Nozzle

About: Nozzle is a research topic. Over the lifetime, 158675 publications have been published within this topic receiving 893026 citations. The topic is also known as: spout.

Nanoparticle formation using a plasma expansion process

Abstract: We describe a process in which nanosize particles with u narrow size distribution are generated by expanding a thermal plasma carrying vapor-phase precursors through a nozzle. The plasma temperature and velocity profiles are characterized by enthalpy probe measurements. by calorimetric energy balances. and by a model of the nozzle flow. Aerosol samples are extracted from the flow downstream of the nozzle by means of a capillary probe interfaced to a two-stage ejection diluter. The diluted aerosol is directed to a scanning electrical mobility spectrometer (SEMS) which provides on-line size distributions down to particle diameters of 4 nmt. We have generated silicon, carbon, and silicon carbide particles with number mean diameters of about 10 not or less, and we have obtained some correlations between the product and the operating conditions. Inspection of the size distributions obtained in the experiments, together with the modeling results, suggests that under our conditions silicon carbide formation is initiated by nucleation of extremely small silicon particles from supersaturated silicon vapor, followed by chemical reactions at the particle surfaces involving carbon-containing species from the gas phase.

Method of making supercritical fluid molecular spray films, powder and fibers

Abstract: Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a heated nozzle having a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. In another embodiment, the temperature of the solution and nozzle is elevated above the melting point of the solute, which is preferably a polymer, and the solution is maintained at a pressure such that, during expansion, the solute precipitates out of solution within the nozzle in a liquid state. Alternatively, a secondary solvent mutually soluble with the solute and primary solvent and having a higher critical temperature than that of primary solvent is used in a low concentration (<20%) to maintain the solute in a transient liquid state. The solute is discharged in the form of long, thin fibers. The fibers are collected at sufficient distance from the orifice to allow them to solidify in the low pressure/temperature region.

Static Pressure Distribution in the Free Turbulent Jet

Abstract: Measurements of mean velocity, turbulent stress and static pressure were made in the mixing region of a jet of air issuing from a slot nozzle into still air. The velocity was low and the two-dimensional flow was effectively incompressible. The results are examined in terms of the unsimplified equations of fluid motion, and comparisons are drawn with the common assumptions and simplifications of free jet theory. Appreciable deviations from isobaric conditions exist and the deviations are closely related to the local turbulent stresses. Negative static pressures were encountered everywhere in the mixing field except in the potential wedge region immediately adjacent to the nozzle. Lateral profiles of mean longitudinal velocity conformed closely to an error curve at all stations further than 7 slot widths from the nozzle mouth. An asymptotic approach to complete self-preservation of the flow was observed.

No-moving-part hybrid-synthetic jet actuator

Abstract: In contrast to usual synthetic jets, the “hybrid-synthetic jets” of non-zero time-mean nozzle mass flow rate are increasingly often considered for control of flow separation and/or transition to turbulence as well as heat and mass transfer. The paper describes tests of a scaled-up laboratory model of a new actuator version, generating the hybrid-synthetic jets without any moving components. Self-excited flow oscillation is produced by aerodynamic instability in fixed-wall cavities. The return flow in the exit nozzles is generated by jet-pumping effect. Elimination of the delicate and easily damaged moving parts in the actuator simplifies its manufacture and assembly. Operating frequency is adjusted by the length of feedback loop path. Laboratory investigations concentrated on the propagation processes taking place in the loop.