Influence of the Axial Position of the Guide Vane on the Fluctuations of Pressure in a Nuclear Pump

The influence of the axial mount position of the guide vane on the pressure fluctuation in a nuclear pump(AP1000)is investigated.The characteristics of the three-dimensional flow inside the nuclear pump are analyzed by means of numerical simulation.Results indicate that when the axial relative distance between the guide vane and the pumping chamber is reduced,in conditions of“small flow,”the efficiency of the pump increases,the pressure inside the pumping chamber decreases,while the losses related to the guide vane grow.Under large flow conditions,as the efficiency of the pump decreases,the losses for the guide vane and the pumping chamber increase.The pressure fluctuation in the annular pumping chamber is basically determined by the rotation frequency and the blade passing frequency.The magnitude of these fluctuations is affected by the guide vane axial position.In particular,the smallest possible amplitude is obtained when the outlet central plane of the guide vane coincides with the outlet axis of the pumping chamber.

The effect of anode axial position on the performance of a miniaturized cylindrical Hall thruster with a cusp-type magnetic field

A 200 W cylindrical Hall thruster with a cusp-type magnetic field was proposed, manifesting convergent plume and high specific impulse. In this paper, a series of ring-shaped anodes are designed and the influence of anode axial position on the performance of CHT with a cusp-type magnetic field is studied. The experimental results indicate that the thruster keeps stable operation at the condition of 140–270 W discharge power. When the anode moves axially towards the upstream cusp field, the thrust enhances from 6.5 mN to 7.6 mN and specific impulse enhances from 1658 s to 1939 s significantly. These improvements of thruster performance should be attributed to the enhancement of current utilization, propellant utilization and acceleration efficiency. According to the analyses on the discharge characteristics, it is revealed that as the anode moves upstream, the electron transport path could be extended, the magnetic field in this extended path could impede electron cross-field transport and facilitate the ionization intensity, yielding to the enhancement of current utilization and propellant utilization efficiency.Moreover, along with this enhancement of upstream ionization at the given anode flow rate, the main ionization region is thought to move upstream and then separate more apparently from the acceleration region, which has been demonstrated by the narrowing of ion energy distribution function shape. This change in acceleration region could decrease the ion energy loss and enhance acceleration efficiency. This work is beneficial for optimizing the electrode structure of thruster and recognize the ionization and acceleration process under the cusp magnetic field.

Novel approach for determining the optimal axial preload of a simulating rotary table spindle system

This paper presents a new theoretical model to determine the optimal axial preload of a spindle system, for challenging the traditional method which relies heavily on experience of engineers. The axial preloading stiffness was treated as the sum of the spindle modal stiffness and the framework elastic stiffness, based on a novel concept that magnitude of preloads can be controlled by measuring the resonant frequency of a spindle system. By employing an example of a certain type of aircraft simulating rotary table, the modal stiffness was measured on the Agilent 35670A Dynamic Signal Analyzer by experimental modal analysis. The equivalent elastic stiffness was simulated by both finite element analysis in ANSYS? and a curve fitting in MATLAB?. Results showed that the static preloading stiffness of the spindle was 7.2125×107 N/m, and that the optimal preloading force was 120.0848 N. Practical application proved the feasibility of our method.

Reliability of gas holdup measurements using the differential pressure method in a cyclone-static micro-bubble flotation column

Gas holdup is one of the key parameters in flotation process. Gas holdup as measured by a differential pressure method was investigated and the relative errors compared to the average gas holdup from the volume expansion method. The errors were used to establish optimum measurement positions. The results show that the measurement position should be in the middle of the column and in the region half way from the center to the wall (the half-radius). The gas holdup along the axial direction is lower at the bottom and higher at the top of the floatation column. The gas holdup along the radial direction is lower near the wall and higher near the center of the flotation column. The average gas holdup measure- ment can be replaced by regional gas holdup values.

Numerical Investigations of Film Cooling Characteristics of Interrupted Slot and Trench Holes on a Vane Endwall

This paper describes film cooling characteristics of the novel combined configuration employing interrupted slot and trench holes on a vane endwall.Interrupted slot,formed by uneven thermal expansion between combustor and high-pressure turbine vane,can improve adiabatic film cooling effectiveness of the leading edge and pressure side-endwall junction by inhibiting the development of horseshoes vortex.Holes embedded into a straight trench were introduced to improve film efficiency comparing to cylindrical holes on vane passage endwall.The influences of lateral pressure gradient,slot coolant and step on crossflow of the hole coolant in trench were mainly discussed.Three dimensional Reynolds-averaged Navier-Stokes equations with shear stress turbulence model(SST k-ω)were used to obtain the flowfields and adiabatic film cooling effectiveness of a cascade model.Four hole blowing ratios M=0.5,1.0,1.5,2.0 and two axial positions X/Cax=–0.05,0 were considered.The coolant crossflow in trench on flat endwall of cascade passage trends to flow towards suction side due to the lateral pressure gradient rather than both sides on flat plate.For combined configuration of interrupted slot and trench holes,the step vortex rolls up hole coolant upstream of trench which changesηdistributions comparing to that on flat passage endwall.Comparing to the cylindrical holes,better film cooling performance can still be obtained when arranging trench holes under high blowing ratios.The influence of hole’s axial positions was also discussed.

Numerical investigation of thermo-physical properties of non-newtonian fliud in a modelled intestine

Several kinds of researches have been conducted on peristaltic flow of non-Newtonian fluid in modelled oesophagus,stomach and intestine.However,further investigation is still needed es-pecially in the area of mechanical shear stress,the influence of inlet temperature and velocity,Nutsselt number and the history of strain rates experienced by fluid particles.This study presents the numerical investigation of thermo-physical properties of non-Newtonian fluid in a modelled intestine.The properties investigated were fluid temperature,velocity,Nutsselt number and wall shear stress.Numerical simulation was performed by solving 3D Navier-Stokes and continuity equations.The intestinal model was drawn by using Autodesk Inventor 2017 while the numerical investigation was conducted by using ANSYS FLUENT 16.0.The Computational Fluid Dynamics solver employs the Finite Element Method(FEM)to discretize the governing equations.Chyme,Hibiscus Sabdariffa Roselle(Sobo),Soymilk(Soya)and Pap(Ogi)were the working fluids used for the investigation.Analyses of the results showed that the variation of fluid temperature and heat transfer with axial position across the length of intestinal model were not significantly influenced by the variation of the inlet velocity.Expansion of the model about the pulsating part enhanced heat transfer and nutrient delivery to the intestinal walls.Variation of the inlet velocity did not affect the average Nutsselt number.Chyme and Sobo had the highest and lowest Nutsselt number,respectively.Sobo displayed the best fluid properties considering flow behaviour while Soya dis-played the best properties for thermal history.The results presented in this study are of countless importance in medical,paramedical,engineering applications,thermoregulation system,ther-motherapy,and biomedical disciplines,where analyses and investigation of gastrointestinal tract history can be understudied.