###### Abstract  
[PERSON]'s 'Diffusion Theory', less investigated due to its limited international visibility, can offer one of the simplest and, on the other hand, high-accuracy methods for evaluating the ignition delay of fossil fuel and biofuel droplets, including their blend. In this study, experimental pre-tests were conducted to determine pre-existing subject knowledge on stationary droplet combustion at ambient pressure and temperatures varying from 935 to 1010 K followed by simulation of droplet ignition times. The test fuels were mineral diesel (DF), RME and a 20% RME blend with DF. Simulations were performed for isobaric conditions. Using the detailed transport model and detailed chemical kinetics, the necessary rearrangements were made for the governing equations to meet the criteria for modern fuels (biodiesel, diesel, and blend). The influence of different physical parameters, such as droplet radius, or initial conditions, on the ignition delay time was investigated. The high sensitivity of the proposed methodology to experimental results was substantiated. g 2025 26 June 20251 1 July 2025  
ing reactions whose active site generates the appearance of two or more active centers, and in-depth and detailed examination of explosions and combustion. After the 1930s extensive studies in the field of reaction kinetics became an indispensable part of flame propagation theory. The lack of experimental data at this time gave momentum to the formation of theoretical knowledge in the scientific works of [PERSON] [3,4], [PERSON] [4,5], [PERSON] [5] and [PERSON] [6]. Among the very first experimental works carried out to investigate the combustion of an isolated fuel droplet belong to Godsave [7, 8, 9], Kumagai and Isoda [10] and Spalding [11], which were later reviewed in refs [12, 13, 14, 15, 16, 17] and became what we call today 'the classical theory of droplet combustion' [13, 18]. Two typical cases of droplet combustion are distinguished. The first is the combustion of liquid fuels in a high-pressure oxidizing medium (near critical conditions), the so-called bipppollant droplet combustion [19]. Being the subject of a variety of research works, this form of combustion is used extensively in practical applications [20, 21]. The second is the combustion of monopropellants, such as nitromethane, which has its own oxygen supply [22]. This study focuses specifically on the combustion of spherically symmetric droplet combustion under normal gravity conditions, since the real combustion of diesel fuel, rapeseed oil methyl ester (RME) and their binary blends usually takes place under normal, rather than reduced (or zero) gravity environments. As discussed in [13], there are various types of research done under prescribed conditions, including, but not limited to, the \(D^{2}\)-law of droplet evaporation [23, 24, 25, 26], the \(D^{n}\)-law of droplet evaporation (where \(n=8/3\)) [26], droplet evaporation in a finite domain [27], droplet ignition [28, 29], burning rate [30, 31] of different single component [32] and multicomponent [33, 34, 35] fuels. Having analyzed typical cases of mathematical modelling of the droplet burning process described in the classical combustion theory, it was established that those methods had two main shortcomings:  
* Many mathematical calculations were performed using pure hydrocarbons: n-heptane, n-pentane, and n-hexane, motivating the fact that those fuel types were best investigated [6, 9, 10, 11, 14, 17]. Thus, the flammability features of certain investigated fuels of fossil origin are often established by approximation, taking numerical values of the required parameter of a hydrocarbon compound closest to its chemical composition. Such an attitude introduces calculation errors and aggravates the establishment of flammability features of blended fuels. * Some of the so-called advanced models presented by the authors who investigated droplet burning theory are very complicated [16, 36, 37, 38, 39].