Mass Flow Rate Distribution Research Articles

Aerodynamic analysis of an airborne wind turbine with three different aerofoil-based buoyant shells using steady RANS simulations

The manuscript investigates aerodynamic performance of an airborne wind turbine with varying shell configurations in an effort to elaborate the influence of shell aerodynamics on the performance of the buoyant airborne wind turbine for operating conditions at an altitude of 400 m above the sea level. A systematic study has been conducted on the three airborne duct shapes based on the NACA-5415, NACA-9415 and NACA-5425 cambered aerofoils by considering NREL Phase IV rotor and constant airborne shell throat diameter of 4.02 m. Three dimensional steady state simulations have been performed by employing k-ω SST turbulence model for a range of wind speeds10–25 m/s at zero angle of attack (the angle between wind direction and turbine rotational axis). The performance of the studied turbines have been analysed in terms of rotor thrust coefficient, duct thrust coefficient, turbine power coefficient, swallowed mass flow rate and pressure distribution along the shell. Results demonstrate that among all the considered shell configurations, the NACA-9415 shell based turbine demonstrated highest power coefficient. Increment in the both, aerofoil camber (5–9% of chord length) and thickness (15–25% of the chord length) resulted in 2.05 and 1.45 times higher turbine power coefficient respectively in comparison to the reference aerofoil (NACA-5415) shell based turbine.

Modeling and optimization of an enhanced battery thermal management system in electric vehicles

This paper models and optimizes an air-based battery thermal management system (BTMS) in a battery module with 36 battery lithium-ion cells. A design of experiments is performed to study the effects of three key parameters (i.e., mass flow rate of cooling air, heat flux from the battery cell to the cooling air, and passage spacing size) on the battery thermal performance. Three metrics are used to evaluate the BTMS thermal performance, including (i) the maximum temperature in the battery module, (ii) the temperature uniformity in the battery module, and (iii) the pressure drop. It is found that (i) increasing the total mass flow rate may result in a more non-uniform distribution of the passage mass flow rate among passages, and (ii) a large passage spacing size may worsen the temperature uniformity on the battery walls. Optimization is also performed to optimize the passage spacing size. Results show that the maximum temperature difference of the cooling air in passages is reduced from 23.9 to 2.1 K by 91.2%, and the maximum temperature difference among the battery cells is reduced from 25.7 to 6.4 K by 75.1%.

A Numerical Investigation of the Effect of Inlet Preswirl Ratio on Rotordynamic Characteristics of Labyrinth Seal

Full three-dimensional (3D) computational fluid dynamics (CFD) simulations are carried out using ANSYS cfx to obtain the detailed flow field and to estimate the rotordynamic coefficients of a labyrinth seal for various inlet swirl ratios. Flow fields in the labyrinth seal with the eccentricity of the rotor are observed in detail and the detailed mechanisms that increase the destabilizing forces at high inlet swirl ratios are discussed based on the fluid governing equations associated with the flow fields. By evaluating the contributions from each term of the governing equation to cross-coupled force, it is found that circumferential velocity and circumferential distribution of axial mass flow rate play key roles in generating cross-coupled forces. In the case that circumferential velocity is high and decreases along the axial direction, all contributions from each term are positive cross-coupled force. On the other hand, in the case that circumferential velocity is low and increases along the axial direction, one contribution is positive but the other is negative. Therefore, cross-coupled force can be negative in the local chamber depending on the balance even if circumferential velocity is positive. CFD predictions of cross-coupled stiffness coefficients and direct damping coefficients show better agreement with experimental results than a bulk flow model does by considering the force on the rotor in the inlet region. Cross-coupled stiffness coefficients derived from the force on the rotor in the seal section agree well with those of the bulk flow model.

Effects of gas liquid ratio on the atomization characteristics of gas-liquid swirl coaxial injectors

To understand the atomization characteristics and atomization mechanism of the gas-liquid swirl coaxial (GLSC) injector, a back-lighting photography technique has been employed to capture the instantaneous spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of gas liquid ratio (GLR) on the spray pattern, Sauter mean diameter (SMD), diameter-velocity distribution and mass flow rate distribution were analyzed and discussed. The results show that the atomization of the GLSC injector is dominated by the film breakup when the GLR is small, and violent gas-liquid interaction when the GLR is large enough. The film breakup dominated spray can be divided into gas acceleration region and film breakup region while the violent gas-liquid interaction dominated spray can be divided into the gas acceleration region, violent gas-liquid interaction region and big droplets breakup region. The atomization characteristics of the GLSC injector is significantly influenced by the GLR. From the point of atomization performance, the increase of GLR has positive effects. It decreases the global Sauter mean diameter (GSMD) and varies the SMD distribution from a hollow cone shape (GLR = 0) to an inverted V shape, and finally slanted N shape. However, from the point of spatial distribution, the increase of GLR has negative effects, because the mass flow rate distribution becomes more nonuniform.

Design and Analysis of CFD Experiments for the Development of Bulk-Flow Model for Staggered Labyrinth Seal

Nowadays, bulk-flow models are the most time-efficient approaches to estimate the rotor dynamic coefficients of labyrinth seals. Dealing with the one-control volume bulk-flow model developed by Iwatsubo and improved by Childs, the “leakage correlation” allows the leakage mass-flow rate to be estimated, which directly affects the calculation of the rotor dynamic coefficients. This paper aims at filling the lack of the numerical modelling for staggered labyrinth seals: a one-control volume bulk-flow model has been developed and, furthermore, a new leakage correlation has been defined using CFD analysis. Design and analysis of computer experiments have been performed to investigate the leakage mass-flow rate, static pressure, circumferential velocity, and temperature distribution along the seal cavities. Four design factors have been chosen, which are the geometry, pressure drop, inlet preswirl, and rotor peripheral speed. Finally, dynamic forces, estimated by the bulk-flow model, are compared with experimental measurements available in the literature.

Validating Spray Coverage Rate Using Liquid Mass on a Spray Card

Abstract. Validation of agricultural sprayers is important for quantifying as-applied coverage rates under field conditions. The complexity of modern sprayer control systems presents a challenge for precise field validation due to the use of nozzle control technologies, such as pulse width modulation, to meter chemical flow rates at individual nozzles. Non-uniform flow over time may result in local variations at high spatial resolutions that are ignored when estimating as-applied coverage rates across a field. The purpose of this study was to test several methods for estimating the mass of water applied to a water-sensitive paper spray card target using steady-state and instantaneous measurement techniques. The steady-state method consisted of a spray patternator table used to quantify the mass flow rate distribution across the nozzle width at varying nozzle pressures. The mass flow rate was then projected onto a two-dimensional area traveling across the spray width to calculate the mass of water that was deposited in the area. Two instantaneous sampling methods were used. The first method directly measured the mass of the spray card and water for 5 min after exposure to model the evaporation rate and solve for the initial mass at the time of exposure. The second method indirectly used the percent coverage of the exposed spray card by droplets. Results showed that the error between the calculated mass of water from the mass flow rate and the estimated initial mass of water from the evaporation rate varied between 2% and 8%. The relationships between the calculated and estimated initial mass of water methods and the spray card percent coverage were highly linear (R2 > 0.98). Both instantaneous methods produced results with higher variability between replications than the steady-state method, but the number of replications resulted in acceptably small differences between average mass measurements. These results show the potential for using evaporation rates for laboratory validation and percent coverage for laboratory or field validation of as-applied coverage rates. Keywords: Evaporation rate, Flow measurement, Precision agriculture, Sprayers, Water-sensitive paper.

The hybrid method applied to the plate-finned tube evaporator geometry

A procedure for the design and rating of plate-finned tube evaporator is proposed, to overcome limitations of both numerical and experiment based available present methods. The hybrid method allows to achieve high accuracy without incurring excessive computational cost and provides overall performance predictions starting from local analyses. The domain is divided into control volumes, where heat transfer is modeled by means of predictor equations obtained by known data. An iterative analytical method is used to find at each control volume the convergence between the heat transfer rates on both sides, and to obtain the distribution of wall temperature in the heat exchanger and the spatial distribution of the air mass flow rate. A case study is shown where in the first row the refrigerant completely evaporates, while this doesn't happen for the last one where the vapor quality at the outlet is 28% lower.

Interaction between a hollow‐cone spray and the co‐axial swirling stratified flow in a novel spray pyrolysis furnace

Pressure‐swirl nozzles producing hollow‐cone sprays are widely used in many engineering applications, but the induced high‐speed stream along the centreline of the spray cone was ignored in designing spray chambers. The high‐speed stream influences the flow field especially in minimized spray chambers, but it is difficult to characterize experimentally. Hence, computational fluid dynamics was applied to investigate the multi‐phase flow interactions inside a novel spray pyrolysis furnace for liquid ore exploitation. The mass flow rate distribution of the co‐axial swirling stratified flow inside the furnace, the gas‐solid separation efficiency, particle size distribution, and residence time were investigated under different positions and directions of the hollow‐cone spray. The results proved that different spray operations would cause variation in the air mass flow rate distribution and gas‐solid separation efficiency, which should be paid attention to in the design of process intensification. The distribution of particles sized from 30 to 40 μm were most sensitive under different flow rates. The recommended operating conditions of the spray pyrolysis process were confirmed as the inlet velocity of 5 m/s and downward spray from the top of the furnace chamber.

Aero-thermal coupled through-flow method for cooled turbines with new cooling model

The aero-thermal–coupled phenomenon is significant in modern cooled turbines, and an aero-thermal coupled through-flow method has previously been developed by the authors for considering the influence of heat transfer and coolant mixing in through-flow design. However, the original cooling model is not capable of calculating the distribution of the coolant mass flow rate and pressure loss in complex cooling structures. Therefore, in this paper, a one-dimensional flow calculation for the internal coolant is introduced into the heat transfer calculation to further improve the through-flow cooling model. Based on various empirical correlations, the cooling model can be used to simulate different cooling structures, such as ribbed channels and cooling holes. Three operating conditions were selected for verification of the NASA-C3X vane, which has 10 internal radial cooling channels. The calculated Nusselt number of internal cooling channels strongly agrees with the experimental data, and the predicted blade surface pressure and temperature distributions at mid span are also in good agreement with the experimental data. The convergence history of the meridional velocity and blade surface temperature demonstrates effective convergence properties. Therefore, the aero-thermal–coupled through-flow method with the new cooling model can provide a reliable tool for cooled turbine through-flow design and analysis.

CFD aided design of integrated spray pyrolysis furnace for liquid ore exploitation

Traditional spray pyrolysis of liquid ore includes the two processes of spray drying and calcination. A novel spray pyrolysis furnace was designed to integrate the two processes into one unit operation and separate solid particles from the furnace gas at the same time. Computational fluid dynamics was used to aid the design and investigate the flow pattern, which had the characteristic of co-axial swirling stratified flow. The mass flow rate distribution of the hot air was calculated under different boundary conditions and structural sizes to optimize the structure and flow field of the furnace. An injection model was built to simulate the hollow cone spray. The temperature and species distribution of the continuous phase, and the separation efficiency and residence time of the dispersed particles were obtained. Simulation results proved that the evaporation and pyrolysis process were divided in the upper and lower parts of the furnace chamber with continuous flow. The separation efficiency and mean residence time of the particle product was more than 95% and 6s, respectively. Preferred operation conditions and structure parameters are recommended for extensive application of spray pyrolysis of different liquid ores.

Experimental Research of Fuel Mass Flow Rate Distribution Effectiveness in Fuel Manifold on Engine Starting Performance

The component test results of fuel flow divider connecting fuel manifolds show that, when the starting fuel supply is given and the primary fuel manifold relative unfold pressure is at constant, the adjustment of the secondary fuel manifold turn-on pressure has effects on fuel flow through the primary fuel manifold and the time of fuel into the combustion chamber. The verification results of the secondary fuel manifold unfold pressure influence on engine starting performance shows that, when the secondary fuel manifold unfold pressure is low, the time of fuel into the combustion chamber is short, the engine starts fast; but because of rotation speed is low and engine inlet air flow is less, the gas temperature in staring phase is high. The test research results have important guidance and reference meaning for confirming the secondary fuel manifold unfolds pressure.

Effect of Rotation on a Gas Turbine Blade Internal Cooling System: Experimental Investigation

A detailed aerothermal characterization of an advanced leading edge (LE) cooling system has been performed by means of experimental measurements. Heat transfer coefficient distribution has been evaluated exploiting a steady-state technique using thermochromic liquid crystals (TLCs), while flow field has been investigated by means of particle image velocimetry (PIV). The geometry key features are the multiple impinging jets and the four rows of coolant extraction holes, and their mass flow rate distribution is representative of real engine working conditions. Tests have been performed in both static and rotating conditions, replicating a typical range of jet Reynolds number (Rej), from 10,000 to 40,000, and rotation number (Roj) up to 0.05. Different crossflow conditions (CR) have been used to simulate the three main blade regions (i.e., tip, mid, and hub). The aerothermal field turned out to be rather complex, but a good agreement between heat transfer coefficient and flow field measurement has been found. In particular, jet bending strongly depends on crossflow intensity, while rotation has a weak effect on both jet velocity core and area-averaged Nusselt number. Rotational effects increase for the lower crossflow tests. Heat transfer pattern shape has been found to be substantially Reynolds independent.

CFD analysis of WCLL BB PbLi manifold

ENEA CR Brasimone has developed the new design of the Water Cooled Lithium Lead Breeding Blanket (WCLL BB). In the new design Breeding Zone (BZ) water coolant flows in radial-toroidal direction, and PbLi flows in radial-poloidal direction; a gap between the Back Plate (BP) and the BZ constitutes the PbLi inlet manifold. The paper presents the CFD analysis of the WCLL BB PbLi inlet manifold, performed by ANSYS CFX-15 code. The objective of the analysis is to investigate the PbLi flow paths in the manifold region and to optimize the mass flow rate distribution in the BZ of the module. A preliminary analytical analysis is performed to evaluate pressure drop at orifices and to select the diameter of the orifices. CFD simulations are performed with the selected geometries. The optimal geometric configuration is a compromise between the need to have low PbLi velocity, to limit MHD issues and Eurofer corrosion, and to preserve the structural capability of the stiffening plates to withstand the overpressure conditions. Results demonstrate that the layout of the manifold and the size of the orifices is suitable to uniformly distribute the PbLi in the BZ, fulfilling the fluid velocity constraints. Specific MHD analyses are required to evaluate more realistic flow paths and to demonstrate the feasibility of the design.

A Predictive Model for Preliminary Gas Turbine Blade Cooling Analysis

The growing trend to achieve a higher turbine inlet temperature (TIT) in the modern gas turbine industry requires a more efficient and advanced cooling system design. Therefore, a complete study of heat transfer is necessary to predict the thermal loadings on the gas turbine vanes and blades. In the current work, a predictive model for the gas turbine blade cooling analysis has been developed. The model is capable of calculating the distribution of coolant mass flow rate (MFR) and metal temperatures of a turbine blade using the mass and energy balance equations at given external and internal boundary conditions. Initially, the performance of the model is validated by demonstrating its capability to predict the temperature distributions for a NASA E3 blade. The model is capable of predicting the temperature distributions with reasonable accuracy, especially on the suction side (SS). Later, this paper documents the overall analysis for the same blade profile but at different boundary conditions to demonstrate the flexibility of the model for other cases. Additionally, guidelines are provided to obtain external heat transfer coefficient (HTC) distributions for the highly turbulent mainstream.

Progress status of the ITER Vacuum Vessel sectors manufacturing design thermal hydraulic performance

The present work exposes the 3D steady state thermal hydraulic (TH) analysis of the Irregular Sector number 3 (IrS#3) of the ITER Vacuum Vessel (VV), including the Irregular Field Joints (IrFJ) by means of a commercial CFD (Computational Fluid Dynamics) code. The geometry of the IrS#3 has been simplified and healed in order to be suitable for CFD analysis. The simplified geometry has been meshed and converted to a polyhedral cell based mesh so as to enhance accuracy and calculation stability. Nuclear heat deposition (H) from the latest C Lite model [1] has been implemented through several User Defined Functions (UDF). Water coolant and stainless steel shell are solved together as a steady state conjugate heat transfer problem in order to assess the impact of the nuclear heat deposition on the IrS#3 cooling scheme. Hence, the IrS#3 is simulated as a whole, without splitting the domain.Results show the total IrS#3 pressure drop as well as the flow and temperature distribution all over the IrS#3. Moreover, the heat transfer coefficient (h) has been calculated at the fluid-solid interface. Velocity magnitude in the water coolant has an average value of 0.10m/s and mass flow rate distribution is 11% and 89% respectively for Inboard and Outboard. The pressure drop, mainly concentrated at inlet and outlet ducts, is of 77.4kPa. The average h is of 5 690W/(m2K), way above the design limit of 500W/(m2K). The fluid temperature stays at an average value of 101.7°C. The results obtained have a significant importance regarding design and safety and give a valuable insight on the current cooling scheme and system behavior for the IrS#3 of the ITER VV. This follows a previous work presenting the methodology and the results of a 3D TH analysis of the Irregular Sector number 2 (IrS#2) of the ITER Vacuum Vessel (VV) by means of CFD [2].

Identification of key liquid metal flow features in the physical conditioning of molten aluminium alloy with high shear processing

Although treating molten alloy with high shear processing (HSP) can dramatically refine the microstructure of solidified aluminium alloys, it was also recently employed as part of an effective route to purification of contaminated aluminium alloy scrap. The key mechanisms of HSP include the dispersion of large aluminium oxide films and clusters into very fine oxide particles by the high shear rate, and the redistribution of bulk melt by the agitation. These fine oxides act as nucleation sites for iron-based intermetallic phases, the formation of which is a pre-cursor to purification of the alloy. Macroscopic flow features of HSP, such as flow rate and shear rate, influence its performance significantly. Simulation based on Computational Fluid Dynamics was used to predict key features of fluid flow during HSP in a static direct chill (DC) caster. It was found that the distribution of shear rate and mass flow rate is highly nonuniform in the caster, and only in the close vicinity of the mixing head is there a relatively high level of shear rate and effective melt agitation. Therefore, effective dispersion of oxide films and clusters, and resulting significant nucleation of the intermetallics and/or primary aluminium phase, can only occur near the mixing head, and not throughout the whole crucible. Confidence in the model validity was built, by comparison with post-solidification microstructures in a previous experiment with similar process parameters and geometry.

Performance Analysis of an Air Cycle Heat Pump with a Turbocharger Driven by a Blower

Comparing with the common air cycle heat pumps using electrical machine as the prime mover, an air cycle heat pump with a turbocharger driven by a blower (ACHPTDB) could not only cuts down the initial cost, but also reach a balance between the heating capacity and heating load. The blower is chosen as the prime mover and the turbocharger takes place of the compressor and expansion valve/expander. A thermodynamic model for the ACHPTDB was built by using finite-time thermodynamics (FTT). The performance of the model was optimized associated with the air mass flow rate and subsequent distribution of pressure drops, which indicates the thermodynamic performance can reach its maximum by adjusting the air mass flow rate. It is also shown that heating COP has a maximum with respect to the blower pressure ratio or other parameters, which indicates there exists a tradeoff in how the mass flow rate and the blower pressure ratio should be allocated to make heating COP reach its optimization.

Application of ATHLET/DYN3D coupled codes system for fast liquid metal cooled reactor steady state simulation

In this paper the approaches used for developing of the BN-800 reactor test model and for validation of coupled neutron-physic and thermohydraulic calculations are described. Coupled codes ATHLET 3.0 (code for thermohydraulic calculations of reactor transients) and DYN3D (3-dimensional code of neutron kinetics) are used for calculations. The main calculation results of reactor steady state condition are provided. 3-D model used for neutron calculations was developed for start reactor BN-800 load. The homogeneous approach is used for description of reactor assemblies. Along with main simplifications, the main reactor BN-800 core zones are described (LEZ, MEZ, HEZ, MOX, blankets). The 3D neutron physics calculations were provided with 28-group library, which is based on estimated nuclear data ENDF/B-7.0. Neutron SCALE code was used for preparation of group constants. Nodalization hydraulic model has boundary conditions by coolant mass-flow rate for core inlet part, by pressure and enthalpy for core outlet part, which can be chosen depending on reactor state. Core inlet and outlet temperatures were chosen according to reactor nominal state. The coolant mass flow rate profiling through the core is based on reactor power distribution. The test thermohydraulic calculations made with using of developed model showed acceptable results in coolant mass flow rate distribution through the reactor core and in axial temperature and pressure distribution. The developed model will be upgraded in future for different transient analysis in metal-cooled fast reactors of BN type including reactivity transients (control rods withdrawal, stop of the main circulation pump, etc.).

A Method to Predict the Thickness of Poorly-Bonded Material Along Spray and Spray-Layer Boundaries in Cold Spray Deposition

Multi-traverse CS provides a unique means for the production of thick coatings and bulk materials from powders. However, the material along spray and spray-layer boundaries is often poorly bonded as it is laid by the leading and trailing peripheries of the spray that carry powder particles with insufficient kinetic energy. For the same reason, the splats in the very first layer deposited on the substrate may not be bonded well either. A mathematical spray model was developed based on an axisymmetric Gaussian mass flow rate distribution and a stepped deposition yield to predict the thickness of such poorly-bonded layers in multi-traverse CS deposition. The predicted thickness of poorly-bonded layers in a multi-traverse Cu coating falls in the range of experimental values. The model also predicts that the material that contains poorly bonded splats could exceed 20% of the total volume of the coating.

Numerical simulation of cell-to-cell performance variation within a syngas-fuelled planar solid oxide fuel cell stack

The cell-to-cell voltage variation in a planar solid oxide fuel cell (SOFC) stack is numerically investigated, considering the coupling effect of the heat transfer and uniform mass flow rate distribution between cells. The model integrates validated three-dimensional electro-chemical button cell sub-models with the structure of a real counter-flow planar SOFC stack. A uniform characteristic diagram is defined to analyse the variation of the cell voltage distribution in a planar SOFC stack. A quantitative index of uniformity is proposed to compare and explain the difference in the cell voltage distribution uniformity in planar SOFC stacks. The simulation results indicate that the distribution characteristics of the cell voltage within a planar SOFC stack are primarily determined by the combined effects of the mass flow rate distribution and temperature distribution. The mass flow rate distribution dominates the overall cell voltage distribution trend, and the temperature distribution mainly dominates the cell voltage distribution of the cell near the top and bottom of the stack due to the thermal effects. The simulation results also indicate the relative uniform cell voltage distribution in planar SOFC stacks in the case of using syngas as a fuel instead of hydrogen.