Messunsicherheit bei der Messung aerodynamisch relevanter Bliskmerkmale durch Informationsfusion

• Measurement uncertainty in the measurement of aerodynamically relevant blisk features by fusion of information

Schmidt, Ânderson; Schmitt, Robert H. (Thesis advisor); Gröger, Sophie (Thesis advisor)

Aachen : RWTH Aachen University (2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023

Abstract

Despite the setback, which aviation suffered in the recent past due to the coronavirus pandemic, air transport remains the only means of transport capable of covering long distances quickly. The fact that the engines used, in this case turbines, have a negative life cycle assessment, as well as the lack of a more efficient technology that could replace the kerosene currently used, means that large aircraft will have to continue to use combustion as an energy source in a window of about 15 to 20 years. Despite the positive historical record of developing new turbines such as turbo-fan and gear-fan, which have significantly reduced the average fuel burn per passenger or mass carried by increasing the bypass ratio (Fan- core engine ratio), this technology still has an energy balance that leaves potential for improvement. New prototypes of single-wing and V-wing aircraft are being tested that would allow an increase in propeller diameter (Fan) to core engine ratio (one propeller spinning slower and one core engine spinning at a high RPM) and thus a direct increase in bypass. But even these prototypes need time before they can replace models with turbines mounted under the wings. Therefore, reducing the length, diameter and number of stages of the core engines seems to be the best way to optimize the new generation of turbofans at the moment. Blisks (Blade Integrated Disk) are components used in the high compression area and are responsible for increasing the pressure of the air before it reaches the combustion chamber. However, despite the above requirements, this increase in pressure and consequently temperature can only be achieved by modifying the alloys used and new, more complex and aerodynamically efficient geometries. This represents a challenge for design, manufacturing and quality control. Measuring geometric requirements of blisks with tactile sensors on coordinate measuring machines (CMMs) is common practice. However, morphological effects typically cause errors in the compensation of the sensing ball as the sensor moves over complex geometries, primarily around the edge of the blade. Errors in the shape, position, effect of the sensing ball, and measurement strategy typically occur superimposed, making a differentiation of individual effects practically unfeasible. By using a digital twin, it is possible to simulate some of the above sources of error. With the help of a CMM simulator, an estimation of these effects, by introducing known deviations into the blisk CAD model, is possible. Understanding these morphological effects is an important step towards smart connected manufacturing. It also forms the basis for the comparison of different measurement principles, as well as the implementation of metrological traceability, which is an important point of quality assurance and measurement process capability. In this paper, as a first step, the author performs a historical review of the design features relevant to the aerodynamic control and efficient operation of compressor blades in order to understand the reasons and the measurement systems available at that time. With this information, a review of the state of the art is conducted, selecting the measurement systems of current industrial practice (CMM and SLP), which are used to systematically and methodically investigate the sources of uncertainty in the measurement. The reduction of the systematic components of the measurement uncertainty, caused by the incorrect position of the real compressor blade in relation to its CAD model, can be minimized by the fusion of the above mentioned measurement systems. Finally, the author compares the obtained results based on a standardized error of 95\% and thus can answer the research questions defined in this thesis.

Institutions

• Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University [417200]
• Chair of Production Metrology and Quality Management [417510]