Fluid Machines Research Articles

Integration of advanced high-pressure pumps and energy recovery equipment yields reduced capital and operating costs of seawater RO systems

High-pressure pumping and brine energy recovery equipment account for as much as 40% of the capital costs in seawater reverse osmosis (SWRO) desalination systems. Energy consumption by the high-pressure feed pump accounts for at least 35% of the operating costs. Recently developed equipment integrates into one package the function of high-pressure pumping, energy recovery and control of feed and brine flows resulting in a substantial reduction in capital and operating costs of SWRO systems. The integrated equipment package is based on proven technology blended with state-of the-art fluid machine design and clever integration of numerous components heretofore installed individually in SWRO systems. This package will make a substantial contribution toward the reduction of capital and operating costs for SWRO systems with capacities between 50 and 500 m 3/d permeate production per train.

From the Crystal Palace to the Pump Room

This article discusses centrifugal pumps and compressors that have reached efficiency levels above 90 percent and are built in sizes ranging from a few watts to megawatts. As machines have evolved to handle a wider range of liquids and gases at higher pressures and temperatures, whole industries have become dependent on them. The centrifugal impellers in these pumps and compressors make them among the most complex fluid machines ever built. The development of the centrifugal impeller has been helped because the device can be used in both pumps and compressors. The earliest development occurred in pumps, which were more advanced than compressors until early in the 20th century.

Experimental Study on Passive Control of Pseudo-Shock.

It is well known that the pseudo-shock in the straight duct oscillates severely, and causes vibration and noise of fluid machines. In the previous paper, the performance of the diffuser is shown to be improved by the passive control method without noticeable changes of the pseudo-shock stracture, and a new passive control method of the pseudo-shock useing the bypass system was proposed. In the present paper, the effectiveness of these methods for the oscillation suppression of the pseudo-shock was investigated exprimentally. Both of these methods can suppress the wall pressure fluctuation, reducing the pressure gradient and the shock oscillation amplitude.

Calculation of Three Dimensional Boundary Layer in Francis Turbine Runner.

It is important to estimate friction loss with high accuracy in order to predict the performance of fluid machine such as water turbine. However, the influences from secondary flow and the upstream flow in boundary layer are not considered in previous methods. Here, a finite difference method for 3 D boundary layer equations is applied to the case of Francis turbine runner. The velocity distribution along main flow direction is assumed as 1/n power law model, and Mager model is used for the secondary flow.

CHARACTERIZATION OF FLUID MACHINES AS ACOUSTIC MULTI-PORT SOURCES

The aim of the work reported in this paper was to study the characterization of fluid machines (e.g., fans, pumps) as sources of fluid-borne sound in connected pipe or duct systems. Of special interest is the possibility of extending earlier published methods beyond the plane wave region: i.e., to include higher order modes effects. For machines which can be modelled as an acoustic multi-port source, a method which makes it possible to measure the source data is suggested together with a modal decomposition technique. In order to verify and test the measurement method and modal decomposition technique, measurements were first carried out on a small test-rig without flow, with an ordinary loudspeaker as a source. Then the method was tested on an axial fan mounted to the end of a duct. In both cases ten microphone positions, divided equally between two duct cross-sections, were used to separate the waves (five modes) into left- and right-going components. It was verified that the measured source data can be used to predict the sound field created by the fan at a given acoustic load.

A study of planar orbiting mechanism and its applications to scroll fluid machinery

The law of gearing plays a very important role in the mechanism and machine design. On the contrary to a gear which usually rotates about its own axis without translational motion, the planar orbiting mechanism moving around a circular orbit without self-rotation is also an important mechanism. It has the ability of changing its enclosed fluid volume and therefore can be applied to fluid machines such as pumps, compressors and engines. In this paper, some elementary theorems related to the design of planar orbiting mechanisms are proposed and proved. Applications based on these thethese theorems are discussed. Two examples in the design of scroll fluid machines are particularly illustrated; one of which focuses on the geometric scroll shape design and the other points out a way to construct the so-called perfectly meshing scroll profiles.

A measurement method for determining the source data of acoustic two-port sources

Acoustic source data for fluid machines are of importance for calculating the acoustic field generated in a duct system and for analysis of source-load interaction effects. In this paper the problem of measuring source data for acoustic two-port sources in general is first described and critically discussed. A measurement method to determine the source data of an acoustic two-port source in the form of a source strength vector and a scattering matrix is then presented. This method consists of two steps. First the scattering matrix is determined by using external noise sources to create two independent acoustic test cases. As the second step, the source strength is determined by using a number of different acoustical loads to obtain an overdetermined problem. By solving the overdetermined matrix problem one can improve the prediction of the source data and it is also possible to verify whether or not the machine under test behaves as a linear source. For this purpose a special linearity measure has been defined. The measurement method has been verified and also successfully tested on an axial flow fan.

Pressure drop for flow in channels subjected to strong system rotation

A disc stack centrifuge is an industrial example of a fluid machine in which all the internal flow takes place in a rapidly rotating frame. The present report gives a survey of the experimental and theoretical work performed at Alfa-Laval in order to estimate the pressure drops in the different internal passages in the centrifuge, including both laminar and turbulent flow. For the laminar flow between the discs, a theory has been developed using the concept of a rotating Hele Shaw cell and conformal mapping. The theory is valid in the limit of very small Rossby numbers. For moderately large Rossby numbers, this model overestimates the pressure drop. The linear theory was extended by introducing advecting vortices in a computer model. The vortices cause vertical fluid transport between the Ekman and geostrophic layers by Ekman pumping, an effect which decreases the pressure drop in the disc stack. The linear model and the enhanced model have both been confirmed by experiments. The flow is turbulent in most parts of the centrifuge, except in the disc stack. The theoretical or numerical modelling for rotating turbulent flows is very difficult and no reliable models exist so far. We therefore have to rely on measurements, which show that the pressure is significantly influenced by rotation for Rossby numbers below unity.

Study on Scroll Profile based on Algebraic Spiral for Scroll Fluid Machines

Study on Scroll Profile based on Algebraic Spiral for Scroll Fluid Machines

Numerical calculation of the dynamic behavior of solid particles through the inlet box with complex geometry of a fluid machine

A finite element method is used to calculate the three-dimensional gas flow field in the inlet box of a large-size fluid machinery. The dynamic behaviors of solid particles through the inlet box are obtained numerically by the “one way coupling” method. The trajectories of different-sized particles and the distribution of particle positions on the outlet plane of inlet box are investigated.

Study on Scroll Profile for Scroll Fluid Machines

Study on Scroll Profile for Scroll Fluid Machines

Internal Flow of Fluid Machines

Internal Flow of Fluid Machines

Flow through Narrow Clearance between Rotating Cylinder and Stationary Wall

It is important to estimate the leakage flow rate through a rotor clearance of positive-displacement type fluid machine and flowmeter. In order to :make clear the flow through the top clearance between the lobe rotor and the easing wall not only in laminar regime but also in turbulent regime, experiments are carried out by using a model passage composed of a rotating cylinder and a stationary straight wall. In the laminar regime, the leakage flow rate through the top clearance is estimated theoretically. When the cylinder is at rest, the transition from laminar to turbulent flows occurs at Reynolds number Re=150 based on the minimum clearance and the mean velocity in it. The effect of the rotating direction and speed on the critical Reynolds number is also discussed. In the turbulent regime, the empirical equation for the leakage flow rate is obtained.

温度測定による流体機械性能判定法調査研究分科会報告

温度測定による流体機械性能判定法調査研究分科会報告

Mathematical modeling of multicylinder compressor discharge system interactions

Gas oscillations are complicated in a multicylinder compressor discharge system because of the cylinder interactions. These are identified and modeled here as kinematic and geometric types of coupling. The kinematic coupling effect is incorporated with the input volume velocities, at the values, which are derived from the discharge mass flow rates. To account for the geometric interactions arising because of the interconnected cavities and passages, impedance matrices are formulated. The discharge system components are described by steady state acoustic impedances, in distributed parameters format. The overall discharge system mathematical model (in the frequency domain) is then coupled with the time domain compressor cylinder thermodynamic, and valve fluid and structural dynamic models. An iterative is used to account for the back pressure effect. The theory is applied to a two cylinder high speed refrigeration compressor. Unsteady flow pressures are predicted in the valve chamber (for capacity and energy consumption considerations), and at the manifold end (for muffling effectiveness consideration). Excellent agreements between theory and experiment are obtained. The technique as outlined in this paper should be applicable to any multicylinder/interstaged positive displacement type of fluid machine.

Pipe Flow under the Influence of Coriolis is Forces

Fluids moving radial through a rotating channel receive the effect of Coriolis force, and it generates a secondary flow which modifies the distributions of the primary flow velocity. Investigations on this problem are absolutely necessary for the improvements of fluid machines, but the available data are very few because of the difficulties of the experimental works. This paper concerns the hydraulic losses and velocity distributions in a U-shaped rotating channel with a circular section. The losses are found to increase with the rotational speeds when the flow velocity of water is kept constant. The losses are expressed as the ratio of the rotational speeds to the flow velocity. Physical meaning of this ratio on the losses is clarified by the measurements of velocity distributions. When the water moving in the axial direction of the rotating channel is turned in the radial direction, as in the impeller of a fluid machine, the primary flow velocity loses its uniformity and the uneven distribution of velocity causes a peculiar flow changing sinuously along the channel. The detailed nature of this flow is also discussed.

Fluid Friction and Leakage between a Stationary and Rotating Disc

This paper describes an investigation of the flow in a narrow gap between a rotating and stationary disc with an arbitrarily imposed radial pressure difference. This system represents the conditions pertaining between the rotors and casings of many fluid machines. The investigation is mainly experimental, for although the equations of motion were derived for the fluid system in question, these were found not to be tractable for the conditions observed. Experimental results are reported from two separate test series. The first test series yielded data on the frictional and pressure forces in the system which were obtained in sufficient detail for use in design calculations for fluid machinery. In the second series the flow between the discs was studied in detail in order to explain the nature and form of the results obtained in the first series of tests.

Current Technology of Radial-Inflow Turbines for Compressible Fluids

Radial turbines have been used for hydraulic, steam, and gas turbine service. In hydraulic turbine practice, a substantial regime of specific speed is reserved exclusively for Francis turbines. No similar situation is found with compressible fluids, where axial turbines are used for the entire specific speed range of practical interest. Francis turbines consistently achieve efficiencies of 90–94 percent, but their counter parts in compressible fluid machines generally are thought to be inferior to axial turbines in performance. Review of available data indicates that radial inflow turbines with compressible fluids can approach or equal the performance of equivalent hydraulic turbines and that, in the specific speed range to which they are applicable, they can match axial turbine performance. Criteria are given which may be used for determination of the suitability of radial turbines for specific requirements.

On the Necessity of Unsteady Flow in Fluid Machines

It is shown that work can be done on, or by, a fluid in a frictionless flow process only if the flow is unsteady. The implications of this conclusion in the analysis of fluid machinery, and provisions which must be made in analysis to account for unsteady flow, are discussed.

Visco-type (Friction-type) Fluid Machines, Together with the General Theory

Visco-type (Friction-type) Fluid Machines, Together with the General Theory