Thermo-fluid diagnostic methods using laser-induced plasma and ultrasound wave

다국어 초록 (Multilingual Abstract)

We investigated the LIBS (laser-induced breakdown spectroscopy) characteristics in various phase conditions including single-phase (gas) and two-phase (liquid gas, solid gas) for thermo-fluid applications. For single-phase (gas) analysis, two-dimensional mapping of the LIBS signals from chemical species information was performed in propane flames with in situ diagnostics. Key combustion information, such as density, fuel concentration, and fuel/air equivalence ratio were provided by the LIBS measurement. For the two-phase spray flame, the simultaneous laser ignition and spectroscopy enabled rapidly determining the local equivalence ratio and condensed fuel concentration during the reaction. In parallel with the laser ignition, the equivalence ratio and droplet characteristics, such as concentration, size, and distribution of spray combustion, were simultaneously obtained for a feedback control system. For the two-phase aerosol analysis, LIBS detected solid carbon particulates in a flow system that was designed to replicate aircraft exhaust flow conditions. The detected signals from the emissions stream at velocities of up to 70 m/s showed that in-situ characterization of carbon particulates in the high-speed exhaust were proven feasible. The results obtained through this research will allow for more practical diagnostics in various applications such as biology, combustion and the environment.
In addition, basic research was conducted for the thermo-fluid diagnostics using LIUS (laser-induced ultrasound) waves. We demonstrated that the reduced-graphene-oxide-coated thin aluminum film (rGO-Al) and rGO-coated polydimethylsiloxane (rGO-PDMS) were effective optoacoustic transmitters for generating high-pressure and high-frequency ultrasound waves. Under pulsed laser excitation, rGO-Al and rGO-PDMS transmitters generated enhanced optoacoustic pressure that was 64 and 76 times stronger, respectively, than Al alone. Promising optoacoustic wave generation was made possible by optimizing the thermoelasticity of metal, the PDMS film and the thermal conductivity of rGO in the proposed transmitter for laser-induced ultrasound applications. LIBS and LIUS have great advantages as analytical techniques, namely, real-time rapid analysis and stand-off detection capability, which are all material phases for diagnosing thermo-fluid phenomena.

목차 (Table of Contents)

• CHAPTER 1 INTRODUCTION 1
• 1.1 Motivation and purpose 1
• 1.2 Laser-material interaction 5
• 1.2.1 Laser 5
• 1.2.2 Various phenomena in laser-matter interactions 6
• 1.3 Laser-Induced Breakdown Spectroscopy (LIBS) for Thermo-Fluid Diagnostics 10
• 1.3.1 Introduction of LIBS 10
• 1.3.2 The theory of LIBS 11
• 1.3.3 Comparison of LIBS and conventional diagnostic methods for thermo-fluid applications 17
• 1.3.4 LIBS for thermo-fluid applications 23
• 1.4 Laser-Induced Ultrasound Wave for Thermo-Fluid Diagnostics 27
• 1.4.1 Introduction of LIUS 27
• 1.4.2 The theory of LIUS 30
• CHAPTER 2 EXPERIMENTAL SETUP 34
• 2.1 Experimental apparatus 34
• 2.1.1 Laser 34
• 2.1.2 Spectroscopy 35
• 2.1.3 Hydrophone 36
• 2.2 Shadow graph 37
• 2.3 Light scattering 38
• CHAPTER 3 DIAGNOSTIC OF GAS PHASE REACTING FLOW USING LIBS 39
• 3.1 Background and objective 39
• 3.2 Experimental condition 41
• 3.3 Results 45
• 3.4 Conclusion 52
• CHAPTER 4 DIAGNOSTIC OF TWO PHASE (LIQUID-GAS) REACTING FLOW USING LIBS 54
• 4.1 Background and objective 54
• 4.2 Experimental condition 60
• 4.3 Results 62
• 4.4 Conclusion 94
• CHAPTER 5 DIAGNOSTIC OF TWO PHASE (SOLID-GAS) FLOW USING LIBS 96
• 5.1 Background and objective 96
• 5.2 Experimental condition 99
• 5.3 Data analysis 105
• 5.4 Results 107
• 5.4.1 LIBS spectra in particle stream 107
• 5.4.2 Visualization of particle and plasma 110
• 5.4.3 LIBS signal for delay time 113
• 5.4.4 LIBS signal for carbon concentration 117
• 5.4.5 Limit Of Detection (LOD) 125
• 5.5 Conclusion 126
• CHAPTER 6 DIAGNOSTIC OF LIQUID PHASE SAMPLE USING LIUS : PART 1 REDUCED GRAPHENE OXIDE COATED THIN ALUMINUM FILM 128
• 6.1 Background and objective 128
• 6.2 Experimental condition 130
• 6.3 Results 132
• 6.4 Conclusion 140
• CHAPTER 7 DIAGNOSTIC OF LIQUID PHASE SAMPLE USING LIUS : PART 2 REDUCED GRAPHENE OXIDE COATED POLYDIMETHYLSILOXANE (PDMS) FILM 141
• 7.1 Background and objective 141
• 7.2 Experimental condition 143
• 7.3 Results 145
• 7.4 Conclusion 154
• CHAPTER 8 CONCLUSION 156
• REFERENCES 158
• ABSTRACT IN KOREAN 167
• ACKNOWLEDGEMENTS IN KOREAN 169