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This paper presents a numerical investigation on the dynamic analysis of steam and water system of the natural circulation boiler SHL35.2.5/AI with the software MATLAB/SIMULINK. Based on the four-order Astrom-Bell model, a model applicable the specific boiler was established, casting light on the changes in parameters of designed, cold start and varying load condition. And a curve of cold start is obtained, which can be taken as reference for practical operation. In addition, in the condition of varying load, our model captured the phenomenon of false water level, and according analysis is made. Our study introduces a feasible method of simulation on the dynamic analysis of steam and water system on other boilers as well.

The head curves of a 1.5:1 new axial blood pump model were measured using five working fluids at five rotational speeds. The working fluids were water, a 39 wt% aqueous glycerin solution (GS), and three aqueous xanthan gum solutions (XGSs) with different concentrations. The flow velocities and shear stresses in the mechanical clearance between the casing and rotor were investigated using a laser Doppler velocimeter and hot-film sensor. At every rotational speed, the experiment in which viscous GS was used in the pump model showed a head curve lower than that obtained using water, whereas the head obtained using viscoelastic XGS was higher than that generated using water. A maximum difference of 65.8% between the heads measured in the 0.06% XGS and GS experiments was detected. The higher head produced by the XGS may have originated from the drag-reduction effect of XGS viscoelasticity. The measurements showed that a reverse washout flow at a velocity of 0.05–0.11 m/s occurs in the clearance. This reverse washout flow is crucial to preventing flow stagnation and accompanying thrombus formation. The wall shear stress and the Taylor number of the rotating Couette-like flow in the clearance both indicated that it is a turbulent flow.

The mean and time-varying fluctuation property of local wall shear stress of horizontal air–water bubbly flows in a circular pipe of 35 mm I.D. is measured using a TSI-1268W hot film probe. Data are collected in both entrance and developed regions of the flows. The variation of wall shear stress with L/D is analyzed, and the entrance length is determined to be 52–65 D at present studies. It is found that the wall shear stress is not uniform around the pipe circumference due to the asymmetrical phase distribution in the flows. The mean shear stress tends to decrease circumferentially from the pipe bottom to top. An increase of air flow rate at a constant water flow rate would further lower the wall shear stress at the upper part of the pipe and at the same time raise the wall shear stress at lower part of the pipe in both entrance and developed regions. An increase of water flow rate at a constant air flow rate would result in an increase of wall shear stress at all circumferential positions. The statistical property of wall shear stress is also discussed.

A 2:1 scaled-up model of the Kyoto-NTN magnetically suspended impeller centrifugal blood pump developed by Kyoto University, Japan, is tested using aqueous Xanthan gum solution and water as working fluids, respectively. It is found that the pump head rise with the solution is lower than that with water at same flow rate when the pump operates at low rotor speeds; at high rotor speeds, however, the pump will generate a higher head for the solution than for water at the same flow rate, and a maximum difference of 7% is detected. Data comparison indicates that water does not accurately model the head vs. flow rate characteristics of the prototype pump, and aqueous Xanthan gum solution of 600 ppm produced results best simulating the performance of the prototype pump.

A newly designed magnetically suspended axial blood pump is presented, in which a 5 degrees-of-freedom rotor is suspended by using two conical active magnetic bearings, each with a four-pole stator. The preferred configuration could provide a rather large moment of inertia to increase the rotating stability of the suspended rotor in the pump. The hydrodynamic performance and internal flow fields in the pump are investigated by computational fluid dynamics. The pump head flow characteristics and the efficiency-Q curves at various rotating speeds are obtained, and the detailed flow fields in the pump are determined numerically. The distribution of shear stress, including Reynolds shear stress, is studied and discussed. Also, special attention is given to the small clearance between the rotor and the pump shell where the reversed secondary flow is formed and can flush out the clearance to avoid the flow stagnations. The secondary flow as well as the magnetic bearings can reduce thrombus in the pump. To check the biocompatibility of the pump further, the hemolysis indexes of the pump are estimated on the basis of the computed results.

Quasi 3-D measurements of the turbulence structure of air–water bubbly flow in a horizontal tube with 35 mm i.d. are undertaken with two TSI “X”-type hot-film probes. The turbulent fluctuations, uf,vf,wf, in axial, radial and circumferential directions, respectively, and Reynolds stresses − uv and − uw are obtained. It is found that in the lower portion of the tube, the profiles of turbulent fluctuation and Reynolds stress resemble those of single phase flow; whereas in the upper portion of the tube, where the bubble population is high, the turbulence, especially the circumferential fluctuation wf, is substantially enhanced, and the radial turbulence assumes highest value in the radial position −0.7 − uw and − uv in our measurements are in the same level except in the lower portion of the tube where − uw assumes a value close to zero as is the case in single phase flow and vertical air–water bubbly flow.

The numerical model is built for the primary air duct of the pulverizing system with medium speed mills, and the inner flow fields are simulated by employing the commercial code of FLUENT. The simulated results show that the lengths of the straight ducts before and behind the measuring element are too short to meet the requirement of the flow rate measurement of the primary air due to the compact design in many domestic power plants. The actual flow at the cross section where the measuring element is installed is irregular and disordered and the air velocity obtained by the single measuring element is not the area-weighted average value. The blowing of cool primary air also aggravates the disorder of the flow fields. It is concluded that the flow rate of the primary air can not be measured precisely. The numerical simulation method could be adopted to measure and calibrate the flow rate of the primary air, which can avoid the limitations of the existing method. This solution could improve the precision and reduce the cost of the measurement, which will be a good alternative for the domestic power plants.

Two-D liquid velocity field in a tube with a combination of a stenosis and a bifurcation was measured with refractive index matching technique using Laser Doppler Velocimeter (LDV). The flow ratio of main tube to bypass was 1:4. It is found that the axial velocity profile has two peaks in the XOY plane which is skewed to the main tube wall facing the flow from the bypass, and it manifests itself in the form of "M" in the XOZ plane. A two counter-rotating vortices in the main tube cross section downstream the conjunction region is also detected.