Small Vane Research Articles

Numerical Simulation of Internal Flow Field of Self-Designed Centrifugal Pump

The two self-designed of centrifugal pump with small vane and centrifugal pump without small vane were simulated numerically to select a centrifugal pump with higher efficiency. The internal flow characteristics of the centrifugal pump was simulated by using Reynolds time-averaged N-S equation and RNG turbulence model to obtain pressure and velocity distribution and the cavitation characteristics were simulated by using SST turbulence model and Schnerr-Sauer cavitation model to obtain the gas volume fraction distribution. The results show that at the same flow rate, the change of velocity in the pump cavity of centrifugal pump with vane is smoother and the gas volume is less, but the back-flow is aggravated near the small vane, especially when interacting with the tongue, and a large amount of gas is generated at the suction surface of the small vane. In addition, the efficiency of centrifugal pump without vane is higher than that of centrifugal pump with vane, which provides a basis for the structural optimization of centrifugal pump.

입구베인 각도에 따른 터보블로어 성능특성 연구

Turbo blowers are mainly used in refuse collection systems. We discuss blower performance in relation to the angle of the inlet vane installed at the upstream of the blower. The flow characteristics of the components are analyzed by three-dimensional Navier-Stokes analysis and compared to experimental results. A two-stage serially connected turbo blower is introduced to analyze the performance experimentally. Throughout the experimental measurements and the numerical simulation, the distorted inlet velocity generated in the small vane angle reduces the performance of the blower, because of the local leading-edge separation and the resulting non-uniform blade loading. We also perform a detailed flow analysis using the results obtained in the numerical simulation.

Optimal operation of turbo blowers serially connected using inlet vanes

Optimal operation of the turbo blowers having an inlet vane has been studied to understand the blowers’ operating performance. To analyze three-dimensional flow field in the turbo blowers serially connected, general analysis code, CFX, is introduced in the present work. SST turbulence model is employed to estimate the eddy viscosity. Throughout the numerical analysis, it is found that the flow rates of the turbo blowers can be controlled at the vane angle between 90 (full open condition) degrees and 60 degrees effectively, because pressure loss rapidly increases below 60 degree of a vane angle. Efficiency also has almost the same values from 90 degrees to 60 degrees of a vane angle. It is noted that the distorted inlet velocity generated in the small vane angle makes performance deterioration of the turbo blowers due to the local leading edge separation and the following non-uniform blade loading.

Understanding and improving the convective cooling of brake discs with radial vanes

Detailed computational fluid dynamics (CFD) analyses of airflow and convective heat dissipation from a standard disc with radial vanes gave vital information regarding its weak points. Heat transfer from vanes is found to be particularly non-uniform, offering the largest scope for increasing local and average values of the coefficient of convective heat dissipation. A relatively simple modification — installation of an additional small vane (per channel, between the existing vanes) — demonstrated the ability to increase convective cooling from the ventilation channels. The radial position of these additional vanes was altered from disc ID towards OD, and best results were obtained with the vanes placed at the channel outlets (OD). An improvement in the total convective cooling (product of the average convective heat transfer coefficient and the entire disc wetted area) of nearly 14 per cent was achieved. In spite of better cooling, the new design has lower mass (air) flow when compared with the baseline design. The results are also presented in the form of Nusselt numbers, enabling their wider use. Conducted validation provided strong confidence in the accuracy of the results when searching for new solutions.

Comparison of Anti-Stall Effect of Two Diffusers in a Centrifugal Compressor.

The anti-stall effects in two diffusers, a vaned diffuser with fixed small vanes and a low-solidity cascade diffuser, were compared in a centrifugal compressor with suction damper. These diffusers had the same outer diameter. The surge limit flow rate did not differ, however, the stability differed. To clarify the difference of stability, pressure measurement and numerical simulation were carried out. In the vaned diffuser, the flow guided by the small vane pushed back the flow from down stream of throat. This mechanism suggests instability near surge point. In the low-solidity cascade diffuser, there observed no backflow on the whole suction surface. This suggests the more stable character.

Decrease of Pressure Loss in BWR Steam Separator (1)

Numerical analysis and air-water test were performed in order to evaluate gas-liquid separation characteristics in a BWR steam separator. Centrifugal force and flow quality were simulated in the test. Simulation of plant operation conditions was not sufficient at low volumetric flux due to large effect of gravity force. Pressure loss coefficient agreed with the plant conditions within 10%. Carryover agreed well with plant conditions for a current separator but was under-estimated for a separator with small vane angle. Calculated gas-liquid behavior agreed well with plant condition data in the 1st stage but calculated results over-estimated carryover. Combination of calculated results in the 1st stage and simulation test results in the 2nd and 3rd stages gave good prediction for carryover.

Geotechnical properties and behavior of high-porosity, organic-rich sediments in Eckernförde Bay, Germany

The organically rich, fine-grained, very soft, high porosity sediments in the inner portion of Eckernförde Bay, Germany have varying amounts of methane gas, with the horizon of gas fluctuating vertically on a seasonal cycle. The sharp vertical gradient in water content, with values exceeding 500% at the sediment–water interface, and corresponding gradient in density can be expected to cause a significant subbottom acoustic impedance contrast in these surficial sediments. Equations are presented to characterize geotechnical property variations of the upper 5 m. The upper 1.5 m exhibits appreciable ‘apparent’ overconsolidation with a trend toward a normally consolidated stress state at 2.5 m depth. The coefficient of permeability of the upper 40 cm is low (4×10 -6 cm s -1) and the sediment is highly compressible with compression indices of 2.7–6.8. Triaxial compression test results indicate that the sediment behaves as a normally consolidated clay with a low friction angle (22°). The rheological behavior of the upper 20–30 cm, determined with a small vane device, is indicative of a shear-thinning material, implying that the resistance to penetration decreases with increasing velocity.

Autorotation of polygonal prisms with an upstream vane

Abstract It has recently been shown that autorotation of bodies, with their axes normal to the airstream, is exhibited by bodies with polygonal sections having up to seven sides. In this work it is shown that the rotational speed can be enhanced, and prismatic bodies that do not autorotate on their own will do so, with the addition of a fixed upstream vane. Furthermore, it was found that the direction of rotation would change once for small vane gaps and three- and four-sided models as the vane angle is changed monotonically, but that three changes of direction were exhibited by bodies with five or more sides. For large vane gaps no changes in direction are exhibited, although for a five-sided body and intermediate gaps a case of two changes in direction was also recorded, and evidence of alternative final steady states arising from a given initial state was noted. Lift and drag coefficients for some of the cases are reported.

Studies with Centrifuge Vane and Penetrometer Apparatus in a Normal Gravity Field

Abstract Small vane and penetrometer devices have been developed to measure soil properties in models during centrifuge operation. To aid the interpretation of vane data from centrifuge models a series of tests was conducted in cakes of kaolin clay in a normal gravity field. In the experimental program the effects of disturbance during insertion, delay between insertion and rotation, rate of rotation and geometry of vane blades were investigated. The results were used to devise a scientific method of operation of the vane apparatus. Subsequent tests were all performed with a vane size of 18 mm diameter by 14 mm high. Penetrometer tests were conducted in cakes of kaolin and Gault clays. Vane shear strengths were used to calibrate the apparatus. The ratio of cone resistance to vane strength was found to increase with increasing over-consolidation ratio. The values also differed considerably between the two clays. Thus, while the penetrometer has the advantage of providing a continuous profile of resistance with depth, some care is required in converting this measurement into undrained shear strength.

Determination of optimum geometrical parameters of stators of turbine expansion engines

The efficiency of the stators of centripetal radial turbine expansion engines, characterized by the small dimensions of the flow section have been studied. The study is extended to obtain data on the variation of the losses in relation to the relative geometrical parameters. Investigations have been carried out into the level of the total losses in the wing-shaped small vane stator and its geometrical parameters are optimized. The processing method accepted for the calculations is based on the equations of the unidimensional theory of the gas flows which gives sufficiently reliable results.

Small Cone Penetrometer Tests and Piezocone Tests in Laboratory Consolidated Clays

Abstract Small vane, 10-mm-diameter cone penetrometer and 12.7-mm-diameter piezocone devices have been developed to measure soil properties in centrifuge models during flight. This paper presents tests with these devices on kaolin and Gault clay in a normal gravity field. Empirical cone factors were shown to increase with increasing overconsolidation ratio but were found to depend on other factors such as cone size and testing rates. The values also differed considerably between the two clays used. Tests with the small piezocone have shown that the ratio of pore pressure to point resistance decreases slightly with the overconsolidation ratio, but not enough for this ratio be used as a method for determining overconsolidation ratio (OCR). As shown by other workers, pore pressures acting around the tip influence measured tip resistance and should be taken into account when interpreting cone resistances in clays. Dissipation tests with the piezocone have yielded values of coefficient of consolidation agreeing very well with those from swelling tests on clay cakes.

Unsteady effects in mechanically-excited turbulent plane jets

Two methods of mechanically exciting a plane turbulent free jet are described; periodic perturbatin of the nozzle exit velocity, and forced oscillation of a small vane located in the het potential core. Hot-wire measurements obtained by conditional sampling techniques indicated that the flow fields of the two jets are substantially different although they have the same Strouhal number of 0.0032. While the mean flow development of the pulsed jet can be described adequately by a quasi-steady model, the vane-excited jet exhibits unsteady effects which depart significantly from quasi-steady approximations such as increased entrainment, amplification of excitation and non-linear effects in the form of the presence of high harmonics. The constancy of momentum flux has been examined in both the steady and unsteady jets

Vane Stagger Angle and Camber Effects in Fan Noise Generation

The problem of sound generated by the interaction of velocity disturbances with stator vanes in an annular duct is considered theoretically. The duct carries a uniform subsonic main flow and is assumed to be anechoic. In this problem it seems consistent to model the vanes by flat plates parallel to the duct axis. However, this modeling may yield an unrealistically low acoustic power. In the present paper, a nonplanar lifting surface approximation of the vanes shows that at frequencies prevailing in current turbofans even a small vane inclination significantly affects the sound generation process. The lower the circumferential periodicity \m of the cut-on sound field, the more pronounced are the acoustic effects of vane stagger angle and camber. Calculations for a typical example of a turbof an stator show at \m = 1 a rise of 23 dB in upstream acoustic power when the stagger angle is increased from 0 to 15 deg. Furthermore, even at \m - 16 there is still a rise of 5 dB. Besides the acoustic power, the modal distribution of the sound field is very sensitive to vane camber and stagger angle.

A Full Shift True Breathing Zone Air Sampler and Its Application to Lead Workers

A completely head-mounted full shift dust sampler for monitoring the lead-in-air concentration in a lead worker's actual breathing zone is described. A small filter head is positioned within 5 cm of the mouth and nose on an adjustable stalk. Air is drawn through a 1.25 cm diameter glass fibre filter at a rate of 0.51/min by a small rotary vane pump.Initial comparisons with a conventional lapel-mounted UKAEA head powered by a Casella pump show that the average lead-in air concentration in the true breathing zone can be significantly different from that around the lapel.

A Full Shift True Breathing Zone Air Sampler and Its Application to Lead Workers

A completely head-mounted full shift dust sampler for monitoring the lead-in-air concentration in a lead worker's actual breathing zone is described. A small filter head is positioned within 5 cm of the mouth and nose on an adjustable stalk. Air is drawn through a 1.25 cm diameter glass fibre filter at a rate of 0.51/min by a small rotary vane pump. Initial comparisons with a conventional lapel-mounted UKAEA head powered by a Casella pump show that the average lead-in air concentration in the true breathing zone can be significantly different from that around the lapel.

Experience in the operation of large axial-flow pumps on main canals

1. Operating experience and full-scale investigations made it possible to evaluate the effectiveness of designs that have been adopted and to formulate the main requirements imposed on the design of pumps and pressure pipes for pumping stations intended to operate in a sequence on main canals. Among the priority tasks to provide reliability of large pumping equipment with respect to parameters and performance are: provision of a high accuracy in the manufacture and assembly of the working elements and flow part of pumps; consideration when designing pumps of the conditions of their interaction with pipelines in transient and steady regimes. 2. To reduce the fluctuating loads on the pump and to limit the starting currents in the motor at small heads, the pumps should be started at small vane angles. In the case of large starting heads, with the danger of falling into an unstable operating regime when the vacuum-breaking valve is open, and also with horizontal inserts at the beginning of the pressure pipes, the pump should be started at medium or even large vane angles, which may be determined by full-scale tests. Horizontal inserts at the beginning of the pipe should be avoided at new stations being designed. 3. The pump should be stopped if necessary to bring it out of the saddle regime and then started at a large vane angle. 4. Pumps with a hydraulic drive for turning the impeller vanes should be stopped at large vane angles. This reduces the magnitude and time of action of dynamic loads, increases pump reliability, and lengthens its service life.

A new recording wind vane

New techniques applicable in the design of remote recording wind vanes are presented, and two preferred systems are described in detail. A small Duralumin vane is coupled to the shaft of a continuous rotation potentiometer, which may be a high resolution wire wound instrument, or constructed from a low-torque rotary switch. In one system the potentiometer has provision for alternative inputs, the supply voltage being automatically switched from one input to the other following a positional triggering action of the moving contact. Another technique utilizes a step potentiometer with one supply position, the sign of the output reference voltage being automatically changed as the wiper traverses the input connections. The outputs of the transducers change progressively over ranges of up to two revolutions of the shaft, and when range extremities are reached, revert to voltages which correspond to angular changes of 360°. The overlap provided prevents an incoherent recording which would otherwise be obtained when the moving contact reaches the ends of the track. A complete instrument weighs 350 g, has a vane 25 cm long and operates in winds down to 25 cm s−1 and the systems are well suited to automatic weather station operation.

A diver-held vane-shear apparatus

An inexpensive instrument, consisting of a small vane attached to the shaft of a calibrated torque screwdriver, has been developed for measuring the shear strength of sea-floor sediments. It can be used either in situ or on sediment samples removed to the ship or laboratory.

Low speed anemometer

A moving-coil milliammeter has been modified by fitting an extended arm and a small vane to the movement. Air loads on the vane are resisted by applying current to the moving coil, this current then serving as a measure of the air speed. The range of the instrument is 0.2 to 4.5 ft sec-1.

A proposed method of microwave power measurement

The paper describes the basic principles of a new method of microwave power measurement. According to the proposed method, the microwave power is converted into heat by a power-dissipating element placed in a waveguide. Around this element a closed air duct is formed with vertical upward and downward branches. The air heated by the dissipative element causes a deviation of a small vane placed in the duct and suspended on a horizontally stretched torsion filament, and the angular displacement of a mirror mounted on this vane is observed through an autocollimator.