NUMERICAL PREDICTION OF DYNAMIC PERFORMANCE OF PELTON TURBINE

Different from the reaction turbines, the hydraulic performance of Pelton turbine is dynamic due to the unsteady flow in the rotating buckets in time and space. The dynamic energy efficiency of bucket ηEB and power efficiency of bucket ηPB within a short period can be predicted from the dynamic flow pattern of the free-surface sheet flow in the rotating bucket, whereas the dynamic discharge efficiency of bucket ηQB is defined as the resident discharge in the bucket at the respective moment. Under the operation of higher unit speed nDH than the optimum one, the power efficiency of bucket is deteriorated by the jet interference with the rear surface of bucket ?Prear at the first stage of the dynamic performance, as well as the loss power due to the spilt flow from the cutout of bucket at the later stage of performance. Based on the dynamic performance prediction presented, the future possibility of the quantitative investigation for the negative scale effect of Pelton turbines was discussed.     

STUDY ON JETS IMPACT IN AIR FOR ENERGY DISSIPATION

1.　 INTRODUCTIONChina is a country rich in hydropower resources.With the developmentof the Chineseeconomy,many large-scale hydroelectric stations with high dams are being built or will bebuilt in the country,especially in the southwest region of China.Mostof which are locatedin the areas with high mountains and narrow valleys. The characteristics of these projectsare high water head,heavy discharge and narrow valleys.If flood discharge and energydissipation is nottreated properly,seriou…     

AERATION EFFECT OF SUBMERGED JET ON HYDRAULIC CHARACTERISTICS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＪｅｔｆｌｏｗｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙａｐｐｌｉｅｄｆｏｒｅｎｅｒｇｙｄｉｓｓｉｐａｔｉｏｎ .Ｉｎｄｅｓｉｇｎ ,ｈｏｗｅｖｅｒ,ｂｅｃａｕｓｅｏｆｔｈｅｃｏｍ ｐｌｅｘｉｔｙｏｆｐｒｏｂｌｅｍａｎｄｔｈｅｄｉｆｆｉｃ     

A STUDY ON THE FLOW BEHAVIOR OF AN AXISYMMETRIC LAMINAR JET

It is of great practical and theoretical importance to study the properties and flowbehavior of laminar jet,because it tightly links the physical phenomena of nonlinerity such asflow stability and transition and so forth.However,many problems and differences exist in ba-sic concepts and in understanding of stable and transitional properties and flow patterns of ax-isymmetric laminar jet.Therefore,a further study on this subject is needed to evaluate the exist-ing understandings and to find out the mechanism governing the behavior of actual axisymmetriclaminar jet flow.In this thesis,the flow behavior of axisymmetric laminar jet issuing from nozzles of severaldiameters in the direction of gravity was studied experimentally using flow visualization tech-nique in the range of Reynolds number from tens to thousands.The unstable and transitionalprocesses in the laminar jet were observed.The influence on the jet flow of different geometrycontours of jet chamber boundary was investigated.Some new flow phenomena were discoveredwhich gave deeper understanding of flow patterns and their dependent factors in low Reynoldsnumber axisymmetric laminar jet.A theoretical model to describe the variation of the axisym-metric laminar jet length influenced by the weak density difference is proposed based on the ex-perimental observation,which will be helpful in recognizing the flow behavior of axisymmetriclaminar jet of low Reynolds numbers.     

RESEARCH ON MOTION CHARACTERISTICS OF GAS-SOLID JET FLOW

l.INThoDUCT1ONTheresearchontwo-phasejetflowisbecomingahotspotofjetflowresearchinrecentyears.Therapiddevelopmentofcomputertechnologyhasmadeitpossibletosimulatetwo-phasejetflow,whichisofessentialimPortanceinvariousengineeringapplications.Forin-stanceitisausualproceduretospoutparticlesintoreactororcombustorinengineering.Theeffectofflowonparticlesdeterminestheparticledistributionandthepresenceofparticleshaveeffectonjetflowinturn.Therefore,theinvestigationontheparticledistributionandtheflowchar…     

EFFECT OF SUSPENDED PARTICLE ON STABILITY OF INTERFACE OF MOVING TWO-PHASE JET

ＮＯＭＥＮＣＬＡＴＵＲＥαｓｐａｒｔｉｃｌｅｖｏｌｕｍｅｆｒａｃｔｉｏｎｕｇｉｎｓｔａｎｔａｎｅｏｕｓｇａｓｖｅｌｏｃｉｔｙｖｅｃｔｏｒｕｓｉｎｓｔａｎｔａｎｅｏｕｓｐａｒｔｉｃｌｅｖｅｌｏｃｉｔｙｖｅｃｔｏｒＵｍｅａｎａｘｉａｌｖｅｌｏｃｉｔｙｏｆ...     

SCALE EFFECT OF IMPINGING PRESSURE CAUSED BY SUBMERGED JET

The characteristics of the impinging pressure at the jet equipment where the maximum jet velocity can reach 50m/s were studied. By comparing the impinging pressure with the one measured at the low velocity conditions, two conclusions of the scale effect are drawn： firstly, the velocity attenuation degree is smaller than that of low velocity jet, and secondly, the relative impinging width is narrower than that of low-velocity jet. The reasons of the scale effect of the impinging pressure were elucidated through numerical simulation.     

NUMERICAL SIMULATION OF ICE CONTROL EFFECT OF SOLAR ENERGY ON TIBETAN CHANNELS

With the Tanghe Diversion Channel in Tibet as an example, the theoretical study on the ice control effect of the solar sacks was conducted based on the previous study. The numerical simulation method was adopted and a one-dimensional numerical model for ice crystal in diversion channels in high-altitude cold regions was developed in this article. The heat transfer through the air-water interface and the mass transfer between ice and water were considered in the model. The model was validated by the field observation data on the diversion channel of the Tanghe Hydropower Station. The results show that the ice control effect of the solar sacks is obvious in the channel with large mass flow rate in the high-altitude cold regions.     

THE HYDRODYNAMIC CHARACTERISTICS OF FREE VARIABLEPITCH VERTICAL AXIS TIDAL TURBINE

The hydrodynamic characteristics of free variable-pitch vertical axis tidal turbine are investigated by combining experime-ntal and numerical simulations.The variations of hydrodynamics are obtained based on testing the kinematics and the dynamics of the turbine under different flow and structural conditions.Through analyzing the movement of the turbine and the characteristics of the flow field by numerical simulations,it is shown how the turbine’s performance is improved.     

EXPERIMENTAL STUDY ON THE EFFECTS OF AIR ENTRAINMENT ON A PLANE JET DIFFUSION IN A PLUNGE POOL

l'mTRODUrmNThisworkwasmotivatedbythepotentialapplicationOftheerosionofplungepoolsdownstreamofdamscausedbysubmergedwaterjets.TheerosionorscourofplungepoolsoccursatthePointofajetimpact.Thescourprocesshasbeeninvestigatedformanyyears.Thescourdepthestimatedfromformulasdevelopedoveryears,however,indicatesawidevariation(MasonandArumugam,l985)-Mostoftheseformulasinvolveanexpressioninwhichscourdepthisafunctionofthedischargeperunitwidth,theheaddropandthechar-acteristicsizeofthebedmaterial.Arecentin…     

INVESTIGATION ON THE SPLASH LENGTH OF THE AERATED JET

Atomized flow forms as an aerated jet from high dams impacts against the downstream water surface at high speed. Of all the regions of atomized flow the splash region is in the center of storm rainfall, which might cause certain damage to the hydropower stations and thence more attention should be paid. In this paper the impact of the water drop at the outer edge of the aerated jet against the downstream water surface was analyzed, and the motion of the splash water drop was investigated. Furthermore, a new formula for the calculation of the splash length was suggested, which is in good agreement with the data of model tests and prototype observation.     

EFFECT OF SURFACTANT ON TWO-PHASE FLOW PATTERNS OF WATER-GAS IN CAPILLARY TUBES

Flow patterns of liquid-gas two-phase flow were experimentally investigated. The experiments were carried out in both vertical and horizontal capillary tubes having inner diameters of 1.60 mm. The working liquid was the mixture of water and Sodium Dodecyl Benzoyl Sulfate (SDBS). The working gas was Nitrogen. For the water/SDBS mixture-gas flow in the vertical capillary tube, flow-pattern transitions occurred at lower flow velocities than those for the water-gas flow in the same tube. For the water/SDBS mixture-gas flow in the horizontal capillary tube, surface tension had little effect on the bubbly-intermittent transition and had only slight effect on the plug-slug and slug-annular transitions. However, surface tension had significant effect on the wavy stratified flow regime. The wavy stratified flow regime of water/SDBS mixture-gas flow expanded compared with that of water-gas.     

EXPERIMENTAL INVESTIGATIONS ON DIFFUSION CHARACTERISTICS OF HIGH CONCENTRATION JET FLOW IN NEAR REGION

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒｅｓｅａｒｃｈｏｆｊｅｔｉｓａｎｉｍｐｏｒｔａｎｔｆｉｅｌｄｉｎｆｌｕｉｄｍｅｃｈａｎｉｃｓ.Ｉｔａｌｓｏｈａｓｍａｎｙａｐｐｌｉｃａｔｉｏｎｓｉｎｅｎｇｉｎｅｅｒｉｎｇ ,ｆｏｒｅｘａｍｐｌｅ ,ｔｈｅｄｉｓｃｈａｒｇｅｏｆｐｏｌｌｕｔａｎｔａｎｄｃｏｏｌｉｎｇｗａｔｅｒｉｎｉｎｄｕｓｔｒｉｅｓ .Ｗｈｅｎｔｈｅｉｎｉｔｉａｌｄｅｎｓｉｔｙｏｆｔｈｅｊｅｔｉｓｄｉｆｆｅｒｅｎｔｆｒｏｍｔｈａｔｏｆｔｈｅａｍｂｉｅｎｔｗａｔｅｒｂｏｄｙ ,ｔｈｅｊｅｔｗｉｌｌｂｅａｆ…     

NUMERICAL CALCULATION OF SOLID-LIQUID T WO PHASE FLOW BETWEEN STAY VANES IN HYDRAULIC TURBINE

1.　INTRODUCTIONMany phenomena of silt-laden water flow can be seen in most rivers of China.Theabrasion of silt-laden water flow to hydraulic turbine has become the most concern forhydraulic power station or pump station.It is always of interest to many engineers andresearchers because of its seriously destroying to the blade ofhydraulic turbine.And mostoftheir works are mainly the performance effect caused by silt-laden water flow,namely thestudy ofouter characteristic.Surface coatisful…     

OSCILLATION AMPLITUDE OF THE FREE END OF A FLEXIBLY MOUNTED RIGID CYLINDER IN TRIANGLE ARRANGEMENT

In this paper,the oscillation amplitude of the free end of a group of threecylinders are studied.The three cylinders are erected at the vertices of an equilateral trian-gle,and three arrangements are made in this study.One of the three cylinders is served asa working cylinder which is mounted by a flexible cantilever and two accelerometers areattached on the free end in two directions.The results of the three-cylinder arrangementare compared with those of two cylinders in tandem/side-by-side arrangement in the samecondition.The experimental results show that the rear cylinder of a group of three cylin-ders is affected more seriously than that of the corresponding two cylinders in the contrastarrangement.The main direction of oscillation is changed.The transversal oscillation isstronger than the longitudinal oscillation in the three-cylinder arrangement.On the con-trary,the transversal oscillation is much weaker than the longitudinal oscillation in two-cylinder arrangement.The largest transversal oscillat     

PDA MEASUREMENTS OF TWO-PHASE FLOW STRUCTURE AND PARTICLE DISPERSION FOR A PARTICLE-LADEN JET IN CROSSFLOW

The two-phase flow structure and particle dispersion for a dilute particle-laden jet in crossflow(JICF) were experimentally investigated by means of Phase Doppler Anemometry(PDA) measurement.The two-phase flow experiments were conducted for different flow conditions and solid particle parameters,including the ratio of the jet velocity to crossflow velocity,the particle size and mass loading.The experimental results indicate that the fine particles with the size of 70 micron and the mass loading of 0.05% hav...     

NUMERICAL EXPERIMENTS ABOUT GROWTH OF THE ENERGY OF DISTURBANCE IN A BAROCLINIC FLOW

This article is concerned with the growth of energy of disturbances in a baroclinic flow within a finite time period. The implicit difference scheme was applied to the linearized vorticity equation, and the disturbance energy was computed for three kinds of vertical shears. It turns out that all the disturbance energy rapidly increases initially, and during the succeeding period there are several stages of growth and decay of energy of disturbances, and from a certain time on, all the disturbance energy begins to decrease.     

EFFECT OF NON-SPHERICAL PARTICLES ON THE FLUID TURBULENCE IN A PARTICULATE PIPE FLOW

In the non-spherical particulate turbulent flows,a set of new fluid fluctuating velocity equations with the nonspherical particle source term were derived, then a new method,which treats the slowly varying functions and rapidly varying functions separately, was proposed to solve the equations, and finally the turbulent intensity and the Reynolds stress of the fluid were obtained by calculating the fluctuating velocity statistically. The equations and method were used to a particulate turbulent pipe flow. The results show that the turbulent intensity and the Reynolds stress are decreased almost inverse proportionally to the fluctuating velocity ratio of particle to fluid. Nonspherical particles have a greater suppressing effect on the turbulence than the spherical particles. The particles with short relaxation time reduce the turbulence intensity of fluid, while the particles with long relaxation time increase the turbulence intensity of fluid. For fixed particle and fluid, the small particles suppress the turbulence and the large particles increase the turbulence.     

AN EXPERIMENTAL STUDY ON THREE DIMENSIONAL STRUCTURE OF BAROCLINIC WAVY JET STREAM IN A ROTATING ANNULUS SUBJECT TO RADIAL TEMPERATURE GRADIENT

1.　INTRODUCTIONThe research on jet,which is a typical flow pattern in atmosphere,has made a greatprogress in both theory and observation.There existsa striking similar feature between thejetstream of baroclinic fluid in a rotating annulussystem and the defined one of IMO( Inter-national Meteorological Organization,Upper Air Technical Commission) .Forsuch a similarfeature,more and more attention hasfocused on the experimental simulation of jetstream ina baroclinic fluid system based on…