn into a big stall cell with growth of a long length-scale disturbance for the middle gap. In the latter case, therefore, the stalling process was identified with ‘high frequency stall inception’. For the small stator-rotor gap, the stalling process is identified with ‘long wave-length stall inception’, and supported the recent computational model for the short wave-length stall inception by showing that closing the rotor-stator gaps suppressed the growth of short length-scale disturbances.From the measurement of the pressure field traces on the casing wall, a hypothesis has been built up that the short length-scale disturbance should result from a separation vortex from a blade surface to reduce circulation. The processes of the stall evolution are discussed on this hypothesis.Copyright © 2001 by ASME

Casing treatment for compressors

Abstract: A cast assembly for a gas turbine engine compressor, the compressor including a plurality of axial flow stators and a rotor having a plurality of axial flow blades, each of the blades having a tip section and a leading edge. The assembly comprises a stator outer platform, a boss, a passage, a blade outer shroud and a circumferential slot. A boss is formed in the platform and includes a passage. The passage includes an inlet and an outlet. The inlet is disposed in the circumferential slot. The outlet being disposed upstream of the leading edge of the blades. The passage circumferentially converges inward from the inlet to the outlet. The outer shroud joins with said outer platform during the assembly of the compressor such that the circumferential slot is formed downstream and proximate to the leading edge of the blades. The circumferential slot is in flow communication with the inlet and converges axially.

Numerical simulation of the flow field in the vicinity of an axial flow fan

Abstract: The main purpose of the current investigation is the development and evaluation of a numerical model used to simulate the effect of an axial flow fan on the velocity field in the vicinity of the fan blades. The axial flow fan is modeled as an actuator disc, where the actuator disc forces are calculated using blade element theory. The calculated disc forces are expressed as sources/sinks of momentum in the Navier-Stokes equations solved by a commercially available computational fluid dynamic (CFD) code, Flo + + , The model is used to determine the fan performance characteristics of an axial flow fan as well as the velocity fields directly up- and downstream of the fan blades

Casing treatment for a fluid compressor

Abstract: An axial flow or centrifugal flow compressor having arrays of blades (16) extending across a working medium flowpath (18) includes a casing treatment for enhancing the compressor's fluid dynamic stability. In one variant of the invention the casing treatment comprises one or more circumferentially extending grooves (40) that each receive indigenous fluid from the compressor flowpath at a fluid extraction site (56) and discharge indigenous fluid into the flowpath at a fluid injection site (58), circumferentially offset from the extraction site, where the migrated fluid is better able to advance against an adverse pressure gradient in the flowpath. Each groove is oriented so that the discharged fluid enters the flowpath with a streamwise directional component that promotes efficient and reliable integration of the introduced fluid into the flowpath fluid stream (20). In a second variant of the invention, the casing treatment comprises a circumferentially extending compartment (62), typically comprising a voluminous pressure compensation chamber (64) and a single passage (66) circumferentially coextensive with the chamber, for establishing fluid communication between the chamber and the flowpath. The voluminous character of the compartment attenuates the inordinate circumferential pressure difference across the tips of excessively loaded compressor blades (16), making the compressor less susceptible to tip vortex induced instabilities. One embodiment of the pressure compensating variant includes a passage (66) oriented similarly to the groove (40) of the grooved variant of the casing treatment so that fluid flowing from the passage enters the flowpath with a streamwise directional component.

Motor-driven compressors

Abstract: A motor-driven compressor is formed integrally with a compressor device for compressing refrigerant and a motor for driving the compressor device. The motor-driven compressor includes a drive circuit and a plurality of cooling fins. The drive circuit controls the operation of the motor. The drive circuit is provided on an outer surface of a wall of a refrigerant suction route. The plurality of cooling fins are formed on an inner surface of the wall of the refrigerant suction route. In such motor-driven compressors, the drive circuit may be sufficiently cooled without using cooling devices. As a result, providing cooling devices with the drive circuit in motor-driven compressors is no longer necessary.

Axial flow fan having counter-rotating dual impeller blade arrangement

Abstract: A counter-rotating axial flow fan for cooling electronic components comprising two or more impellers with narrow chord blades. At least one impeller rotates in a first direction and at least one impeller rotates in a second direction opposite to the first direction. The blades of the impellers are configured so as to cause air to flow in the same axial direction. The air flow generated by this counter-rotating fan is substantially greater than the air flow of an otherwise identical co-rotating fan.

The Periodical Interaction of the Tip Clearance Flow in the Blade Rows of Axial Compressors

Abstract: Current models on the tip clearance flow in turbomachines only describe the time-averaged behaviour of the flow structures. However, the real tip clearance flow is periodically fluctuating in time. This fact has to be considered for the design of turbomachine bladings especially with regard to blade vibrations and tip clearance noise.Detailed experimental investigations on the time-resolved behaviour of the flow in the rotor blade tip region were carried out in a four-stage low-speed research compressor. A strong time-periodic interaction of the blade tip vortices of adjacent blades can be shown for relatively large tip clearance of the rotor blades for operating points near the stability limit of the compressor. The resulting flow pattern, which frequency is not related to the rotor frequency, moves along the blade row. It can be described as a multicell configuration with strongly fluctuating cell number and size. The structure and propagation of the flow instability can be summarized in a model of the periodic fluctuating tip clearance flow (Mailach et al., 2000).Additional experiments were carried out in a straight cascade to improve the understanding of this flow phenomenon. It can be shown by means of time-resolved measurements that the same disturbance exists for comparable inlet flow conditions in the blade tip region of the cascade. Flow visualizations show that the blade tip vortex is strongly fluctuating and moves sometimes ahead of the leading edge of the adjacent blade. The result of this is a short-lengthscale flow pattern, which is propagating along the blade row. These experiments confirm the model of the time-periodic tip clearance flow proposed for compressors. A Strouhal-number for the estimation of the frequency of the flow fluctuation will be presented, which includes both design and aerodynamic parameters.Copyright © 2001 by ASME

High-efficiency, inflow-adapted, axial-flow fan

Abstract: An efficient axial flow fan (2) comprises a central hub (6), a plurality of blades (8), and a band (9), and is designed to operate in a shroud (4) and induce flow through one or more heat exchangers (5) - in an automotive engine cooling assembly, for example. The fan blades (8) have a radial distribution of pitch ratio that provides high efficiency and low noise in the non-uniform flow field created by the heat exchanger(s)(5) and shroud (4). The blade (8) has either no sweep, or is swept backward (i.e. opposite the direction of rotation) in the region between the radial location r/R=0.70 and the tip (r/R-1.00). The blade pitch ratio increases from the radial location r/R=0.85 to a radial location between r/R=0.90 and r/R=0.975, and then decreases to the blade trip.

Gas turbine engine provided with foreign material removing structure

Abstract: PROBLEM TO BE SOLVED: To provide a gas turbine engine capable of having a structure downsized and inexpensive for removing foreign material by utilizing existing parts in the engine. SOLUTION: A collecting port 17 for making enter a foreign material E in the air A into the port 17 and introducing and discharging the foreign material E outside a curved passage 14 is formed on a diametrical outer peripheral portion of the curved passage 14 connected to a downstream side of a centrifugal compressor 1. A collecting port 39 is formed in a boundary portion between a top wall 37 and a peripheral wall 38 in an outer cylinder 11 of a combustion room C of a combustor 4. A collecting port 61 is formed on a compressor shroud 51 of an axial compressor 44.

Compressor Performance With Water Injection

Abstract: There has been renewed interest recently in the injection of water at inlet to gas turbine plants As is to be expected there is a drop in temperature at the inlet face to the compressor and this obviously has an effect on compressor performance But a second effect occurs within the early stages of the compressor itself, associated with an increase in the effective specific heat due to continuing evaporation of the water droplets Consequently there are movements away from design operating conditions on the stage characteristicsA one-dimensional analysis of compressor off-design performance is developed to illustrate these effects, which appear to be appreciable, even for very small quantities of water injectionCopyright © 2001 by ASME

Mixed flow and centrifugal compressor for gas turbine engine

Abstract: A two stage compressor with a mixed flow first stage, a centrifugal second stage, and an intermediate duct The centrifugal rotor (2) has a circumferential array of radially extending centrifugal flow blades (16) between the centrifugal flow hub and an associated centrifugal flow shroud An intermediate duct (3) has an inner duct wall (20) defining an axially curvilinear transition surface of revolution between anoutlet end of the mixed flow hub and an inlet end of the centrifugal flow hub and an outer duct wall (21) defining an axially curvilinear transition surface of revolution between an outlet end of the mixed flow shroud and an inlet end of the centrifugal flow shroud

Role of tip clearance flow on axial compressor stability

Abstract: Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2002.

Compressor starting torque converter

Abstract: A large compressor (18) is powered by a single-shaft gas turbine (12) via shaft (14), gearbox (16) and a hydraulic torque converter (10), which is undersized relative to the maximum shaft power requirement of compressor (18). The hydraulic torque converter (10) has a lock-up device (40) that locks the impeller (24) and the turbine wheel (28) at 25% of the maximum shaft power requirement of compressor (18). Gas turbine (12) has a starter (34). Optionally, compressor (18) has its outlet connected to auxiliary compressor (50) that assists the starting process by decreasing the back pressure of compressor (18).

Aerofoil for an axial flow turbomachine

Abstract: A turbine stator vane (41) for use in an axial flow gas turbine. The vane has an aerofoil the pressure face of which is convex between platform (45) and tip (46) regions in a plane (48) which extends both radially of the turbine and transversely of the general working fluid flow direction between the vanes. The trailing edge (43) of the aerofoil is straight from platform to tip, and the spanwise convex and concave curvatures of the aerofoil pressure and suction surfaces respectively are achieved by rotational displacement of the aerofoil sections about the straight trailing edge. However, the axial width (W) of the aerofoil is substantially constant over substantially all of the aerofoil radial height and the chord line at mid-height aerofoil sections (44) is shorter than the chord lines in aerofoil sections at platform or tip regions. Reducing chord length at the mid-height region in this way lowers aerodynamic profile losses without unduly affecting vane performance. Also disclosed is a turbine rotor blade designed to form a stage pair with the stator vane.

Three-dimensional wall jets: Axial flow in a stirred tank

Abstract: In this article, the flow at the wall of a stirred tank is compared with turbulent wall jet behavior. Agreement is shown to be very good. For all three axial impellers studied, the wall jet is three dimensional along the wall and baffle of the tank. The expansion of the jet is linear, and the maximum velocity decays with 1/z, where z is the dimensionless axial distance. These wall-jet characteristics help further the fundamental understanding and modeling of the bulk flow in a stirred tank and provide meaningful test data for CFD validation.

Downhole gas compression

Abstract: A downhole gas compression system is adapted for location in a bore of a natural gas-producing well ( 10 ), the system comprising an axial flow compressor ( 32 ) and a gas-filled electric drive motor ( 30 ). The motor drives the compressor to compress the produced gas, the compressed gas being directed upwardly through production tubing ( 20 ) to surface.