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. , 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 Amount: $344,605
RFA: Exploratory Research - Environmental Engineering (1998) RFA Text | Recipients Lists
Research Category: Sustainability , Land and Waste Management , Engineering and Environmental Chemistry
Increasingly stringent environmental regulations and the drive for more efficient and economical combustion systems motivate the development of improved sensors for real-time process control and emissions monitoring. The objective of the proposed research is to establish novel optical sensors based on semiconductor diode lasers, fiber-optic components, and absorption spectroscopy techniques for measurements of gas temperature and the concentrations of CO, CO2, NO, NO2, and H2O at multiple locations in combustion systems for incineration, propulsion, and energy generation applications. The measured values of gas temperature and species concentrations will be incorporated into a closed-loop strategy to demonstrate the utility of diode-laser sensing for on-line adaptive control of the combustion process and emissions monitoring.
The advanced sensors will incorporate new developments in room-temperature semiconductor diode lasers that extend the range of laser wavelengths into the visible and infrared spectral region, without cryogenic cooling, for sensitive absorption measurements of electronic transitions and strong, first-overtone vibrational bands, respectively. Values of species concentrations and gas temperature will be determined in real time from high-resolution absorption measurements recorded at selected wavelengths using a fast, high bit-resolution data acquisition system on board a personal computer. The adaptive control strategy will be based on least-mean-square algorithms for fast time response, stability, and ease of implementation.
These optical sensors will be compact, reliable, and enable fast, sensitive measurements of gas temperature and the target species: CO, a combustion pollutant; CO2, a major-species combustion product and greenhouse gas; NO and NO2, the important nitrogen-oxide pollutants, and H2O, a major-species combustion product. In addition, the sensor system will be compatible with fiber-optic components for easy implementation, wavelength multiplexing, and simultaneous multi-species measurements at multiple locations. The diode-laser sensors will also be used to measure important fundamental 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 non-intrusive, line-of-sight measurements in the combustion region and for fast extractive-sampling measurements in the exhaust region using a multi-pass cell for increased sensitivity. The outputs from the sensors will be incorporated into a closed-loop strategy for real-time adaptive control of the combustion process. Future generations of the sensors may be developed to measure other important species including N2O, NH3, combustion radicals such as CH and C2, and various stable hydrocarbons (e.g., CH4, C2H2, C6H6). The reliability, accuracy, and flexibility of these multiplexed diode-laser sensors make them suitable for measurements of combustion pollutants and efficiency for emissions-monitoring and combustion-control applications and thus will enable improved design and development of large-scale industrial systems.