scholarly journals Non-adiabatic modulation of premixed-flame thermoacoustic frequencies in slender tubes

2022 ◽  
Vol 933 ◽  
Author(s):  
Enrique Flores-Montoya ◽  
Victor Muntean ◽  
Mario Sánchez-Sanz ◽  
Daniel Martínez-Ruiz

This paper presents an experimental study of the influence of heat losses on the onset of thermoacoustic instabilities in methane–air premixed flames propagating in a horizontal tube of diameter, $D = 10$ mm. Flames are ignited at the open end of the tube and propagate towards the closed end undergoing strong oscillations of different features owing to the interaction with acoustic waves. The frequency of oscillation and its axial location are controlled through the tube length $L$ and the intensity of heat losses. These parameters are respectively modified in the experiments by a moveable piston and a circulating thermal bath of water prescribing temperature conditions. Main experimental observations show that classical one-dimensional predictions of the oscillation frequency do not accurately describe the phenomena under non-adiabatic real scenarios. In addition to the experimental measurements, a quasi-one-dimensional analysis of the burnt gases is provided, which introduces the effect of heat losses at the wall of the tube on the interplay between the acoustic field and the reaction sheet. As a result, this analysis provides an improved description of the interaction and accurately predicts the excited flame-oscillation harmonics through the eigenvalues of the non-adiabatic acoustics model. Unlike the original one-dimensional analysis, the comparison between the flame oscillation frequency provided by the non-adiabatic extended theory and the frequencies measured in our experiments is in excellent agreement in the whole range of temperatures considered. This confirms the importance of heat losses in the modulation of the instabilities and the transition between different flame oscillation regimes.

2019 ◽  
Vol 100 (4) ◽  
Author(s):  
A. V. Yulin ◽  
V. K. Kozin ◽  
A. V. Nalitov ◽  
I. A. Shelykh

2015 ◽  
Vol 117 ◽  
pp. 130-141 ◽  
Author(s):  
Ya-jun Wang ◽  
Jiang Li ◽  
Fei Qin ◽  
Guo-qiang He ◽  
Lei Shi

2002 ◽  
Vol 48 (3) ◽  
pp. 347-352 ◽  
Author(s):  
M. A. Mironov ◽  
V. V. Pislyakov

1984 ◽  
Vol 21 (4) ◽  
pp. 415-416
Author(s):  
Meziane Harhad ◽  
Robert W. Courter

2007 ◽  
Vol 51 (2T) ◽  
pp. 313-315
Author(s):  
K. Takahashi ◽  
A. Fukuyama ◽  
T. Kaneko ◽  
R. Hatakeyama

1968 ◽  
Vol 90 (4) ◽  
pp. 547-552 ◽  
Author(s):  
E. K. Levy

A one-dimensional analysis of a compressible vapor flowing within the evaporator section of a heat pipe is presented. Comparisons between the theoretical results and existing heat pipe data show that the presence of gasdynamic choking can limit the heat transfer capacity of a heat pipe operating at sufficiently low vapor pressures.


2013 ◽  
Vol 33 (2) ◽  
pp. 249-257 ◽  
Author(s):  
Alberto Colombo ◽  
Lívia A. Alvarenga ◽  
Myriane S. Scalco ◽  
Randal C. Ribeiro ◽  
Giselle F. Abreu

The increasing demand for water resources accentuates the need to reduce water waste through a more appropriate irrigation management. In the particular case of irrigated coffee planting, which in recent years presented growth with the predominance of drip irrigation, the improvement of drip irrigation management techniques is a necessity. The proper management of drip irrigation depends on the knowledge of the spatial pattern of soil moisture distribution inside the wetted strip formed under the irrigation lines. In this study, grids of 24 tensiometers were used to determine the water storage within the wetted strip formed under drippers, with a 3.78 L h-1 discharge, evenly spaced by 0.4 m, subjected to two different management criteria (fixed irrigation interval and 60 kPa tension). Estimates of storage based on a one-dimensional analysis, that only considers depth variations, were compared with two-dimensional estimates. The results indicate that for high-frequency irrigation the one-dimensional analysis is not appropriate. However, under less frequent irrigation, the two-dimensional analysis is dispensable, being the one-dimensional sufficient for calculating the water volume stored in the wetted strip.


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