A semi-premixed channel structure in the flame front of a premixed combustor

Abstract

The invention discloses a flame front head half pre-mixing channel structure of a pre-mixing combustion chamber. A convergent channel is formed in the upstream portion of a half pre-mixing channel, the outer ring convergent and inner ring expanding manner is adopted, the structural form can carry out acceleration on an incoming flow, and the tempering danger of the combustion chamber is reduced; adownstream outer ring expanding structure is arranged on the downstream portion of the half pre-mixing channel, it can be ensured that the flame face is expanded outwards to reserve the enough spacefor the backflow area, a center body is arranged to be in the axial expanding manner to reduce the tempering risk, the inwards-concave curve shape is adopted in the expanded center body end to ensurethat the backflow area developing to the downstream area cannot be generated, and only a backflow area is formed between the flame and the oval.

Description

technical field [0001] The invention belongs to the technical field of combustion chambers of gas turbines, and relates to a flame front semi-premix channel structure, in particular to a flame front semi-premix channel structure of a premix combustion chamber. Background technique [0002] In the combustor design of heavy-duty low-pollution gas turbines, lean oil (mainly natural gas fuel) semi-premixed combustion is often used to reduce the flame temperature and reduce the emission and pollution of NOx harmful gases. In the high-pressure test of this kind of combustion chamber, there will be thermoacoustic oscillation caused by flame instability, lean flameout and flashback caused by fuel diversity (such as hydrogen, ethane, propane and other active fuels). The existing technology mainly adopts the convergent outer ring in the shape of the convergent channel to accelerate the gas in the semi-premixed channel so as to reduce the risk of flashback (such as figure 1 , 2 shown...

AI Technical Summary

Problems solved by technology

[0003] Although figure 1 , 2 , The design shape of the existing semi-premixed channel shown in 3, although its starting point is all in order to reduce the risk of tempering, but there are defects and deficiencies in the three structural designs: for figure 1 In terms of the convergent semi-premixed channel shown, as Figure 4 As shown, the convergent shape of the outer ring does not completely prevent the tempering phenomenon, and there is still a high-temperature zone near the tip of the central body. Although the high-temperature zone can generally be eliminated by means of cold air blowing, the problem with this shape is that, The speed in the mixing channel is high, and there is no expansion angle in the mixing section close to the combustion chamber, resulting in a small opening angle of the flame downstream, which limits the size of the recirculation zone. The recirculation zone is axially narrow and long, easy to go up and down Movement, causing combustion instability, and eventually lead to flameout, so the axial inlet speed is generally kept low in general use, and this limits the power load of the combustion chamber

for figure 2 In terms of the convergent semi-premixed channel shown, as Figure 5 As shown, in order to reduce the total pressure loss, the expansion angle increased at the end of the mixing section, although the flame spreads out leaving enough space for the central recirculation zone to develop, but it also brings a great risk of tempering, mainly in the case of If the expansion angle is set too small, the recirculation area will be unstable and the fire cannot be stabilized. If the expansion angle is set too large, the local speed will be low and the risk of backfire will be high. In addition, the center body will not produce a recirculation area to steady flame

for image 3 In terms of the convergent semi-premixed channel shown, as Image 6 As shown, increasing the radius of the inner ring will increase a blunt body-induced recirculation zone downstream, however, since the axial position of the central body is close to the upstream, the flame generated downstream of the combustion chamber will easily "cut off" the two recirculation zones (due to the flame Acceleration), while the recirculation zone near the upstream due to the central body will move along the circumference, this driving force is due to the tangential velocity generated by the swirl mixing used in the upstream; the downstream flame surface is due to the non-stop central body The development of the recirculation zone to the downstream causes the area of ​​the flame surface to change, resulting in a thermoacoustic oscillation source. Another point is that the local high temperature on the flame surface will generate hot spots, and the high temperature causes the increase of NOx

Images