Generator is an inlet-area-modulated, gas-flow-through device utilizing hydrogen gas and a rotating disk for operation. Design enables generator to produce pressure oscillations as high as 120, 18, and 12 percent of the mean chamber pressure at frequencies of 1, 10, and 15 kHz, respectively

Robinson, R. E.

English

NASA Technical Reports Server

Outlet Orifice 
I Monitor 
Transducer 
Inlet 
Orifice 
Perforated Disc
Inlet Tube 
Gas 
November 1970	 Brief 70-10635 
NASA TECH BRIEF C 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
High Amplitude Sinusoidal Pressure Generator 
A sinusoidal pressure generator capable of genera-
ting large-amplitude, high-frequency pressure fluctua-
tions at high average static pressures has been built 
and tested. The generator is capable of producing pres-
sure oscillations as high as 120%, 18% and 12% of the 
mean chamber pressure at frequencies of 1, 10 and 
15kHz, respectively. Mean pressure of the chamber 
can be varied from 15 psia to 1500 psia. 
Transducer 
Under Test Chamber 
-	 Gas 
C111110 
Inlet-Area-Modulated Sinusoidal Pressure Generator 
The generator is an inlet-area-modulated, gas-flow-
through device using a rotating disc. It is similar in 
operation to a sinusoidal pressure generator pre-
viously described in NASA Tech Brief 66-1003 1. How-
ever, the newer generator varies the area of the inlet 
to the chamber rather than the outlet area, and thus 
is able to produce the high amplitudes described 
above. Also, this generator uses hydrogen gas for 
operation rather than helium. Hydrogen offers higher 
frequency and better waveshape capability because 
of its higher speed of wave propagation (speed of 
sound). The dynamic pressure at a given frequency and 
average chamber pressure are also highest for hydro-
gen because they are a function of the gas constant 
and the specific heat ratio. 
The inlet-area-modulated generator is illustrated 
in the figure. Pressure oscillations in this type of 
generator are produced by controlling the gas flow 
into and out of a chamber. The pressure in the cham-
ber is sensed by the test transducer and by a standard 
transducer. Sinusoidal pressure variation is obtained 
by varying the mass flow through the chamber in a 
sinusoidal manner as a function of time. This is done 
by varying the flow area to the chamber by rotating 
a circular disc, with holes located along a circle near 
the disc periphery, against the inlet nozzle throat. 
Rotation of the disc alternately blocks and opelis the 
flow area. Pressure differences across the chamber 
are minimized by keeping the chamber dimensions 
smaller than the wavelength of the sinusoidal oscilla-
tion being generated. Thus, pressure wave propagation 
phenomenon is minimal. The chamber pressure change 
is therefore quasi-steady and is an expansion-compres-
sion phenomenon. 
Notes: 
I. The need for calibrating pressure transducers under 
these conditions was prompted by studies of high-
frequency combustion instability in rocket engines. 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19700000615 2020-03-17T01:01:49+00:00Z
Other needs have also arisen, such as the quieting 
of advanced aircraft engines, experiments with 
fluidics, and the upgrading of internal combustion 
engine technology. 
The following documentation may be obtained 
from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-CR-72656 (N70-23287), Development 
of a Sinusoidal Pressure Generator for 
Pressure Transducer Dynamic Calibration
Technical questions may be directed to:

Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: TSP70- 10635 
Patent status: 
No patent action is contemplated by NASA. 
Source: Richard E. Robinson of 
Battelle Memorial Institute 
under contract to 
Lewis Research Center 
(LEW-1124 1) 
Brief 70-10635	 Category 07 %


High amplitude sinusoidal pressure generator

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