A new continuously running turbine facility is being constructed in the new Advanced Performance Gas Turbine Laboratory at the University of Notre Dame. The purpose of this turbine rig is to provide an environment for the development of performance enhancing flow control technologies at conditions that are similar to those in real engines. The unique design features include using the power generated by the turbine to load-share with a motor to drive a centrifugal compressor which supplies the air to drive the turbine, and re-circulating most of the compressor discharge air to the turbine inlet to control the inlet temperature.
To achieve a higher pressure ratio within the limited power, the compressor that supplies the air for the turbine is placed downstream of the turbine as a vacuum pump. The power generated by the turbine is used to load share with a variable-speed AC motor, whose power is used only for balancing the power gap between the turbine and the compressor. The shaft of the motor between the turbine and compressor was configured such that mechanical couplings can be attached at both ends. One end receives the turbine power through a torque meter. The other end drives the compressor through a gearbox with the sum of the turbine and motor power. This arrangement also provides open space at the inlet to the turbine for easy access.
To avoid the condensation and freezing due to the large temperature drop after the turbine, a large amount (depending on turbine design and required turbine downstream temperature) of the compressor discharge air is re-circulated back to the turbine through a mixing chamber to keep the temperature after turbine close to the laboratory temperature. The temperature into turbine is controlled by varying the amount of re-circulated mass flow using a throttle valve. Since the pressure of the turbine flow is below atmospheric pressure, a small mount of flow can be easily drawn from atmosphere in order to provide cooling and purge flow. A valve and flow meter are used to control the cooling flow rate. This flow can be cooled to control the temperature ratio of the cooling flow and turbine main flow.
The facility, as defined by the characteristics of the 500HP drive motor, centrifugal compressor, and piping system, can be used with a wide range of turbine blade designs. High loading axial turbines can be tested in this facility at a pressure ratio of 2.1. Figure 2 compares the possible turbine design points of the Notre Dame turbine rig with those of some existing industry research turbines in a stage loading versus flow coefficient plot from Marttingly’s book. A detailed description of this work was given by Ma et al in Design of a Transonic Research Turbine Facility.
