Modeling and prediction for the oxidation efficiency of magnesium sulfite in aeration tank of magnesium-based seawater exhaust gas clean system

2017 ◽  
Vol 233 (1) ◽  
pp. 164-173
Author(s):  
Quan Liu ◽  
Yimin Zhu ◽  
Tie Li ◽  
Xiaojia Tang ◽  
Weifeng Liu ◽  
...  
Keyword(s):  
Flow Field ◽  
Initial Conditions ◽  
Negative Impact ◽  
Fluid Model ◽  
Aeration Tank ◽  
Exhaust Gas ◽  
Clean System ◽  
Physics Modeling ◽  
Set Up ◽  
Oxidation Efficiency

In magnesium-based seawater exhaust gas clean system, the desulfurization by-product, magnesium sulfite (MgSO3), has a negative impact on the ecological environment, which needs to be treated to make harmless. Due to the limited space on board, the aeration oxidation method is used to convert it to magnesium sulfate. Because of the variable size, shape and flow field of aeration tank, it is difficult and expensive to design and verify the oxidation efficiency of the aeration tank by experimental method. In this work, in order to predict the oxidation efficiency accurately, RFlow, a computational fluid dynamics software, was used to analyze the flow field and MgSO3 oxidation reaction in aeration tank. The subdomain technology was adopted for physics modeling and mesh generation of the aeration tank, and the total number of meshes was 285,000. The multi-phase flow field model was set up using the multi-fluid model and dispersive k-ε turbulence model. Under the given initial conditions, the predicted oxidation efficiency was 94.2%. Compared with the results of the actual ship test, the prediction model for MgSO3 oxidation efficiency of the aeration tank is reliable.

Enhanced oxidation of MgSO3 during desulfurization by a novel spray method in magnesium-based seawater exhaust gas clean system

2017 ◽  
Vol 231 (4) ◽  
pp. 871-876
Author(s):  
Quan Liu ◽  
Meijun Sun ◽  
Tianliang Zhang ◽  
Yimin Zhu
Keyword(s):  
Oxidation Rate ◽  
Oxidation Mechanism ◽  
Aeration Tank ◽  
Exhaust Gas ◽  
Oxidation Method ◽  
Marine Diesel ◽  
Clean System ◽  
Desulfurization Process ◽  
Oxidation Efficiency ◽  
The Cost

The magnesium-based seawater exhaust gas clean system is effective in reducing sulfur dioxide emission from marine diesel engines. Oxidation of the desulfurization by-product, magnesium sulfite (MgSO3), is required for recycling. However, the oxidation efficiency is generally low in the aeration tank after the desulfurization process, making the tank volume too large for practical use on ocean vessels. In this article, we propose a novel spray oxidation method to enhance the oxidation of MgSO3 during the desulfurization process. The effects of MgSO3 content, pH and temperature on the oxidation rate were investigated. The results showed that the spray oxidation rate of MgSO3 was 1.5 order with respect to the MgSO3 concentration under both unsaturated and saturated conditions of MgSO3 solution, which is different from the aeration oxidation researches. The spray oxidation rate decreased with the increase in pH and raised slowly as the temperature increased. The MgSO3 oxidation mechanism of the spray oxidation method was analyzed and discussed in comparison with the traditional bubble aeration method. The novel spray oxidation method is effective in reducing the cost of the subsequent MgSO3 aeration oxidation process and the offprint of aeration tanks, thus is promising to be applied on ocean vessels.

Modeling and prediction of desulfurization efficiency for magnesium-based seawater exhaust gas clean system

2017 ◽  
Vol 233 (1) ◽  
pp. 325-332
Author(s):  
Quan Liu ◽  
Yimin Zhu ◽  
Xiaojia Tang ◽  
Tie Li ◽  
Weifeng Liu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Sulfur Dioxide ◽  
Flow Field ◽  
Prediction Model ◽  
Field Model ◽  
Exhaust Gas ◽  
Practical Result ◽  
Clean System ◽  
Desulfurization Efficiency

The desulfurization efficiency is a major parameter of magnesium-based seawater exhaust gas clean system, which is one of the important means to control the sulfur dioxide emission from marine diesel engines. In this work, the RFlow, a computational fluid dynamics software, was used to analyze the flow field and sulfur dioxide absorption rate in the desulfurization tower of magnesium-based seawater exhaust gas clean system. The subdomain technology was applied for physics modeling and mesh generation of the desulfurization tower, and total number of the mesh is 2.25 million. The flow field model was set up by coupling the multi-fluid model with the dispersive k-ε turbulence model. Based on flow field model, the prediction model for desulfurization efficiency of magnesium-based seawater exhaust gas clean system was programmed in user-defined module of the RFlow software, according to the two-film theory and sulfur dioxide absorption reaction equations. The simulation results predicted a desulfurization efficiency of 97.9%, which agrees well with the practical result. In order to study the effect of gas and liquid flow rate on the desulfurization efficiency, the computational fluid dynamics prediction model was applied. And the verification tests were conducted on a container vessel. Comparing the predicted results with the experimental data, the maximum error is less than 2%. It is proved that the prediction model is reliable and useful for the magnesium-based seawater exhaust gas clean system.

Work Stress and Organisational Citizenship Behaviours (OCBs) in Call Centers Employees

2015 ◽  
Vol 3 (1) ◽  
Author(s):  
Sunita ◽  
Urvashi Singh ◽  
Shalini Singh ◽  
Rajnee Sharma
Keyword(s):  
Negative Impact ◽  
Call Centers ◽  
Negative Relationship ◽  
Married Couples ◽  
Call Centre ◽  
Simple Correlation ◽  
Nuclear Families ◽  
Set Up ◽  
Stress At Work ◽  
The Relationship

The present study was conducted to examine the relationship between organisational stress and organisational citizenship behaviours (OCBs) in employees of call centers. The study also further explored as how stress at work set-up has negative impact on OCBs. A sample of 250 employees working in call centre of Gurgaon belonging to an age group of 25-30 years were selected on availability basis. All were working married couples living in nuclear families. Job stress survey (Spielberger & Vagg, 1999) and Organisational Citizenship Behaviour (Bateman & Organ, 1983) were administered. Data was analysed by using simple correlation and multiple regression. Results showed the negative relationship between organisational stress and OCBs. Results of regression analysis also exhibited the negative impact of stress on OCBs. The implications for the employees are discussed.

scholarly journals On Kaufmann's theory of the impact of the pianoforte hammer

1920 ◽  
Vol 97 (682) ◽  
pp. 99-110 ◽  
Keyword(s):  
Initial Conditions ◽  
Practical Importance ◽  
Prima Facie ◽  
Point Of View ◽  
Infinite Length ◽  
Modes Of Vibration ◽  
Rigorous Treatment ◽  
The Subject ◽  
Set Up ◽  
The Impact

The theory of the vibrations of the pianoforte string put forward by Kaufmann in a well-known paper has figured prominently in recent discussions on the acoustics of this instrument. It proceeds on lines radically different from those adopted by Helmholtz in his classical treatment of the subject. While recognising that the elasticity of the pianoforte hammer is not a negligible factor, Kaufmann set out to simplify the mathematical analysis by ignoring its effect altogether, and treating the hammer as a particle possessing only inertia without spring. The motion of the string following the impact of the hammer is found from the initial conditions and from the functional solutions of the equation of wave-propagation on the string. On this basis he gave a rigorous treatment of two cases: (1) a particle impinging on a stretched string of infinite length, and (2) a particle impinging on the centre of a finite string, neither of which cases is of much interest from an acoustical point of view. The case of practical importance treated by him is that in which a particle impinges on the string near one end. For this case, he gave only an approximate theory from which the duration of contact, the motion of the point struck, and the form of the vibration-curves for various points of the string could be found. There can be no doubt of the importance of Kaufmann’s work, and it naturally becomes necessary to extend and revise his theory in various directions. In several respects, the theory awaits fuller development, especially as regards the harmonic analysis of the modes of vibration set up by impact, and the detailed discussion of the influence of the elasticity of the hammer and of varying velocities of impact. Apart from these points, the question arises whether the approximate method used by Kaufmann is sufficiently accurate for practical purposes, and whether it may be regarded as applicable when, as in the pianoforte, the point struck is distant one-eighth or one-ninth of the length of the string from one end. Kaufmann’s treatment is practically based on the assumption that the part of the string between the end and the point struck remains straight as long as the hammer and string remain in contact. Primâ facie , it is clear that this assumption would introduce error when the part of the string under reference is an appreciable fraction of the whole. For the effect of the impact would obviously be to excite the vibrations of this portion of the string, which continue so long as the hammer is in contact, and would also influence the mode of vibration of the string as a whole when the hammer loses contact. A mathematical theory which is not subject to this error, and which is applicable for any position of the striking point, thus seems called for.

scholarly journals A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4136
Author(s):  
Clemens Gößnitzer ◽  
Shawn Givler
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Negative Impact ◽  
Operating Conditions ◽  
Engine Operation ◽  
Gas Engine ◽  
Cycle Simulation ◽  
Simulation Results ◽  
The Impact

Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier–Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are taken from a snapshot from a different cycle. Such a combination yields a new snapshot. With the combined snapshot, the simulation is continued until the end of combustion. The results obtained with combined snapshots show that the velocity field seems to have the highest impact on CCV. Turbulence intensity, quantified by the turbulent kinetic energy and turbulent kinetic energy dissipation rate, has a similar value for all snapshots. Thus, their impact on CCV is small compared to the flow field. This novel methodology is very flexible and allows investigation of the sources of CCV which have been difficult to investigate in the past.

Nanoparticle Precipitation in a T-Mixer: Coupling Experimental and Numerical Investigations of the Fluid Dynamics With the Solid Formation Processes

2006 ◽  
Author(s):  
Johannes Gradl ◽  
Florian Schwertfirm ◽  
Hans-Christoph Schwarzer ◽  
Hans-Joachim Schmid ◽  
Michael Manhart ◽  
...  
Keyword(s):  
Flow Field ◽  
Fluid Dynamic ◽  
Concentration Field ◽  
Population Balance ◽  
Mixing Process ◽  
Image Velocimetry ◽  
Modeling Material ◽  
Field Information ◽  
Set Up ◽  
3D Information

Mixing and consequently fluid dynamic is a key parameter to tailor the particle size distribution (PSD) in nanoparticle precipitation. Due to fast and intensive mixing a static T-mixer configuration is capable for synthesizing continuously nanoparticles. The flow and concentration field of the applied mixer is investigated experimentally at different flow rates by Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF). Due to the PIV measurements the flow field in the mixer was characterized qualitatively and the mixing process itself is quantified by the subsequent LIF-measurements. A special feature of the LIF set up is to detect structures in the flow field, which are smaller than the Batchelor length. Thereby a detailed insight into the mixing process in a static T-Mixer is given. In this study a CFD-based approach using Direct Numerical Simulation (DNS) in combination with the solid formation kinetics solving population balance equations (PBE) is applied, using barium sulfate as modeling material. A Lagrangian Particle Tracking strategy is used to couple the flow field information with a micro mixing model and with the classical theory of nucleation. We found that the DNS-PBE approach including macro and micro mixing, combined with the population balance is capable of predicting the full PSD in nanoparticle precipitation for different operating parameters. Additionally to the resulting PSD, this approach delivers a 3D-information about all running subprocesses in the mixer, i.e. supersaturation built-up or nucleation, which is visualized for different process variables.

Experimental Characterization of a Swirl Stabilized MGT Combustor

2015 ◽  
Author(s):  
T. O. Monz ◽  
M. Stöhr ◽  
W. O’Loughlin ◽  
J. Zanger ◽  
M. Hohloch ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Flame Stabilization ◽  
Main Stage ◽  
Exhaust Gas ◽  
Test Rig ◽  
Gas Emissions ◽  
Preheating Temperature ◽  
Exhaust Gas Emissions

A swirl stabilized MGT combustor (Turbec T100) was operated with natural gas and was experimentally characterized in two test rigs, a pressurized and optically accessible MGT test rig and an atmospheric combustor test rig. For the detailed characterization of the combustion processes, planar OH-PLIF and simultaneous 3D-stereo PIV measurements were performed in the atmospheric combustor test rig. Flow fields, reaction zones and exhaust gas emissions are reported for a range of pressure scaled MGT load points. Parameter studies on combustor inlet conditions (e.g. air preheating temperature, air and fuel mass flow rates and fuel split) were conducted in the atmospheric combustor test rig. From the parameters studies the fuel split between the pilot and the main stage and the air preheating temperature were found to have the biggest impact on the flame shape, flame stabilization and exhaust gas emissions. The measurements of the ATM test rig are compared with measurements of the pressurized MGT test rig with and without an optically accessible combustion chamber. Opened and closed conical flame and flow pattern were found in both test rigs. Reasons for the two flame and flow pattern are supposed to be the interaction of pilot stage combustion and flow field and the interaction of the dilution air with the combustion and the flow field. The results are discussed and compared with repect to a transferability of combustion characteristics from the ATM test rig to the MGT test rigs.

scholarly journals Changes And New Constraints In The Competition Rules Enforcement Due To Accession: The Perception Of The Romanian Companies

2011 ◽  
Vol 7 (4) ◽  
Author(s):  
Alina Mihaela Dima
Keyword(s):  
Competition Policy ◽  
Negative Impact ◽  
Free Market ◽  
National Level ◽  
Well Being ◽  
Business Environment ◽  
Competition Rules ◽  
Set Up ◽  
The One ◽  
The Right

Many times, in the attempt to win or to maintain an advantageous position on the market, the economic agent will use a whole arsenal of practices (inclusively and mostly from the marketing field), most of them anticompetitive, with a negative impact on the business environment, which also affects the well-being of the consumer. The policy in the field of competition is the one that defines these types of behaviour and penalizes them depending on the importance of their negative impact, by creating a complex and coherent legislative and institutional mechanism. The right enforcement of the competition policy at the national level is the key in this process, but this should be coordinated with the regional and international objectives and regulations in this field. Romania is facing a double challenge: on the one side, it had to set up a competition policy, which was almost ignored before the90s, on the other side, it had to comply, recently, with high standards in the field, as an EU candidate. Now, as a member state, the promotion of a competition culture becomes a must, along with the design of an adequate system of information and knowledge dissemination for all of those involved. The paper is based on a original and qualitative research and aims at emphasising the increased necessity of the promotion of a competition culture for the competitiveness of the Romanian business environment on the European level in the new context of accession. This will help Romanian business to face the competition challenges within a more extended single European market, as an essential issue of the free market economy status recently granted, and accordingly to the most important EU objectives set up at Lisabon to become the most competitive economy in the world up to 2010.

scholarly journals Ekologi Pohon Kluwak/Pakem (Pangium edule Reinw.) di Taman Nasional Meru Betiri, Jawa Timur

2016 ◽  
Vol 14 (1) ◽  
pp. 33
Author(s):  
N. M. Heriyanto ◽  
Endro Subiandono
Keyword(s):  
Random Sampling ◽  
National Park ◽  
Negative Impact ◽  
Sampling Procedure ◽  
Regional Office ◽  
Transect Line ◽  
Ecological Aspects ◽  
Tree Generation ◽  
Set Up ◽  
Important Value Index

<p>The ecological aspects of kluwak/pakem tree (Pangium edule Reinw) were observed at three location namely Pakeman, Sumber Salak and Sumber Gadung, Sub section II of Conservation Regional Office, Ambulu-Meru Betiri National Park, East Java in October-December 2006. Three transect line measuring 20 m x 1000 m were established accrossed the slope in which observation plots were set up by employing purposive random sampling procedure. The result showed that most of Pangium habitat was found in steep area along the river. Association around the kluwak/pakem trees includes besule trees/Chydenanthus excelsus Miers. Important Value Index (IVI) 28.5%, and wining trees/Pterocybium javanicum R. Br. (IVI 20%). However, wining trees was the most closest association with Pangium vegetation. Biophyisical information of the Pangium vegetation were as follows: 24-30oC daily temperature, 50-80% humidity, 10-65% slope, and 15-306 m altitude. The soil is Latosol with pH 5.5-6.5. Harvesting of fruit of Pangium trees by community surrounding the forest had no negative impact to the trees but this activity should be managed accordingly to avoid disturbing tree generation.</p><p> </p><p><strong>Abstrak</strong></p><p>Penelitian dilakukan pada bulan Oktober-Desember 2006 di blok Pakeman, blok Sumber Salak, dan blok Sumber Gadung Subseksi II Ambulu, Taman Nasional Meru Betiri, Jawa Timur, untuk mengetahui beberapa aspek ekologi pohon kluwak/pakem (Pangium edule Reinw.). Pengumpulan data menggunakan metode pengukuran pada jalur berpetak dengan lebar jalur 20 m dan panjang 1.000 m, jalur memotong lereng dan jumlah jalur pengamatan 3 jalur. Petak-petak penelitian ditetapkan secara sengaja dengan metode purposive sampling, di mana pengukuran dilakukan pada tempat-tempat yang terdapat pohon kluwak/pakem. Hasil penelitian menunjukkan bahwa habitat kluwak/pakem di Taman Nasional Meru Betiri banyak dijumpai di sepanjang pinggiran aliran air dan topografi agak curam. Komposisi vegetasi di sekitar pohon kluwak/pakem banyak dijumpai jenis besule (Chydenanthus excelsus Miers) dengan Indeks Nilai Penting (INP) 28,5% dan wining (Pterocybium javanicum R. Br.) dengan INP 20%. Lingkungan fisik yang berkaitan erat dengan kluwak/pakem adalah suhu antara 24-30oC, kelembaban udara 50-80%, kemiringan lahan 10-65%, dan ketinggian tempat di atas permukaan laut 15-306 m. Jenis tanah Latosol dengan tekstur geluh lempungan dengan pH 5,5-6,5. Wining merupakan jenis tumbuhan yang mempunyai asosiasi kuat dengan kluwak/pakem, yang ditunjukkan oleh nilai Indeks Ochiai mendekati nilai satu dan di lapang ditemukan secara bersama-sama dengan pohon kluwak/pakem. Pemanenan buah kluwak/pakem oleh masyarakat tidak berpengaruh buruk pada pohonnya, namun perlu dikelola dengan baik agar tidak mengganggu regenerasi.</p>

Effects of inertia and stratification in incompressible ideal fluids: pressure imbalances by rigid confinement

2013 ◽  
Vol 726 ◽  
pp. 404-438 ◽  
Author(s):  
R. Camassa ◽  
S. Chen ◽  
G. Falqui ◽  
G. Ortenzi ◽  
M. Pedroni
Keyword(s):  
Euler Equations ◽  
Initial Conditions ◽  
Numerical Algorithms ◽  
Wave Dispersion ◽  
Variable Density ◽  
Density Variation ◽  
Fluid Inertia ◽  
Time Dynamics ◽  
Long Wave ◽  
Set Up

AbstractConsequences of density stratification are studied for an ideal (Euler) incompressible fluid, confined to move under gravity between rigid lids but otherwise free to move along horizontal directions. Initial conditions that generate horizontal pressure imbalances in a laterally unbounded domain are examined. The aim is to show analytically the existence of classes of initial data for which total horizontal momentum evolves in time, even though only vertical forces act on the fluid in this set-up. A simple class of such initial conditions, leading to momentum evolution, is identified by systematic asymptotic expansions of the governing inhomogeneous Euler equations in the small-density-variation limit. These results for Euler equations are compared and confirmed with long-wave asymptotic models, which can handle arbitrary density variations and provide closed-form mathematical expressions for limiting cases. In particular, the role of wave dispersion arising from the fluid inertia is captured by the long-wave models, even for short-time dynamics emanating from initial conditions outside the models’ asymptotic range of validity. These results are compared with direct numerical simulations for variable-density Euler fluids, which further validate the numerical algorithms and the analysis.

Sign in / Sign up

Export Citation Format

Share Document