Periodic Reporting for period 2 - AIRSEAL (Airflow characterization through rotating labyrinth seal)
Periodo di rendicontazione: 2020-05-01 al 2022-11-30
The AIRSEAL project addresses Topic JTI-CS2-2018-CfP08-ENG-01-34, “Airflow characterization through rotating labyrinth seal” under the Joint Technical Programme reference "Ultra-high Bypass and High Propulsive Efficiency Geared Turbofans", ITD Engines WP 2.4.2 (Low Pressure Turbine), Clean Sky 2.
Rising gas turbine performance demands have led to higher gas temperatures and pressure ratios, necessitating further minimization and control of internal gas leakages due to increased cooling flows. The application of new seal designs and improved understanding of leakage flow characteristics are of particular importance in order to meet future performance goals. Understanding the flow in labyrinth seals is fundamentally important in developing improved seal concepts to enhance and predict component performance in gas turbines engines.
The main objective of AIRSEAL project was to test different labyrinth seal configurations to determine the pressure loss characteristics for different rotor speeds, radial clearances and at different temperature and pressure ratios. The test rig, specifically developed in this project, is able to test a seal configuration in a simplified, yet representative, environment. The tests have been divided in two campaigns, the complexity of the second campaign being dependent on the results and conclusions of the first.
A suitable set of labyrinth seals configurations have been tested in order to define the final geometry of the seals, final air pressures, final air temperatures, final radial clearances and final rotor speed. The test data which has been acquired during tests has been used to fill numerical model predictions in order to perform a final analysis. The first test campaign has been conducted to extend experimental coverage on the effects of knife angle, tip thickness, pitch, height, number of knives, and land surface roughness. This entire data base will be utilized in the development of the LPT model. A second test campaign followed. In this, the conclusions of the first campaign enabled the optimization of the test matrix (test cases to be performed) and test procedures with the goal to achieve final conclusions on the significance of different parameters on the efficiency of the labyrinth seals.
During tests, parameters such as pressure ratio, upstream temperature, upstream angle of incidence, and rotor rotation speed were varied. The tests were performed with one rotor and three types of stators. In the two test campaigns, a total of 720 tests have been performed with the labyrinth seals.
Rising gas turbine performance demands have led to higher gas temperatures and pressure ratios, necessitating further minimization and control of internal gas leakages due to increased cooling flows. The application of new seal designs and improved understanding of leakage flow characteristics are of particular importance in order to meet future performance goals. Understanding the flow in labyrinth seals is fundamentally important in developing improved seal concepts to enhance and predict component performance in gas turbines engines.
The main objective of AIRSEAL project was to test different labyrinth seal configurations to determine the pressure loss characteristics for different rotor speeds, radial clearances and at different temperature and pressure ratios. The test rig, specifically developed in this project, is able to test a seal configuration in a simplified, yet representative, environment. The tests have been divided in two campaigns, the complexity of the second campaign being dependent on the results and conclusions of the first.
A suitable set of labyrinth seals configurations have been tested in order to define the final geometry of the seals, final air pressures, final air temperatures, final radial clearances and final rotor speed. The test data which has been acquired during tests has been used to fill numerical model predictions in order to perform a final analysis. The first test campaign has been conducted to extend experimental coverage on the effects of knife angle, tip thickness, pitch, height, number of knives, and land surface roughness. This entire data base will be utilized in the development of the LPT model. A second test campaign followed. In this, the conclusions of the first campaign enabled the optimization of the test matrix (test cases to be performed) and test procedures with the goal to achieve final conclusions on the significance of different parameters on the efficiency of the labyrinth seals.
During tests, parameters such as pressure ratio, upstream temperature, upstream angle of incidence, and rotor rotation speed were varied. The tests were performed with one rotor and three types of stators. In the two test campaigns, a total of 720 tests have been performed with the labyrinth seals.
The AIRSEAL test bench has been designed, manufactured, assembled, installed, and tested at COMOTI's facilities with the involvement of both project partners. Throughout the development and testing phases, the Topic Leader was engaged for validation of the intermediate and final results. At the end of the commissioning phase, the test bench was demonstrated to perform its functions within the entire working envelope: up to 15,000 rpm, up to 150 °C, pressure ratios of 0.5 to 1, with the pressure difference under 2 bar, and with data recording as required.
For the actual test campaigns, three specific labyrinth seals (consisting of a stator and a rotor, working together to minimize gas leakage) were manufactured according to Topic Leader specifications. The seals met dimensional requirements and their conformity was documented throughout the manufacturing process. The geometry and characteristics of the rotors and stators were defined as per Topic Leader requests.
The commissioning and testing of the AIRSEAL Test Bench and the completion of test campaigns #1 and #2 have provided a wealth of data on the performance of labyrinth seals tested in similar conditions of labyrinth seals of aerospace engines. A set of test data has been made available to the scientific community through the open access ZENODO repository proposed by the Clean Sky JU. The link to the data is https://doi.org/10.5281/zenodo.7763679 .
The raw data files from the 720 tests performed have been processed and analyzed using a combination of automated and manual procedures, and the stabilized regimes (the actual tests) have been identified, graphically represented, and saved as individual files for ease of access and speed of processing. Regression analysis has been utilized to explore the correlation between the dependent variable (response - airflow) and the independent variables (predictor variables – pressure ratio, rotor speed, temperature, and clearance) to develop a mathematical model that includes linear, quadratic, and interaction terms.
Regarding the further exploitation of the project results, the Topic Leader is planning to calibrate a CFD model of the test rig based on experimental tests, with the aim of establishing a numerical methodology capable of accurately predicting labyrinth seal performance. Discussions with the Topic Leader are ongoing to expand research and development on labyrinth seals, taking into account the extensive range and high levels of operating parameters provided by the AIRSEAL Test Bench. The acquired know-how will be utilized in new European research projects and commercial ventures within the aerospace and industrial sectors.
Project results were disseminated through various channels, including the COMOTI and AIRSEAL project websites, press articles, scientific papers, and conference participation. Additionally, the project was showcased at fairs, exhibitions, and academic presentations. The AIRSEAL project also facilitated the development of a complementary initiative, the INFRASEAL project, which focuses on a broader research infrastructure for rotating labyrinth seals characterization.
For the actual test campaigns, three specific labyrinth seals (consisting of a stator and a rotor, working together to minimize gas leakage) were manufactured according to Topic Leader specifications. The seals met dimensional requirements and their conformity was documented throughout the manufacturing process. The geometry and characteristics of the rotors and stators were defined as per Topic Leader requests.
The commissioning and testing of the AIRSEAL Test Bench and the completion of test campaigns #1 and #2 have provided a wealth of data on the performance of labyrinth seals tested in similar conditions of labyrinth seals of aerospace engines. A set of test data has been made available to the scientific community through the open access ZENODO repository proposed by the Clean Sky JU. The link to the data is https://doi.org/10.5281/zenodo.7763679 .
The raw data files from the 720 tests performed have been processed and analyzed using a combination of automated and manual procedures, and the stabilized regimes (the actual tests) have been identified, graphically represented, and saved as individual files for ease of access and speed of processing. Regression analysis has been utilized to explore the correlation between the dependent variable (response - airflow) and the independent variables (predictor variables – pressure ratio, rotor speed, temperature, and clearance) to develop a mathematical model that includes linear, quadratic, and interaction terms.
Regarding the further exploitation of the project results, the Topic Leader is planning to calibrate a CFD model of the test rig based on experimental tests, with the aim of establishing a numerical methodology capable of accurately predicting labyrinth seal performance. Discussions with the Topic Leader are ongoing to expand research and development on labyrinth seals, taking into account the extensive range and high levels of operating parameters provided by the AIRSEAL Test Bench. The acquired know-how will be utilized in new European research projects and commercial ventures within the aerospace and industrial sectors.
Project results were disseminated through various channels, including the COMOTI and AIRSEAL project websites, press articles, scientific papers, and conference participation. Additionally, the project was showcased at fairs, exhibitions, and academic presentations. The AIRSEAL project also facilitated the development of a complementary initiative, the INFRASEAL project, which focuses on a broader research infrastructure for rotating labyrinth seals characterization.
The project work is based on innovative techniques and makes use of the latest developments in the field of labyrinth seal testing. Various modern equipments and processing methods are used for the manufacturing of new type of labyrinths.
One of the ground-breaking innovations that the project proposes is that the radial clearance measurements will be done during testing runs while the rotor (disk + labyrinth seal) is rotating. In this way, the real clearance value during testing could be used in optimizing the mathematical model of the sealing. Another ground breaking innovation resides in the automation of the test bench - integrated centralized control and data acquisition systems.
The AIRSEAL project generated a full set of functional data for the ITD Engines modules in order to finalize the LPT Preliminary Design Review (PDR) along with the test bench itself and the test specimens.
Related to the UHPE high-level objectives, the expected impacts of AIRSEAL project are: contribution to a 15% reduction in CO2 compared to 2000 baseline, a reduction in NOX and a 6dB noise reduction, goals also in line with ACARE objectives.
The successful completion of the project will have a significant impact on the labyrinth seal design time and, consequently, cost, as it allows the removal of most of the time consuming control strategies, of research and testing. Furthermore, the proposed concept and approaches enables a better optimization. The aim of project is to aid at improving the environment control techniques for the aerospace facilities by at least 10% in terms of efficiency, with respect to present efficiency values. This will enable a more efficient design of the LPT, with impact not only economically, but also on the operation.
One of the ground-breaking innovations that the project proposes is that the radial clearance measurements will be done during testing runs while the rotor (disk + labyrinth seal) is rotating. In this way, the real clearance value during testing could be used in optimizing the mathematical model of the sealing. Another ground breaking innovation resides in the automation of the test bench - integrated centralized control and data acquisition systems.
The AIRSEAL project generated a full set of functional data for the ITD Engines modules in order to finalize the LPT Preliminary Design Review (PDR) along with the test bench itself and the test specimens.
Related to the UHPE high-level objectives, the expected impacts of AIRSEAL project are: contribution to a 15% reduction in CO2 compared to 2000 baseline, a reduction in NOX and a 6dB noise reduction, goals also in line with ACARE objectives.
The successful completion of the project will have a significant impact on the labyrinth seal design time and, consequently, cost, as it allows the removal of most of the time consuming control strategies, of research and testing. Furthermore, the proposed concept and approaches enables a better optimization. The aim of project is to aid at improving the environment control techniques for the aerospace facilities by at least 10% in terms of efficiency, with respect to present efficiency values. This will enable a more efficient design of the LPT, with impact not only economically, but also on the operation.