Turbomachinery wakes: Differential work and mixing losses

In this paper the mixing of stator wakes in turbomachinery is considered An extension is trend An attempt is also made to understand better the work t ransfer process between a made to the existing model of Denton (1993), whic h addresses the effects of acceleration before mixing. Denton showed that i f a total pressure wake was accelerated, mixing loss diminished, and vice v ersa. Here a total temperature wake is shown to exhibit a reverse stator wa ke and a rotor. The paper concentrates on axial turbines, but a brief look at compressors is included. It is argued that the free-stream work is not t he same as the wake work, and the concept of "Differential Work" is introdu ced. A simple steady velocity triangle based model is proposed to give an e stimate of the ratio of wake work to free-stream work (mu, see later). The model is compared to an unsteady CFD result to offer some verification of t he assumptions. It is concluded that the rotodynamic work process tends to reduce total pressure wake depths in turbines and compressors and therefore mixing losses. The miring loss due to total temperature wakes is less stro ngly affected by the differential work process.