Session: Student Poster Competition

Submission Number: 186905

Impact of Thermodynamic Property Modeling on Aero-Engine Mean-Line Design 

Mean-line methods remain a cornerstone of preliminary aero-engine design because they
enable rapid component sizing and early-stage trade studies. Despite their widespread use,
most mean-line analyses rely on simplified thermodynamic assumptions, typically treating
the working fluid as an ideal gas with constant specific heats. While such assumptions are
often acceptable at moderate temperatures, their validity becomes increasingly questionable
in high-temperature regions of the engine and in the context of emerging propulsion
concepts, including alternative fuels. The influence of thermodynamic-property modeling on
mean-line design predictions therefore warrants systematic investigation. In addition,
relatively few one-dimensional mean-line studies address the integration of alternative fuels,
motivating the inclusion of low-fidelity assessments to evaluate the feasibility of existing
engine architectures under such conditions.
This work develops a modular aero-engine mean-line design tool and applies it using a set of
modeling approaches with increasing thermodynamic fidelity. In the first approach, the
working fluid is treated as an ideal gas with constant thermodynamic properties, and station-
by-station flow quantities are obtained using standard compressible-flow relations. In the
second approach, thermodynamic properties are allowed to vary with pressure and
temperature, and the corresponding mean-line equations are closed numerically using real-
gas property evaluations from the CoolProp library. The variable-property formulation is
further extended to an exploratory hydrogen-fueled exhaust application in order to examine
how changes in exhaust-gas composition influence downstream turbine trends. In all
approaches, the stage-by-stage mean-line formulation is based on the Euler turbomachinery
equation and velocity triangle analysis. Aerodynamic feasibility is assessed using non-
dimensional parameters such as work and flow coefficients, Mach number levels, and
diffusion limits. To isolate the influence of modeling assumptions, dedicated comparison
scripts are employed to separately assess the effects of thermodynamic-property modeling
and fuel choice.
The framework is applied to a representative multi-spool turbofan architecture based on
publicly available reference data, results from a zero-dimensional (0D) thermodynamic cycle
analysis, and user-defined design choices, including inlet Mach number, inlet hub-to-tip ratio,
and assumed polytropic efficiencies. The present study is structured around two main
comparisons. First, the ideal-gas, constant-property formulation is compared against the
real-gas, variable-property formulation to evaluate how thermodynamic-property modeling
affects preliminary sizing outputs such as trends in pressure and temperature, axial annulus
area evolution, stage loading, and stage-level feasibility metrics. Second, the variable-
property formulation is extended to an exploratory hydrogen-fueled exhaust application to examine how changes in exhaust-gas composition and resulting thermodynamic property variations may influence turbine mean-line trends downstream of the combustor. At the current stage, results are being consolidated to identify and interpret the most sensitive components and stages.
In addition, a sensitivity analysis is performed using the variable-property formulation as the
baseline to assess the robustness of the mean-line design trends to key design inputs. A systematic parametric sweep is applied to selected design parameters, and the resulting changes in stage-wise quantities such as diffusion factors, work and flow coefficients, and relative Mach numbers are examined.
Overall, this work aims to clarify how thermodynamic-property modeling choices and key design assumptions influence aero-engine mean-line design outcomes. Through comparative analyses, sensitivity studies, and a low-fidelity hydrogen application, the work demonstrates the level of thermodynamic modeling detail required to obtain physically meaningful results during preliminary aero-engine design.

Presenting Author: Dimitrios Ivanoudis Aristotle University of Thessaloniki

Presenting Author Biography: Dimitrios Ivanoudis is a final-year Mechanical Engineering student at Aristotle University of Thessaloniki, Greece, specializing in aeronautics and aero-engines. His academic background includes coursework in thermodynamics, fluid mechanics, turbomachinery, aerodynamics, and computational fluid dynamics. He is currently completing his master’s thesis on aero-engine mean-line design modelling. The work examines the influence of thermodynamic-property modelling assumptions on preliminary component sizing and performance trends, including variable-property formulations and low-fidelity assessments for alternative-fuel applications.

Authors:

Dimitrios Ivanoudis Aristotle University of Thessaloniki
Konstantinos Bollas Aristotle University of Thessaloniki
Michail Psaropoulos Aristotle University of Thessaloniki
Anestis Kalfas Aristotle University of Thessaloniki