Experiments on Front- and Aft- Disk Cavity Ingestion in a Subscale 1.5-Stage Axial Turbine

Abstract

This paper describes experiments performed in a subscale 1.5-stage axial air turbine in which ingestion of mainstream air into the front and aft disk cavities was measured. The front disk cavity is upstream of the rotor, the aft disk cavity is downstream of the rotor. Both disk cavities contain a labyrinth seal at a radially inboard location; this seal divides the cavity into a ‘rim cavity’ and an ‘inner cavity’. The front rim cavity features a double seal with radial clearance and axial overlap at its periphery; the aft rim cavity double seal possesses axial gap. Results are reported for three experiment sets, each set defined by the main air flow rate and rotor speed. Furthermore, each set comprises four different purge air flow rates. The initial step in each experiment was the measurement of time-average static pressure distribution in the main gas annulus and the disk cavities to establish the steady-state pressure differentials that contribute to ingestion into and egress from the cavities. This was followed by the measurement of tracer gas (CO2) concentration distribution in the disk cavities to quantify the ingestion. In addition to the pressure and concentration (in terms of sealing effectiveness) results, the mass flow rates of ingested main air into the front and aft rim cavities are reported for the various experimental conditions. Both inner cavities were found to be completely sealed against ingestion. Ingestion and egress discharge coefficients based on an orifice model are reported for the front and aft double rim seals; their trends are quite different from those of single rim seals with axial overlap and radial clearance reported earlier.

Numerical modeling of hot gas ingestion into the rotor-stator disk cavities of a subscale 1.5-stage axial gas turbine

“…The residual target is that the normalized root mean square (RMS) errors for each conservation balance over the entire mesh fell to less than 10 À5 . The value for different boundary conditions are adapted from ASU rig data [17] and are listed in Table 1.…”

“…The current Computational Fluid Dynamic simulations were carried out based on the gas turbine rig at Arizona State University [17]. Fig.…”

“…This smaller gradient across the lower lip of the double lip seal suggested that it is less sensitive to mainstream-cavity interactions. Recent studies by Balasubramanian et al [17], Patinios et al [18], and Scobie et al [19] have been focused on 1.5-stage axial gas turbines. Balasubramanian et al [17] performed several experiments to measure the ingestion of mainstream air into the front and aft disk cavities in a subscale 1.5-stage axial air turbine.…”

“…Recent studies by Balasubramanian et al [17], Patinios et al [18], and Scobie et al [19] have been focused on 1.5-stage axial gas turbines. Balasubramanian et al [17] performed several experiments to measure the ingestion of mainstream air into the front and aft disk cavities in a subscale 1.5-stage axial air turbine. Different experiment sets with different main air flow rates, rotor speeds and purge air flow rates were examined.…”

Effect of Various Coolant Mass Flow Rates on Sealing Effectiveness of Turbine Blade Rim Seal at First Stage Gas Turbine Experimental Facility

“…They found out that mass flow rate of rim seal and flow rate ratio of main flow and secondary flow is important factor for sealing efficiency. Balasubramanian, J. et al [40] constructed the experimental facility with single rim seal. They found out the sealing effectiveness of rim seal in different operating conditions.…”