Medium Resolution Transmission Measurements of CO2 and H2O at High Temperature and a Multiscale Malkmus Model for Treatment of Inhomogeneous Gas Paths
Open Access
- Author:
- Bharadwaj, Sudarshan Padmanaban
- Graduate Program:
- Mechanical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 21, 2005
- Committee Members:
- Michael F Modest, Committee Chair/Co-Chair
Anil Kamalakant Kulkarni, Committee Member
Domenic Adam Santavicca, Committee Member
Eugene Edmund Clothiaux, Committee Member - Keywords:
- Multiscale Malkmus model
Malkmus model
Combustion gases
Narrow-band transmissivity
Inhomogeneous gas paths - Abstract:
- Radiative heat transfer is often the dominant mode of heat transfer in fires and in commercial combustion systems. Radiative heat fluxes with large magnitudes can have profound effects on combustion performance and on the environment. Despite their importance, the lack of knowledge of the necessary radiative properties makes it impossible today to accurately predict such radiative fluxes. Also, there are no models today to calculate radiative fluxes accurately at an acceptable computational cost for general participating media with spectrally varying properties. Medium resolution high temperature transmission measurements have been made for CO$_2$ and H$_2$O using a drop tube mechanism, which, owing to the short dwell time of the drop tube within the furnace, guarantees a truly isothermal high-temperature gas column. In the current work, an existing transmissometer apparatus was significantly redesigned in order to obtain better signal-to-noise ratios, and the modified apparatus was used to measure the transmissivity of CO$_2$/H$_2$O at temperatures up to 1550~K. The new measurements will overcome the limitations of older data obtained by earlier researchers, which have an average uncertainty of around $pm$30\%, as well as those of data obtained with the previous transmissometer setup, whose uncertainty was around $pm$20\% for high temperatures. Data were collected with an FTIR-spectrometer. The measured data were compared with two line-by-line databases (HITEMP and CDSD1000) and two narrow-band databases (Radcal and SNB). They were also used to obtain least-squares fitted Malkmus band model parameters at different temperatures. Narrow-band $k$-distribution functions were obtained from these parameters, based on the Malkmus narrow-band model. A new, more accurate method of deriving the transmissivity of an inhomogeneous path from the experimental data for homogeneous paths at various temperatures was also developed, for use with the narrow-band $k$-distribution functions.