Thermodynamic Cycle Simulation Software – AxCYCLE™ Overview

Note – AxCYCLE is our legacy thermodynamic cycle simulation tool. For the latest features and developments, check out our AxSTREAM System Simulation software tool, which combines the power of AxCYCLE and AxSTREAM NET into a single interface. 


AxCYCLE is a thermodynamic simulation software which allows users to quickly and easily design, analyze and optimize various thermodynamic cycles (thermodynamic simulation and heat balance calculations) in a user-friendly and flexible environment, from a restricted amount of known data.

AxCYCLE Demo – Aero Engine Video


The tasks user can solve with AxCYCLE™ include:

  • Design new thermodynamic cycles from scratch
  • Analyze existing thermodynamic systems and their performance at design and off-design conditions
  • Redesign, optimize, rerate and upgrade existing plants
  • Troubleshoot and correct efficiency/reliability issues in existing hardware



AxCYCLE™ allows performing calculations on multiple types of cycles (Brayton, Rankine, etc.) and applications (with specific components) including:

  • Fossil Steam Power Plants
  • Nuclear Steam Power Plants
  • Cooled and Uncooled Gas Turbine Plants
  • Aerospace Gas Turbines Engines
  • Combined Cycles (gas-steam, gas-sCO2, etc.)
  • Cogeneration Cycles
  • sCO2 (supercritical carbon dioxide) Cycles
  • ORC (Organic Rankine Cycles)
  • Geothermal Cycles
  • Molten Salt Cycle
  • Waste Heat Recovery Cycles and Systems
  • Heat Pumps Cycles/Refrigeration Cycles
  • Etc.


AxCYCLE has several fluid libraries:

  • General Fluids – Includes steam/water, standard air, carbon dioxide, natural gas, etc.
  • COOLPROP – Contains over 45 fluid options (free database)
  • NIST REFPROP – Propane, ethanol, refrigerants, CO2 and more (required third-party application).
  • NIST Mixture – Contains several NIST mixtures
  • Combustion Products – Includes more than a dozen typical fuels combustion product
  • Thermal Oils – Contains therminol thermal oils which can be used for indirect waste heat recovery systems
  • Molten Salts – Contains several molten salts

Additionally, custom fluids, custom mixtures and custom combustion products can be used in cycles.


Cooling flows and secondary flows can be thermodynamically analyzed using AxCYCLE by modeling the complete gas turbine with turbine, compressor, combustion chamber, extractions, injections, etc. while automatically recalculating the fluid properties at each component’s inlet and outlet.

Cycle Creation Process

Starting from the selection of components using drag-and-drop from respective libraries (turbomachine, heat exchange, engine, library of gas turbine engines, library of internal combustion engines, burner, separation, mixing, valve, seal, generator/motor, etc.), users progress with the cycle assembly as desired to model an infinite number of different systems.

After the cycle assembly the engineer needs to specify the data necessary to run calculations.

As a conceptual 0D tool, AxCYCLE uses only the basic thermodynamic parameters of the components such as pressure, enthalpy, temperature, fluid quality and basic performance parameters such as efficiency and pressure loss.

No mechanical or geometric data is required which makes it extremely convenient and adapted to investigate concepts when the components of the system have no defined characteristics as well as to study existing systems where some geometric/mechanical data may be unknown.


Each parameter in AxCYCLE can be either inputted or calculated. This allows for an enhanced flexibility of problem formulation to, for example, calculate mass flow rate or heater outlet temperature based on given boundary conditions and power requirement or specify the flow rate and boundary conditions to obtain power.

Additionally, multiple options are available for different components to be modeled in specific ways; for example heat exchangers can be characterized by their efficiency or pinch point, turbines can be conceptual or behave as per existing hardware, etc.

For steam cycles the embedded Steam Cycle Wizard tool allows simplifying the components selection, cycle assembly, property type specification and boundary conditions input through an easy-to-use interface.


Analysis & Post-Processing

Thermodynamic cycles can be analyzed at their design point or at off-design conditions to calculate power production, heat and fuel consumption, rejected heat, thrust, thermal efficiency, etc.

Embedded P-H and T-S diagrams allow reviewing the thermodynamic process of the current system and also allow superimposing the characteristics of other cycles as a mean of comparison.

AxCYCLE-analysis AxCYCLE-analysis-post

Printer-friendly simulation results (reports) can be automatically generated.

AxCYCLE systems and their components can be exported to the AxCYCLE Economics™ module to evaluate the capital costs, payback period, levelized cost of electricity, influence of renovations on ROI, etc.

AxCYCLE can also be linked to the AxSTREAM® platform to:

  • Extract boundary conditions for turbine, compressor and pump conceptual design
  • Import turbomachine performance maps to study cycle at design and off-design conditions using actual efficiency values.
Cycle Off-Design Calculations, Parametric Studies and Optimizations

In addition to design point calculations AxCYCLE includes several tools for system off-design calculation, parametric study and optimization tasks.


MAP is a multi-run tool used to run a series of calculations for one or two variables. AxCYCLE MAP is a very effective tool to study the influence of operational parameters on cycle performance. It is the ultimate tool to calculate cycle performance curves as it can automatically take into account components off-design efficiency based on the boundary conditions inputted or calculated; these include for example the dependency of efficiency on turbomachinery components rotation speed and pressure ratio, the influence of component aging, or can be used to study the effects of variations of operating conditions and component parameters on cycle performance.



AxCYCLE is fully capable of thermodynamic cycles optimization calculations including through the use of a DOE approach (Design Of Experiment) in the PLAN tool. This multivariable tool can be run for any combination of input and output parameters within dozens available (up to 20 variables can be selected at once). The DOE engine itself selects values within the provided range, in an optimized way, to minimize the number of solver runs required to optimize a cycle. The obtained results are used to build “response surfaces” that are used as abstract models for optimization.



The QUEST tool inside AxCYCLE is a quasi-random search algorithm which can be used to optimize combinations of parameters within a given range, for as many design variables as desired and for any given number of combinations of parameters. Results are plotted on a 3D design space which allows easily reviewing the best combination of values for a given task while allowing users to set filters to customize and refine the optimization task.



To study several cycle load points the AxCYCLE CASE tool is generally used. It allows users to specify the desired value for each of any number of variables to select in order to analyze how the system would behave under different conditions. For enhanced user experience AxCYCLE CASE is fitted with an option to interface to and from spreadsheets containing results and/or values for the different parameters selected. Some examples of CASE tasks include studying the performance of the given cycle upon opening or closing of valves, analyzing the required boundary conditions to obtain a given take-off vs cruise thrust for an aerospace gas turbine or hourly energy demand of a power plant.