液氧/甲烷火焰和燃烧不稳定性试验

Experimental investigation on combustion instability of liquid oxygen and methane flame

为了解液氧/甲烷火焰在外界扰动作用下的表现,增进对燃烧不稳定性的理解,分别对两种喷剪切同轴式喷嘴结构进行了试验,试验采用单喷嘴矩形模型燃烧室,液氧以液态从中心喷嘴喷注,甲烷以气态从同轴的环形腔喷注。试验中,压力调节装置上的齿轮间断性地堵住和打开安装在燃烧室底部和主喷管旁边的辅助喷管出口,分别向燃烧室输入高频扰动。采用高速照相机记录火焰的OH辐射量,并采用阴影和纹影技术记录液氧的喷雾过程。试验成功激发起了燃烧室一阶横向和一阶纵向振型,在高频扰动作用下,还产生了两次强低频振荡。讨论了分离火焰的特征及其液氧射流在外界扰动作用下的表现和影响参数。

Experimental results of a test campaign on the interaction of a cryogenic LOX/CH4 spray flame with an acoustic excitation are given. Liquid oxygen and gaseous methane are injected with a shear coaxial injector. The flame was visualized by detecting the OH emission with a frame rate up to 27 kHz. Simultaneously shadowgraph images were also recorded to visualize the flow field. The flame behavior under different chamber pressure and different mixture ratio is compared. A pressure modulator device was used to excite acoustic pressure oscillations in the combustion chamber. The first transversal and the first longitudinal combustion instability could be excited during hot fire tests. Two strong low frequency instabilities were found under high frequency external disturbance. A lifted flame has been observed under the experimental conditions and the characteristic of the lift-off distance is discussed.