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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

# Response of Soot Temperature to Unsteady Inlet Airflow Under Modulated Condition and Naturally Occurring Combustion Dynamics

[+] Author and Article Information

Combustion Research Laboratory,
School of Aerospace Systems,
University of Cincinnati,
745 Baldwin Hall,
Cincinnati, OH 45221-0070

Arda Cakmakci

Combustion Research Laboratory,
School of Aerospace Systems,
University of Cincinnati,
745 Baldwin Hall,
Cincinnati, OH 45221-0070
e-mail: cakmakaa@mail.uc.edu

Jong Guen Lee

Combustion Research Laboratory,
School of Aerospace Systems,
University of Cincinnati,
Engineering Research Center, Room 484,
Cincinnati, OH 45221-0070
e-mail: jongguen.lee@uc.edu

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 10, 2014; final manuscript received August 25, 2014; published online November 11, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(4), 041507 (Apr 01, 2015) (5 pages) Paper No: GTP-14-1368; doi: 10.1115/1.4028673 History: Received July 10, 2014; Revised August 25, 2014; Online November 11, 2014

## Abstract

The response of soot temperature to unsteady inlet airflow is characterized using pyrometry. The unsteady inlet airflow is achieved by either modulating inlet air or naturally occurring unstable flame, running on a jet fuel at fuel-rich conditions. The inlet air is modulated by a siren device running at frequencies between 150 and 250 Hz and up to 60% of modulation level ($u'$/um) is achieved. Also, the combustor can be run naturally unstable at the same inlet operating condition by changing the combustor length. For pyrometry, the emission from whole flame at 660 nm, 730 nm, and 800 nm is recorded and the three-color pyrometry is used to measure soot temperature. The effect of nonisothermal distribution of soot in flame on the measured temperature is also considered. The level of overall temperature fluctuation under inlet flow modulation (Trms/Tmean) is about an order of magnitude lower than that of flame emission fluctuation (Irms/Imean). Under naturally occurring instability, the measured soot temperature is in phase with the pressure measured in the combustor, indicating that the measured soot temperature can be used as a quantity related to combustion dynamics for fuel-rich sooty flames.

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## Figures

Fig. 1

Flame emission spectrum from fuel rich flame (φ = 4) around (a) OH*- and (b) CH*-band

Fig. 2

Cross-sectional view of test setup

Fig. 3

Optical arrangements for three-color pyrometer

Fig. 4

Typical histogram of temperature

Fig. 5

PDF (probability density function) of soot temperature from nonisothermal flames for case 1 (Tm = 1850 K), case 2 (Tm = 2100 K), and case 3 (Tm = 2400 K)

Fig. 6

Total emission spectrum for (a) case 1 (Tm = 1850 K), (b) case 2 (Tm = 2100 K), and (c) case 3 (Tm = 2400 K)

Fig. 7

(a) Emission intensity fluctuation versus inlet velocity fluctuation and (b) temperature fluctuation versus emission intensity fluctuation

Fig. 8

Fast Fourier transformation result of temperature (T800/660) oscillation for Vrms/Vmean = 22%

Fig. 9

Time traces of combustor pressure and emission during naturally unstable flame

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