Model-Based Analysis of Transient Behavior of Large Scale CFB Boilers

2003 ◽  
Author(s):  
Ari Kettunen ◽  
Timo Hyppa¨nen ◽  
Ari-Pekka Kirkinen ◽  
Esa Maikkola
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Model Parameters ◽  
Air Flow Rate ◽  
Process Data ◽  
Cfb Boiler ◽  
Flow Rates ◽  
Load Change ◽  
Secondary Air

The main objective of this study was to investigate the load change capability and effect of the individual control variables, such as fuel, primary air and secondary air flow rates, on the dynamics of large-scale CFB boilers. The dynamics of the CFB process were examined by dynamic process tests and by simulation studies. A multi-faceted set of transient process tests were performed at a commercial 235 MWe CFB unit. Fuel reactivity and interaction between gas flow rates, solid concentration profiles and heat transfer were studied by step changes of the following controllable variables: fuel feed rate, primary air flow rate, secondary air flow rate and primary to secondary air flow ratio. Load change performance was tested using two different types of tests: open and closed loop load changes. A tailored dynamic simulator for the CFB boiler was built and fine-tuned by determining the model parameters and by validating the models of each process component against measured process data of the transient test program. The know-how about the boiler dynamics obtained from the model analysis and the developed CFB simulator were utilized in designing the control systems of three new 262 MWe CFB units, which are now under construction. Further, the simulator was applied for the control system development and transient analysis of the supercritical OTU CFB boiler.

Plug Flow of Coarse Particles in a Horizontal Pipe

1982 ◽  
Vol 104 (2) ◽  
pp. 198-206 ◽  
Author(s):  
Y. Tsuji ◽  
Y. Morikawa
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Air Flow ◽  
Plug Flow ◽  
Packed Bed ◽  
Coarse Particles ◽  
Air Flow Rate ◽  
Horizontal Pipe ◽  
Main Pipe ◽  
Secondary Air

Plug flow of coarse particles was investigated experimentally in a horizontal pipe, in which a sub-pipe for secondary air injection was installed. Measurements were made about the plug motion, pressure drop, and transportation properties, and the roles of the main and sub-pipe air flow were clarified. The main air flow increases the number of plugs, while the sub-pipe air flow increases the plug velocity. The higher the main pipe air flow rate, the more regular the motion. The height of a stationary layer of deposited particles, which is built on the bottom of the main pipe, decreases with increasing the sub-pipe air flow rate. The pressure drop in the moving plug is quantitatively much smaller than that in the stationary packed bed of same particles.

Coordinated control of fuel flow rate and air flow rate of a supersonic heat-airflow simulated test system

2020 ◽  
Vol 124 (1278) ◽  
pp. 1170-1189
Author(s):  
C. Cai ◽  
L. Guo ◽  
J. Liu
Keyword(s):  
Flow Rate ◽  
Control Algorithm ◽  
Air Flow ◽  
Coordinated Control ◽  
Test System ◽  
Gas Temperature ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Fuel Flow ◽  
Simulated Test

ABSTRACTThe gas temperature of the supersonic heat airflow simulated test system is mainly determined by the fuel and air flow rates which enter the system combustor. In order to realise a high-quality control of gas temperature, in addition to maintaining the optimum ratio of fuel and air flow rates, the dynamic characteristics of them in the combustion process are also required to be synchronised. Aiming at the coordinated control problem of fuel and air flow rates, the mathematical models of fuel and air supply subsystems are established, and the characteristics of the systems are analysed. According to the characteristics of the systems and the requirements of coordinated control, a fuzzy-PI cross-coupling coordinated control strategy based on neural sliding mode predictive control is proposed. On this basis, the proposed control algorithm is simulated and experimentally studied. The results show that the proposed control algorithm has good control performance. It cannot only realise the accurate control of fuel flow rate and air flow rate, but also realise the coordinated control of the two.

A Study of the Flow Field in a Model Rotor-Stator Disk Cavity

1999 ◽  
Author(s):  
R. P. Roy ◽  
S. Devasenathipathy ◽  
G. Xu ◽  
Y. Zhao
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Air Flow ◽  
Core Region ◽  
Air Flow Rate ◽  
The Core ◽  
Rotor Disk ◽  
Secondary Air ◽  
Radial Outflow ◽  
Circumferential Pressure

Experimental and computational studies of the turbulent flow field in a model gas turbine disk cavity have been carried out. The experiments were performed in a rig which features a rotor disk-stator disk configuration with stator vanes, rotor blades, and rim discouragers with axial overlap. Particle Image Velocimetry was used to map the flow field in the cavity at three positions along the axial gap between the disks for various mainstream and secondary air flow rates, and rotor speeds. Static pressure distribution in the cavity at the stator disk and the circumferential distribution of the same at the mainstream passage outer shroud were measured. A recirculation region developed radially inboard in the disk cavity where a strong radial outflow was found close to the rotor disk and a weak radial inflow near the stator disk. This is the source region where the rotation of the core fluid is minimal, its radial extent increasing with the secondary air flow rate. Radially outboard, in the core region, the flow was rotation-dominated except when the secondary air flow rate was high. The peak-to-peak amplitude of the circumferential pressure asymmetry in the mainstream flow path increased as the square of the main air flow rate, attained its maximum value at the stator vane exit, and decreased rapidly downstream. For the experiments performed, no circumferential pressure asymmetry could be found in the disk cavity, even near its rim. The rotating fluid in the core region of the cavity gave rise to an adverse radial pressure gradient, its magnitude increasing as the secondary air flow rate decreased. This feature can facilitate ingress of mainstream gas into the cavity. Concurrently with the experiments, the flow field was simulated numerically using the commercial CFD code FLUENT/UNS. The agreement between the measurements and the computed results is generally good.

scholarly journals POLYMER WASTES’ FLOTATION SEPARATION RESEARCH RESULTS

2020 ◽  
Vol 6 (444) ◽  
pp. 50-58
Author(s):  
А. Volnenko ◽  
◽  
А. Leudanski ◽  
Y. Apimakh ◽  
B. Korganbayev ◽  
...  
Keyword(s):  
Liquid Layer ◽  
Flow Rate ◽  
Air Flow ◽  
Liquid Temperature ◽  
Air Flow Rate ◽  
Flotation Process ◽  
Flow Rates ◽  
Research Results ◽  
Air Bubble ◽  
Plastic Wastes

For separation of plastic wastes (polyamide (PA), acrylonitrile butadiene styrene (ABS) and polystyrene (PS), a flotation method is proposed. Using this method, the effect of concentration of surface-active substances (surfactants), which were used as polidocanol, sulphanole and a mixture of surfactants containing sodium laureth sulfate and diethanolamide, was studied. The research results analysis of the flotation separation of a mixture of crushed plastic wastes was carried out according to the calculated values of the extraction of a floated component ε and the purity of a concentrate β. It was noted that the maximum extraction of the floated component depends on the polymer and surfactant type. A mixture of surfactants at lower concentrations allows to achieve greater extraction of the floated component with less foaming ability. The research results on the extraction of polystyrene from the air flow rate at various concentrations of surfactants’ mixture show that the extraction has a maximum at a certain air flow rate. At low air flow rates, the working volume of liquid is not saturated enough with gas bubbles. If the optimal value of air flow rates is exceeded, many gas bubbles are formed that are not involved in the flotation process. The research results on the extraction of polystyrene from the aerated liquid layer height at various concentrations of surfactants’ mixture show that, at a low height of the aerated liquid layer, the probability of collision of a plastic particle with an air bubble is low and some potentially floated particles seek the bottom of an apparatus without having time to collide with an air bubble. When assessing the influence of liquid temperature on the flotation process, it was found that increasing the liquid temperature above 20°C leads to a sharp decrease in ABS and PS extraction. This is explained by the fact that the dependence of the surfactants’ foaming ability on the temperature is characterized by solubility curves and for most surfactants they have an extremum.

scholarly journals Evaluation of Izmir Tulum cheese pieces by drying with tray drier at different air flow rates and temperatures

2018 ◽  
Author(s):  
Nurcan Koca ◽  
Gulsah Kizilalp ◽  
Izel Polat ◽  
Müge Urgu
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Sensory Properties ◽  
Water Holding Capacity ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Physical Chemical ◽  
Tulum Cheese ◽  
Water Holding

Izmir tulum cheese pieces were dried using a tray dryer at different air flow rates (1.0 and 1.8 m/s) and temperatures (45oC, 55oC and 65oC). The increase in temperature and air flow rate increased bulk and tapped bulk densityand decreased the water holding capacity. The lowest lightness and highest redness were obtained in samples dried at 65oC. The samples dried at 55°C and 1 m/s had the highest flavor and overall impression scores. As a result, a dried cheese product to benefit from left-over pieces obtained during packaging  was developed, having advantages such as easy to transport, store and package.Keywords: Izmir Tulum cheese; tray dryer; physical, chemical and sensory properties.   

Evaluation of numerical modelling for a compact down-hole subsea gas-liquid separator for high gas content

2009 ◽  
Vol 49 (1) ◽  
pp. 433
Author(s):  
Shakil Ahmed ◽  
Mohamed Nabil Noui-Mehidi ◽  
Jamal Naser's ◽  
Gerardo Sanchez Soto ◽  
Edson Nakagawa
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volume Fraction ◽  
Air Flow ◽  
Gas Content ◽  
Water Mixture ◽  
Air Flow Rate ◽  
Flow Rates ◽  
High Efficient ◽  
Liquid Separator

This paper describes the computational fluid dynamics (CFD) modelling of a laboratory scale gas-liquid separator designed for high gas content. The separator consists of two concentric pipes with swirl tube in the annular space between the pipes. The gas-liquid mixture comes tangentially from the side inlet and the system works with a combination of gravity and centrifugal forces to achieve a high-efficient gas-liquid separation. Three dimensional transient multi-phase fluid flows were solved to predict the velocity and volume fraction of each phase. The standard k- turbulence model was used for turbulence closure. The performance of the gas-liquid separator was visually established for a range of gas flow rates (271–495 L/min), with volume fraction (VF) =0.874–0.985 by observing the liquid carry over (LCO) regime where liquid was carried out in the gas stream. The liquid and gas flow rates at which the LCO was observed defines the upper operational range of the separator. Air-water mixture was used in the numerical simulations to keep consistent with the experiments. The pressure between the inlet and exit was validated against the experiments for different air-water flow rate combinations. The values were matched reasonably well for high air flow rate (495 L/min, VF=0.985) but were under-predicted for low air flow rate (271 L/min, VF=0.874). The air and water were mixed upstream of the inlet in the experiments and the pressure was measured at the start of the inlet. In case of numerical simulation the air and water were mixed at the inlet. This might cause the deviation of pressure when the air flow rate was low.

Two-Phase Flow Visualization for a Hybrid Heat Sink

2018 ◽  
Author(s):  
Danish Rahman ◽  
Ahmad Almomani ◽  
Ibrahim Hassan ◽  
Yasser Al-Hamidi ◽  
Aziz Rahman
Keyword(s):  
Flow Rate ◽  
Slug Flow ◽  
Air Flow ◽  
Plug Flow ◽  
Cross Flow ◽  
Flow Regimes ◽  
Air Flow Rate ◽  
Two Phase ◽  
Flow Rates ◽  
Impingement Jet

This paper aimed to study two-phase flow under adiabatic conditions through the process of flow visualization. This was done through the use of a test section with a cross flow and a jet impingement (swirl jet). The flow regimes under different air-water flow rates were determined using a high-speed camera that recorded digital videos. For each of the flow rates the pressure differential between the inlet and the outlets were measured. Through the pressure drop it is proposed that the types of flow regimes may later be able to be predicted. Nine air-water flow rates were considered to collect data and generate a flow map for the impingement jet and cross flow. The major observed flow regimes within the crossflow and impingement jet followed the predicted trend with bubbly and plug flow in the former, and slug flow in the latter. It was further observed that increasing the air flow rate increased the likelihood of bubbly and plug flow in both the cross-flow and impingement jet. In the cross flow, a lower air flow rate resulted in bubbly flow while within the impingement jet, a lower air flow rate resulted in slug flow.

scholarly journals Dynamic Permeability of Porous Elastic Fabrics

2012 ◽  
Vol 7 (2_suppl) ◽  
pp. 155892501200702 ◽  
Author(s):  
Phillip W. Gibson ◽  
Kenneth Desabrais ◽  
Thomas Godfrey
Keyword(s):  
Flow Rate ◽  
High Pressures ◽  
Air Flow ◽  
High Strength ◽  
Fluid Structure Interactions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Dimensional Changes ◽  
Permeability Changes ◽  
Dynamic Permeability

This paper describes permeability measurements for porous fabrics as influenced by strain, humidity, air flow rate, and fabric elasticity. The focus is on standard parachute fabrics, where the fabric's porosity and air permeability influence the rate of steady-state descent, and also affect the complicated fluid-structure interactions taking place during parachute opening and deployment. High strength nylon parachute fabrics showed relatively small permeability changes due to strain, humidity, and flow rate. Comparative measurements on elastomeric fabrics showed much larger changes in air flow due to fabric dimensional changes at high pressures and flow rates. Elastomeric fabrics that stretch and change permeability in response to higher pressures and flow rates may be able to reduce the “opening shock” during the parachute deployment phase.

Thermal analysis on charging and discharging behaviour of a phase change material-based evacuated tube solar air collector

2016 ◽  
Vol 27 (2) ◽  
pp. 156-172 ◽  
Author(s):  
Neeraj Mehla ◽  
Avadhesh Yadav
Keyword(s):  
Phase Change ◽  
Total Energy ◽  
Phase Change Material ◽  
Flow Rate ◽  
Air Flow ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Solar Air Collector ◽  
Evacuated Tube ◽  
Change Material

The performance analysis on the phase change material-based evacuated tube solar air collector was examined under consecutive and simultaneous charging and discharging modes. Acetamide was used as phase change material. The system performance was evaluated on the basis of the phase change material storage system energy efficiency, exergy efficiency, collector efficiency, the instantaneous energy stored in the phase change material and total energy stored by the system at low and high air flow rates of 0.018 kg/s and 0.035 kg/s, respectively. The maximum average efficiency (17.9%) of the collector was obtained at a high air flow rate during simultaneously charging and discharging of the phase change material. The results obtained demonstrate that the system is more effective when it is operated with high air flow rate during simultaneously charging and discharging of the phase change material. The average total energy at high air flow rates is 1.01 to 1.02 times more in comparison to that at low air flow rates. The findings show the feasibility of the phase change material-based evacuated tube solar air collector for producing hot air for space heating during consecutive and simultaneous charging and discharging of the phase change material in northen Indian climatic conditions. This system would be relevant in areas with good sunlight.

The Flow Field and Main Gas Ingestion in a Rotor-Stator Cavity

2007 ◽  
Author(s):  
R. P. Roy ◽  
D. W. Zhou ◽  
S. Ganesan ◽  
C.-Z. Wang ◽  
R. E. Paolillo ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Radial Clearance ◽  
Air Flow Rate ◽  
Experimental Conditions ◽  
Time Resolved

The ingestion of mainstream gas into turbine rotor-stator disk cavities and simultaneously, the egress of cavity gas into the main gas path are consequences of the prevailing unsteady, three-dimensional flow field. To understand these processes, we are carrying out a study that combines experiments in a model single-stage axial turbine with computational fluid dynamic (CFD) simulations. The turbine stage features vanes, blades, and axially overlapping radial clearance rim seal. In this paper, we present time-resolved velocity maps, obtained by particle image velocimetry, of the flow in the disk cavity at four experimental conditions as defined by the main air flow rate, rotor speed, and purge air flow rate. Time-averaged but spatially local measurement of main air ingestion is also presented. Significant ingestion occurred at two of the four experimental conditions where the purge air flow rate was low — it is found that high tangential (swirl) velocity fluid intersperses with lower tangential velocity fluid in the rim region of the cavity. It is argued that the high tangential velocity fluid is comprised of the ingested main air, while the lower tangential velocity fluid is the indigenous cavity air. This interpretation is corroborated by the results of the unsteady, three-dimensional CFD simulation. When the purge flow rate was high, no ingestion occurred as expected; also, large-scale structures that were unsteady appeared in the cavity flow giving rise to large velocity fluctuations. It is necessary to obtain time-resolved information from experiments and computation in such a flow because even when the vane-blade relative position is matched during a particular experiment, the instantaneous flow field does not necessarily remain the same. As such, some of the flow patterns will be smeared out if the interrogation time scale is large.

Sign in / Sign up

Export Citation Format

Share Document