scholarly journals Analysis of Flow Characteristics in SCR Mixing Chambers of Different Shapes

2017 ◽  
Author(s):  
Kyongjun Lee ◽  
Sechang Park
Keyword(s):  
Flow Characteristics ◽  
Different Shapes ◽  
Mixing Chambers

Thermal Performance of a Corrugated Wall With Artificial Roughness

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Rabia Ferhat ◽  
Ahmed Zineddine Dellil ◽  
Khadidja Boualem ◽  
M-Kamal Hamidou
Keyword(s):  
Thermal Performance ◽  
Flow Characteristics ◽  
Artificial Roughness ◽  
Inlet Channel ◽  
Ansys Fluent ◽  
Plate Heat ◽  
Corrugated Channel ◽  
Improve Heat Transfer ◽  
Different Shapes ◽  
Corrugated Wall

This paper aims to determine the flow characteristics and thermal performance of plate heat exchangers. The study is divided into two parts. In the first part, four different shapes of corrugated boundaries have been recommended, rectangular, trapezoidal, triangular, and sinusoidal shapes. In addition, an artificial roughness has been introduced to improve heat transfer within corrugated channel. In the second part, a corrugated wall was used at the inlet channel. Numerical results are presented as Nusselt number (Nu) and friction factor (Cf) using the commercial software ansys-fluent where the Reynolds number is ranged between 3000 and 12,000. The results of this investigation reveal that the overall thermal performance improves greatly by 50% due to the use of the sinusoidal artificial roughness and added undulations in the inlet channel. It is also observed that the latter case with the ratio A″/λ″ = 0.05 is the optimal design for the plate heat exchanger.

A Numerical Investigation of Transient Flow and Cavitation Within Minisac and Valve-Covered Orifice Diesel Injector Nozzles

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Won Geun Lee ◽  
Rolf D. Reitz
Keyword(s):  
Fuel Injection ◽  
Transient Flow ◽  
Flow Characteristics ◽  
Transient Behavior ◽  
Injection Rate ◽  
Arbitrary Lagrangian Eulerian ◽  
Variable Speed ◽  
Fast Decrease ◽  
Different Shapes ◽  
Fuel Injection Rate

Cavitating flow within diesel injector passages has been investigated numerically using the homogeneous equilibrium model (HEM), which uses the barotropic assumption and the variable speed of sound of the mixture. To apply the HEM, the KIVA-3V code was modified to implement a generalized equation of state, and injector needle movement is simulated by the arbitrary Lagrangian-Eulerian (ALE) approach and the snapper algorithm. It is demonstrated that the model can predict the effect of nozzle passage geometry on the flow structure and cavitation. The model is able to reproduce the transient fuel injection rate as a function of the needle lift profile. Special interest is focused on the transient behavior during the nozzle closing period, which shows that the fast decrease in flow rate can increase the cavitation in the nozzle passage. The effects of the pressure difference and environment pressure on cavitation augmentation at the end-of-injection were also investigated. Flow characteristics due to different shapes of the nozzle flow passage in axisymmetric single hole nozzles and multihole nozzle configurations (minisac and valve-covered orifice eight-hole nozzles) were compared with emphasis on the end-of-injection period.

A Numerical Investigation of Transient Flow and Cavitation Within Minisac and VCO Diesel Injector Nozzles

2009 ◽  
Author(s):  
Won Geun Lee ◽  
Rolf D. Reitz
Keyword(s):  
Fuel Injection ◽  
Transient Flow ◽  
Flow Characteristics ◽  
Transient Behavior ◽  
Injection Rate ◽  
Arbitrary Lagrangian Eulerian ◽  
Variable Speed ◽  
Fast Decrease ◽  
Different Shapes ◽  
Fuel Injection Rate

Cavitating flow within diesel injector passages has been investigated numerically using the Homogeneous Equilibrium Model (HEM), which uses the barotropic assumption and the variable speed of sound of the mixture. To apply the HEM, the KIVA-3V code was modified to implement a generalized equation of state, and injector needle movement is simulated by the Arbitrary Lagrangian-Eulerian (ALE) approach and the snapper algorithm. It is demonstrated that the model can predict the effect of nozzle passage geometry on the flow structure and cavitation. The model is able to reproduce the transient fuel injection rate as a function of the needle lift profile. Special interest is focused on the transient behavior during the nozzle closing period, which shows that the fast decrease in flow rate can increase the cavitation in the nozzle passage. The effects of the pressure difference and environment pressure on cavitation augmentation at the end of the injection were also investigated. Flow characteristics due to different shapes of the nozzle flow passage in axisymmetric single hole nozzles and multi hole nozzle configurations (mini-sac and VCO eight-hole nozzles) were compared with emphasis on the end of injection period.

Three-Dimensional Free Jets

1967 ◽  
Vol 71 (684) ◽  
pp. 858-859
Author(s):  
N. Rajaratnam ◽  
K. Subramanya
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Maximum Velocity ◽  
Potential Core ◽  
Free Jets ◽  
Axisymmetric Jet ◽  
Plane Jets ◽  
Velocity Decay ◽  
Different Shapes ◽  
Semi Empirical

Fairly elegant semi-empirical theories are available for predicting the turbulent diffusion of axisymmetric and plane jets. However, there are relatively few investigations on the non-axisymmetric jets, herein denoted as three-dimensional jets. The extensive investigations conducted at the Polytechnic Institute of Brooklyn on three-dimensional jets have shown that the flow field is characterised by three distinct regions; the potential core, the characteristic decay (CD) region and the axisymmetric decay (AD) region. In the CD region the velocity profiles in the direction of the minor axis are similar but the maximum velocity decay curves are different for different shapes. In the AD region the flow characteristics are similar to that of an axisymmetric jet. Yevdjevich has recently conducted another investigation on rectangular jets.

Numerical Study of Counter Jet Formed by Impinging Jets in Cross-Flow and its Effect on Mixing

2017 ◽  
Author(s):  
Thomas A. Epalle ◽  
Fabien Gaugain ◽  
Vincent Melot ◽  
Nasser Darabiha ◽  
Olivier Gicquel
Keyword(s):  
Numerical Study ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Passive Scalar ◽  
Impinging Jets ◽  
Mean Velocity ◽  
Plane Flow ◽  
Flow Mixing ◽  
Mixing Chambers

In this paper we will numerically analyse flow mixing in multiple jets in a crossflow. The system comprises a row of six radially-distributed injectors around the main pipe. The configuration represents mixing zones in industrial systems where a counter jet can be formed in the injection plane. Flow mixing can be modified as a result of geometry and injection velocities. We propose a simple model to describe the counter jet length as a function of injection flow characteristics. We also develop empirical laws to help engineers design practical test facilities. We then vary the velocity ratio to obtain both impinging and non-impinging jets in the injection plane. The focus is mainly on flow characteristics around the radial injection plane in the case of impinging jets, examining the mixing quality and efficiency by introducing a passive scalar discharge in a nitrogen flow. The mean velocity and width of the counter jet are finally analyzed by changing the injection velocities. These results are compared to those of non-impinging jets. It is found that the non-impinging jet configurations are convenient for short length mixing chambers, while the impinging ones should be considered in the case of longer mixing chambers.

Experimental investigation of the flow characteristics of small orifices and valves in water hydraulics

2002 ◽  
Vol 216 (4) ◽  
pp. 235-245 ◽  
Author(s):  
Zhu Bikai ◽  
Huang Yan ◽  
Zhang Tiehua ◽  
Li Zhuangyun
Keyword(s):  
Experimental Investigation ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Test Results ◽  
Small Opening ◽  
Aspect Ratios ◽  
Water Hydraulics ◽  
Different Shapes ◽  
Large Opening ◽  
Spool Valve

This paper describes an experimental investigation of the flow characteristics of water passing through small sharp-edged cylindrical orifices and valves of different shapes in water hydraulics. The test results using orifices with aspect ratios, l/d, of 1–15 and diameters of 0.8-3 mm show that the flow coefficients in the case of non-cavitating flow are larger than those of flow with cavitation and decrease with increase in the aspect ratio. However, the flow coefficients of flow with cavitation tend to be of constant value close to the contraction coefficient, Cc at small aspect ratios. Orifices with large aspect ratios have the effect of suppressing cavitation. Experimental results concerning the spool valve illustrate that the sharp-edged valve is less cavitation stricken at large opening than at small opening. Throttles with a triangular notch have better anticavitation ability than those with a square notch. The flow of the throttle with a square notch is significantly affected by the flow direction and the shape of the flow passage.

Structural phenomena in the growth of carbon nanotubes

1993 ◽  
Vol 51 ◽  
pp. 750-751
Author(s):  
Jun Jiao
Keyword(s):  
Carbon Nanotubes ◽  
Growth Mechanism ◽  
Carbonaceous Material ◽  
Cluster Growth ◽  
Structural Elements ◽  
Rich Variety ◽  
Different Shapes ◽  
Point To Point

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.

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