Study of Thermo-Diffusive Effects on Iso-Octane/Air Flames at Fixed Turbulence Karlovitz Number

Hayakawa, Akihiro; Takeo, Tomohiro; Miki, Yukito; Nagano, Yukihide; Kitagawa, Toshiaki

doi:10.1115/ajtec2011-44221

Cited by 3 publications

(6 citation statements)

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“…Although these values are important for laminar flame characteristics, such as flame instability [21], turbulent flame characteristics are also affected by the Markstein length or the Markstein number. Hayakawa et al [18] investigated the turbulent burning velocity at fixed turbulence Karlovitz numbers and showed that the ratio of turbulent burning velocity to unstretched laminar burning velocity increases with a decrease in Markstein number. Kobayashi et al [22] proposed that the Markstein length affects the flame surface density of the turbulent flame front via a change in the passivity of the flame front.…”

Section: Introductionmentioning

confidence: 98%

“…Kitagawa and Hayakawa et al [17,18] investigated spherically propagating laminar and turbulent flames in a large constant volume combustion chamber for hydrogen and iso-octane up to initial mixture pressure of 0.5 MPa. Tse et al [19] investigated flame propagation up to 60 atm using two concentric cylindrical vessels.…”

Section: Introductionmentioning

confidence: 99%

“…Spherically propagating premixed flames in a constant volume combustion chamber have been widely investigated in order to clarify the fundamental characteristics of premixed flames [17][18][19][20]. Kitagawa and Hayakawa et al [17,18] investigated spherically propagating laminar and turbulent flames in a large constant volume combustion chamber for hydrogen and iso-octane up to initial mixture pressure of 0.5 MPa.…”

Section: Introductionmentioning

confidence: 99%

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Laminar burning velocity and Markstein length of ammonia/air premixed flames at various pressures

Hayakawa

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Mimoto

et al. 2015

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h i g h l i g h t sLaminar burning velocities of ammonia/air flames at high pressures are evaluated. Maximum value of laminar burning velocity of ammonia/air flame is about 7 cm/s. Laminar burning velocity decreases with the increase in the pressure. Markstein length increases with the increase in equivalence ratio. Markstein lengths at high pressure are lower than those at 0.1 MPa. a b s t r a c tAmmonia is expected to be useful not only as a hydrogen-energy carrier but also as a carbon-free fuel. In order to design an ammonia fueled combustor, fundamental flame characteristics of ammonia must be understood. However, knowledge of the characteristics of ammonia/air flames, especially at the high pressures, has been insufficient. In this study, the unstretched laminar burning velocity and the Markstein length of ammonia/air premixed flames at various pressures up to 0.5 MPa were experimentally clarified for the first time. Spherically propagating premixed flames, which propagate in a constant volume combustion chamber, were observed using high-speed schlieren photography. Results indicate that the maximum value of unstretched laminar burning velocities is less than 7 cm/s within the examined conditions and is lower than those of hydrocarbon flames. The unstretched laminar burning velocity decreases with the increase in the initial mixture pressure, tendency being the same as that of hydrocarbon flames. The burned gas Markstein length increases with the increase in the equivalence ratio, the tendency being the same as that of hydrogen/air flames and methane/air flames. The burned gas Markstein lengths at 0.1 MPa are higher than those at 0.3 MPa and 0.5 MPa. However, the values of burned gas Markstein length at 0.3 MPa and 0.5 MPa are almost the same. In addition, numerical simulations using CHEMKIN-PRO with five detailed reaction mechanisms which are presently applicable for the ammonia/air combustion were also conducted. However, qualitative predictions of unstretched laminar burning velocity using those reaction mechanisms are inaccurate. Thus, further improvements of reaction mechanisms are essential for application of ammonia/air premixed flames.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Laminar burning velocity and Markstein length of ammonia/air premixed flames at various pressures

Hayakawa

Goto

Mimoto

et al. 2015

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319

171

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“…(8) (19) , The gradient of velocity fluctuation components are required to evaluate the longitudinal Taylor microscale from Eq. (8). In order to ensure the accuracy of the gradient of velocity fluctuation component, the minimum spatial resolution must be set less than three or four times of Kolmogorov length scale (20) .…”

Section: Longitudinal Taylor Microscale and Kolmogorov Length Scalementioning

confidence: 99%

“…(12) were close to the values from its definition, Eq. (8). In this study, the PIV measurements were only conducted at the conditions shown in Table 1 for air at 298 K. The properties of iso-octane/air mixture, such as kinematic viscosity, which was used in this study are different from air.…”

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confidence: 99%

Analysis of Turbulent Burning Velocity of Spherically Propagating Premixed Flame with Effective Turbulence Intensity

Hayakawa

Miki

Nagano

et al. 2012

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Burning velocity of spherically propagating turbulent flames kept increasing with flame propagation. On the other hand, turbulent burning velocity obtained from burner stabilized flame is constant for a given turbulence intensity. This difference of turbulent burning velocity characteristic was discussed by Abdel-Gayed and Bradley et al. For spherically propagating flames, not all turbulent eddies contribute to the turbulence that affect the turbulent flame. Small flames may be wrinkled only by small scale turbulent eddies. As the flame propagates, it becomes progressively wrinkled by the larger eddies. The turbulence which contributes to turbulent flame may increase with the increase in flame radius. This increase in turbulence may cause the increase in turbulent burning velocity. The effective turbulence intensity was proposed by Abdel-Gayed and Bradley et al. as the turbulence intensity which contributes effectively to turbulent flame. In this study, the turbulence characteristics which are necessary for obtaining the effective turbulence intensity were evaluated by Particle Image Velocimetry (PIV) measurement. Then turbulent burning velocity of iso-octane/air flame was investigated with effective turbulence intensity. The turbulent burning velocity increased with the increase in effective turbulence intensity. The increase in turbulent burning velocity may be caused by the increase in flame front area with increase in the effective turbulence intensity.

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Study of Thermo-Diffusive Effects on Iso-Octane/Air Flames at Fixed Turbulence Karlovitz Number

Cited by 3 publications

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Laminar burning velocity and Markstein length of ammonia/air premixed flames at various pressures

Laminar burning velocity and Markstein length of ammonia/air premixed flames at various pressures

Analysis of Turbulent Burning Velocity of Spherically Propagating Premixed Flame with Effective Turbulence Intensity

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