Figure 1: Scheme of typical labyrinth seal [1] COMPARISON OF LABYRINTH SEAL CALCULATION AND REAL AIRCRAFT TURBINE ENGINE MEASUREMENT M. Čížek 1 , T. Vampola 1 , L. Popelka 1 1 Center of Aviation and Space Research, Faculty of Mechanical Engineering, Czech Technical University in Prague, Jugoslávských partyzánů 1580/3, 16000, Prague Abstract This paper describes comparison between 3D CFD calculation of labyrinth seal of a turbine engine and measurement of actual advanced turbine engine in test facility. The goal is to verify capability of the 3D CFD modelling and obtain more insight into air flow path in the labyrinth seal. The total temperature was revealed not being a constant value through the labyrinth seal, thus driving design and even service trend monitoring consequences. Keywords: Labyrinth Seal, Aircraft Turbine Engine, CFD, Test 1. Introduction The labyrinth seal of aircraft turbine engine is an important part of air flow path in the engine. The air flow path consists of two vital branches [1]. Primary stream consists of compressor air flow, combustor contribution and turbine work stage(s) in a standard turbine engine architecture. Secondary air flow is used for cooling hot parts, bounded between rotating parts and stator counterparts (e.g. between shaft and stator where the shaft has very high rotational speed). Typical labyrinth seal scheme is shown in Figure 1. The labyrinth seal is produced as a part of shaft or within stator parts. Presented paper is focused on the shaft configuration. The first research of labyrinth seals was started with steam turbines where the labyrinth seals were located to the tip of blades [2]. The purpose of labyrinth seal is eliminating mass flow passing through the seals [3], because air flow leaked through the seal does not produce work in primary branch of flow. Reduction of the detrimental leakage mass flow is enabled by a circumferential swirl, created in cavities between the teeth. Most of the research conducted on labyrinth seals was associated with steam turbines. However, there are differences in boundary conditions between steam turbine and aircraft turbine engine: the key difference lies in rotation speed where the speed is greater in turbine engines, in turn influencing the strength of swirl and the resulting mass flow though the seal [6]. With the development of CFD increased number of reliable numerical simulations of labyrinth seals appears in the literature, e.g. [7]. At first instance, radial clearance, i.e. space located between rotating part (teeth) and non-rotating part (it is straight shape) [8], can be studied. Presented configuration is using the rotating teeth [5]. Such a flow path was simulated in the CFD software. The goal of this article is verification of the CFD results by comparison with reduced data measure in the test facility. Research was also aimed at investigation of possible changes of total temperature. Knowledge of the total temperature values and its development in labyrinth seal is important for designers of turbine engines. They can better specify e.g. material of rotating parts and manufacturing process. A better selection of material properties can be successfully pursued. Labyrinth seal in an aircraft turbine engine is specific by radial clearance. Clearance is smaller than in the steam turbines and rotational speed is higher. 2. CFD Calculation Computational domain of the 3D CFD calculation consisted of three volumes. This configuration has been chosen because it enables a better description of air flow through the labyrinth seal. It is helpful in capturing the properties of a circumferential swirl. TOPICAL PROBLEMS OF FLUID MECHANICS 19 _______________________________________________________________________ DOI: https://doi.org/10.14311/TPFM.2020.003