Christian Dupont

Blade Manufacturing Tolerances Definition for a Mistuned Industrial Bladed Disk

This paper deals with the characterization of the blade manufacturing geometric tolerances in order to get a given level of amplification in the forced response of a mistimed bladed-disk. The theory is based on the use of a nonparametric probabilistic model of blade random uncertainties, The dispersion parameters controlling the nonparametric model are estimated as a function of the geometric tolerances. The industrial application is devoted to the mistuning analysis of a 22 blades wide chord fan stage. Centrifugal stiffening due to rotational effects is also included. The results obtained validate the efficiency and the reliability of the method on three-dimensional bladed disks.

Mistuning Phenomena on Bladed Disk: Industrial Methods and Applications

This paper deals with the methods used at Snecma (SAFRAN Group) to simulate the real mistuned dynamic behavior of bladed disks. Many applications of the method on industrial cases are also presented. The dissymmetry of a real bladed disk, which is mainly generated by small deviations in its geometry, leads to different dynamic impedances of the blades. These variations in impedance cause significant amplification of the forced response of the bladed disk. We propose to focus on industrial methods that can be used to simulate the mistuned dynamic behavior of a bladed disk in the case of small “frequency mistuning” or of greater “large mistuning”. This method, based on the modal synthesis technique (Benfield and Hruda family), can be classified as a “first generation method”. The first originality of this method consists in taking into account major mistuning, such as that induced by an FOD event. A second innovation concerns the use of these methods to assess in probabilistic terms the correction factor to apply to the maximum dynamic level measured during engine certification tests. The first part of the paper relates to the proposed method and its validation for large-scale “shape” mistuning on an academic test case. In the second section, we present a number of industrial applications: • An application of “geometric mistuning” is presented on a bladed disk after an FOD event. The same kind of analysis as previously described is carried out and the numerical results are commented. • The mistuning analyses are carried out on an industrial blisk with a local defect. The sensitivity of the response amplification factor is calculated versus the mistuning rate using a probabilistic approach. • Another application of the mistuning strategy is discussed: it concerns the use of the mistuning method to specify the correction factor of partial dynamic strain gauge measurements in order to assess the maximum level of a bladed disk. • The last application is dedicated to the simulation of intentional mistuning to increase the aeroelastic stability of an industrial test case.Copyright

Forced Response Prediction: Methodology for the Design of HP Compressors Bladed Disks

This paper presents a general approach related to bladed disk forced response prediction and a typical way to use it in the design process. Firstly, a good confidence level in prediction tools must be reached. The first application is a highly instrumented HP compressor blisk representative of a real engine environment. Simulation of forced response is compared to measurements in order to check the accuracy of prediction. For this test case, the results obtained are in very good agreement with measurements. The good quality of prediction is due to the complete characterization performed on the test case: all the influent parameters were identified before testing. But during the design process, many important parameters are unknown and this level of accuracy can not be obtained. Nevertheless, forced response prediction in the early design process can provide interesting information even if uncertainties are high for some parameters. As an illustration, a second application is proposed, based on the design experience of a new HP compressor of a known engine family. Some forced response predictions were performed during development and compared afterwards with measurements obtained during engine testing. This analysis has permitted to confirm some technical choices and to assess the High Cycle Fatigue risk associated to this new engine configuration.Copyright