Forcing Pulsations by Means of a Siren for Gas Turbine Applications

Abstract

A siren is a robust fast-valve that generates effective flow pulsations and powerful noise levels under well-controlled conditions. It operates under the inlet flow conditions of a gas turbine combustor. Its principle is based on a sonic air jet periodically sheared by a cogged wheel rotating at a given speed. It is used as an alternative to loudspeakers in combustion laboratories when the use of these is made difficult by aggressive flow conditions, such as hot air under pressure, possibly containing impurities. It is also a serious candidate as an effective flow actuator to be deployed on power gas turbine fleets. The authors have gathered more than twenty years of knowledge on siren technology. This pulsator was originally developed for research on thermoacoustics. By scanning through a given frequency range, one detects the acoustic resonance of specific parts of the combustor assembly, or possibly triggers a combustion instability during a sensitivity analysis of a flame to small perturbations. In 2010, Giuliani et al. developed a novel siren model with the capacity to vary the amplitude of pulsation independently from the frequency. In this contribution, the physics, the metrics, and the resulting parameters of the pulsator are discussed. Technical solutions are unveiled about visiting large frequency ranges (currently 6 kHz) and achieving elevated pressure fluctuations (150 dB SPL proven, possibly up to 155 dB SPL) with a compact device. A multimodal excitation is available with this technology, one idea being to dissipate the acoustic energy on nearby peaks. The contribution ends with a summary of the applications performed so far and the perspective of an industrial application.

Prototyping and Study of Mesh Turbomachinery Based on the Euler Turbine

“…The kinetic energy of the working fluid flow at the turbine (6) converts into mechanical energy. The turbine ( 6) is connected to the DC generator (7), whose resistance varies using the adjustable resistor (10). Scales (9) and tachometer (8) are provided to measure torque on the generator shaft (7) and its rotation speed.…”

“…The turbine ( 6) is connected to the DC generator (7), whose resistance varies using the adjustable resistor (10). Scales (9) and tachometer (8) are provided to measure torque on the generator shaft (7) and its rotation speed. Working fluid after the turbine (6) enters the tank (12) through a liquid collecting device (11).…”

“…Through the electric drive (4), pump test sample (3) is driven and starts to pump the working fluid from the tank (2) to the measuring container (9). The body of electric drive (4) is installed on the bearing (5) fixed on frame (1), which makes it possible to measure torque upon readings of the scales (7). Pressure at inlet and outlet is determined upon readings of the pressure gauges (15,17).…”

“…The results of practical use of mesh channels are known in the development of lattice wings [3,4], heat exchangers [5][6][7], and ejectors for various purposes [8,9]. The maximum rigidity of the rotor structure is achieved with a minimum rotor mass using modern additive technologies [10][11][12].…”

“…The use of jet streams features flowing from unconventional nozzles makes it possible to meet a variety of requirements in the design of technological processes [7,25]. The use of a nozzle with a non-axisymmetric outlet section allows for a significant increase or decrease in the force impact on barriers [25].…”