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 x 105 and 7.42 x 105
,respectively,
while the dimensionless sealing air flow rate ranges from 3047 to 8310. Themeasurement
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 presentstudy, a modified orifice model that takesthe tangential velocity
into account is proposed and a new factorH isintroduced to well explain the mechanism
of the ingress