A Numerical Investigation of Turbulent Non-Premixed Nozzle-Mixed Industrial Burner

2002 ◽  
Author(s):  
Per Stralin ◽  
Achintya Mukhopadhyay ◽  
Ishwar K. Puri
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Velocity Ratio ◽  
Flame Stabilization ◽  
Flame Height ◽  
Flow Rates ◽  
Fuel Ratio ◽  
Fuel Flow ◽  
Annular Jet ◽  
Wide Range

Nozzle-mix burners are widely used in heat treatment and non-ferrous melting furnaces, and other applications, where temperature uniformity is required. These burners are stable over a wide range of air-fuel ratios from very lean to rich (up to 50% of excess fuel), high turndown ratio and low NOX emissions at all air-fuel ratios. Here, the fuel is generally transported by a central jet and air through an annular jet. The separation between the fuel jet and the air annulus and confining wall are crucial for flame stabilization. The objective of the present work is to investigate the flow and flame characteristics of a nonpremixed nozzle-mix burner through a detailed parametric study. The inferences from this study will provide useful information for designers, regarding choice of parameters. The burner is modeled as an axisymmetric arrangement of fuel duct at the center, surrounded by a coaxial annular duct of air. The ducts discharge into a confined environment, formed by a chimney, placed coaxially with the ducts. The results of the numerical simulation show that for a given air-fuel ratio, as the fuel flow rate increased, the location of the flame base shifted from near the fuel nozzle towards the oxidizer nozzle. Similar shift in flame position was also observed for higher air velocities for a given fuel velocity. High fuel and air flow rates and small separation between fuel and air jets tend to destabilize the flame. For a given air-fuel ratio, flame height increased with increase in fuel flow rates, but the change became insignificant at higher flow rates. For a given fuel velocity, flame height decreased with increase in air flow rate for both buoyancy-controlled and momentum-controlled regimes. The air-to-fuel velocity ratio was found to be the most significant parameter in determining the flame height.

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.

In-Use Heavy-Duty Diesel Emissions Measurement Using an Air-to-Fuel Ratio Derived Exhaust Flow Rate

2007 ◽  
Author(s):  
John Nuszkowski ◽  
Jason D. Bolyard ◽  
Gregory J. Thompson ◽  
Daniel K. Carder
Keyword(s):  
Fuel Consumption ◽  
Flow Rate ◽  
Internal Combustion Engines ◽  
Exhaust System ◽  
Diesel Emissions ◽  
Vehicle Exhaust ◽  
Flow Rates ◽  
Fuel Ratio ◽  
Fuel Flow ◽  
Heavy Duty Diesel

Emissions produced by internal combustion engines during laboratory testing have been shown to not fully represent real world applications. Raw emissions measurements have aided the study of vehicle emissions resulting from in-use applications. In-use emissions measurements may be cumbersome; being that direct measurement of exhaust flow rate will often require that the vehicle exhaust system be modified. This paper investigated the feasibility of substituting exhaust air-to-fuel ratio and ECU fuel flow rates for the inferred measurement of exhaust flow rates. The air-to-fuel ratio for a diesel application was solved from the measured raw emissions of CO2, O2, and NOx. A 2002 Ford F-650, powered by a 2002 Cummins ISB diesel engine, was fitted with an Annubar™ exhaust flow rate measurement system (averaging pitot tube) in order to directly measure continuous exhaust flow rates. Concurrently, exhaust flow rates were estimated from air-to-fuel ratio, while “theoretical” exhaust flow rates were derived from engine speed, intake air density, and assumed volumetric efficiency. These surrogate measurements of exhaust flow rates were then compared with the direct measurements of flow rates obtained by the Annubar™ system. Fuel consumption estimates based on the air-to-fuel ratio derived exhaust flow rate and CO2, theoretical exhaust flow rate and CO2, and measured exhaust flow rates and CO2 were then compared with reported ECU fueling rates over the entire test and during NTE events. An error analysis was performed on the air-to-fuel ratio exhaust flow rate equation to quantify uncertainty resulting from the measurements and assumed parameters. The results showed that the air-to-fuel ratio derived exhaust flow rates compared well with the measured exhaust flow rates and the theoretical exhaust flow rates with an R2 value of 0.982 and 0.986, respectively. During highly transient events and motoring conditions, the air-to-fuel ratio derived exhaust flow rates were inaccurate due to analyzer response and zero fueling conditions, respectively. However, during steadier operation, the air-to-fuel ratio derived exhaust flow rate compared to the measured exhaust flow rate and the theoretical exhaust flow rate within 3.5% and 1.9%, respectively. Overall measurement uncertainty was most affected by the CO2 analyzer at high AFRs. The resulting fuel consumptions from AFR derived exhaust flow rate, theoretical exhaust flow rate, and MEMS exhaust flow rate compared to within 2% of each other. The ECU fuel consumption was 5–7% higher than the MEMS, AFR derived, and theoretical.

Nitrogen Removal from Anaerobically-Treated Leachate

1984 ◽  
Vol 19 (1) ◽  
pp. 87-100
Author(s):  
D. Prasad ◽  
J.G. Henry ◽  
P. Elefsiniotis
Keyword(s):  
Nitrogen Removal ◽  
Air Flow ◽  
Operating Conditions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Anaerobic Filter ◽  
Ph Values ◽  
Wide Range ◽  
Ammonia Desorption ◽  
Effects Of Ph

Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of ammonia from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, KD for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9, 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120, and 190 cm3/sec/L. Results indicated that nitrogen removal from the effluent of anaerobic filters by ammonia desorption was feasible. Removals exceeding 90% were obtained with 8 hours aeration at pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals under a wide range of operating conditions.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

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.

Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

2017 ◽  
Author(s):  
B. R. Nichols ◽  
R. L. Fittro ◽  
C. P. Goyne
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
System Stability ◽  
Supporting Evidence ◽  
Test Rig ◽  
Flow Rates ◽  
Oil Supply ◽  
Bending Mode ◽  
Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

Determinants of flow across isolated gastroduodenal junctions of cats and rabbits

1983 ◽  
Vol 245 (2) ◽  
pp. G257-G264 ◽  
Author(s):  
K. Schulze-Delrieu ◽  
J. P. Wall
Keyword(s):  
Flow Rate ◽  
High Yield ◽  
Pressure Waves ◽  
Base Line ◽  
Tonic Activity ◽  
Flow Rates ◽  
Wide Range ◽  
Line Flow ◽  
Pressure Resistance ◽  
Unidirectional Valve

The resistance generated by the gastroduodenal junction was measured in isolated cat and rabbit preparations. Cannulas were tied into the antrum and duodenum. Yield pressures were determined by increasing the pressure in one of the cannulas until flow occurred. The junctional segment of the cat maintained a high yield pressure. Yield pressures were similar in the antroduodenal and the duodenogastric direction (12.5 +/- 5.7 vs. 14.8 5.8 cmH2O) and increased on both sides to the same degree following exposure of the preparation to 100 mM [K+] and to 10(-6) M carbachol. These experimental manipulations also led to the occurrence of pressure waves in the antral cannula. Yield pressures were diminished but not abolished by exposure of the preparation to 0 [Ca2+] solution or 10(-6) M isoproterenol. Junctional segments from the rabbit did not maintain a yield pressure. Resistance across the junctional segment of both species was also measured by channeling the outflow of one of the cannulas to a flowmeter. Over a wide range of pressures, flow rates across the junctional segment of the rabbit exceeded those across the junctional segment of the cat. Carbachol and 100 mM [K+] decreased the base-line flow and increased the amplitude of intermittent decreases of flow. Isoproterenol and 0 [Ca2+] had opposite effects. Inflation of a balloon decreased the flow rate across the rabbit but not the cat junctional segment. Flow rates across the junctional segment did not differ in the antroduodenal and duodenogastric direction. The gastroduodenal junction does not act as an unidirectional valve. Pyloric resistance relates to the structure of the pyloric segment and to phasic and tonic activity of its musculature.

Influence of milk flow rate and streak canal length on new intramammary infection in dairy cows

1991 ◽  
Vol 58 (4) ◽  
pp. 383-388 ◽  
Author(s):  
Robert J. Grindal ◽  
Andrew W. Walton ◽  
J. Eric Hillerton
Keyword(s):  
Flow Rate ◽  
Peak Flow ◽  
Peak Flow Rate ◽  
Secondary Importance ◽  
Flow Rates ◽  
Intramammary Infection ◽  
Susceptibility To Infection ◽  
Milk Flow ◽  
Wide Range ◽  
Mastitis Control

SummaryEighteen cows with a wide range of quarter peak flow rates (0·35–2·22 kg/min) were inoculated with Streptococcus agalactiae and Str. dysgalactiae 4 mm into each streak canal every 3 d for 12 d. Thirty of the 72 quarters developed intramammary infection. Mean peak flow rate and length of streak canal of those quarters that became infected were 1·26 ± 0·08 kg/min (mean ± SEM) and 11·47 ± 0·41 mm respectively, compared with 1·01 ± 0·05 kg/min and 12·05 ± 0·35 mm for those that remained uninfected. Logistic regression analysis showed that the probability of infection increased significantly with the increase in peak flow rate (P = O·O1). The influence of streak canal length on new infection, after allowing for the effect of peak flow rate, was not significant at the 5% level (P = 0·07), suggesting that there may be an inverse relationship between teat duct length and infection, but that it is of secondary importance to peak flow rate. If increased mass of milk distends the teat duct by raising intramammary pressure, then quarter susceptibility to infection is further compromised. These results strongly suggest that the benefits of reduced infection from mastitis control, achieved despite dramatic increases in milk flow rate and milk yield, are significantly underestimated.

The Role of Mean Flame Anchoring on the Stability Characteristics of Syngas, Synthesis Natural Gas, and Hydrogen Fuels in a Turbulent Non-Premixed Bluff-Body Combustor

2019 ◽  
Author(s):  
Nikhil Ashokbhai Baraiya ◽  
Satynarayanan R. Chakravarthy
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Momentum Flux ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Inlet Flow ◽  
Combustion Dynamics ◽  
Flow Rates ◽  
Inlet Flow Rate ◽  
The Difference

Abstract A lab-scale bluff body combustor is mapped for its stability and flame dynamics of non-premixed flames. The characteristics are observed across variations in the fuel composition, as well as in the inlet flow rate. The combustor is seen to exhibit markedly different dynamics for each of the varied fuel compositions. This behavior is explained on the basis of mean flame stabilization behavior and on the combined effects of the fuel-jet momentum flux and global equivalence ratio. It is seen that the H2 flames primarily act as a pilot source for secondary combustion of either CO or CH4. Further, it is seen that, the high momentum flux associated with H2-CO mixtures result in combustion near the wall and outside the bluff-body shear layers at low inlet flow rates. Whereas, at high inlet flow rates, the mean heat release rate is seen to stabilize closer to the injection holes as well as extend to near the bluff-body shear layer. This marked difference in flame stabilization is seen to have a drastic effect on the nature of oscillations inside the chamber. This is contrasted to H2-CH4 (synthesis natural gas) flames that exhibit stabilization inside the bluff-body wake at high inlet flow rate. The difference between H2-CH4 and H2-CO flames with regards to combustion dynamics is then explained as a result of the flame stabilization behavior, which is seen to be different across the varied fuel compositions. While H2-CH4 flame exhibits the well-known large wake structures responsible for combustion instability, H2-CO flame exhibits no such structures, owing to their stabilization point. Further analysis using pressure fixed phase instants reveal the difference in nature of combustion dynamics across the tested fuel compositions and are justified using the spatial Rayleigh index map.

Sign in / Sign up

Export Citation Format

Share Document