基于时滞模型的纵向燃烧不稳定性分析

Analysis of Longitudinal Combustion Instability

关键词:  集总燃烧时滞模型  系统耗散率  纵向燃烧不稳定性

Key words:  Concentrated combustion time-lag model  System damping coefficient  Longitudinal combustion instability

摘要:

在集总燃烧时滞模型的基础上，研究了系统耗散对燃烧稳定性的影响。通过在流动控制方程中考虑剪应力引起的阻尼项，利用燃烧锋面处的匹配边界条件，推导了考虑耗散效应的集总燃烧时滞模型。其次，采用Tim Liuwen等的研究方法，通过对不稳定燃烧试车数据进行滤波操作和相关性计算，间接获得了各阶声学模态对应的耗散系数。将其作为阻尼项加入到新的模型中，重新计算了本次试车的稳定性曲线。结果显示，各阶耗散系数均小于0.1，且耗散系数会随着模态阶数的提高而降低。另一方面，考虑耗散后的系统增益较原始模型及现有模型降低了48%，说明系统耗散的加入影响了模型的预测精度。进一步研究证明，耗散的增加会降低系统增益，从而提高其稳定性。

Abstract:

Based on concentrated combustion time-lag model，the effects of system damping on combustion stability were studied here. Firstly，flow induced shear stress was introduced into the governing equation as resistance term，and by using the match boundary layer at combustion front，new concentrated time-lag model considering the damping effect was established. Secondly，through band-pass filtering and correlation analysis，Tim Liuwen’s method was adopted to indirectly extract damping coefficients for each acoustic model from the test data of unstable combustor. At last，the newly derived damping coefficients were added into the new model as resistance term，and the stability curve for this test was recomputed. It is indicated that the damping coefficient of each mode is not larger than 0.1，and the damping coefficient will be reduced as the model number improved. On the other hand，compared with the original model and contemporary model，system gain was reduced by about 48% when considering the damping effect，which means that introducing the system damping has some influence on the model precision for prediction. Furthermore，it is proved that increasing system damping will reduce the system gain and improve its stability simultaneously.