Acoustic device and method for measuring gas densities

Density measurements can be made in a gas contained in a flow through enclosure by measuring the sound pressure level at a receiver or microphone located near a dipole sound source which is driven at constant velocity amplitude at low frequencies. Analytical results, which are provided in terms of geometrical parameters, wave numbers, and sound source type for systems of this invention, agree well with published data. The relatively simple designs feature a transmitter transducer at the closed end of a small tube and a receiver transducer on the circumference of the small tube located a small distance away from the transmitter. The transmitter should be a dipole operated at low frequency with the kL value preferable less that about 0.3

Aeroacoustic flowmeter

The flowmeter is based on a measurement of phase difference between two points on the circumference of a pipe separated axially by an integral multiple of sound wavelength. Plane sound waves are generated aeroacoustically by a non-protruding ring cavity energized either directly by the flow or by a subsidiary flow of the same medium. The frequency of the aeroacoustic source varies with temperature and therefore the temperature can be obtained. In the case of steam flow, temperature can be measured independently and therefore from the measured frequency (or speed of sound), the quality of wet steam can be measured. The flowmeter is linear in velocity and no calibrations are required

I. The transient boundary layer produced by a sink on a plane wall. II. Flow of dusty gases

Part I: The solution for the problem of the transient boundary layers generated by a sink on a plane wall is obtained by an integral method. The incompressible flow is similar and the similarity solutions are obtained for the two dimensional and axisymmetric cases. The velocity layer reaches a steady state and the thermal layer does not. For large times, when the thermal layer is much thicker than the velocity layer, a solution for the temperature field is obtained ignoring the velocity layer. With some approximations to the flow near the sink, similar solutions for compressible flow are also obtained. Part IIa: By using the integrated equations of motion, the development of a laminar, two-dimensional, dusty jet issuing from a slit is considered. The solutions are simple in the limits τ → 0 and τ → ∞, where τ is the particle relaxation time. For arbitrary τ, a numerical example is given. With some assumptions, the turbulent dusty jet is also considered. Part IIb: There are three parameters in the problem of steady motion of a dusty gas around a sphere. These are the Reynolds number R, particle parameter σ and the mass concentration of dust f[subscript ∞]. Solutions are obtained by the perturbation method by expanding in terms of R with σ or σ/R fixed, in the limit R → 0. Solutions are also obtained for the limit R tending to infinity with f < < 1. In both cases critical values of σ exist, below which the sphere does not capture dust. The efficiency of capture as a function of σ is calculated in both cases