2000 Progress Report: Multiplexed Diode-Laser Absorption Sensors for Real-Time Measurements and Control of Combustion SystemsEPA Grant Number: R827123
Title: Multiplexed Diode-Laser Absorption Sensors for Real-Time Measurements and Control of Combustion Systems
Investigators: Hanson, Ronald K. , Jeffries, J. B.
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, 1999 through September 30, 2000
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
Objective:The goal of this research is to demonstrate novel optical sensors based on emerging semiconductor diode laser technology. These new lasers coupled with communication industry developed fiberoptic components enable simple and inexpensive devices for measurements of important combustion species. These all-optical sensors will be compact and reliable, and will allow fast species-specific and sensitive measurements of the target species: CO, a toxic, regulated combustion pollutant; CO2, a major-species combustion product and greenhouse gas; NO and NO2, the important nitrogen-oxide pollutants; NH3 an important combustion effluent from thermal de-NOx and from fuel-bound nitrogen; and H2O, a major-species combustion product. The sensor strategy developed in this program is based on absorption spectroscopy techniques and incorporates new developments in room-temperature continuous-wave semiconductor diode lasers. The range of available diode laser wavelengths has recently been extended into the infrared spectral region near 2.0 and 2.3 microns, thereby enabling sensitive absorption measurements using the strong, first-overtone vibrational bands of CO and NO and strong combination bands of NH3, CO2 and H2O. Similar extensions of diode laser wavelengths into the blue and near-ultraviolet region of the spectrum will enable measurements of NO2 and, with non-linear wavelength conversion, NO. These new lasers operate without cryogenic cooling, and thus promise portable and rugged sensors. The diode-laser absorption sensors will also 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 temperatures and pressures that are relevant to combustion flows.
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, NH3, CO2, and H2O. The sensors employ newly available room temperature, distributed feedback tunable diode lasers that operate near near 2.3 microns for CO measurements, 2.0-microns for NH3 and CO2 measurements, and near 1.3-1.4 and 1.7 microns for H2O measurements. The laser wavelength is tuned across the absorption feature for simultaneous, non-intrusive, multi-parameter direct absorption measurements in the combustion and exhaust regions of laboratory combustion facilities. 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). 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 on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 21 publications||7 publications in selected types||All 5 journal articles|
||Wang J, Maiorov M, Jeffries JB, Garbuzov DZ, Connolly JC, Hanson RK. A potential remote sensor of CO in vehicle exhausts using 2.3 μm diode lasers. Measurement Science & Technology 2000;11(11):1576-1584.||
||Webber ME, Baer DS, Hanson RK. Ammonia monitoring near 1.5 μm with diode-laser absorption sensors. Applied Optics 2001;40(12):2031-2042.||