scholarly journals A Eulerian Multi-Fluid Model for High-Speed Evaporating Sprays

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 941
Author(s):  
Robert Keser ◽  
Michele Battistoni ◽  
Hong G. Im ◽  
Hrvoje Jasak
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Fluid Model ◽  
Operating Conditions ◽  
Droplet Breakup ◽  
Triangular Distribution ◽  
Complex Dynamic ◽  
Academic Settings ◽  
Combustion Technology ◽  
Ideal Framework

Advancements in internal combustion technology, such as efficiency improvements and the usage of new complex fuels, are often coupled with developments of suitable numerical tools for predicting the complex dynamic behavior of sprays. Therefore, this work presents a Eulerian multi-fluid model specialized for the dynamic behavior of dense evaporating liquid fuel sprays. The introduced model was implemented within the open-source OpenFOAM library, which is constantly gaining popularity in both industrial and academic settings. Therefore, it represents an ideal framework for such development. The presented model employs the classes method and advanced interfacial momentum transfer models. The droplet breakup is considered using the enhanced WAVE breakup model, where the mass taken from the parent droplets is distributed among child classes using a triangular distribution. Furthermore, the complex thermal behavior within the moving droplets is considered using a parabolic temperature profile and an effective thermal conductivity approach. This work includes an uncertainty estimation analysis (for both spatial and temporal resolutions) for the developed solver. Furthermore, the solver was validated against two ECN Spray A conditions (evaporating and non-evaporating). Overall, the presented results show the capability of the implemented model to successfully predict the complex dynamic behavior of dense liquid sprays for the selected operating conditions.

Bearings Influence on the Dynamic Behavior of HSM Spindle

2012 ◽  
Author(s):  
David Noel ◽  
Mathieu Ritou ◽  
Sebastien Le Loch ◽  
Benoit Furet
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Design Parameters ◽  
Mechanics Model ◽  
Bearing Stiffness ◽  
Rough Milling ◽  
The Impact

The aeronautic industry requires high speed and high power spindles to obtain high material removal rates during long rough milling operations. The weakness of HSM spindle is the bearings, although high precision hybrid ball bearings have been developed to achieve this critical application. Inadequate use of spindles inevitably leads to shortened lifetimes. Choosing the operating conditions is a required step before machining applications. It can be achieved through either experimental tests or numerical modeling that leads to stability lobe diagrams. Stability of cuts relies on the dynamic behavior of the spindle, which is particularly due to the eigenfrequencies of the tool-shaft assembly. The frequencies depend on bearing stiffness that can change under operating conditions. That is why the impact of cutting conditions and bearing parameters on its stiffness are studied in the paper. A five degrees of freedom model of angular ball bearing is briefly presented. A complete bearing model is introduced. The originality of the approach is the complete technological modeling, notably of the radial expansions of inner and outer rings of bearing. A non-linear expression is established from continuum mechanics model. The influence of geometry of bearing, operating conditions and design parameters of spindle on the bearing stiffness are established and analysed. Then, modal analyses of the tool-spindle assembly are carried out in relation to the varying bearing stiffness. Finally, significance of the approach is demonstrated through the analyses of Frequency Response Function.

Ball bearing turbocharger vibration management: application on high speed balancer

2020 ◽  
Vol 21 (6) ◽  
pp. 619
Author(s):  
Kostandin Gjika ◽  
Antoine Costeux ◽  
Gerry LaRue ◽  
John Wilson
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Ball Bearing ◽  
Squeeze Film ◽  
Design And Technology ◽  
Squeeze Film Damper ◽  
Damping Coefficients ◽  
Bearing Loads ◽  
Stiffness And Damping

Today's modern internal combustion engines are increasingly focused on downsizing, high fuel efficiency and low emissions, which requires appropriate design and technology of turbocharger bearing systems. Automotive turbochargers operate faster and with strong engine excitation; vibration management is becoming a challenge and manufacturers are increasingly focusing on the design of low vibration and high-performance balancing technology. This paper discusses the synchronous vibration management of the ball bearing cartridge turbocharger on high-speed balancer and it is a continuation of papers [1–3]. In a first step, the synchronous rotordynamics behavior is identified. A prediction code is developed to calculate the static and dynamic performance of “ball bearing cartridge-squeeze film damper”. The dynamic behavior of balls is modeled by a spring with stiffness calculated from Tedric Harris formulas and the damping is considered null. The squeeze film damper model is derived from the Osborne Reynolds equation for incompressible and synchronous fluid loading; the stiffness and damping coefficients are calculated assuming that the bearing is infinitely short, and the oil film pressure is modeled as a cavitated π film model. The stiffness and damping coefficients are integrated on a rotordynamics code and the bearing loads are calculated by converging with the bearing eccentricity ratio. In a second step, a finite element structural dynamics model is built for the system “turbocharger housing-high speed balancer fixture” and validated by experimental frequency response functions. In the last step, the rotating dynamic bearing loads on the squeeze film damper are coupled with transfer functions and the vibration on the housings is predicted. The vibration response under single and multi-plane unbalances correlates very well with test data from turbocharger unbalance masters. The prediction model allows a thorough understanding of ball bearing turbocharger vibration on a high speed balancer, thus optimizing the dynamic behavior of the “turbocharger-high speed balancer” structural system for better rotordynamics performance identification and selection of the appropriate balancing process at the development stage of the turbocharger.

Dynamic analysis of a helical gear reduction by experimental and numerical methods

2020 ◽  
Vol 68 (1) ◽  
pp. 48-58
Author(s):  
Chao Liu ◽  
Zongde Fang ◽  
Fang Guo ◽  
Long Xiang ◽  
Yabin Guan ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Dynamic Analysis ◽  
Dynamic Behavior ◽  
Fourth Order ◽  
Numerical Models ◽  
Helical Gear ◽  
Operating Conditions ◽  
Dynamic Responses ◽  
Lumped Mass ◽  
Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

High-Speed Atomic Force Microscopy for Studying the Dynamic Behavior of Protein Molecules at Work

2006 ◽  
Vol 45 (3B) ◽  
pp. 1897-1903 ◽  
Author(s):  
Toshio Ando ◽  
Takayuki Uchihashi ◽  
Noriyuki Kodera ◽  
Atsushi Miyagi ◽  
Ryo Nakakita ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Dynamic Behavior ◽  
High Speed ◽  
Force Microscopy ◽  
Atomic Force ◽  
Protein Molecules

Flow Features Analysis of Throttle Notches of Proportional Direct Valve

2011 ◽  
Vol 189-193 ◽  
pp. 2285-2288
Author(s):  
Wen Hua Jia ◽  
Chen Bo Yin ◽  
Guo Jin Jiang
Keyword(s):  
Fluid Flow ◽  
Dynamic Behavior ◽  
Flow Rate ◽  
Discharge Coefficient ◽  
3D Models ◽  
Operating Conditions ◽  
Flow Models ◽  
Flow Features ◽  
Rate Discharge ◽  
Spool Valve

Flow features, specially, flow rate, discharge coefficient and efflux angle under different operating conditions are numerically simulated, and the effects of shapes and the number of notches on them are analyzed. To simulate flow features, 3D models are developed as commercially available fluid flow models. Most construction machineries in different conditions require different actions. Thus, in order to be capable of different actions and exhibit good dynamic behavior, flow features should be achieved in designing an optimized proportional directional spool valve.

Bifurcation Analysis of Self-Acting Gas Journal Bearings

2001 ◽  
Vol 123 (4) ◽  
pp. 755-767 ◽  
Author(s):  
Cheng-Chi Wang ◽  
Cha’o-Ku`ang Chen
Keyword(s):  
Dynamic Behavior ◽  
Reynolds Equation ◽  
Rotational Velocity ◽  
Power Spectra ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Finite Differences Method ◽  
Subharmonic Response ◽  
Rotor Center ◽  
Rotor Mass

This paper studies the bifurcation of a rigid rotor supported by a gas film bearing. A time-dependent mathematical model for gas journal bearings is presented. The finite differences method and the Successive Over Relation (S.O.R) method are employed to solve the Reynolds’ equation. The system state trajectory, Poincare´ maps, power spectra, and bifurcation diagrams are used to analyze the dynamic behavior of the rotor center in the horizontal and vertical directions under different operating conditions. The analysis shows how the existence of a complex dynamic behavior comprising periodic and subharmonic response of the rotor center. This paper shows how the dynamic behavior of this type of system varies with changes in rotor mass and rotational velocity. The results of this study contribute to a further understanding of the nonlinear dynamics of gas film rotor-bearing systems.

scholarly journals The Influence of Carrier Air Preheating on Autoignition of Inline-Injected Hydrogen–Nitrogen Mixtures in Vitiated Air of High Temperature

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Christoph A. Schmalhofer ◽  
Peter Griebel ◽  
Manfred Aigner
Keyword(s):  
Hydrogen Content ◽  
Gas Turbines ◽  
High Speed ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Promoting Effect ◽  
Experimental Conditions ◽  
Lean Premixed Combustion ◽  
Image Velocimetry ◽  
Fuel Mixtures

The use of highly reactive hydrogen-rich fuels in lean premixed combustion systems strongly affects the operability of stationary gas turbines (GT) resulting in higher autoignition and flashback risks. The present study investigates the autoignition behavior and ignition kernel evolution of hydrogen–nitrogen fuel mixtures in an inline co-flow injector configuration at relevant reheat combustor operating conditions. High-speed luminosity and particle image velocimetry (PIV) measurements in an optically accessible reheat combustor are employed. Autoignition and flame stabilization limits strongly depend on temperatures of vitiated air and carrier preheating. Higher hydrogen content significantly promotes the formation and development of different types of autoignition kernels: More autoignition kernels evolve with higher hydrogen content showing the promoting effect of equivalence ratio on local ignition events. Autoignition kernels develop downstream a certain distance from the injector, indicating the influence of ignition delay on kernel development. The development of autoignition kernels is linked to the shear layer development derived from global experimental conditions.

Feasibility of High Speed Furnace Drawing of Optical Fibers

2004 ◽  
Vol 126 (5) ◽  
pp. 852-857 ◽  
Author(s):  
Xu Cheng ◽  
Yogesh Jaluria
Keyword(s):  
Optical Fibers ◽  
High Speed ◽  
Flow Instability ◽  
Fiber Quality ◽  
Domain Boundary ◽  
Operating Conditions ◽  
Furnace Temperature ◽  
Fiber Drawing ◽  
Heated Zone ◽  
Additional Information

The domain of operating conditions, in which the optical fiber-drawing process is successful, is an important consideration. Such a domain is mainly determined by the stresses acting on the fiber and by the stability of the process. This paper considers an electrical resistance furnace for fiber drawing and examines conditions for process feasibility. In actual practice, it is known that only certain ranges of furnace temperature and draw speed lead to successful fiber drawing. The results obtained here show that the length of the heated zone and the furnace temperature distribution are other important parameters that can be varied to obtain a feasible process. Physical behavior close to the boundary of the feasible domain is also studied. It is found that the iterative scheme for neck-down profile determination diverges rapidly when the draw temperature is lower than that at the acceptable domain boundary due to the lack of material flow. However, the divergence rate becomes much smaller as the temperature is brought close to the domain boundary. Additional information on the profile determination as one approaches the acceptable region is obtained. It is found that it is computationally expensive and time-consuming to locate the exact boundary of the feasible drawing domain. From the results obtained, along with practical considerations of material rupture, defect concentration, and flow instability, an optimum design of a fiber-drawing system can be obtained for the best fiber quality.

Characteristics of air entrainment during dynamic wetting failure along a planar substrate

2014 ◽  
Vol 747 ◽  
pp. 119-140 ◽  
Author(s):  
E. Vandre ◽  
M. S. Carvalho ◽  
S. Kumar
Keyword(s):  
High Speed ◽  
Water Solution ◽  
Air Entrainment ◽  
Dynamic Contact ◽  
Operating Conditions ◽  
Dynamic Wetting ◽  
Glycerol Water ◽  
Planar Substrate ◽  
Wide Range ◽  
Stationary Plate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

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