Application of linear analysis to an experimental investigation of a turbojet engine with proportional speed control Page: 2 of 39
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TECH LIBRARY KAF, NM
IA NATIONAL ADVISORY COMMITxE FOR AERONAUTICS 1IfIIIRl ilI
0065644
TECHNICAL NOTE 2642
APPLICATION OF LINEAR ANALYSIS TO AN lPERIMENTA
INVESTIGATION OF A TJRBOJFT ENGINE W~IT
PROPORTIONAL SPEED CONTROL
By Marcel Dandois and David Novik
SUMMARY
Results of an analytical and a sea-level experimental investigation
of a turbojet engine with proportional speed control are presented.
Linear analysis and description of the engine as a first-order linear
system proved adequate for analytical prediction of the response and the
stability of the controlled engine, although instability calculations
were found to be much more critical than response calculations.
On the basis of a compromise between speed of response and oscilla-
tions, an optimum loop gain was found. Increased loop gain increased the
speed of response and decreased the speed error but ultimately led to
instability characterized by an essentially constant frequency and con-
stant amplitude oscillation. Operation near the limits of stability
required a decrease in control gain with decreasing engine speed.
INTRODUCTION
A current approach to synthesis of control systems for turbojet
engines involves the techniques of linear analysis and synthesis
described in references 1 and 2 and their bibliographies. This
approach is predicated upon a knowledge of the dynamic characteristics
of the various components of the controlled system. Accordingly, con-
siderable effort has been expended in obtaining the dynamic characteris-
tics of gas -turbine engines from experimental and analytical studies
(references 3 to 6). These investigations of gas -turbine engine dynamics
indicate that the engines may be considered linear for substantial excur-
sions from steady-state equilibrium points and that within the limits of
experimental accuracy the engines appear to be first-order systems.
The adequacy of the linear techniques and data discussed in the
references may be ascertained by comparison of analytical results based
on these techniques and actual experimental data. An experimentalCre~-- 1_ --._,
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Dandois, Marcel & Novik, David. Application of linear analysis to an experimental investigation of a turbojet engine with proportional speed control, report, February 1952; (https://digital.library.unt.edu/ark:/67531/metadc56440/m1/2/: accessed April 22, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.