Numerical optimization and compatibility assessment of millimeter-scale Tesla turbines in ultra-micro gas turbines

Tesla turbines (TT) can offer several advantages over radial-axial (Ra-Ax) type ultra-micro turbines (UMT) at millimeter scales because of their uniquely simple manufacturability and mechanism. To justify this, we present a vis-à-vis comparison of the TT with three prior reference studies on Ra-Ax UMT. The operational parameters of the TT are considered based on the data reported for Ra-Ax UMT in the reference cases. These parameters include upstream-downstream pressure, temperature, rotor diameter, and revolutions per minute. We solve the Reynolds-averaged Navier-Stokes equation using the k-ϵ RNG turbulence model for air to calculate torque and mass flow rate. Subsequently, we examine the performance of TT at different disc gaps, nozzle throat widths, and inlet configurations. We report the efficiency, mass flow rate, and size of the TT in each of the cases. Our study helps identify that efficiency maximizes at any fixed operational parameters when the throat velocity approaches near-sonic conditions. However, the maximum torque on the rotor depends on the mass flow rate, throat velocity, and arm length. Our study reveals that optimized TT can enhance efficiency by 15% to 30% while taking up almost half as much space as Ra-Ax UMT. These findings indicate that TT might be an excellent alternative to Ra-Ax UMT as a part of ultra-micro gas turbine systems.