Gerard M. Faeth

Bio: Gerard M. Faeth is an academic researcher from University of Michigan. The author has contributed to research in topics: Turbulence & Diffusion flame. The author has an hindex of 71, co-authored 307 publications receiving 16317 citations. Previous affiliations of Gerard M. Faeth include United States Department of the Navy & Pennsylvania State University.

Evaporation and combustion of sprays

Abstract: A description is provided of recent spray evaporation and combustion models, taking into account turbulent two- and three-dimensional spray processes found in furnaces, gas turbine combustors, and internal combustion engines. Within the class of spray models of interest, two major categories are distinguished, including locally homogeneous flow (LHF) models and separated flow (SF) models. SF models are of the greatest practical importance, but LHF models have distinct advantages in some cases. Attention is also given to recent progress on modeling interactions between drops and the flow in both dilute and dense sprays, involving sprays having low and high liquid volume fractions, respectively.

Near-limit drop deformation and secondary breakup

Abstract: The properties of drop deformation and secondary breakup were observed for shock wave initiated disturbances in air at normal temperature and pressure Test liquids included water, glycerol solutions, n-heptane, ethyl alcohol and mercury to yield Weber numbers (We) of 05–1000, Ohnesorge numbers (Oh) of 00006-4, liquid/gas density ratios of 580–12,000 and Reynolds numbers (Re) of 300–16,000 Measurements included pulsed shadowgraphy and holography to find drop deformation properties prior to breakup, as well as drop size distributions after breakup Drop deformation and breakup regimes were identified in terms of We and Oh: regimes at low Oh include no deformation, nonoscillatory deformation, oscillatory deformation, bag breakup, multimode breakup and shear breakup as We is increased However, most of these regimes occur at higher We when Oh values are increased, with no breakup observed for Oh > 4 over the present test range Unified temporal scaling of deformation and breakup processes was observed in terms of a characteristic breakup time that largely was a function of Oh Prior to breakup, the drag coefficient evolved from the properties of spheres to those of thin disks as drop deformation progressed The drop size distribution after breakup satisfied Simmons' universal root normal distribution function for the bag and multimode breakup regimes and could be characterized by the Sauter mean diameter (SMD) alone Drop sizes after shear breakup, however, did not satisfy this distribution function due to the distorting effect of the core or drop-generating drop Nevertheless, the SMD after secondary breakup could be correlated in terms of a characteristic liquid boundary layer thickness for all breakup regimes, similar to recent results for nonturbulent primary breakup Drop properties after secondary breakup suggest that both reduced drop sizes and reduced relative velocities play a role in ending the secondary breakup process

Current status of droplet and liquid combustion

Abstract: The present understanding of spray combustion in rocket engine, gas turbine, Diesel engine and industrial furnace applications is reviewed. In some cases, spray combustion can be modeled by ignoring the details of spray evaporation and treating the system as a gaseous diffusion flame; however, in many circumstances, this simplification is not adequate and turbulent two-phase flow must be considered. The behavior of individual droplets is a necessary component of two-phase models and recent work on transient droplet evaporation, ignition and combustion is considered, along with a discussion of important simplifying assumptions involved with modeling these processes. Methods of modeling spray evaporation and combustion processes are also discussed including: one-dimensional models for rocket engine and prevaporized combustion systems, lumped zone models (utilizing well-stirred reactor and plug flow regions) for gas turbine and furnace systems, locally homogeneous turbulent models, and two-phase models. The review highlights the need for improved injector characterization methods, more information of droplet transport characteristics in turbulent flow and continued development of more complete two-phase turbulent models.

Structure and breakup properties of sprays

Abstract: Multiphase flow phenomena relevant to spray combustion are reviewed, emphasizing the structure of the near-injector dense-spray region and the properties of secondary and primary breakup. Existing measurements of dense-spray structure are limited to round pressure-atomized sprays in still gases and show that the dispersed flow region is surprisingly dilute, that separated flow effects are significant because the flow is dilute and developing, and that atomization involves primary breakup at the liquid surface followed by secondary breakup, while effects of collisions are small. Available information about secondary breakup emphasizes breakup due to shock wave disturbances at large liquid/gas density ratios and shows that secondary breakup is a dominant feature of dense sprays that must be resolved as a function of time so that secondary breakup can be properly treated as a rate process. Finally, available information about primary breakup has been dominated by effects of disturbances in the injector passage; therefore, while some understanding of turbulent primary breakup has been achieved, more information about aerodynamic primary breakup is needed to address practical spray combustion processes.

Fractal and projected structure properties of soot aggregates

Abstract: The structure of soot aggregates was investigated, emphasizing the fractal properties as well as the relationships between the properties of actual and projected soot images. This information was developed by considering numerically simulated soot aggregates based on cluster-cluster aggregation as well as measured soot aggregates based on thermophoretic sampling and analysis by transmission electron microscopy (TEM) of soot for a variety of fuels (acetylene, propylene, ethylene, and propane) and both laminar and turbulent diffusion flame conditions. It was found that soot aggregate fractal properties are relatively independent of fuel type and flame condition, yielding a fractal dimension of 1.82 and a fractal prefactor of 8.5, with experimental uncertainties (95% confidence) of 0.08 and 0.5, respectively. Relationships between the actual and projected structure properties of soot, e.g., between the number of primary particles and the projected area and between the radius of gyration of an aggregate and its projected image, also are relatively independent of fuel type and flame condition.

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Light Absorption by Carbonaceous Particles: An Investigative Review

Abstract: The optical properties of the light-absorbing, carbonaceous substance often called “soot,” “black carbon,” or “carbon black" have been the subject of some debate. These properties are necessary to model how aerosols affect climate, and our review is targeted specifically for that application. We recommend the term light-absorbing carbon to avoid conflict with operationally based definitions. Absorptive properties depend on molecular form, particularly the size of sp 2-bonded clusters. Freshly-generated particles should be represented as aggregates, and their absorption is like that of particles small relative to the wavelength. Previous compendia have yielded a wide range of values for both refractive indices and absorption cross section. The absorptive properties of light-absorbing carbon are not as variable as is commonly believed. Our tabulation suggests a mass-normalized absorption cross section of 7.5 ± 1.2 m2/g at 550 nm for uncoated particles. We recommend a narrow range of refractive indices for s...

A technology-based global inventory of black and organic carbon emissions from combustion

Abstract: [1] We present a global tabulation of black carbon (BC) and primary organic carbon (OC) particles emitted from combustion. We include emissions from fossil fuels, biofuels, open biomass burning, and burning of urban waste. Previous ‘‘bottom-up’’ inventories of black and organic carbon have assigned emission factors on the basis of fuel type and economic sector alone. Because emission rates are highly dependent on combustion practice, we consider combinations of fuel, combustion type, and emission controls and their prevalence on a regional basis. Central estimates of global annual emissions are 8.0 Tg for black carbon and 33.9 Tg for organic carbon. These estimates are lower than previously published estimates by 25–35%. The present inventory is based on 1996 fuel-use data, updating previous estimates that have relied on consumption data from 1984. An offset between decreased emission factors and increased energy use since the base year of the previous inventory prevents the difference between this work and previous inventories from being greater. The contributions of fossil fuel, biofuel, and open burning are estimated as 38%, 20%, and 42%, respectively, for BC, and 7%, 19%, and 74%, respectively, for OC. We present a bottom-up estimate of uncertainties in source strength by combining uncertainties in particulate matter emission factors, emission characterization, and fuel use. The total uncertainties are about a factor of 2, with uncertainty ranges of 4.3–22 Tg/yr for BC and 17–77 Tg/yr for OC. Low-technology combustion contributes greatly to both the emissions and the uncertainties. Advances in emission characterization for small residential, industrial, and mobile sources and topdown analysis combining field measurements and transport modeling with iterative inventory development will be required to reduce the uncertainties further. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; KEYWORDS: emission, black carbon, organic carbon, fossil fuel, biofuel, biomass burning

A front-tracking method for the computations of multiphase flow

Abstract: Direct numerical simulations of multiphase flows, using a front-tracking method, are presented. The method is based on writing one set of governing equations for the whole computational domain and treating the different phases as one fluid with variable material properties. Interfacial terms are accounted for by adding the appropriate sources as δ functions at the boundary separating the phases. The unsteady Navier–Stokes equations are solved by a conventional finite volume method on a fixed, structured grid and the interface, or front, is tracked explicitly by connected marker points. Interfacial source terms such as surface tension are computed on the front and transferred to the fixed grid. Advection of fluid properties such as density is done by following the motion of the front. The method has been implemented for fully three-dimensional flows, as well as for two-dimensional and axisymmetric ones. First, the method is described for the flow of two or more isothermal phases. The representation of the moving interface and its dynamic restructuring, as well as the transfer of information between the moving front and the fixed grid, are discussed. Applications and extensions of the method to homogeneous bubbly flows, atomization, flows with variable surface tension, solidification, and boiling are then presented.

Handbook of heat transfer

Abstract: Handbook of Numerical Heat Transfer Free Full Download Links from Multiple Mirrors added by DL4W on 2015-04-10 02:13:35. Handbook of heat transfer / editors, W.M. Rohsenow, J.P. Hartnett. Y.I. Cho. m 3rd ed. p. cm. Includes bibliographical references and index. ISBN 0-07053555-8. Students investigate heat transfer by conduction, convection and radiation. The analogy between heat and mass transfer is covered and applied in the analysis.