Most part of the work carried out in the 1st period of the START project deals with the development and assessment of a multiphysics tool, named U-THERM3D, for high-fidelity predictions of metal temperature using the code ANSYS Fluent in the context of Scale Resolving Simulations. Such activity is in charge to UNIFI. In the past years, a 3D coupled approach for the thermal design of combustor liners was developed by UNIFI and has been used as starting point for the the new U-THERM3D approach. The basic idea is a desynchronisation of time steps in the solution of the involved phenomena, that can be summarized in convection (including several sub-phenomena as combustion, spray evolution etc.), conduction in the solid and radiation. Each of them is solved in a dedicated simulation, running with a parallel coupling strategy. The procedure used in U-THERM3D is depicted in Figure 1. As far as radiation is concerned a steady solver is exploited because of the extremely small time scales. Convective and radiative wall heat fluxes are manipulated before sending them to the conduction solver. In addition to the three solvers, a dedicated tool for the calculation of effusion holes is coupled, relying on the imprinted technique as sketched in Figure 2.
Before testing the new methodology on the START full additive combustor, it was decided to prove and assess the U-THERM3D tool on two test cases: the AvioAero LEMCOTEC combustor and the DLR model combustor FIRST. Some details about LEMCOTEC combustor and its injection system are reported in Figure 3. An example of the results obtained by the investigation of an Approach operating condition is reported in Figures 4 and 5.
Central task of the project was the execution of the full annular test of the START combustor developed by AvioAero. Tests were carried out at the Sesta-Lab facilities of COSVIG. Besides the standard sensors installed on the test article by the Topic Manager, including a rotating probe for the exhaust gas analysis, UNIFI managed the adoption of an innovative type of thermal paints for metal temperature measurement. The Thermal History Coating THC paint developed by Sensor Coating System Ltd (SCS) was considered for the outer liner. The innovative THC provided by SCS permits a much higher accuracy in the measurement (below 2°C), with a pointwise description of the temperature over the painting. The use of a plasma sprayed coating also allow to have a higher resistance in the harsh environment of the full-scale combustion tests. Figure 6 reports a picture of the combustor liner painted the innovative THC and with the standard thermal paints.
Once raw data of the tests have been delivered to the Topic Manager, including the post-processing of the metal temperature carried out by SCS on the THC, activity of data analysis and further post-processing by UNIFI (Task 3.1) was carried out. As an example of the obtained results in terms of metal temperature, Figure 7 reports a picture of the sampled 300 points over combustor outer liner.
In Task 3.2 the developed U-THERM3D methodology has been applied to investigate the START combustor. In figure 8 a comparison of the predicted outlet temperature distribution with the measured data is reported, pointing out an excellent agreement. Figure 9 shows a comparison of the predicted and measured metal temperature. Also in this case a very good agreement is observed.
Concerning the dissemination, activities performed during the START project have been presented at some international workshops and conferences. The restrictions introduce worldwide due to the COVID-19 pandemic have greatly affected further contributions to public events such as the participations to Airshows as planned in the Annex I.
Three publications have been prepared and published by UNIFI regarding the development and validation steps of the U-THERM3D methodology.
Regarding the exploitation of the obtained results and knowledge, the following items can be summarized for the two partners. UNIFI: The most relevant outcome of UNIFI in the START project is the development of the U-THERM3D methodology and its validation. Currently, a License Agreement is under definition between UNIFI and AvioAero for the official release of the U-THERM3D methodology. The developed methodology will be used and further improved and validated in a new research program started on March 1st 2021 (project ACROSS, Euro-HPC). COSVIG: Concerning COSVIG, the main outcome from the START project is the further update of the test cell #2 at Sesta-Lab premises. The tests carried out during START project have permitted to define operations and control strategies optimized for small size combustors fed by liquid fuels which were not commonly investigated in the past at Sesta-Lab premises.
