无叶扩压器进口条件和几何形状对流动分离的影响

本文通过理论计算和部分实验对比,分析了无叶扩压器中产生流动分离的原因和条件,得出了气流进口条件和扩压器几何参数对流动分离起始位置的影响规律。在无叶扩压器中,气流进口流动角,进口速度场的畸变以及扩压器壁面倾角等对流动分离的位置有很大影响。     

氯气压缩机的高效设计方法及数值模拟结果分析

针对某企业年产7万吨的氯气压缩机,进行了基于叶轮表面速度最优分布的三元离心叶轮、扩压器、蜗壳设计及CFD叶轮内部流动分析,得出了设计方法可靠等3点结论。     

二维扩压器的优化设计

本文根据二不可压紊流附以理论推导得到扩压器面最优化速度分布的一般表达式，运用最优控制的直接解法－－多重打法，建立了适于求解的数学模型，并得到了满足约束的壁面最优化速度分布，该计算结果与实验结果及用Ｐｏｎｔｒｙａｇｉｎ极大值原理的计算结果均甚为吻合，该方法可推广至带吹吸气的扩压器的优化设计中，亦可推广到其它类型流道设计中。     

离心风机叶片扩压器内部流场的试验研究

利用激光多普勒测速仪(LDV)测量了离心风机叶片扩压器的内部流场。试验中，分别在大流量和小流量两个工况下对离心风机叶片扩压器的内部流场进行了详细的测量，由测量结果分析了叶片扩压器流道中前侧板侧、中间和后侧板侧三个回转面上气流速度的矢量分布和等值线分布，以及气流从扩压器的叶片凹面到凸面、从扩压器的进口到出口的流动特性。结果表明在扩压器喉部附近靠近扩压器凹面的局部区域，速度的方向会向叶片凸面发生较大角度的偏转；随着流量的增大，该区域将会向叶片扩压器的下游及流道宽度方向发展。     

离心式压缩机叶片扩压器的实验研究

利用电子扫描阀测压系统，测量了不同工况下离心式压缩机叶片扩压器内部的静压分布，并做了该机的级性能实验。实验结果表明，在不同工况下叶片扩压器内部的静压分布差异很大，叶片扩压器在设计工况下具有较高的效率，但在变工况时，扩压器流道壁面边界居容易发生分离，导致冲击损失较大，效率下降很快。     

无叶扩压器内部非定常流动的PIV测量

利用激光粒子成像速度仪(PIV)测量了无叶扩压器内部的非定常流场.试验发现在无叶扩压器内,沿扩压器宽度方向,气流速度分布是不均匀的,在靠近叶轮叶片吸力面侧形成了一个低速区,这个低速区是由叶轮出口的尾迹流造成的.这个低速区的存在影响了无叶扩压器的扩压能力和效率.     

半高导叶扩压器的研究

半高导叶扩压器,可以改善扩压器内部流动,提高扩压器的压力恢复系数,改善压缩机的级性能。本文建立了一种分析半高导叶扩压器内部流动的简化计算模型,计算结果与实测结果比较表明,速度分布符合得较好,但出口气流角相差较大。     

离心式空气压缩机内流动特性研究

叶轮流动特性表明其前缘速度最大,尾缘处部分分离流动,而中间面两侧速度并不均匀。弯道和扩压器内部流场稳定,没有明显变化。通过对离心式空气压缩机整级流动特性分析表明:扩压器和弯道内流场则较为稳定,叶轮和扩压器交界面处流动速度较高,回流器内流场变化较为剧烈。通过对其内流动分析,可以为设计大工况下高效低耗的离心机提供理论指导。     

基于FLUENT的混流式风机整机流场数值模拟

利用fluent软件对-混流式风机的整机内部流场进行了数值模拟,捕捉到了风机内部压力分布和速度分布等许多重要的流动现象,证实了扩压器、叶轮间相互作用引起的整流场不对称性,并预示了叶轮内部的重要流动特征.所得到的分析结果对探讨影响通风机效率的原因、优化叶型设计等研究内容提供了重要的理论依据.     

组装式压缩机叶片扩压器设计及性能分析

针对某组装式压缩机用半开式小流量系数叶轮,设计了两种不同型式的叶片扩压器,并对半开式叶轮和叶片扩压器组成的模型级的内部流动进行数值模拟,以及对两种扩压器的流场分布和性能进行了分析。试验结果表明:采用机翼形扩压器相比楔形扩压器,气动性能得到明显提高。     

Simulation and optimization of a piezoelectric micropump for medical applications

We designed a valveless micropump excited by a piezoelectric actuator for medical applications. The complete electric–fluid–solid coupling model is built upon using ANSYS software (Canonsburg, PA) to investigate the behaviors of the micropump. The effects of the geometrical dimensions on the micropump characteristics and its efficiency are analyzed. The simulation results show that there is an optimal thickness of the piezoelectric layer to obtain a large pump flow, and that this optimal thickness is affected by the material and the thickness of the pump membrane. To enhance the performance of the micropump, some important diffuser parameters, such as the diffuser length, the diffuser angle, and the neck width, should be optimized. However, the variations of the diffuser’s geometrical dimensions do not affect the optimal thickness of the piezoelectric layer.     

低速风洞扩压段扩压角的优化设计与讨论

合适的扩压角对于风洞的设计十分重要。本文综合考虑扩压段扩压效率和扩压段尺寸等因素,通过Matlab数值分析计算得出理论最佳扩压角。在保持扩压效率不减少的情况下,增大扩压角,并最终取得一个高扩压效率、合理尺寸及低耗材的扩压段设计。结合实例,加以演示,给出风洞扩压段扩压角的最佳选取方法。     

Development of a performance prediction method for centrifugal compressor channel diffusers

A hybrid performance prediction method is proposed in the present study. A channel diffuser is divided into four subregions: vaneless space, semi-vaneless space, channel, and channel exit region. One-dimensional compressible core flow and boundary layer calculation of each region with an incidence loss model and empirical correlation of residuary pressure recovery coefficient of a channel predict the performance of diffusers. Three channel diffusers are designed and tested for validating the developed prediction method. The pressure distributions from an impeller exit to the channel diffuser exit are measured and discussed for various operating conditions from choke to nearly surge conditions. The strong non-uniform pressure distribution which is caused by impeller-diffuser interaction is obtained over the vaneless and semi-vaneless spaces. The predicted performance shows good agreement with the measured performance of diffusers at a design condition as well as at off-design conditions.     

Influence of divergent section on flow fields and discharge coefficient of ISO 9300 toroidal-throat sonic nozzle

The effect of divergent section of ISO 9300 toroidal-throat nozzle on discharge coefficient was analyzed based on the inviscid transonic flow model and laminar boundary layer theory. A series of numerical simulations were conducted to verify the results of theory, and investigate the effect of divergent section length L and diffuser angle θ operated at different Reynolds numbers. Combined with the numerical results in this study and the experimental data reported by Nakao, it showed the discharge coefficient increases with the rise of diffuser angle θ or the drop of divergent section length L. A lot of new results about the effect of divergent section were obtained. It indicated that the effect of divergent section on discharge coefficient of ISO 9300 toroidal-throat nozzle should be considered when Re<1.1×10⁴. At last, a concept of effective critical flow was proposed to discuss the effect of divergent section on discharge coefficient.     

基于机器学习的斜流压气机多目标优化

针对100公斤级涡喷发动机,为了提高斜流压气机性能,利用编码搭建的BP神经网络-遗传算法平台,对叶轮入口轮毂半径、叶轮叶片数、扩压器轴向长度和扩压器叶片数进行压气机级的多目标优化。结果表明:优化后的压气级总压比提高了3.2%,等熵效率提高了7.9%,工作稳定性大幅度提高;优化后的斜流压气机叶轮出口处的泄漏流得到明显的改善,扩压器转弯段逆压梯度和附面层影响减小。     

Numerical study on performance of supersonic inlets with various three-dimensional bumps

Numerical investigations were performed with a supersonic inlet system installed with a three-dimensional bump which was substituted for a diverter or conventional ramp-type compression systems at Mach 2. The modified inlets were designed to have two oblique shocks and a terminal normal shock followed by a subsonic diffuser, with a circular cross-section throughout. A numerical analysis was conducted to understand the three-dimensional flow field including shock/boundary layer interactions that occur around a three-dimensional bump and to evaluate the performance of the supersonic inlets. The current numerical simulations showed a bump-type inlet based on a conventional ramp-type inlet can provide an improvement in total pressure recovery downstream of the shock/boundary-layer interaction over a ramp-type inlet.     

基于MEMS的压电微泵建模与优化

以压电驱动的无阀微泵为研究对象,根据扩张管/收缩管的压力损失系数和连续方程,建立了无阀微泵的理论模型。利用有限元分析软件,建立了无阀微泵有限元模型,进行了耦合场仿真分析。模拟并分析了不同边界条件下驱动电压、电压频率、泵膜厚度、压电薄膜厚度和压电材料对无阀微泵输出特性的影响。仿真结果显示,无阀微泵具有很好的整流特性,并且驱动电压越大,输出特性越好。在局部固定边界条件下,当压电薄膜上施加电场强度为500 V/mm的驱动电压时,存在最优的压电薄膜厚度,使得微泵的输出流量最大。研究结果为无阀微泵的优化设计提供了依据。     

Shape optimization of two-dimensional thermal conducting solid using boundary integral equation formulation

A method for shape design sensitivity analysis of two-dimensional thermal conducting solid is presented using the material derivative concept and the adjoint variable method. A general thermal boundary condition with heat convection is considered in addition to prescribed temperature and heat flux. The method for deriving the sensitivity formula is based on standard direct boundary integral equation formulation. The sensitivity of a general functional depending on temperature and heat flux is considered. The method is then applied to obtain the sensitivity analysis is demonstrated by a hollow cylinder problem with exact solution. A weight minimization problem of a thermal diffuser is considered as a practical application. The sensitivity by the presented method is compared with that by finite differences and an optimal shape is found by use of an optimization routine.     

COMPARISON OF TWO METHODS TO INCREASE TIP CLEARANCE AND ITS EFFECT ON PERFORMANCE OF TURBOCHARGER CENTRIFUGAL COMPRESSOR STAGE

Tip clearance between the blade tip and casing of a centrifugal compressor can be varied through two methods:by changing the blade height(M1)or by changing the casing diameter(M2). Numerical simulations are carried out to compare these two methods and their effect on the stage and impeller performance.The impeller and diffuser are connected through rotor stator boundary using frozen rotor approach.Overall stage performance and the flow configuration have been investigated for nine tip clearance levels from no gap to 1 mm.Impeller and diffuser performances are also pre- sented separately.It has been found that the overall and impeller performance are comparatively better for M1 below tip clearance of 0.5 mm whereas M2 is found advantageous above 0.5 mm of tip clear- ance.Both M1 and M2 show performance degradation with the increase in tip clearance.Two models have been proposed for the stage total pressure ratio and efficiency,which are found to be in agree- ment with experimental results.The impeller efficiency and the pressure ratio are found to be maxi- mum at tip clearance of 0.1 mm for both the cases however minimum diffuser effectiveness is also observed at the same clearance level.Diffuser effectiveness is found to be maximum at zero gap for both cases.As it is practically impossible to have zero gap for unshrouded impellers so it is concluded that the optimum thickness is 0.5 mm onwards for M1 and 0.5 mm for M2 in terms of diffuser effec- tiveness.Mass averaged flow parameters,entropy,blade loading diagram and relative pressure fields are presented,showing the loss production within the impeller passage with tip clearance.