||Experimental Studies on Heating and Burning of Fuel Droplets with Various Compositions
||Department of Mechanical Engineering
Free falling droplet
In this research, single drop biofuel is used to investigate the evaporation and combustion characteristics to improve the combustion efficiency of the industrial furnace. This research consists of two experiments such as single suspended droplet experiment and free falling droplet experiment. The single suspended droplet experiment is used to investigate the evaporation behaviors of the single droplet in a stationary motion at three different high ambient temperatures and the free falling droplet experiment is used to investigate the combustion behaviors of the freely falling isolated droplet in the high temperature oxidizing combustion chamber.
The suspended droplet experiment of biofuels results showed that some admiring phenomena were founded such as, expansion, micro-explosion, ejection, bubbling, char formation, and char ignition. In heavy oil series fuels, evaporation observed without char formation. For bio-oil series fuels at 400oC, after the evaporation of volatile components in the fuel char formation was observed without ignition of char particles and increasing to 500oC leads to ignition of char particles. Increasing ambient temperature will be increasing evaporation rate, and a number of micro-explosion per sec, bubbling, swelling phenomena of biofuels and reducing the initial heat absorption period, droplet lifetime.
In free falling droplet experiment result shows that the evaporation constant rate was higher for DAO fuel among other fuels. For DAO and DAO: PFO (1:1) fuel, the variation of drop squared diameter with time curve was linear. Ignition, burning, and extinction of flame were observed in the free falling droplet experiment and we observed some interesting events in the burning droplet, such as fuel jet ejection when the gas velocity and droplet velocity were similar or equal, and micro-explosion was observed after the droplet burning. For NCKU A & NCKU B fuels, there was no evaporation occurred and burning behaviors of the droplet were not observed.
Table of contents I
List of tables IV
List of figures V
1. Introduction 1
1.1 Background and motivation of the study 1
1.2 Objectives of study 3
2. Literature review 4
2.1 Biomass 4
2.2 Biomass conversion routes to energy 6
2.2.1 Direct combustion 7
2.2.2 Pyrolysis 8
2.2.3 Gasification 10
2.2.4 Liquefaction 11
2.2.5 Anaerobic digestion 11
2.2.6 Fermentation 12
2.3 Properties of bio-oil 12
2.3.1 Water 12
2.3.2 Oxygen 13
2.3.3 pH value 13
2.3.4 Heating value 14
2.3.5 Viscosity 14
2.3.6 Flash point and Pour point 15
2.3.7 Solids 15
2.3.8 Ash 16
2.3.9 Surface tension 16
2.3.10 Thermal conductivity and specific heat capacity 17
2.4 Behavior of bio-oil 17
2.5 Droplet evaporation and combustion 21
3. Experimental setup and Methodology 31
3.1 Fuel properties 31
3.2 Suspended droplet experiment 32
3.3 Free falling droplet experiment 34
3.3.1 Drop generation system 34
3.3.2 Drop combustion system 35
4. Results and Discussion 38
4.1 Single droplet evaporation 38
4.1.1 Thermal behavior of heavy oil series fuels 39
4.1.2 Thermal behavior of bio-oil series fuels 42
4.2 Free falling droplet 46
4.2.1 Flame streak 46
4.2.2 Vaporization rate 48
5. Conclusions 50
5.1 Suspended droplet experiment 50
5.2 Free falling droplet experiment 51
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