Calculation of the Overspeed at Emergency Shutdown of a Transonic Test Turbine Facility Using a Web-Based Thermodynamic Simulation Tool

The Institute of Thermal Turbomachinery and Machine Dynamics at Graz University of Technology operates a Transonic Test Turbine Facility of 3 MW power. The test turbine is a two-spool two-stage turbine. The high-pressure high-speed stage is connected to a brake compressor via a coupling, whereas the second low-pressure low-speed stage is connected to a water brake. In the case of a coupling failure or a break-off of the water brake, an emergency shutdown is triggered in order to avoid excessive overspeed of the turbine stages, leading to blade dismantling or even disk bursting. For a previous one-stage setup, the shutdown procedure was developed and adjusted with the help of a dynamic thermodynamic simulation of the test rig which allowed to calculate the occurring maximum speeds. With this approach, the safe operation of the test rig shall be guaranteed. This work presents a simulation model for the existing two-spool two-stage test rig. With a dynamic simulation, the overspeeds of the high-speed and low-speed shafts are calculated for the cases of coupling failure and water brake break-off as well as for the case of both shafts running freely. In this way, it is checked that the maximum speeds of the shafts in the case of an emergency stay within the allowable limits. However, a break-off of the water brake in July 2022 led to higher overspeeds as predicted. The following investigations detected an error in the control system, which could have harmed the low-pressure turbine. For the modeling and simulation, the newly developed web-based version of a thermodynamic simulation tool, IPSE GO, was used because it allows easy access to the simulation by all partners via a web browser.