scholarly journals OPTIMALIZATION OF AFTERBURNER CHANNEL IN BIOMASS BOILER USING CFD ANALYSIS

2016 ◽  
Vol 56 (5) ◽  
pp. 379-387 ◽  
Author(s):  
Jiří Pospíšil ◽  
Martin Lisý ◽  
Michal Špiláček
Keyword(s):  
Cross Sections ◽  
Flue Gas ◽  
Air Distribution ◽  
Cfd Analysis ◽  
Mixing Process ◽  
Rectangular Duct ◽  
Biomass Boiler ◽  
Cross Section Area ◽  
Section Area ◽  
Secondary Air

This contribution presents the results of parametrical studies focused on the mixing process in a small rectangular duct within a biomass boiler. The first study investigates the influence of a local narrowing located in the central part of the duct. This narrowing works as an orifice with very simple rectangular geometry. Four different free cross sections of the orifice were considered in the center of the duct, namely 100%, 70%, 50%, 30% of free cross section area in the duct. The second study is focused on the investigation of the influence of secondary air distribution pipe diameter on the mixing process in a flue gas duct without a narrowing.

Optimization of Secondary Air Distribution in Biomass Boiler by CFD Analysis

2016 ◽  
Vol 832 ◽  
pp. 231-237 ◽  
Author(s):  
Martin Lisý ◽  
Jiří Pospíšil ◽  
Otakar Štelcl ◽  
Michal Špilaček
Keyword(s):  
Combustion Chamber ◽  
Flue Gas ◽  
Gas Flow ◽  
Air Distribution ◽  
Cfd Modelling ◽  
Biomass Boiler ◽  
Air Supply ◽  
Secondary Air ◽  
Emission Limits ◽  
The Impact

This paper deals with a use of CFD modelling for optimization of supply of secondary combustion air in the two-chamber biomass boiler combusting very wet biomass (capacity ca. 200 kW). Objective of the analyse is to observe the impact of diameter of a secondary air supply pipe and air flow velocity on mixing of the secondary air with flue gas in the combustion chamber. The numerical model of the experimental boiler was build up for subsequent utilizing of CFD computation based on finite element method. The commercial code STAR-CD was used for carried out parametrical studies. Series of calculations were carried out for four different diameters of air distribution pipes and for 3 different air velocities in distribution orifice. Quality of air dispersion in flue gas flow was assessed in the vertical cross section lead in the end of the combustion chamber. The results of calculation were verified on the experimental installation of the boiler. Influence of secondary air mixing on emission production was measured and analysed. Emissions of pollutants for recommended air distribution comply with emission limits stipulated in the most stringent class 5 according to ČSN-EN 303-5 as well as with emission limits under Regulation No. 405/2012 Sb.

scholarly journals Load bearing capacity of thin-walled rectangular and I-shaped steel sections of short both empty and concrete-filled columns

2021 ◽  
Vol 15 (58) ◽  
pp. 77-85
Author(s):  
Amor Bouaricha ◽  
Naoual Handel ◽  
Aziza Boutouta ◽  
Sarah Djouimaa
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Load Capacity ◽  
Cross Sectional ◽  
Short Columns ◽  
Cross Section Area ◽  
Section Area ◽  
Specimen Height ◽  
Steel Sections ◽  
Thin Walled

In this experimental work, strength results obtained on short columns subjected to concentric loads are presented. The specimens used in the tests have made of cold-rolled, thin-walled steel. Twenty short columns of the same cross-section area and wall thickness have been tested as follows: 8 empty and 12 filled with ordinary concrete. In the aim to determine the column section geometry with the highest resistance, three different types of cross-sections have been compared: rectangular, I-shaped unreinforced and, reinforced with 100 mm spaced transversal links. The parameters studied are the specimen height and the cross-sectional steel geometry. The registered experimental results have been compared to the ultimate loads intended by Eurocode 3 for empty columns and by Eurocode 4 for compound columns. These results showed that a concrete-filled composite column had improved strength compared to the empty case. Among the three cross-section types, it has been found that I-section reinforced is the most resistant than the other two sections. Moreover, the load capacity and mode of failure have been influenced by the height of the column. Also, it had noted that the experimental strengths of the tested columns don’t agree well with the EC3 and EC4 results.

Parametric Modeling of Transition Tube with Constant Section Area along Straight, Circular and Oblique Central Route on CATIA

2012 ◽  
Vol 619 ◽  
pp. 18-21
Author(s):  
Xiang Bao Meng ◽  
Lei Wang ◽  
Zi Jian Pan
Keyword(s):  
Cross Sections ◽  
Parametric Modeling ◽  
Phase Flow ◽  
Cross Section Area ◽  
Section Area ◽  
Micro Channels ◽  
Multi Phase Flow ◽  
Transitional Junction ◽  
Multi Phase ◽  
Constant Section

Parametric modeling of transition tubes were implemented based on constant cross section area assumption along the main central routes on CATIA software. The key objective of modeling these similar structures is to provide more geometric configuration options and modifications of micro channels for multi phase flow systems. The modeling processes were parameterized and analyzed by CATIA “Generative Shape Design” module with the help of “Parameters” and “Relations” functions. The surface models are all designed in circular cross sections that are constrained in two ways: one is perpendicular to the main central routes of the tube for planar transitional junction, and another is, perpendicular to the sub-branch central routes for oblique transitional junction three dimensionally. Next work is emphasized on numerical simulation and experimental investigation with these geometric structures in a multi phase flow system.

scholarly journals Exact Longitudinal Vibration Characteristics of Rods with Variable Cross-Sections

2011 ◽  
Vol 18 (4) ◽  
pp. 555-562 ◽  
Author(s):  
Bulent Yardimoglu ◽  
Levent Aydin
Keyword(s):  
Differential Equation ◽  
Cross Section ◽  
Cross Sections ◽  
Longitudinal Vibration ◽  
Transformation Method ◽  
Variable Cross ◽  
Cross Sectional ◽  
Cross Section Area ◽  
Section Area ◽  
Sinusoidal Functions

Longitudinal natural vibration frequencies of rods (or bars) with variable cross-sections are obtained from the exact solutions of differential equation of motion based on transformation method. For the rods having cross-section variations as power of the sinusoidal functions ofax+b, the differential equation is reduced to associated Legendre equation by using the appropriate transformations. Frequency equations of rods with certain cross-section area variations are found from the general solution of this equation for different boundary conditions. The present solutions are benchmarked by the solutions available in the literature for the special case of present cross-sectional variations. Moreover, the effects of cross-sectional area variations of rods on natural characteristics are studied with numerical examples.

scholarly journals AN EXPERIMENTAL INVESTIGATION OF SOIL LAYER COUPLING FAILURE CHARACTERISTICS ON NATURAL GRASSLAND BY PASSIVE SUBSOILER-TYPE OPENERS

2020 ◽  
pp. 49-58 ◽  
Author(s):  
Changbin He ◽  
Yong You ◽  
Decheng Wang ◽  
Hongjian Wu ◽  
Bingnan Ye
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Layer Structure ◽  
Soil Layer ◽  
Failure Characteristics ◽  
Design And Optimization ◽  
Cross Section Area ◽  
Section Area ◽  
Draft Force ◽  
Natural Grassland

Unclear soil layer coupling failure characteristics on natural grassland impeded the design and optimization of appropriate tillage tools. The coupling failure characteristics including surface disturbance and profile, disturbed cross-section area, soil over-turning rate, and coupling forces between the soil layer of natural grassland and selected passive subsoiler-type openers were investigated in this paper. Three single-shoot openers (i.e. CO, AO and WAO) and a test unit were designed, and furrow opening experiments under different working depths were conducted. Results showed that, along the passages, U-shaped disturbed cross-sections were usually created with soil-root clods overturned along the furrows. The roots were usually broken in a pulling or dragging way underground. Both disturbed cross-section area and draft force values increased with the working depth increasing linearly (R2≥0.93), contrary to the tendency of the specific draft force with the depth. Winged opener (i.e. WAO) had larger draft forces and disturbed soil layer cross-section areas than no-winged openers (i.e. AO and CO). The soil layer failure processes of the natural grassland were affected by its composite soil layer structure and the geometry parameters of the openers. The results provide original references for designing novel furrow openers applicable to improve degraded natural grassland.

A unified procedure for the vibration analysis of elastically restrained Timoshenko beams with variable cross sections

2020 ◽  
Vol 68 (1) ◽  
pp. 38-47
Author(s):  
Gang Wang ◽  
Wen L. Li ◽  
Wanyou Li ◽  
Zhihua Feng ◽  
Junfang Ni
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Vibration Analysis ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Timoshenko Beams ◽  
Unified Approach ◽  
Cross Section Area ◽  
Section Area ◽  
Elastically Restrained

A generalized analytical method is developed for the vibration analysis of Timoshenko beams with elastically restrained ends. For a beam with any variable cross section along the lengthwise direction, the finite element method is the only unified approach to handle those kinds of problems, since the analytical solutions could not be obtained by the governing equations when the cross section area and the second moment of area changing variably lengthwise. In this article, a unified approach is proposed to study the Timoshenko beam with any variable cross sections. The cross section area and second moment of area of the beam are both expanded into cosine series, which are mathematically capable of representing any variable cross section. The translational displacement and rotation of cross section are expressed in the Fourier series by adding some admissible functions which are used to handle the elastic boundary conditions with more accuracy and high convergence rate. By using Hamilton's principle, the eigenvalues and the coefficients of the Fourier series are both obtained. Some examples are presented to illustrate the excellent accuracy of this method. Analytical solutions of the vibration of the beam are achieved for different combinations of boundary conditions including classical and elastically restrained ones. The derived results can be used as benchmark solutions for testing approximate or numerical methods used for the vibration analysis of Timoshenko beams with any variable cross section.

Pressure Drop of Two-Fluid Mixtures in a Y-Typed Microchannel with Varying Cross-Section Area

2013 ◽  
Vol 284-287 ◽  
pp. 898-902
Author(s):  
Ben Ran Fu
Keyword(s):  
Pressure Drop ◽  
Pressure Distribution ◽  
Cross Sections ◽  
Cfd Simulation ◽  
Fluid Mixtures ◽  
Cross Section Area ◽  
Section Area ◽  
Theoretical Predictions ◽  
The Mean ◽  
Two Fluid

The present study investigates experimentally and numerically the single-phase flow of two-fluid mixtures (H2SO4 and NaHCO3 solutions) and of water in a Y-typed micromixer with uniform, converging, and diverging cross-sections. The mean hydraulic diameter of the three kinds of main channel is approximately 174 µm. The experimental data of pressure drop agree with the theoretical predictions and CFD simulation results within 10%. Furthermore, the pressure distribution prediction for converging and diverging microchannels is consistent with that from CFD results. The pressure falls rapidly in the diverging microchannel near the entrance and slowly near the outlet. Such the pressure distribution may enable the forward flow of a bubble in a diverging microchannel.

scholarly journals Morphological and leaf anatomical studies on Cleistogenes Serotina (L.) Keng (Poaceae)

2001 ◽  
pp. 5-13
Author(s):  
Antónia Nyakas ◽  
Edit Molnár
Keyword(s):  
Cross Sections ◽  
Grass Species ◽  
C4 Grasses ◽  
Anatomical Studies ◽  
Kranz Anatomy ◽  
Cross Section Area ◽  
Section Area ◽  
Leaf Tissues ◽  
Different Levels ◽  
New Habitats

The grass species Cleistogenes serotina (L.) Keng, generally found in the mountainous region in Hungary, has been observed in the lowlands of the Great Hungarian Plain in the last few decades. Since its first recent mention in sand habitat as well it, has been found in several locations in the interfluve between the Danube and the Tisza. In certain, sandy grasslands, the invasion of this species is considerable (e.g. near Fülöpháza the area invaded by Cleistogenes increased almost fourfold within six years). The success of invasion on new habitats is related to changes in thecharacteristics of plants comparatively studied on mountain and sand populations.We studied blades of leaves on different levels (1st, 5th and 10th) and from different biotops. Cuttings were made, with a thickness of 10-12 μm, at the middle of the blades. The cross sections were observed using a light microscope. Digitised images (DigitPlan) and survey data were arranged into a database.The leaf structure is characterised by the kranz anatomy, and a double layered bundle sheath, which is typical of the aspartate type of C4 grasses. There were significant differences only in cross section area and the number of bundles for various ages of the leaves. There were more bundles in the older leaves than in the younger ones. We did not find any difference in the ratio of tissues among leaves of different ages and sources. According to our study, the ratio of leaf tissues characteristic to species was neither significantly influenced by the biotop, nor by the age of the leaves. However, there is a difference in tissues size. Summarising the results, the species can be considered „only” as ecotypes on thedifferent studied areas. Our new result is that kranz anatomy can also be found in the leaf-sheath.This research was supported by the Hungarian Scientific Fund (OTKA), grant No. T016511 and T026346.

scholarly journals Tests of Concrete Strength across the Thickness of Industrial Floor Using the Ultrasonic Method with Exponential Spot Heads

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2118 ◽  
Author(s):  
Bohdan Stawiski ◽  
Tomasz Kania
Keyword(s):  
Compressive Strength ◽  
Cross Section ◽  
Cross Sections ◽  
Ultrasonic Method ◽  
Concrete Strength ◽  
Testing Machine ◽  
Cross Section Area ◽  
Section Area ◽  
Strength Result

The accepted methods for testing concrete are not favorable for determining its heterogeneity. The interpretation of the compressive strength result as a product of destructive force and cross-section area is burdened with significant understatements. It is assumed erroneously that this is the lowest value of strength at the height of the tested sample. The top layer of concrete floors often crumble, and the strength tested using sclerometric methods does not confirm the concrete class determined using control samples. That is why it is important to test the distribution of compressive strength in a cross-section of concrete industrial floors with special attention to surface top layers. In this study, we present strength tests of borehole material taken from industrial floors using the ultrasonic method with exponential spot heads with a contact surface area of 0.8 mm2 and a frequency of 40 kHz. The presented research project anticipated the determination of strength for samples in various cross-sections at the height of elements and destructive strength in the strength testing machine. It was confirmed that for standard and big borehole samples, it is not possible to test the strength of concrete in the top layer of the floor by destructive methods. This can be done using the ultrasonic method. After the analysis, certain types of distributions of strength across concrete floor thickness were chosen from the completed research program. The gradient and anti-gradient of strength were proposed as the new parameters for the evaluation of floor concrete quality.

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