scholarly journals Study of the effect of baffles on longitudinal stability of partly filled fuel tanker semi-trailer using CFD

2021 ◽  
Vol 3 (SI2) ◽  
pp. SI13-SI23
Author(s):  
HUYNH PHUOC THIEN ◽  
Hong Duc Thong ◽  
Tran Minh Tai
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Stability Limit ◽  
Longitudinal Stability ◽  
Fluid Sloshing ◽  
Transient Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability ◽  
Different Levels ◽  
Simulation Scheme

Sloshing of liquid in partially filled fuel tanker vehicles has a strong effect on the directional stability and safety performance. Under the maneuver of the vehicle, such as steering, braking, or accelerating, the liquid fuel in the tanker tends to oscillate. As a result, hydrodynamic forces and moments raise. It leads to reduce the stability limit and the controllability of the vehicle. To minimize the effect of sloshing, the baffles are usually added to the tanker. This paper presents the study of the effect of baffles on the longitudinal stability of the fuel tanker semi-trailer using the computational fluid dynamics (CFD) approach. A three-dimensional fluid dynamic model of a typical tanker with different baffle configurations is developed. The User Defined Function (UDF) is used to control the acceleration of the tanker according to the simulation scheme. Transient simulations are performed for the cases of constant acceleration longitudinal maneuvers with different levels of fuel in the tanker. The volume of fluid (VOF) and air obtained from the simulation is used to indirectly calculate the center of gravity of the tanker. The post-processing results show that the baffles could provide resistance to the fluid sloshing, resulting in an improvement of the longitudinal stability of the tanker semi-trailer. The results also prove that the benefit of the baffle to the fuel tanker vehicle’s stability depends on the size of the baffle, as well as the number of baffles. The 40% height three baffles model is the proper baffle model to resist the longitudinal sloshing in the partially filled tanker of the studied trailer. By adding baffles, shifting of load on the kingpin and the rear axis are less than 5% and 2% as the tanker is filled with 50% and 70% fluid level respectively.

Numerical and Experimental Investigation of the CeCOST Swirl Burner

2018 ◽  
Author(s):  
Erdzan Hodzic ◽  
Senbin Yu ◽  
Arman Ahamed Subash ◽  
Xin Liu ◽  
Xiao Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Combustion Process ◽  
Stability Limit ◽  
Swirl Burner ◽  
Current Configuration ◽  
Stable Case ◽  
Eddy Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

Clean technology has become a key feature due to increasing environmental concerns. Swirling flows, being directly associated with combustion performance and hence minimized pollutant formation, are encountered in most propulsion and power-generation combustion devices. In this study, the development process of the conceptual swirl burner developed at the Swedish National Centre for Combustion and Technology (CeCOST), is presented. Utilizing extensive computational fluid dynamics (CFD) analysis, both the lead time and cost in manufacturing of the different burner parts were significantly reduced. The performance maps bounded by the flashback and blow-off limits for the current configuration were obtained and studied in detail using advanced experimental measurements and numerical simulations. Utilizing high speed OH-chemiluminescence, OH/CH2O-PLIF and Large Eddy Simulation (LES), details of the combustion process and flame-flow interaction are presented. The main focus is on three different cases, a stable case, a case close to blow-off and flashback condition. We show the influence of the flame on the core flow and how an increase in swirl may extend the stability limit of the anchored flame in swirling flow burners.

Criteria for the Stability Limit Prediction of High Speed Centrifugal Compressors With Vaneless Diffuser: Part II — The Development of Prediction Criteria

2020 ◽  
Author(s):  
Carlo Cravero ◽  
Davide Marsano
Keyword(s):  
High Speed ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Stability Limit ◽  
Design Phase ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
The Stability ◽  
Computational Resources

Abstract The challenge to be able to predict the stability limit in high speed centrifugal compressor is particularly strategic in an initial design phase. Furthermore, to be able to predict the limit massflow rate through the use of simplified numerical models (which does not require excessive computational resources) is very important. In the literature there are several methods to predict the chocking condition, while there is a lack as regards the surge condition. The authors have already presented a criterion to predict the surge line valid for centrifugal compressors with vaned diffuser. Instead those with vaneless diffuser have a very different behavior. For this reason, in the first paper an in-depth fluid dynamic analysis has been carried out, in order to identify the main phenomena linked to the trigger of instability in this type of compressors. This analysis has allowed understanding that the rotational speed is a discriminating factor in the phenomenology. In this second part, using the previous information, different criteria to predict the limit massflow rate for centrifugal compressors with vaneless diffuser are described. All the criteria are based on different simplified CFD approaches that can be routinely used during the design phase.

Fluid Dynamic Excitation of Centrifugal Compressor Rotor Vibrations

1978 ◽  
Vol 100 (1) ◽  
pp. 73-78
Author(s):  
W. E. Thompson
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Experience ◽  
Orbital Stability ◽  
Dynamic Force ◽  
Force Coefficient ◽  
Streamline Curvature ◽  
Compressor Rotor ◽  
Pressure Distributions ◽  
The Stability

A mechanism by which compressor rotor lateral vibration perturbs the mass flow-rate, the velocity and the pressure distributions within impeller passages is postulated. Such a perturbation will develop an unbalanced force on the rotor which, if it enhances the rotor vibration, is termed self-exciting. The concepts of rotor orbital velocity, the virtual center of shaft rotation, the reduction of unsteady flow to quasi-steady flow, the fluid dynamic force coefficient, mechanical orbital stability and the stability increment are introduced. The ideas are imposed on the streamline curvature method of quasi-three dimensional analysis of passage flow and a computer program has been assembled to carry out computation. No generalized guidelines have been found as yet but rather individual passage calculations are needed to determine the potentially exciting or damping character of the induced fluid dynamic forces. The average stability increment per stage for nine industrial multistage centrifugal compressors has been determined and compared with known operating experience. Important engineering characteristics of two of the compressors are shown in an example of the analysis. A provisional limit of the stability increment per stage ⩽ 1.85 lbf-s/in. (323.9N-s/m) is suggested, below which unstable nonsynchronous vibration of the compressor rotor can be expected.

Rotordynamic Force Prediction of Whirling Centrifugal Impeller Shroud Passages Using Computational Fluid Dynamic Techniques

1999 ◽  
Author(s):  
J. Jeffrey Moore ◽  
Alan B. Palazzolo
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Centrifugal Impeller ◽  
Pump Impeller ◽  
Dynamic Techniques ◽  
Computational Fluid Dynamics Cfd ◽  
Steady Solutions ◽  
And Performance ◽  
Rotordynamic Forces ◽  
Frequency Ratios

The demand for higher efficiencies and performance of modern centrifugal turbomachinery requires improved knowledge of critical design factors in strength of materials, aerodynamics, and rotordynamics. While tremendous strides in finite element stress analysis and computational fluid dynamics (CFD) have addressed the first two areas, the lack of accurate prediction tools for centrifugal impellers typically leaves rotordynamics out of the design loop. While several authors have analyzed the rotordynamic forces arising from shrouded centrifugal impellers, there has been no study to couple the secondary shroud passage with the three-dimensional primary flow model. The strong interaction between these domains makes this approach advantageous. The current study utilizes CFD techniques to analyze the full 3D viscous, primary/secondary flow field in a centrifugal pump impeller to determine rotordynamic forces. Multiple quasi-steady solutions of an eccentric, 3D model at different precessional frequency ratios yield the rotordynamic impedance forces. Performing a second order, least-squares analysis generates the skew-symmetric stiffness, damping, and mass matrices. The results show good correlation with experiment for both performance and rotordynamic forces.

scholarly journals Numerical validation of an analytical seal flutter model

2021 ◽  
Vol 5 ◽  
pp. 191-201
Author(s):  
Michele Greco ◽  
Roque Corral
Keyword(s):  
Analytical Model ◽  
Fluid Dynamic ◽  
Stability Limit ◽  
Labyrinth Seal ◽  
Analytical Models ◽  
Mode Shapes ◽  
Labyrinth Seals ◽  
Low Frequencies ◽  
Wide Range ◽  
The Stability

An analytical model to describe the flutter onset of straight-through labyrinth seals has been numerically validated using a frequency domain linearized Navier-Stokes solver. A comprehensive set of simulations has been conducted to assess the stability criterion of the analytical model originally derived by Corral and Vega (2018), “Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models - Part I: Theoretical Support,” ASME J. Turbomach., 140 (12), pp. 121006. The accuracy of the model has been assessed by using a simplified geometry consisting of a two-fin straight-through labyrinth seal with identical gaps. The effective gaps and the kinetic energy carried over are retained and their effects on stability are evaluated. It turns out that is important to inform the model with the correct values of both parameters to allow a proper comparison with the numerical simulations. Moreover, the non-isentropic perturbations included in the formulations are observed in the simulations at relatively low frequencies whose characteristic time is of the same order as the discharge time of the seal. This effect is responsible for the bending of the stability limit in the <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>0</mml:mn><mml:mi>t</mml:mi><mml:mi>h</mml:mi></mml:math></inline-formula> ND stability map obtained both in the model and the simulations. It turns out that the analytical model can predict accurately the stability of the seal in a wide range of pressure ratios, vibration mode-shapes, and frequencies provided that this is informed with the fluid dynamic gaps and the energy carried over to the downstream fin from a steady RANS simulation. The numerical calculations show for the first time that the model can be used to predict accurately not only the trends of the work-per-cycle of the seal but also quantitative results.

Linear Stability Analysis of LPT Rotor Packets: Part II — Three-Dimensional Results and Mistuning Effects

2004 ◽  
Author(s):  
Roque Corral ◽  
Juan Manuel Gallardo ◽  
Carlos Vasco
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Stability Limit ◽  
Mode Shapes ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Reduced Frequency ◽  
Stability Maps ◽  
The Stability ◽  
The One

Part II of this paper compares the aerodynamic damping of a modern Low Pressure Turbine (LPT) interlock bladed-disc to the one obtained when the blades are welded in pairs through the lateral face of the shroud. The damping is computed using the linearized Reynolds averaged Navier-Stokes equations on a moving grid. It is concluded that the increase in stability of the welded-pair with respect the cantilever configuration due to the modification of the mode-shapes, is smaller than the one due to the overall raise of the reduced frequencies of a bladed-disc with an interlock design. The modification of the flutter boundaries due to mistuning effects is taken into account using the reduced order model known as the Fundamental Mistuning Model (FMM). It is shown that the modification on the stability limit of a interlock bladed-disc is negligible, while for a welded-pair configuration an increase of 0.15% on the critical damping may be expected. Two realistic welded-pair bladed-discs are analysed in this work. It is shown that both are aerodynamically unstable, which is in agreement with the experimental observations. Critical reduced frequency stability maps accounting for mistuning effects are derived for both, freestanding and welded in pairs airfoils. The airfoils are assumed to be identical and mechanically uncoupled. The stabilizing effect of mistuning is also retained in these maps.

The Effect of Time-Varying Wind Direction on the Indoor Climate of a Naturally Ventilated Greenhouse

2010 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Wind Direction ◽  
Three Dimensional ◽  
Time Varying ◽  
Two Dimensional ◽  
Indoor Climate ◽  
Transient Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level ◽  
Transient Wind

This paper presents a numerical investigation into the indoor climate of a four span naturally ventilated, four span greenhouse subject to a time-varying wind direction. The effect of transient wind conditions on the temperature and velocity distribution inside the greenhouse is numerically determined using Computational Fluid Dynamics (CFD). The research in this paper is an extension of work previously conducted on two-dimensional models of greenhouses. Current work concentrates on the three-dimensional effect of external winds. Results indicate that for a wind direction of 22.5 degrees, the microclimate at plant level varies throughout the length of the greenhouse. It was also found from transient simulations that even a slight change in wind direction have a pronounced effect on the indoor climate at plant level.

3-D Computational Fluid Dynamic Analysis of Bustle Gas Combustion in a Direct Reduced Iron Plant

2007 ◽  
Author(s):  
William Walker ◽  
Ali Farhadi ◽  
George Tsvik ◽  
Tom Roesel ◽  
Naresh K. Selvarasu ◽  
...  
Keyword(s):  
High Temperature ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Pure Oxygen ◽  
Computational Fluid Dynamic Analysis ◽  
Gas Combustion ◽  
Flow Rates ◽  
Direct Reduced Iron ◽  
Computational Fluid Dynamics Cfd ◽  
Reducing Gases

Gases from a natural gas reformer are used to reduce iron oxides to iron in the direct reduced iron (DRI) plant. The reducing gases consist of mainly hydrogen and carbon monoxide and traces of methane, water vapor, carbon dioxide and nitrogen. Part of this gas mixture is burned to heat the gases to 1000°C (1832°F) by the injection of pure oxygen through an Inconel nozzle. The oxygen nozzle fails frequently, mainly due to the high temperature reactions. This paper aims to study the reactions that contribute to the high temperature for different oxygen flow rates and thus optimize the flow rates to prevent failure of the nozzle using a three dimensional (3D) computational fluid dynamics (CFD) model.

Enhancement of Centrifugal Compressor Operating Range by Control of Inlet Recirculation With Inlet Fins

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Hideaki Tamaki ◽  
Masaru Unno ◽  
Ryuuta Tanaka ◽  
Satoshi Yamaguchi ◽  
Yohei Ishizu
Keyword(s):  
Centrifugal Compressor ◽  
Stability Limit ◽  
Great Promise ◽  
Low Speed ◽  
Operating Range ◽  
Surge Margin ◽  
Compressor Inlet ◽  
Qualitative Effect ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

The operating points of a turbocharger compressor tend to approach or cross its surge line while an engine is accelerating, particularly under low-engine speed conditions, hence the need for an acceptable surge margin under low compressor-speed conditions. A method shifting the stability limit on a compressor low-speed line toward a lower flow rate is expected and inlet recirculation is often observed in a centrifugal compressor with a vaneless diffuser near a surge and under a low compressor-speed condition. First, examples of inlet recirculation were introduced in this paper, whereupon the effect of inlet recirculation on compressor characteristic was discussed by 1D consideration and the potential shown for growth of inlet recirculation to destabilize compressor operations. Accordingly, this study focused on suppressing the effect of inlet recirculation on compressor characteristics using small fins mounted in a compressor-inlet pipe, and examining whether they enhance the compressor operating range under low-speed conditions. Small fins are known as inlet fins in this paper. According to test results, they showed great promise in enhancing the compressor operating range during inlet recirculation. Besides, attempts were also made to investigate the qualitative effect of inlet fins on flow fields using computational fluid dynamics (CFD) and the disadvantages of inlet fins were also discussed.

scholarly journals Auxetic two-dimensional lattices with Poisson's ratio arbitrarily close to −1

2014 ◽  
Vol 470 (2172) ◽  
pp. 20140538 ◽  
Author(s):  
Luigi Cabras ◽  
Michele Brun
Keyword(s):  
Poisson’S Ratio ◽  
Effective Properties ◽  
Three Dimensional ◽  
Stability Limit ◽  
Analytical Form ◽  
Poisson's Ratio ◽  
Three Dimensional Printing ◽  
Uniaxial Test ◽  
Constitutive Properties ◽  
The Stability

In this paper, we propose a class of lattice structures with macroscopic Poisson's ratio arbitrarily close to the stability limit −1. We tested experimentally the effective Poisson's ratio of the microstructured medium; the uniaxial test was performed on a thermoplastic lattice produced with a three-dimensional printing technology. A theoretical analysis of the effective properties was performed, and the expression of the macroscopic constitutive properties is given in full analytical form as a function of the constitutive properties of the elements of the lattice and on the geometry of the microstructure. The analysis was performed on three microgeometries leading to an isotropic behaviour for the cases of three- and sixfold symmetries and to a cubic behaviour for the case of fourfold symmetry.

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