Numerical Investigation on the Influence of Nozzle Lip Thickness on the Flow Field and Performance of an Annular Jet Pump

The performance of an annular jet pump( AJP) is determined by its area ratio A( ratio of cross sectional area of throat and annular nozzle) and flow rate ratio q( ratio of primary and secondary flow rate,Qs/Qj),while the nozzle lip thickness is neglected in the present studies. This paper presents a study on the effect of the thickness on the flow field and performance of an AJP with A = 1. 75. With the increasing flow rate ratio and nozzle lip thickness,a small vortex forms at the nozzle lip and keeps on growing. However,as the flow rate ratio or nozzle lip thickness is extremely low,the vortex at the lip vanishes thoroughly. Moreover,the recirculation width varies conversely with the nozzle lip thickness when the flow rate ratio q ≤ 0. 13. While the deviation of the recirculation width with different nozzle lip thickness is negligible with q ≥ 0. 13. Additionally the existence of nozzle lip hinders the momentum exchange between the primary and secondary flow and leads to a mutation of velocity gradient near the nozzle exit,which shift the recirculation downstream. Finally,based on the numerical results of the streamwise and spanwise vortex distributions in the suction chamber, the characteristics of the mixing process and the main factors accounting for the AJP performance are clarified.

Compact Pneumatic Pulse-Jet Pump with Venturi-Like Reverse Flow Diverter

A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity,particle mass concentration,lifting height,and compression pressure.Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser.The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity.However,even for a liquid mixture with a high viscosity of 7.38 mPa·s,a pumping capacity of 170.7 L·h-1 was observed.For a liquid mixture,two dimensionless indices of performance were found to be the ratio of Euler numbers Euout/EuDV and the suction factor q.As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump,the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.

Reaction Crystallization of Struvite in a Continuous FB MSZ Type Crystallizer with Jet Pump Driven by Compressed Air

The results of struvite reaction crystallization from diluted water solutions of phosphates （V） （0.20 mass% of PO43-） by means of magnesium and ammonium ions are presented. Continuous FB MSZ crystallizer with jet pump driven by compressed air was used. Influence of pH and mean residence time of suspension on the crystal product quality was determined. Increase in pH from 9 to 11 resulted that mean crystal size decreased nearly two-time： from 27.1 to 15.1μm for mean residence time of suspension 900 s. Elongation of this time from 900 to 3,600 s influenced struvite crystal size advantageously-it increased from 27.1 to 41.2 μm at pH 9. From the population density distributions nucleation and growth rates of struvite were calculated based on the simplest SIG model of mass crystallization kinetics in MSMPR crystallizer. Linear growth rate ofstruvite crystals decreased nearly two-time with the increase in environment pH from 9 to 11, and more than 2.5-time with the elongation of mean residence time of crystal suspension in a crystallizer from 900 to 3,600 s from 1.34× 10-8 m/s （pH 9, τ= 900 s） to 2.60×10-9 m/s （pH 11, τ= 3,600 s）.

Influence of long and short guide vanes on hydraulic performance of water-jet pump

Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to study the influence of long and short guide vanes on the water-jet pump,on the basis of conventional design,eight schemes of guide vane with different vertical heights were designed in the method of computational fluid dynamics for numerical calculation,the performance curve of water-jet pumps with different long and short guide vanes was obtained,and finally the influence of different guide vanes on hydraulic performance and internal flow was analyzed.The results show that all of schemes reducing the height of blade can improve the head and efficiency.In the schemes reducing the height on the shroud,the guide vanes that the height of the blade is equal to the height difference between hub and shroud in impeller have the highest head and efficiency.In all schemes decreasing the blade height,with the increase of the height difference,the velocity increases gradually and the distribution of turbulence kinetic energy becomes more reasonable in the guide vane outlet.The schemes reducing the height on the hub have more reasonable distribution of velocity and turbulence kinetic energy according to schemes reducing the height on the shroud.The guide vanes of long and short blades can be used to stagger the position of the diffusion flow generated by adjacent blades,which can reduce the effect of the velocity circulation and make the flow of the outlet position more stable.

Study of the Different Factors That Influence Jet Pump Performance

The objective of this work is to study experimentally the characteristics of jet pump. Suction head, driving air pressure and the percentage of the distance between throat section and nozzle are recorded. The effect of each parameter on the pump performance is investigated, in order to have a better understanding about the behavior of such pump under various conditions. A simple geometry jet pump was designed, developed and tested. The experiments show that we should be careful in increasing the suction head, and stability must be considered between the suction head and the driving air mass flow rate. While the effect of increasing Pa will stop at certain maximum of the ratio of the mass flow rate of water to air (M), that is any increase in Pa will meet no change in M. While increasing S/Dth will leads to decrease in the percentage of M because the optimum S/Dth = 0.5 so that at this value we will have the best performance and any other values for S/Dth the percentage M will decreases, but this effect is not so clear and it could be neglected. The pump performance is not so sensitive with the change of S/Dth after S/Dth = 0.5. Also this information will help improving and extending the use of the jet pump in many practical applications.

Continuous Reaction Crystallization of Struvite in a DTM Type Crystallizer With Jet Pump of Ascending Suspension Flow in a Mixing Chamber–Kinetic Approach of the Process

Reaction crystallization of struvite in water solutions containing 0.20 mass % of phosphate(V) ions by magnesium and ammonium ions addition was investigated experimentally. Process was carried out in DTM type crystallizer with liquid jet pump device in 298 K assuming stoichiometric conditions. Struvite crystals of mean size Lm 5.2-23.0 μm were produced depending on pH (9-11) and mean residence time of suspension in a crystallizer τ (900-3600 s). Under these conditions linear growth rate of struvite crystals (SIG MSMPR kinetic model) decreased 2-time with the increase in pH and 3-time with the elongation of mean residence time of crystal suspension from 7.11×10-9 m/s (pH 9, τ900 s) to 1.65×10-9 m/s (pH 11, τ3600 s). Nucleation rate varied within the 7.9×108-1.8×1010 1/(sm3) limits. Struvite product of maximal linear size exceeded 100 μm with 10 vol. % of < 3 μm fraction corresponded to pH 9 and τ3600 s.

Experimental investigation of the flow characteristics of jet pumps for zero flow-ratio conditions

Experimental research was conducted on the performance curves and the cavity evolution for different flow and geometric parameters in jet pumps for zero flow ratio(ZFR)conditions.New pressure ratio,Pr,flow ratio,qr,were used in place of the conventional performance parameters h,q,to characterize the jet pump flow performance.A super cavitation cavity in the jet pump was observed to fill most of the flow channel,which hindered further increases of the flow rate and increased qr to one,thus,created a critical point on the new P_(r)-q_(r)^(2)curve.Before the critical point,P_(r)was proportional to q_(r)^(2)with a coefficient that was much more sensitive to the area ratio than the relative throat length and the diffusion angle.After the critical point,the flow rate reached its maximum,the limiting flow rate,which only depended on the total inlet pressure and the area ratio.The total inlet pressure was proportional to the square of the limiting flow rate with a flow coefficient that was only a quadratic function of the area ratio.

Optimal performance of water-oil axial jet pump in an egyptian offshore oil field

The jet pump is an artificial lift employed when the reservoir pressure declines and the well deviation increases.The use of computer well models for optimizing the oil well output has proven to be a suc-cessful strategy,and has helped increasing the efficiency and production of numerous wells.The objective of this study was to use a production optimization technique that achieves some improve-ments,and recommend approaches toward increasing the oil well production.The effects of the motive fluid flow rate and pressure on the oil production rate were investigated to determine the optimal in-jection rate and pressure on the performance of the deep well water-oil axial jet-pump.Additionally,the effects of the well-head pressure,water cut,and roughness of tubing on oil production of this jet pump type were investigated.The results revealed that the impact on the oil lift performance is significant.The oil production increased by 19.43%,and the optimal economic value for the injection rate and pressure for the GA-1A well are 744.44 BFPD and 2722.22 psig,respectively.In summary,increasing the tubing roughness decreased the well's total liquid production.Thus,maintaining the well integrity is a very important factor because not doing so can lower the productivity by up to 20%-25%.

Numerical investigation of turbulent flow coherent structures in annular jet pumps using the LES method

Annular jet pumps that are used in hydraulic machinery have a very simple structure but very complex internal flow fields. Large eddy simulations were used to study the coherent structures in the turbulent flows in annular jet pumps with various area ratios,m. The distribution, movement and evolution of the coherent structure in the annular jet pumps are described based on vorticity,pressure and Q criteria. All the criteria demonstrate that the vortexes are mainly distributed in the recirculation region and in the mixing and the boundary layers, which have large velocity gradients. The various characteristics of the coherent structures are shown by the different criteria with the vorticity criterion describing the distribution, movement and evolution of the vortexes,the pressure criterion describing the movement and the Q criterion describing the vortex movement and evolution. The vorticity variation in the spanwise direction is larger than the variation in the streamwise direction; however, the streamwise vortex is the main mechanism driving the entrainment of the secondary flow and the mixing. The annular jet pump with m=3.33 had a higher vortex shedding frequency(about 1000 Hz) than that with m=1.72(313–417 Hz). The azimuthal instability is the main reason for the generation of the streamwise vortex from the spanwise vortex. The vortex structures in the recirculation region are very strong,but small and disordered with no periodic vortex rings.

Large eddy simulation of the transient cavitating vortical flow in a jet pump with special emphasis on the unstable limited operation stage

This paper studies the unsteady three-dimensional cavitating turbulent flow in a jet pump.Specifically,thefocus is on the unstable limited operation stage,and both the computational and experimental methods are used.In the experiments,the distribution of the wall pressure,as well as the evolution of cavitation over time,are obtained for a jet pump.Computation is carried out using the large eddy simulation,combined with a mass transfer cavitation model.The numerical results are compared with the experimental results,including the fundamental performances(the pressure ratio h and the efficiencyη),as well as the wall pressure distribution.Both the experimental and computational results indicate that the evolution of the cavitation over time in a jet pump is a quasi-periodic process during the unstable limited operation stage.The annular vortex cavitation inception,development and collapse predicted by the large eddy simulation agree fairly well with the experimental observations.Furthermore,the relationship between the cavitation and the vortex structure is discussed based on the numerical results,and it is shown that the development of the vortex structures in the jet pump is closely related to the evolution of the cavitation.The cavitation-vortex interaction is thoroughly analyzed based on the vorticity transport equation.This analysis reveals that the cavitation in a jet pump dramatically influences the distribution and the production of the vorticity.The process of the annular cavitation inception,development,and collapse involves a significant increase of the vorticity.

Large eddy simulation of turbulent flow structure and characteristics in an annular jet pump

The large eddy simulation（LES） of the flow characteristics in an annular jet pump（AJP） is conducted, and the flow characteristics are systematically analyzed from both time-averaged and instantaneous aspects. The jet expansion, the velocity distribution and the energy are considered to analyze the time-averaged evolution of the flow field in the AJP. The transient flow characteristics can also be acquired from the analysis of the turbulence intensity and the Reynolds stress. The simulation demonstrates that in the time-averaged characteristics, the potential cores increase linearly with the increase of the flow ratio. With the flow development, the jet half-width gradually increases and the residual energy coefficient decreases. Compared with the distribution of the time-averaged axial velocity, that of the instantaneous velocity is more complex and disorderly. The high intensity of the axial turbulence mainly occurs in the mixing layer and the near-wall regions of the diffuser. The annular distribution of the Reynolds stress is mainly in the mixing layer and the recirculation region. There is a low-stress zone between the mixing layer and the high-stress region in the wall-boundary layer. The intensity of the spanwise vortexes is larger than that of the streamwise vortexes, and therefore, the former make greater contribution to the total vorticity. This research provides a better understanding of the flow characteristics in the AJP.

Numerical analysis of bubble dynamics in the diffuser of a jet pump under variable ambient pressure

Recent studies have shown that the collapse of cavitation bubbles in a jet pump can generate an extremely high pressure with many potential applications. The dynamics of the bubble is governed by the Rayleigh-Plesset equation. With the bubble dynamics equation and the heat and mass transfer model solved with the Runge-Kutta fourth order adaptive step size method, the oscillations of the bubble in the diffuser of the jet pump are assessed under varied conditions. To obtain the pressure variation along the diffuser, the Bernoulli equation and the pressure measured in experiment are coupled. The results of simulation show that a transient motion of the bubbles can be obtained in the diffuser quantitatively, to obtain the pressure and temperature shock in the bubble. Moreover, increasing the outlet pressure coefficient would result in a more intense bubble collapsing process, which can be used in the subsequent studies of the cavitation applications. The predictions are compared with experiments with good agreement.

叶片数对无轴泵喷推进器性能的影响

为丰富无轴泵喷推进器噪声性能优化理论,研究了叶片数对无轴泵喷推进器性能的影响,重点探究了不同叶片数下无轴泵喷推进器内的压力脉动变化规律。基于计算流体力学中的有限体积法离散RANS方程,应用RNG k-ε湍流模型封闭计算模型,采用SIMPLEC进行压力-速度耦合,对不同叶片数下的无轴泵喷推进器内部流场进行了非定常数值模拟计算,并对计算结果进行了详细的对比分析。研究结果表明:随叶片数的增加,无轴泵喷推进器模型的扬程、效率和推力均逐渐增大,叶片表面压力分布更加均匀,叶轮轮缘和中部的压力脉动均明显降低,叶轮进出口主频处的压力脉动幅值从轮缘向中心逐渐减小。

矢量泵喷推进潜航器回转性能研究

泵喷推进器已经逐渐成为现代潜航器的首选,矢量推进器也在航空航天领域得到了广泛的应用。为了解决传统依赖船舵控制在低航速下控制效率低的问题以及提高潜航器回转性能,矢量推进器在潜航器上的应用已逐步成为国内外关注的热点。本文考虑大舵角(喷管偏角)下潜航器各参数非线性的影响,建立潜航器水平面操纵运动的非线性模型。通过仿真研究分析船-舵-推进器、船-矢量推进器和船-舵-矢量推进器三种不同的控制方法下潜航器在低航速、控制泵喷推进器转速、控制潜航器轴向航速三种不同条件下作水平面回转运动时的回转性能,结果表明矢量泵喷推进器可以有效改进潜航器的回转性能。

舟山LNG取水泵站泥沙减淤清淤试验研究

LNG接收站取水流道内水流形态复杂,泥沙淤积问题往往难以避免,特别是在含沙量较高水域,流道内泥沙淤积可能威胁接收站的正常运营。为实现LNG取水泵站不停机条件下清淤,开展取水泵站射流冲刷物理模型试验,模拟了射流冲沙装置开启后吸水间射流水流特征及冲刷效果,探究了射流冲刷设置的喷嘴与翼墙夹角、射流流量、冲刷时间等因素影响下流道内减淤清淤效果。试验结果表明,在理想状态下吸水间射流冲沙装置连续作用12h基本可达到较为理想的清淤效果;一次大风浪过后,装置连续作用0.5h基本可达到较为理想的清淤效果。清淤效果视射流流量、喷嘴与翼墙夹角以及冲刷时间不同而有差别。结合取水泵站泥沙淤积物理模型试验研究成果,取水泵站淤积区主要发生在前池、过滤池末端、吸水间和消防泵附近,建议在这些区域安装射流冲沙装置,实现不停机状态下的减淤清淤,提高取水安全保证率,从而提高运营效益。

轮缘驱动泵喷推进器的螺旋桨性能优化方法

为得到适用于新型轮缘驱动泵喷推进器的螺旋桨,在传统泵喷推进器螺旋桨的基础上进行性能优化方法研究十分必要。利用CFD数值模拟方法对推进器进行水动力仿真,分别对比3个不同的螺旋桨孔径比和3种桨叶厚度分布方案对推进器敞水性能的影响。对比结果发现小孔径比对推进器敞水性能更为有利,其中0.1孔径比推进器比0.3孔径比推进器的敞水效率最大提升了3.25%。厚度反置导致轮缘驱动螺旋桨高半径处压力分布不均匀,扭矩大幅提升,敞水效率大幅降低。轮缘驱动螺旋桨的厚度越小,扭矩越低,敞水效率越高,其中方案C桨的扭矩比方案A最大降低了21.74%,敞水效率最大提升了12.9%。

叶顶间隙对螺旋混流式喷水推进泵内流及推进特性的影响

喷水推进泵是舰船泵喷推进系统的核心部件,喷水推进泵在工作过程中,叶顶间隙处所产生的泄漏流会严重影响混流泵的工作性能。为了探讨叶轮叶顶间隙对喷水推进泵推进特性的影响,本文定义了叶顶间隙系数τ,设计了六种不同叶顶间隙系数模型并使用Ansys进行仿真分析,最终得到叶顶间隙对于喷水推进泵内流以及推进特性的影响规律。结果表明:随着叶顶间隙系数的增大,叶顶间隙处泄漏流逐渐增加,泄漏涡影响范围变大,轴向推力随着叶顶间隙系数的增大呈负指数下降,叶顶间隙处泄漏量随指数上升,喷水推进泵内流损失增加,推进效率持续减小,并且在大流量工况下叶顶间隙对喷水推进泵推进特性影响最大,在设计的六套模型中,叶顶间隙系数为0.08,叶顶间隙为0.16mm时效率最高。通过本文的研究可以发现,叶顶间隙对于喷水推进泵内流以及推进特性影响较大,在设计时应尽量减小叶顶间隙。

基于射流补水的水泵水轮机S特性改善研究

针对水泵水轮机的“S”特性提出了在导叶顶盖位置无叶区处加装注水管的解决方案,并模拟了注水管安装在不同位置时的“S”特性曲线,分析了加装注水管后转轮区域内流线及转轮各叶道流量的分布规律。结果表明,于导叶顶盖加装注水管可以有效改善转轮内部流动,减轻转轮和导叶内部流动的相互影响,减小叶道涡的尺寸,同时有效缓解了转轮各叶道流量分布不均的现象。在注水管处于无叶区中段和活动导叶附近时,对“S”特性的改善效果明显。

导叶叶片数对喷水推进泵瞬态特性的影响

为揭示喷水推进泵不同导叶叶片数时的瞬态特性规律,基于DES混合模拟和FEM声学有限元方法,对喷水推进泵流场和声场进行数值模拟,并进行试验,验证了瞬态特性数值计算方法的准确性,研究了不同导叶叶片数(Z=5,6,7)对喷水推进泵推力、压力脉动、内流诱导噪声等性能的影响规律.结果表明:随着导叶叶片数增大,喷水推进泵推力先减小后增大,流量逐渐减小,转矩逐渐增大;导叶叶片数对叶轮出口压力脉动分布规律影响较小,对压力脉动主频处幅值有较大影响,轮毂处压力脉动幅值受导叶叶片数增大先减小后增大,轮缘和流道中心处幅值随着导叶叶片数增大逐渐减小;导叶叶片数变化会改变内流诱导噪声主频,增大导叶叶片数有利于降低喷水推进泵内流诱导噪声主频处幅值和总声压级.

冰粒空气射流喷射器结构的关键参数

目前在冰粒射流表面处理领域普遍存在冰粒易粘结和堵塞等问题,严重影响表面处理效率。基于射流泵基本结构,提出冰粒即时制备和利用的冰粒空气射流表面处理技术,可解决冰粒粘结堵塞问题。为实现冰粒的高效利用和冰粒空气射流的高速喷射,研制冰粒引射和加速一体化喷射器结构。系统性研究喷射器工作喷嘴位置(L_(d))、膨胀比(n)和加速喷嘴直径比(D_(n))、长径比(L_(n))对冰粒引射能力和加速的影响,以冰粒冲击动能为综合评判指标,确定喷射器结构参数,并进行表面处理试验验证。研究结果表明:在2 MPa气压下,喷射器喷嘴参数为n=1.5,D_(n)=4.0,L_(d)=4,L_(n)=0 mm时,可以充分引射加速冰粒。该结构参数下进行铝合金板脱漆试验,可获得较大的脱漆半径并使铝合金板表面更光滑,铝合金表面粗糙度由3.194±0.489μm变为1.156±0.136μm。冰粒的即时制备和利用解决了冰粒空气射流技术工程应用时存在的冰粒粘结和储存问题,可为材料表面处理领域提供一种新的技术方法。