Modeling Macro- And Micro-Scale Turbulent Mixing and Chemistry in Engine Exhaust Plumes

Modeling Macro- And Micro-Scale Turbulent Mixing and Chemistry in Engine Exhaust Plumes PDF Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781724301871
Category :
Languages : en
Pages : 216

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Book Description
Simulation of turbulent mixing and chemical processes in the near-field plume and plume-vortex regimes has been successfully carried out recently using a reduced gas phase kinetics mechanism which substantially decreased the computational cost. A detailed mechanism including gas phase HOx, NOx, and SOx chemistry between the aircraft exhaust and the ambient air in near-field aircraft plumes is compiled. A reduced mechanism capturing the major chemical pathways is developed. Predictions by the reduced mechanism are found to be in good agreement with those by the detailed mechanism. With the reduced chemistry, the computer CPU time is saved by a factor of more than 3.5 for the near-field plume modeling. Distributions of major chemical species are obtained and analyzed. The computed sensitivities of major species with respect to reaction step are deduced for identification of the dominant gas phase kinetic reaction pathways in the jet plume. Both the near field plume and the plume-vortex regimes were investigated using advanced mixing models. In the near field, a stand-alone mixing model was used to investigate the impact of turbulent mixing on the micro- and macro-scale mixing processes using a reduced reaction kinetics model. The plume-vortex regime was simulated using a large-eddy simulation model. Vortex plume behind Boeing 737 and 747 aircraft was simulated along with relevant kinetics. Many features of the computed flow field show reasonable agreement with data. The entrainment of the engine plumes into the wing tip vortices and also the partial detrainment of the plume were numerically captured. The impact of fluid mechanics on the chemical processes was also studied. Results show that there are significant differences between spatial and temporal simulations especially in the predicted SO3 concentrations. This has important implications for the prediction of sulfuric acid aerosols in the wake and may partly explain the discrepancy between past numerical studies ...

Modeling Macro- And Micro-Scale Turbulent Mixing and Chemistry in Engine Exhaust Plumes

Modeling Macro- And Micro-Scale Turbulent Mixing and Chemistry in Engine Exhaust Plumes PDF Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781724301871
Category :
Languages : en
Pages : 216

Get Book

Book Description
Simulation of turbulent mixing and chemical processes in the near-field plume and plume-vortex regimes has been successfully carried out recently using a reduced gas phase kinetics mechanism which substantially decreased the computational cost. A detailed mechanism including gas phase HOx, NOx, and SOx chemistry between the aircraft exhaust and the ambient air in near-field aircraft plumes is compiled. A reduced mechanism capturing the major chemical pathways is developed. Predictions by the reduced mechanism are found to be in good agreement with those by the detailed mechanism. With the reduced chemistry, the computer CPU time is saved by a factor of more than 3.5 for the near-field plume modeling. Distributions of major chemical species are obtained and analyzed. The computed sensitivities of major species with respect to reaction step are deduced for identification of the dominant gas phase kinetic reaction pathways in the jet plume. Both the near field plume and the plume-vortex regimes were investigated using advanced mixing models. In the near field, a stand-alone mixing model was used to investigate the impact of turbulent mixing on the micro- and macro-scale mixing processes using a reduced reaction kinetics model. The plume-vortex regime was simulated using a large-eddy simulation model. Vortex plume behind Boeing 737 and 747 aircraft was simulated along with relevant kinetics. Many features of the computed flow field show reasonable agreement with data. The entrainment of the engine plumes into the wing tip vortices and also the partial detrainment of the plume were numerically captured. The impact of fluid mechanics on the chemical processes was also studied. Results show that there are significant differences between spatial and temporal simulations especially in the predicted SO3 concentrations. This has important implications for the prediction of sulfuric acid aerosols in the wake and may partly explain the discrepancy between past numerical studies ...

Atmospheric Effects of Aviation

Atmospheric Effects of Aviation PDF Author: Anne M. Thompson
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 332

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NASA University Program Management Information System: FY 1995

NASA University Program Management Information System: FY 1995 PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 670

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29th AIAA Fluid Dynamics Conference

29th AIAA Fluid Dynamics Conference PDF Author:
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 412

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Modeling the Evolution of Vehicle Exhaust Plume Near Road and in Laboratory Dilution Systems Using the CTAG Model

Modeling the Evolution of Vehicle Exhaust Plume Near Road and in Laboratory Dilution Systems Using the CTAG Model PDF Author: Yan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 209

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Book Description
There are a growing number of people living or spending substantial time near major roadways, being exposed to elevated traffic-related pollutants. Due to their adverse health effect, it is imperative to reduce the uncertainties in the traffic emission inventory and characterize the spatial and temporal impacts of pollutants on near-road air quality, which is critical to assessing human exposure. This dissertation presents the development and applications of an environmental turbulent reacting flow model, the Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model. CTAG is designed to simulate the transport and transformation of multiple air pollutants in various environments. For near-road applications, CTAG couples the major turbulent mixing processes with gas-phase chemistry and aerosol dynamics. CTAG demonstrates that significant improvement in predicting the spatial gradients of pollutants near roadways can be achieved by detailed treatment of turbulence characteristics. It is commonly assumed that the NO2/NOx ratio by volume for most roadways is 5%. However, this dissertation is the first to show that this assumption may not be suitable for most roadways, especially those with a high fraction of heavy-duty truck traffic. It also illustrates that the dynamics of exhaust plumes are highly sensitive to vehicle-induced turbulence, sulfuric acid induced nucleation, and condensation of organic compounds. It simulates, for the first time, the multi-scale aerosol dynamics and microenvironmental air quality by introducing a multi-scale structure to generate the processed on-road particle emissions. It implies that roadway and surrounding infrastructure designs can affect near-road air quality. CTAG can be used to improve the regulatory model in assessing the air quality in near-road environments. The turbulent reacting flows inside the fabricated dilution systems are also investigated since they are essential to most emission testing procedures and share the same mechanisms with the atmospheric dilution. CTAG investigates the effects of the dilution parameters and illustrates that turbulence plays a crucial role in mixing the exhaust with the dilution air, and the strength of nucleation dominates the level of particle emissions. A potential unifying parameter, the dilution rate of exhaust, is found to play an important role in new particle formation. Using the CTAG model, urban planners have the potential to develop strategies to reduce the uncertainties associated with dilution samplings and define a standardized dilution sampling methodology for characterizing emissions from multiple combustion sources.

NASA University Program Management Information System, FY 1994

NASA University Program Management Information System, FY 1994 PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 648

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Proceedings

Proceedings PDF Author:
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages : 332

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1st AIAA Aircraft Engineering, Technology, and Operations Congress

1st AIAA Aircraft Engineering, Technology, and Operations Congress PDF Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 532

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Modeling and Simulation of Turbulent Combustion

Modeling and Simulation of Turbulent Combustion PDF Author: Santanu De
Publisher: Springer
ISBN: 9811074100
Category : Science
Languages : en
Pages : 661

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Book Description
This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.

Turbulent Combustion Modeling

Turbulent Combustion Modeling PDF Author: Tarek Echekki
Publisher: Springer Science & Business Media
ISBN: 9400704127
Category : Technology & Engineering
Languages : en
Pages : 496

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Book Description
Turbulent combustion sits at the interface of two important nonlinear, multiscale phenomena: chemistry and turbulence. Its study is extremely timely in view of the need to develop new combustion technologies in order to address challenges associated with climate change, energy source uncertainty, and air pollution. Despite the fact that modeling of turbulent combustion is a subject that has been researched for a number of years, its complexity implies that key issues are still eluding, and a theoretical description that is accurate enough to make turbulent combustion models rigorous and quantitative for industrial use is still lacking. In this book, prominent experts review most of the available approaches in modeling turbulent combustion, with particular focus on the exploding increase in computational resources that has allowed the simulation of increasingly detailed phenomena. The relevant algorithms are presented, the theoretical methods are explained, and various application examples are given. The book is intended for a relatively broad audience, including seasoned researchers and graduate students in engineering, applied mathematics and computational science, engine designers and computational fluid dynamics (CFD) practitioners, scientists at funding agencies, and anyone wishing to understand the state-of-the-art and the future directions of this scientifically challenging and practically important field.