High Hydraulic Performance Research Articles

On the design of manifolds for parallel channel systems

In the design of high-performance heat and mass transfer devices such as liquid-cooled heat sinks, catalytic reactors, and catalytic convertors, parallel mini/microchannels are favored owing to their special potentials. Offering low pressure drop, providing high transfer surface area to volume ratio, and being easy to manufacture and optimize have been drawing thermal and chemical engineers attention to parallel channels for past decades. When working with parallel channels, the challenge of flow maldistribution is commonly faced which decreases their efficiency significantly. System total pressure drop and flow uniformity are two parameters that determine the system performance. In the present study, a variety of practical ideas, aiming to enhance parallel channels performance, are studied numerically. Inventive manifold designs with high hydraulic performance are created through the course of this study. The results of these designs are compared with basic conventional designs which show substantial enhancement. Analyzing less successful designs lead us to deep understanding of fluid dynamics in parallel channel heat and mass transfer devices.

Numerical study of the influence of blade inlet design parameters on the internal flow characteristics and energy performance of a Francis turbine

One of the challenges of hydraulic turbine design is the creation of a conveyor with high hydraulic performance in accordance with the parameters of the hydraulic energy. The blade inlet parameters, such as blade beta angle, lean angle, and ellipse axis ratio, have an effect on the performance and cavitation characteristics of the runner, among the numerous geometric elements that regulate turbine performance. All of these parameters must be optimized to ensure that the runner inlet is matched to the guide vane under design conditions and a wider range of off-design conditions. For hydraulic designers, computational fluid dynamics based performance prediction methods can provide rapid turbine performance predictions and expedite runner development. Finding a collection of accessible parameters, meanwhile, strongly depends on the designer’s previous design work, which is frequently time-consuming. In this article, the internal flow characteristics and energy performance of a Francis turbine with moderate specific-speed, as well as the blade leading edge geometrical parameters that influence them, are investigated in depth. The Francis turbine is designed in accordance with the rated head H (m), rated flow rate Q (m), and rated speed n (rpm) within the constraints of the fixed meridional projection, including the leading-edge and trailing-edge positions. The energy performance, internal flow characteristics, velocity profile, flow angles, pressure distribution, blade loading, and cavitation characteristics are computed, analyzed, and compared. The main findings can serve as a guide for the development of Francis turbines with moderate specific-speed.

Discharge Coefficient of Symmetrical Stepped and Triangular Labyrinth Side Weirs in a Subcritical Flow Regime

The labyrinth side weir structure is an optimal solution to regulate and divert excess flows across rivers, and irrigation and drainage channels when the opening length of the side weir is limited. Changing the geometry of the side weir is considered one way to improve its efficiency. The present study investigates the hydraulic effects of stepped labyrinth side weirs to increase their discharge capacity. To estimate the outflow over symmetrical stepped labyrinth side weir, the discharge coefficient needs to be determined. Normal triangular labyrinth side weir in one cycle mode has been modified by increasing the crest path using different steps. A total of 417 experiments were conducted on normal and stepped side weirs for various weir opening lengths, weir heights, internal head angles, and hydraulic conditions. The results were analyzed and compared. It was found that efficiency improved, and the discharge coefficient increased as the number of the steps decreased. Furthermore, the water surface profile becomes more uniform with decreasing number of steps. A lower number of steps, smaller head angle, and high weir length produce a higher discharge coefficient by approximately 15%–35% compared to a normal triangular labyrinth side weir; in addition, the Knope length decreases by approximately 40%–70% for the same effective length. Additionally, a reliable equation to estimate the discharge coefficient of the stepped labyrinth side weir was presented. The results of this study can be used to design side weirs with high hydraulic performance when the weir-included angle selected is small or there is a lack of space.

Optimization design for an impeller of the multiphase rotodynamic pump handling gas-liquid two-phase flow

The multiphase rotodynamic pump is crucial for the multiphase blending transportation process. However, desigining such pump with high hydraulic performance and good blending transportation ability is quite challenging because of its unique structure. This study constructed a multi-objective optimization design system, which combines the 3D inverse design theory, response surface methodology, genetic algorithm, computational fluid dynamics simulation, and multi-objective optimization strategy, to improve the multiphase pump performance. Five optimization variables, namely the impeller loading parameters ( m1,S, m1,H, kS, kH) and the high-pressure edge angle ( θ), were selected in this study. Furthermore, two optimization objectives were considered at inlet gas void fraction ( IGVF) = 10%, namely the pump efficiency and the gas uniformity at the impeller outlet. The optimization results demonstrated that the pump efficiency and blending transportation ability would improve if the impeller blades had for-loaded loading distribution and the negative high-pressure edge angle. After optimization, the pump efficiency and the gas uniformity for the optimized impeller Opt1 improved by 2.6% and 18.2% at IGVF = 10%, respectively. Moreover, the internal flow pattern in the impeller was improved significantly, resulting in the maximum amplitude of pressure fluctuation in impeller Opt1 being 0.42 times that in the original test impeller.

Comparative Study of Nonsymmetrical Trapezoidal and Rectangular Piano Key Weirs with Varying Key Width Ratios

Rectangular piano key weirs (RPKW) have been introduced as an innovative type of labyrinth weir with a smaller footprint and high hydraulic performance. To date, limited attention has been paid to PKWs with other planforms. In this study, experiments and numerical simulations were conducted to investigate and compare the discharge capacity of unsymmetrical trapezoidal piano key weirs (TPKW) and classical rectangular PKWs with varying inlet/outlet key width ratios. Results indicate that, even if all other parameters are held constant, the discharge capacity of a trapezoidal PKW can still be further improved by up to 10% through optimizing the key width ratio. Relative to RPKWs, TPKWs were proven to be more efficient, especially for high relative heads because of the larger outlet cross section, and less efficient for low relative heads due to the relative lack of total crest length. For the specific geometric configurations considered in this study, the optimal range of key width ratio for TPKW and RPKW is likely to be within 1.30 to 1.57 and 1.50 to 1.77, respectively. At the end of this study, a new PKW configuration is introduced, which combines the advantages of both geometries (rectangular and trapezoidal) and improves the overall weir efficiency up to 8%.

Numerical study on the effects of installing an inducer on a pump in a turbopump

In a projectile, a turbopump is widely used to pressurize oxidizer and fuel to gain high thrust instead of using high pressure tank which has a disadvantage in total weight. Pumps in a turbopump employ an inducer upstream to prevent performance degradation by increasing pressure at the impeller inlet. However, cavitation and related instabilities take place frequently, so numerous analysis have been conducted for turbopumps. In this study, the pumps with and without an inducer were numerically studied using ANSYS CFX 13.0 to analyze the effects of installing an inducer, which was rarely treated before. By comparing these two pumps, the merits and demerits of installing an inducer can be analyzed in the aspects of hydraulic/suction performances and internal flow characteristics. Also, the role of an inducer can be understood in both of non-cavitating and cavitating conditions. As a result, head rise and efficiency of the pump were degraded by installing an inducer in non-cavitating conditions. The inducer could not play a role at high flow rate, and efficiency of the inducer was steeply declined in the off-design conditions. However, suction performance of the pump was greatly improved by adopting the inducer. Head of the pump with an inducer abruptly decreased at the low cavitation numbers, while head of the pump without an inducer started to decline gradually at the high cavitation numbers. In spite of high cavitation number, severe cavitation appeared in the case without an inducer, so it can be said that installing an inducer can prevent performance deterioration from the cavitation and satisfies stable operation which is more important for pumps rather than obtaining high hydraulic performance.

An integrated rotating biological contactor and membrane separation process for domestic wastewater treatment

Membrane fouling is a major bottleneck of almost all pressure-driven membrane filtration processes that limits their widespread applications. Improvement of hydrodynamics conditions is one of the most effective methods for membrane fouling control. This paper assesses a rotating biological contactor (RBC) integrated with membrane (RBC-MI) filtration that potentially offers inherent membrane fouling control as well as enhances biological performance, in which the membrane is placed inside the RBC bioreactor. Results show that the RBC-MI system achieves 84% of COD, 96.7% ammonium, 74% total nitrogen, 89% total phosphorus, and 96% turbidity removals. The integration of membrane placed inside the bioreactor doubles the permeability as compared to the external placement. Higher hydraulic performance is achieved at the low membrane-to-disk gap and higher disk rotational speed. The energy analysis shows that the RBC-MI consumes only 0.18 kWhm−3 signifying its viability as promission option to the energy-intensive conventional treatment systems.

Development of Hydrophilic PVDF Membrane Using Vapour Induced Phase Separation Method for Produced Water Treatment.

During the production of oil and gas, a large amount of oily wastewater is generated, which would pollute the environment if discharged without proper treatment. As one of the most promising treatment options, membrane material used for oily wastewater treatment should possess desirable properties of high hydraulic performance combined with high membrane fouling resistance. This project employs the vapor induced phase separation (VIPS) technique to develop a hydrophilic polyvinylidene fluoride (PVDF) membrane with polyethylene glycol (PEG) as an additive for produced water treatment. Results show that thanks to its slow nonsolvent intake, the VIPS method hinders additive leaching during the cast film immersion. The results also reveal that the exposure of the film to the open air before immersion greatly influences the structure of the developed membranes. By extending the exposure time from 0 to 30 min, the membrane morphology change from typical asymmetric with large macrovoids to the macrovoid-free porous symmetric membrane with a granular structure, which corresponds to 35% increment of steady-state permeability to 189 L·m−2h−1bar−1, while maintaining >90% of oil rejection. It was also found that more PEG content resides in the membrane matrix when the exposure time is extended, contributes to the elevation of surface hydrophilicity, which improves the membrane antifouling properties. Overall results demonstrate the potential of VIPS method for the fabrication of hydrophilic PVDF membrane by helping to preserve hydrophilic additive in the membrane matrices.

Optimum hydraulic design of cylindrical weirs

ABSTRACT Cylindrical weirs (CW) due to high hydraulic performance, economic, and ease in construction are highly regarded. In this study, the discharge coefficient () of this structure and its ability to flow energy dissipation were investigated. The results showed that in the range of the relative head (Ratio of the head of flow over the crest to the diameter of the weir: H/D) between 0.15 and 2.0, the varies between 1.0 and 1.4. In the same range of the H/D, such structures can dissipate the flow energy between 80% and 15%. The optimum value of the for economic design purposes is about 1.3, which occurs in the range of the H/D between 0.5 and 0.7.

Flow characteristics over asymmetric triangular labyrinth side weirs

Side weir is placed at the channel bank as a head regulator or a diversion device. Flow over a side weir has been the subject of many research studies considering its three dimensional and complicated characteristics. However, the labyrinth side weirs warrant further research due to their higher efficiency compared to linear side weirs. In this paper, subcritical flow characteristics and discharge coefficient for both symmetric and asymmetric triangular labyrinth side weirs were studied experimentally. The results show that asymmetric labyrinth side weirs have higher discharge coefficient compared to symmetric labyrinth side weirs; since a larger portion of the crest is orthogonal to the flow. Using the present laboratory data, general equations were proposed for the estimation of discharge coefficient of both symmetric and asymmetric triangular labyrinth side weirs. The results of this study can be useful to design side weirs with high hydraulic performance.

Investigating the effect of a parapet wall on the hydraulic performance of an arced piano key weir

ABSTRACT Piano key weirs (PKWs) are classified as broad-crested weirs offering a high hydraulic performance. In this experimental study, the hydraulic performance of PKWs (of curved plan-form) under different hydraulic and geometric conditions was studied. A total of 16 experimental models with four different arc radii (35, 49, 70 and 90 cm) and central angles (90°, 65°, 50°, 45°) with a parapet wall of 4.5 cm height were considered. The results showed that by increasing the angle of the curved plan-form, the hydraulic performance of the weir was further affected by the parapet wall. Moreover, the parapet wall increased the hydraulic performance by 10% at most. In addition, the arced PKW with a parapet wall increased the performance by 2.98 and 3.82 times compared to the arced sharp-crested weir and the linear sharp-crested weir, respectively.

Effects of blade thickness on hydraulic performance and structural dynamic characteristics of high-power coolant pump at overload condition

As an indispensable equipment in thermal power plants, the high-power coolant pump is necessary for high hydraulic performance with good structural safety for transferring of heat produced by fuels. However, the design of blade thickness for coolant pump especially at the off-design condition is still empirical and arbitrary. In the present work, the hydraulic performance, internal flow pattern, and structural response arising from the variations of blade thickness in coolant pump have been investigated using computational fluid dynamics and fluid–structure interaction methods. The numerical results have been verified by experimental performance and found to be good. To improve the accuracy of head calculation at the overload condition, a modified equation is proposed with the help of multi-island genetic algorithm and the average deviation is reduced from 58.50 to 1.59%. With the blade thickening process, the hydraulic performance is gradually deteriorated especially at the overload condition, and the flow behavior is changed with the proportion of high velocity near the pressure surface enlarging, the proportion of low velocity near the suction surface decreasing, and the pressure fluctuation intensity rising. Besides, increasing the blade thickness beyond 23.0 mm, the stress reduction is not effective. However, it helps to increase the natural frequency for suppressing the resonance. Finally, considering the optimal hydraulic and structural performances, the blade thickness is optimized to 23.0 mm.

The Use of Acid-Washed Iron/Aluminum Mixture in Permeable Reactive Barrier for the Elimination of Different Heavy Metal Ions From Water

In this experimental study, the performance of a fixed bed column containing a mixture of iron and aluminum modified with acid, as a reaction bed, was evaluated for the removal of heavy metals of cadmium, nickel, and copper. The tests were carried out by feeding the columns with aqueous solutions at the concentration of 100 mg/L using four iron/aluminum granular mixtures at various volume ratios (100/0, 50/50, 75/25, 25/75 and 0/100), and pH (3, 5, 7) for a total of 28 column tests. Results showed that metal ion removal was mainly accomplished via redox reactions that initiated the precipitation of mineral phases. At pH 5 and flow rate of 1 mL/min, the removal efficiency of cadmium, nickel, and copper at the 50/50 ratio of modified iron and aluminum was obtained higher than 99% and this removal efficiency could be kept about 50 hours. It seems that the column with the volume ratio of 75/25 of iron and aluminum mixture was the most efficient column for removing the heavy metals with the most suitable iron content and also high hydraulic performance due to the suitable aluminum content. It is therefore seen that the mixture of iron and aluminum can be used as an environmentally and economically viable remediation technology for the subsequent prevention of groundwater contamination.

Test study of the optimal design for hydraulic performance and treatment performance of free water surface flow constructed wetland

Orthogonal tests with mixed levels of design parameters of a free water surface flow constructed wetland were performed to assess their effect on hydraulic and treatment performance, and discover the relationship between the design parameters and the two performances. The results showed that water depth, plant spacing, and layout of in- and outlet mainly affected the two performances. Under 40cm depth, central pass of in- and outlet, 1.8m3/h flow rate, 20cm plant spacing, 2:1 aspect ratio, and Scripus tabernaemontani as the plant species, treatment performance of 5.3% TN, 6.1% TP and 15.6% TSS removal efficiencies and a high hydraulic performance of 0.854e, 0.602MI were achieved. There was no significant correlation between the design parameters and the two performances. The relationship among various hydraulic indicators and that among the purification indicators displayed extremely significant correlation. However, there was no significant correlation between hydraulic and treatment performance.

High hydraulic performance in horizontal waterwheels

Slow rotating waterwheels have been recently proposed as affordable sources of renewable energy in rural areas. In terms of hydraulic efficiency, classical horizontal waterwheels reach values on the order of 50%, being well below those obtained from overshot (71%), waterfall (66%) and, even, undershot (65%) vertical ones. Based on the study of an horizontal waterwheel built prior to 1940s that includes features from both elementary turbines and antique waterwheels, we conclude that horizontal waterwheels may actually reach hydraulic efficiencies as high as 81%. These quantitative results are obtained by analytical approximations and, more important, by numerical integrations through accurate computational fluid dynamics (CFD) simulations. In addition, we show that such a high hydraulic efficiency does not substantially vary when changing the net available head. We suggest that this relevant progress made on improving the efficiency of classical horizontal waterwheels may have implications in future designs of nano/micro hydropower devices.

高水力性能ミニターボポンプの開発研究 : インペラのスプリッタベーン方式とキャビテーション性能(OS13-4 流体機械に関連した内部複雑流動の解析と計測(ポンプ(1))

高水力性能ミニターボポンプの開発研究 : インペラのスプリッタベーン方式とキャビテーション性能(OS13-4 流体機械に関連した内部複雑流動の解析と計測(ポンプ(1))

Automation of border irrigation in South-East Australia: an overview

There exists a growing interest in automating border irrigation after a large number of irrigated farms in South East Australia have upgraded their layout design. Several manufacturing companies are producing automated equipment which rely on controllers fitted with timers or field water sensors to monitor the advance of the water front down the border (bay). Labor saving together with potential for increase in pasture yield and additional flexibility to perform other farming tasks are the main benefits considered by farmers who decide to adopt automation. Environmental benefits can also be realized provided that the system is properly managed. Correct sensor placement and timer setting are critical factors to achieve high hydraulic performance as they can influence the application efficiency of a typical border irrigation event by as much as 40%. Further efforts will be required in future to incorporate feedback control, improve operational reliability and adapt existing systems or develop new ones to meet the requirements of new irrigation techniques such as surge flow.

The synthesis of tooth profile shapes and helical gears of high hydraulic performance for rotary type pumps

In this work a method is presented for the synthesis of high hydraulic performance of non involute helical gears and tooth profiles. Two gear capacity criteria are used in the synthesis: (1) the capacity based on optimal helical advance equal to the circular pitch for which perturbations of delivery speed and torque can be completely eliminated and (2) the capacity based on optimal tooth profile which consists substantially in circular arcs whose centers fall on the pitch point, and whose connecting part consists of a suitable curve which satisfies the condition for continuous contact without intersection of two mating teeth surfaces. The present paper deals with the theoretical basis and the comparison with test results. The tooth profile recommended as a result of this study has permitted size and cost reduction in a currently manufactured line of pumps with delivery pressure to 20 kg/cm 2.

Research on Tooth Profile of Rotors for Gear Pumps of Rotary Type : 1st Report, Quasi-Semi-Elliptic Type-1

To eliminate the defects which are found in the conventionally developed tooth profiles, a new rack form has been obtained. Gear pumps having tooth profiles which are generated by or derived from the said rack are expected to have higher hydraulic performance. Analytical and geometrical interpretations are given ; furthermore comparison of the numerical values of delivery rate, specific slide of the said profile with those of the other conventional typical ones is shown. Experimental results are in good agreement with theoretical ones, but they are not shown here.