Modeling of Cavitation Induced Fuel Atomization and Breakup Processes

2017 ◽  
Author(s):  
Bolin Zhao ◽  
C. P. Chen
Keyword(s):  
Aerodynamic Force ◽  
Current Model ◽  
Flow Characteristics ◽  
Theoretical Development ◽  
Fuel Injector ◽  
Initial Flow ◽  
Cavitation Effect ◽  
Primary Breakup ◽  
Turbulence Effects ◽  
Large Pressure Gradient

Recent experimental and modeling studies have indicated that turbulence and cavitation behaviors within a realistic fuel injector have significant effects on the liquid atomization and spray processes. In addition to the breakup process induced by aerodynamic force at the liquid/gas interface, the effects of flow characteristics including turbulence and cavitation inside the injector nozzle on atomization have been shown to be important. The cavitation within the injector is complicated by the turbulent flow under large pressure gradient and geometry of the injector orifice. We have previously developed the “T-blob” and “T-TAB” model, for liquid fuel primary and secondary breakup predictions respectively, to account for liquid turbulence effects within the injector. The objective of this study is to further account for the cavitation effect in the atomization process of a cylindrical liquid jet. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and the initial flow conditions. These scales are further modified to include the cavitation effect. The drop size formed is estimated based on the energy distribution among wave, turbulence and cavitation modes. This paper describes theoretical development of the current model. Both non-evaporating and evaporating spray cases will be investigated to validate the newly developed cavitation-induced atomization model.

scholarly journals Numerical Simulation of Liquid Jet Atomization Including Turbulence Effects

2007 ◽  
Vol 129 (4) ◽  
pp. 920-928 ◽  
Author(s):  
Huu P. Trinh ◽  
C. P. Chen ◽  
M. S. Balasubramanyam
Keyword(s):  
Current Model ◽  
Droplet Breakup ◽  
Spray Angle ◽  
Liquid Jet ◽  
Primary Breakup ◽  
Turbulence Effects ◽  
Turbulence Effect ◽  
Blob Model ◽  
Secondary Breakup ◽  
Liquid Jet Atomization

This paper describes numerical implementation and validation of a newly developed hybrid model, T-blob/T-TAB, into an existing computational fluid dynamics (CFD) program for primary and secondary breakup simulation of liquid jet atomization. This model extends two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (the “blob” model) (1987, Atomization Spray Technol., 3, pp. 309–337) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup of O’Rourke and Amsden (1987, SAE Technical Paper No. 872089) to include liquid turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and flow conditions at the liquid nozzle exit. Transition to the secondary breakup was modeled based on energy balance, and an additional turbulence force acted on parent drops was modeled and integrated into the TAB governing equation. Several assessment studies are presented, and the results indicate that the existing KH and TAB models tend to underpredict the product drop size and spray angle, whereas the current model provides superior results when compared to the measured data.

scholarly journals Study the effect of angle of attack on flow characteristics at racing bike helmet using CFD

2018 ◽  
Vol 204 ◽  
pp. 06001
Author(s):  
Syamsuri ◽  
M Hasan Syafik ◽  
Yudho Putro Iswanto
Keyword(s):  
Numerical Simulations ◽  
Drag Coefficient ◽  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Flow Characteristics ◽  
Reynold Number ◽  
Attack Angle ◽  
Large Area ◽  
Drag Racing ◽  
Simulation Results

At a cyclist drag racing champions greatly affect the speed of the bike, especially on the use of racing bike helmets. If the aerodynamic force from the racing bike helmet is getting smaller than the use of helmets on the bike racing will be more optimal and will affect the rate of the racer. In this study, numerical simulations were used to investigate the magnitude of the drag force that occurs around the surface of the helmet. With CFD software, 4 variations of attack angle 0°, 10°, 20° and 30° and variations of Reynold number 7.14x104, 1.00x105, and 1.16x105 are simulated to determine the flow characteristics of each state. The simulation results show that large area vortex is formed at the bottom of the helmet curve and dominates at the attack angle 30°. The result of the drag coefficient generated at the angle of attack 0° to 20° tends to decrease but at the attack angle 200 and 30° the drag coefficient increases.

The evolution of the initial flow structures of a highly under-expanded circular jet

2019 ◽  
Vol 871 ◽  
pp. 305-331 ◽  
Author(s):  
Huan-Hao Zhang ◽  
Nadine Aubry ◽  
Zhi-Hua Chen ◽  
Wei-Tao Wu ◽  
Sha Sha
Keyword(s):  
Vortex Ring ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Structures ◽  
Secondary Vortex ◽  
Shock Cell ◽  
Initial Flow ◽  
Turbulence Transition ◽  
Circular Jets ◽  
Generation Mechanisms

The three-dimensional flow characteristics of the compressible vortex ring generated by under-expanded circular jets with two typical pressure ratios, i.e. $n=1.4$ (moderate) and 4.0 (high), are investigated numerically with the use of large-eddy simulations. Our results illustrate that these two pressure ratios correspond to different shock structures (shock cell and Mach disc, respectively) within the jet. These two typical types of flow structures and characteristics are discussed and validated with experiments, and the different generation mechanisms of the secondary vortex rings are compared. Moreover, detailed information about the evolution of the secondary vortex ring, primary vortex ring and turbulence transition features, including the radial and azimuthal modes, is investigated. The geometric features and mixing effects of the jets are also explored.

Analysis on the Convection of Highway in Permafrost Regions

2012 ◽  
Vol 204-208 ◽  
pp. 1644-1647
Author(s):  
Xiao Yu Sun ◽  
Zhen Qing Wang ◽  
Hong Tao Xing ◽  
Yong Heng Tong
Keyword(s):  
Flow Characteristics ◽  
Theoretical Development ◽  
Construction Costs ◽  
Rural Highways ◽  
Percent Time ◽  
Traffic Volumes ◽  
Percent Time Spent Following ◽  
The Cost ◽  
Permafrost Regions ◽  
Key Parameter

The purpose of this study was to evaluate flow characteristics on two-lane rural highways and to develop criteria for highway widening The study is conducted on two tracks: theoretical development of delay models and use of a simulation model to estimate the effect of certain parameters on delay and percent-time-spent-following. Models of delay are presented, as are the regions in which the traffic is stable or unstable. It was also possible from the simulation to obtain the percent-time-spent-following, which is a key parameter in determining level-of-service on two-lane highways.The accrued delay over the usable life of a two-lane highway pavement, assumed to be 20 years, was discounted to present monetary value This was then compared to four typical construction costs for different terrain types. The threshold average daily traffic volumes were determined at the points where the present value of the accumulated delay was equal to the cost of constructing two more lanes. These threshold values can be used as criteria for widening a two-lane highway and converting it into a four-lane facility. Additional criteria, based on percent-time-spent-following, are also presented.

Detailed Dynamic Modelling of an Integrated Hydraulic Actuator

2020 ◽  
Author(s):  
Dom Wilson ◽  
Ioannis Georgilas ◽  
Andrew Plummer ◽  
Pejman Iravani ◽  
Dhinesh Sangiah
Keyword(s):  
High Performance ◽  
Dynamic Modelling ◽  
Flow Characteristics ◽  
Hydraulic Cylinder ◽  
Theoretical Development ◽  
Hydraulic Actuator ◽  
Pressure Losses ◽  
Low Leakage ◽  
Smart Actuator ◽  
And Control

Abstract Hydraulic servos are characterised by their high-performance nature but due to their size and weight are not suitable for robotics where new legged applications require high power density and excellent dynamic behaviour in a small size. As an answer to this need a new class of integrated smart actuators is being developed. These systems consist of a servo valve, hydraulic cylinder, sensors and a controller all in a single device. This paper outlines the detailed modelling of the smart actuator for use in simulation and control design. The result is a model consisting of the dynamics of the novel ultra-low leakage servovalve, the valve flow characteristics considering the properties of each spool land, the single-ended cylinder with friction and the pressure losses in the supply and return lines to the actuator. The models are a combination of empirical and theoretical development, validated with experimental data. The smart actuator’s unique properties; compactness, weight and efficiency, combined with high-performance hydraulics make it well suited to mobile robot applications.

Test rig to determine the fuel injector flow characteristics

2013 ◽  
Vol 59 (1) ◽  
pp. 33-41
Author(s):  
Rafał Dychto ◽  
Jacek Leyko ◽  
Grzegorz Mitukiewicz
Keyword(s):  
Flow Characteristics ◽  
Fuel Injector ◽  
Test Rig

Aerodynamic Simulation of Road Vehicle in Steady Crosswind

2013 ◽  
Vol 376 ◽  
pp. 341-344
Author(s):  
Shan Ling Han ◽  
Ru Xing Yu ◽  
Yu Yue Wang ◽  
Gui Shen Wang
Keyword(s):  
Flow Field ◽  
Wind Direction ◽  
Motor Vehicle ◽  
Aerodynamic Force ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
External Flow ◽  
Slant Angle ◽  
Ahmed Body

Because crosswind affects drivers to control their vehicles safely, the research on flow characteristics in automotive crosswind has a great significance to improve the crosswind stability of the vehicle. By the steady state numerical simulation method, the aerodynamic characteristics of external flow field of Ahmed body in crosswind was investigated. The Ahmed body with 25° slant angle is built in UG NX. The external flow field of the Ahmed body in the wind direction of 0°, 15º, 30° angle is simulated in XFlow software. According to the map of the pressure and velocity distribution, the flow field both before and after, as well as left and right has significant change as the wind direction angle increased, and the trail turbulence intensity also changes. The changes of aerodynamic force and moment affect the driving stability of a motor vehicle.

scholarly journals Effects of Nozzle Shape on the Flow Characteristics of Premix Injector Using Computational Fluid Dynamics (CFD)

2015 ◽  
Vol 773-774 ◽  
pp. 450-454
Author(s):  
Ronny Yii Shi Chin ◽  
Shahrin Hisham Amirnordin ◽  
Amir Khalid
Keyword(s):  
Flow Characteristics ◽  
Fuel Injector ◽  
Spray Characteristics ◽  
Hole Shape ◽  
Injector Nozzle ◽  
K Factor ◽  
Efficient Combustion ◽  
Nozzle Hole ◽  
Nozzle Geometries ◽  
Air Nozzle

The burner system is a patented, unique, higher-efficiency and fuel-injector system that works with a specially designed oil burner to create ultra-efficient combustion that reduces oil use, greenhouse gases and other harmful emissions. This research shows the injector nozzle geometries play a significant role in spray characteristics, atomization and formation of fuel-air mixture in order to improve combustion performance, and decrease some pollutant products from burner system. The aim of this research is to determine the effects of nozzle hole shape on spray characteristics of the premix injector by using CFD. Multiphase of volume of fluid (VOF) cavitating flow inside nozzles are determined by means of steady simulations and Eulerian-Eulerian two-fluid approach is used for performing mixing of Jatropha oil and air. Nozzle flow simulations resulted that cavitation area is strongly dependent on the nozzle hole shape. Conical hole with k-factor of 2 provides higher flow velocity and turbulent kinetic energy compared with conical hole with k-factor of 1.3 and cylindrical hole. The results show that the premix injector nozzle hole shape gives impact to the spray characteristics and indirectly affects the emission of the system.

Numerical study on characteristics of unsteady flow in a centrifugal pump volute at partial load condition

2015 ◽  
Vol 32 (6) ◽  
pp. 1549-1566 ◽  
Author(s):  
Lei Tan ◽  
Baoshan Zhu ◽  
Yuchuan Wang ◽  
Shuliang CAO ◽  
Shaobo Gui
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Dominant Frequency ◽  
Content Type ◽  
Cavitation Effect ◽  
Partial Load ◽  
Large Pressure Gradient

Purpose – The purpose of this paper is to elucidate the detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition. Design/methodology/approach – Unsteady flows in a centrifugal pump volute at non-cavitation and cavitation conditions are investigated by using a computation fluid dynamics framework combining the re-normalization group k-e turbulence model and the mass transport cavitation model. Findings – The flow field in pump volute is very complicated at part load condition with large pressure gradient and intensive vortex movement. Under cavitation conditions, the dominant frequency for most of the monitoring points in volute transit from the blade passing frequency to a lower frequency. Generally, the maximum amplitudes of pressure fluctuations in volute at serious cavitation condition is twice than that at non-cavitation condition because of the violent disturbances caused by cavitation shedding and explosion. Originality/value – The detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition are revealed and analysed.

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