A reactive quasi-two-dimensional (quasi-2D) throughflow model of a shockwave turboreactor for steam cracking is presented in this work as a fast, physics-based tool to support and accelerate the decarbonisation of the petrochemical industry [1]. While less detailed than full three-dimensional (3D) computational fluid dynamics (CFD) [2], the quasi-2D formulation retains the key meridional-plane flow physics [3]. The computational effort is thereby reduced to minutes per case rather than the days or weeks typical of 3D CFD, making it an ideal tool for swift preliminary parametric screening and optimisation. The proposed methodology solves the Euler and species-transport equations in the radial and axial directions using a pseudo-transient finite-volume formulation. Blade–flow interactions are represented via source terms based on local velocity triangles, with deviation angles and loss factors estimated empirically. Steep thermochemical gradients are resolved using a fifth-order Weighted Essentially Non-Oscillatory (WENO-5) discretisation scheme. Validation is performed against 3D reactive CFD across multiple turboreactor architectures and operating conditions. The results demonstrate that the quasi-2D model accurately reproduces key aerothermochemical flow features at a fraction of the computational cost. Overall, the proposed approach provides an efficient tool for preliminary turboreactor analysis, enabling rapid exploration of feasible configurations and accelerated decision-making. REFERENCES [1] R. L. Johnson, M. C. Akkurt, M. Bonheure, D. Laboureur, T. Verstraete, and K. M. Van Geem, “Flow dynamics in an electrified shockwave turboreactor diffuser,” Chem. Eng. J., vol. 513, p. 162238, 2025, doi: 10.1016/j.cej.2025.162238. [2] N. Karefyllidis, D. Rubini, B. Rosic, L. Xu, and V.-M. Purola, “Axial energy-imparting turbomachine for high-enthalpy gas heating,” J. Turbomach., vol. 146, no. 3, 2023, doi: 10.1115/1.4063928. [3] X. Liu, K. Wan, D. Jin, and X. Gui, “Throughflow-based simulation tool for preliminary compressor analysis,” Appl. Sci., vol. 11, no. 1, 2021, doi: 10.3390/app11010422. [4] O. Léonard and O. Adam, “Quasi-one-dimensional CFD model for multistage turbomachines,” J. Therm. Sci., vol. 17, no. 1, pp. 7–20, 2008, doi: 10.1007/s11630-008-0007-z. [5] K. Grogan and M. Ihme, “StanShock: Gas-dynamic shock-tube modeling with non-ideal effects,” Shock Waves, vol. 30, no. 4, pp. 425–438, 2020, doi: 10.1007/s00193-019-00935-x.