There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

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Heat and Mass Transfer

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

Preface. Preface to the Second Edition. 1 Foundations of Pyrodynamics. 1.1 Heat and Pressure. 1.2 Thermodynamics in a Flow Field. 1.3 Formation of Propulsive Forces. 1.4 Formation of Destructive Forces. 2 Thermochemistry of Combustion. 2.1 Generation of Heat Energy. 2.2 Adiabatic Flame Temperature. 2.3 Chemical Reaction. 2.4 Evaluation of Chemical Energy. 3 Combustion Wave Propagation. 3.1 Combustion Reactions. 3.2 Combustion Wave of a Premixed Gas. 3.3 Structures of Combustion Waves. 3.4 Ignition Reactions. 3.5 Combustion Waves of Energetic Materials. 4 Energetics of Propellants and Explosives. 4.1 Crystalline Materials. 4.2 Polymeric Materials. 4.3 Classification of Propellants and Explosives. 4.4 Formulation of Propellants. 4.5 Nitropolymer Propellants. 4.6 Composite Propellants. 4.7 Composite-Modified Double-Base Propellants. 4.8 Black Powder. 4.9 Formulation of Explosives. 5 Combustion of Crystalline and Polymeric Materials. 5.1 Combustion of Crystalline Materials. 5.2 Combustion of Polymeric Materials. 6 Combustion of Double-Base Propellants. 6.1 Combustion of NC-NG Propellants. 6.2 Combustion of NC-TMETN Propellants. 6.3 Combustion of Nitro-Azide Propellants. 6.4 Catalyzed Double-Base Propellants. 7 Combustion of Composite Propellants. 7.1 AP Composite Propellants. 7.2 Nitramine Composite Propellants. 7.3 AP-Nitramine Composite Propellants. 7.4 TAGN-GAP Composite Propellants. 7.5 AN-Azide Polymer Composite Propellants. 7.6 AP-GAP Composite Propellants. 7.7 ADN , HNF, and HNIW Composite Propellants. 8 Combustion of CMDB Propellants. 8.1 Characteristics of CMDB Propellants. 8.2 AP-CMDB Propellants. 8.3 Nitramine-CMDB Propellants. 8.4 Plateau Burning of Catalyzed HMX-CMDB Propellants. 9 Combustion of Explosives. 9.1 Detonation Characteristics. 9.2 Density and Detonation Velocity. 9.3 Critical Diameter. 9.4 Applications of Detonation Phenomena. 10 Formation of Energetic Pyrolants. 10.1 Differentiation of Propellants, Explosives, and Pyrolants. 10.2 Energetics of Pyrolants. 10.3 Energetics of Elements. 10.4 Selection Criteria of Chemicals. 10.5 Oxidizer Components. 10.6 Fuel Components. 10.7 Metal Azides. 11 Combustion Propagation of Pyrolants. 11.1 Physicochemical Structures of Combustion Waves. 11.2 Combustion of Metal Particles. 11.3 Black Powder. 11.4 Li-SF6 Pyrolants. 11.5 Zr Pyrolants. 11.6 Mg-Tf Pyrolants. 11.7 B-KNO3 Pyrolants. 11.8 Ti-KNO3 and Zr-KNO3 Pyrolants. 11.9 Metal-GAP Pyrolants. 11.10 Ti-C Pyrolants. 11.11 NaN3 Pyrolants. 11.12 GAP-AN Pyrolants. 11.13 Nitramine Pyrolants. 11.14 B-AP Pyrolants. 11.15 Friction Sensitivity of Pyrolants. 12 Emission from Combustion Products. 12.1 Fundamentals of Light Emission. 12.2 Light Emission from Flames. 12.3 Smoke Emission. 12.4 Smokeless Pyrolants. 12.5 Smoke Characteristics of Pyrolants. 12.6 Smoke and Flame Characteristics of Rocket Motors. 12.7 HCl Reduction from AP Propellants. 12.8 Reduction of Infrared Emission from Combustion Products. 13 Transient Combustion of Propellants and Pyrolants. 13.1 Ignition Transient. 13.2 Ignition for Combustion. 13.3 Erosive Burning Phenomena. 13.4 Combustion Instability. 13.5 Combustion under Acceleration. 13.6 Wired Propellant Burning. 14 Rocket Thrust Modulation. 14.1 Combustion Phenomena in a Rocket Motor. 14.2 Dual-Thrust Motor. 14.2.3 Dual-Grain Dual-Thrust Motor. 14.4 Erosive Burning in a Rocket Motor. 14.5 Nozzleless Rocket Motor. 14.6 Gas-Hybrid Rockets. 15 Ducted Rocket Propulsion. 15.1 Fundamentals of Ducted Rocket Propulsion. 15.2 Design Parameters of Ducted Rockets. 15.3 Performance Analysis of Ducted Rockets. 15.4 Principle of the Variable Fuel-Flow Ducted Rocket. 15.5 Energetics of Gas-Generating Pyrolants. 15.6 Combustion Tests for Ducted Rockets. Appendix A: List of Abbreviations of Energetic Materials. Appendix B: Mass and Heat Transfer in a Combustion Wave. B.1 Conservation Equations at a Steady State in a One-Dimensional Flow Field. B.2 Generalized Conservation Equations at a Steady-State in a Flow Field. Appendix C: Shock Wave Propagation in a Two-Dimensional Flow Field. C.1 Oblique Shock Wave. C.2 Expansion Wave. C.3 Diamond Shock Wave. Appendix D: Supersonic Air-Intake. D.1 Compression Characteristics of Diffusers. D.2 Air-Intake System. Appendix E: Measurements of Burning Rate and Combustion Wave Structure. Index.

Propellants and explosives : thermochemical aspects of combustion

Experimental analysis of diffusion flame spread along thin parallel solid fuel surfaces in a natural convective environment

In this work a numerical study has been carried out to gain physical insight into the phenomena of opposed flow flame spread over an array of thin solid fuel sheets in a microgravity environment. The two-dimensional (2D) simulations show that the flame spread rates for the multiple-fuel configuration are higher than those for the flame spreading over a single fuel sheet. This is due to reduced radiation losses from the flame and increased heat feedback to the solid fuel. The flame spread rate exhibits a non-monotonic variation with decrease in the interspace distance between the fuel sheets. Higher radiation heat feedback primarily as gas/flame radiation was found to be responsible for the increase in the flame spread rate with the reduction of the interspace distance. It was noted that as the interspace distance between the fuel sheets was reduced below a certain value, no steady solution could be obtained. However, at very small interspace distances, steady state spread rates were obtained. Here, due to...

Opposed flow flame spread over an array of thin solid fuel sheets in a microgravity environment

A two-dimensional numerical model of opposed flow flame spread over thin solid fuel is formulated and modeled to study effect of gas phase heat sink (a wire-mesh placed parallel to the fuel surface) on the flame spread rate and flame extinction. The work focuses on the performance of the wire-mesh in normal gravity environment of 21 % oxygen concentration. The simulations were carried out for various mesh parameters (wire diameter, ‘\( \overline{d}_{wr} \)’ and number of wires per unit length, ‘N’) and mesh distance perpendicular to fuel surface (Ymesh). Experiments were carried out for wire mesh with \( \overline{d}_{wr} = 0.035\,{\text{cm}} \) and N = 5 and were found to complement numerical predictions. Both simulations and experiments show that wire mesh is effective in reducing flame spread rate when placed at distance less than flame width (which is about 0.50 cm). Mesh wire diameter is determined to not have major influence on heat transfer. However, smaller wire diameter is preferred on account better aerodynamics and for increasing heat transfer surface area (here prescribed by parameter ‘N’). Computations show that meshes with more number of wires per unit length are more effective heat sinks. However, the flame extinction occurs only if mesh is located very close to the fuel surface (of the order of 0.15 cm) and at this distance flame suppression is relatively insensitive to number of wires per unit length.

Effect of gas phase heat sink on suppression of downward flame spread over thin solid fuels

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Simulations on Optimization of Liquid Spray Burners & Operating Parameters

The upper stage propulsion of spacecrafts is an intensive area of emphasis. In the past few decades, standard propellants have been worked upon and utilized. Cryogenic Propellants viz., Liquid Hydrogen, Liquid Oxygen are widely used for upper stages however, an aspect of concern is the high pressure cryogenic storage tanks that must be able to withstand high pressure thus making fuel tanks bulky needing heavy insulation to store Propellant thereby, reducing performance and practicality. The over-dependence on cryogenic propellants has necessitated active research efforts for efficient alternatives. As an attractive alternative, Nitrogen tetroxide and Monomethyl hydrazine (MMH) are used for many space applications owing to high specific impulse, extreme storage stability, and hypergolic nature. The combination is extensively used in orbital maneuvers, reaction controls, and launch vehicle propulsion. The present study details the role of energetic propellants using N2O4 and MMH as the base composition for enhanced upper stage performance. Selected energetic materials are tested with the base composition by using standard NASA-CEA complex chemical equilibrium program. The performance is evaluated in terms of variation in specific impulse and characteristic velocity. The work is motivated by the need of efficient space operations with attractive propulsive alternatives to minimize over-dependence. To validate the practical utility, the role of chamber pressure, supersonic area ratio and optimal Oxidizer to fuel ratio (O/F) is determined.

Advanced upper stage energetic propellants

Current classical hybrid engines suffer from low solid fuel regression rate, low volumetric loading and relatively low combustion efficiency. The combustion occurs in a boundary layer flame zone, distributed along the length of the combustion chamber about the fuel surface. Portions of the propellant may pass through the chamber without reacting thus secondary combustion chamber are often employed. These chambers add length and mass and may serve as a potential source of combustion instability. These drawbacks can be avoided in Vortex Hybrid Rocket Engine (VHRE). This injection methods generates a bi-directional, co-axial vortex flow field in the combustion. The swirling high velocity rate enhances heat transfer to the fuel surface which in turn drives high regression rate. Vortices are a major component of turbulent flow. The dynamics of vortices depends majorly on the nozzle geometry which in turn drives the mixing properties. The stream wise vorticity drastically alters the mass entrainment of a jet, and the efficiency of this vorticity in entraining fluid increases as the jet evolves downstream. An attempt was made to study the effects of various orifice geometries under different operating flow velocities on characteristics of vortices created by smoke, using a laser visualization technique. The nozzle geometries studied include circular and noncircular (square, triangle). The characteristic features of non-circular ones include improved large and small scale mixing in low and high speed flows, and enhanced combustor performance by improving combustion efficiency, reducing combustion instabilities and undesired emissions. For square and triangular sections the effect of different angles were also observed. Further, straws and meshes were fixed inside the setup such that it ensured a uniform distribution of flow and reduced turbulence to avoid possible variation. Visualization of the flows was carried out in the vicinity of the orifice exit in order to identify flow regimes and to study coherence. The work can be utilized significantly in potential space applications of vortex dynamics in space debris removal system, injectors, HVAC (Heating, ventilation, and air conditioning), nozzles etc.

Vinayak Malhotra

Papers

Opposed flow flame spread over an array of thin solid fuel sheets in a microgravity environment

Effect of gas phase heat sink on suppression of downward flame spread over thin solid fuels

Simulations on Optimization of Liquid Spray Burners & Operating Parameters

Advanced upper stage energetic propellants

Experimental Investigation on Laser Visualization of Flow Vortices