Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

Introduction to heat transfer

The growth of a vapor bubble in a superheated liquid is controlled by three factors: the inertia of the liquid, the surface tension, and the vapor pressure. As the bubble grows, evaporation takes place at the bubble boundary, and the temperature and vapor pressure in the bubble are thereby decreased. The heat inflow requirement of evaporation, however, depends on the rate of bubble growth, so that the dynamic problem is linked with a heat diffusion problem. Since the heat diffusion problem has been solved, a quantitative formulation of the dynamic problem can be given. A solution for the radius of the vapor bubble as a function of time is obtained which is valid for sufficiently large radius. This asymptotic solution covers the range of physical interest since the radius at which it becomes valid is near the lower limit of experimental observation. It shows the strong effect of heat diffusion on the rate of bubble growth. Comparison of the predicted radius‐time behavior is made with experimental observations in superheated water, and very good agreement is found.

The growth of vapor bubbles in superheated liquids. report no. 26-6

The focus of this article is on intrinsic combustion instabilities in both premixed and nonpremixed systems, identifying, in particular, the roles of differential and preferential diffusion, thermal expansion, and heat losses. For premixed flames, the hydrodynamic instability resulting from thermal expansion plays a central role and is particularly dominant in large-scale flames. It is responsible for the formation of sharp folds and creases in the flame front and for the wrinkling observed over the surface of expanding flames. In contrast, instabilities in diffusion flames, which give rise to cellular and oscillating flames, are mainly driven by diffusive-thermal effects, with thermal expansion playing a secondary role. The discussion also includes instabilities of edge-flames in unmixed reactants, which possess stability characteristics of both premixed and diffusion flames, but with a distinct mode of instability.

Intrinsic Flame Instabilities in Premixed and Nonpremixed Combustion

A review of cavity-based trapped vortex, ultra-compact, high-g, inter-turbine combustors

Basic thermodynamics of FLOXCOM, the low-NOx gas turbines adiabatic combustor

An adiabatic combustor for a gas turbine including: (a) a combustion chamber designed and configured to produce high-pressure combustion gases for the turbine, the combustion chamber having a primary combustion zone containing a substantially vitiated-air zone; (b) at least one primary air inlet providing air to the primary combustion zone, and (c) a fuel injector for injecting fuel, disposed such that the fuel is directly introduced to the vitiated-air zone, wherein the primary air inlet is positioned and directed, and the combustion chamber is designed and configured, so as to produce an internal recirculation that generates a toroidal vortex within the primary combustion zone, thereby producing therein the vitiated-air zone and maintaining therein a state of flameless oxidation.

Design of adiabatic combustors

The main objective of this paper is development of a simple real-time transient performance model for jet engine control. A jet engine arrives to its most dangerous condition during transient operation that may be triggered by fast changes of the input fuel command signal. Thus, the control system specifications are formulated to specify the maximal variance of the fuel flow command (from idle to maximum power level) during transient maneuver. Linear and piecewise-linear techniques are not always convenient and appropriate for turbine engine controller design. An alternative quasilinear simple/ fast engine model is discussed in this paper. This model has maximum accuracy for maximal variance of the fuel flow input command in accordance to the jet engine control system specifications. The fast model is obtained using the Novel Generalized Describing Function, proposed for investigation of nonlinear control systems. The paper presents the Novel Generalized Describing Function definition and then discusses the application of this technique for the development a fast turbine engine simulation suitable for control and real-time applications. Simulation results are compared between the conventional and fast models and found to provide good agreement.

Jet Engine Model for Control and Real-Time Simulations

Novel design of adiabatic combustors

One of the factors which reduces combustion efficiency in a fluidized-bed combustor is the elutriation of fine coal particles from the freeboard above the bed surface. To our knowledge, data about the real local flow behavior of the two-phase flow in the freeboard are lacking in the literature. This paper concerns the measurement of the gas and the elutriated particle velocities in the freeboard of a cold fluidized bed using Laser Doppler Anemometry. A special electronic system has been devised to record simultaneously the gas and particle velocities and to indicate the size of the particles. In this paper the apparatus and some preliminary measurements are reported. The most significant observation is that the gas velocity profiles exhibit minima near the bed center and maxima near the walls.

Yeshayahou Levy

Papers

Basic thermodynamics of FLOXCOM, the low-NOx gas turbines adiabatic combustor

Design of adiabatic combustors

Jet Engine Model for Control and Real-Time Simulations

Novel design of adiabatic combustors

Laser doppler measurements of flow in freeboard of a fluidized bed