Varying reference pressure used together with a balanced pressure pickup /a diaphragm switch/ to switch the electric output of the pressure transducer in a reference pressure line obtains precise engine cylinder pressure data from a high speed internal combustion engine

Mc Jones, R. W.

Morgan, N. E.

English

NASA Technical Reports Server

1 
December 1966	 1	 Brief 66-10470 
-	 NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Indicator System Provides Complete Data of Engine Cylinder 
Pressure Variation 
Pressure Gage 
Shut-Off Valve	 Pressure Transducer
Dual Beam Scope 
Pressure Regulator 
Bleed Valve
Balanced 
Pressure 
Switch
(A 
0 
Flywheel
Camera 
Tape Head 
The problem: 
To rapidly obtain precise engine cylinder pressure 
data from a high speed internal combustion engine. 
The technique generally used in internal combustion 
engine research employs a balanced pressure dia-
phragm pickup with a controlled reference pressure on 
one side and a cylinder pressure on the other. A 
history of cylinder pressure over a large number of 
cycles can be obtained by plotting many individual 
data points to obtain a complete picture of the cyclic 
cylinder pressure variation. 
The solution: 
Use a varying reference pressure together with a 
balanced pressure pickup (a diaphragm switch) to
switch the electric output of the pressure transducer 
in the reference pressure line. The magnitude of the 
cylinder pressure as well as a crank angle at which the 
switch opened and closed is displayed on a dual 
beam scope and photographed. The other beam of 
the scope displays crank angle position blips picked 
up by a tape recorder head from a magnetic tape 
mounted on the engine flywheel. 
How it's done: 
The reference pressure side of the balanced pres-
sure switch is initially pressurized to a level above 
peak cylinder pressure. The pressure is then allowed 
to decay at a controlled rate (with the engine running) 
while a time exposure photograph of the oscillograph 
(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=19660000469 2020-03-11T17:36:57+00:00Z
display is taken. The decaying reference pressure 
sequentially changes the crank angle position at 
which the switch is activated and each succeeding data 
point is recorded. The resulting photograph consists 
of a series of horizontal lines whose extremities repre-
sent points of cylinder pressure equal to reference 
pressure. The envelope of this series of lines provides 
a pressure—time history of cylinder pressure over the 
number of cycles which occur while the camera shutter 
is open (usually about 2 seconds).
Note: 
Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B66-10470 
Patent status: 
No patent action is contemplated by NASA. 
Source: R.W. Mciones and N. E. Morgan 
of Vickers Incorporated 
under contract to 
Lewis Research Center 
(Lewis-291) 
Brief 66-10470	 Category 05


Indicator system provides complete data of engine cylinder pressure variation

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