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Mathematical Models of the Transient Heat Flow to Fuel Droplets.
Herbert S Bennett1, Richard Kayser1
1Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234.
Journal of Research of the National Bureau of Standards (1977)
|September 27, 2021
Summary
This study analyzes two theoretical models for fuel droplet preheating, considering transient heat conduction. Both models accurately predict micro-explosion times, showing similar temperature profiles for emulsified fuels.
Area of Science:
- Combustion Science
- Heat Transfer
- Fuel Chemistry
Background:
- Understanding the preheat stage of fuel droplets is crucial for optimizing combustion processes.
- Emulsified fuels offer potential benefits in combustion efficiency and emissions reduction.
- Transient heat conduction significantly influences droplet behavior during preheating.
Purpose of the Study:
- To theoretically analyze two distinct models for the preheat stage of conventional and emulsified fuel droplets.
- To investigate the effects of transient heat conduction on droplet temperature profiles.
- To compare the predictive capabilities of the two models, particularly regarding micro-explosion phenomena.
Main Methods:
- Development and theoretical analysis of two preheat models for fuel droplets.
- Model 1: Temporal variation in droplet and gas temperatures; spatial variation only in gas temperature.
- Model 2: Spatiotemporal variation in both droplet and gas temperatures.
Main Results:
- Temperature gradients within oil and water droplets are found to be negligible compared to those in surrounding combustion gases.
- Temperature profiles predicted by both models exhibit strong similarity.
- Predicted times for micro-explosion occurrence show agreement within 10% between the two models.
Conclusions:
- Both analyzed models provide reliable predictions for the preheat stage of fuel droplets, including emulsified fuels.
- The simplified model (Model 1) offers comparable accuracy to the more complex model (Model 2) for predicting key phenomena like micro-explosions.
- Transient heat conduction plays a vital role, and its inclusion in models is essential for accurate combustion simulations.
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