Download or read book Flow Diagnostic of Swirl Stabilized Combustion Without and with Porous Inert Media for Mitigation of Combustion Noise and Thermo acoustic Instabilities written by Joseph Warren Meadows and published by . This book was released on 2014 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Study of combustion dynamics has gained significant research attention since low-emission systems are increasingly employed in the industry. In particular, combustion noise and thermo-acoustic instabilities are of great importance in highly critical applications such as power generation, jet propulsion engines, and rocket propulsion systems. Recently, porous inert media (PIM), also referred to as foam insert, has shown promise in mitigating combustion noise and thermo-acoustic instabilities in lean premixed (LPM), swirl-stabilized combustion at atmospheric pressure and elevated pressures. In this study, the flow field without and with PIM is investigated to understand the underlying mechanisms responsible for mitigating thermo-acoustic instabilities. Experiments are conducted for LPM combustion and lean direct injection (LDI) combustion. First, time-resolved PIV technique is utilized to measure the non-reacting flow field without and with PIM. Although the flow field inside the annulus of the foam insert was optically inaccessible, measurements immediately downstream provide insight into the instantaneous flow field and turbulence characteristics. The study highlights the role of the foam insert on vorticity, velocity, shear layer spreading angle, recirculation zone dynamics, and turbulent kinetic energy; which ultimately affects the acoustics behavior of the combustor in a favorable manner. The effect of PIM on the dominant turbulent structures in the flow field is quantified using proper orthogonal decomposition (POD) technique. Next, flow field measurements are acquired for LPM swirl-stabilized combustion without and with PIM. The turbulent structures similar to the non-reacting flow field are also present in the reacting flow field, with notable difference in size and shape. The instantaneous and average flow fields provide insight into the effects of PIM on the velocity and turbulence fields. POD analysis is used to quantify the effect of PIM on the dominant turbulent structures, and PIM is shown to distribute the turbulent energy from the large scale structures to smaller scale structures. By harmonically reconstructing the flow field at the frequency of thermo-acoustic instability, the feedback mechanism is found to be the vortical structures in the corner recirculation zones, and PIM is shown to eliminate the feedback mechanism. The efficacy of PIM in mitigating combustion noise and thermo-acoustic instabilities is demonstrated for liquid fuel combustion utilizing the LDI concept. In this system, the flame stabilizes downstream of the dump plane due to a balance of flow velocity and flame speed of the fuel-air mixture created upstream. The ring shaped PIM is placed at the dump plane of the combustor to alter the flow field in an advantageous manner. Sound pressure levels (SPL) and CO and NOx emissions are measured for combustion without and with PIM inserts. Effect of atomizing air to liquid mass ratio on SPL suggests equivalence ratio oscillations are the driving force for thermo-acoustic instabilities. Results show that the PIM insert reduces broad band combustion noise, mitigates peak instabilities occurring at the first longitudinal mode of the natural frequency of the combustor, and facilitates thermal feedback from the flame to the fuel atomization process. Different insert geometries were examined and they all reduced SPLs, but the converging foam geometry provided the best performance. Finally, flow fields of LDI combustion are experimentally measured using time-resolved PIV technique without and with PIM. The instantaneous flow field highlights the role of PIM on the fluctuating velocity field. The driving mechanism for thermo-acoustic instability is identified by analyzing the fluctuating flow field, and PIM is found to decrease the driving force for thermo-acoustic instability. The average flow field is used to show the effect of PIM on the turbulence and POD analysis is used to quantify the effect of PIM on the turbulent structures. The study identifies spatial and temporal non-homogeneities in equivalence ratio as the feedback mechanisms for exciting thermo-acoustic instabilities in LDI swirl-stabilized combustion. In general, PIM decreases the driving force while increasing the dampening force in both LPM and LDI combustion systems.
Download or read book Combustings Flow Diagnostics written by D.F.G. Durão and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of papers prepared for and presented at a NATO sponsored Advanced Study Institute which was held in Montechoro, Portugal during the period 16-27 April, 1990. This Institute was attended by approximately ninety delegates from fifteen countries and followed from a related Institute held in Vimeiro, Portugal in 1987 (see the book entitled "Instrumentation for Combustion and Flow in Engines", edited by D. F. G. Dur~o, J. H. Whitelaw and P. O. Witzel. The purposes of the first Institute related closely to instrumentation for use in gas-turbine combustors and the cylinders of internal-combustion engines. These topics were also addressed in the second Institute, though in a manner which was wider ranging and chosen to demonstrate and explain the development and application of measurement methods to combusting flows in general. The papers contained in this boo~ were selected to provide the reader with a comprehensive and up-to-date view of the variety of experimental techniques available to measure in combusting flows. Included are discussions of their range and applicability, potential accuracy and ease of use. Thus, the first paper provides a brief overview and the second an indication of those aspects of combustion which should influence the choice of flow property to be measured and the technique to be used.
Download or read book Combustion Instabilities in Gas Turbine Engines written by Timothy C. Lieuwen and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 2005 with total page 688 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers gas turbine users and manufacturers a valuable resource to help them sort through issues associated with combustion instabilities. In the last ten years, substantial efforts have been made in the industrial, governmental, and academic communities to understand the unique issues associated with combustion instabilities in low-emission gas turbines. The objective of this book is to compile these results into a series of chapters that address the various facets of the problem. The Case Studies section speaks to specific manufacturer and user experiences with combustion instabilities in the development stage and in fielded turbine engines. The book then goes on to examine The Fundamental Mechanisms, The Combustor Modeling, and Control Approaches.
Download or read book Non intrusive Combustion Diagnostics written by Kenneth K. Kuo and published by Begell House Publishers. This book was released on 1994 with total page 780 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume selects over sixty papers presented at this symposium, and provides an excellent introduction to the state-of-the-art technology in non-intrusive combustion diagnostics for propulsion systems. As such, it is invaluable for researchers wishing to adopt the methods directly, to those interested in assessing the accuracy, advantages, and limitations of specific techniques, and to those seeking a starting point for new ideas toward advances in combustion diagnostics. Topics range from LIF and PLIF techniques to diagnostics of particles, gaseous reaction systems, and solid propellants. Also covered are diagnostics in practical combustion systems.
Download or read book Characteristics and Control of Combustion Instabilities in a Swirl stabilized Spray Combustor written by S. Murugappan and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Study in a Swirl stabilized Combustor with and Without Spray Combustion written by Mohammad-Reza Ghaffarpour and published by . This book was released on 1992 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Combustion Control in Industrial Multi Swirl Stabilized Spray Combustor written by and published by . This book was released on 2005 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this study is to investigate the emission characteristics and combustion dynamics of multiple swirl spray combustors either in premixing or non-premixed combustion (e.g. Lean Direct Injection), and correlate these combustion characteristics (emissions, combustion instability and lean flammability) to the fluids dynamics (flow structures and its evolution). This study covers measurement of velocity flow field, temperature field, and combustion under effects of various parameters, including inlet flow Reynolds number, inlet air temperature, swirl configurations, downstream exhaust nozzle contraction ratios, length of mixing tube. Knowledge obtained through this comprehensive study is applied to passive and active controls for improving gas turbine combustion performance in the aid of novel sensor and actuator technologies.
Download or read book Characterisation of Coherent Instabilities in a Swirl Burner Under Combustion Conditions written by Claudio Leporati and published by . This book was released on 1995 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Study of Combustion Instability in Swirl stabilized Burner furnace Systems written by Victor Manuel Rodriguez Martinez and published by . This book was released on 2003 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book MILD Combustion Modelling Challenges Experimental Configurations and Diagnostic Tools written by Alessandro Parente and published by Frontiers Media SA. This book was released on 2021-11-26 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Emissions Control in Swirl Stabilized Combustors written by and published by . This book was released on 2006 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Stanford University portion of this collaborative project has four major goals: 1) develop real-time tunable-diode-laser (TDL)-based sensors for combustion control, 2) demonstrate the use of these sensors to measure temperature in liquid-fueled swirl- stabilized flames at the University of Cincinnati, 3) fabricate a swirl-stabilized gas and liquid fuel burner with optical access to enable diagnostic development that mimics the atmospheric pressure performance of the University of Cincinnati facility, and 4) demonstrate the use of the TDL sensor for combustion control in this burner. Early in the project, we designed, fabricated, and tested a first generation TDL temperature sensor using water vapor absorption near 1.8 micrometers. After testing the sensor in well-controlled heated-cell and in stable laminar flames at Stanford University, this first generation temperature sensor was used for measurements a practical swirl-stabilized burner at the University of Cincinnati. The plus or minus 20K accuracy at 500Hz illustrated the potential for TDL laser temperature sensing for combustion control. The time-resolved (500Hz) measurements of gas temperature obtained were the first use of TDL temperature sensing in a liquid-fueled combustor. These measurements also demonstrated the ability to monitor temperature fluctuations in a forced flame and illustrated the potential to identify% of combustion instabilities using a fast Fourier transform (FFT) of time-resolved temperature measurements.
Download or read book Towards Predicting Dynamics in Turbulent Premixed Combustion Using PIV PLIF Measurements of Flow flame Microstructure written by Seung Hyuck Hong and published by . This book was released on 2014 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion dynamics are critical to the development of high-efficiency, low-emission and fuel-flexible combustion systems used for propulsion and power generation. Predicting the onset of dynamics remains a challenge because of the complex interactions among several multi-scale phenomena, including turbulence, kinetics and acoustics, and their strong dependence on the operating conditions and fuel properties. In this thesis, a series of experiments were conducted in a laboratory-scale combustor, burning lean premixed propane/hydrogen/air mixtures over a range of equivalence ratio, fuel composition and inlet temperature. Dynamic pressure and flame chemiluminescence measurements are used to determine macro-scale characteristics such as the frequency, limit cycle amplitude and dynamic flame shape. High-speed, high-resolution particle image velocimetry (PIV) is used to quantify the micro-scale structure of the flow, while planar laser-induced fluorescence (PLIF) of OH radical is used to investigate the flame microstructure. Results demonstrate that combustion dynamics in wake-stabilized flames can be characterized using a single non-dimensional parameter that collapses many response measures over a range of operating conditions and fuel composition, including the critical wake length at which dynamics is first observed, the critical phase at which transition among dynamic modes is encountered, and the limit cycle amplitude, emphasizing the role of the physics and chemistry of the flame processes in driving the overall system dynamics and encapsulating the governing mechanisms. The proposed parameter is based on the normalized strained flame consumption speed, which encapsulates the flow-combustion interactions at the flame scale. PIV data reveal significant changes in the recirculation zone structure depending on the equivalence ratio and the fuel composition, demonstrating the impact of chemical kinetics on the flow. These changes are shown to correlate strongly with the stability characteristics, i.e., blow-off and flashback limits as well as the onset of the thermoacoustic instabilities, highlighting a critical role of the recirculation zone in flame stabilization. An expression for the critical phase at which dynamic mode transition occurs is derived based on the linear acoustic energy balance. It is shown that the critical phase is also a function of the same non-dimensional parameter, suggesting that it represents the state within a dynamic mode as well. Results show that the normalized phase correlates with the upper- and lower-boundary of a dynamic mode, thus being a necessary and sufficient condition for dynamics. The results provide a metric for quantifying the instability margins of fuel-flexible combustors operating over a wide range of conditions. Analysis of PIV and OH-LIF data suggests that heat transfer near the flame-holder may play an important role in determining the stability characteristics. The impact of heat transfer on the onset of dynamics is experimentally investigated using different flame-holders. Results demonstrate the effectiveness of using heat-insulating materials as a passive control strategy to prevent or significantly delay the onset of the instabilities.
Download or read book Combustion Diagnostics by Nonintrusive Methods written by American Institute of Aeronautics and Astronautics and published by . This book was released on 1984 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis and Design Tools for Combustion Instabilities written by and published by . This book was released on 2001 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational analysis of flow through a model combustor is completed using several commercial CFD packages. Both global and reduce-order models prove ineffective for this gas-turbine applicaion. These models exhibit signifloant stiffness or require numerical damping of product concentrations. The existenoe of a CH4+M reaction is critical to the performanoe of any methane/air chemistry model. A 12-specie model based on a set of elementary reactions is found to perform well. The flow is made unsteady by imposing a sinusoidally varying inflow profile.
Download or read book Thermoacoustic Instability written by R. I. Sujith and published by Springer Nature. This book was released on 2021-12-14 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book systematically presents the consolidated findings of the phenomenon of self-organization observed during the onset of thermoacoustic instability using approaches from dynamical systems and complex systems theory. Over the last decade, several complex dynamical states beyond limit cycle oscillations such as quasiperiodicity, frequency-locking, period-n, chaos, strange non-chaos, and intermittency have been discovered in thermoacoustic systems operated in laminar and turbulent flow regimes. During the onset of thermoacoustic instability in turbulent systems, an ordered acoustic field and large coherent vortices emerge from the background of turbulent combustion. This emergence of order from disorder in both temporal and spatiotemporal dynamics is explored in the contexts of synchronization, pattern formation, collective interaction, multifractality, and complex networks. For the past six decades, the spontaneous emergence of large amplitude, self-sustained, tonal oscillations in confined combustion systems, characterized as thermoacoustic instability, has remained one of the most challenging areas of research. The presence of such instabilities continues to hinder the development and deployment of high-performance combustion systems used in power generation and propulsion applications. Even with the advent of sophisticated measurement techniques to aid experimental investigations and vast improvements in computational power necessary to capture flow physics in high fidelity simulations, conventional reductionist approaches have not succeeded in explaining the plethora of dynamical behaviors and the associated complexities that arise in practical combustion systems. As a result, models and theories based on such approaches are limited in their application to mitigate or evade thermoacoustic instabilities, which continue to be among the biggest concerns for engine manufacturers today. This book helps to overcome these limitations by providing appropriate methodologies to deal with nonlinear thermoacoustic oscillations, and by developing control strategies that can mitigate and forewarn thermoacoustic instabilities. The book is also beneficial to scientists and engineers studying the occurrence of several other instabilities, such as flow-induced vibrations, compressor surge, aeroacoustics and aeroelastic instabilities in diverse fluid-mechanical environments, to graduate students who intend to apply dynamical systems and complex systems approach to their areas of research, and to physicists who look for experimental applications of their theoretical findings on nonlinear and complex systems.
Download or read book Advanced Combustion and Aerothermal Technologies written by Nick Syred and published by Springer. This book was released on 2007-10-16 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here readers will find a summary of proceedings at a highly important NATO workshop. The ARW Advanced Combustion and Aerothermal Technologies: Environmental Protection and Pollution Reductions, was held in Kiev, May 2006. The workshop was co-directed by Profs. N. Syred and A.Khalatov, winners of the NATO Scientific Prize 2002, and was organized by the Institute of Thermophysics (Ukraine) and Cardiff University, UK. The primary workshop objective was to assess the existing knowledge on advanced combustion and aerothermal technologies providing reduced environmental impact.
Download or read book Flashback Mechanisms in Lean Premixed Gas Turbine Combustion written by Ali Cemal Benim and published by Academic Press. This book was released on 2014-12-01 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Blending fuels with hydrogen offers the potential to reduce NOx and CO2 emissions in gas turbines, but doing so introduces potential new problems such as flashback. Flashback can lead to thermal overload and destruction of hardware in the turbine engine, with potentially expensive consequences. The little research on flashback that is available is fragmented. Flashback Mechanisms in Lean Premixed Gas Turbine Combustion by Ali Cemal Benim will address not only the overall issue of the flashback phenomenon, but also the issue of fragmented and incomplete research. Presents a coherent review of flame flashback (a classic problem in premixed combustion) and its connection with the growing trend of popularity of more-efficient hydrogen-blend fuels Begins with a brief review of industrial gas turbine combustion technology Covers current environmental and economic motivations for replacing natural gas with hydrogen-blend fuels
