Detonability of simple and representative components of pyrolysis products of kerosene: pulsed detonation engine application

The use of liquid fuels such as kerosene is of interest for the Pulse Detonation Engine (PDE). In this context, a representative gaseous mixture of the lighter products resulting from the decomposition of a kerosene of type JP-10 was studied. The detonability limits of simple components (hydrogen, ethylene, propylene) and mixtures of these components were tested in a 50 mm diameter and 2.5 m long detonation tube. This dimension is compatible with the applications of the aircraft industry and more particularly the PDE. The influences of the nitrogen dilution, geometry of the DDT device (Schelkin spiral), ignition energy and initial pressure were investigated. This paper was based on work that was presented at the 19th International Colloquium on the Dynamics of Explosions and Reactive Systems, Hakone, Japan, July 27 - August 1, 2003. Communicated by J.E. Shepherd     

Surface deformation measurements of a cylindrical specimen by digital image correlation

Planar digital image correlation has been extended to measure surface deformations of cylindrical specimens without physical contact for high-temperature situations. A single CCD camera acquires the surface image patterns of a section of a specimen in the undeformed and deformed states to determine two-dimensional displacements on a projection plane. Axial, circumferential and shear deformations are determined through curvature transformation on the two-dimensional projection displacement field. The resolution of this technique was determined for a cylinder of 22.23-mm diameter to be 3.5 μm for the axial displacement, 0.05 percent for the axial and shear strains and 0.08 percent for the circumferential strain when correlation computations are carried out over a field of 5 mm×5 mm.     

Fluctuations of the flow parameters of an incompressible viscous fluid in a collar-type flow throttling device

The flow in channels of the labyrinth seal type with one or two throttling stages is calculated on the interval of Reynolds numbers Re from 1.9·10⁴ to 4.5·10⁵. The nonsteady flow structure and the distribution and fluctuations of the pressure on the body of the labyrinth are investigated. The results are compared with the data of a physical experiment.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 3–8, January–February, 1990.     

Frictional instability of a train of elastically connected bodies

Leningrad State Steelworks Research and Design Institute. Leningrad Mining Institute. Translated from Prikladnaya Mekhanika, Vol. 25, No. 7, pp. 110–115, July, 1989.     

Assessment of a quintuple hotwire measurement technique for highly turbulent flows

A five-wire calibration and measurement technique is presented, which is an extension of the four-wire method developed by Döbbeling et al. (1990a, b). From numerical simulations of the uniqueness domain and the angular resolution it is concluded that the uniqueness domain of the quintuple technique can be expanded to a hemisphere as opposed to the four-wire techniques which are restricted to a conical domain of about 40° half angle. Measurements of the mean velocities and Reynolds stresses in a low-turbulence jet and in grid turbulence confirm and complement the results of the numerical simulations. It is thus shown that the quintuple method achieves increased accuracy in an expanded measurement range.The work of D. Hölzer, student of engineering at the University of Karlsruhe, and the support of W. Paulat and W. Pfeffinger in writing the data aquisition software, and H. Klette who manufactured the probe, is gratefully acknowledged. This work was supported by the Deutsche Forschungsgemeinschaft within the framework of the Sonderforschungsbereich 167, Hochbelastete Brennräume- Stationäre Gleichdruckverbrennung, Teilprojekt A10.     

Accuracy of thermocouples in radiant-heat testing

Results of an investigation of the accuracy of iron-constantan thermocouples in measuring transient surface temperatures produced by radiant heating on metallic specimens are given. The criterion of thermocouple accuracy was derived from the theory of heat conduction. The thermocouples were tested on metallic specimens of different thicknesses at varying heating rates. Comparison of these results with analytical criteria permitted quantitative determination of thermocouple errors.     

Acoustics and dynamics of coaxial interacting vortex rings

Using a contour dynamics method for inviscid axisymmetric flow we examine the effects of core deformation on the dynamics and acoustic signatures of coaxial interacting vortex rings. Both “passage” and “collision” (head-on) interactions are studied for initially identical vortices. Good correspondence with experiments is obtained. A simple model which retains only the elliptic degree of freedom in the core shape is used to explain some of the calculated features.