Bill Sweetman

Bio: Bill Sweetman is an academic researcher. The author has contributed to research in topics: Detonation & Pulse (physics). The author has an hindex of 2, co-authored 4 publications receiving 29 citations.

Proving the concept

Abstract: SUBTITLE: TILTROTORS SHOW GREAT PROMISE BUT ACCEPTANCE HINGES ON THE RESOLUTION OF SAFETY AND INFRASTRUCTURE ISSUES.

A lot of gas

Abstract: Eastern Australian gas reserves at January 1998 were 450 billion cubic metres (bcm) with 255 bcm already produced, i.e. 705 bcm discovered (AGSO 2000). The Australian Bureau of Agricultural and Resource Economics (ABARE) expects another 255 bcm to be produced to 2009/10 (ABARE 1995). Scope for additional discoveries in these states is minimal and a pipeline from Western Australia or Darwin will be needed around 2005 when Bass Strait and Central Australia will be unable to meet growing consumption.

Supersonic contenders enter the ring

Abstract: SUBTITLE: TWO RIVAL DESIGN TEAMS GO PUBLIC WITH PLANS TO DELIVER A VIABLE AND QUIET SBJ BY 2012.

Inclination calculation apparatus and inclination calculation program, and game apparatus and game program

Abstract: An inclination calculation apparatus sequentially calculates an inclination of an input device operable in terms of a posture thereof. The input device includes acceleration detection means and imaging means. The inclination calculation apparatus sequentially calculates first inclination information representing an inclination of the input device from positions of two imaging targets in a taken image obtained by the imaging means. The inclination calculation apparatus also sequentially calculates second inclination information representing an inclination of the input device from an acceleration detected by the acceleration detection means. The inclination calculation apparatus calculates an inclination of the input device using the first inclination information and the second inclination information.

Innovation in Flight: Research of the NASA Langley Research Center on Revolutionary Advanced Concepts for Aeronautics

Abstract: The goal of this publication is to provide an overview of the topic of revolutionary research in aeronautics at Langley, including many examples of research efforts that offer significant potential benefits, but have not yet been applied. The discussion also includes an overview of how innovation and creativity is stimulated within the Center, and a perspective on the future of innovation. The documentation of this topic, especially the scope and experiences of the example research activities covered, is intended to provide background information for future researchers.

Three-dimensional numerical simulation of the operation of a rotating-detonation chamber with separate supply of fuel and oxidizer

Abstract: A three-dimensional numerical simulation of the operation of an annular rotating-detonation chamber (RDC) with separate supply of combustible mixture components, hydrogen and air, is performed, and the calculation results are compared to available experimental data. The model is based on a system of time-dependent Reynolds-averaged Navier-Stokes equations complemented with a turbulence model and continuity and energy equations for a multicomponent reacting gas mixture. The system is solved using a coupled algorithm based on the finite volume method and particle method. Calculations are for the first time performed with allowance for effects of finite rates of turbulent and molecular mixing of the combustible mixture components with each other and with reaction and detonation products. The calculation results compare favorably with the experimental data obtained at the Lavrentyev Institute of Hydrodynamics of the Siberian Branch of the Russian Academy of Sciences.

Deflagration-to-detonation transition in gases in tubes with cavities

Abstract: The existence of a supersonic second combustion mode — detonation — discovered by Mallard and Le Chatelier and by Berthelot and Vieille in 1881 posed the question of mechanisms for transition from one mode to the other. In the period 1959–1969, experiments by Salamandra, Soloukhin, Oppenheim, and their coworkers provided insights into this complex phenomenon. Since then, among all the phenomena related to combustion processes, deflagration-to-detonation transition is, undoubtedly, the most intriguing one. Deflagration-to-detonation transition (DDT) in gases is connected with gas and vapor explosion safety issues. Knowing mechanisms of detonation onset control is of major importance for creating effective mitigation measures addressing two major goals: to prevent DDT in the case of mixture ignition, or to arrest the detonation wave in the case where it has been initiated. A new impetus to the increase in interest in deflagration-to-detonation transition processes was given by the recent development of pulse detonation devices. The probable application of these principles to creation of a new generation of engines put the problem of effectiveness of pulse detonating devices at the top of current research needs. The effectiveness of the pulse detonation cycle turned out to be the key factor characterizing the Pulse Detonation Engine (PDE), whose operation modes were shown to be closely related to periodical onset and degeneration of a detonation wave. Those unsteady-state regimes should be self-sustained to guarantee a reliable operation of devices using the detonation mode of burning fuels as a constitutive part of their working cycle. Thus deflagration-to-detonation transition processes are of major importance for the issue. Minimizing the predetonation length and ensuring stability of the onset of detonation enable one to increase the effectiveness of a PDE. The DDT turned out to be the key factor characterizing the PDE operating cycle. Thus, the problem of DDT control in gaseous fuel–air mixtures became very acute. This paper contains results of theoretical and experimental investigations of DDT processes in combustible gaseous mixtures. In particular, the paper investigates the effect of cavities incorporated in detonation tubes at the onset of detonation in gases. Extensive numerical modeling and simulations allowed studying the features of deflagration-to-detonation transition in gases in tubes incorporating cavities of a wider cross section. The presence of cavities substantially affects the combustion modes being established in the device and their dependence on the governing parameters of the problem. The influence of geometrical characteristics of the confinement and flow turbulization on the onset of detonation and the influence of temperature and fuel concentration in the unburned mixture are discussed. It was demonstrated both experimentally and theoretically that the presence of cavities of wider cross section in the ignition part of the tube promotes DDT and shortens the predetonation length. At the same time, cavities incorporated along the whole length or in the far-end section inhibit detonation and bring about the onset of low-velocity galloping detonation or galloping combustion modes. The presence of cavities in the ignition section turns an increase in the initial mixture temperature into a DDT-promoting factor instead of a DDT-inhibiting factor.

Heat fluxes to combustor walls during continuous spin detonation of fuel-air mixtures

Abstract: Pioneering measurements of heat fluxes to the walls of flow-type combustors of different geometries were performed in regimes of continuous spin detonation of fuel-air mixtures under unsteady heating These heat fluxes are compared with those observed in the regime of conventional turbulent combustion in the same combustor Air is used as an oxidizer, and acetylene or hydrogen is used as a fuel For identical flow rates of the fuel, the heat fluxes to the combustor walls in regimes of continuous spin detonation and conventional combustion are close to each other; their mean steady values are ≈1 MW/m2 (≈05% of the enthalpy flux of the products over the channel cross section) In both detonation and combustion regimes, the maximum heat fluxes penetrate into the walls in the mixing region (where the heat release occurs) In the case of detonation, regenerative cooling of the combustor walls by the flow of the fresh mixture occurs in the heat-release region (region of propagation of the detonation-wave front) The regeneration becomes less effective in the downstream direction because of the shorter time of contact between the walls and the cold mixture and a longer time of contact between the walls and the hot products More intense heating persists downstream of the front, where the regeneration ceases, but the temperature of the products is high The character of heating of the wall in the region of rotation of the front of spin detonation waves depends on the number of these waves: the zone of the maximum heat release becomes narrower with increasing number of waves