ACERC
Abstracts - 1996 |
ACERC
Abstracts - 1996 |
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Thrust Area 6: Model Evaluation Data and Process Strategies |
Tree, D.R.; Wiczynski, P.D.
and Yonushonis, T.M.
Society of Automotive Engineers, 960036:103, 1996. (Also presented at
SAE International Congress, Detroit, Michigan, February 22-92, 1996.)
Funded by Cummins Engine Company, US Department of Energy and NASA.
Measurements have been made to determine the effect of piston crown surface properties on combustion. Back-to-back engine tests were conducted to compare surface modified pistons to a production piston. Each modified piston was found to prolong combustion duration. Porous coatings and a non-porous, roughened piston were observed to increase fuel consumption. Increase in fuel consumption was determined to be the result of increased heat release duration. The data show surface roughness alone affects the duration of heat release. The shift in magnitude of the centroid of heat release was similar to the shift observed in insulated engine experiments.
Tree, D.R.; Oren, D.C.;
Thomas, M.Y. and Wiczynski, P.D.
Society of Automotive Engineers, 960317:131, 1996. Funded by Cummins
Engine Company, US Department of Energy and NASA.
Data have been gathered to compare the performance of steel crown pistons coated with yttria stabilized zirconia or mullite to an uncoated piston. The effect of coated pistons on in-cylinder heat transfer was determined from curves of ISFC versus centroid of heat release. Error analysis of the measurements showed uncertainty of ± 3% in ISFC and ± 2 crank angle degrees in the centroid of heat release could be expected for the data. Particulate emissions increased at advanced injection timings with the mullite-coated piston while the zirconia-coated piston showed an increase in particulate and NOx at advanced timings.
Haslam, J.K. and Hedman,
P.O.
Proceedings at the Fall Meeting of the Western States Section/Combustion
Institute, The University of Southern California, Los Angeles, California,
October 28-29, 1996. Funded by ACERC and Morgantown Energy Technology Center
(ATS).
New laser dyes allow improvement in existing coherent ant-Strokes Raman spectroscopy (CARS) instruments. In the past, single Strokes, beam CARS instruments have been used to probe one species for temperature and concentration (e.g. N2). In order to probe multiple species simultaneously (CO, CO2, O2, N2), two Strokes beams are often used in what is known as a dual-Strokes CARS instrument. However. The dual-Strokes beam instruments are relatively inefficient, difficult to align and optics intensive. With new Pyromethene dyes, a single Strokes beam can be used to probe the same species as the dual Strokes with enhanced performance. In this experiment, two new CARS system dyes were compared and evaluated for enhanced multi-species detection. The improved CARS instrument uses a mixture of Pyromethene 597 and Pyromethene 650 for a single Strokes laser beam. These two mixed dyes have sufficient spectral band width and improved intensity to replace the traditional Rhodamine 575/601 dye and Rhodamine 640 dyes of an earlier dual-Strokes CARS instrument. The improved Pyromethene single Strokes CARS system has been used to obtain CARS spectra (CO, CO2, O2, N2) that allowed CARS temperature and species concentration measurements in a swirling, turbulent, premixed natural gas/air burner to be obtained.
Dawson, R.W. and Hedman,
P.O.
Proceedings at the Fall Meeting of the Western States Section/ Combustion
Institute, The University of Southern California, Los Angeles, California,
October 28-29, 1996. Funded by ACERC and Morgantown Energy Technology Center
(ATS).
An approach for analyzing instantaneous CO, O2, CO2, and H2O species concentrations using multiplex coherent anti-Strokes Raman spectroscopy (CARS) in premixed combustion systems in introduced and demonstrated. A dual-dye, single broadband Strakes dye laser was used to produce CARS spectral signals from N2, CO, O2, and CO2. A computer code obtained Sandia National Laboratories was used to determine the temperature as well as the value Chinr/Xi where Xi is the specie mole fraction and Chinr is the signal contribution form non-resonant gases. Temperatures as well as the non-resonant signal contribution (Chinr) for each laser shot were obtained from the nitrogen spectra. Initial estimate of Chinr were made by assuming that nitrogen concentrations were known and remained constant throughout premixed combustion. Equilibrium predictions, based upon the instantaneous nitrogen temperature, were used in conjunction with the estimated value of Chinr as initial estimates needed to resolve the instantaneous CO, O2, and CO2 spectra into concentration measurements. This technique reduced the computational demand of determining the best fit between theoretical and experimental spectra.
The H2O mole fraction was determined from an oxygen elemental mass balance and the assumption that any oxygen not accounted for in the measured concentrations of CO, O2, and CO2 was in H2O. The partially reacted natural gas will bee in the form of various hydrocarbon fragments that are difficult to quantify. The hydrogen that is not reacted to water is assumed to be unaccounted for by the measurements and is lumped into a H* mole fraction, and the carbon that is not measured as CO2 or CO is unaccounted for carbon, which is lumped into a C* mole fraction. The magnitude of H* and C* gives an indication of the extent of the combustion reaction and the ratio H* to C* gives an indication of the effective composition of the partially reacted hydrocarbon gases (CXHY). The results show that this technique is effective in determining concentrations of the major combustion species in a premixed gaseous-fueled flame. The paper describes the detail of the technique and presents example results for a swirling, turbulent, premixed natural gas/air flame.
Flores, D.V. and Hedman,
P.O.
Proceedings at the Fall Meeting of the Western States Section/Combustion
Institute, The University of Southern California, Los Angeles, California,
October 28-29, 1996. Funded by ACERC and Morgantown Energy Technology Center
(ATS).
The objective of this study was to obtain temperature and species (CO, CO2, O2, N2 and H2O) concentration measurements using coherent anti-Stokes Raman spectroscopy (CARS) from and atmospheric pressure, swirling, turbulent, premixed natural gas/air flame in a model combustor that simulates the characteristics of a utility gas turbine engine. The Brigham Young University (BYU)/ACERC laboratory-scale, gas-turbine combustor (LSGTC) simulates many of the key combustion characteristics of commercial gas turbines, while providing optical access for the CARS laser beams. In situ data (temperature and species concentrations) have been collected as a function of radial and axial position at several locations over the combustion zone.
This paper demonstrates the applicability of two new developments made at the BYU/ACERC optics laboratory: (1) a new CARS systems that uses a dual dye, single Stokes laser with sufficient spectral band-width to simultaneously excite the Strokes frequencies of N2, CO, O2, CO2 and (2) a newly proposed method that allows the calculation of additional species concentrations from reduced CARS data from local elemental mass balances. The species concentrations calculated include H2O, and unaccounted-for hydrogen (H*) and carbon (C*).
Iso-coutour maps of temperature and species concentrations from instantaneous CARS measurements on premixed natural gas flames are presented. The combustor was operated at a medium swirl number of 0.74 and a fuel equivalence ratio of 0.65. Early results indicate that the measurements of species concentrations are self-consistent. Nevertheless CO measurements are above expected levels based on both kinetic and equilibrium predictions. Investigation on the source of this discrepancy is underway. In addition, estimated concentrations of H2O and unaccounted-for carbon (C*) and hydrogen (H*), deduced from oxygen, carbon, and hydrogen mass balances (from known premixed composition) are presented. Observations on flame behavior from these measurements are made. These data provide considerable insight into the flame behavior as well as a database for model evaluation.
Kinghorn, K.B. and Hedman,
P.O.
Proceedings at the Fall Meeting of the Western States Section/Combustion
Institute, The University of Southern California, Los Angeles, California,
October 28-29, 1996. Funded by ACERC and Morgantown Energy Technology Center
(ATS).
A new burner design that may have application in gas turbine engines was designed and fabricated and preliminary operational characteristics were determined in a laboratory-scale gas turbine combustor. The adjustable burner uses a ring-shaped cylindrical cavity wherein the combustion zone is stabilized by a toroidal body of hot rotating gases. With this design, the toroidal flow of the burner maintained a stable flame over a range of fuel equivalence ratios (Phi = 0.50 to 1.2). Quantitative experiments were conducted to evaluate operation over a range of fuel equivalence ratios (Phi =0.6, 0.7, 0.8, 0.9,1.0, 1.1, and 1.2) and inlet velocities (7.5, 10, 30, 50, 70, 90, and 100 m/sec). The flame appeared to be more stable at lower inlet velocities. The magnitudes of the inlet velocity controls the rotational speed of the toroidal flow, which seems to affect the flame stability.
In order to better understand the mechanisms involved in the toroidal flow stabilization, a two-dimensional slice of the full-scale burner was designed and fabricated. This 2-D section of the full burner allows for optical access and laser diagnostics. The design and testing of both burners is presented and the operational characteristics are discussed. Future research possibilities are also presented.
Dubey, R.K.; Erickson, P.A.
and McQuay, M.Q.
HTD-Vol 328, National Heat Transfer Conference, 6:29, 1996. Funded by
ACERC.
The combustion characteristics of an ethanol spray flame in a Rijke-tube combustor under the influence of an actively controlled acoustic field has been experimentally investigated using the phase-Doppler particle analyzer technique. The actively controlled acoustic field in the combustor had sound pressure levels of 150 dB and a frequency of 69 Hz. Active control was implemented using a modified fast response feedback loop controller, using two speakers, and was used to attenuate as well as enhance the fundamental mode of oscillation in the combustor. Experiments were performed to study the effect of three sound pressure levels (nonoscillating, oscillating with 150 dB, and enhanced oscillating with 160 dB) on temperature distribution, total heat transfer, Sauter-mean diameter of the ethanol droplets, mean and time-resolved droplet velocity and droplet data rate. The results show that the droplet time-resolved azial velocity component has a preferred frequency equal to the frequency of the sinusoidal pressure wave in the combustor. The maximum temperature measured at quarter length of the combustor increased from 1138 K for nonoscillating to 1194 K for enhanced condition. The heat transferred from the combustor wall by the cooling water increased by 36% of the nonoscillating value for the enhanced condition and was directly dependent on the amplitude of the acoustic field. The Sauter-mean diameter of the spray decreased, on average, 6% and 9% for the sound pressure levels of 150 dB and 160 dB, respectively, while the droplet arrival rate at the prove volume remained the same.
Newbold, J.; McQuay, M.Q.
and Webb, B.W.
Proceeding of the Twenty-Ninth Symposium on Automotive Technology and Automation:
967-976, 1996. Funded by ACERC and Ford.
Profiles of velocity, species concentration (O2, CO, CO2), wall radiative heat flux, and temperature are reported in the combustion space of regenerative, side-port, 650-ton/day, gas-fired, flat-glass furnace. A region of fast moving gases exists near the glass, with axial velocity components exceeding 20 m/s, and a large recirculation zone near the crown. Temperatures as high as 2050 K in the flame and as low as 1750 K in the recirculation zone are reported. A region of intense reaction near the glass, with large concentration gradients, and incomplete combustion even in the tail of the flame are observed. Local incident radiant fluxes in the crown were nearly uniform spatially at a level of 700 kW/m². CO2 concentrations were the highest near the batch, where the glass reactions are the most intense.
Mallampalli, H.
Evaluation of CH4/NO Global Mechanisms Used for Modeling Lean Premixed Turbulent
Combustion of Natural Gas, M.S./BYU, August 1996. Advisor: Fletcher
Groberg, C.J.
Comparison of Measured Gas Temperature and Species Concentrations Taken at
the Milliken Furnace to PCGC-3 Predictions, M.S./BYU, December 1996. Advisor:
Cannon
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