Inlet Diameter Research Articles

SIMULATION OF FLUID FLOW THROUGH A STAINLESS STEEL GLOBE VALVE USING ENGINEERING FLUID DYNAMICS

Globe valves are often used in many practical application of industry with the aim of controlling the fluid flow through the valve. Valve design ensuring an operation capacity plays an important role for engineers. This paper presents the design and simulation of fluid flow through the globe valve using CAD/CAE tools such as Autodesk CFD. Besides, design of experiment technique Box-Behnken is used to integrate the CFD simulation to identify the optimal design parameters of the globe valve. These parameters are inlet pressure, orifice diameter, and outlet clearance. The results showed that the optimal parameters are appropriate to improve the valve design to ensure the maximum fluid flow rate.

스크류원심펌프 임펠러 자오면형상 설계파라미터 최적화

Screw centrifugal pump is a non-clog type pump, which is widely used for drainage and sewage control systems. The screw centrifugal pump combines the advantages of the screw pump and centrifugal pump. Screw centrifugal pump shows the relatively high efficiency and the good solids handing capability. Based on a screw centrifugal pump design method, the parameters of impeller meridional plane shape are investigated for the improvement of pump performance. The design parameters of impeller meridional plane shape, such as impeller inlet and outlet diameters, outlet width, total axial length, blade inlet and outlet angles, and inclination angles, were investigated to examine their effects on the pump performance. Numerical analysis was conducted to determine the essential design variables for the screw centrifugal pump. Furthermore, flow passage shape optimization was conducted to enhance the performance of the screw centrifugal pump.

Оцінка характеристик закапотованого гвинтовентилятора ТРДД з надвисоким сту-пенем двоконтурності

In many respects, the efficiency and economy of the aircraft are determined by the parameters and characteristics of the power plant. The analysis of trends in the world engine building shows that an increase in the bypass ratio can significantly increase the efficiency of engines. One of the possible technical solutions to ensure the high performance of the perspective engines with an ultra-high bypass ratio is the use of a ducted propeller or propfan. This solution allows you to reduce acoustic radiation. In addition, the main advantage of the ducted propfans is a certain increase in thrust for the same consumed power. When flowing around a ducted propfan, a significant suction force arises on the nose of the profiled ring, the projection of which on the direction of movement provides a positive thrust of the ring. The presence of a duct also leads to a decrease in the final loss of the propeller, which, in turn, leads to an increase in the efficiency of the engine. Ducted and unducted propfans with the same blade row are investigated to assess the characteristics of a ducted propfan. The researches were carried out by the method of numerical experiment. The object of the research is a propfan with an inlet diameter of 2.924 m and the number of blades of 14 for a turbofan engine with a bypass ratio of m = 30. To research the propfan characteristics, a cruising mode of operation was selected in the range of revolutions n = 1500 ... 1650 rpm. with Mach numbers at the input from M = 0.54 to M = 0.8. In this work, the calculation did not take into account the resistance force of the duct. For a qualitative assessment of the flow in the propfan, visualization of the flow lines in the ducted and unducted propfan was obtained. The analysis of the research results showed that for all modes of operation the ducted propfan has a thrust force higher than the unducted propfan. The increase in thrust load reaches 71 ... 76 %. Visualization of the flow lines when flowing around a ducted and unducted propfan showed that the presence of a duct improves the internal aerodynamics of the propfan.

Numerical Simulation and Computational Flow Characterization Analyses of Centrifugal Pump Operating as Turbine

Using a pump in reverse mode as a hydraulic turbine remains an alternative for hydropower generation in meeting energy needs, especially for the provision of electricity to remote and rural settlements. The primary challenge with small hydroelectric systems is attributed to the high price of smaller size hydraulic turbines. A specific commercial pump model, with a flow rate of 12.5 m3/h, head 32 m, pressure side diameter of 50 mm, impeller out, and inlet diameters of 160 mm and 6 mm, respectively, was chosen for this research. This research aimed to investigate a pump’s flow characteristics as a turbine to help select a suitable pump to be used as a turbine for micro- or small hydropower construction. Numerical methodologies have been adopted to contribute to the thoughtful knowledge of pressure and velocity distribution in the pump turbine performance. In this study, the unsteady flow relations amongst the rotating impeller and stationary volute of the centrifugal pump made up four blades and four splitters. Intermittent simulation results of pressure and velocity flow characteristics were studied considering diverse impeller suction angles. The study was conducted by considering a wide range of rotational speeds starting from 750 rpm to 3250 rpm. From the results, it was found that PAT operation was improved when operated at low speeds compared to high-speed operation. Thus, speeds between 1500 rpm and 2000 rpm were suitable for PAT performance. This research helps to realize the unsteady flow physiognomies, which provide information for future research on PAT. This study makes useful facts available which could be helpful for the pump turbine development. Future studies should focus on cost analysis and emission generation in energy generation.

Investigation of the Jet Characteristics and Pulse Mechanism of Self-Excited Oscillating Pulsed Jet Nozzle

Self-excited oscillation pulse jet technology is widely used to clean sediment from oil storage tanks. Its successful application is dependent on jet performance. As the cleaning requirements of the oil industry increase, it is necessary to optimise the structure of self-excited oscillation pulsed jet nozzles (SOPJNs) to optimise cleaning and energy efficiencies. In this study, the jet performance of a SOPJN is modelled and analysed based on computational fluid dynamics with consideration of a large eddy simulation and homogeneous cavitation. The modelling results are highly consistent with experimental results. The effects of the SOPJN’s inlet diameter, cavity diameter, cavity length, wall reflection angle, and inlet pressure on the jet’s peak velocity, oscillation frequency, and cavitation number were analysed. The results show that the oscillation frequency decreases with the increase of the inlet diameter d1, cavity diameter D, cavity length L and reflection angle of wall α. Optimisation of the SOPJN inlet diameter, cavity length, and wall reflection angle produced a jet with a high peak velocity and strong cavitation. The optimal nozzle cavity diameter strengthens cavitation, while the peak velocity fluctuates as the cavity diameter increases. The peak velocity increases with the inlet pressure, while the increasing rate of the peak velocity decreases. The results of this study can be used in the design and optimisation of similar nozzle structures for improved pulse jet cleaning.

FLUID FLOW STUDY IN VARIOUS SHAPES AND SIZES OF HORIZONTAL AXIS SEA CURRENT TURBINE

The ducted tidal turbine models have been developed to utilize the conversion of the kinetic energy on ocean currents. The research in refining the turbine characteristics has been carried out by modifying the turbine’s shape and size. This study investigated flow characteristics in the meridional section of five ducted turbines models for seawater flow with velocity U0 = 1.5 m/s. The ducted turbine design and construction have five different impeller house diameters and fixed inlet and outlet diameters. The potential energy flow theory and experimental data are used to analyze the flow characteristics of the model. The results show that flow velocity in the x-direction at the inlet and outlet cross-section is getting smaller, reducing the impeller house cross section. Each impeller house size reduction increases the flow speed in the impeller house cross-section and also pressure on all other cross-sections tested. In the inlet area, the increased pressure indicates a decrease in speed flow and discharge coefficient value. The discharge coefficient value decreases from CQ = 0.9 at the diameter ratio of dr = 1 to CQ = 0.56 at the diameter ratio of dr = 0.375. The maximum value of power coefficient was determined at dr = 0,61÷0.73 or dr = 0.69 which is equivalent to average internal flow velocity Vr =2.0÷2.6 m/s and the static pressure ps = 97.1÷ 94.4 kPa. At the ratio value of D0/D2 = 0.83, the optimal diameter ratio dropt=0,61÷0.73 is in line with the duct model of case 3 and case 4, but it may be determined solely as for case 4.

Experimental study and numerical simulation of the kinetic energy recovery of the mine’s exhaust gas

ABSTRACT In mines, the exhaust gas is mainly discharged from main ventilators in free dissipation state. The effective recovery of its kinetic energy is lucrative from economical and technical standpoints. This study is focused on recovering the kinetic energy of the exhaust gas without deteriorating the main ventilator’s safe operation or increasing power dissipation. The related experiments and numerical simulations were performed for the conical diffusers with diffusing angles of 16° and inlet diameters of 220 and 320 mm, respectively. By examining the start-up and operation states of the wind turbines using inlet collectors with conical, circular arc, and cone-arc shapes, it was found that the wind speed at the inlet of the drainage tube exceeded 4 and 20 m/s at the minimal and maximal distances from the wind turbine, respectively. The wind speed at the overflow tube outlet was no less than 1.8 m/s, proving a certain recovery of kinetic energy by the wind turbine. Thus, the critical distance between the diffuser and the inlet collector should be at least four times the diffuser’s inlet diameter. Finally, the velocity, pressure, and flow fields in the vortex core regions of the kinetic recovery system with different types of inlet collectors were simulated with the FLUENT commercial software package. The simulation results revealed that the circular-arc collector outperformed other three tested configurations in kinetic energy recovery. Implications: This study is focused on recovering the kinetic energy of the exhaust gas without deteriorating the main ventilator’s safe operation or increasing power dissipation. China is a country with coal as its main energy source, which releases over ten billion cubic meters of the exhaust gas annually. In addition to low-concentration methane, there is also the exhaust gas released at a velocity of about 20 m/s, which kinetic energy recovery would be very lucrative. The significance of this study is that the mine’s main ventilator outlet was simplified as two conical diffusers with parameters α=16°/n=2 and α=16°/n=2.5, and the optimal critical distance between the diffuser and the collector was determined as 4Di , where Di was the diffuser’s inlet diameter. Under that optimal condition, the system can achieve the maximum power without affecting the ventilator’s normal operation. It is instructive to make full use of and manage the exhaust gas in mine that fits the journal on the purpose of air waste management. Finally, we provide a statement serious that the article is original and unpublished and is not being considered for publication elsewhere.

Neuromuscular ultrasound (NMUS) O-NU001. Feasibility of shear wave elastography and high definition color in evaluation of carpal tunnel syndrome

Introduction . Diagnosis of carpal tunnel syndrome (CTS) is based on clinical findings and electrodiagnostic tests (EDT). However, EDT has high false negative rates, and the results often do not reflect the severity of symptoms. The aim of this study is to investigate the value of shear wave elastography (SWE) and high definition (HD) color in diagnosis and evaluation of symptom severity in CTS. Methods . The study prospectively enrolled 39 wrists from 23 patients with EDT-confirmed CTS, 15 wrists from 12 patients who have CTS symptoms without EDT abnormality and 28 wrists from 14 healthy volunteers. Cross-sectional area (CSA) and longitudinal diameter of median nerve were measured. SWE of median nerve at the wrist and midforearm were performed, and the ratio between them was calculated. SWE of abductor pollicis brevis (APB) and abductor digiti minimi (ADM) were also measured and the ratio was obtained. HD color was conducted in the longitudinal plane at carpal tunnel. Results . The CSA of the median nerve at the carpal inlet and longitudinal diameter were significantly larger for the EDT-confirmed CTS group compared to control group (13.21[11.28,17.23] vs 7.98[6.53,8.94]; p < 0.001, 2.77[2.41,3.08] vs 2.07[1.79,2.24]; p < 0.001). It also had significantly higher median nerve elasticity ratio (2.59[1.77,4.09] vs 1.61[1.32,1.94]; p = 0.007). HD color showed significantly higher grades in the former group (p = 0.004). In ROC analysis, a 1.97 cut-off value on SWE ratio revealed sensitivity, specificity, PPV, NPV of 74.4%, 78.6%, 82.9%, 68.8%, respectively (AUC: 0.796[0.687,0.905]). Inter-rater reliability was excellent for SWE measurements (ICC: 0.908(0.761,0.967)). There was no significant correlation of CSA, elasticity and HD color grade with clinical symptom scores. In comparison between the group of CTS patients without EDT abnormality and control group, the former had significantly larger CSA in carpal inlet and elasticity ratio (9.61[7.21,11.55] vs 7.98[6.53,8.94]; p = 0.011, 2.59[0.94,4.65] vs 1.61[1.32,1.94]; p = 0.009). Conclusion . SWE and HD color are helpful supportive tools in diagnosing CTS, especially in patients who have typical CTS symptoms but normal results in EDT.

Effect of Geometrical Parameters on Extraction Efficiency of the Annular Centrifugal Contactor

The geometrical parameters of annular centrifugal contactors (ACCs) have an important influence on the extraction efficiency. The present work used a home-made 25 mm ACC constructed by 3D printing to investigate the effect of five geometrical parameters on the extraction efficiency. These parameters are annular width (d), clearance height (Hc), rotor inlet diameter (Din), bottom vane number (N), and the bottom vane’s bending direction (S). Central composite design was employed to design the experiment, and the response surface methodology was used to analyze the data. The results show that Hc and Din were positive for efficiency, while d and N were negative. When the bottom vane’s bending direction was the same as the liquid helical flow direction, the efficiency improved compared to the straight vane. It is found that 3 mm d, 5 mm Hc, 6 mm Din, and four clockwise covered vanes are the parameters where the efficiency reached the highest point of 94.5%. We analyzed the interactions between the parameters based on the coefficients of the quadratic equation, and the interactions were not considered in previous studies. This work surprisingly reveals that the effects of the parameters on the extraction efficiency were not independent, and there were interactions between the parameters. The interaction between the rotor inlet diameter and annular width was significant and could not be ignored. These results could serve as a reference for optimizing extraction processes and the design of ACCs.

Generation Mechanism of Broadband Whoosh Noise in an Automotive Turbocharger Centrifugal Compressor

Abstract The present study focuses on the acoustics of a turbocharger centrifugal compressor from a spark-ignition internal combustion engine. Whoosh noise is typically the primary concern for this type of compressor, which is loosely characterized by a broadband sound elevation in the 4–13 kHz range. To identify the generation mechanism of broadband whoosh noise, the present study combines three approaches: three-dimensional (3D) computational fluid dynamics (CFD) predictions, experiments, and modal decomposition of 3D CFD results. After establishing the accuracy of predictions, flow structures and time-resolved pressures are closely examined in the vicinity of the main blade leading edge. This reveals the presence of rotating instabilities that may interact with the rotor blades to generate noise. An azimuthal modal decomposition is performed on the predicted pressure field to determine the number of cells and the frequency content of these rotating instabilities. The strength of the rotating instabilities and the frequency range in which noise is generated as a consequence of the rotor-rotating instability interaction correspond well with the qualitative trend of the whoosh noise that is measured several duct diameters upstream of the rotor blades. The variation of the whoosh frequency range between low and high rotational speeds is interpreted through this analysis. It is also found that the whoosh noise primarily propagates along the duct as acoustic azimuthal modes. Hence, the inlet duct diameter, which governs the cut-off frequency for multi-dimensional acoustic modes, determines the lower frequency bound of the broadband noise.

Current Evidence about Developmental Dysplasia of the Hip in Pregnancy.

In adults, developmental dysplasia of the hip (DDH) represents a spectrum of disorders. It is commonly found in women in routine orthopedic practice. Hip dysplasia is a leading precursor of joint laxity; when untreated, it can contribute to chronic modifications, such as thickening of the pulvinar and ligamentum teres (which can also elongate), hypertrophy of the transverse acetabular ligament, and osteoarthritis. DDH is presumed to be associated with alterations in pelvic morphology that may affect vaginal birth by the reduction in the transverse diameter of the pelvic inlet or outlet. Here, we provide an overview of the current knowledge of pregnancy-associated DDH. We primarily focused on how a surgical DDH treatment might influence the pelvic shape and size and the effects on the mechanism of birth. We presented the female pelvis from the standpoint of bone and ligament morphology relative to a pelvic osteotomy. Then, we described whether the pregnancy was impacted by previous surgical DDH treatments, performed from infancy to adulthood. In conclusion, hip dysplasia is not associated with high-risk complications during pregnancy or with increased difficulty in vaginal delivery.

Simulation Of The Process Of Cavitation Treatment Of Liquid Feed

The same fractional composition and uniformity of distribution of raw material components of plant origin in the mixture are the main criteria for the liquid feed quality. This is ensured by the homogenisation and dispersion of feed components using cavitation treatment. The purpose of the study is to simulate the process of cavitation treatment of liquid feed with a rotary cavitation disperser-homogeniser and substantiate its rational design and technological parameters. The task is to create such a rotary cavitation disperser-homogeniser, which allows simultaneously performing technological processes of dispersion, emulsification, and homogenisation of mixture components in a liquid medium with higher productivity, quality, and lower energy consumption. As a result of modelling the action of a rotary cavitation disperser-homogeniser in the Star CCM+ software, the distributions and dynamics of velocities of the liquid phase of the mixture and the pressure and concentration of the gaseous phase of liquid in the diffuser are established, which indicates the presence of cavitation. This confirms the operability of the developed design and technological facilities for the preparation of liquid feed and indicates the expediency of further research to substantiate its technological parameters. As a result of numerical modelling of the operation process of a rotary cavitation disperser-homogeniser, the dependences of the maximum (max) and minimum (min) movement speed of the liquid phase of the mixture in the inlet Vin and in the diffuser Vrot on the rotor speed n, inlet diameter Din and the number of resonators Nhole are determined. The qualitative criterion for evaluating the cavitation phenomenon in the developed equipment is the maximum and minimum cavitation number Xmax and Xmin, which depends on the rotation speed of the rotor n, the inlet diameter Din and the number of resonators Nhole. The value of the cavitation number Xmin=0.08 and Xmax=0.57 is achieved at n=2725 rpm, Din=0.049 m, Nhole=48, which corresponds to a film flow of liquid with a stable separation of the cavitation cavity from the rest of the continuous flow (film cavitation)

Investigation of amplification process of heavy oil viscosity reduction device based on jet cavitation using lab experimental and numerical simulation method

ABSTRACT With the increasing requirement of global energy resources, researchers seek for new ways to deal with unconventional crude oil resources. Using the Computational Fluid Dynamics numerical simulation method, the standard k-ɛ turbulence model and the cavitation dynamics model are used to simulate the internal flow field of the 105t/a heavy oil viscosity reduction spray nozzle device which is designed by the jet cavitation theory. The jet cavitation intensity is evaluated by cavitation number and gas content. The influence of spray nozzle structural parameters such as inlet diameter, contraction length, expansion cone angle and expansion length on the cavitation effect of the spray nozzle are studied. The results show that the cavitation effect is the best when the inlet diameter, contraction section length, expansion section cone angle, and expansion section length of the large capacity device are 120 mm, 110 mm, 10°, and 150 mm, respectively. A laboratory test device with a processing capacity of 2000 t/a is built to conduct jet cavitation test on a batch of Saudi crude oil to obtain the change rate of crude oil viscosity, density and molecular weight. The numerical results are consistent with the outcome of laboratory experiments, and it is concluded that this spray nozzle can meet the needs of large processing capacity while ensuring a high cavitation rate.

Cop Enhancement of Vapour Compression Refrigeration System

This experimental investigation exemplifies the design and testing of diffuser at compressor inlet and nozzle at condenser outlet in vapour compression refrigeration system with the help of R134a refrigerant. The diffuser with divergence angle of 12°,14° and the nozzle with convergent angle 12°,14° are designed for same inlet and outlet diameters. Initially diffusers are tested at compressor inlet diffuser is used with inlet diameter equal to exit tube diameter of evaporator and outlet tube diameter is equal to suction tube diameter of the compressor. Diffuser helps to increases the pressure of the refrigerant before entering the compressor it will be helps to reduces the compression work and achieve higher performance of the vapour compression refrigeration system. Then nozzles are testing at condenser outlet, whereas nozzle inlet diameter equal to discharging tube diameter of condenser and outlet diameter equal to inlet diameter of expansion valve. Additional pressure drop in the nozzle helped to achieve higher performance of the vapour compression refrigeration system. The system is analyzes using the first and second laws of thermodynamics, to determine the refrigerating effect, the compressor work input, coefficient of performance (COP).

Cop Enhancement of Vapour Compression Refrigeration System

This experimental investigation exemplifies the design and testing of diffuser at compressor inlet and nozzle at condenser outlet in vapour compression refrigeration system with the help of R134a refrigerant. The diffuser with divergence angle of 12°,14° and the nozzle with convergent angle 12°,14° are designed for same inlet and outlet diameters. Initially diffusers are tested at compressor inlet diffuser is used with inlet diameter equal to exit tube diameter of evaporator and outlet tube diameter is equal to suction tube diameter of the compressor. Diffuser helps to increases the pressure of the refrigerant before entering the compressor it will be helps to reduces the compression work and achieve higher performance of the vapour compression refrigeration system. Then nozzles are testing at condenser outlet, whereas nozzle inlet diameter equal to discharging tube diameter of condenser and outlet diameter equal to inlet diameter of expansion valve. Additional pressure drop in the nozzle helped to achieve higher performance of the vapour compression refrigeration system. The system is analyzes using the first and second laws of thermodynamics, to determine the refrigerating effect, the compressor work input, coefficient of performance (COP).

Gas-solid Erosion Wear Characteristics of Two-phase Flow Tee Pipe

Particles erosion wear always consist in the intersection of tee pipe, which is an inevitable problem. In order to obtain the erosion wear characteristics of two-phase flow tee pipe, several cases of different inlet diameters are investigated numerically in this paper. Euler-Lagrange method is adopted to describe the gas-solid two-phase flow and the finite volume method is adopted to solve the erosion results. Meshing O-type grids to obtain the reasonable boundary layer in ICEM CFD. By verifying and comparing the turbulence intensity and velocity of the six meshes, a reasonable finite element model is selected. Intersection, the severest erosion region, is the location where the gas flow direction changes. The inlet diameter determines the region of the impact particles directly hitting the wall. When the inlet diameter is smaller, the erosion of the intersection is severer. As the inlet velocity increases, both the erosion of the intersection and the outlet pipe become severer. However, there are only the erosion scars at the intersection are affected, with the increase of particle mass flow.

Cop Enhancement of Vapour Compression Refrigeration System

This experimental investigation exemplifies the design and testing of diffuser at compressor inlet and nozzle at condenser outlet in vapour compression refrigeration system with the help of R134a refrigerant. The diffuser with divergence angle of 12°,14° and the nozzle with convergent angle 12°,14° are designed for same inlet and outlet diameters. Initially diffusers are tested at compressor inlet diffuser is used with inlet diameter equal to exit tube diameter of evaporator and outlet tube diameter is equal to suction tube diameter of the compressor. Diffuser helps to increases the pressure of the refrigerant before entering the compressor it will be helps to reduces the compression work and achieve higher performance of the vapour compression refrigeration system. Then nozzles are testing at condenser outlet, whereas nozzle inlet diameter equal to discharging tube diameter of condenser and outlet diameter equal to inlet diameter of expansion valve. Additional pressure drop in the nozzle helped to achieve higher performance of the vapour compression refrigeration system. The system is analyzes using the first and second laws of thermodynamics, to determine the refrigerating effect, the compressor work input, coefficient of performance (COP).

Constructal heat transfer and fluid flow enhancement optimization for cylindrical microcooling channels with variable cross‐section

AbstractThis study applies constructal theory to conduct a numerical optimization of three‐dimensional cylindrical microcooling channels with the solid structure subjected to internal heat generation. The cylindrical channels are designed as variable cross‐section configurations that experience conjugate heat transfer and fluid flow, where water is used as the coolant. The research aims to optimize the channel configurations subject to a fixed global solid material volume constraint. The key objectives are to minimize the global thermal resistance and friction factor. The coolant is pushed through the channels by pressure drop represented as Bejan number. The main design parameters are the inlet and outlet diameters at a given porosity. The channel configuration and the structure elemental volume are permitted to change to find the best design parameters that minimized thermal resistance and friction factor, so that the cooling effect is enhanced. An ANSYS FLUENT code is used to obtain the best optimal parameter of the configuration that enhances thermal performance. The influence of Bejan number on optimized inlet and outlet diameters led to minimization of thermal resistance and friction factor and maximization of Nusselt number. The results show distinctive optimal inlet and outlet diameters that enhance the overall performance of the system in the range of and , respectively.

Parametric Design Tool for Development of a Radial Guide Vane Cascade for a Variable Speed Francis Turbine

Hydropower as a part of the family of renewable energy sources represents an engineering and scientific field which inspires researchers to work on development of the systems and sub-systems in a way of optimizing the whole energy transformation process to obtain more efficient, flexible and reliable hydropower operation with the best possible water to energy ratio. This research is part of a Horizon 2020 HydroFlex project by the Norwegian University of Science and Technology (NTNU), where the main goal is development of a flexible hydropower generation. The guide vane cascade is one of the most crucial stationary sub-systems of the hydraulic turbine and is a subject of this study. Its re-design for obtaining a quality “flow-feeding” of a variable speed high head Francis turbine is developed. Having this goal in mind, a MATLAB code was generated, based on several key parameters, such as initial energy conditions as net head and turbine discharge at best efficiency point (BEP). Turbine runner geometrical constraints are taken into account during this process, while using recommendations for some initial guide vane calculations such as their number, inlet and outlet diameter, guide vane axis diameter, delivery angles etc. Using an inverse Euler turbine equation, the operating range of the turbine was calculated for a variable speed and discharge conditions, keeping the shock-free flow for all states at the runner’s inlet, as it is the most favourable inflow condition. For those operating points, the flow streamlines angles were obtained at the guide vanes leading and trailing edges. With an interpolating mathematical functions between the angles of the leading and trailing edges, the camber lines of the hydrofoils were obtained for further guide vane cascade geometry development. This algorithm can be implemented on any given runner geometry. The guide vane design is then exported into ANSYS Workbench for further numerical tests, such as CFD simulations for verifying the hydrodynamic characteristics and FEM analysis for verifying the structural integrity of this sub-system for variable speed operating conditions.

Real-Time Continuous Rapid Colorimetric Sensor for Gaseous Formaldehyde Determination by Increasing Gas-Liquid Reaction Rate

Formaldehyde can have detrimental health effects on humans. To reduce exposure to formaldehyde, several methods have been reported for gas-phase formaldehyde determination including chromatography, capillary electrophoresis electrochemical and so on. Among these methods, colorimetric sensor is a promising technique for its high sensitivity, selectivity, low cost and compactness. However, it usually takes tens of minutes for one measurement. In this paper, a real-time continuous rapid formaldehyde determination system based on colorimetric sensor was presented. Through the study of the relationship between inlet diameter of gas and its bubble size and reaction speed, the reaction time is reduced to 1/3 with an ability to detect formaldehyde concentrations as low as 0.02 ppm. The system can also measure the formaldehyde concentration continuously and automatically, which is vital for locating pollution sources.