考虑闭合效应的刷式密封泄漏特性研究

Investigations on Leakage Flow Characteristics of Brush Seal with Consideration of Blow Down Effect

采用基于非线性Darcian多孔介质模型的Reynolds-Averaged Navier-Stokes(RANS)方程的数值方法研究实验测量的零间隙和具有间隙的刷式密封在不同压比和转速下的泄漏特性,提出针对刷式密封闭合效应的间隙修正公式。考虑闭合效应后具有间隙的刷式密封泄漏量的预测结果与实验数据吻合,验证所建立刷式密封闭合效应修正模型的有效性。研究结果表明:刷丝束顶部与转轴间的间隙导致刷丝束内部压力降低且具有较为明显的径向压差,径向压差的存在导致刷丝束产生闭合效应,进而减小了刷式密封的有效密封间隙;闭合效应使得刷式密封有效间隙随着压比升高而减小,数值计算刷式密封泄漏特性时考虑闭合效应可以显著提高预测精度;在相同压比和转速下,具有间隙的刷式密封的泄漏量明显大于零间隙刷式密封的泄漏量;刷式密封的泄漏量随着压比的增大而增大;在所研究的转速范围内转速对刷式密封的泄漏特性的影响有限。

The leakage flow characteristics of the experimental brush seal with zero clearance and clearance at different pressure ratios and rotational speeds were numerically investigated using Reynolds-Averaged Navier-Stokes （RANS） solutions based on the non-linear Darcian porous medium model. The corrected formula for the blow down effect of brush seal was presented. The numerical predicted leakage flow rate of the clearance brush seal was in well agreement with the experimental data with consideration of blow down effect, which validated the corrected formula for the brush seal blow down effect. The research results show that the clearance between the bristle tip and the shaft results in the decrease of the pressure and relatively obvious radial pressure difference in the bristle pack of brush seal, and the radial pressure difference leads the blow down effect of bristle pack, and then leads to the reduction of effective clearance of brush seal. The effective clearance of brush seal is decreased with the increasing of pressure ratio due to the blow down effect. The prediction accuracy of the leakage flow rate of brush seal can be improved significantly with consideration of blow down effect. The leakage flow rate of the clearance brush seal is larger than that of the zero clearance case at the same pressure ratio and rotational speed. The leakage flow rate of brush seal is increased with the increasing of the pressure ratio, while the rotational speed has less effect on leakage flow rate in the presented rotational speeds range.