CFD Air Flow Channel Optimization for a Low NOx Operation of a Big Steam Boiler

2007 ◽  
Author(s):  
Tudor I. Prisecaru ◽  
Elena Popa ◽  
Malina Mihaela Prisecaru
Keyword(s):  
Pressure Drop ◽  
Complex Problem ◽  
Airflow Rate ◽  
Nox Emissions ◽  
Steam Boiler ◽  
Scaled Model ◽  
Air Inlet ◽  
Steam Boilers ◽  
The Subject ◽  
Air Channels

One of the Romanian big power plant (Turceni) of 2400 MWe installed power has seven Benson boilers of 1035 t/h each, using Romanian pulverized lignite. Until 2008, every one of them has to be revamped in order to emit less than 500 mg/Nm3 of NOx at full load and 6% oxygen content in the flue gas. The problem has been very complex due to the fact that all these steam boilers have been commissioned since 1968, without any design preparation concerning low NOx emissions. Step by step, all the technological measures have been performed, so the burning process of the Romanian low heat power lignite, has been able to produce low NOx emissions by the help of supplementary stages of air injections. The last problem and the subject of the presented paper, occurred regarding the possibility to inject enough and equal airflow rate through sixteen nozzles before the end of the boiler’s furnace. The complexity of this problem consisted not only in a lot of technical constraints concerning to the starting place of the air pipes, but also to the path of the pipes (with very big dimensions) and to a very low influence in pressure drop losses towards the existent air ducts. A special supplementary problem has been that one to create the simplest shape of the air inlet elbow from the main existent air ducts, in order to suck the strictly necessary airflow rate at the lowest possible pressure drop loss. Due to the fact that the boiler’s dimensions are too big to use only one air pipe toward the nozzles, two air manifolds are considered starting from two main different air ducts and feeding eight nozzles each; this fact has complicated the task further, in order to balance the airflow rate inside the two manifolds. This complex problem has been solved by the help of CFD Fluent code and has been considered also the subject of one of the team member’s PhD dissertation. Special meshing techniques have been used in order to optimize the cells’ number. For CFD results validation a special 1:50 transparent scaled model of the furnace has been constructed and performed using a laser — Doppler anemometer to determine the airflow rate and velocity, inside the air channels and at the nozzles’ exits to the furnace.

URGENSI MANAJEMEN DALAM PENGEMBANGAN AKTIVITAS DAKWAH

1970 ◽  
Vol 10 (2) ◽  
pp. 278-291
Author(s):  
Wahyu Budiantoro
Keyword(s):  
Public Life ◽  
Complex Problem ◽  
Good Management ◽  
The Subject

Da’wah in practical terms, always in touch with the community. Therefore requires a specific set of supporters in achieving its objectives, namely the setting or the good management and direction. In missionary activity there will be a very complex problem, if no good management, systematic, and purposeful. Implementation of propaganda will work effectively and efficiently when it first be able to identify the problems faced by the community. Then, on the basis of control of the situation and conditions for propaganda, formulate an appropriate plan. The dynamics of the problem requires people with a variety of actors preaching able to devise a proper plan-as the basis of a movement dakwah-, and arrange and organize the subject of preaching in a certain propaganda units. To realize and ground the teachings of Islam in public life, the propaganda must be properly managed, to meet the needs of society. Dakwah dalam tataran praktis, selalu berhubungan dengan masyarakat. Oleh karenanya membutuhkan seperangkap pendukung dalam mencapai tujuan, yaitu pengaturan atau manajemen yang baik dan terarah. Dalam aktivitas dakwah akan timbul masalah yang sangat kompleks, apabila tidak dilakukan manajemen yang baik, sistematis, dan terarah. Penyelenggaraan dakwah akan berjalan dengan efektif dan efisien apabila terlebih dahulu dapat mengidentifikasi masalah-masalah yang tengah dihadapi oleh masyarakat. Kemudian, atas dasar pengendalian situasi dan kondisi tempat untuk dakwah, disusunlah suatu rencana yang tepat. Dinamika masyarakat dengan berbagai problemnya mengharuskan para pelaku dakwah mampu menyusun rencana yang tepat –sebagai dasar dari sebuah gerakan dakwah, dan mengatur dan mengorganisir subjek dakwah ke dalam kesatuankesatuan dakwah tertentu. Untuk mewujukan dan membumikan ajaran-ajaran Islam dalam kehidupan masyarakat, maka dakwah harus dikelola dengan baik, untuk memenuhi kebutuhan masyarakat.

scholarly journals Heat Enhancement Effectiveness Using Multiple Twisted Tape in Rectangular Channels

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 188
Author(s):  
M. Ziad Saghir ◽  
Ayman Bayomy ◽  
Md Abdur Rahman
Keyword(s):  
Pressure Drop ◽  
Heat Removal ◽  
Energy System ◽  
Twisted Tape ◽  
Heat Exchanger Design ◽  
Twisted Tapes ◽  
Rectangular Channels ◽  
Flow Through ◽  
The Subject ◽  
Energy Coefficient

Heat enhancement and heat removal have been the subject of considerable research in the energy system field. Flow-through channels and pipes have received much attention from engineers involved in heat exchanger design and construction. The use of insert tape is one of many ways to mix fluids, even in a laminar flow regime. The present study focused on the use of different twisted tapes with different pitch-to-pitch distances and lengths to determine the optimum design for the best possible performance energy coefficient. The results revealed that twisted tape of one revolution represented the optimal design configuration and provided the largest Nusselt number. The length of the tape played a major role in the pressure drop. The results revealed that the insertion of a shorter twisted tape can create mixing while minimizing the changes in the pressure drop. In particular, the best performance evaluation criterion is found for a short tape located towards the exit of the channel. The highest performance energy coefficient was obtained for the half-twisted tape for a Reynolds number varying between 200 and 600.

A Method to Design Shell-Side Pressure Drop Constrained Tubular Heat Exchangers

1977 ◽  
Vol 99 (3) ◽  
pp. 441-448 ◽  
Author(s):  
K. P. Singh ◽  
M. Holtz
Keyword(s):  
Pressure Drop ◽  
Heat Exchangers ◽  
Solution Procedure ◽  
Design Guidelines ◽  
Solution Technique ◽  
Nuclear Heat ◽  
Side Pressure ◽  
Flow Induced Vibrations ◽  
The Subject ◽  
Shell And Tube

In shell and tube heat exchangers, the triple segmental baffle arrangement has been infrequently used, even though the potential of this baffle system for high thermal effectiveness with low pressure drop is generally known. This neglect seems to stem from the lack of published design guidelines on the subject. Lately, however, with the rapid growth in the size of nuclear heat exchangers, the need to develop unconventional baffling pattern has become increasingly important. A method to effectively utilize the triple segmental concept to develop economical designs is presented herein. The solution technique given in this paper is based on a flow model named “Piecewise Continuous Cosine Model.” The solution procedure easily lends itself to detailed analysis to determine safety against flow-induced vibrations.

Full-Scale Demonstration of Surface-Stabilized Fuel Injectors for Sub-Three ppm NOx Emissions

2004 ◽  
Author(s):  
Steven J. Greenberg ◽  
Neil K. McDougald ◽  
Leonel O. Arellano
Keyword(s):  
Pressure Ratio ◽  
Full Scale ◽  
Low Flow ◽  
Stable Operation ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Fuel Injectors ◽  
Air Inlet ◽  
Radial Profiles ◽  
Developed Surface

ALZETA Corporation has developed surface-stabilized fuel injectors for use with lean premixed combustors which provide extended turndown and ultra-low NOx emission performance. These injectors use a patented technique to form interacting high-flow and low-flow flame zones immediately above a selectively-perforated porous metal surface. This allows stable operation at low reaction temperatures. This technology has been given the product name nanoSTAR™. Previous work involved the development of nanoSTAR technology from the proof-of-concept stage to prototype testing. Rig testing of single injectors and of two injectors simulating a sector of an annular combustion liner have been completed for pressure ratios up to 17 and combustion air inlet temperatures up to 700 K (800°F). This paper presents results from the first ever full-scale demonstration of surface-stabilized fuel injectors. An annular combustion liner, fitted with twelve nanoSTAR injectors was successfully tested up to a pressure ratio of 12 and combustion air inlet temperature of 700 K (800°F). NOx emissions were 2 ppm with CO emissions of 3 ppm both corrected to 15% O2. The combustion system exhibited excellent temperature uniformity around the annular combustor outlet with a maximum pattern factor of 0.16 and engine-appropriate radial profiles.

Availability Analysis of a Steam Boiler in Textile Process Industries Using Failure and Repair Data: A Case Study

2020 ◽  
Author(s):  
Suyog Patil ◽  
Anand Bewoor ◽  
Rajkumar Patil
Keyword(s):  
Preventive Maintenance ◽  
Water System ◽  
Feed Water ◽  
Steam Boiler ◽  
Combustion System ◽  
Blow Down ◽  
Process Industries ◽  
Availability Analysis ◽  
Steam Boilers ◽  
Ram Analysis

Abstract The demand of steam in process industries is increasing rapidly, and this demand can be met by increasing the capacity utilization of steam boilers. Many of the process industries depend on industrial steam boilers as a vital component for their operation. The availability of the boiler can be improved by identifying critical mechanical sub-systems/components concerning failure frequency, reliability, and maintainability and minimizing their likelihood of occurrences. The selection of appropriate technique for data collection and reliability analysis is essential. The time between failure (TBF) and time to repair (TTR) of all components and sub-systems were collected to carry out Reliability, Availability and Maintainability (RAM) analysis. The best-fit distribution and distribution parameters were calculated using ReliaSoft software Weibull++10 after performing trend testing. The preventive maintenance intervals of all components and sub-systems and the availability of the system were evaluated. The analysis reveals that the combustion system, feed-water system, and blow-down system are the critical sub-systems from a reliability perspective and are still the biggest reasons for the boiler downtime. The research study also showed that TTR was longer for the combustion system than the other sub-systems, and thus, to enhance its availability, it is suggested that maintenance resources should be allocated at the appropriate moment to the combustion system. The study also shows the usage of RAM analysis in deciding the preventive maintenance intervals of components/sub-systems of the boiler. It also provides a reference for the preparation of the maintenance plan for the boiler system.

Experimental Analysis of an Air-to-Air Heat Exchanger for Use in a Refrigeration Brayton Cycle

Volume 3 ◽  
2004 ◽  
Author(s):  
Alireza Kargar ◽  
Mohammad H. Hosni ◽  
Steve Eckels ◽  
Tomas Gielda
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Removal Rate ◽  
Experimental Results ◽  
Airflow Rate ◽  
Brayton Cycle ◽  
Moisture Removal ◽  
Research Project ◽  
Cycle System ◽  
Automotive Air Conditioning

The refrigeration Brayton cycle, which has been used extensively in various industries, has an excellent potential for use in automotive air conditioning applications. However, the air-cycle system has a couple of drawbacks including fog generation and low cycle efficiency. In this research project, an air-to-air heat exchanger called a ‘mixer’ is designed and used at the outlet of a refrigeration Brayton cycle. The primary function of the mixer is to remove moisture from the secondary warm airflow into the system. Successful moisture removal from the secondary airflow results in achieving the second function of fog dissipation from the primary cold airflow. In order for the system to perform appropriately, the moisture removal rate must be kept at the highest possible rate. The experimental results from this research project reveal that to enhance moisture removal rate, one may either increase the primary cold airflow rate, decrease the secondary warm airflow rate, or the combination of the above airflow adjustments. Furthermore, based on experimental results, one may speculate that there is an optimum point in decreasing the secondary airflow rate. However, in increasing the primary airflow rate, one must be aware of the pressure drop through the cold side of the mixer as the higher pressure drop results in higher power consumption for the Brayton cycle. It is important to point out that appropriate levels of the primary and secondary airflows impacts the mixer effectiveness, and that for a constant cold airflow rate, decreasing the warm airflow rate below the cold airflow rate results in higher effectiveness.

Active Air Control System Development Using Charge Air Integrated Manifold Engine Numerical Simulation (CAIMENS)

2007 ◽  
Author(s):  
Diana K. Grauer ◽  
Kirby S. Chapman ◽  
Ali Keshavar
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Flow Rate ◽  
Pressure Wave ◽  
Equivalence Ratio ◽  
Peak Pressure ◽  
Intake Manifold ◽  
Airflow Rate ◽  
Engine System ◽  
The Impact

The natural gas transmission industry integrates turbochargers into the engine system to strategically increase airflow for the purpose of decreasing pollutant emissions, such as Nitrogen Oxide (NOX). Regulations are expected to be tightened in the coming years, forcing transmission companies to look past turbochargers for compliance. The solution to further decreasing emissions lies not in further retrofit, but focusing on the physics of the current system. The flow rate physics of the intake and exhaust manifolds impede equal distribution of air from the turbocharger to each cylinder. Imbalance in airflow creates a discontinuity in the trapped equivalence ratio from cylinder to cylinder. The trapped equivalence ratio is directly proportional to NOX production and a function of the fuel flow rate, airflow rate, and, in two-stroke cycle engines, the scavenging efficiency. Only when these three characteristics are balanced cylinder to cylinder will the combustion and the NOX production in each cylinder be equal. The engine NOX production will be disproportionately high if even one cylinder operates less lean relative to the other cylinders. Balancing the NOX production between cylinders can lower the overall NOX production of the engine. This paper reports on an investigation into the transient, compressible flow physics that impact the trapped equivalence ratio. A comprehensive, variable geometry, multi-cylinder Turbocharger-Reciprocating Engine Computer Simulation (T-RECS) has been developed to illustrate the effect of airflow imbalance on an engine. A new model, the Charge Air Integrated Manifold Engine Numerical Simulation (CAIMENS), is a manifold flow model coupled with the T-RECS engine processor that uses an integrated set of fundamental principles to determine the crank angle-resolved pressure, temperature, burned and unburned mass fractions, and gas exchange rates for the cylinder. CAIMENS has the ability to show the transient impact of one cylinder firing on each successive cylinder. The pulsation model also describes the impact of manifold pressure drop on in-cylinder peak pressure and the pressure wave introduced to the intake manifold by uncovering the intake ports. CAIMENS provides the information necessary to quantify the impact of airflow imbalance, and allows for the visualization of the engine system before and after airflow correction. The model shows that not only does the manifold pressure drop have a significant impact on the in-cylinder peak pressure, but it also has an impact on the pressure wave introduced to the intake manifold as the ports are opened. Also, each cylinder has a considerable impact on the airflow into each successive cylinder.

The Pathogenesis of Anaërobic Microbic Infections in the Major and Minor Psychoses, with Control Cases

1932 ◽  
Vol 78 (320) ◽  
pp. 12-95 ◽  
Author(s):  
W. M. Ford-Robertson
Keyword(s):  
Mental Disorders ◽  
Complex Problem ◽  
Chronic Infections ◽  
The Past ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship

The subject of this thesis is the outcome of what might be termed a hereditary interest in the complex problem of the relationship of chronic infections to the psychoses and allied mental disorders. Circumstances enabled me, while still a student, to undertake very humbly the continuation of my father's researches in the Scottish Asylums' Laboratory at a point where his illness and death might have proved the closing of a long and arduous chapter. That this would have been so is, as far as I know, borne out by the fact that up to the present no work directly bearing on his later bacteriological studies has been published. The researches I have undertaken during the past six years have been an attempt to elucidate more clearly what exactly are the bacteriological factors at work, and, further, in what manner they attack the economy generally, and with what result. In my endeavour to verify and extend Ford-Robertson's views I have been singularly fortunate.

Design Improvement Survey for NOx Emissions Reduction of a Heavy-Duty Gas Turbine Partially Premixed Fuel Nozzle Operating With Natural Gas: Experimental Campaign

2015 ◽  
Author(s):  
Matteo Cerutti ◽  
Roberto Modi ◽  
Danielle Kalitan ◽  
Kapil K. Singh
Keyword(s):  
Pressure Drop ◽  
Natural Gas ◽  
Gas Turbine ◽  
Pollutant Emissions ◽  
Nox Emissions ◽  
Heavy Duty ◽  
Fuel Nozzle ◽  
Partially Premixed ◽  
Heavy Duty Gas Turbine ◽  
The Impact

As government regulations become increasingly strict with regards to combustion pollutant emissions, new gas turbine combustor designs must produce lower NOx while also maintaining acceptable combustor operability. The design and implementation of an efficient fuel/air premixer is paramount to achieving low emissions. Options for improving the design of a natural gas fired heavy-duty gas turbine partially premixed fuel nozzle have been considered in the current study. In particular, the study focused on fuel injection and pilot/main interaction at high pressure and high inlet temperature. NOx emissions results have been reported and analyzed for a baseline nozzle first. Available experience is shared in this paper in the form of a NOx correlative model, giving evidence of the consistency of current results with past campaigns. Subsequently, new fuel nozzle premixer designs have been investigated and compared, mainly in terms of NOx emissions performance. The operating range of investigation has been preliminarily checked by means of a flame stability assessment. Adequate margin to lean blow out and thermo-acoustic instabilities onset has been found while also maintaining acceptable CO emissions. NOx emission data were collected over a variety of fuel/air ratios and pilot/main splits for all the fuel nozzle configurations. Results clearly indicated the most effective design option in reducing NOx. In addition, the impact of each design modification has been quantified and the baseline correlative NOx emissions model calibrated to describe the new fuel nozzles behavior. Effect of inlet air pressure has been evaluated and included in the models, allowing the extensive use of less costly reduced pressure test campaigns hereafter. Although the observed effect of combustor pressure drop on NOx is not dominant for this particular fuel nozzle, sensitivity has been performed to consolidate gathered experience and to make the model able to evaluate even small design changes affecting pressure drop.

The Analysis of Leakage in a Twin Screw Compressor and its Application to Performance Improvement

1995 ◽  
Vol 209 (2) ◽  
pp. 125-136 ◽  
Author(s):  
J S Fleming ◽  
Y Tang
Keyword(s):  
Analytical Techniques ◽  
Complex Problem ◽  
Screw Compressor ◽  
Leakage Path ◽  
Compression Cycle ◽  
Compressor Design ◽  
Twin Screw ◽  
Compressor Performance ◽  
The Subject ◽  
Fluid Behaviour

The performance of a helical screw compressor is influenced more by the internal gas leakages than by any other thermo-fluid aspect of its behaviour. Six separate types of leakage path can be identified. Only the cusp blow holes have a constant geometry; every other path has a geometry and resistance to flow which varies (periodically) in a manner unique to it. The pressure difference driving the gas along a leakage path also varies (periodically) and does so in a manner that is not the same for every leakage path. This is quite obviously a complex problem requiring insight in modelling the thermo-fluid behaviour and the solution of a large number of simultaneous equations. The distribution of leakage through the various leakage paths within the machine is important for the improvement of the compressor performance. A method of determining the aggregate leakage through each path individually over a complete compression cycle is required to enable this study to be conducted. The authors have constructed a mathematical model of the complete compressor thermofluid process which is suitable for this purpose, its macropredictions having been verified against measured data derived from a test compressor. The nature of its micropredictions and their verification, that is for each leakage path, are the subject of the paper proposed here. Analytical techniques are proposed and experimental methods are discussed. The influence of different rotational speeds on the leakage is considered. Also discussed is the manner in which the leakage distribution prediction could be used to optimize a compressor design.

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