scholarly journals Effect of secondary air on soot nucleus production in stoker-fired boilers

2013 ◽  
Vol 17 (5) ◽  
pp. 1317-1321
Author(s):  
Qing-Cheng Wang ◽  
Zhao-Chun Wu
Keyword(s):  
Temperature Field ◽  
Flow Field ◽  
Smoke Emission ◽  
Black Smoke ◽  
Nucleus Concentration ◽  
Secondary Air

Black smoke emission and soot nucleus production in a stoker-fired boiler by secondary air are studied numerically and experimentally. Temperature field, flow field, and soot nucleus concentration are predicted numerically. It reveals that the secondary air gives about 10% reduction of the soot nucleus production, and the black smoke emission is controlled evidently.

Numerical Analysis of Flow Fields and Temperature Fields in a Regenerative Heating Furnace for Steel Pipes

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
Yi Han ◽  
Feng Liu ◽  
Xin Ran
Keyword(s):  
Temperature Field ◽  
Flow Field ◽  
Flow Velocity ◽  
Gas Flow ◽  
Flow Fields ◽  
Heating Furnace ◽  
Temperature Fields ◽  
Turbulent Layer ◽  
Steel Pipes ◽  
Pipe Blanks

In the production process of large-diameter seamless steel pipes, the blank heating quality before roll piercing has an important effect on whether subsequently conforming piping is produced. Obtaining accurate pipe blank heating temperature fields is the basis for establishing and optimizing a seamless pipe heating schedule. In this paper, the thermal process in a regenerative heating furnace was studied using fluent software, and the distribution laws of the flow field in the furnace and of the temperature field around the pipe blanks were obtained and verified experimentally. The heating furnace for pipe blanks was analyzed from multiple perspectives, including overall flow field, flow fields at different cross sections, and overall temperature field. It was found that the changeover process of the regenerative heating furnace caused the temperature in the upper part of the furnace to fluctuate. Under the pipe blanks, the gas flow was relatively thin, and the flow velocity was relatively low, facilitating the formation of a viscous turbulent layer and thereby inhibiting heat exchange around the pipe blanks. The mutual interference between the gas flow from burners and the return gas from the furnace tail flue led to different flow velocity directions at different positions, and such interference was relatively evident in the middle part of the furnace. A temperature “layering” phenomenon occurred between the upper and lower parts of the pipe blanks. The study in this paper has some significant usefulness for in-depth exploration of the characteristics of regenerative heating furnaces for steel pipes.

scholarly journals Feasibility Study on Oil Droplet Flow Investigations Inside Aero Engine Bearing Chambers: PDPA Techniques in Combination With Numerical Approaches

1995 ◽  
Author(s):  
A. Glahn ◽  
M. Kurreck ◽  
M. Willmann ◽  
S. Wittig
Keyword(s):  
Numerical Methods ◽  
Flow Field ◽  
Flow Analysis ◽  
Field Analysis ◽  
Oil Droplet ◽  
Droplet Flow ◽  
Aero Engine ◽  
Secondary Air ◽  
Numerical Approaches ◽  
Engine Bearing

The present paper deals with oil droplet now phenomena in aero engine bearing chambers. An experimental investigation of droplet sizes and velocities utilizing a Phase Doppler Particle Analyzer (PDPA) has been performed for the first time in bearing chamber atmospheres under real engine conditions. Influences of high rotational speeds are discussed for individual droplet size classes. Although this is an important contribution to a better understanding of the droplet flow impact on secondary air/oil system performance, an analysis of the droplet flow behaviour requires an incorporation of numerical methods because detailed measurements as performed here suffer from both strong spatial limitations with respect to the optical accessibility in real engine applications and constraints due to the extremely time consuming nature of an experimental flow field analysis. Therefore, further analysis is based on numerical methods. Droplets characterized within the experiments are exposed to the flow field of the gaseous phase predicted by use of our well-known CFD code EPOS. The droplet trajectories and velocities are calculated within a Lagrangian frame of reference by forward numerical integration of the particle momentum equation. This paper has been initiated rather to show a successful method of bearing chamber droplet flow analysis by a combination of droplet sizing techniques and numerical approaches than to present field values as a function of all operating parameters. However, a first insight into the complex droplet flow phenomena is given and specific problems in bearing chamber heat transfer are related to the droplet flow.

Effects of U-Shape Inner Cooler on Flow and Solidification of Molten Steel in Slab Continuous Casting Mold

2011 ◽  
Vol 291-294 ◽  
pp. 423-427
Author(s):  
Yan Juan Jin ◽  
Xiao Chao Cui ◽  
Zhu Zhang
Keyword(s):  
Fluid Dynamics ◽  
Temperature Field ◽  
Flow Field ◽  
Continuous Casting ◽  
Molten Steel ◽  
Continuous Casting Mold ◽  
Slab Continuous Casting ◽  
Cooling Technology ◽  
Steel Flow

An inner-outer coupled cooling technology of molten steel for 1240×200mm slab continuous casting, that is to set an inner cooler—U shape pipes in the mold, is put forward in order to enhance the efficiency of transmitting heat and improve inner structure of billet. The flow status and solidification status of molten steel under coupling flow field and temperature field in inner-outer coupled cooling mold are simulated by using fluid dynamics software, and compare with those in traditional mold. It is found that setting inner cooler in the mold can make molten steel flow status even, which is favorable to floating up of the inclusion, quickening the solidification of steel liquid and improving the quality of billet.

Experimental Investigation of Turbine Stage Flow Field and Performance at Varying Cavity Purge Rates and Operating Speeds

2016 ◽  
Author(s):  
Johan Dahlqvist ◽  
Jens Fridh
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
High Speed ◽  
Control Volume ◽  
Spatial Average ◽  
Turbine Stage ◽  
Wide Range ◽  
Annulus Flow ◽  
Purge Flow ◽  
Secondary Air

The aspect of hub cavity purge has been investigated in a high-pressure axial low-reaction turbine stage. The cavity purge is an important part of the secondary air system, used to isolate the hot main annulus flow from cavities below the hub level. A full-scale cold-flow experimental rig featuring a rotating stage was used in the investigation, quantifying main annulus flow field impact with respect to purge flow rate as it was injected upstream of the rotor. Five operating speeds were investigated of which three with respect to purge flow, namely a high loading case, the peak efficiency, and a high speed case. At each of these operating speeds, the amount of purge flow was varied across a very wide range of ejection rates. Observing the effect of the purge rate on measurement plane averaged parameters, a minor outlet swirl decrease is seen with increasing purge flow for each of the operating speeds while the Mach number is constant. The prominent effect due to purge is seen in the efficiency, showing a similar linear sensitivity to purge for the investigated speeds. An attempt is made to predict the efficiency loss with control volume analysis and entropy production. While spatial average values of swirl and Mach number are essentially unaffected by purge injection, important spanwise variations are observed and highlighted. The secondary flow structure is strengthened in the hub region, leading to a generally increased over-turning and lowered flow velocity. Meanwhile, the added volume flow through the rotor leads to higher outlet flow velocities visible in the tip region, and an associated decreased turning. A radial efficiency distribution is utilized, showing increased impact with increasing rotor speed.

Flow Field and Temperature Field in GaN-MOCVD Reactor Based on Computational Fluid Dynamics Modeling

2018 ◽  
Vol 35 (9) ◽  
pp. 098101
Author(s):  
Shu-Zhe Mei ◽  
Quan Wang ◽  
Mei-Lan Hao ◽  
Jian-Kai Xu ◽  
Hong-Ling Xiao ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Temperature Field ◽  
Flow Field ◽  
Dynamics Modeling ◽  
Computational Fluid Dynamics Modeling ◽  
Mocvd Reactor

Experimental Investigation of Turbulence Structure in a Three-Nozzle Combustor

2007 ◽  
Author(s):  
Benjamin Boehm ◽  
Andreas Dreizler ◽  
Markus Gnirss ◽  
Cameron Tropea ◽  
Jens Findeisen ◽  
...  
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Air Entrainment ◽  
Pollutant Emissions ◽  
Laser Doppler Velocimeter ◽  
Velocity Signal ◽  
Size And Shape ◽  
Recirculation Zones ◽  
Turbulent Flow Field ◽  
Secondary Air

Proper mixing of fuel, primary and secondary air is a major issue to optimize engine performance in terms of efficiency and pollutant emissions. The underlying turbulent flow field determines these mixing processes. Most experimental and numerical investigations are performed in single nozzle combustors for reasons of optical accessibility and simplicity. The focus of the present study is to compare the variation of the non-reacting turbulent flow field for the case of single-nozzle and three-nozzle operation. In addition, the influence of secondary air entrainment is investigated. The flow configuration is based on commercial geometries. Using a two component laser Doppler velocimeter (LDV) the mean and fluctuating velocities of all three components, as well as two Reynolds-stress components were measured. The autocorrelation function and spectral distributions of the fluctuating velocity signal clearly revealed coherent fluid motions. These observations, together with high speed-flow visualisations indicate a precessing vortex core (PVC). An additional lower frequency for all three nozzles in operation revealed a pulsation of the recirculation zones. A major result of this investigation is that the size and shape of the internal recirculation zones were significantly influenced by operation of adjacent nozzles. Furthermore the generation of PVCs were augmented in the three-nozzle configuration. The additional secondary air entrainment interacts with the primary flow, changing the size and shape of the recirculation zone and affecting the low frequency pulsation.

scholarly journals Numerical Simulation of Temperature and Fluid Fields in Solidification Process of Ferritic Stainless Steel under Vibration Conditions

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 174
Author(s):  
Wenli Wang ◽  
Jing Chen ◽  
Miaomiao Li ◽  
Along Wang ◽  
Mengyao Su
Keyword(s):  
Stainless Steel ◽  
Temperature Field ◽  
Flow Field ◽  
Ferritic Stainless Steel ◽  
Stokes Equations ◽  
Solidification Process ◽  
Crystal Formation ◽  
Positive Temperature ◽  
Vibration Direction ◽  
Casting Mold

A three-dimensional model of a circular casting mold with a vibrating nucleus generator was established, and the characteristics of temperature and flow fields during the solidification process of ferritic stainless steel Cr17 in the casting mold were analyzed using finite element and finite difference methods. A standard k-ε turbulent current model was adopted to simulate the temperature field, and a standard k-ε model in Reynolds-averaged Navier–Stokes equations (RANS) was employed to deal with the flow field. The temperature field diffuses outward with a positive temperature gradient. Low degrees of undercooling can prevent solidified shells from forming rapidly on the surface of the nucleus generator. The temperature perpendicular to the direction of vibration is lower than that in the direction of vibration. The flow field exhibits a heart-shaped distribution and spreads gradually outward. The uniform distribution of grains can be achieved at three different frequencies of vibration. The results show that the degree of undercooling affects the distribution of the temperature field while the frequency of vibration affects the flow field significantly. Under the conditions of undercooling of 540 K and vibration frequency of 1000 Hz, the region perpendicular to the vibration direction of the nucleus generator is the optimum area for equiaxed crystal formation.

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