AM Testing (Italy)

Abstract Variable Guide Vanes such as Inlet Guide Vanes (IGVs) and Nozzle Guide Vanes (NGVs) are a typical design feature included in gas turbines and axial expanders to achieve improved performance in off-design conditions and, consequently, operational flexibility. In the last years the evolution of the energy market has challenged these components, which were already characterized by an intrinsic complexity, to achieve higher availability performances. For this reason, a deeper experimental characterization of the mechanical behavior of these assemblies has become of interest, especially when considering highly loaded nozzles. In particular, the investigation of the kinematic pairs of NGV is becoming very important in some design configuration. This paper describes the design and the commissioning of a novel advanced bench designed to test full-scale NGVs geometries constituted by stems supported by bushing couples. The bench is designed to perform the measurement of the friction coefficient of the kinematic chain and then to accomplish continuous endurance testing of the bushing/stem pair at high temperature. Details are given regarding the design of the bench components which allow testing of bushing different by size and manufacturing technology. The design verifications needed for the proper bench operation are presented. In addition, the testing procedure is also included which will provide in the upcoming months useful data regarding clearance evolution and, more in general, component lifing.

Abstract Tilting pad journal bearings (TPJBs) are crucial elements in turbomachinery applications providing stiffness and damping characteristics that determine rotor system dynamic behavior. Hence, a correct design and an accurate dynamic properties prediction is fundamental for the successful industrial operation of rotating machinery. Current design trends in turbomachinery aiming at higher efficiency and power through weight optimization and higher operating speeds determine the development of large flexible rotors that are particularly important from the rotordynamic standpoint. The dynamic feasibility of this type of machine relies on bearing stiffness and damping characteristics that must be predicted with a certain level of confidence in order to increase the accuracy of the expected rotordynamic behaviour and avoid unpredicted vibration issues when rotors are operated. Furthermore, large centrifugal compressors commonly used in Liquified Natural Gas (LNG) applications make the bearings operate at very high peripheral speed where the transition from laminar to turbulent regime occurs, increasing the necessity of predictions accuracy. In this paper a test campaign on different large TPJB solutions operating in turbulent lubrication regime has been performed on a dedicated test rig designed for investigations on large size high-performance oil bearings. In the present work both static performance and dynamic identification of the tested TPJB solutions are presented and compared to numerical model predictions. The results of an uncertainty quantification, performed to validate the experimental results, are also shown.