Turbomachinery design described by similarity considerations

Expressions of operating conditions related to the design of turbomachinery are examined. The dimensionless field of turbomachinery design is discussed. The relationships of dimensionless design parameters such as diameter ratios, flow coefficients, head coefficients, and design choices regarding the fluid and the machine are explained. The core of the design process is said to relate such sets of design parameters to the dimensionless form of the machine. Mathematical models are provided to support the theoretical considerations

Preliminary design of turbopumps and related machinery

Pumps used in large liquid-fuel rocket engines are examined. The term preliminary design denotes the initial, creative phases of design, where the general shape and characteristics of the machine are determined. This compendium is intended to provide the design engineer responsible for these initial phases with a physical understanding and background knowledge of the numerous special fields involved in the design process. Primary attention is directed to the pumping part of the turbopump and hence is concerned with essentially incompressible fluids. However, compressible flow principles are developed. As much as possible, the simplicity and reliability of incompressible flow considerations are retained by treating the mechanics of compressible fluids as a departure from the theory of incompressible fluids. Five areas are discussed: a survey of the field of turbomachinery in dimensionless form; the theoretical principles of the hydrodynamic design of turbomachinery; the hydrodynamic and gas dynamic design of axial flow turbomachinery; the hydrodynamic and gas dynamic design of radial and mixed flow turbomachinery; and some mechanical design considerations of turbomachinery. Theoretical considerations are presented with a relatively elementary mathematical treatment

Rapid Synthesis of Sub-10 nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol® 66

We report a simple one-pot method for the rapid preparation of sub-10 nm pure hexagonal (β-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol® 66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core–shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects

(5RS,10SR,15RS)-Trimethyl­truxene1

The title mol­ecule, C30H24, was prepared as a possible precursor to buckminsterfullerene cages. The two enanti­omers adopt the anti configuration, with one S/R and two R/S methyl groups, one anti to the other two. The truxene framework is slightly non-planar: with respect to the central six-ring mean plane, the three methyl C atoms are 1.377 (3), −1.475 (3) and 1.515 (3) Å distant, whereas the respective proximate peripheral six-ring mean planes make dihedral angles of 6.27 (6), 3.45 (7) and −7.37 (7)°