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研究了液体燃料喷雾蒸发程度对突扩燃烧室热量释放图形及稳定性的影响。保证总的燃料/空气比不变。在几种液/气燃料流量比下,同时喷入液态和气态烃类燃料,可改变燃料的喷雾蒸发程度。蒸发程度的变化可改变燃烧室内平均能量释放图形及瞬时火焰结构,并可改变与燃烧室不稳定性有关的压力脉动的振幅和频率。当液体燃料份额从0增加到50％时,总的压力脉动均方根值降低至50％。当预混气态燃料和空气进行燃烧时,压力脉动的大部分能量保留在45～65Hz的低频带内,此压力脉动包含燃烧室纵向声振波型。随液体燃料的喷射,可以观察到低频部分明显减少,高频部分(250～380Hz)明显增加。通过测量CH辐射强度可知,当预混气态燃料和空气燃烧时,体积能量的释放是沿着整个燃烧室的长度分布的。当喷射液体燃料时,能量释放区域向上游移动并集中在燃烧室的前半部分。在最大平均能量释放区域,液体燃料的加入也造成了热量释放脉动均方根值的局部增加。液体燃料的喷射使反应流场的结构产生显著变化。预混气态燃料和空气燃烧的特点是大尺寸连贯的旋涡结构从突扩面脱落,此时火焰前峰位于旋涡结构边缘附近。相反,当气态和液态燃料共同燃烧时,在燃烧室前半部分形成一个散布的反应区域。在共同燃烧过程中末观察到低频火焰旋涡结构的脱落现象。压力和能量释放脉动的交叉频谱分析结果表明,液体燃料的喷入,在低频区(45～75Hz)减少了火焰与声振波型的耦合联系;在高频区(250Hz以上)增加了这一耦合联系。
The influence of the degree of liquid fuel spray evaporation on the heat release pattern and the stability of the sudden expansion combustor was studied. Ensure that the total fuel / air ratio is unchanged. At several liquid / gas fuel flow rates, simultaneous injection of both liquid and gaseous hydrocarbon fuels changes the degree of spray evaporation of the fuel. Variations in the degree of evaporation can change the average energy release pattern in the combustion chamber and the instantaneous flame structure and can change the amplitude and frequency of the pressure pulsations associated with combustion chamber instability. When the liquid fuel fraction increases from 0 to 50%, the total root mean square pressure pulsation drops to 50%. When the premixed gaseous fuel and air are burned, most of the pressure pulsation energy remains in the low frequency band of 45-65 Hz and this pressure pulsation contains the longitudinal acoustic modes of the combustion chamber. With the injection of liquid fuel, it is observed that the low frequency part is significantly reduced, and the high frequency part (250-380 Hz) is obviously increased. By measuring the CH radiation intensity, it is known that when the premixed gaseous fuel and air are burned, the volumetric energy release is distributed along the length of the entire combustion chamber. When liquid fuel is injected, the energy release area moves upstream and concentrates in the first half of the combustion chamber. In the region of maximum average energy release, the addition of liquid fuel also caused a local increase in the rms value of the heat release pulsation. The injection of liquid fuel causes a significant change in the structure of the reaction flow field. The characteristics of premixed gaseous fuel and air combustion are the large, coherent vortices that fall off of the flared face with the pre-flame peak near the edge of the vortex structure. In contrast, when the gaseous and liquid fuels co-burn, a scattered reaction zone is formed in the first half of the combustion chamber. In the process of co-combustion was observed at low frequency flame vortex shedding phenomenon. Crosstalk analysis of pressure and energy release pulsations showed that the injection of liquid fuel reduced the coupling of flame and acoustic modes in the low frequency range (45-75 Hz) and increased in the high frequency range (above 250 Hz) Coupling contact.