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Recent research activities in dynamic pressure metrology have been mainly focusing on the development of primary standards like the shock tube or drop-weight apparatus to establish traceability to SI. However, these calibration facilities require a high level of expertise leading to elaborate and time-consuming calibrations. The development of secondary calibrators, based on the reference sensor principle, offering efficient and cost-effective calibrations is essential to meet the needs for industry and to disseminate the dynamic pressure quantity to a wide end-user community. This paper reports a novel secondary calibrator for dynamic pressure measurements up to 300 bar with an expanded uncertainty of about 3.0 %. A heating option enable calibrations at elevated temperatures up to 200 °C making it an ideal solution for convenient calibrations of dynamic pressure transducers used for measurement in internal combustion engine applications.

Recent research activities in dynamic pressure metrology have been mainly focusing on the development of primary standards like the shock tube or drop-weight apparatus to establish traceability to SI. However, these calibration facilities require a high level of expertise leading to elaborate and time-consuming calibrations. The development of secondary calibrators, based on the reference sensor principle, offering efficient and cost-effective calibrations is essential to meet the needs for industry and to disseminate the dynamic pressure quantity to a wide end-user community. This paper reports a novel secondary calibrator for dynamic pressure measurements up to 300 bar with an expanded uncertainty of about 3.0 %. A heating option enable calibrations at elevated temperatures up to 200 °C making it an ideal solution for convenient calibrations of dynamic pressure transducers used for measurement in internal combustion engine applications.

The PRECCINSTA GTMC was studied at elevated pressure and power density with 6 kHz stereoscopic particle image velocimetry (SPIV), OH* chemiluminescence (CL), and 100 kHz dynamic pressure measurements. This technically premixed, swirl stabilized flame exhibited self-excited thermoacoustic oscillations with limit-cycle behavior. A helical precessing vortex core (PVC) was detected within the inner shear layer, between the central recirculation bubble (CRB) and the reactant jets. The PVC was found to be the delineating flow feature for combustion dynamics even at elevated pressure. Sparse dynamic mode decomposition (DMD) of the velocity fields deconvolved the dynamics into a thermoacoustic and PVC mode. The precession of the PVC was at a non-harmonic frequency to the thermoacoustic oscillations, and at least twice that of findings at atmospheric conditions. Nevertheless, the continuous and persistent structure of the PVC allows it promote unsteady heat release to sustain the thermoacoustic cycle. The three dimensional structure of the reactant jets, central recirculation bubble, and PVC was reconstructed by double phase conditioning the reconstructed velocity field. The surface of the CRB was observed to transition between asymmetric and symmetric states depending on the thermoacoustic phase. Analysis of the swirling strength values on the CRB surface indicates the interaction strength between the hydrodynamic structures of the PVC and CRB. When this coupling is large, the heat release determined by the mean OH*-CL intensity is maximum. These findings indicate a critical role of the PVC and CRB interaction on combustion in unstable swirl flames at conditions closer to those found in a modern gas turbine engine.