This article presents one approach to the mathematical modeling and analysis of a
turbojet engine with the primary goal of defining the transfer function and
simulation model. Extensive research on turbojet engine dynamic parameters in
the time and frequency domains has been presented. The turbojet engine transfer
function was defined based on the operation characteristics and experimental
test data, which included fuel flow, turbine rotation speed, and exhaust gas
temperature. For the turbojet engine, where the turbine rotation speed was
defined as a controlled parameter, fuel flow was used as a control parameter.
The total gain of the control object and the time constant parameters were
determined as nonlinear functions, which primarily depend on turbojet engine
mechanical characteristics and thermodynamic processes. Using the Simulink
digital simulation platform, a dynamic turbojet engine simulation was performed.
In limited operational conditions on the ground test cell, turbojet engine
acceleration and exhaust gas temperature parameters were simulated in response
to the throttle handle position step command. Under the same initial conditions,
the simulation results were analyzed and compared with the experimental test
data. With regard to dynamic behavior, the study reveals that the presented
turbojet engine mathematical model has high fidelity, where simulation results
exhibit a numeric accuracy better than 1.5%. The personal motivation for this
study has come as a problem investigation in which several turbojet engines have
severe failures in exploitation. In all cases, turbine blades were heavily
damaged due to excessive heat exposure. Before any technical solution was
implemented, the very first step was turbojet engine mathematical modeling and
dynamic analysis. The presented technical approach and results in the form of
the turbojet engine simulation model can be used in the diagnostic process,
predictive maintenance planning, and health monitoring concept.