XL Toolboxes

Chemical Equilibrium in Excel®

Chemical equilibrium is the classic limit case of all combustion processes. As with all equilibrium processes, it represents a balance between competing mechanisms. When a system is in chemical equilibrium, the chemical reactions for production and destruction of species are occurring at an equal rate, so that the concentrations of the reacting substances do not change with time. In terms of thermodynamics, chemical equilibrium is the condition in which there is no tendency or potential to make the composition of the system change; that is, no change can occur in the system without outside work being done on the system. While there are several approaches to solving systems in chemical equilibrium, the thermodynamic approach has proven to be more powerful for general chemical systems.

Cequel^TM is a user friendly Excel Toolbox which calculates thermodynamic and transport properties for a mixture in chemical equilibrium, including the dense gas correction. This code also calculates the chemical potential, B values, for the thermochemical erosion analyses. It provides combustion performance and gas mixture transport properties for several hundred propellant combinations.

The popular FORTRAN CCET code was converted into a Microsoft Windows compatible dynamic link library (DLL) function, which is controlled by VBA. This provides a computationally intensive code which runs at a very high speed running as an add-in within the Excel/VBA platform.

General Operation

Cequel^TM contains both a spreadsheet function and wizards help the user insert an instance of the function into the spreadsheet for a specific application. The first section of both the function and the wizard allows you to select the problem type, the ingredients that are to be combusted, and the relative amounts of each ingredient. Specification of the mixture ratio(s) can be in terms of O/F, equivalence ratio, Fuel %, or Air/Fuel ratio. A tri-propellant option is also available. The second section is problem specific, allowing the user to select equilibrium properties and products.

Features

• Cequel^{TM solves TP, HP, SP, TV, UV, SV, Rocket, Detonation and Shock problems.}
• Cequel^TM is a spreadsheet function that allows input values to be named cell ranges.
• Cequel^TM eliminates the need to cut and paste output from other chemical equilibrium codes into Excel.
• Cequel^TM can be used to perform cycle analyses and optimization.
• Cequel^TM eliminates the need to cut and paste output from other chemical equilibrium codes into Excel.
• Cequel^TM can used within Excel iterative features including goal seeking, rules solving, optimization, and Monte Carlo uncertainty analysis.
• Cequel^TM can be used for engine cycle analyses which include changing chemical equilibrium within the cycle.
• Cequel^TM can be used to predict thermal engine performance, including frozen and shifting equilibrium for rockets, detonation and shock problems.
• Cequel^TM can be used in conjunction with other SpreadsheetWorld Toolboxes such as XLRocket, XLNumerical Methods, and XLProPlot.
• Cequel^TM can be used within the SpreadsheetWorld Integrated Collaborative Environment (ICE) in conjunction with SpreadsheetWorld ICE Toolboxes including XLLink, ICEMaker and Model INTegrator.

Using Cequel^TM with other XLToolboxes

The properties calculated by Cequel^TM and be used to support other SpreadsheetWorld XLToolboxes in an iterative dynamic Excel environment. For example they can be used to support thermal power systems analysis which requires the properties of mixtures of combustion gases. Calculations could include thermal engine cycle analysis, heat transfer calculations and gas dynamic flow calculations. Visual representations of Cequel^TM calculations can be effectively presented using XLProPlot.

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