One of the most important ways to manage consumption is to reduce non-revenue water and losses in urban and rural water supply systems. The inaccuracy of the meters can have direct impact on the evaluation of loss water control programs as well as resource conservation programs thereby leading to incorrect decisions. In this paper, for numerical simulation of the effect of direct pump installation on the performance of domestic water meters, a turbine water meter of multi-jet production type is selected. It is assumed that the values of the mechanical brake torque on the impeller, such as the bearing friction drag torque, and magnetic magnitude is insignificant and can be considered as zero. The input and output flow are the fully developed in the water meter where K-ω-SST turbulent model is selected and the rotational speed of the impeller is collected at different flow rates. Comparing the numerical solution results with the manufacturer's practical experiments data, reveals the maximum error of 9.66%. Thus, the model can be used to evaluate the effect of direct pump installation on the performance of domestic water meters. As a real-world case, the water meter performance when the centrifuge pump is directly inserted into the outlet of the water meter is simulated and the results were compared with the non-pumped state. the behavior of the water meter when the pump is installed at the outlet of the water meter differs from the non-pumped mode in different flow rates. This difference is due to the change in the flow profile and the angle of impact of the water with the impeller. The results indicate that in high flow rates (more than 536 L/h) with the other same conditions, rotational speed of the impeller is less than the non-pumped state with the maximum decrease of 17% and thus the meter has a negative error measurement. However, in low flow rates (less than 75 L/h) the rotational speed of the impeller is increased almost twice more than the non-pumped state causing enlargement in meter's orders of error measurement.

Mixing time can be used as a comparative measurement of mixers efficiency. The present study is an investigation of the effect of important operating variables (impeller rotational speed and air bubbles present) on the mixing time in an agitated tand by dual Rushton turbine. This study has shown that the mixing time decreases with an increase in impeller speed and the effect of gas flow rate on the mixing time depends on the impeller rotational speeds. The mixing time obtained by conductivity method has been compared with the PLIF technique by Moghaddas. According to the experimental results, the mixing times which were obtained from the conductivity technique have a good agreement with the PLIF technique. Therefore, the conductivity technique is a simple, accurate and cost effective technique to replace expensive way. Also, the mixing time obtained by using the correlation and formula at large scale of mixing systems was incorrect, and the number of available correlation in this scale of mixing systems is limited. In the present study,to predict of mixing time in a dual Rushton impeller stirred, a six-concentration obtained experimentally and that calculated from compartment model was obtained.

Using inducers in order avoiding pressure reduction at the centrifugal pump impeller inlet and consequently increasing pump performance at high suction speeds are important in many applications. The inducer which is an axial pump with lower number blades than impeller’s (usually 3 or 4), located on the upstream impeller and rotates with the same rotational speed and direction as the pump. In this research, changing inducer design parameters such as the blade pitch and the length to the diameter ratio on its and pump hydraulic performance is investigated, numerically. The results show that using inducer and changing its blade pitch ratio from 0.24 to 0.48, causes average pressure ratio increasing from %10 up to %34 at the pump impeller inlet. Unlike the pitch ratio changing effects, increasing the length to blade diameter ratio from 7/12 to 16/12 show a fairly constant average pressure ratio increasing up to %23. For the large pitch ratio, pump impeller induced head; decreases for low flow rate. Meanwhile, decreasing pitch ratio in high flow rate causes flow counter rotation at the pump impeller inlet that increases the pump impeller head.

Mixing time, flow pattern, and power number of a vessel depend on design and type of its impeller. That is, impeller effectiveness has often been evaluated via mixing time. In order to investigate the effect of impeller type on the mixing time, some experiments have been done for different types of impellers in a stirred vessel with a diameter of 175 mm. The mixing time measurements are carried out by means of electrical conductivity variations technique in five different rotational speeds (in the range of 4002000- rpm) for the following agitators: a two-bladed propeller, a three-bladed propeller, a four-bladed turbine, and a six-bladed turbine. Water is used as the main fluid; besides, 7cc NaCl solution with 200000 ppm concentration is injected as the tracer in a specific position. The mixing time is defined as the period between release of tracer and the time when the concentration of the tracer reaches 95% of the final concentration in the tank. By changing the type of impellers, the mixing time of different impellers have been evaluated. Indeed, the impeller giving the shortest mixing time is introduced as the best mixing impeller for the governed experimental conditions. It has been shown that increasing the rotational speed leads to a considerable decrease in mixing time and an increase in turbulency. Finally, by installing some baffles in the tank diminishing of vortexes is observed; consequently, mixing time decreases.

In the present research, the effect of altering the rotational speed of the Rushton impeller inside the bioreactor was simulated and investigated for proper air distribution and changes in the shear stress rate. The simulation was performed using the multiphase approach of the zero-equation scattered phase model, via the K-Epsilon Standard perturbation model, in stable three-dimensional manner using ANSYS Products 2019 R3 and Ansys CFX software packages. The governing equations of the system were solved by the finite volume method for the entire system. To properly inject air into the bioreactor, a sparger ring was used under the impeller. The results revealed that increasing the impeller rotation speed could help better disperse the air inside the bioreactor. However, it also increases the shear stress rate inside the bioreactor. It was also shown that increasing the speed and getting more energy from it creates turbulence in the liquid. Additionally, its effect on the gas phase is reduced for the rotation speeds more than 150 rpm. Considering the rotation speed of the impeller and its effect on the mixing of gas-liquid phase, the intra-liquid stress and the average mass transfer rate, the speed of 350 to 450 rpm may be considered as the optimal speed. Finally, it was found that by increasing the rotation speed of the impeller, better mixing in the bioreactor could not be achieved and the optimal speed had to be determined.

The aim of this study is designing the impeller of a centrifugal compressor in order to supply pressure ratio for a 65 kW micro gas turbine. First, the primary thermodynamic analysis has been conducted for the considered cycle using a home made code. Herein, the compressor pressure ratio was considered to be 4. The obtained thermal efficiency was 25.64%. Then, the design of micro compressor in 90,000 rpm rotational speed was conducted and its dimensions were extracted. The designed micro compressor has 9 main blades and 9 splitter blades. The outer diameter of the compressor impeller was 95.5 mm. Then, the three-dimensional geometry of the compressor impeller was extracted. Finally, to validate the designed impeller, CCD software was used and CFD analysis has been conducted on generated geometry, using CFX.

The effect of Gurney flap height and mounting position on the head coefficient of a centrifugal fan at different Reynolds numbers is investigated experimentally. Quarter round Gurney flap of 1.0, 1.5, 2.0 and 2.5 mm height is mounted at three different positions, S=1.00 (impeller tip), S=0.95 and S=0.90 on the pressure surface of the impeller blade tip. Performance tests are carried out on the centrifugal fan at five Reynolds numbers corresponding to five rotational speeds of 1100, 1500, 2000, 2500 and 2900 rpm respectively. From the performance curves it is found that the fan head coefficient increases significantly with Gurney flaps at low Reynolds numbers and increases marginally at high Reynolds numbers. Effect of Reynolds number on the head coefficient is considerable for the baseline fan and found to be negligible for the fan with Gurney flaps, for all combinations of Gurney flap mounting position and height. The head coefficient of the fan improves as Gurney flap height increases but the improvement is marginal after certain height of Gurney flap. The head coefficient of the fan deteriorates when Gurney flap is mounted away from the impeller blade tip.

In this article, the effects of volute cross section shape and centroid profile of a radial flow compressor volute were investigated. The performance characteristics of a turbocharger compressor were obtained experimentally by measuring rotor speed and flow parameters at the inlet and outlet of the compressor. The three-dimensional flow field model of the compressor was obtained numerically solving Navier-Stokes equations with SST turbulence model. The compressor characteristic curves were plotted. For model verification, the results were compared with experimental data, showing good agreement.Modification of a volute was performed by introducing a shape factor for volute cross section geometry. By varying this parameter, new external volutes were generated and modeled while the original volute was intermediate volute. The effect of volute cross section shape on compressor pressure ratio and isentropic efficiency at design rotational speed were investigated.Also pressure non-uniformity around compressor impeller was investigated using pressure taps around the impeller outlet to verify numerical results. This effect was considered and reported for new cases using numerical results.The results show how the shape and centroid profile of volute circumferential cross sections can influence the compressor characteristics and circumferential static pressure non-uniformity.

The present study aims to describe characteristics of cavitation during the startup process of a condensate pump. The pump is featured by an impeller equipped with five splitter blades. A computational fluid dynamics (CFD) work was conducted to plumb the evolution of cavitation in the pump. Effect of the volumetric flow rate on instantaneous cavitation patterns as the rotational speed of the pump increased was analyzed. The results show that high resistance to cavitation of the pump depends greatly on large area of the impeller eye, which is related to the deployment of the splitter blades. The splitter blades are insignificantly affected by cavitation. During the startup process, both the pump head and the pump efficiency vary drastically, which is insensitive to the flow rate. At a net positive suction head (NPSH) of 2.0 m, high flow rates are responsible for intensified cavitation. High volume fraction of cavitation arises near the inlet of long blades. As the rotational speed increases, the evolution of cavitation is featured by intermittency and diversified cavity patterns. Furthermore, the sum of the volume fraction of cavitation fluctuates with continuously increasing rotational speed.

The high-speed centrifugal pump plays a crucial role in fields such as aerospace and petrochemical industries, owing to its characteristics of elevated rotational speed and high head. During high-speed operation, the centrifugal pump is prone to cavitation, which alters the fluid flow state within the pump, leading to vibrations, noise, and a sudden decrease in pump head and efficiency. Simultaneously, the collapse of cavitation bubbles generates impact pressure that can damage the pump's internal flow components, significantly reducing its operational lifespan and causing severe consequences. Moreover, under constant-flow conditions, the absolute and relative velocities of the fluid at the impeller inlet are functions of the suction pipe diameter. Therefore, there exists an optimal value for the impeller inlet diameter to enhance the centrifugal pump's resistance to cavitation. Similarly, the different geometric and structural parameters of the inducer also influence the hydraulic performance of the centrifugal pump. The focus of this study is on the external characteristics and internal flow patterns of an optimized high-speed centrifugal pump. In this paper, the entire flow field of the model pump is numerically simulated using ANSYS CFX software. The performance and overall flow field state of the high-speed centrifugal pump under different impeller configurations and inlet diameters are explored. The influence of blade wrap angle and inlet diameter on the high-speed centrifugal pump is revealed, providing a theoretical basis for subsequent optimal design.