Dynamics and Stability Limits of Syngas Combustion in a Backward-Facing Step Combustor

2007 ◽  
Author(s):  
Raymond L. Speth ◽  
H. Murat Altay ◽  
Ahmed F. Ghoniem
Keyword(s):  
High Speed ◽  
Vortex Method ◽  
Operating Mode ◽  
Operating Conditions ◽  
Video Data ◽  
Stable Region ◽  
Small Scale ◽  
Flammability Limit ◽  
Combustion Dynamics ◽  
Operating Modes

The stability bands and combustion dynamics of syngas under different operating conditions and fuel compositions are investigated. Pressure measurements and high-speed video data are used to distinguish three operating modes. A stable region near the lean flammability limit is characterized by the shedding of small-scale vortices in the shear-layer. A quasistable region is present at intermediate equivalence ratios. At high equivalence ratios, we observe an unstable operating mode characterized by the periodic interaction between a large vortex and the flame. As the amount of hydrogen in the fuel is increased, the lean flammability limit is extended and transitions between operating regimes moves to lower equivalence ratios. Numerical simulations performed using a vortex method correspond to the experimental measurements and confirm the observed instability mechanism.

Dynamics and Stability Limits of Syngas Combustion in a Swirl-Stabilized Combustor

2008 ◽  
Author(s):  
Raymond L. Speth ◽  
H. Murat Altay ◽  
Duane E. Hudgins ◽  
Ahmed F. Ghoniem
Keyword(s):  
High Speed ◽  
Equivalence Ratio ◽  
Fluid Dynamic ◽  
Flame Structure ◽  
Low Frequency ◽  
Operating Conditions ◽  
Video Data ◽  
Combustion Dynamics ◽  
Lean Blowout ◽  
Operating Modes

The combustion dynamics, stability bands and flame structure of syngas flames under different operating conditions are investigated in an atmospheric pressure swirl-stabilized combustor. Pressure measurements and high-speed video data are used to distinguish several operating modes. Increasing the equivalence ratio makes the flame more compact, and in general increases the overall sound pressure level. Very close to the lean blowout limit, a long stable flame anchored to the inner recirculation zone is observed. At higher equivalence ratios, a low frequency, low amplitude pulsing mode associated with the fluid dynamic instabilities of axial swirling flows is present. Further increasing the equivalence ratio produces unstable flames oscillating at frequencies coupled with the acoustic eigenmodes. Additionally, a second unstable mode, coupled with a lower eigen-mode of the system, is observed for flames with CO concentration higher than 50%. As the amount of hydrogen in the fuel is increased, the lean flammability limit is extended and transitions between operating regimes move to lower equivalence ratios.

scholarly journals Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Load Capacity ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Fluid Film ◽  
Small Scale ◽  
Vapor Compression ◽  
Density Profiles ◽  
Film Pressure

Abstract High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles is investigated for two one-dimensional bearing geometries (parabolic and Rayleigh step) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting of a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggests the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

scholarly journals Computational study of smoke flow control in garage fires and optimization of the ventilation system

2009 ◽  
Vol 13 (1) ◽  
pp. 69-78
Author(s):  
Milos Banjac ◽  
Barbara Nikolic
Keyword(s):  
Computational Study ◽  
Ventilation System ◽  
Operating Mode ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
Start Time ◽  
Combustion Dynamics ◽  
Operating Modes ◽  
Smoke Flow ◽  
Emergency Operating

With the aim of evaluating capabilities of a ventilation system to control the spread of smoke in the emergency operating mode, thereby providing conditions for safe evacuation of people from a fire-struck area, computational fluid dynamics simulation of a fire in a semi-bedded garage was conducted. Using the experimental results of combustion dynamics of a passenger car on fire, optimal positions of ventilation openings were determined. According to recommendations by DIN EN 12101 standard, the operating modes of a ventilation system were verified and optimal start time of the smoke extraction system was defined.

Development of a hybrid ozonation biofilm-membrane filatration process for the production of drinking water

2005 ◽  
Vol 51 (6-7) ◽  
pp. 241-248 ◽  
Author(s):  
T. Leiknes ◽  
M. Lazarova ◽  
H. Ødegaard
Keyword(s):  
Drinking Water ◽  
Organic Matter ◽  
High Speed ◽  
Membrane Surface ◽  
Drinking Water Treatment ◽  
Rotating Disk ◽  
Operating Conditions ◽  
Operating Modes ◽  
High Concentrations ◽  
Biomass Separation

Drinking water sources in Norway are characterized by high concentrations of natural organic matter (NOM), low alkalinity and low turbidity. The removal of NOM is therefore a general requirement in producing potable water. Drinking water treatment plants are commonly designed with coagulation direct filtration or NF spiral wound membrane processes. This study has investigated the feasibility and potential of a hybrid process combining ozonation and biofiltration with a rotating disk membrane for treating drinking water with high NOM concentrations. Ozonation will oxidize the NOM content removing colour and form biodegradable organic compounds, which can be removed in biological filters. A constructed water was used in this study which is representative of ozonated NOM-containing water. A rotating membrane disk bioreactor downstream the ozonation process was used to carry out both the biodegradation as well as biomass separation in the same reactor. Maintenance of biodegradation of the organic matter while controlling biofouling of the membrane and acceptable water production rates was the focus in the study. Three operating modes were investigated. Removal of the biodegradable organics was consistent throughout the study indicating that sufficient biomass was maintained in the reactor for all operating conditions tested. Biofouling control was not achieved through shear-induced cleaning by periodically rotating the membrane disks at high speed. By adding a small amount of sponges in the membrane chamber the biofouling could be controlled by mechanical cleaning of the membrane surface during disk rotation. The overall results indicate that the system can favorably be used in an ozonation/biofiltration process by carrying out both biodegradation as well as biomass separation in the same reactor.

Study on Operating Condition in Solar-Absorption Refrigerating System in Summer

2007 ◽  
Author(s):  
Yuefen Gao ◽  
Guohua Shi ◽  
Songling Wang
Keyword(s):  
Solar Energy ◽  
Operating Performance ◽  
Operating Mode ◽  
Operating Conditions ◽  
Operation Management ◽  
Solar Absorption ◽  
Operating Modes ◽  
The Stability ◽  
Cooling Loads ◽  
System Operating

A solar-absorption refrigerating system using the solar energy as the driving power is an energy efficiency system, which is also friendly to the environment. However, as the solar radiation varies with the season, the day and night and the climate, the solar energy supplying to the system is unsteady, which affects the security and the stability of the system. Here a typical solar-absorption refrigerating system is put forward to. Then the operating conditions in summer and their operating performance are discussed. Different operating modes are chosen according to the cooling loads and the weather. Automatic control system is used to keep the whole system operating steadily. Finally a survey is carried out. The operating record indicates that it is reasonable to adopt different operating mode in different case. This will provide the reference for the design and operation management of the solar-absorption refrigerating system.

scholarly journals INTEGRATED ASSESSMENT OF ENVIRONMENTAL AND ECONOMIC EFFICIENCY OF GAS BOILER OPERATING MODES

2020 ◽  
Vol 4 (157) ◽  
pp. 127-133
Author(s):  
Y. Ponomarenko ◽  
M. Katkov ◽  
R. Semenenko
Keyword(s):  
Economic Efficiency ◽  
Power Plants ◽  
Thermal Power ◽  
Operating Mode ◽  
Operating Conditions ◽  
Technological Parameters ◽  
Boiler Load ◽  
Operating Modes ◽  
Steam Boilers ◽  
Time Changes

A thermal energy is one of the most significant sources of environmental impact.This is a consequence of both the use of mostly non-renewable natural resources and environmental pollution from thermal power plants. The intensity of this impact depends on many factors, namely the purpose, power, type of fuel used and operating mode. Existing studies have established links between emissions and characteristics such as power and fuel type for stationary operating conditions. At the same time, changes in operating conditions have a significant impact on environmental and economic characteristics. This article is devoted to establishing the relationship between the operational characteristics of gas boilers and their environmental and economic efficiency. The analysis was based on the field data obtained from steam and water boilers that are in commercial operation and uses the natural gas. It was found that for steam and water boilers, there is a well-conditioned non-linear relationship between the technological parameters of boiler operation, in particular gas consumption, the percentage of boiler load, the amount and temperature of flue gases with indicators of pollutants entering the atmosphere. The most significant factor affecting the environmental and economic characteristics of boilers is the percentage of load of boilers. The nature of the dependency is determined by the type of boiler and the setting mode. These dependences with a high degree of conditionality have a parabolic character, which makes it possible to assume the existence of adjustment modes that minimize environmental and economic costs. For steam and water boilers, the dependence of environmental impact on the percentage of load is direct. But for steam boilers in the range of data that were studied, it has a monotonous character, that is, it does not have an extremum point. For water boilers, it is possible to find the optimal loading level that minimizes environmental costs, but to confirm this assumption, additional research is needed at low boiler loading levels. The proposed method can be used to determine the operating modes of boilers and their settings, taking into account environmental and economic criteria. Keywords: water gas boilers, steam gas boilers, operating modes, environmental and economic characteristics.

scholarly journals Analysis of acoustic signals in increments for functional diagnostics of multi-drive units

2019 ◽  
Vol 4 (123) ◽  
pp. 77-85
Author(s):  
Inna Yuriivna Kondratieva ◽  
Hanna Volodymyrivna Rudakova ◽  
Oksana Valeriivna Polyvoda ◽  
Natalia Viktorivna Sarafannikova
Keyword(s):  
High Speed ◽  
Acoustic Noise ◽  
Effective Means ◽  
Current Trend ◽  
Multiple Scale ◽  
Acoustic Signals ◽  
Operating Conditions ◽  
Functional Diagnostics ◽  
Mechatronic Systems ◽  
Operating Modes

The current trend in the development of mechatronic systems is the use of multi-drive frame configurations. Such objects, as a rule, consist of a large number of interacting elements. The relative displacements of these elements generate vibrations that can critically affect the operation of precision mechatronic systems. This can lead to limiting operating conditions of the equipment, and in some cases, its failure. An effective means of preventing accidents, identifying critical modes of operation, diagnosing faults in equipment of electromechanical systems are the methods of functional diagnostics.Methods of functional diagnostics in real time require a large number of calculations, mathematical modeling of the object, processing a large amount of information, which leads to the mandatory use of computer technology. The main methods of processing the measurement results are the Fourier and Laplace transforms, classical methods for analyzing time series, multiple-scale wavelet analysis, etc. The disadvantage of the approaches used is computational complexity in the implementation of discrete transformations and the need for significant amounts of memory to store reference values. The considered methods are based on the analysis of the original signal, however, the increments of the signal of different orders may also be informative.The aim of the research is to develop methods for analyzing acoustic signals generated by working equipment of electromechanical complexes, in increments suitable for use in functional diagnostics systems when monitoring the operating modes of electric drives.In the process of research, an analysis of acoustic noise signals from a working multi-drive unit, obtained as a result of a series of experiments at two high-speed modes, was performed. To speed up the process of analyzing signals and eliminate their redundancy, a data aggregation method has been applied. The degree of permissible aggregation is determined using a multi-scale analysis. The developed method for analyzing aggregated acoustic signals in increments in phase space can be used for functional diagnostics of multi-drive units.

Enlarging Fuel Flexibility for Frame 5 DLN: Combustor Operability and Emissions With High C2+ Content

2015 ◽  
Author(s):  
Alessandro Zucca ◽  
Annalisa Forte ◽  
Nicola Giannini ◽  
Christian Romano ◽  
Roberto Modi
Keyword(s):  
Oil And Gas ◽  
Operating Conditions ◽  
High Concentration ◽  
Current Frame ◽  
Fuel Gas ◽  
Combustion Dynamics ◽  
Operating Modes ◽  
Fuel Flexibility ◽  
Current Design ◽  
Gas Market

Fuel flexibility is a key feature for Dry Low NOx (DLN) combustors, which shall be capable of accepting a wider range of fuel compositions to meet more and more challenging requests from the Oil and Gas market segment (upstream and downstream applications). Non-methane hydrocarbons (C2+) are one of the main targets of GE Oil & Gas efforts to enlarge the fuel flexibility of DLN combustors, as they are often present in high concentration in fuel gas streams that customers would like their gas turbine to be fed with. The main concerns with such fuel gases in DLN combustor are: the risks of flashback, hardware overheating, increased combustion dynamics and NOx emission, ignition in unexpected locations (with potential damage of the combustor, operability issues and impact on durability). In order to assess the capability of the current Frame 5 DLN1 hardware design with high C2+ fuels, a single can full pressure test campaign was conducted on a full size DLN1 combustor at Sesta Combustion Lab (Italy). The combustion chamber was successfully tested in premix mode up to 50%v. of ethane content, observing safe and reliable operation with regard to the above mentioned risks. Special tests were carried out in both Premix and Lean-Lean operating modes, in order to verify the ability of the combustor to maintain a stable and harmless flame and assess the operability margins in the different operating conditions of the combustor. Tests demonstrated a good margin already with the current design. After optimizing the air flow path, the expected performances also in terms of NOx and CO emissions and combustion dynamics were achieved in the investigated ethane content range. These tests outcomes allowed a paramount enlargement of the Frame 5 DLN1 capability in terms of acceptable C2+ concentration in fuel gas.

Development and Characterization of Small-Scale ORC System Using Scroll Expander

2013 ◽  
Vol 291-294 ◽  
pp. 1627-1630 ◽  
Author(s):  
Eunkoo Yun ◽  
Hyun Dong Kim ◽  
Sang Youl Yoon ◽  
Kyung Chun Kim
Keyword(s):  
High Speed ◽  
Organic Rankine Cycle ◽  
Synchronous Generator ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Hot Water ◽  
Working Fluid ◽  
Small Scale ◽  
Operating Characteristics ◽  
Scroll Expander

In order to determine the operating characteristics of a small-scale ORC (organic Rankine cycle) system for various low temperature heat sources, experiments were carried out. A small-scale ORC power generation system adopting R-245fa as a working fluid was designed and manufactured. Hot water was used for the heat source and the temperature was controlled by the 110 kW electric resistance heaters which provided up to 150 °C. Cooling temperature was controlled by a circulating water chiller to simulate various heat sink environments. An open-drive oil-free scroll expander directly connected to a high-speed synchronous generator was installed in the ORC unit. The efficiencies of the cycle and the expander, electric power of the developed ORC system with respect to the operating conditions were investigated by experiments. The factors which influence the performance of the oil-free scroll expander were analyzed and discussed.

Distributed Modeling Of Building Systems Through Cyber-Physical Integration

2019 ◽  
pp. 12-17
Keyword(s):  
Data Structure ◽  
Operating Conditions ◽  
Physical Models ◽  
Distributed Model ◽  
Physical Processes ◽  
Distributed Modeling ◽  
Distributed Models ◽  
Operating Modes ◽  
Building Systems ◽  
Important Practical Application

This article describes the proposed approaches to creating distributed models that can, with given accuracy under given restrictions, replace classical physical models for construction objects. The ability to implement the proposed approaches is a consequence of the cyber-physical integration of building systems. The principles of forming the data structure of designed objects and distributed models, which make it possible to uniquely identify the elements and increase the level of detail of such a model, are presented. The data structure diagram of distributed modeling includes, among other things, the level of formation and transmission of signals about physical processes inside cyber-physical building systems. An enlarged algorithm for creating the structure of the distributed model which describes the process of developing a data structure, formalizing requirements for the parameters of a design object and its operating modes (including normal operating conditions and extreme conditions, including natural disasters) and selecting objects for a complete group that provides distributed modeling is presented. The article formulates the main approaches to the implementation of an important practical application of the cyber-physical integration of building systems - the possibility of forming distributed physical models of designed construction objects and the directions of further research are outlined.

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