Laser-based Diagnostics

Laser-based diagnostics: The research objective is to continually develop cutting-edge laser-based diagnostic tools to visualize combustion flow fields in high-pressure and high-temperature combustion systems to support on-going projects. High-power 10 Hz pulsed Nd:Yag laser (Continuum Surelite III) with fundamental (~850 mJ/pulse at 1064 nm), second (~450 mJ/pulse at 532 nm), third (~250 mJ/pulse at 355 nm), and fourth (~120 mJ/pulse at 266 nm) harmonic generators is installed in the lab. The continuous wavelength (CW) multiline Argon-Ion laser (Coherent Innova70) at a nominal power of 5 W is installed for laser extinction to measure soot concentrations. TSI PIV system for the velocity measurement is also available in the department. The high spectral resolution spectrometer (Andor Shamrock i303 Spectroscopy) with two turret systems equipped with the gratings ranging from 150 groove/mm to 1800 groove/mm is integrated with the intensified charged-coupled device (ICCD) camera (Andor iStar (PCI) 3651) to gate down to 50 ns. Additional ICCD camera (PCO DiCamPro) and CCD camera (PCO SensiCam) are available for visualization of transient flame structure combined with laser diagnostics. The high-speed camera (Photron SA1.1.) is also available for the high-speed visualization imaging. Dr. Lee’s group developed and applied various combustion laser diagnostics including laser-induced incandescence (LII) of soot, coherent anti-Stokes Raman scattering (CARS) of temperature, scattering, laser extinction of soot and species, laser-induced fluorescence (LIF) of CH2O radical, schlieren and shadowgraphy of shock wave, etc., to harsh combustion environments. His current interest in laser diagnostics includes the PLII of diesel spray soot formation and laser-induced exciplex fluorescence (PLIEF) of the time-resolved vapor and liquid phase measurement in the GDI spray combustion and laser-induced breakdown spectroscopy (LIBS) of equivalence ratio measurement.

Figure: Laser setup for MIE scattering and PIV measurement in combustion vessel.                            (Click the picture to enlarge)

Figure: PLIEF measurement of liquid and vapor GDI spray.

Figure: PLIEF measurement of liquid and vapor GDI spray (Click the picture to enlarge)

 

Figure: PLII and Mie of soot particles.(Click to enlarge the picture)

Figure: PLII and Mie of soot particles.                             (Click to enlarge the picture)