Author: H. DavoudiPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Characterisation of Mixture Preparation in Lean Premixed Prevaporised Combustor Modules by Planar Laser Fluorescence Imaging and Computational Fluid Dynamics Modelling
Author: H. DavoudiCharacterisation of Mixture Preparation in Lean Premixed Prevaporised Combustor Modules by Planar Laser Fluorescence Imaging and Computational Fluid Dynamics Modelling
Author: H. DavoudiCharacterisation of Mixture Preparation in Lean Premixed Prevaporised Combustor Modules by Planar Laser Fluorescence Imaging and Computational ...
Author: Henrik DavoudiIndex to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards
Author: Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 762
Book Description
Theses on any subject submitted by the academic libraries in the UK and Ireland.
A Study of Mixture Formation in a Lean Burn Research Engine Using Laser Fluorescence Imaging
Author: Martin BerckmüllerInvestigation Into Mixing and Combustion in an Optical, Lean, Premixed, Prevaporised Combustor
Author: Stephen C. HardingLean Premixed/prevaporized Combustion
Author: Formadehyde as a Tracer to examine Mixture - Formation in Spark Ignited Engines
Author: Publisher: Cuvillier Verlag
ISBN: 3736920652
Category : Science
Languages : en
Pages : 154
Book Description
Towards Predicting Dynamics in Turbulent Premixed Combustion Using PIV-PLIF Measurements of Flow-flame Microstructure
Author: Seung Hyuck HongPublisher:
ISBN:
Category :
Languages : en
Pages : 216
Book Description
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.
Impact of Mixer Design on Lean Direct Injection Combustion
Author: Xiao RenPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
To reduce the environmental impact of aviation, lean direct injection (LDI) combustion is being pursued to achieve very low emissions. LDI utilizes multi-point mixers to achieve low NOx emissions and satisfactory combustion stability. Since the performance of LDI directly depends on design parameters of each single LDI mixer, a series of fundamental investigations into lean-dome-relevant pilot combustor devices are conducted herein. A single LDI mixer typically uses swirlers with converging venturi and diverging flare to generate swirling flows, which facilitate mixing in the combustor dome. This dissertation aims to investigate the impact of LDI mixer design parameters, including swirler vane angle, flare, and relative swirling direction between inner and outer swirlers, on single-mixer LDI combustion. The flow fields, flame structures and responses, radical distributions, emissions, and lean blowout (LBO) limits of methane-fueled LDI combustion are investigated with varying mixer design parameters. Experimentally, a test system of single-mixer LDI combustion has been designed and built to investigate mixer designs via advanced optical diagnostics, including particle image velocimetry, broadband flame imaging, chemiluminescence imaging, and OH-planar laser induced florescence. Compared against experimental data, the best practices of meshing and turbulence and combustion modeling have been established for Computational Fluid Dynamics (CFD) simulations of LDI. Reasonable agreement between experimental and CFD result has been achieved for flow characteristics and flame structure/response. Larger swirler vane angle lowers LBO limits but produces higher NOx levels. Removing flare reduces NOx emissions at a cost of worsening operability. Counter-swirling forms a stronger shear layer than the co-swirling case.