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.

Modeling Approach and Analysis of the Structural Parameters of an Inductively Coupled Plasma Etcher Based on a Regression Orthogonal Design

The geometry of an inductively coupled plasma （ICP） etcher is usually considered to be an important factor for determining both plasma and process uniformity over a large wafer. During the past few decades, these parameters were determined by the ＂trial and error＂ method, resulting in wastes of time and funds. In this paper, a new approach of regression orthogonal design with plasma simulation experiments is proposed to investigate the sensitivity of the structural parameters on the uniformity of plasma characteristics. The tool for simulating plasma is CFD-ACE＋, which is commercial multi-physical modeling software that has been proven to be accurate for plasma simulation. The simulated experimental results are analyzed to get a regression equation on three structural parameters. Through this equation, engineers can compute the uniformity of the electron number density rapidly without modeling by CFD-ACE＋. An optimization performed at the end produces good results.

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.

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 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.

基于机-电-磁-流整体耦合的油阻尼断路器保护特性的容差设计

油阻尼断路器的主要特点是在电路发生短路、过载等情况时能够自动脱扣,断开电路,从而保护人员和设备的安全,常用于变电站等场所。文章在以往对油阻尼断路器油阻尼力、电磁铁静态特性、操作机构性能等研究的基础上,构建一个基于机-电-磁-流多体多自由度多场耦合的一体化虚拟样机整体耦合模型;接着对该整体耦合模型的保护特性进行了仿真与分析,通过仿真得到了不同电流倍数下动触头的分断特性,并通过实验验证了整体耦合模型和仿真结果的正确性;最后,为减小产品保护特性的分散程度,提高油阻尼断路器的稳定性,文中结合稳健容差设计技术,选取不同电流倍数下触头的断开时间作为目标函数,以极靴半径、细铁芯半径、粗铁芯半径、粗铁芯高度作为关键设计参数,通过正交试验和贡献率分析法对目标函数进行容差分配,使得触头断开时间的分散度比原来减少39.165%。研究成果将会对电器产品的研发提供理论指导。

正交实验法在水性木器清漆助剂选择中的应用

水性木器清漆的配方设计主要包括原材料选择及各组分比例确定两方面内容,如采用全面实验,则实验数目多、实验时间长、效率低。本论文基于探索性初配方进行助剂的正交实验,考察润湿剂、分散剂、消泡剂、成膜助剂和增稠剂的最佳种类搭配,然后采用正交实验考察上述助剂最佳用量搭配。通过实验数据分析,结合漆膜表观、光泽度和对比率等性能,获得漆膜无弊病、透明度较高的水性木器清漆配方。

火麻仁黄嘌呤氧化酶抑制肽的酶解制备工艺研究

为寻找开发火麻仁蛋白,提高火麻应用价值的最佳条件,以火麻蛋白为原料,通过酶解法制备火麻仁黄嘌呤氧化酶抑制肽,采用正交试验法优化中性蛋白酶酶解火麻蛋白制备多肽的最佳工艺条件。以中性蛋白酶用量、酶解时间、酶解温度进行单因素试验,通过正交试验分析获得制备火麻仁黄嘌呤氧化酶抑制肽的最佳酶解条件为pH值6.5,料液比1∶5,酶用量6000 U/g,酶解温度50℃,酶解时间5 h。在此条件下进行的验证试验中,多肽抑制率为78.98%,表明该工艺稳定、可行,具有较高的应用价值。

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.

Construction of column-orthogonal designs for computer experiments

Latin hypercube design and uniform design are two kinds of most popular space-filling designs for computer experiments. The fact that the run size equals the number of factor levels in a Latin hypercube design makes it difficult to be orthogonal. While for a uniform design, it usually has good space-filling properties, but does not necessarily have small or zero correlations between factors. In this paper, we construct a class of column-orthogonal and nearly column-orthogonal designs for computer experiments by rotating groups of factors of orthogonal arrays, which supplement the designs for computer experiments in terms of various run sizes and numbers of factor levels and are flexible in accommodating various combinations of factors with different numbers of levels. The resulting column-orthogonal designs not only have uniformly spaced levels for each factor but also have uncorrelated estimates of the linear effects in first order models. Further, they are 3-orthogonal if the corresponding orthogonal arrays have strength equal to or greater than three. Along with a large factor-to-run ratio, these newly constructed designs are economical and suitable for screening factors for physical experiments.

精密轴承用PEEK保持架结构及注塑工艺优化

针对原PEEK保持架兜孔无锁口,采用侧向抽芯机构进行注塑加工时外圆精度低的问题,将保持架兜孔分成内外两部分且设计为球面,注塑模具采用单分型面注塑模结构。并对注塑工艺浇口结构和浇口数量进行优化,基于正交试验得到最优工艺参数为模具温度180℃、熔体温度390℃、保压时间5 s和保压压力55 MPa。实际加工表明:外径面圆度不大于0.15 mm占86%;拉伸强度远高于65 MPa;200℃高温摩擦系数平均值为0.195,磨痕宽度平均值为0.9625 mm,磨损量平均值为0.1394 mm^(3);与相应公差等级套圈、球合套后,轴承旋转精度达到P4,振动值达到Z4。

富水混合花岗岩地层地铁隧道施工中地面注浆止水帷幕的设计参数优化

[目的]富水混合花岗岩地层新建隧道施工受地下水的影响显著,通常采用地面预注浆形成止水帷幕的措施来降低地下水对隧道施工过程的影响。但止水帷幕设计参数的选择大多以经验为主,可能存在隔水效果不佳、水位降低显著导致地层沉降超限,以及隧道周围突涌水等现象,故需要对富水混合花岗岩地层注浆帷幕设计参数进行优化。[方法]依托广州地铁18号线番禺广场站—南村万博站区间工程,基于正交试验设计,通过数值模拟分析了止水帷幕设计参数(帷幕深度、帷幕厚度、帷幕渗透系数及帷幕与隧道间距离)对注浆隔水效果的影响;采用SPSS软件进行多元线性回归分析,拟合了选取止水帷幕设计参数的经验公式,获取了止水帷幕最优设计参数并进行工程应用。[结果及结论]止水帷幕的影响因素按影响程度排序依次为:帷幕渗透系数、帷幕深度、帷幕厚度、帷幕与隧道间距离;现场选取的止水帷幕设计最优参数中,帷幕深度为58 m、帷幕厚度为2.0 m、帷幕渗透系数为1×10-10m/s、帷幕与隧道间距离为0.5 m。现场工程实践表明,采用最优参数后,止水帷幕降低地下水位效果较好,隧道开挖时的围岩稳定且开挖面干燥,地下水对隧道开挖的影响得以有效降低。

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。

大型土工离心机磁流体密封结构性能研究

大型土工离心机由于主轴轴径大、线速度高,使得现有磁流体密封结构很难满足安装、发热等要求。设计一种新型剖分式磁流体密封装置,利用有限元数值分析方法研究剖分式结构变形、极靴组件结构参数对密封性能的影响及密封装置温度分布,考虑实际加工能力,运用正交试验对结构参数进行优选。结果表明:结构参数对密封性能的影响程度由大到小依次为密封间隙、永磁铁高度、永磁铁宽度、槽宽、齿宽、齿高;优化后密封装置的各结构参数分别为密封间隙0.5 mm、齿宽2 mm、齿高2 mm、槽宽2.8 mm,永磁铁宽度11 mm、永磁铁高度22 mm;优化后的密封压力值为0.97 MPa,高于未优化前的0.54 MPa,同时高于工况要求的0.1 MPa;大轴径磁流体密封在工作时,存在轴套积热问题,需要在轴套部位开设冷却腔。

柴油机复式油气分离器设计与试验验证

设计了一款新型复式油气分离器,采用迷宫式结构作为粗滤组件、滤网作为精滤组件。设计开发了油气分离器部件性能试验台,通过正交试验设计方法设计多方案油气分离器,并基于部件试验台进行多方案性能试验测试。最终设计出满足要求的复式油气分离器,并通过整机试验验证其性能。结果表明,油气分离器综合性能影响因素由强到弱依次为滤网层数、滤网目数、过滤孔孔径、孔数、孔板间距。整机试验发现在300 L/min窜气量下分离效率达到了92.6%,压力损失小于3 kPa,满足发动机使用要求。

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。

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UPLC-MS/MS与G1-熵权法多指标综合评分优选微乐方提取工艺

目的建立同时测定微乐方水提物中6个指标性成分含量的方法,并优选微乐方的水提取工艺。方法采用超高效液相色谱串联质谱法(UPLC-MS/MS),Waters CORTECS C18色谱柱(2.1 mm×100 mm,1.6μm),以0.1%甲酸水-乙腈为流动相,梯度洗脱,流速0.25 mL/min,柱温40℃,进样量2μL,电喷雾负离子离子源,正负离子切换多反应监测(MRM)模式。以没食子酸、牡荆素、芍药苷、柚皮苷、橙皮苷、甘草酸含量和干膏率为评价指标,采用G1-熵权法确定各指标权重系数,以加水量、提取时间和提取次数为考察因素,通过正交试验确定提取工艺优化参数。结果微乐方水提物中6个成分在考察的浓度范围内线性关系良好(r>0.999),平均加样回收率为96.83%~102.56%,RSD<4.0%。最佳工艺参数为:饮片加12倍量水浸泡2 h,提取2次,每次1.5 h。结论本研究建立的UPLC-MS/MS同时测定微乐方中6个成分的方法快速、简便、灵敏度高,优选的提取工艺稳定可行,可为制剂开发提供依据。

补骨脂栓剂的制备及质量检查

目的:制备补骨脂栓剂、优选其处方及制备工艺。方法:以外观、融变时限为考察指标,用热熔法制备栓剂,在单因素实验基础上用正交设计实验进行处方筛选,考察制备基质比例、温度、增稠剂对栓剂的影响,并对制备的栓剂进行了质量检查。结果:优选出的处方是聚乙二醇6000、甘油、聚乙二醇400质量比为4∶3∶3,温度70℃,羟甲基纤维素钠为3%,按此处方制备的栓剂光滑,硬度适宜。结论:该处方设计合理,制备工艺可行,所得栓剂外观条件良好、融变时限符合要求。

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。