2,297 research outputs found

    Correlation of spray dropsize distribution and injector variables

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    The atomization characteristics of impinging stream rocket engine injection elements are studied to determine the effects of hydraulic and geometric parameters on the mass median drop size. The major conclusions are: (1) the velocity profile of impinging jets affects mean drop size, this effect is greater when the jets are laminar than when they are turbulent; (2) the drop size/injection velocity dependence for turbulent jet impingement differs from that obtained with non-turbulent jets; (3) the level of turbulence intensity does not affect mean drop size; (4) the impingement of disintegrated or nearly disintegrated jets substantially decreases atomization; and (5) even though an emulsion is formed when immiscible jets impinge, the level of emulsification is small

    Effect of cement grade and fineness of slag on the early age to medium term properties of binary blends

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    The hydration and microstructural evolution of cementitious materials are dependent on both the mineralogical and physical attributes of the constituent materials. This paper ascertains the influence of constituent materials’ fineness on hydration and the evolution of mechanical properties of CEM I-slag composite cements. The clinker to supplementary cementitious material ratio was maintained at 50:50 and the sulphate content kept constant in all mixes. Compressive strength development was followed over time, with hydration followed by isothermal calorimetry and chemical shrinkage. Results from these techniques show that, for a given clinker, a more finely ground slag was consistently superior to a coarser slag. Furthermore, calorimetry revealed that the intensity of alite hydration and the secondary peak attributable to participation of aluminates from slag in hydration were also greater when using a finer slag. Finely ground clinker also accelerates slag hydration. The early age strengths in the binary blends were weaker than the control specimens, but this was offset beyond 7 days when using finer slag blends. Blending of higher grade CEM I (52.5R) and fine slag also yielded comparable early age strength to a CEM I- 42.5R mix

    Effect of cyclic freezing and thawing on the microstructure of composite cements

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    Mixed performance of composite cements exposed to freeze-thaw has been reported. A detailed understanding of the degradation mechanism is also lacking. This study investigates the microstructure of composite slag cements with and without limestone subjected to cyclic freezing and thawing. Freeze-thaw was assessed on concrete samples in accordance with CEN/TR 15177 but with a modified temperature profile. Microstructure was characterized by SEM and thermogravimetric analysis. The results indicate decalcification through carbonation and then leaching as dominant degradation mechanisms. This has implications on the pore structure and hence the water suction capacity and progression of the ice-front in concrete

    Determining the influence and effects of manufacturing variables on sulfur dioxide cells

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    A survey of the Li/SO2 manufacturing community was conducted to determine where variability exists in processing. The upper and lower limits of these processing variables might, by themselves or by interacting with other variables, influence safety, performance, and reliability. A number of important variables were identified and a comprehensive design experiment is being proposed to make the proper determinations

    Collective Quadrupole Excitations in Transitional Nuclei

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    The generalized Bohr Hamiltonian was used to describe the low-lying collective excitations in even-even isotopes of Ru, Pd, Te, Ba and Nd. The Strutinsky collective potential and cranking inertial functions were obtained using the Nilsson potential. The effect of coupling with the pairing vibrations is taken into account approximately when determining the inertial functions. The calculation does not contain any free parameter
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