<p>A comprehensive one-dimensional combustion solver, which allows to solve isolator, combustor, and nozzle flow and reacting mechanism together, has been developed to facilitate the design and analysis of dual-mode scramjet combustors. This reduced-order solver aims to provide fast and efficient solutions for numerical analyses, making use of quasi-one-dimensional governing equations and incorporating models for combustion, mixing, and internal instabilities including ram-to-scram transitions and thermal choking. The solver is particularly valuable for meeting the growing demand for designing scramjet engines capable of achieving a wide range of flight missions. To address the requirements for fast convergence in multiple simulations, the solver uses specified flight conditions as inputs and outputs critical information on flow variables, thrust, and thermal choking. The simulation results demonstrate how thrust, and combustion modes are influenced by the equivalence ratio and flight conditions. The solver's accuracy has been validated through comparisons with zero-dimensional combustion results from existing references, as well as pressure profiles from HyShot-II experimental data. The analysis aligns well with experimental data but reveals discrepancies attributed to limitations in 1-D simulations, including the lack of complex structural modeling such as bleed slots and shock assumptions in the pseudo-shock method. The study considers the use of hydrogen and kerosene as fuels, with simulations conducted across three distinct flight missions. For hydrogen fuel, the simulations show mode transitions at certain equivalence ratios due to significant heat addition in the combustor. In contrast, kerosene fuel combustion exhibits lower reaction and heat release rates, resulting in lower thrust and efficiency. These differences highlight the impact of fuel type on flight performance and should be considered during combustor design.</p>