Abstract:
A
computer model of the J-85 gas turbine engine has been used in a
investigation for potential benefits in performance simulation, arising from the adoption
of
compressor stage stacking models. The eight-stage, axial flow compressor of the
engine was simulated by means of two separate stage stacking methods: the Howell
program and the projects code, the latter being developed on the basis of the pre-existing
J-85 complete engine simulation model.
Results obtained from the use of the Howell program generally support its
suitability for the prediction of single stage and overall compressor performance. This
includes the
capability of the code to render the effect from the Variation of specific
design parameters and from the incorporation of variable geometry. Certain weaknesses
originating from the empirical nature and the logic of the program are identified.
Recommendations for the assessment of the validity of produced results, a well as
modifications for the
improvement of the code, are proposed.
The
projects stage stacking code was tested with sets of stage characteristics
derived from different
techniques. The produced results depend on the topology and
shape of the utilised characteristics. A special feature embedded in the program's logic
denotes the
tendency of individual stages to work within their stall areas or below the
hypothetical choke points of the corresponding characteristics. Although in certain
instances the
predicted overall compressor performance appears satisfactory, analysis of
results in individual
stages indicates the need for improvement of the code, in order to
obtain a closer
approach to the physical mechanism and the associated limitations of
stage matching. This is also true for the prediction of variable geometry effects on the
overall
compressor performance.
The
complete engine simulation model incorporating the projects stage stacking
code
provides generally satisfactory results, a compared to those produced by a
equivalent model of the Cranfield's Turbomatch Scheme. Specific problems encountered
are attributed to certain weaknesses of the embedded stage stacking code, which is
susceptible of improvement as already reported.
