Internal Flow System Research Articles

Experimental Study of The Fan Turbine Performance in Oscillating Water Column with Airflow System in Venturi Directional

The Indonesian Ocean Energy Association has ratified the potential for ocean wave energy in Indonesia with a theoretical potential of 141,472 Megawatts. Unfortunately, this vast potential has not yet been utilized optimally in the Indonesian seas. Ocean wave energy technology has developed rapidly in various countries worldwide. One of the most famous ocean wave power generation technologies is the Oscillating Water Column (OWC), which utilizes airflow from ocean waves oscillating movement. Inspired by OWC, an innovative ocean wave power generation technology model was designed using a simpler fan turbine because it is directly integrated with an electric dynamo and an internal flow system in a venturi tube which can increase airspeed based on the concept of continuity theory. The experiment's results succeeded in creating up and down movements of ocean waves with a high tide of 15 cm and a low tide of 12 cm. Ocean wave oscillations can produce gusts of air with a speed of 1.56 m/s. The final result is obtained by model performance with an average turbine rotation speed of 42.191 rpm, an average electric voltage of 0.809 volts, and a more optimal turbine efficiency of 67.9%.

Robust bubble feature extraction in gas-liquid two-phase flow using object detection technique

ABSTRACT Identification of flow regime and feature extraction of bubble characteristics in gas-liquid two-phase flow systems have been significant issues in various engineering disciplines, including nuclear thermal-hydraulics field. In nuclear safety analysis codes, flow regime transition criteria and bubble size-dependent correlations are often utilized to obtain solutions for the governing equations. However, even today, they still rely on flow regime maps and empirical criteria that are based on visual observations and fully-developed flow conditions. In the present study, the AI-based object detection approach was adapted by utilizing convolutional neural networks to extract bubbly flow features. The model network is capable of extracting real-time bubbly flow features in an internal multiphase flow system. From the coordinate information of each individual detected bubbles, features such as void fraction, bubble number density, and average bubble sizes can be acquired instantly. The present approach has the potential to replace the traditional hand-coded image analysis method and open up a path for a fully automated and versatile two-phase flow feature extraction.

Combination of Low Fluctuation of Temperature with TiO2 Photocatalytic/Ozone for the Quality Maintenance of Postharvest Peach.

Chilling injury, tissue browning, and fungal infection are the major problems of peach fruit during post-harvest storage. In this study, a precise temperature control cold storage with low-temperature fluctuation (LFT) and internal circulation flow system is designed. An ozone (O3) generator and a (titanium dioxide) TiO2 photocatalytic reactor were applied to cold storage to investigate the variation of LFT combined with ozone fumigation and a TiO2 photocatalytic reactor in the efficiency of delaying ripening and maintaining peach fruit quality. Results showed that the temperature fluctuation with the improved control system was only ±0.1 to ±0.2 °C compared with that of ±0.5 to ±1.0 °C in conventional cold storage. LFT significantly reduced the chilling injury of peach fruit during storage. Although LFT combined with fumigation of 200 mg m−3 ozone periodical treatment slightly damaged the peach fruit after 40 d of storage, its combination with the TiO2 photocatalytic system significantly improved the postharvest storage quality of the fruit. This treatment maintained higher titratable acidity (TA), total soluble solids (TSS), better firmness, color, microstructure, and lower decay rate, polyphenol oxidase (PPO) activities, total phenol accumulation, respiratory intensity, ethylene production, and malondialdehyde (MDA) content during 60 d of storage. All the results show that LFT combined with the TiO2 photocatalytic system might be a promising technology for quality preservation in peach fruit storage.

CFRP 분진 회수를 위한 흡입모듈 및 블로어 성능평가

This study evaluated the operating point and the suction performance of the suction module for carbon fiber reinforced plastics (CFRP) dust removal under different drilling rotational speeds. A three-dimensional steady-state Reynolds-averaged Navier–Stokes (RANS) calculation with a shear stress transport (SST) turbulence model was conducted to investigate the internal flow characteristics and system resistance of the base model. Parts of the suction module exhibiting an unstable flow behavior were determined and their shape was modified for increased aerodynamic and suction performance. Prototypes of the base and the modified models were fabricated for measurement of the operating point and efficiency of the CFRP dust removal. Results confirmed the selection of appropriate blower specifications for the drilling system design of the modified suction module to achieve high efficiency and high suction.

A closed-form analytical model for predicting 3D boundary layer displacement thickness for the validation of viscous flow solvers

A closed-form analytical model is developed for estimating the 3D boundary-layer-displacement thickness of an internal flow system at the Sanal flow choking condition for adiabatic flows obeying the physics of compressible viscous fluids. At this unique condition the boundary-layer blockage induced fluid-throat choking and the adiabatic wall-friction persuaded flow choking occur at a single sonic-fluid-throat location. The beauty and novelty of this model is that without missing the flow physics we could predict the exact boundary-layer blockage of both 2D and 3D cases at the sonic-fluid-throat from the known values of the inlet Mach number, the adiabatic index of the gas and the inlet port diameter of the internal flow system. We found that the 3D blockage factor is 47.33 % lower than the 2D blockage factor with air as the working fluid. We concluded that the exact prediction of the boundary-layer-displacement thickness at the sonic-fluid-throat provides a means to correctly pinpoint the causes of errors of the viscous flow solvers. The methodology presented herein with state-of-the-art will play pivotal roles in future physical and biological sciences for a credible verification, calibration and validation of various viscous flow solvers for high-fidelity 2D/3D numerical simulations of real-world flows. Furthermore, our closed-form analytical model will be useful for the solid and hybrid rocket designers for the grain-port-geometry optimization of new generation single-stage-to-orbit dual-thrust-motors with the highest promising propellant loading density within the given envelope without manifestation of the Sanal flow choking leading to possible shock waves causing catastrophic failures.

Innovative Turbine Stator Well Design Using a Kriging-Assisted Optimization Method

At present, it is a common practice to expose engine components to main annulus air temperatures exceeding the thermal material limit in order to increase the overall engine performance and to minimize the engine specific fuel consumption. To prevent overheating of the materials and thus the reduction of component life, an internal flow system is required to cool and protect the critical engine parts. Previous studies have shown that the insertion of a deflector plate in turbine cavities leads to a more effective use of reduced cooling air, since the coolant is fed more effectively into the disk boundary layer. This paper describes a flexible design parameterization of an engine representative turbine stator well geometry with stationary deflector plate and its implementation within an automated design optimization process using automatic meshing and steady-state computational fluid dynamics (CFD). Special attention and effort is turned to the flexibility of the parameterization method in order to reduce the number of design variables to a minimum on the one hand, but increasing the design space flexibility and generality on the other. Finally, the optimized design is evaluated using a previously validated conjugate heat transfer method (by coupling a finite element analysis (FEA) to CFD) and compared against both the nonoptimized deflector design and a reference baseline design without a deflector plate.

Structural Deflection's Impact in Turbine Stator Well Heat Transfer

In the most evolved designs, it is common practice to expose engine components to main annulus air temperatures exceeding the thermal material limit in order to increase the overall performance and to minimize the engine-specific fuel consumption (SFC). To prevent overheating of the materials and thus the reduction of the component life, an internal flow system is required to cool the critical engine parts and to protect them. This paper shows a practical application and extension of the methodology developed during the five-year research program, main annulus gas path interaction (MAGPI). Extensive use was made of finite element analysis (FEA (solids)) and computational fluid dynamics (CFD (fluid)) modeling techniques to understand the thermomechanical behavior of a dedicated turbine stator well cavity rig, due to the interaction of cooling air supply with the main annulus. Previous work based on the same rig showed difficulties in matching predictions to thermocouple measurements near the rim seal gap. In this investigation, two different types of turbine stator well geometries were analyzed, where—in contrast to previous analyses—further use was made of the experimentally measured radial component displacements during hot running in the rig. The structural deflections were applied to the existing models to evaluate the impact inflow interactions and heat transfer. Additionally, to the already evaluated test cases without net ingestion, cases simulating engine deterioration with net ingestion were validated against the available test data, also taking into account cold and hot running seal clearances. 3D CFD simulations were conducted using the commercial solver fluent coupled to the in-house FEA tool SC03 to validate against available test data of the dedicated rig.

2D numerical study on flow boiling of zeotropic mixture isobutane/pentane in internal countercurrent flow system

Based on effective diffusion model and volume of fluid (VOF) model, the evaporation process of zeotropic mixture isobutane/pentane in an inclined straight flow channel is investigated. The physical properties of mixture and the source terms in the continuity, momentum, energy and species conservation equations are coded through User Defined Functions (UDF). The simulation results show that the evaporation rate first increases and then decreases from the entrance of vapor to the exit. The interaction of shearing force is relatively stronger at the top and bottom walls than that of near the interface. The velocity boundary layer is similar to the temperature boundary layer. The evaporation rate of pentane is higher than that of isobutane in the unit of kg/s because of its higher molecular weight. In addition, according to available experimental data, another physical model is built to validate the effective diffusion model. The mean absolute percentage error (MAPE) of heat transfer coefficient for all the four cases is 6.9%. This statistical indicator shows that the effective diffusion model proposed by Banerjee can reasonably describe the flow boiling of zeotropic mixture isobutane/pentane.

Experimental Study of Unsteady Flow in a Shock Tube for Needle-Free Drug Delivery

Recently, the needle-free delivery system has been widely used in medical fields due to its convenience in delivering drug particles into human body without any external needles. In order to penetrate through the outer layer of the skin, drug particles need to obtain enough momentum, which is achieved by accelerating drug particles in a Contoured Shock Tube (CST). The CST consists of a micro shock tube with two diaphragms and an expanded supersonic nozzle. In the present study, experimental studies were carried out by pressure measurement. Six high sensitive pressure transducers were used for recording pressure changes as the shock wave moved through different locations along walls in the test section. From which, data on shock wave propagation could be obtained. Different diaphragm pressure ratios were conducted to demonstrate effects of initial diaphragm pressure ratios on shock wave propagation. Shilieren visualization was also performed to observe shock wave propagation and shock wave structure in the present experimental shock tube model. The characteristic of the internal flow and shock wave system have been studied and analyzed in details in the present shock tube model.

Internal Flow and Axial Thrust Balancing of a Rocket Pump

Large axial thrust is produced on the rotor assembly of high-pressure rocket pumps. Thus, to ensure the reliability of bearings supporting the high rotational speed rotor, precise axial thrust balancing is essential. To realize complete axial thrust balancing, the back shroud of the main impeller is employed as the balance piston of a self-balancing type axial thrust balancing system in which the rotor assembly moves axially to compensate unbalance axial force. In this balancing system, which is often applied, complicated internal flow characteristics and pressure distributions are very important for predicting the precise characteristics of the axial thrust produced by the system. In the present study, a calculation method for analyzing the internal flow system taking into account effects of boundary layer conditions and angular momentum change in the impeller side-chambers is applied to the system combining the balance piston and grooves on the casing wall of the balance piston chamber. The analysis program is able to detect phenomena which could not be captured in past calculations and is effective for calculating internal flow characteristics much faster than possible with CFD analysis. A combination of balance piston and grooves on the casing wall of the balance piston chamber was confirmed to be suitable for extending the dynamic range of axial thrust balancing although installation of the grooves increased the leakage flow rate and friction torque at the same time.

J051042 ロケット用ポンプロ内部流路の動特性を考慮、した最適設計([J05104]流体機械の研究開発におけるEFD/CFD(4))

In the rocket turbopump, the balancing system with the balance piston is often applied to reduce the axial thrust. The leakage flow through the balance piston is affected by the configuration of the balance piston and the balancing point in the axial direction. In designing the internal flow system, the balancing point and flow rate have been estimated by the static analysis code of the internal flow. On the other hand, the analysis code for dynamic response of the internal flow through the balance piston was developed. In this study, optimal calculation considering the dynamic characteristics of the internal flow system was carried out by using the dynamic analysis code. As the results, the balancing point in the steady state significantly affects the leakage flow rate and the axial vibration.

J051041 ロケット用ポンプ内部流れの動特性解析([J05104]流体機械の研究開発におけるEFD/CFD(4))

Internal flow of a cryogenic rocket turbopump is rather complicated compared to ordinary pumps. In order to design stable axial thrust balancing system, dynamic analyses of the internal flow system is essential. In the present study, analysis program to analyze dynamic characteristics of leakage flow through the axial thrust balancing system was developed. In the program, structure of the balance piston type axial thrust balancing system and the internal flow passages are combined. Pressure perturbation was imposed on the inlet of the balancing system and the dynamic response of the axial thrust balancing system was evaluated. Calculated results showed that the system has resonant frequencies which depend on the fluids and the other parameters of the system.

Amperometric Determination of l-Lactate Based on Entrapment of Lactate Oxidase on a Transducer Surface with a Semi-Permeable Membrane Using a SIRE Technology Based Biosensor. Application: Tomato Paste and Baby Food

Determination of dissolved L-lactate in tomato paste and baby food samples using a SIRE-based (sensors based on injection of the recognition element) biosensor is reported. The measuring principle is based on the use of a small amount of enzyme, which is injected into an internal delivery flow system and held in direct spatial contact with the amperometric transducer by the use of a semipermeable membrane. Measurements are based upon the reversible enzymatic conversion of L-lactate to pyruvate and hydrogen peroxide by lactate oxidase. Differential measurements are performed in which the samples are measured in the presence and absence of enzyme allowing for control over matrix interferences present in crude samples. The linear range investigated for the determination of L-lactate in tomato paste and baby food was 0-0.1 mM using a lactate oxidase concentration of 22 U/mL. Samples were diluted with buffer prior to biosensor measurements. The L-lactate concentrations of the tomato paste and baby food were determined to be 1.02 +/- 0.02 mM and 2.51 +/- 0.10 mM, respectively, using the standard addition method. The repeatability for tomato paste and baby food measurements was 2.5% (RSD, n = 15) and 4.0% (RSD, n = 15) and the reproducibility was 13.0% (RSD, n = 45) and 3.0% (RSD, n = 45), respectively. The concentration of dissolved L-lactate can be used as a measure of freshness in the food industry. All biosensor measurements were compared with measurements from an established spectrophotometric assay (Boehringer Mannheim). It was found that the biosensor had good correlation with the spectrophotometric method. The biosensor gave 12% higher values for the tomato paste measurements and 2.5% higher values for the baby food measurements. However, a distinct advantage of the biosensor is that it can perform L-lactate measurements within 3 minutes, whereas the spectrophotometric assay requires a 35-minute measurement time.

A Comparison of Two Methods for Utilizing Steam Turbine Exhaust Hood Flow Field Data

This article describes the effects of two methods for representing the nonuniform distribution of flow properties across a steam turbine discharge annulus, on the hood loss coefficient. One method uses a mass-weighted integration of the property across the station, while the other is based on a mass-derived representative value of the property. The former has the potential for very high accuracy provided a sufficient number of points are integrated. The latter, while less accurate, is easier to apply and therefore more commonly used. The analytical modeling includes a simplistic step profile of pressure across the annulus, as well as a three-dimensional exhaust hood, flow-field simulation calculated using a Navier–Stokes code. Results show that significant errors can occur in the hood loss coefficient with the mass-derived approach. Although the analysis centers on hood loss coefficient as the performance parameter whose sensitivity is being monitored, the results highlight the pitfalls of improper application of measured data for any internal flow system.

Wall region turbulent flow under high mass fluxes over a flat plate

In mass transfer operations, the surface, past which the fluid moves has the additional property of acting as the source or sink of material for the flowing stream. The diffusing molecules carry momentum with them, which effects the original velocity distribution, which in turn effects the mass transfer process itself. The problem of mass-transpired boundary layers in turbulent flow has been analyzed with particular emphasis on the region in the immediate vicinity of the wall. The combined effect of the viscous and turbulent stresses has been taken into account. Theoretical results have been expressed in terms of the dimensionless velocity, U +, and eddy viscosity, ϵ/ν as a continuous function of the dimensionless distance parameter y +. It is observed that the effect of the turbulent stresses is substantial, particularly at high transpiration rates. It is also shown that substantial differences, mainly in the case of injection, exist between the momentum profiles of an external and internal flow system. It has been also concluded that the eddy diffusivity close to the wall varies with the cubic power of the distance measured from the wall under both low and high mass flux conditions.

On chemical reactions in internal flow systems

The basic equations for a non-isothermal homogeneous reaction in an internal flow system with a fully established velocity field are presented. It is shown that the specie concentrations can be found from a single function, i.e. the degree of advancement of the reaction, while the temperature is determined through a generalized enthalpy function which takes into account the thermal exchange with the exterior. Under mildly non-isothermal conditions, to which the analysis applies primarily, the determination of the two basic functions reduces to the solution of two linear parabolic equations and their associated Sturm-Liouville systems. An illustration of the analysis is given and a number of extensions are indicated.