Vortex-type's micro-hydro water turbine is a new technology for harvesting energy from water which the performance is still providing more challenge. After having designed the vortex-type water turbine in previous work, a laboratory-scale experimental apparatus is built to prove the design and to validate numerical simulations of the turbine The important design parameters such as torque, power, and efficiency are considered. It is found that the CFD results gives higher torque, power, and efficiency compared to experiments results with a similar trend. This is due to no feature in the used CFD software in evaluating mechanical friction that happened in experiments device, for more specific in torque-meter used. Head of CFD for discharge of 2.7 L/s and 2.8 L/s are 0.06 m and 0.06 m while from experiment is 0.07 m and 0.072 respectively. ANSYS has been used for CFD simulation.

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Flow conditions near the casing tongue have a significant impact on the performance and stable operation of the centrifugal pump, so the internal flow conditions have been measured by the experiment and PIV measurement. The internal flow conditions of mini centrifugal pumps especially smaller than 100mm are less measured by PIV measurement and its flow conditions near the casing tongue are not clarified yet. Therefore, PIV measurement was conducted near the casing tongue for the mini centrifugal pump having 55mm impeller diameter. The two-dimensional open impeller with the large blade outlet angle 2=60° was selected as the test impeller. FlowMaster Stereo-PIV by LaVision was used for the PIV measurement and the whole test section was made of the acrylic resin including the test impeller. Two CCD cameras with its resolution 2048×2048 pixels were used and velocity vector and contour were calculated by the PIV measurement software DaVis(Lavision). The internal flow conditions near the casing tongue were focused in this research. The PIV measurement results at different flow rates were shown and the tongue flow angle was defined to clarify the flow condition near the casing tongue with the impeller rotation. With the increase of the flow rate, the tongue flow angle increases which means the flow near the casing tongue is discharged to the casing throat. In the present paper, the internal flow near the casing tongue is clarified by PIV measurement results and the flow conditions with the impeller rotation are discussed.

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This study involved an experimental investigation of the distribution of pulp fiber concentration in the region behind a partition plate with a tapered trailing-edge inserted in a convergent channel. The channel was modeled at the laboratory scale for the dispersion and rectification components of the headbox passage in a papermaking machine. For the experiments, the inlet cross-sectional average flow velocity, Ua, of an actual pulp suspension was in the range of 0.03–3.3 m/s. The flow was visualized, and the fiber-concentration distribution was measured. Subsequently, the effects of the flow velocity on the time-averaged and fluctuating fiber-concentration distributions (Ca and C’, respectively) in the flow direction were examined through comparisons with those in the cases where the plate was installed in the parallel channel or had a simple rectangular edge. In the convergent channel with the tapered trailing-edge, the fiber-concentration defect behind the plate was reduced abruptly. Moreover, the uniformity of the fiber-concentration distribution at the convergence exit did not vary with the flow velocity, thereby having a low value. Overall, the fundamental observations obtained in this study can contribute to the optimization and improvement of the headbox channels of papermaking machines.

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This paper presented a formula for calculating the resistance coefficient of porous medium model of brush seals considering the effect of gas compressibility. Firstly, the 2-D tube bank model is used to calculate the axial resistance coefficient of brush seals. Secondly, the feasibility of the method is validated according to the existing experiment results. The validation results show that this formula is effective for brush seals. Lastly, the pressure distribution and leakage rate of the test brush seal are analyzed. With the presented porous medium model, the pressure drop through the bristle is computed, and the effect of groove of the back plate is addressed. The pressure drop is mainly concentrated on the downstream side of the bristle pack. The groove in the back plate can keep the pressure balance of the bristles back, causing the recovering of the pressure in the last row of bristles. The leakage rate of porous medium model is higher than the 2-d tube bank model, because the 2-D tube bank model only considers the leakage rate of the zone of the fence height. The rotation speed has a little effect on the reduction of the leakage rate.

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This paper presents the results of an investigation on the effects of wavy cylindrical tubes on the turbulent cross-flow in a staggered tube bundle arrangement with transverse and longitudinal pitch-to-diameter ratios of 3.8 and 2.1, respectively. Two models of staggered tube bundles equipped with wavy cylinders are tested; the Model-A having a wavelength ratio (/Dm= 2) corresponding to a wave steepness (a/ = 0.1) and the Model-B having (/Dm= 1) corresponding to (a/ = 0.2).Experimental measurements were performed using a subsonic wind tunnel to study and compare the flow characteristics of the new configuration of cylindrical tubes with that of a similar arrangement with smooth cylinders for Reynolds numbers ranging from 0.5104 to 2104 based on the mean tube diameter and the free stream velocity. Experimental results show that the circumferential minimum pressure coefficients for wavy tube bundles are greater than at the bundle with smooth cylinders. As a result, the lift forces of wavy tube bundles are suppressed and a significant drag reduction is observed up to 20% for both wavy models. This continuous reduction of the drag force becomes larger with the increase of Reynolds number.

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When the liquid rocket engine turbopump starts, the tank valve opens first before the pump is driven. Due to the tank and hydrostatic pressure, there is a passive flow phenomenon inside the pump called natural flow. The impeller is passively rotated by hydraulic impact, which impacts the stability of the turbopump during the initial startup period. In order to study the unsteady natural flow characteristics of the turbopump, the coupled CFD/6DOF solver is used for simulation and obtaining the variation of rotational speed, flow loss, and torque with time. The characteristics of the turbopump impeller's radial and axial force are analyzed. The internal flow field and pressure pulsation features were investigated. The results show that the rotational speed caused by natural flow increases exponentially with time. Furthermore, the natural flow loss and torque gradually decrease with the increased rotational speed and has distinct pulsation characteristics and periodicity. The backflow phenomenon in the flow channel becomes more complex. The suction chamber and the inducer have a buffering effect on the impact of the incoming flow, making the pressure distribution more uniform. Due to the matching angle and the rotor-stator interference, the pressure pulsation in the guide vanes has distinct sub-harmonic interference during the natural flow process.

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This study proposes a method to optimize the blade angle and chord length distributions of axial flow fan rotor blade, and applied it to the design of the actual industrial axial flow fan. The present design model of the axial flow fan rotor blade is to construct and stack the section profiles using single circular arc and airfoil thickness distribution with the camber and stagger angles as design variables along the blade span height from hub to tip, and the chord length distribution is designed in a parabolic fashion from hub to tip. The performance and efficiency of the fan rotor blades are predicted by applying a through-flow analysis method to the 3D fan blade geometry obtained from the design variables of the camber angle, stagger angle, and chord length of the blade sections. These fan design and through-flow analysis methods are used as the simulation engine for optimization problem. Through applying the optimization algorithm, an optimal axial flow fan rotor is obtained with maximum efficiency and computational fluid dynamics analysis is performed to verify the result of the present optimal design. From the computational fluid dynamics calculation results, it can be seen that the present optimal design model has an efficiency improvement of about 2% compared to the initial design, and maintains relatively high efficiency even under partial load conditions.

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Abstract The aim of the present study is two-fold. Firstly, it attempts to solve the asymptotic model of the 2D stationary potential flow of a supersonic viscous fluid over thin airfoils. In the case of a high Re number:Re=O(10⁵), and a free stream Mach number of M_∞=1.45, the asymptotic solution is built using the new successive complementary expansion method. The theoretical Mach number of the flow is estimated in the outer inviscid zone along the airfoil surface, and a correction term is added to account for the viscous boundary layer effect in order to get an accurate approximation throughout the whole domain. Secondly, for comparison purposes, numerical simulations of the NACA 43013 airfoil were run for the Mach number distribution in each area. On the one hand, when compared to numerical simulations, the asymptotic supersonic laminar viscous flow solution shows good agreement for the laminar boundary layer but begins to diverge slightly from x=0,3.At this point, the laminar-turbulent transition starts, then the turbulent boundary layer develops towards the trailing edge. On the other hand, the Mach number distribution for the outer inviscid region matches the simulation and illustrates the change in velocity upon interaction with both the detached shock wave and the expansion waves.

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The behaviors of surge frequencies in multi-stage axial-flow compressors are studied by use of several non-dimensional parameters on the basis of numerical-experimental results. One of the essential parameters proves to be a flowpath-average reduced surge frequency multiplied by the stalling pressure ratio and the tip-Mach number. Framework map in terms of such parameters against reduced resonance frequencies can provide a whole view of the surge frequency behaviors, including various characteristic zones of surge behaviors, i.e., convective surges, near-resonant surges, degenerated surges, and multi-stage effects. Particularly, for the convective surges, the surge frequency parameter comes to have a nearly constant value over a wide range of the reduced resonance frequencies, independently of number of stages, speeds, and pressure ratios, etc., of the compressors. The map is practically useful for the evaluation of deep-surge frequencies. At the same time, it could form a base for further investigations into the surge phenomena.

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