Combustion Toolbox in action#
The Combustion Toolbox [Cuadra et al., 2026] is a MATLAB-based thermochemical framework designed to solve problems involving chemical equilibrium for both gas- and condensed-phase species. The toolbox is composed of several modules, each of which is designed to solve a specific class of problems:
CT-EQUIL computes the thermochemical equilibrium composition of multi-component gas mixtures for prescribed set of chemical species (gaseous—including ions—or condensed phases) and thermodynamic constraints (e.g. pressure–enthalpy).
CT-SD solves steady-state shock and detonation wave problems for both normal and oblique incidence.
CT-ROCKET estimates the theoretical performance of rocket engines under highly idealized conditions.
CT-LIA predicts shock-turbulence interaction statistics using linear theory, accounting for thermochemical effects.
CT-TURBULENCE performs spectral and statistical analysis of turbulent flows, including energy spectra, Helmholtz decomposition, and turbulence diagnostics.
The framework also includes an intuitive graphical user interface (GUI), with a royalty-free standalone version available for Windows, macOS, and Linux.
There is a sixth closed-source (i.e., proprietary) module, CT-EXPLO, that estimates the theoretical properties of high explosive mixtures and multi-component propellants with non-ideal EoS. Although still under development, CT-EXPLO is distributed in its current form as the thermochemical module of SimEx [Sánchez-Monreal et al., 2022] subject to a proprietary license. Further details on this module will be provided elsewhere.
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Gallery#
Here we show some results obtained using the Combustion Toolbox.
Figure 1: Variation of the molar fractions \(X_j\) for a TP transformation of a Silica-Phenolic mixture at atmospheric pressure \((p = 1\) atm\()\) with \(T \in [200, 5000]\); line: numerical results obtained with CT; symbols: numerical results obtained with NASA’s CEA [Gordon and McBride, 1994].
Figure 2: Hugoniot curves for different molecular gases at pre-shock temperature \(T_1 = 300\) K and pressure \(p_{1} = 1\) atm [numerical results obtained with Combustion Toolbox (lines) and contrasted with NASA’s Chemical Equilibrium with Applications (CEA) code [Gordon and McBride, 1994] excluding ionization (symbols)].
Figure 3: Variation of molar fraction for a CJ detonation for lean to rich CH4-air mixtures at standard conditions \((T_1 = 300\) K and pressure \(p_1 = 1\) atm\()\); line: numerical results obtained with Combustion Toolbox; circles: NASA’s Chemical Equilibrium with Applications code [Gordon and McBride, 1994]. The computational time was of 6.68 seconds using a Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz for a set of 26 species considered and a total of 351 case studies.
Figure 4: Pressure-deflection (a) and wave angle-deflection (b) shock polar diagrams for air (79% N2, 21% O2) at pre-shock temperature \(T_1 = 300\) K and pressure \(p_1 = 1\) atm, and a range of pre-shock Mach numbers M1 between 2 and 14; line: calorically imperfect gas with ionization/dissociation; dashed: calorically imperfect gas with frozen chemistry; circles: results obtained with Cantera [Goodwin et al., 2021] within Caltech’s SD-Toolbox [Browne et al., 2008, Browne et al., 2008]; diamonds: maximum deflection angle \(\theta_{\rm max}\).