Fuel Tracer Laser Induced Fluorescence for Droplet Liquid Vapor Visualization

Transcription

1 Fuel Tracer Laser Induced Fluorescence for Droplet Liquid Vapor Visualization Presenter: Keisuke Sato Mentor: Dr. Terrence Meyer 1

2 Motivation Combustor inside engine Droplet & Vapor cloud Vapor cloud Droplet Source: Computational Flow Physics Laboratory, Apte Research Group Understand the fuel droplet vaporization process in engine cycle. In order to achieve this, concentration of fuel vapor needs to be measured. Technique, Planar Laser Induced Fluorescence (PLIF) is used. 2

3 Fluorescence & Phosphorescence Energy Diagram Higher Energy Fluorescence: Radiative transition between electronic states of the same multiplicity. Phosphorescence: Radiative deactivation process between electronic states of different multiplicity. Source: Alexandros Charogiannis & Frank Beyrau, Exp Fluids,

4 Oxygen Quenching Effect Higher Energy Source: Alexandros Charogiannis & Frank Beyrau, Exp Fluids, 2013 For many tracer molecules, there is a strong quenching effect of local oxygen. It extinguishes the phosphorescence. The amount of oxygen dissolved needs to be controlled in order to take images. 4

5 Goal of Project 1. Design the fluid system so that the amount of oxygen dissolved in fuel tracer can be controlled quantitatively and repeatedly. 2. Measure the lifetime of fluorescence by varying the amount of oxygen that is dissolved. 5

6 Fluid System Diagram N2 Fuel Tracer in Bath Gas N2 Coflow Cylinder Seeding Tank O2 + fuel tracer 6

7 Fluid System Diagram N2 Fuel Tracer in Bath Gas N2 Coflow Cylinder Seeding Tank N2 + fuel tracer O2 Through mass flow controller 7

8 Experimental Setup Fourth harmonic of Nd: YAG laser is used for fluorescence and phosphorescence. The set of two lens focuses to thin collimated beam sheet at the degassed fuel vapor. Images are taken by Intensified Charge Coupled Device Camera. Wavelength 266nm PIMAX 2 fuel tracer N2 8

9 Sample fluorescence image Fluorescent is caused by Nd:YAG laser. Sample (Tuluene) is ejected from nozzle. Images are taken by ICCD camera and processed by MATLAB. The red region shows the higher intensity. 9

10 Results 3.7% Toluene, Balance N2 mixed with O2 fractions S FL (t) Ae t/ The lifetime of fluorescence is clearly dependent on the local oxygen. Higher the percentage of oxygen decays faster. 10

11 Toluene Fitted exponential lifetimes Sparged N2 seeded with 3.7% toluene and diluted with O2/N2 mixture Lifetime VS amount of oxygen dissolved. When there is no oxygen, the lifetime is the longest. In the condition of air, the lifetime is quite short. Error bar is as small as the size of a dot. 11

12 Future Work Heat the fuel tracer and take the data of lifetime. Measure the lifetime of phosphorescence of droplet by using droplet generator (20 micron). These give the idea of the vaporization process of fuel tracer. 12

13 Combustor inside engine Droplet & Vapor cloud Vapor cloud Droplet Source: Computational Flow Physics Laboratory, Apte Research Group Understand the fuel droplet vaporization process in engine cycle. In order to achieve this, concentration of fuel vapor needs to be measured. Technique, Planar Laser Induced Fluorescence (PLIF) is used. 13

14 Acknowledgement I would like to give a big thank to the following people who have involved this project!! Dr. Terrence Meyer (Professor) Dr. James Michael (Post doctor) Chloe Dedic (PhD student) Cameron Hansen (Freshman honor) Air Force Office of Scientific Research 14

15 Question? 15