Engineering topics

Shakkottai, Parthasarathy

Publications and source records attributed to Shakkottai, Parthasarathy.

11 records

NASA NTRS1992

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.

Shakkottai, Parthasarathy↗

NASA NTRS1992

Acoustic Device Would Measure Density Of Gas

Proposed acoustic sensor measures density of flowing gas or mixture of gases. Constructed in variety of configurations for use in monitoring industrial processes. Basic configuration, sensor comprises narrow tube closed at one end and open at other, sound transmitter located in closed end, and microphone located part way along tube. Entire sensor, or at least open end of tube, placed inside pipe or vessel containing gas, density of which measured. Transducer produces constant-velocity-amplitude sound waves at frequency lower than fundamental resonant frequency of tube.

Shakkottai, Parthasarathy↗

NASA NTRS1991

Method for the determination of lignin content of a sample by flash pyrolysis in an atmosphere of hydrogen or helium and method therefor

The lignin content of wood, paper pulp or other material containing lignin (such as filter paper soaked in black liquor) is more readily determined by flash pyrolysis of the sample at approximately 550.degree. C. in a reducing atmosphere of hydrogen or in an inert atmosphere of helium followed by a rapid analysis of the product gas by a mass spectrometer. The heated pyrolysis unit as fabricated comprises a small platinum cup welded to an electrically-heated stainless steel ribbon with control means for programmed short duration (1.5 sec, approximately) heating and means for continuous flow of hydrogen or helium. The pyrolysis products enter an electron-ionization mode mass spectrometer for spectral evaluation. Lignin content is obtained from certain ratios of integrated ion currents of many mass spectral lines, the ratios being linearly related to the Kappa number of Klason lignin.

Shakkottai, Parthasarathy↗

NASA NTRS1990

Apparatus for the remote detection of sounds caused by leaks

Two laser beams derived from a laser pass through a furnace and are superposed in a laser spot to produce interference fringes having the same pitch as that of a Ronchi grating printed on a retroreflecting screen. Minute fluctuations of the laser beams caused by sound waves from leaks result in intensity fluctuations of the laser spot when the laser fringes move past the fixed grating. A telescope and photocell arrangement detects the light variations to produce an electrical signal which is amplified and filtered to detect the sound of leaks. This non-contact laser Schlieren microphone is sensitive to sounds all along the path of the beams.

Shakkottai, Parthasarathy↗

NASA NTRS1990

Acoustic Humidity Sensor

Industrial humidity sensor measures volume fraction of water in air via its effect on speed of sound. Only portion of sensor exposed to sensed atmosphere is pair of stainless-steel tubes, one containing dry air and other containing moist air. Counters measure intervals between reflected pulses. Sensor rugged enough for use in harsh environments like those used to control drying of paper in paper mills, where most humidity sensors do not survive.

Shakkottai, Parthasarathy↗

NASA NTRS1990

Lignin Sensor Based On Flash-Pyrolysis Mass Spectrometry

New lignin sensor takes only few minutes to measure lignin content of specimen of wood, pulp, paper, or similar material. Includes flash pyrolizer and ion-trap detector that acts as mass spectrometer. Apparatus measures amount of molecular fragments of lignin in pyrolysis products of samples. Helpful in controlling digestors in paper mills to maintain required lignin content, and also in bleaching plants, where good control of bleaching becomes possible if quick determination of lignin content made.

Kwack, Eug Y.↗

NASA NTRS1990

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.

Shakkottai, Parthasarathy↗

NASA NTRS1989

Polymeric Electrolytic Hygrometer For Harsh Environments

Design of polymeric electrolytic hygrometer improved to meet need for reliable measurements of relative humidity in harsh environments of pulpmills and papermills. Redesigned sensor head features shorter, more-rigidly-held sensing element, less vulnerable than previous version to swell and loss of electrical contact. Useful for control of batch dryers in food and pharmaceutical industries.

Lawson, Daniel D.↗

NASA NTRS1989

Simulator Of Rain In Flowing Air

Report describes relatively inexpensive apparatus that creates simulated precipitation from drizzle to heavy rain in flowing air. Small, positive-displacement pump and water-injecting device positioned at low-airspeed end of converging section of wind tunnel 10 in. in diameter. Drops injected by array entrained in flow of air as it accelerates toward narrower outlet, 15 in. downstream. Outlet 5 in. in diameter.

Clayton, Richard M.↗

NASA NTRS1989

Whistle Gauge Measures Flow And Temperature

Simple, rugged gauge used to measure speed of flow and temperature of steam or other gas flowing through pipes of arbitrary diameter, from 1 to 28 in. or larger. Specially designed, instrumented whistle - has no moving parts, small, nonobstruction, operates at high temperature and pressure, and cleans itself. Does not operate at zero flow, but at moderate flows (tens of meters per second) generates intense sound for use in measurements. Consists of slanted ring groove of depth D and pressure taps in wall of pipe carrying flow to be measured. Resonant wavelength of sound generated by ring groove depends primarily on size and shape of groove and approximately equal to 4D.

Shakkottai, Parthasarathy↗

NASA NTRS1989

Evolution Of Cenospheres

Microscopy reveals changes in structure during combustion. Experiments performed to trace evolution of structures of droplets of burning fuel oil. Many droplets burn incompletely, forming cenospheres. Knowledge of structure at various stages of combustion process contributes to efforts to design equipment to burn cenospheres.

Kwack, Eug Y.↗