National Center for Combustion Research and Development

Indian Institute Of Technology Madras & Indian Institute of Sciences, Bangalore
Recent Developments in Optical Diagnostics for Fuel Spray Delivery and Particulate Emissions

Speaker : William D Bachalo, PhD,

Date : 13-06-2014 10:00 AM - 12:00 PM
Venue: Aero / NCCRD Seminar Hall

Abstract :

This talk will review the requirements and challenges associated with fuel spray injection into combustion systems including spark ignition, diesel and gas turbine combustors. Beginning with the spray formation region close to the injector, a description of the spray formation process and preferred methods for analyzing these phenomena will be reviewed. Basic shadowgraph, ballistic imaging, X-ray absorption and X-ray phase contrast methods will be discussed. The capabilities and limitations of these methods will be reviewed. Once the spray has formed, phase Doppler inter ferometry is the preferred method for acquiring measurements of the spray drop size distributions and droplet dynamics. Droplet size, velocity, number density and flux are very important measurements needed to understand the fuel-air mixing. The complexities associated with these measurements will be described along with methods developed to cope with such conditions. To be meaningful, measurements need to be made at realistic conditions of high pressures and high temperatures typical of modern combustion systems. These spray flows are characteristically injected at very high pressure and thus have very high velocity and droplet number density. High temperatures and pressures produce significant refractive index gradients that produce beam steering. Method for handling these challenging conditions will be discussed. Methods are being developed to reduce pollutant emissions including improved fuel spray delivery, enhanced fuel-air mixing, split injection, multiple injection and other strategies. As these methods are applied, there is a need to monitor the nonvolatile particulate emissions (nvPM). Laser-induced incandescence (LII) has been developed as a real time method for measuring the nvPM emissions. Recent developments in the LII technology allow reliable measurements of the soot primary particle size and soot volume ration. These measurements can be made with resolution as high as 0.05 mg/m3. The method will be described in detail. Dr. Bachalo received his Ph.D. degree in Mechanical Engineering and Aerospace Sciences at the University of California, Berkeley. He then conducted postdoctoral research at the NASA Ames Research Center on transonic and supersonic turbulent boundary layer flows with separation, both shock-induced and pressure gradient induced. To support his experimental research, he developed laser Doppler velocimetry and holographic interferometry as useful optical diagnostics. He then joined a small start-up company where he developed particle characterization methods. He invented the phase Doppler interferometry method for studying fuel sprays associated gas turbine combustion and aircraft icing. He founded Aerometrics Inc. in 1982 and grew the company into a successful enterprise based on the phase Doppler instrument development, LDV and other optical diagnostics. Beginning in 1996, he joined a start-up company as vice president of scientific affairs and set the goal of treating Type 1 diabetes. This company successfully transplanted Islets of Langerhans into laboratory animals. In 1998, he co-founded Artium Technologies, Inc., a company dedicated to producing instrumentation for particulate monitoring, aerosol measurements, and spray characterization. Dr. Bachalo has been awarded the International Tanasawa Award twice, the Marshal Award twice, and the Lefebvre Award in recognition of his contributions to spray characterization and spray combustion research and development.

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