Heat Transfer Characteristics of a Rotor-Stator System With Small Radial Outflow

In some cases, the mass flow rate needed to prevent ingress through rim seals in turbine is smaller than that entrained by a free disk. In order to obtain the heat transfer features of the rotor-stator system at such a small mass flow rate, a combined computational and theoretical study has been carried out. It is found that the average Nusselt number (Nu_av) on the rotor drops approximately linearly down to zero with decreasing turbulent flow parameter (λ_t) when λ_t is smaller than λ_t,c (λ_t,c < λ_t,fd), while Nu_av almost keeps constant when λ_t is larger than λ_t,c. A correlation between Nu_av and λ_t has been developed, which is expected to be useful in determining disk temperatures in the preliminary design of an internal air cooling system. The Eckert number, which can express the relationship between heat generated by windage and heat conducted through disk, turns out to be an important nondimensional number in describing the heat transfer features of such rotor-stator systems. Moreover, the effect of rotational speed on heat transfer when λ_t,c<λ_t<λ_t,fd has been studied, further identifying the significance of the Eckert number.