大型锻造加热炉蓄热式燃烧系统改造模拟

Simulation of regenerative combustion system reformation of large forging heating furnace

利用CFD软件模拟了一个大型加热炉的新型设计方案并对其合理性、可行性进行了分析。该方案将12个直焰蓄热式燃烧器布置在炉顶两侧、燃烧器出口向下安装;并相应设计45°炉衬转角使炉气作90°转向时有导流作用。采用标准k-ε模型、离散坐标模型(DO模型),系统地研究了该方案升温、保温初期、保温末期,相应燃烧器不同能量供应方式对有效加热区内速度场、温度场的影响。通过模拟发现:火焰出口高速射流区域是温度最高区域,设计中需要留有充分空间使其在有效加热区外,在此区域外的炉膛上部区域,速度场稳定且流速低,仅受高温辐射传热影响,低温烟气回流影响较小,温度相对均匀;模拟中发现因直焰燃烧器的高速燃气动能充沛,气流直冲而下,顺着特制的45°炉衬斜面90°转向后继续顺着炉底行进,约70%的炉气可以穿过垫铁和工件使之均匀加热,并达到对侧炉墙,在炉内形成均匀流场。模拟显示,在30 s的一个供热周期内,燃烧器由全能量供应30 s变为全能量供应10 s、或全能量供应5 s,铸锭表面温度差由90℃减小到15℃以内,完全满足工艺要求。

CFD software was used to simulate a design scheme of a large pallet heating furnace,and the rationality and feasibility of the scheme was analyzed. In the scheme,12 direct flame regenerative burners installed on the top of both sides,each side 6,downward; a 45°slope lining at 90° bend was designed to make a guide flow to the high speed air flow. Effects of different energy supply modes for corresponding burners on the velocity field and the temperature difference of the ingot surface during the different heating processes such as temperature rising period,early and end stages of holding time are studied by using the standard k-ε model and the discrete coordinate model（ DO model）. The simulation results show that high velocity jet zone of flame outlet is the highest temperature area,so the design needs to set aside enough space to avoid the effective heating zone. For the rest areas of the upper part of the furnace,the velocity field of the flow rate is low and stable,low speed flame reflux has little influence on the temperature,the temperature is more affected by high temperature heat radiation,which therefore results in a relatively uniform temperature area. The simulation found out that due to the enough kinetic energy of high speed burning gas,the gas stream flows downward to furnace bottom along specially made 45° slope lining at 90° bend,about 70%burning gas can go through pallets to homogenously heat workpieces. It is simulated that during 30 s heating cycle,the time for full energy supply reduced from 30 s to 10 s or 5 s,the temperature difference of the ingot surface is reduced from 90 ℃ to 15 ℃.