Experimental Determination of Statistical Properties of Two-Phase Turbulent Motion

1960 ◽  
Vol 82 (3) ◽  
pp. 609-621 ◽  
Author(s):  
S. L. Soo ◽  
H. K. Ihrig ◽  
A. F. El Kouh
Keyword(s):  
Gas Phase ◽  
Tracer Diffusion ◽  
Statistical Properties ◽  
Solid Particles ◽  
Turbulent Motion ◽  
Two Phase ◽  
Gaseous State ◽  
Diffusion Technique ◽  
And Diffusion

Experimental methods for the determination of certain statistical properties of turbulent conveyance and diffusion of solid particles in a gaseous state are presented. Methods include a tracer-diffusion technique for the determination of gas-phase turbulent motion and a photo-optical technique for the determination of motion of solid particles. Results are discussed and compared with previous analytical results.

scholarly journals Experimental and Numerical Analysis on Two-Phase Induced Low-Speed Pre-Ignition

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5063
Author(s):  
Norbert Zöbinger ◽  
Thorsten Schweizer ◽  
Thomas Lauer ◽  
Heiko Kubach ◽  
Thomas Koch
Keyword(s):  
Gas Phase ◽  
Cfd Simulation ◽  
Particle Temperature ◽  
Solid Particles ◽  
Two Phase ◽  
Engine Operation ◽  
Oil Droplet ◽  
Low Speed ◽  
Detailed Reaction Mechanism ◽  
Oil Fuel

The root cause of the initial low-speed pre-ignition (LSPI) is not yet clarified. The literature data suggest that a two-phase phenomenon is most likely triggering the unpredictable premature ignitions in highly boosted spark-ignition engines. However, there are different hypotheses regarding the actual initiator, whether it is a detached liquid oil-fuel droplet or a solid-like particle from deposits. Therefore, the present work investigates the possibility of oil droplet-induced pre-ignitions using a modern downsized engine with minimally invasive endoscopic optical accessibility incorporating in-cylinder lubrication oil detection via light-induced fluorescence. This setup enables the differentiation between liquid and solid particles. Furthermore, the potential of hot solid particles to initiate an ignition under engine-relevant conditions is analyzed numerically. To do so, the particle is generalized as a hot surface transferring heat to the reactive ambient gas phase. The gas-phase reactivity is represented as a TRF/air mixture based on RON/MON specifications of the investigated fuel. The chemical processes are predicted using a semi-detailed reaction mechanism, including 137 species and 633 reactions in a 2D CFD simulation framework. In the optical experiments, no evidence of a liquid oil droplet-induced pre-ignition could be found. Nevertheless, all observed pre-ignitions had a history of flying light-emitting objects. There are strong hints towards solid-like deposit LSPI initiation. The application of the numerical methodology to mean in-cylinder conditions of an LSPI prone engine operation point reveals that particles below 1000 K are not able to initiate a pre-ignition. A sensitivity analysis of the thermodynamic boundary conditions showed that the particle temperature is the most decisive parameter on the calculated ignition delay time.

The Application of Numerical Simulation to Liquid Pipeline Leakage at LNG Terminal in China

2020 ◽  
Author(s):  
Zhichao Guo ◽  
Zhaoci Li
Keyword(s):  
Numerical Simulation ◽  
Liquid Phase ◽  
Natural Gas ◽  
Diffusion Process ◽  
Gas Phase ◽  
Stokes Equations ◽  
Response Strategy ◽  
Movement Trajectory ◽  
Two Phase ◽  
And Diffusion

Abstract In 2018, China’s natural gas import reached 90.39 million tons, and the liquefied natural gas (LNG) import was 53.78 million tons, accounting for 59.5% of total natural gas imports. With the construction of LNG terminals, more studies on the leakage of LNG storage and transportation facilities have emerged to prevent catastrophic consequences such as explosions and frostbite. However, most of previous researches focused on gas pipeline leakage after LNG gasification, and few of those have been done on LNG liquid pipeline leakage. In this paper, Fluent software is used to numerically simulate the process of LNG liquid pipeline leakage. After the occurrence of LNG leakage, it will suffer the process of endothermic, evaporation, and diffusion, which is considered as a two-phase diffusion process. The Euler-Lagrangian method is introduced to simulate the diffusion process of gas phase and liquid phase separately. In the simulation, the liquid phase is regarded as discrete droplets for discrete processing. The movement trajectory, heat transfer process and evaporation process of each droplet are tracked respectively. Different from the liquid phase, the gas phase is regarded as a continuous phase and the Navier-Stokes equations are adopted for calculation. Thereafter, coupling calculations of two phase are performed to determine the concentration field and temperature field of the LNG liquid pipeline leakage. As a supplement to this research, the influence of wind speed on LNG leakage and diffusion process is analysed in detail. Finally, the numerical simulation method is applied to a coastal LNG terminal in northern China to determine the distribution of natural gas concentration and temperature, as well as delimit the combustion range. The results can provide scientific reference for the delimitation of risky zones and the formulation of emergency response strategy.

Site Preference and Diffusion in Ni3Al Alloyed with Ir, Ta or Re at 1200°C

2010 ◽  
Vol 297-301 ◽  
pp. 1322-1327 ◽  
Author(s):  
N. Garimella ◽  
H.J. Choi ◽  
Yong Ho Sohn
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Site Preference ◽  
Solid Diffusion ◽  
Ordered Intermetallic ◽  
Ternary Alloying ◽  
Tracer Diffusion Coefficients ◽  
Interdiffusion Coefficients ◽  
And Diffusion

Diffusion in L12-Ni3Al with ternary alloying additions of Ir, Ta and Re was investigated at 1200°C using solid-to-solid diffusion couples, and examined with respect to site preference in ordered intermetallic compound. In addition to determination of average ternary interdiffusion coefficients [1-3], average effective interdiffusion coefficients were determined directly from the experimental concentration profiles. Ni has the largest magnitude of average effective interdiffusion coefficient, followed by Al, Ir, Re and Ta. The average effective interdiffusion coefficients for Ir, Re and Ta are much smaller than those for Ni and Al. Tracer diffusion coefficients determined by extrapolation technique, and available literature also followed the same trend. The relative tendency of Ni, Al, Ir, Re and Ta to occupy the -Ni and -Al sites are correlated to these diffusion coefficients, with due consideration for diffusion mechanisms and coordination of atoms.

Effect of the Wall on Two-Phase Turbulent Motion

1960 ◽  
Vol 27 (1) ◽  
pp. 5-15 ◽  
Author(s):  
S. L. Soo ◽  
C. L. Tien
Keyword(s):  
Stationary Solution ◽  
Turbulence Intensity ◽  
Solid Particles ◽  
Turbulent Intensity ◽  
Turbulent Motion ◽  
Two Phase ◽  
The Mean

Stationary solution on the effect of a wall on two-phase (solid particles in gas) turbulent motion shows that the intensity of motion of solid particles is affected by the presence of the wall and the distribution of turbulent intensity of the stream near the wall. The intensity of motion of solid particles can be significantly higher than the turbulence intensity of the mean stream. These modifications are consequences of Bernoulli force acting between the wall and the particle.

Electrical Mobilities and Tracer-diffusion Coefficients of the Na and Tl Ions in the Molten (Na — Tl)NO3 System

1967 ◽  
Vol 22 (8) ◽  
pp. 1171-1176 ◽  
Author(s):  
Sandro Forcheri ◽  
Vittoriano Wagner
Keyword(s):  
Diffusion Coefficients ◽  
Tracer Diffusion ◽  
Significant Feature ◽  
Rapid Variation ◽  
Polarization Model ◽  
Diffusion Technique ◽  
Zone Electrophoresis ◽  
Ionic Mobilities ◽  
Tracer Diffusion Coefficients ◽  
And Diffusion

The ionic mobilities and the diffusion coefficients of Na and Tl in the (Na-Tl) NO3 system have been determined by means of a zone electrophoresis and diffusion technique. The most significant feature of the Na mobility isotherm is its rapid variation with composition in the NaNO3 rich region.The diffusion coefficients of both cations have been found to depend rather weakly on composition. The electrical and diffusional mobilities of both cations show trends opposite to that of the fluidity.These results are discussed in terms of the anion polarization model.

scholarly journals Fuzzy-GMC Control of Gas-Phase Propylene Copolymerization in Fluidized Bed Reactor

2018 ◽  
Vol 156 ◽  
pp. 07002
Author(s):  
Nazratul Fareha Salahuddin ◽  
Ahmad Shamiri ◽  
Mohd Azlan Hussain ◽  
Navid Mostoufi
Keyword(s):  
Gas Phase ◽  
Fluidized Bed ◽  
Fuzzy Logic Controller ◽  
Fluidized Bed Reactor ◽  
Solid Particles ◽  
Phase Model ◽  
Regulatory Control ◽  
Generic Model ◽  
Two Phase ◽  
Model Control

A modified two-phase model for gas phase propylene and ethylene copolymerization was chosen to represent the process in a fluidized bed reactor. This model considered the entrainment of solid particles in the reactor, as a modification to the original two-phase model assumptions. The non-linearity of this process makes it difficult to control just by using conventional controller such as PID. A hybrid control strategy (a simple designed fuzzy logic controller (FLC) integrated with generic model control (GMC)) is designed to control the temperature of the reactor. This advanced control system was compared with the GMC and conventional PID controller. The simulation results showed that the hybrid controller (Fuzzy-GMC) performed better than both GMC and PID in terms of both servo and regulatory control.

scholarly journals Determination of dryout localization using a five-equation model of annular flow for boiling in minichannels

2017 ◽  
Vol 38 (1) ◽  
pp. 123-139 ◽  
Author(s):  
Jan Wajs ◽  
Dariusz Mikielewicz
Keyword(s):  
Liquid Film ◽  
Mass Balance ◽  
Gas Phase ◽  
Annular Flow ◽  
Film Flow ◽  
Equation Model ◽  
Two Phase ◽  
Model Predictions ◽  
Cross Correlations

AbstractDetailed studies have suggested that the critical heat flux in the form of dryout in minichannels occurs when the combined effects of entrainment, deposition, and evaporation of the film make the film flow rate go gradually and smoothly to zero. Most approaches so far used the mass balance equation for the liquid film with appropriate formulations for the rate of deposition and entrainment respectively. It must be acknowledged that any discrepancy in determination of deposition and entrainment rates, together with cross-correlations between them, leads to the loss of accuracy of model predictions. Conservation equations relating the primary parameters are established for the liquid film and vapor core. The model consists of three mass balance equations, for liquid in the film as well as two-phase core and the gas phase itself. These equations are supplemented by the corresponding momentum equations for liquid in the film and the two-phase core. Applicability of the model has been tested on some experimental data.

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