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: 68D02010
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: April 1, 2002 through September 1, 2002
Project Amount: $69,992
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , SBIR - Monitoring , Small Business Innovation Research (SBIR)
The overall purpose of the Phase I research project was to investigate and demonstrate the feasibility of a nonintrusive instrument for real-time particulate concentration and primary particle size measurement in diesel and gasoline engine exhaust. The technology is based on the principle of laser-induced incandescence (LII). Specific efforts included the development of theoretical models, identification of measurement approaches, design and development of a prototype LII system including hardware and software, and testing of the prototype system under different applications to demonstrate the feasibility of the measurement technique.
Light scattering and heat transfer models were developed to accurately describe the process of LII from soot particulates. These theoretical models subsequently were used to develop optimal methods for measuring the soot volume concentration and primary particle size. The methodology incorporates a pulsed laser that heats the elemental carbon in the soot exhaust particulates to incandescence. Two photodetectors measure the radiation, at different wavelengths, from the soot particles. The radiation signature, related to the heating and cooling rate of the particulates, is directly related to the soot particulate volume concentration in parts per trillion. This can be related to mass using the particle density. The rate of decay of the LII signal is used to infer the soot primary particle size (a soot aggregate is composed of nano-sized spherical primary particles).
A prototype LII system, including the hardware and software, was developed. A key innovation is a low-fluence technology that incandescences the carbon particles and avoids vaporization. The low-fluence approach yields consistent, reproducible measurements. The prototype also includes National Institute of Standards and Technology traceable calibration, two-color pyrometry, self-calibration, and relay imaging of the apertured beam. These features differentiate Artium Technologies, Inc.'s instrument from competing LII systems.
The prototype LII system was tested under different applications, namely diesel engine exhaust, gasoline engine exhaust, and carbon black production. The results were compared with data from conventional instruments such as the gravimetric method, the smoke meter, and the electric low-pressure cascade impactor. These tests and comparisons clearly demonstrated the ability of the LII instrument to accurately measure the soot volume concentration and primary particle size. Excellent measurement range and sensitivity also were demonstrated. In addition, the ability of the LII instrument to make transient measurements was clearly demonstrated.
The primary application for the LII system is for monitoring soot particulate emissions from vehicles (diesel and gasoline). Artium Technologies, Inc., believes that the LII instrument could be used for enforcing U.S. Environmental Protection Agency regulations on particulate emissions. A version of the instrument also can be used for research and development purposes. Specifically, this instrument will help engine manufacturers develop low-emission engines. It also will assist in the development of products by emissions control equipment manufacturers. There is a need for real-time measurement of the mass of the elemental carbon in the raw diesel exhaust. This is important for engine design to reduce particulate emissions. This also can be useful in regulatory compliance, as an alternative to gravimetric procedures that are time consuming, require dilution and filtration, and can have sampling errors. The LII system can be coupled with technology that is being simultaneously developed by Sandia National Laboratory to measure the soluble organic fraction in exhaust streams to provide more complete information on the organic components of the exhaust. The National Research Council of Canada is continuing to develop enhancements that will allow the measurement of the size and shape of the soot aggregates and their particle size distribution. The independent market analysis conducted by Foresight Science & Technology has determined that Artium Technology, Inc.'s LII technology can be successfully commercialized and introduced into the market.