1999 Progress Report: Multiplexed Diode-Laser Absorption Sensors for Real-Time Measurements and Control of Combustion Systems

EPA Grant Number: R827123
Title: Multiplexed Diode-Laser Absorption Sensors for Real-Time Measurements and Control of Combustion Systems
Investigators: Hanson, Ronald K. , Baer, D. S.
Current Investigators: Hanson, Ronald K. , Baer, D. S. , Jeffries, J. B.
Institution: Stanford University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2002)
Project Period Covered by this Report: October 1, 1998 through September 30, 1999
Project Amount: $344,605
RFA: Exploratory Research - Environmental Engineering (1998) RFA Text |  Recipients Lists
Research Category: Sustainability , Land and Waste Management , Engineering and Environmental Chemistry


This research is aimed at establishing novel optical sensors based on semiconductor diode lasers, fiber-optic components, and absorption spectroscopy techniques for measurements of gas temperature and of CO, CO2, NO, NO2, and H2O concentrations in combustion systems for incineration, propulsion, and energy generation applications. The advanced sensors will incorporate new developments in room-temperature continuous-wave semiconductor diode lasers that extend the range of laser wavelengths into the visible and infrared spectral region (near 2.0 and 2.3 microns), without cryogenic cooling, for sensitive absorption measurements of strong, first-overtone vibrational bands, respectively. These all-optical sensors will be compact, reliable, and enable fast, sensitive measurements of the target species: CO, a combustion pollutant; CO2, a major-species combustion product and greenhouse gas; NO and NO2, the important nitrogen oxides pollutants; and H2O, a major-species combustion product. The diode-laser absorption sensors also will be used to accurately measure (some for the first time) important spectroscopic parameters of the target species at the probed wavelengths over a range of relevant temperatures and pressures to combustion flows. The sensor systems will be applied for nonintrusive, line-of-sight measurements in the combustion region (i.e., in situ) and for fast extractive-sampling measurements in the exhaust region using a multipass cell (36-meter fold optical path) for increased sensitivity, if necessary.

Progress Summary:

Diode-laser absorption sensors have been developed for fast, sensitive, in situ measurements of gas temperature and the concentrations of the target species CO, CO2, and H2O. The sensors employ newly available room temperature, distributed feedback tunable diode lasers that operate near 2.0 microns for CO2 measurements, near 2.3 microns for CO measurements, and near 1.3-1.4 microns for H2O measurements. The sensors were applied for simultaneous, nonintrusive, multiparameter measurements in the combustion and exhaust regions of laboratory combustion facilities (e.g., flat-flame burners). For CO measurements in the exhaust duct, a detection limit of 1.5 ppm-m was achieved by direct absorption spectroscopy with a 50-kHz detection bandwidth and a 50-sweep average (0.1-s total measurement time). With wavelength-modulation spectroscopy techniques, a sensitivity of 0.1 ppm in a 1-m path was achieved with a 500-Hz detection bandwidth and a 20-sweep average (0.4 seconds total measurement time). The measurements in the combustion zone agreed with theoretical equilibrium values to within the experimental uncertainty of about 5 percent. In addition, the CO sensors were incorporated successfully into a system for simultaneous measurements of CO, CO2, and H2O in a laboratory combustion facility. These preliminary results suggest that diode laser absorption techniques may be applied for in situ combustion measurements for in-field continuous emission monitoring and combustion control, detailed studies of engine combustion such as dynamic exhaust gas analysis with single-cycle time resolution, and for development and validation of advanced combustion models.

Future Activities:

Future plans involve extending the capabilities of the sensors for measurements of other combustion species and incorporating the sensors into closed-loop feedback systems for real-time combustion control and emissions compliance.

Journal Articles:

No journal articles submitted with this report: View all 21 publications for this project

Supplemental Keywords:

remote sensing, temperature, waste reduction, pollution prevention, pollution control, atmosphere, combustion, environmental engineering, toxics, pollutants, air pollution., RFA, Scientific Discipline, Air, Waste, Environmental Chemistry, Environmental Monitoring, Incineration/Combustion, Engineering, Chemistry, & Physics, Environmental Engineering, optical sensors, combustion generated radicals, emissions measurement, air pollution, emission controls, optical sensor, process control, carbon dioxide, fiber laser, combustion, incineration, real time monitoring, emissions contol engineering, laser absorption sensors, combustion contaminants

Relevant Websites:


Progress and Final Reports:

Original Abstract
  • 2000 Progress Report
  • 2001 Progress Report
  • Final Report