In order to simultaneously control the spray field and volume of sprinklers in accordance with various shapes of irrigation area, a variable regulator design for precision irrigation sprinklers is proposed. The variable regulator was constructed with upper and lower waterblocking pieces, each of which comprises a central throughhole as well as fanshaped throughholes and fanshaped waterblocking pieces. As the sprinkler rotates, the upper and lower waterblocking pieces rotate in opposite directions. In conducting, both the watercarrying area and spray range increase; when it is closed, both the watercarrying area and spray range decrease. In this study, the structural parameters, including the central angle of the fanshaped and central throughholes for minimizing the sprinkler energy loss, were designed; based on the local resistance theory of water movement, the central throughhole diameters for the upper and lower waterblocking pieces were also designed. The results show that the variable regulator designed in this study can guarantee the minimal resistance loss at watercarrying cross section; through spray range and watercarrying area testing, it is found that the contours of sprayed areas has transformed from circles to approximately squares, with the largest range approaching closely the original nozzle range and the water distribution being even, which can meet the demand of controlling spray flow and spray range as they vary and realize variablerate precision irrigation.

In order to study the characteristics of internal flow in a pumpturbine operating in the Sshape region, the flow in the model pumpturbine in a pumped storage power station in China was simulated by using CFD codeCFX. The detached eddy simulation model (DES) that is more precise than the traditional RANS model was applied in the simulation, consequently, the internal flow pattern and performance parameters of the pumpturbine were obtained; and compared with the experimental data and the theoretical analysis results, respectively. It was shown that the results of DES model are quite good, causing the error between the estimated and experimental performance is less than 3%; further, the internal flow in the runner are in good agreement with theoretical analysis as well. As the flow rate decreases, the flow separation phenomenon near the runner inlet was strengthened gradually, and eventually a vortex was developed in the flow passages, causing a blockage to flow. Note that the vortex can induce rotorstator interactions among the runner and double circular cascade, which will results in instability of flow in the whole passage.

The existing methods for calculating critical depths of open channels were summarized and their characters have been clarified.  In order to identify simple, universal, accurate explicit equations for calculating the critical depth in open channels with typical crosssections, two dimensionless variables related to channel crosssection geometry and discharge were defined. Then, those explicit equations available for five sorts of open channels with typical crosssections in literature were expressed by the dimensionless variables, thus the most appropriate ones could be selected by comparing their complexity, accuracy and application range. Also, by applying the best approximations algorithm, a new explicit equation expressed as a series of piecewise power functions was developed for the openchannel with standard citygate crosssection. For the new equations, the results of error analyses indicate that all the maximum relative errors in critical depth are less than 1% in the channel normal application range. The results of the study may provide a reference for the design and hydraulic calculations of typical open channels applied in drainage and irrigation.

Water normal depth calculation is an important task in the design of an open channel for drainage and irrigation. First, dimensionless variables including channel roughness coefficient, bed slope, geometric parameters, and discharge were introduced for each common section. In order to obtain general equations and evaluate their accuracy, the explicit equations available for water normal depth were expressed by those dimensionless variables. Then, the real ranges of those variables were specified for each common section in applications, the relative errors in the explicit equations that involve the variables were analyzed in the ranges. Also, the global relative error distribution diagrams were plotted to compare the maximum relative error and the global one. According to these analyses, the most appropriate equations, which can explicitly calculate the water normal depth in the channels with five types of common section, were spotted. Finally, based on the best approximations algorithm a new piecewise explicit equation was proposed for the water normal depth in a standard castlegate section. It was shown that the maximum relative errors in all the recommended equations are less than 1％ for the water normal depth in six types of common section. The results in the paper have provided an effective method for designing channels with six types of common section and carrying out hydraulic calculations.

Gas viscosity is an important parameter for the performance of gas lubrication mechanism such as dry gas seal. The gas viscosity is related to temperature and pressure under the condition of high pressure, but there are few researches about the detailed relations between viscosity, temperature and pressure. Nitrogen(N₂)is taken as the study object, and the viscosity-temperature fitting expression and the viscosity-pressure fitting expression, the viscosity-temperature-pressure fitting expression have been obtained based on the AP1700 material physical platform using the least square method by a mathematic software. The calculated results by the fitting expressions have enough accuracy compared with the viscosity values offered by the National Institute of Standards and Technology(NIST)Chemistry WebBooks, China national standard Heat Exchangers(GB/T 151-2014), calculated values in Booser′s publication Tribology Data Handbook respectively and calculated values by the Lucas equation. The results show that the fitting expressions can be used to express the changing laws of gas viscosity with temperature and pressure and to calculate the viscosity concerning the temperature and/or the pressure.

The unsteady blood flow field in a new type of ventricular assist device, namely the Bi-ventricular Assist Device(BVAD)under the design condition is calculated based on a CFD method. The blood velocity, turbulent kinetic energy and shear stress, mass flow rate in the pump inlets, axial and radial thrusts acted on the different components are obtained; moreover the static pressure fluctua-tion in the volutes is also analyzed. The results show that there are no notable stagnant regions for thrombus formation in the device. The pressure and shear stress are distributed similarly and uniformly in the device, showing an excellent anti-hemolysis performance. Because of the symmetrical structure of the BVAD, the axial force has been basically balanced by itself. The radial force and torque on the impellers are relatively low, showing the device can endure a transient radial load well. The pressure fluctua-tions in the volutes vary periodically, exhibiting six peaks and six valleys in time domain. The dominated frequency at every monitoring point is the blade passing frequency of the device due to the rotor-stator interaction.

Numerical simulation of a new shrouded impeller vortex pump was carried out. The method of solving steady three-dimensional incompressible continuity equation and RANS equations were employed to calculate the hydraulic performance of the vortex pump. The axial bearing mechanism of the oil film toward the impeller was analyzed, and further discussion about the influence of the wedge shaped groove on both sides of the impeller on the bearing capacity of the oil film was made. It was found that the predicted hydraulic property was consistent with test data, which proves the calculating model reliable. In addition, the results show that the axial supporting of floating impeller is rely on the oil film formed on both side of the impeller. The different thickness of oil film results in different radial pressure drops. The thinner one results in the slow pressure drop while the thicker one results in the uniform pressure, which causes an unequal force on impeller and provides the holding power. More-over, the wedge shaped structure enhances the supporting effect. The study is useful for the design and analysis of vortex pumps.

Water-saving irrigation equipment plays an important role in improving agricultural water use efficiency, increase farmer income and construction of ecological environment, also it has an important strategic position to ease the shortage in water resources, ensure the national food security, and promote the sustainable development of rural economy. The development of water-saving irrigation equipment has taken nearly for 60 years, a considerable progress has been made in its theoretical study and technical level and so on; further the scale of production can basically meet the development of water-saving irrigation in China, but the ability in technological innovation, research and development is weaker, the improvements in product quality, technical performance and reliability are on demand. The developing trends in water-saving irrigation equipment should include strengthening basic theoretical study, enhancing the capability of independent innovation, designing and manufacturing intelligent, precise, cheap and green water-saving irrigation equipment with multi-function, low energy consumption and cost. It is suggested that the comprehensive technology and equipment for water-saving irrigation in hilly land should be investigated. The multi-function, intelligent and precise sprinkler irrigation systems should be developed. Also, the irrigation technology and equipment with low cost, high efficiency and collaborative precision in water and pesticide spraying as well as fertilizing should be innovated. The water-saving irrigation technology and equipment by using clean energy should be exploited. These suggestions may promote the water-saving irrigation equipment industry to develop in a comprehensive and healthy manner in China.

The study on theoretically estimating variable axial clearance in a medium or high pressure external gear pump is rare yet, thus a dynamics model for determining such a clearance was established in the paper based on an analysis on forced acted on a floating axial sleeve (side plate), which consisted of the pressure in squeezed film, the outside compensated forces on the sleeve, the pressure in trapped oil and the working oil pressure. Then variable axial clearances were iteratively estimated from the model in a meshing cycle by using the Runge-Kutta method. Subsequently, an analysis on the influence of compression ratio, different distributions of working oil pressure and trapped oil pressure on the clearance value was conducted. The results show that the axial clearance is about 0.13 mm in all the cases, and it is consistent with the actual value. The greater the total force of oil pressure due to the different distributions of operating oil pressure at the same compression ratio, the smaller the axial clearance. As the other conditions remain unchanged, the higher the compression ratio, the smaller the axial clearance. Moreover the operating oil pressure and compression ratio have a significant impact on the clearance, but the trapped oil pressure just has slight effect on it. Generally, in a medium or high pressure external gear pump the axial clearance really shows less variable, so that the mean value of the variable clearances can be applied in design to simplify subsequent calculations.

The standard k-ε turbulence model, homogeneous multiphase model and Rayleigh-Plesset equation were applied to simulate cavitation characteristics in a centrifugal pump with specific speed of 94 under different conditions based on ANSYS CFX software. According to the simulation results, the energy characteristics under the no-cavitation conditions and cavitation characteristics of the model pump were predicted, and the vapor volume distribution on the middle stream surface of impellerand the blade loading characteristics on the middle stream line under different cavitation conditionswere analyzed. The comparison between prediction values and experimental values indicates that the prediction results are accurate to some extent, and the absolute errors of net positive suction head under different conditions are 0.25, 0.29 and 0.06 m, respectively. The flow field analysis indicates that the vapors generated at suction side of blade near the leading edge at firstand then extended to the outlet of impeller with the reduction of inlet total pressure. Compared with other blades, the loading on the blade that against the volutetongue is the least and the loading on the other blades at the relative position of 0.35-0.80increased obviously with the deterioration of cavitation condition,which shows that the blade loading is significantly affected by cavitation.

As the main body of facility agriculture, the greenhouse play an important role in adding the China vegetable supply, increasing farmer income, promoting agricultural industry, improving the living standard and so on, which has a broad market space and development prospects. At present, the greenhouse industry has made rapid development in theoretical research, control technology, equipment and industrial scale, formed the greenhouse industry and technical system with Chinese characteristics initially. But the scientific content and technological level remain to be further improved in equipment matching capability, environmental regulation and energy saving, mechanization and automation, crop cultivation and management. Increasing the research and application on new technology, new material and new product, strengthening the research on basic theory and standard system, and improving the systematicness, reliability, and advancement of greenhouse equipment, can direct greenhouse industry to high efficiency, low energy consumption, environmental protection, multi function, intelligentization, standardization, regional development, etc.

In order to research influence of inlet shape on centrifugal pump vibration and noise, ensuring the pump and impeller′s other geometric parameters constant, only changing the form of the centrifugal pump inlet, the vibration induced by inlet was studied from two aspects, test and numerical simulatione velocity and the unsteady state pressure characteristics of the two forms of centrifugal pump before and after improvement were obtained, analyzed comparatively and verified experimentally, measuring the vibration signals of model pump feet under different forms of inlet, and processing the vibration signal data to verify the simulation conclusion and the vibration generated by modifying centrifugal pump inlet. The results showed that: the changed centrifugal pump inlet has a certain improvement effect on pressure and velocity distribution within the inlet and impeller, straight centrifugal pump had smaller influence than the pre-impact spin one on flow field, all the observation points′ pressure fluctuations of impeller and volute were reduced and the seat vibration response was reduced by 5 dB under experimental verification.

The threedimensional turbulent flow in an engine cooling water pump with the impeller, which has ever been severely damaged in operation, was simulated employing the timeaveraged N-S equations, the standard k-ε turbulence model and multiphase flow model by CFX software. The characteristics and cavitation performance were predicted and the reasons for the impeller damage were clarified by observing the flow variable distributions in the impeller of the pump. The numerical simulation results indicat that the critical NPSH of the pump is about 10.7 m at 85 ℃, and a serious cavitation occurs under zero gauge pressure, it is suggested that cavitation causes the impeller damage. The experimental head of the pump is 6.1 m at the design flow rate of 285 L/min, it is well below the numerical simulation head under room temperature, thus a serious cavitation has occurred in the real operating conditions; such a conclusion based on the predicted results is basically consistent with the experimental observations.The numerical results provide a theoretical basis for improving the cavitation performance or preventing from or mitigating cavitation in an engine cooling water pump.It offers a fast and precise computational method for simulating and identifying cavitation damage in engine cooling water pumps as well.

The present state of research on flow induced vibration and noise of centrifugal pumps was introduced. Based on the virtual instrument data acquisition system and a routine pump test system, a closedloop test rig was established for measurement of flow induced vibration and noise in centrifugal pumps. A synchronous acquisition was realized for pump performance parameters and flow induced vibration and noise signals.  A singlestage, endsuction centrifugal pump with 5 blades, whose specific speed was 93, was chosen as the experimental model. The additional impellers respectively with 4, 6 and 7 were made and tested in the same volute. The performance of pumps with those four impellers were measured in the whole flow rate, the vibration and noise signals were recorded and processed as well. The experimental results show that the highest vibration intensity is observed in the pump with 5 blades. With increasing flow rate, the vibration intensity level keeps constant initially and then significantly rises. The frequency of noise issued from the pumps mainly was in the range of 0-2 000 Hz. With increasing number of blades, the peak shaft frequency augments gradually at small flow rates. Those outcomes will be instructive and helpful for establishing a hydraulic design method to ensure centrifugal pumps with a low level of flow induced vibration and noise. 

Ocean is a huge treasure rich in biotic and minerals resources as well as energy. Exploitation of marine resources is a new national strategic objective, and the pace of deep-sea mining needs to be accelerated. Due to poor working conditions, the requirements for mining equipment are so high that the research of mining system, especially for the lifting pump system is very important. The classification and global distribution of subsea mineral resources were described. The situation of deep-sea mining in China in detail was summarized. The lifting technology is an important part of deep-sea mining system, and the pipe lifting method is considered to be one of the most promising lifting me-thods, which includes hydraulic lifting, air lifting, light medium and heavy media lifting, et al. Slurry pump lifting and air lift pump lifting technology have been carried out in deep sea trials, proving that they have the best development prospects. Finally, the development of hydraulic lifting technology, highlighting the development prospect of slurry pump and its commercial applications were elaborated, when the trend of deep-sea mining was discussed.

 The laser surface texturing on the SiC mechanical seal samples were studied by using a Qswitched diodepumped Nd:YAG laser and the laser processing technique called “single pulse at a time, repeated at intervals”， and the geometric parameters of texture were measured by means of WykoNT1100 surface profiler, further the effect of laser processing parameters (pumping current, repetition frequency, number of excitations, scanning speed) on the geometrical parameters and quality of microtextures was analyzed. The results show that pumping current and number of excitations have an evident influence on the micropore processing quality, and repetition frequency is relatively small. However,pumping current, scanning speed and repetition frequency can greatly affect microgroove processing quality. High quality microtextures can be obtained via optimizing the laser processing parameters. For processing microdimple, the optimal laser parameters, such as pumping current and number of excitations are 14-16 A, 1-10, for processing microgroove. However, the optimal pumping current, repetition frequency and scanning speed are 14-16 A, 1 500-2 500 Hz and 8-25 mm/s, respectively.

To investigate into the pressure fluctuation feature caused from the rotorstator interaction between the impeller and the diffuser in a mixedflow pump, the unsteady flow field in the pump with different numbers of blades in the impeller and the diffuser were numerically simulated based on the standard k-ε turbulence   model, SIMPLEC algorithm and sliding mesh model. The pressure fluctuation data were acquired by monitoring fluid pressure at the points located at the impeller and diffuser. The influence of number of blades and blade thickness on the pressure fluctuation was discussed in timedomain. The results show that the number of impeller blades is the main factor causing pressure fluctuation in the whole flow field. The pressure fluctuation amplitudes in the inlet and outlet to the impeller is consistently increased when the number of impeller blades is reduced; while the pressure fluctuation at the impeller outlet and in the diffuser is less affected by the number of guide vanes. Those conclusions will provide a reference for hydraulic design of mixedflow pumps and their stable operations.

In order to improve the critical speed of multistage centrifugal pump rotor system effectively, the effects of several impact factors on the speed or natural frequency of the rotor are analyzed and compared by means of rotor dynamics and finite element method. Additionally, the vibration modal analysis is conducted based on a whole rotor system, and the corresponding bending and torsional vibration modal shapes are provided as well. A quantitative comparison of the fluid-structure interaction and spin softening effect on natural frequency or critical speed is made, the factors affecting the critical speed of rotor and the optimization methods for the speed are given, and the numerical analysis and experimental results are compared. It is shown that accurately simplifying support, reasonably determining support stiffness and damping matrix are necessary prerequisites for precise predictions of critical speed. The fluid-structure coupling effect is equivalent to add a virtual mass on the rotor. The spin softening effect works by the Coriolis effect. The "dry" and "wet" critical speeds of multistage centrifugal pump rotor are quite different. The calculated and measured critical speeds are in good agreement. The numerical simulation of ANSYS is in a good accuracy and can provide a certain reference for the rotor design of multistage centrifugal pump.

The main objective of the article is to investigate the difference in indoor thermal comfort and air quality by means of numerical simulation based on a wellvalidated CFD(computational fluid dynamics) model when a commercial kitchen is subject to mixing and displacement ventilation. It was shown that using thermal displacement ventilation in the kitchen can reduce indoor temperature without increasing the airconditioning system capacity. Under the same indoor environmental conditions, the flow velocity of mixing ventilation (MV) is almost twice that of displacement ventilation (DV) in average, and the crossdrafts exists which leads to an uneven flow pattern. The temperature stratification is evident for DV, the temperature gradually gets higher upwards, and it has an appropriate value in the human breathing zone. Also, the air quality in the human breathing zone of DV is better than that of MV system which operates in the same air velocity. Moreover, the average air age of the former is less than 100 s in the kitchen. A properly designed displacement ventilation can maintain a thermally comfortable environment where the air velocity is lower than 0.3 m/s, the difference in temperature is below 2 °C between the head and ankle level, and the percentage dissatisfied people in breathing zone is smaller than 15%, and eventually can provide a better IAQ(indoor air quality) in the occupied zone.

The principle of a new kind electromagnetic pump which has a magnetic circuit to produce reciprocating magnetically permeable piston motion is introduced.

To improve the performance of axial flow pumps and upgrade the design principle of the pump blades, a new approach for calculating the blade camber was proposed here. The principle and procedure that the approach designs the blades of axial flow impeller were presented based on the Joukowski transform. The geometrical properties of an eccentric circular cylinder, which was formed by the superposition of three twodimensional potential flows—a doublet, a uniform plane flow and a point vortex, fluid dynamics around it and the position of stagnation point on it were described. Further, the geometrical properties of a circle arc, which was derived from Joukowski transform, and the fluid dynamics around it were discussed as well. Based on the above achievements, the method and producer for determining the direction and shape of a blade camber were developed in terms of the specified circulation and freestream velocity. The method and producer proposed here are completely different from the traditional ones, such as the singularity method, streamline method and so on for axial flow pump blades. The new approach is easily handled by pump engineers and it is hopeful that the approach can offer a new way for designing axial flow pump blades for the engineers.

To investigate the transient characteristics and internal flow in the pipeline of pump system during regulating period of a valve, a onedimensional simulation model which contains the pipes, pump and valves etc has been established by software Flowmaster. CFD code Fluent 6.2 was used to solve the incompressible threedimensional transient turbulent N-S equations with the dynamic mesh method to deal with the moving boundary caused by the opening valve core. The simulation results show that the valves with linear and logarithmic regulating characteristic have a fast opening feature which means the flow rate is very sensitive to the valve opening degree, in addition the water hammer pressure falls down promptly when the relative opening degree is in the range of 10% to 20%. As the valve relative opening degree is reduced, the flow behind the valve becomes disorder, leading to great hydraulic losses and considerable drag coefficient. For instance, the drag coefficient of valve under transient period shows great difference from that under static condition when the relative opening degree is less than 0.5. These analyses show that the transient behavior and unsteady internal flow pattern cannot be handled by the existing usual analytical steady flow models during regulating period of a valve, especially at a relatively small opening degree. In that case, the steady flow models are subject to be amended in some degree to allow them to provide correct computational results.

To investigate inflow fields in Micro-channel at Reynolds number lower than 1,such as inflow in vascular plant,with micro-fluidic particle image velocimetry(Micro-PIV) technique and numerical simulation that simulating wall roughness elements by setting up porous medium thickness and momentum source of porous medium model in software Fluent,inflow fields in straight micro-channels with cross section of 400 μm×400 μm under the conditions of the Reynolds number of 0.15,0.25 and 0.35 were obtained respectively.The velocity distributions were compared with analytical solution adopted by solving governing equations directly.The result shows that effect from wall roughness on the velocity distributions is small but not ignorable in micro-channel,so the analytical solution cannot meet the experimental results.The profile has the same tendency,but the value is lower in the mean flow area,which is distant from horizontal axis less than 0.04 mm,and higher in other region near the wall.Velocity distributions derived by the numerical simulation meet the experimental results well,so this numerical simulation can be successfully used in handling inflow problems at low Reynolds number in square section straight micro-channel.

Based on the finite volume method and Realizable k-ε turbulence model, the flow field inside multinozzle jet pumps was investigated numerically. The calculation reliability was validated by experimental data. Based on the simulation results of streamwise and spanwise vorticity distribution and their peak value variation, the mixing mechanism of the two fluids was analyzed. The results show that the multinozzle could promote the mixing and improve pump efficiency. The vortex has great effects on the mixing. Relative to the streamwise vorticity, the spanwise vorticity value is large and the attenuation becomes flat. The streamwise vortex plays a major role in the mixing. The value and attenuation rate of streamwise vorticity determine the effect of the mixing in the throat. For a definite vorticity value, the greater the streamwise vorticity value is, the faster it decays. The smaller the spanwise vortex size, the faster the mixng, and the higher the pump efficiency. The vorticity distribution in the throat indicates a central nozzle may lead to greater losses. The optimum distribution is that all the nozzles are on a circle.

The basic soil physical parameters and water-air-thermal parameters measured at 13 sampling points in Shannxi province are analysed to master their provincial-scale spatial distribution characteristics by making use of GIS technology and statistical methods. The effects of soil texture and type and land use on the water-air-thermal parameters spatial distributions are assessed by means of variance and regression analyses. The inverse distance weighted(IDW)interpolation results show that sand content decreases while clay content increases from north to south in the province. Soil saturated hydraulic conductivity, soil air permeability and thermal permeability decrease with declining sand content. Soil texture and type as well as land use are the main controlling factors of water-air-thermal parameters spatial distribution. Explanatory power of soil type on water-air-thermal parameters spatial distribution is better than land use, but weaker than soil texture. It is advisable that soil texture, soil type and land use should be analysed in a combined manner in the provincial-scale spatial distribution prediction of water-air-thermal parameters to improve the accuracy of prediction.

In order to raise the efficiency and quality of Finite Element Analysis(FEA),the functions of overseas commercial FEA preprocessing software HyperMesh is carefully studied,and a bearing block are used to illustrate the steps of FEA’s preprocessing in HyperMesh,the matters needing attention and how to export the result file and so on.The research provides a new ideal method for FEA,and indicates that do the preprocessing of FEA in HyperMesh software first and then export the CAE data to ANSYS software for solution is practicable,and also provides some help to CAE engineers.

In order to research the important influence factors of the coefficient of the flow rate pulsation φ on the external gear pump, the analytic way of deducing and simulation was adopted. By deducing the formulation of the coefficient of flow rate pulsation, the relationship between gear number, press angle and φ were analyzed. A numerical simulation of the transient flow field of the gear pump was performed by using the moving boundary condition and dynamic mesh method with k-ε turbulent model, and the relationships among the loading pressure,the clearance and the φ were achieved. The result shows that the coefficient of flow rate pulsation will decrease with the increasing of the gear number z or the pressure angle α. It is good for improving the flow rate characteristic of the gear pump. Furthermore, the gear number makes a very similar function in improving the flow characteristics with the pressure angle′s function. On the other hand, the coefficient of the flow rate pulsation will also decrease with the loading pressure p or the clearance δ increasing. The exaggerated loading pressure and clearance δ will lead to the volumetric efficiency decreasing, and this characteristics should be attached great importance in pump design procedure.

According to high water head, large head variation and 770 MW unit capacity, a study of hydraulic design of the giant Francis turbine units in the Xiluodu hydropower plant was carried out. From the view of hydraulic stability control, the hydraulic design condition was discussed. The selecting principle and matching relationship of four key hydraulic parameters including rated speed, unit discharge, unit speed, design head as well as two important geometric parameters covering guide vane relative height and diameter ratio of the runner inlet and outlet, were demonstrated. The possible stability problems induced by different hydraulic design parameters were analyzed by comparing different preliminary design schemes, and the viewpoint of selecting low hydraulic design parameters in developing giant Francis turbine was emphasized. The results show that increasing design head can improve the vortex flow characteristics in the runner channel at the high head part load operating region, and can make the incipient cavitation at the suction surface of the blade inlet side far away from the operation region of the hydraulic turbine. Finally, it has been proved that the hydraulic design adopted has practical engineering values by the model acceptance test.

The flow passages and rotor system of a coal mine submersible centrifugal pump were built by the 3D software Pro/E, and an unstructured mesh was generated in the passages with the software ICEM. The characteristics of such a multistage pump were estimated through the code CFX at different operating conditions based on the Reynolds timeaveraged Navier-Stokes (RANS) equations combined with the standard k-ε turbulence models and SIMPLEC scheme， and compared with experimental data, their reliability was confirmed. The simulated fluid flow results were input into Ansys Workbench to calculate the modes of the rotor system with two pivots by using fluidstructure interaction method, it was found that the first order critical speed of the rotor system was lower than the pump rotational speed. According to the deformation patterns of the rotor system the rotor system was redesigned with three pivots， the calculated critical speed of the new rotor system met the design requirement. Obviously, the life span of bearings will be extended. The results show that the quick damage of bearings 7217AC/DB and serve erosion of wearrings are mainly due to the too low critical speed of the original rotor system. The critical speed of the threepivot rotor system is higher than the pump rotational speed and it will greatly improve the reliability of both bearings and sealingrings.

 In order to obtain the simple and general explicit formula with high accuracy for computing the normal depth of semi-cubic parabolic channels,formula for direct computation of the normal depth was developed by obtaining initial function using iteration theory and optimization.Mathematical transformation on the basic equation for determining the normal depth of semi-cubic parabolic channel was made by introducing the concept of characteristic depth of cross-section,and the iterative formula with high convergence rate was derived.According to the optimization of the iterative formula in the range of 0.025 to 40 for dimensionless normal depth H,the reasonable initial function was developed.Direct calculation formula for computing the normal depth of semi-cubic parabolic channels was obtained by using the reasonable initial value and iterative formula.Error analysis of the formula was also carried out.The result indicates that the maximum relative error of the formula is less than 0.3% for the most frequently used range of characteristic depth of cross-section.The formula developed in this paper is simple and has high accuracy with wide range of applications,and it can provide simple method for computing the normal depth when the channel section is designed for irrigation and drainage and controlling the water level