Cavitation Optimization for a Centrifugal Pump Impeller by Using Orthogonal Design of Experiment

Cavitation is one of the most important performance of centrifugal pumps. However, the current optimization works of centrifugal pump are mostly focusing on hydraulic efficiency only, which may result in poor cavitation performance. Therefore, it is necessary to find an appropriate solution to improve cavitation performance with acceptable efficiency. In this paper, to improve the cavitation performance of a centrifugal pump with a vaned diffuser, the influence of impeller geometric parameters on the cavitation of the pump is investigated using the orthogonal design of experiment （DOE） based on computational fluid dynamics. The impeller inlet diameter D1, inlet incidence angle Aft, and blade wrap angle ~0 are selected as the main impeller geometric parameters and the orthogonal experiment of L9（3＂3） is performed. Three-dimensional steady simulations for cavitation are conducted by using constant gas mass fraction model with second-order upwind, and the predicated cavitation performance is validated by laboratory experiment. The optimization results are obtained by the range analysis method to improve cavitation performance without obvious decreasing the efficiency of the centrifugal pump. The internal flow of the pump is analyzed in order to identify the flow behavior that can affect cavitation performance. The results show that D1 has the greatest influence on the pump cavitation and the final optimized impeller provides better flow distribution at blade leading edge. The final optimized impeller accomplishes better cavitation and hydraulic performance and the NPSHR decreases by 0.63m compared with the original one. The presented work supplies a feasible route in engineering practice to optimize a centrifugal pump impeller for better cavitation performance.

Mathematical model for abrasive suspension jet cutting based on orthogonal test design

This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test design is applied to cutting stainless steel. Through range analysis on experiment results, the optimal process conditions for the cutting depth and the kerr ratio of the bottom width to the top width can be determined. In addition, the analysis of ranges and variances are all employed to identify various factors： traverse rate, working pressure, nozzle diameter, standoff distance which denote the importance order of the cutting parameters affecting cutting depth and the kerf ratio of the bottom width to the top width. ~rthermore, non-linear regression analysis is used to establish the mathematical models of the cutting parameters based on the cutting depth and the kerr ratio. Finally, the verification experiments of cutting parameters＇ effect on cutting performance, which show that optimized cutting parameters and cutting model can significantly improve the prediction of the cutting ability and quality of ASJ.

Experimental investigation of key parameters pertinent to multi-hole orifice throttling characteristic

This study firstly defines a set of arrangement rule for perforated holes of multi-hole orifice(MO), and then presents three critical geometrical parameters including total number of performated hole, equivalent diameter ratio and distribution density of perforated holes, which are to quantify MO structure. This paper built the throttling test apparatus for nice test MO plates, which were designed according to orthogonal theory. The experiments were conducted to investigate the effect of three critical geometerical parameters on the pressure loss coefficient of test MOs. Results show that equivalent diameter ratio is the dominant prameter affecting MO throttling characterstic.

Simultaneous Optimization of Incomplete Multi-Response Experiments

This article attempts to develop a simultaneous optimization procedure of several response variables from incomplete multi-response experiments. In incomplete multi-response experiments all the responses (p) are not recorded from all the experimental units (n). Two situations of multi-response experiments considered are (i) on units all the responses are recorded while on units a subset of responses is recorded and (ii) on units all the responses (p) are recorded, on units a subset of responses is recorded and on units the remaining subset of responses is recorded. The procedure of estimation of parameters from linear multi-response models for incomplete multi-response experiments has been developed for both the situations. It has been shown that the parameter estimates are consistent and asymptotically unbiased. Using these parameter estimates, simultaneous optimization of incomplete multi-response experiments is attempted following the generalized distance criterion [1]. For the implementation of these procedures, SAS codes have been developed for both complete (k ≤ 5, p = 5) and incomplete (k ≤ 5, p1 = 2, 3 and p2 = 2, 3, where k is the number of factors) multi-response experiments. The procedure developed is illustrated with the help of a real data set.

Solution for integer linear bilevel programming problems using orthogonal genetic algorithm

An integer linear bilevel programming problem is firstly transformed into a binary linear bilevel programming problem, and then converted into a single-level binary implicit programming. An orthogonal genetic algorithm is developed for solving the binary linear implicit programming problem based on the orthogonal design. The orthogonal design with the factor analysis, an experimental design method is applied to the genetic algorithm to make the algorithm more robust, statistical y sound and quickly convergent. A crossover operator formed by the orthogonal array and the factor analysis is presented. First, this crossover operator can generate a smal but representative sample of points as offspring. After al of the better genes of these offspring are selected, a best combination among these offspring is then generated. The simulation results show the effectiveness of the proposed algorithm.

Experimental Optimization of Jet Self-Priming Centrifugal Pump Based on Orthogonal Design and Grey-Correlational Method

The novel jet self-priming centrifugal pump,as important modern irrigation equipment,is widely used in large-scale irrigation,mine drainage and so on.In order to improve the profile streamline of blade,the inlet shape of impeller was designed as distorted and the outlet shape as cylindrical,which can not only improve the pump efficiency,but also shorten the self-priming time.Further,the novel jet self-priming system was proposed,by employing the jet nozzle and check valve to improve the velocity of self-priming.Meanwhile,nine different structure jet nozzles were designed based on the orthogonal design method,and the relevant self-priming experiments were performed on I level accuracy test bench in Jiangsu University.According to the greycorrelational analysis,the influence of the nozzle geometry parameters on the self-priming performance was obtained.The relationship between self-priming time and self-priming height was discussed.The test results showed that the hydraulic design of jet self-priming centrifugal pump was reasonable;all indicators met the Chinese national standard;the head reached 21.04 m and efficiency was 72.8%under the design flow condition.What is more,the self-priming performance was obviously improved by adjusting the geometrical parameters of nozzle.When the height of the self-priming process was 5.3 m,the self-priming time reached 62 s,which was much shorter than the national standard.Therefore,this research could provide reference for designing the structure of jet self-priming centrifugal pump.

Finite element modal analysis and experiment of rice transplanter chassis

The vibration problem during the operation of rice transplanters is the most common phenomenon.In order that the static and dynamic characteristics of the rice transplanter chassis can meet the requirements of more stable operation,the research took the 2ZG-6DK rice transplanter as the research object to carry out a vibration reduction optimization study.In the research,the Pro/Engineer 5.0 software was first used to model the chassis of the rice transplanter.The constructed finite element model was revised by using the structural parameter revision method and the mixed penalty function method.The model was imported into ANSYS Workbench to solve the modal frequency and vibration shape of the rice transplanter chassis.Based on the MAC(modal assurance criterion)criterion,modal tests were carried out to verify the accuracy of the finite element theoretical analysis.Through the analysis of the characteristics of the external excitation frequency,the chassis is structurally optimized to avoid resonance caused by the natural frequency of the chassis falling within the road excitation frequency range.The final optimization results showed that the first four orders of modal frequencies of the chassis were adjusted to 32.083 Hz,33.751 Hz,42.517 Hz,and 50.362 Hz,respectively,in the case that the chassis mass was increased by 6.714 kg(8.8%).They all avoid the range of road excitation frequency(10-30 Hz)so that the rice transplanter can effectively avoid the resonance phenomenon during operation.This study can provide a reference for the design and optimization of the chassis structure of transplanter.

Objective array design for three-dimensional temperature and salinity observation:Application to the South China Sea

In this study,a moored array optimization tool(MAOT)was developed and applied to the South China Sea(SCS)with a focus on three-dimensional temperature and salinity observations.Application of the MAOT involves two steps:(1)deriving a set of optimal arrays that are independent of each other for different variables at different depths based on an empirical orthogonal function method,and(2)consolidating these arrays using a K-center clustering algorithm.Compared with the assumed initial array consisting of 17 mooring sites located on a 3°×3°horizontal grid,the consolidated array improved the observing ability for three-dimensional temperature and salinity in the SCS with optimization efficiencies of 19.03%and 21.38%,respectively.Experiments with an increased number of moored sites showed that the most cost-effective option is a total of 20 moorings,improving the observing ability with optimization efficiencies up to 26.54%for temperature and 27.25%for salinity.The design of an objective array relies on the ocean phenomenon of interest and its spatial and temporal scales.In this study,we focus on basin-scale variations in temperature and salinity in the SCS,and thus our consolidated array may not well resolve mesoscale processes.The MAOT can be extended to include other variables and multi-scale variability and can be applied to other regions.

Parallel Minimax Searching Algorithm for Extremum of Unimodal Unbounded Function

In this paper we consider a parallel algorithm that detects the maximizer of unimodal function f(x) computable at every point on unbounded interval (0, ∞). The algorithm consists of two modes: scanning and detecting. Search diagrams are introduced as a way to describe parallel searching algorithms on unbounded intervals. Dynamic programming equations, combined with a series of liner programming problems, describe relations between results for every pair of successive evaluations of function f in parallel. Properties of optimal search strategies are derived from these equations. The worst-case complexity analysis shows that, if the maximizer is located on a priori unknown interval (n-1], then it can be detected after cp(n)=「2log「p/2」+1(n+1)」-1 parallel evaluations of f(x), where p is the number of processors.

基于多因素正交实验的关中民居节能优化分析

为解决陕西关中地区民居建筑围护结构热工性能不佳、采暖效率低的问题,本文以关中典型民居为研究对象,从建筑外围护结构和窗墙比方面展开关中民居节能优化分析。结合现场测试调研数据,通过DesigBuilder软件模拟能耗,探究围护结构构造和窗墙比大小对关中民居建筑热负荷、冷负荷、全生命周期投资收益比的影响,采用多因素正交实验方法耦合分析各优化方案的节能性与经济性,选出最适宜的综合节能策略。结果表明关中民居最佳节能优化策略为外墙加设80 mm厚EPS保温层、屋顶加设60 mm厚XPS保温层、外窗改用普通中空5+9A+5玻璃、北向窗墙比0.1、南向窗墙比0.3。优化后关中典型民居节能61.98%,冬季典型气象日室内平均温度上升2.78℃。

参芪二皮冬茶颗粒成型工艺研究

目的:优化参芪二皮冬茶颗粒成型工艺。方法:以药辅比、润湿剂浓度及用量为影响因素,采用正交试验考察参芪二皮冬茶颗粒的成型工艺参数,采用D-最优混料设计筛选最佳辅料配比,以确定参芪二皮冬茶颗粒的最优成型工艺,并进行验证。结果:优化的成型工艺:干膏粉与混合辅料[糊精-甘露醇-乳糖(0.667∶0.167∶0.167)]比例1∶0.6,润湿剂(90%乙醇)用量30%,所制得的颗粒成型率、溶化率、堆密度、休止角、吸湿率分别为92.44%、90.89%、0.46 g/mL、20.17°、7.31%,颗粒临界相对湿度为76%。结论:该工艺方法科学合理,稳定可靠,操作简便,可为参芪二皮冬茶颗粒的大生产提供参考。

不同结构参数对高速开关阀液压力的影响研究

因其具有价格低廉、抗污染性强等优点,高速开关阀已被广泛运用到各种车辆的制动系统中,其动态性能直接影响到车辆的制动效果,而阀芯所受的液压力是决定高速开关阀动态特性优劣的关键参数。针对不同参数对高速开关阀液压力的影响,以及实际工程中阀芯液压力难以测量的问题,采用计算流体动力学(CFD)对高速开关阀进行了数值模拟。首先,基于有限体积法(FVM),建立了不同开度、压差、温度、以及结构参数(阀座节流孔直径和锥角)的三维仿真模型;然后,对比不同网格数量的仿真结果,排除了网格数量对于仿真结果的影响,并详细分析了各参数对液压力的影响,得出了高速开关阀液压力与各参数之间的变化规律;最后,采用响应面分析结合遗传算法对开关阀的结构参数进行了优化。研究结果表明:随着阀芯开度的增加,节流区域发生了转变;较大的压差会导致液压力产生较大幅度的变化;相较于高温,低温对液压力有着更加显著的影响;对结构参数进行优化后,最小开度的液压力提高了49.2%,提高了阀控制稳定性,为高速开关阀线性控制设计提供了理论基础。

高压连接器插座外壳模具设计与多目标注塑工艺优化

以高压连接器插座外壳为研究对象,进行模具设计和注塑工艺优化,在模具设计方面,将点浇口方案改为牛角式进胶方案,使模具结构由三板模简化为两板模。将牛角式浇口设计为嵌件结构,方便电火花成型加工,也方便浇口断裂时及时清理。为提高冷却效率,型腔部分采用环绕式水路设计,型芯部分采用水井式水路设计。由于产品下半部分壁厚较小,采用“圆顶杆+扁顶杆”结合的顶出方式,解决产品难以脱出的问题,同时顶杆与顶杆孔的间隙可以跑气,解决型芯狭窄区域的困气问题。使用Moldex3D对浇注系统、冷却系统设计方案进行仿真分析,验证设计方案合理,并获取初步注塑工艺参数。在工艺优化方面,以体积收缩率标准差和最大翘曲量为响应进行多目标注塑工艺优化,采用“正交试验+响应曲面实验”的方法优化,当熔体温度为228℃,保压压力237.5 MPa,保压时间5.88 s时多目标工艺参数最优,输入Moldex3D软件进一步模拟,得到体积收缩率标准差为0.937%,降低45.39%;最大翘曲量为0.181 mm,降低21.30%,说明优化方案可行。

赤藓糖醇玫瑰酒的研制及品质分析

以食用玫瑰、糯米酒为主要原料,赤藓糖醇作为甜味剂,通过单因素试验和正交试验对玫瑰酒的泡制工艺进行优化,并采用色差仪、能量分析仪、气相色谱-离子迁移谱(gas chromatography-ion mobility spectroscopy,GC-IMS)仪、全自动氨基酸分析仪对其色香味进行品质分析。结果表明,赤藓糖醇玫瑰酒最佳泡制工艺条件为酒精度25%vol、玫瑰花与酒泡制比例1∶150(g/mL)、赤藓糖醇添加量8%、泡制时间21 d。此工艺条件下,玫瑰酒感官总分最高,色差特征L值为36.09、a值为11.51、b值为5.05;每100 g玫瑰酒含能量910.70 kJ、蛋白质0.47 g、碳水化合物13.97 g;共有18种游离氨基酸,其中必需氨基酸有6种,占总氨基酸含量的13.45%;GC-IMS检测到62种挥发性成分,其中乙酸乙酯、丁酸乙酯、2-呋喃甲醇、香叶醇、3-甲基-1-丁醇、麦芽酚、β-蒎烯以及己醛占总挥发性物质的46.59%,是构成玫瑰酒的主要特征风味物质。试验得到的低糖型玫瑰酒品质优良、风味独特。

基于达朗贝尔原理的废塑料薄膜耦合振动分选与参数优化设计

为了提高废塑料薄膜的回收效率和利用价值,提出一种废塑料薄膜耦合振动分选方法;基于达朗贝尔原理,建立所提出方法的动力学方程,分析分选效果的影响因素,确定分选效果的评价指标;确定废塑料薄膜耦合振动分选设备的优化设计变量,建立优化目标函数,编写优化程序,得到最优的废塑料薄膜耦合振动分选设备参数;研制废塑料薄膜耦合振动分选设备,对所建立动力学方程进行验证实验。结果表明:当振动床面振动角为48.63°,振动电机角速度为27.62πrad/s且振动床面横、纵向倾角分别为9.41°、12°时,分选效果最好;验证实验的结果与优化程序的结果相近,验证了所建立动力学方程的正确性;相对于传统的风力振动分选方法,所提出方法在相同分选时间内的分选距离增加18.66%,分选效果更好,验证了所提出方法的有效性。

液控随钻扩眼器球座冲蚀规律及结构优化

在随钻扩眼的过程中,扩眼器球座的冲蚀较为严重,尤其是球座旁通孔附近。基于冲蚀理论与固液两相流理论,结合DPM离散相模型对扩眼器球座进行冲蚀模拟分析,研究不同因素对扩眼器球座冲蚀的影响规律。此外,利用正交试验方法,研究各参数对冲蚀磨损的影响程度,并优化扩眼器球座结构。通过极差和方差分析可知:影响球座冲蚀磨损的因素依次为流量>含砂比>颗粒直径,最优工艺参数组合为:流量35 L/s、含砂比3%、黏度0.028 Pa·s、颗粒直径0.25 mm、颗粒密度1 500 kg/m~3,此时球座的冲蚀率最小,为4.52×10^(-6) kg/(m~2·s)。为了减少扩眼器球座的冲蚀,对球座进行结构优化,优化后球座旁通孔角度为顺时针倾斜45°、圆角半径为7 mm、个数为6,相比优化前的球座冲蚀率降低了24%。

基于Moldflow的车身后护板微孔发泡注塑工艺多目标优化

使用Moldflow软件模拟车身后护板注塑工艺,采用正交试验及灰色关联分析结合熵权法优化注塑工艺参数,并进行了实际试模验证。结果表明:使用微孔发泡注塑成型可实现车身后护板减重及降低翘曲变形量;优化的工艺参数为熔体温度235℃,模具温度35℃,充填时间3.5 s,充填体积百分比92%,初始气体含量1.2%(w),所制零件总质量为1362.2 g,z方向翘曲变形量为1.006 mm,较采用微孔发泡默认工艺组合分别减少了18.4 g,0.478 mm;采用灰色关联分析结合熵权法对工艺优化能满足产品减重和降低翘曲变形量的要求。

寒冷地区新建农宅能耗测试及节能优化研究

通过对沧州地区某新建农宅进行室内热环境和围护结构采暖能耗的测试,研究新建农宅建筑采暖能耗现状和节能降耗策略,并利用DesignBuilder软件建立计算模型,根据当地农宅建筑特性选取了外墙构造、屋顶保温层材料、建筑层高、南向窗墙比、北向窗墙比等5个与采暖能耗相关的因素进行模拟优化分析。运用正交试验和极差分析,研究其对建筑能耗的影响趋势及显著性程度,最后得到新建农宅最佳优化方案为外墙选用250 mm厚EPS板层间浇筑混凝土外墙、屋顶保温层材料选用100 mm厚聚氨酯板、楼层高度选用3.2 m、南北窗墙比分别选择0.45和0.10,该组合单位面积采暖能耗为12.98 W/m^(2),对比实验建筑初始能耗节能率为40.81%。研究结果对于寒冷地区农宅节能设计及建造具有参考意义。

基于灰色关联分析的纵扭超声辅助对电火花微孔加工影响评价

TC4钛合金是航空航天领域经常加工的材料,由于其难切削的特点通常使用电火花进行加工,但存在加工效率与废屑排除的问题。纵扭超声振动可以有效优化如上弊端,但目前没有严谨定量的科学分析证明纵扭超声辅助对电火花加工的优化程度。因此提出纵扭超声辅助电火花放电能量模型,阐明放电机制以及放电能量的影响因素;设置单因素试验和正交试验,通过显著性T检验探索纵扭超声振动对电火花加工的影响程度,通过建立灰色关联分析模型分析电参数的影响权重并选出最优参数组,最后通过打孔试验验证了选优结果的正确性。研究结果表明:峰值电流和脉冲宽度对加工效率和质量的影响较为明显,引入纵扭超声振动明显改善了电火花加工性能,最优峰值电流从2 A提升至3 A,脉冲宽度从125μs提升至150μs,材料去除率提升了83.8%,相对电极损耗率、孔锥度和表面粗糙度分别降低了33.7%、22.3%和16.4%。

基于流场分析的降噪三通管及结构优化

三通管道是日常气体/液体管道使用的结构,流体经过三通管时形成复杂的流场从而产生噪声。采用计算机仿真模拟方法对三通管道内的流场进行分析,通过对三通管道的结构优化改变三通内流场状况,以降低流体经过三通处所产生的噪声,根据设计的正交实验找到最优参数。计算结果表明,改善后的三通结构相比普通三通管,在水流量为2.5L/s、1m测量点处的噪声降低了约14dB,降噪效果明显。