Development of a New Factor for Hot Gas Ingestion Through Rim Seal

This article presents a further investigation on the mechanism of hot gas ingestion by exploring the ingress with complicated cavity generated by the rotor-mounted cylinder protrusion. During the experiment, a cavity with 32 cylinder protrusions circumferentially distributed in rotor that contained 59 blades is applied. The annulus Reynolds number and rotating Reynolds number are fixed to be 1.77 × 10⁵ and 7.42 × 10⁵, respectively, while the dimensionless sealing air flow rate ranges from 3047 to 8310. The measurement of CO₂ concentration and pressure is conducted. Experimental results show that the sealing efficiency is improved with the introduction of the cylinder protrusions even the static pressure inside cavity is found to be reduced. The effect of the circumferentially nonuniform cavity pressure wave is considered and added into the orifice model, and the effect of some impact factors, i.e., the amplitude, initial phase angle difference, and frequency of the cavity pressure wave, on hot gas ingestion is theoretically discussed in detail. However, it is noted that the cavity pressure wave that was introduced by 32 cylinder rotor-mounted protrusions is found to have insignificant effect on improving the sealing efficiency. In the present study, a modified orifice model that takes the tangential velocity into account is proposed and a new factor H is introduced to well explain the mechanism of the ingress.