A computational investigation of hot gas ingress through the rim seal of a counter-rotating turbine cavity with annulus

The hot gas ingestion through rim seals of counter-rotating turbine disks with annulus flow is investigated by numerical simulation in this paper. Three models were calculated in this paper, counter-rotating turbine cavity with annulus and radial sealing inlet, the same geometric configuration but in rotorstator system and the counter-rotating turbine cavity without annulus. The axial Reynolds number of annulus was set at 5.99×10⁵ and rotating Reynolds number was set at 2.35×10⁵, the non-dimensional sealing flow rate was changed from 279 to 1116. The results of simulation indicated that counter-rotating cavity with radial inlet was found to have a much higher sealing efficiency than the stator-rotor cavity at the equivalent condition. The flow path of ingestion gas was considered to be the cause for this. For the difference of flow structure of cavities, the annulus air is ingested the middle of cavity for counter-rotating cavity rather than flowed towards the static wall for rotor-stator cavity. Therefore, the sealing efficiency for counter-rotating cavity is high in both of the walls but low inside the cavity. In addition, preswirl of sealing air was found to affect the sealing efficiency by changing the flow inside cavity and making the early mixing of sealing air and ingestion gas.