Microgravity Spherical Droplet Evaporation and Entropy Effects

Area of Science:

• Combustion Science
• Chemical Kinetics
• Thermodynamics

Background:

• Low-temperature combustion (LTC) requires improved chemical kinetic mechanisms, particularly in the negative temperature coefficient (cool flame) regime.
• Microgravity droplet combustion offers a unique environment to study combustion chemistry by minimizing buoyancy and momentum effects.
• Reduced heat transfer losses and lower entropy generation are key characteristics of the LTC regime.

Purpose of the Study:

• To investigate fundamental low-temperature combustion (LTC) chemical kinetic pathways using microgravity droplet combustion.
• To provide a comprehensive derivation of the conservation of entropy equation in spherical coordinates for microgravity droplet combustion.
• To offer a foundational resource and numerical model for researchers entering the field of LTC.

Main Methods:

• Simulating the entropy equation for spherical droplet combustion under microgravity conditions.
• Deriving the conservation of entropy equation in spherical coordinates.
• Comparing the established d² law analytical model with experimental data.
• Developing a numerical model incorporating entropy.

Main Results:

• Novel findings indicate that lower entropy generation, alongside diminished heat transfer losses, can define the LTC regime.
• The study highlights shortcomings of the traditional d² law when compared against experimental data.
• A numerical model including entropy was developed and validated.

Conclusions:

• Simulating entropy generation in microgravity droplet combustion is crucial for understanding LTC chemical kinetics.
• The provided framework and numerical model serve as a valuable starting point for future research in LTC.
• Further development of the d² law is suggested based on experimental comparisons and entropy considerations.