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Caltech Authors (157.532 recursos)

Repository of works by Caltech published authors.

Group = Guggenheim Jet Propulsion Center

Mostrando recursos 1 - 20 de 22

  1. Recent studies on flame stabilization of premixed turbulent gases

    Penner, S. S.; Williams, F.
    FLAME stabilization is of importance in the practical design of ramjets and afterburners. It has been studied extensively in recent years, particularly with reference to bluff-body flame-holders. In the present survey we describe the investigations relating to flame holding by bluff bodies as well as new techniques (e.g.,. flame holding by the use of reverse jets) which may prove to be of practical importance in new engine configurations. In Section II we consider the flow field downstream of a bluff-body flame-holder which includes the recirculation zone behind the body and a region of flame spreading farther downstream. Explicit reference is made to crucial experiments which...

  2. Experiments concerning the mechanism of flame blowoff from bluff bodies

    Zukoski, Edward E.; Marble, Frank E.
    The general problem of flame stabilization on bluff objects centers about the determination of the maximum stream velocity at which stable combustion may be achieved for various flame holder geometries, gas mixtures and conditions of the approaching combustible stream. Since the process involves both gas dynamic problems and chemical kinetic problems of great complexity, the most reasonable approach is one of similarity, that is, to determine under what conditions the behavior of one flame holder is similar to the behavior of another one. Because a very large number of physical and chemical variables is involved in a combustion problem, similarity...

  3. Heat transfer in turbulent shear flow

    Rannie, W. D.
    The problems of heat transfer in turbulent shear flow along a smooth wall are discussed from the point of view of von Karman's well-known 1939 paper on the analogy between fluid friction and heat transfer. Methods for extending the analysis to higher Prandtl Numbers are suggested.

  4. Flame theory and combustion technology

    Marble, Frank E.
    The study of combustion processes is in a sufficiently early stage so that there is no strong connection between combustion theory and the technology of combustion chamber development. To clarify such a connection is the principal task of workers engaged in establishing combustion as an engineering science. The equations of aerothermochemistry are reviewed for the case in which temperature and composition gradients are small. Solutions have been obtained in very few cases and under very restrictive circumstances; most detailed considerations are restricted to the plane laminar flame front. The current situation in the theory of plane laminar flames is discussed. The few extensions...

  5. Compressibility effects on secondary flows

    Loos, H. G.
    The method of W. R. Hawthorne for the calculation of the secondary vorticity is generalized for compressible flow. It is shown that in the linearized theory (small vorticity) the influence of compressibility upon the secondary vorticity is due to (1) the entropy gradient in the approaching flow and (2) the compression of the fluid during the turning of the flow. The analysis is applied to the secondary vorticity which generates in a cascade or bend if the approaching flow has a boundary layer with a Prandtl Number equal to unity and has been developed along an insulated wall.

  6. Interference during burning in air for nine stationary fuel droplets arranged in a body-centered cubic lattice

    Kanevsky, J.

  7. Thermonuclear power plants

    Tsien, Hsue-Shen
    Some of the unique features of thermonuclear power plants and the essential problems in the technical design of such plants are discussed in this paper. The thermonuclear reaction rate for the fusion of deuterium is calculated on the basis of a similar analysis published by Gamow and Teller. The pressure, temperature, and minimum dimensions of the necessary reaction chamber are determined largely by consideration of reaction quenching and energy loss near the walls. Results are presented for the power output and the efficiency of a power station utilizing the deuterium fusion reaction. The comment by Greenstein that follows this paper deals particularly with the difficult problem of...

  8. Optimalizing control in the presence of noise interference

    Serdengecti, Sedat
    The performance of a modified peak-holding optimalizing control system depends in part on the ability of the controller to detect the input signal frequency component in the output of the controlled system. This paper describes several techniques that may be used for detecting this component and analyzes one of them in great detail. The subject of the detailed analysis is the method of filtering through cross-correlation. A statistical analysis is also carried out in order to demonstrate the efficiency of this method.

  9. Interference effects during burning in air for stationary n-heptane, ethyl alcohol, and methyl alcohol droplets

    Rex, J. F.; Fuhs, A. E.; Penner, S. S.
    Experiments have been conducted for the determination of the evaporation constant and flame shapes of two and of five closely spaced droplets burning in air. Droplets of approximately the same and of different diameters were used at various distances between the droplet centers. The apparent flame shape, which was observed only for n-heptane droplets, changes very little during burning. The square of the droplet diameter decreases linearly with time for fixed spacing between droplet centers, at least within the experimental limits of accuracy. In general, the average evaporation constant for two droplets, K', must be assumed either to vary continuously during burning or else to be a function of average initial...

  10. Experiments on the burning of single drops of fuel

    Goldsmith, M.
    Experiments have been performed in order to measure the mass rate of consumption of single drops of liquid fuel suspended on a quartz filament and burning under various ambient conditions. The influence of increased oxidizer concentration, increased pressure, and elevated temperature in the surrounding atmosphere on mass burning rate has been studied. Comparison is made with theoretical calculations based on the concept of a heterogeneous diffusion flame, with burning rate controlled by heat and mass transfer. The influence of forced convection on burning rate and extinction of burning has also been investigated.

  11. Apparent emission intensities from a turbulent flame composed of wrinkled laminar flames

    Williams, F.; Fuhs, A. E.
    There has recently been some discussion on the use of the model of a wrinkled laminar flame for an approximate description of turbulent flame structure. In particular, Summerfield has claimed that some of his observations contradict theoretical predictions based on the use of this model. 4 It is the purpose of the following discussion to clarify 150me of the consequences of the wrinkled laminar flame model.

  12. On excess enthalpy, flame extinction and minimum ignition energies

    Penner, S. S.; Williams, F.

  13. On the development of rational scaling procedures for liquid-fuel rocket engines

    Penner, S. S.
    A critical summary is presented of recent theoretical studies concerning similarity analysis and the scaling of liquid-fuel rocket engines. On the basis of this work, some suggestions are offered for an experimental program which has as its objective the development of rational scaling procedures.

  14. Emissivity of hydrogen atoms at high temperatures

    Aroeste, Henry; Benton, William C.
    A method is described for making estimates of the total emissivity of hydrogen in the temperature and pressure ranges where hydrogen atoms predominate under equilibrium conditions. For a typical geometrical depth of 50 cm, and temperatures of the order of 12 500ºK and higher, with pressures of the order of 100 atmos and higher, the emissivity approaches unity (є≳0.95), while for temperatures of the order of 9500ºK and lower, with pressures of the order of 10 atmos and lower, the emissivity approaches zero (є≾0.05). The variations of the emissivity between these approximate limits are shown graphically as functions of temperature...

  15. On the determination of absolute intensities from single- and multiple-path absorption measurements

    Penner, S. S.; Aroeste, H.
    The physical principles involved in conventional absolute intensity measurements are reviewed. Experimental difficulties rule out the use of extrapolation techniques for some spectral transitions. For this reason it is of interest to re-examine the possibility of using total absorption measurements, in conjunction with the curves of growth, for making intensity estimates. Extrapolation methods yield results which are independent of spectral line shape. Use of the curves of growth, on the other hand, implies the assumption that the line contour can be described by combined Doppler and Lorentz broadening. The curves of growth permit a unique correlation between total absorption and f-value either...

  16. On generalized scaling procedures for liquid-fuel rocket engines

    Penner, S. S.; Fuhs, A. E.
    The scaling procedures of Penner and Tsien, of Crocco and of Barrère have been generalized by using the assumption that the mean drop size is proportional to the product of powers of the Weber number and the Reynolds number, together with the hypothesis that the total conversion time varies as a power (usually the second) of the drop diameter. The results obtained for the steady aero thermochemistry and for unstable motor operation (low-frequency and high-frequency oscillations) are shown to reduce to previously published rules when suitable simplifying assumptions are made.

  17. Multiple-path technique for the determination of physico-chemical data behind shock fronts

    Hooker, W.; Lapp, M.; Weber, D.; Penner, S. S.

  18. Simultaneous light-absorption and emission measurements behind a shock wave

    Harshbarger, F.

  19. Infrared emissivities and absorptivities of gases

    Penner, S. S.; Thomson, A.
    Approximate analytic expressions are obtained for the "effective band widths" and emissivities of diatomic molecules at elevated pressures. The absorptivities of molecular vibration‐rotation bands are evaluated for radiation emitted by similar molecular vibration‐rotation bands and for radiation emitted by blackbodies. The results obtained for the absorptivity calculations compare favorably with available empirical correlations for H_2O. The postulated model does not apply to CO_2 and, therefore, no satisfactory theoretical formula has been derived for the absorptivities of this molecule. The appendix (by A. Thomson) is devoted to a critical examination of the limits of validity of the effective band‐width concept for...

  20. Absolute intensities for the ultraviolet γ bands of NO

    Weber, D.; Penner, S. S.
    Absolute intensities have been measured for three of the ultraviolet γ bands of NO. The corresponding electronic absorption oscillator strength is estimated to be 0.0024±0.0004.

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