We examine a publication by Euler, Sur une nouvelle manière d’élever de l’eau propose par M. de Mour (On a new method to raise water proposed by Mr. de Mour), published in 1753, addressing a type of water sprinkler, consisting of an inclined tube with its lower end immersed into water, and discharging at its top, by turning a vertical axis to which the inclined tube is attached. In this publication, Euler uses pioneering approaches by applying the concept of mechanical power to estimate the power needed to drive the machine by the human force, and by measuring time by the length of a pendulum necessary to achieve one oscillation. Several design formulas were derived for the determination of the output of the machine, giving also measures for its construction, and supported at the end by a numerical example to show the feasibility of the proposition. This is, perhaps, one of the earliest attempts to design a rotating machine to raise waters.
The aim of the present study is to treat circular- and spiral-shaped viscous micropumps unitarily and provide guidelines for determining the appropriate micropump for performance requirements. Three-dimensional theoretical equations applicable to circular- and spiral-shaped micropumps were derived. Numerical simulations were also performed, and the results were compared with the theoretical results. The results were qualitatively consistent. By comparing the performances of the two micropumps, the spiral- and the circular-shaped micropumps are suitable in the ratio of outermost diameter to channel width c* < 0.2, and c* > 0.2, respectively. The theoretical performance for rotating disk-type micropumps was expressed in a unified manner. Furthermore, the design guideline was provided based on the theoretical method.
Fundamental models of air column resonant surge are proposed. It is assumed that the flow in the suction pipe is incompressible but the effects of compressibility and pipe friction are taken into account in the discharge pipe. The characteristic equation is derived and the differences of onset condition and frequency from those of extended Helmholtz resonant surge are discussed. A reflection model considering the wave reflections at the compressor and throttle is also proposed to obtain better understanding. The results of characteristic equation and reflection models agree nicely. The results are validated by comparisons with experiments.
Generally the boundary layer loss is recognized as the main loss in the cascade flow in actual turbomachinery. Therefore, the loss in the other area outside the boundary layer which we call a mid-flow was often neglected. However, in the present paper, the mid-flow loss evaluation is conducted again to verify if it can really be neglected with all conditions. As a result, it is surely verified that the mid-flow loss can be negligible with higher pressure conditions. However, with lower pressure conditions, it is verified that the mid-flow loss can occupy several tens of % of the total loss; therefore, it cannot be neglected and it is effective to reduce the total loss by reducing the mid-flow loss with these conditions. Moreover, it is verified that the mid-flow loss has the characteristic in which it is inversely proportional to the chord for the identical solidity cascade flow; therefore, it is verified that wide chord cascade can reduce the mid-flow loss. Hence, the wide chord cascade can reduce the total loss in actual turbomachinery.
The theoretical study and numerical analysis have been carried out on the valve plate geometry of the radial piston pump to reduce the flow and pressure fluctuation. The radial piston pump is widely used in industrial applications as a hydraulic power source. The pressure and flow fluctuation of pump produce an adverse effect for the hydraulic system. The geometries of valve plate are studies for the analyses of pressure and flow fluctuation of the pump. The explicit area calculation of the piston kidney over the manifold is carried out to simulate the main flow in between piston chamber and manifold in vale plate configurations of with silencing groove, without silencing groove and with silencing groove cum damping orifice. The analyses of cross-port leakage is done at transition zone near at top dead centre (TDC) and bottom dead centre (BDC) of the valve plate, study the effects of cross-port leakage on pressure and flow fluctuation with volumetric efficiency of the pump. Studies the pump pressure and flow build up characteristic under varying load and validated with existing pump performance. The simulation results suggest that the silencing groove valve plate model is better perform than other configurations in terms of high flow rate, low pressure and flow fluctuation with less cross port leakage and more volumetric efficiency.
The introduction of air is often used in engineering to delay the occurrence of cavitation. A steady simulation on a single-stage and single-suction centrifugal pump was used to study the influence of the air on the internal flow under cavitation condition at 1% inlet void fraction. Steady simulation based on SST k-ω turbulence model and Rayleigh-Plesset cavitation model included in Ansys CFX 17.0 were processed to obtain vapor volume fraction, gas volume fraction and the turbulent energy of the impeller under the condition of natural cavitation and cavitation with entrained air. A homogeneous two-phase flow model was adopted to describe the air-water mixed flow. The experimental cavitation performance curve provides boundary condition support for the numerical simulation. In conclusion, it shows that the head of the pump keeps steady after 1% air entrained like natural cavitation. Then it goes worse when the cavitation number decreases but with lower NPSHr which means cavitation performance is improved by 1% air entrained. It indicated that the entrained air changes the distribution of the vapor in the passage of the impeller. However, the descent of the pressure over a certain value will also do harm to the internal flow of the model pump whether it is ventilating or not. The internal flow of the pump will be seriously damaged and even be blocked completely due to more and more vapor generated causing a dramatic decline of the head.
During operation and working of turbo machines, axial thrust balancing is important. To control and balance the axial thrust, a very simple method using shallow radial grooves mounted on the casing wall, called “J-groove”, was proposed, and studied experimentally. This paper presents a numerical study of the effect of J-groove on the flow in the narrow gap along enclosed rotating disks based on open-source CFD software. It is seen that the difference in pressure between the hub and shroud tip is increased with the increasing number, depth, and length of J-groove. But in the case of increasing width of J-groove, the pressure loss along the radius decreases when the ratio of the groove width to the outer radius W is less than 0.2 and increases when W greater than 0.2.
In this paper, the adjustable blade axial-flow fan is taken as the research object, and the primary aerodynamic design of the fan is carried out by the cascade method. Numerical calculation method is used to verify the aerodynamic performance of the preliminary design fan. The paper uses surrogate model and optimization algorithm to optimize the rotor of the preliminary design fan with a single objective, based on which the multi-objective optimization of the variable operating performance of the stator is carried out. The optimization results show that the total pressure and total pressure efficiency of the fan are significantly improved, and the bend angle and lean of the blade can improve the load distribution of the rotor and enhance the work capacity of the rotor. The optimization results for the stator reveal that there is a strong connection between the rotor and stator, and that a reasonable stator stagger angle will improve the variable operating performance of the fan.
In this work, we investigate an experimental study to measure the pressure jump and the axial pressure jump gradient at gas-liquid interface. The measures have been carried out along Dumitrescu-Taylor bubble length leading to gas-liquid interface. The difference of pressure between liquid and gas is very small and consequently its measurement is fastidious. To our knowledge, no experimental measurements on these two parameters have been reported previously. Interesting to access to this smallest pressure difference between liquid and gas, an experimental method has been implementing. We described this method for after to give measurements that can be used as quantitative prediction for such interfacial conditions on the modeling of the interfacial closure relations in two fluid models. The original results of recording signals show that the pressure jump depends on the distance with respect to the bubble nose and it increase with the bubble velocity. The same trend observed for the axial interfacial pressure jump gradient results. For fixed bubble, an order of magnitude of those last parameters is given. The experimental value of the pressure jump across the interface agrees very well with the calculated value from the Laplace’s capillary equation. This good agreement gives confidence in our measurements. Other measures are carried out to determine the pressure jump at the bottom of the bubble, which is compared to the calculated values.
The pressure distribution law and calculation of impeller side cavity is one of the important topics in the pump industry, but there is no more accurate calculation method at present. On this basis, a mathematical model of pump cavity pressure distribution and balance cavity pressure under design conditions was derived in this paper. By changing the radial clearance of front and back sealing rings and the diameter of the balance hole on the same impeller, the pressure distribution of front and rear cavities and the balance cavity pressure of the pump were systematically tested by a specially designed device. In the test, the curve of pressure loss coefficient and relative radius of pump cavity under different sealing ring radial clearance was obtained, which could solve the calculation problem of the pressure distribution of front and rear pump cavities. The test curve of the relationship between flow coefficient ratio and specific surface area essentially reflected the coupling regulation effect of balance holes and the rear sealing ring on the balance cavity pressure, which could not only solve the calculation problem of the balance cavity pressure, but also provide the theoretical basis for controlling the pressure and cover force of balance cavity and select different combinations of the radial clearance of the rear sealing ring and the diameter of balance holes. The results showed that the theoretical prediction value was more consistent with the actual measured value, which proved that the proposed mathematical model has high accuracy and universality. This study provides a new way to more accurately calculate the pump cavity pressure distribution and balance cavity pressure and laid a theoretical basis for the study of impeller cover force with significant academic and application value.
In order to study the flow law of shunt vane type aviation fuel pump under the condition of gas-liquid mixture transportation, based on the RNG K-ε turbulence model and the Euler-Euler non-uniformity model, using the ANSYS CFX software to calculate an aviation fuel pump under different gas content conditions, and analyzing the flow of the fuel pump and the pressure law of the blade pressure. The research shows that the gas phase is mainly distributed in the front section of the long blade suction surface and the back section of the short blade pressure surface. The increased gas content will result in increased liquid velocity in the pump, which makes the gas phase gradually develop towards the suction surface of long and short blades and diffuse to the impeller flow path. The gas content mainly affects the pressure surface load of the fuel pump blades. The pressure load curve fluctuates at the relative position of the short blade (0.5-0.6) and long blade (0.3-0.6) as well as at the end of the blade and decreases with the increase in gas content. The change of pressure fluctuation of the blade is mainly reflected at the junction of long and short blades, and the pressure fluctuation amplitude of the front section of the short blade and middle section of the long blade fluctuates greatly. With the increase in gas content, the pressure fluctuation amplitude at each monitoring point reduces. The research results can provide some reference for the design of aviation fuel pumps.
Pico scale Turgo turbine (PSTT) is proper as a power plant to be applied for remote areas because of its simple construction, cheap investment cost, and good performance above 35%. However, the design of PSTT is still based on estimation because the wheel diameter and nozzle diameter (D/d) ratio are not yet in reasonable agreement. Furthermore, the literature on D/d affects PSTT performance has not been comprehensive. Accordingly, this study investigates the relation of D/d on PSTT performance and its effect on the U/Vjet. Based on experimental results, the relation of D/d and U/Vjet to PSTT performance is parabolic (expressed by polynomial quadratic); the maximum configuration of D/d of 22, and U/Vjet between 0.42 to 0.47.