| Hot gas ingestion in turbine cavity causes ablation damage,reduces the life and reliability of the turbine disc.To protect the turbine disc,the cooling air is bled from the compressor for sealing and cooling of turbine cavity.By arranging a high sealing effectiveness rim seal structure in the rim clearance and the rotor blade extension root section,the gas ingestion can be improved,the consumption of the sealed cooling air can be reduced,and the low temperature purge flow and the induced aerodynamic loss can be reduced.The design of the rim seal structure is based on the analysis of the gas ingestion flow field in the rotor-stator cavity and the rim clearance area.The ingestion field in rotor-stator cavity is analyzed,and the mechanism of gas ingestion in the basic rotor-stator cavity is summarized.By constructing a "stator-stator cavity" buffer chamber to reduce the swirl ratio of the ingress flow,a radial-radial-axial clearance rim seal is proposed,which further reduces the minimum seal flow rate by about 11.24% compared to the radial-axial clearance rim seal.According to the analysis in the ingestion field in the front cavity of a high pressure turbine of a marine gas turbine,increasing the sealing air helps to improve the seal effectiveness of the rotor-stator system.However,every 1% increase in the sealing air flow will result in a decrease of the stage power by about 0.32% and a decrease in the aerodynamic efficiency by about 0.33%.The cavity and the chute clearance structures are improved based on the gas ingestion characteristics in the chute clearance and the labyrinth-clearance theory,and the local reflow and self-sealing effect of the chute clearance are strengthened,and the sealing effectiveness of the full cavity is improved,and the consumption of the cooling air for seal is also reduced.Starting from the real multi-physics environment where the turbine disc is located,the conjugate heat transfer model is established to improve the prediction of the heat transfer characteristics inside the turbine cavity.The main purpose is to predict the effect of gas ingestion on the temperature field of the turbine disc.Based on the static finite element method,the physical deformation of the turbine disc under multi-load coupling effect is obtained,and the hot running rim seal clearance is obtained to explore the gas ingestion problem under the hot running conditions.The results show that the radial growth of the rotor disc is about 11.89-18.11% of the thickness of the disc lip.The hot running rim seal clearance strengthens the gas ingestion and purge flow,resulting in a reduction in the sealing effectiveness about 2.35%-11.12% when compared with the original cold state.Through the refined unsteady calculation,it is determined that there are Kelvin Helmholtz vortices in the rotor-stator rim seal clearance.Through the analysis in the dynamic characteristics of the large-scale vortex structure in the rim seal area,it is concluded that the vortex frequency is about 5.61 times the rotor frequency,the vortex speed is about 0.35 times the rotor speed,and the number of vortices in the whole circumference of the clearance is about 17.When the lips of the rotor and stator discs are negatively dislocated,these dislocations in lips strengthen the gas ingestion.The whirling rotor forms dynamic dislocated lips of rotor and stator discs.The results show that the whirling rotor disc can increase the sealing effectiveness,improve the gas ingestion phenomenon.The unsteady flow in the low-radius region of the rotor-stator cavity is completely at the same vibration frequency of whirling rotor disc,and the unsteady characteristics of the flow in the high radius region are determined by the vibration frequency of the rotor disc and the frequency of the Kelvin Helmholtz vortex at the rim clearance. |
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