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.

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.

Effects of additives on performance of zinc electrode

In order to improve the properties of the nickel?zinc battery and study the effects of the additives on performance of zinc electrode, 3 levels and 4 factors (acetylene black, Bi2O3, PbO, Ca[Zn(OH)3]2·2H2O coated by La(OH)3 ) that affect the zinc electrode were tested with orthogonal design experiments. The charge?discharge experiments of zinc electrode made up of only zinc oxide were done in 20% KOH solution to investigate the function of the additive. In order to better understand the discharge capability attenuation of electrode, the ratios of zinc to calcium in the worst sample and the best sample of the orthogonal design test were analyzed. The samples were characterized by charge?discharge cycling, phase structure analysis, cyclic voltammetry and X-ray diffraction. Experimental evidences indicate that the optimum ratio of electrode additive is as follows: 0.02 g acetylene black, 0.5 g Bi2O3, 0.3 g PbO and 0.2 g Ca[Zn(OH)3]2·2H2O coated with La(OH)3 in 5 g sample.

Technology for Enzymolysis of Jellyfish Brain Protein by Bromelain

[Objective] This study aimed to investigate the optimal technology for en- zymolysis of jeUyfish brain protein by bromefain. [Method] Effects of enzymolysis temperature, the amount of added enzyme, solid/liquid ratio, enzymolysis time and pH on the enzymolysis of total protein were investigated through single factor ex- periments, and some technical parameters were optimized by orthogonal experi- ments. [Result] The results revealed that enzymolysis temperature of 55℃, the amount of added enzyme of 4 000 U/g, solid/liquid ratio of 1：4, the amount of added enzyme time for 5 h and pH 7 were the optimal combination of parameters for the enzymolysis; the average degree of hydrolysis obtained from the verification tests was 36.9%, indicating that the optimized results of the orthogonal experiment were credible. [Conclusion] This study provides the optimized conditions reliable theo- retical foundation and technical support for the exploitation and utilization of jellyfish resources as medicines or functional food in China.

Effect of Different Combined Treatments on Tomato Seedling Growth in High-temperature Season

The study on raising of strong tomato seedlings in high-temperature season is of great practical significance,because high-temperature condition in summer and autumn causes excessive growth of tomato seedlings easily. ‘Fenniya＇variety was selected as an experimental material,an orthogonal experiment was designed with rhizospheric temperature（ A）,light intensity（ B） and nutrient salt concentration（ C） as three factors which were designed with three levels,so as to study the effects of different treatments on root activity,strong seedling index,hypocotyl length and average internode length. The results showed that the most important factor for tomato seedling＇s root activity,hypocotyl length and internode length was nutrient salt concentration. In terms of effect on seedling index,substrate temperature should be reduced properly,to avoid excessive shading. It was primarily determined that the effects of three factors on the raising of strong tomato seedlings ranked as factor C,factor B and factor A from high to low; and the screened optimal seedling raising conditions were the rhizospheric temperature at（ 3 ＋ 1）℃,the shading rate of（ 50 ＋ 5） % and the EC value of（ 5. 0 ＋ 0. 5） mS/cm.

Effect of Rare Earth Elements on Structure and Electrochemical Properties of PuNi_3-type Hydrogen Storage Alloys

Structure and electrochemical properties of (La, Ce, Pr, Nd)_2MgNi_9 hydrogen storage alloys were investigated through orthogonal design experiments, and the alloys were obtained through induction melting followed by annealing treatment. The structure of main phase in alloys belongs to PuNi_3-type with a space group R3m. Rare earth elements, as a substitute of lanthanum, have a significant effect on phase structure of alloys, elements of cerium and neodymium are beneficial to the formation of Gd_2Co_7-type phase with a space group P 6_3/mmc. Rare earth elements can decrease the unit cell volume of main phase of alloys dramatically, and increase the axis ratio. The results of electrochemical experiment showed that the discharge capacity of alloy electrodes ranged from 342.97 to 380.68 mAh·g -1, and elements of cerium and neodymium can reduce the discharge capacity of alloy electrodes significantly. Compared to the electrode of La_2MgNi_9 alloy, the substitution of lanthanum by rare earth elements did not improve the cyclic stability of alloy electrodes due to the anisotropic structure change of unit cell. While rare-earth elements can improve the high rate dischargeability of alloy electrodes, the high rate dischargeability of alloy electrodes could reach the maximum when the unit cell volume of PuNi_3-type structure was about 0532 nm.

Improved uniformity of deposited metallic layer on hybrid micro/nano-structured Si substrates fabricated by two-step laser ablation for SERS application

Surface-enhanced Raman scattering(SERS) has been widely used as an effective technique for lowconcentration molecules detections in the past decades. This work proposes a rapid and accessible process to fabricate SERS-active substrates with high uniformity and controllability based on two-step laser ablation. Laser beams directly ablate the surface of Si, concurrently creating microstructures and ejecting molten materials caused by the thermal effect that nucleate in ambient air. The nuclei grow into nanoparticles and deposit over the surface. These nanoparticles,together with microstructures, improve the light collection efficiency of the SERS-active substrates. Especially after Au thin film deposition, these nanoparticles can provide nanogaps as hotspots for SERS. By orthogonal experiment design,laser processing parameters for better performances are determined. Compared with substrates fabricated by single 1064 nm master oscillator power amplifier(MOPA) laser ablation, substrates ablated by the primary 1064 nm MOPA laser and secondary UV pulsed laser show more uniform nanoparticles’ deposition over the surface. The optimized largearea substrate has a SERS detection limit of 10^(-8)mol/L for 4-aminothiophenol(4-ATP), indicating the potential realworld applications for trace detection.

Preparation of Poly (Phenylene Sulfide Amide) by Sulfur Solution Route

A new process for preparing poly(phenylene sulfide amide, PPSA), which is by reaction of sulfur instead of sodium sulfide as S source with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure (called sulfur solution route), is reported in the present paper. The influences of polymerization time, molar ratio of precursors, catalyst and solvent upon the polymer were investigated. To seek the best parameters of polymerization, orthogonal design was employed in the experiments. The results indicate that the molar ratio of precursors is the most significant effect on both of viscosity and yield of the polymer. The suitable parameters for preparing the related polymer are presented. The polymer was characterized by IRspectrum, 1HNMRspectrum and Raman spectrum, etc.

Numerical Analysis of Material Properties in Deformation of Near Hemispherical Shells

In this paper,the effects of hardening exponent,yield strength and elastic modulus on the deformability of near hemispherical shells are investigated by means of finite element method and orthogonal experiment design.The largest eccentric angle during the deformation process and thickness reduction after the deformation are introduced to estimate the deformability quantitatively according to the deformation characteristics of near hemispherical shells.The results indicate that the hardening exponent is the most influential parameter,followed by elastic modulus and yield strength.The shell exhibits good deformability when the hardening exponent and elastic modulus are in the range of 0.1-0.125 and 70-108 GPa,respectively.