Burner lip temperature and stabilization of a non-premixed jet flame

Lifting and Splitting of Nonpremixed Methane/Air Flames Due to Reactant Preheating

“…This moves the flame sheet closer to the shear layer and leads to generalized LE at the breakpoint (split flame). Complementarily, the present study has shown the significance of thermal effects in the occurrence of stable split flames: in addition to effects on temperature-dependant properties (both intrinsic fluid and reactive properties) discussed in §3.1, A c c e p t e d M a n u s c r i p t 24 one major effect of preheating is to increase the lip temperature, thus reducing heat loss from the flame base to the burner (Lamige et al, 2014) and enhancing the attached flame stability close to the burner rim. As a consequence of the high injection velocities then reached, local extinctions increase in number and length at the flame breakpoint, with an obvious impact on the flame lifting process.…”

“…Downstream flame extinction is attributed, by Takeno and Kotani (1975), to increased heat and mass transfer rates at the jet breakpoint, resulting in excess transport rate A c c e p t e d M a n u s c r i p t 23 compared to reaction rate. The rim is also postulated to be heated by the flame itself, and may facilitate eddy formation just downstream of the rim, both of which may play significant stabilizing roles (Takeno and Kotani, 1975;Lamige et al, 2014).…”

“…A c c e p t e d M a n u s c r i p t 18 A striking feature of Figure 9 comes from the noticeable evolution with preheating of the preferred origin for non-burning events. A first observation, regardless of the preheating level, comes from the quasi absence (only two cases at T ox,ref = 600 K) of LE starting between the attachment height H a (z ≈ 1.0 mm at ambient temperature (Lamige et al, 2014)) and z = D i .…”

“…"Lifting" (timeline origin) has been defined in these sequences as the first image presenting the cessation of combustion (indicated by cessation of chemiluminescence) at the attachment height (H a (Lamige et al, 2014), cf. Figure 1) close to the burner rim, i.e.…”

“…Experiments were performed on the same experimental burner utilized previously (Lamige et al, 2010(Lamige et al, , 2013(Lamige et al, , 2014Min et al, 2010). In brief, it consists of a vertical coflow atmospheric burner.…”