Critical condition of inner cylinder radius for sustaining rotating detonation waves in rotating detonation engine thruster

We describe the critical condition necessary for the inner cylinder radius of a rotating detonation engine (RDE) used for in-space rocket propulsion to sustain adequate thruster performance. Using gaseous C₂H₄ and O₂ as the propellant, we measured thrust and impulse of the RDE experimentally, varying in the inner cylinder radius r_i from 31 mm (typical annular configuration) to 0 (no-inner-cylinder configuration), while keeping the outer cylinder radius (r_o = 39 mm) and propellant injector position (r_inj = 35 mm) constant. In the experiments, we also performed high-speed imaging of self-luminescence in the combustion chamber and engine plume. In the case of relatively large inner cylinder radii (r_i = 23 and 31 mm), rotating detonation waves in the combustion chamber attached to the inner cylinder surface, whereas for relatively small inner cylinder radii (r_i = 0, 9, and 15 mm), rotating detonation waves were observed to detach from the inner cylinder surface. In these small inner radii cases, strong chemical luminescence was observed in the plume, probably due to the existence of soot. On the other hand, for cases where r_i = 15, 23, and 31 mm, the specific impulses were greater than 80% of the ideal value at correct expansion. Meanwhile, for cases r_i = 0 and 9 mm, the specific impulses were below 80% of the ideal expansion value. This was considered to be due to the imperfect detonation combustion (deflagration combustion) observed in small inner cylinder radius cases. Our results suggest that in our experimental conditions, r_i = 15 mm was close to the critical condition for sustaining rotating detonation in a suitable state for efficient thrust generation. This condition in the inner cylinder radius corresponds to a condition in the reduced unburned layer height of 4.5–6.5.     

Influence of edge propagation on downward flame spread over three-dimensional PMMA samples

This systematic experimental study measures the effect of flame propagation along vertical edges on the overall downward spread of flames using Polymethyl Methacrylate (PMMA). Samples with a wide range of regular cross-sections – from triangular through octagonal – as well as irregular ones, have been used to test a large variation of internal angles. A MATLAB-based tool was used to calculate instantaneous spread rate for central and edge flames. The edge flame is shown to significantly enhance the spread rate, as much as five times, in respect to samples with no edges. This amplification is shown to depend primarily on the internal angle at the edge (the smaller the angle, the faster the flame) and fuel thickness, and not on other factors such as aspect ratio or cross-sectional area. Using a phenomenological argument, the edge propagation rate is correlated to the spread rate over an equivalent cylindrical fuel (the limiting shape with infinite edges) with an effective radius obtained from the geometry of the edges and the diffusion length scale of the solid phase. A formula for flame spread over cylindrical fuel from the literature is used to link the new results to existing models. Both thick and thin limits are shown to encompass the wide range of three-dimensional spread rate data within the effective radius (the independent variable), which can be determined from the known parameters. Based on these results, different types of cross-sectional areas can be sorted in the order of their inherent fire safety characteristics.     

Application of Fractionation Techniques to the Study of Olefin Polymerization Kinetics and Polymer Degradation

Summary: Temperature rising elution fractionation (TREF) has been regarded as a powerful technique for study of semicrystalline polymers. In this paper, two examples of unique applications of TREF were introduced. One was the study on the influence of extraction of internal donor on the variation of isospecific active sites of a MgCl₂- supported Ziegler catalyst, and the other was the estimation of the relationship between polymer micro-tacticity and degradation rate of isotactic polypropylene (iPP). The former example revealed the conversion from high to low isospecific site by the extraction of internal donors, whereas the latter showed a negative correlation between the level of isotacticity and the degradation rate. These results demonstrated that TREF was useful in these research applications.     

Photocatalytic decomposition of liquid-water on the Pt-loaded TiO2 catalysts: Effects of the oxidation states of Pt species on the photocatalytic reactivity and the rate of the back reaction

The photocatalytic decomposition of liquid water on Pt-loaded TiO₂ (Pt/TiO₂) catalysts was investigated. The results obtained by XPS and XRD measurements of the catalysts as a function of the calcination temperature as well as the photocatalytic decomposition reactions of H₂O clearly indicate that controlling the oxidation state of Pt as well as the amount of loaded Pt species are both important factors in the design of water-splitting photocatalysts having high efficiency and stoichiometry.     

Experiment at SPring-8

The GeV photon beam at SPring-8 is produced by backward-Compton scattering of laser photons from 8 GeV electrons. The maximum energy of the photon will be above 3 GeV, and the beam intensity will be 10⁷ photons/sec. Polarization of the photon beam will be 100 % at the maximum energy with fully polarized laser photons. We report the outline of the quark nuclear physics project with this high-quality high-intensity beam.     

An efficient ionization method of electrospray mass spectrometry: the development of an aromatic-cored matrix that wraps labile metal complexes through molecular recognition

Compound 1a, which possesses a triphenylene core and six tetraethyleneoxide side chains, shows efficient ionization of M(II)-containing (M=Pd, Pt) complexes in electrospray ionization mass spectrometry (ESI-MS). The molecular ion peaks [M]+, which are hardly detected under common ESI-MS conditions, are clearly observed as their [M x (1a)n]+ (n=1-4) adducts. UV-visible and NMR studies reveal that the electron-rich triphenylene core of 1a binds to the electron-deficient frameworks of the M(II) complexes in solution, giving rise to charge transfer (CT) complexes. We suggest that 1a stabilizes the complexes and promotes efficient ionization through unique donor-acceptor molecular recognition.     

Preparation and characterization of unique inorganic-organic hybrid mesoporous materials incorporating arenetricarbonyl complexes [-C6H4M(CO)3-] (M = Cr, Mo)

Unique inorganic-organic hybrid mesoporous materials incorporating arenetricarbonyl complexes [-C6H4M(CO)3-] (M = Cr, Mo) within their mesoporous frameworks have been successfully prepared by a simple CVD treatment of the phenylene-bridged organosilica mesoporous materials with metal hexacarbonyls [M(CO)6] (M = Cr, Mo). FT-IR and UV-vis investigations revealed that the arenetricarbonyl complexes exist stably even at temperatures above 473 K under vacuum.     

Preparation of titania particles utilizing the insoluble phase interface in a microchannel reactor

A stable interface between two insoluble currents in a microchannel reactor has been obtained by selecting the solvents and adjusting the flow rate; titania particles with a size of less than 10 nm could be prepared continuously on this interface; this new method shows great advantage for the control and measurement of particle sizes.     

The characteristics of laser micro drilling using a Bessel beam

A Bessel beam is suitable for laser micro-fabrication because it possesses both a micron-sized focal spot and a deep focal depth. As the influence of focusing aberrations is much smaller than that of a convex lens, the generation of a Bessel beam using an axicon is very practical. In the case of laser micro drilling of austenitic stainless steel with a Bessel beam, suitable processing conditions were investigated. The threshold fluence to make a through hole increased with an increase in the sample thickness. For samples with the same thickness, the threshold fluence increased with an increase in the crossing angle. A small crossing angle Bessel beam can drill a deep hole with a small threshold fluence. A through hole with a diameter smaller than 10 μm can be made on a stainless steel sheet 20 μm thick by using a Bessel beam with a large crossing angle. The taper of the hole drilled with the Bessel beam is smaller than that with the focused beam from the convex lens. PACS 52.38.Mf; 42.62.Cf; 42.79.Bh