Final Report: Instrument Development for Real-Time Measurement of Particulate Concentration and Primary Particle Size in Diesel Engine Exhaust Using a Novel Implementation of Laser-Induced IncandescenceEPA Contract Number: 68D03040
Title: Instrument Development for Real-Time Measurement of Particulate Concentration and Primary Particle Size in Diesel Engine Exhaust Using a Novel Implementation of Laser-Induced Incandescence
Investigators: Bachalo, William D.
Small Business: Artium Technologies Inc.
EPA Contact: Manager, SBIR Program
Project Period: May 1, 2003 through April 30, 2005
Project Amount: $224,985
RFA: Small Business Innovation Research (SBIR) - Phase II (2002) Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , SBIR - Monitoring , Small Business Innovation Research (SBIR)
The objective of this SBIR project was to research and develop a laser-induced incandescence (LII) measurement tool, the LII 200. As an emerging technology, the LII 200 is a real-time measurement technique that can be used for in-situ measurement of particulate emission in engine exhaust. The instrument also can be used with sampling lines.
With the LII 200, the soot within the laser beam path is heated rapidly using a pulsed laser source with duration typically less than 20 ns. The soot is heated from the local ambient soot temperature to approximately 4000-4500 K, equal to the soot vaporization point or sublimation temperature. The incandescence from the soot particles is measured using collection optics and photodetectors. With appropriate calibration and analysis of the incandescence signal, information on the soot volume fraction and primary soot particle size may be obtained. The LII 200 method is largely non-intrusive and is capable of making in-situ measurements over a very large range of soot concentrations, both in flames and under ambient conditions.
With the support of SBIR funding from the U.S. Environmental Protection Agency (EPA) and the National Aeronautics and Space Administration (NASA), Artium Technologies, Inc., has developed a fully integrated, rack-mountable/portable, LII 200 system for soot particulate characterization in various applications. The focus of this effort was to: (1) further develop the LII 200 and demonstrate its capability in a variety of applications to support commercialization efforts; (2) develop a rugged instrument suitable for on-board vehicular testing; (3) investigate techniques to increase the measurement sensitivity by at least one order of magnitude; and (4) incorporate soot aggregate size measurement capability.
This research project was aimed at further developing the LII 200 instrument and verifying its suitability for particulate matter (PM) measurement in a variety of applications, including: (1) carbon black measurement and process control; (2) diesel, gasoline, and jet engine PM emissions in laboratory environments; and (3) soot emissions in on-board road testing. The results obtained during the Phase II testing period clearly demonstrate the accuracy, precision, repeatability, reliability, ruggedness, and turn-key operation of the LII 200 system. The research demonstrated that the LII 200 has emerged as a robust instrument for the real-time measurement of soot volume fraction/soot concentration and primary particle size.
Artium Technologies also investigated numerous enhancements to the LII, aimed at reducing the lower detection limit of soot volume fraction and increasing overall measurement sensitivity to meet new EPA regulations expected in 2007. Artium’s target objective was to improve the overall sensitivity of the technique by at least two orders of magnitude—from a previous detection limit of 5.0 ppb to a new detection limit of 0.05 ppb, which is approximately equivalent to 0.1 mg/m3. The design approach involved assessing all aspects of the LII 200 instrument, including: (1) laser and beam generation optics; (2) sampling cell; (3) receiver collection optics; (4) receiver filters and dichroics; (5) photodetectors; and (6) signal detection and digitization electronics. The Phase II results showed that the LII 200 optical design can be modified to provide a two to three order of magnitude increase in measurement sensitivity.
Extensive theoretical modeling, simulations, and experiments clearly demonstrated the feasibility of using a combined LII 200 and elastic light scattering approach for measuring the soot aggregate size and number density, in addition to the soot volume fraction and primary particle size.
The extensive research and development efforts undertaken in Phase II of the project clearly demonstrate the capabilities of the LII 200 technique for engine exhaust PM measurement. It has been demonstrated that an enhanced LII 200 system will be capable of real-time PM measurements over any engine transient operation. It also will have orders of magnitude more sensitivity than the gravimetric technique. The wide dynamic range and lower detection limit will make the enhanced LII 200 a potentially preferred instrument for PM measurements. Artium Technologies has sold the LII 200 to customers in the United States, Canada, and Japan.