OPA

Optimization of air jet pump design for acoustic application

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 Obiettivo del progetto (Objective)

'According to the call topic, the goal of the project is to optimize the design of a subsonic jet pump, to reduce as much as possible the noise level. The optimization of the subsonic jet pump will be done from the aerodynamic point of view and two type of analyses will be used, a RANS analysis as a “fast-screening” procedure to be able to identify using such techniques a trend in the flow behavior when performing a parameter study and a time dependent analysis with the more time-consuming but more accurate and more reliable, Large Eddy Simulation, for only the most promising or thought-provoking configurations. The acoustic treatment for further reducing the noise levels of the jet pump, in any configuration, is the application of noise treatment in the mixing part, and/or in the diffuser. From the acoustic treatment standpoint, there are two ways of attaching the noise reduction problem. First, the passive acoustic treatment, and second, which will be considered in the following, composed of resonant - absorbent structures. Tanking into consideration the aerodynamic optimization and the acoustic treatment a demonstrator with different configurations will be tested in the anechoic chamber where the velocity field and acoustics will be measured and compared with the numerical results.'

Introduzione (Teaser)

Jet pumps convert high-pressure air into a high-speed jet. Because manipulating air flow in aircraft creates noise, scientists are developing designs that reduce the acoustic emissions associated with subsonic jet pumps for air conditioning.

Descrizione progetto (Article)

Scientists launched the EU-funded project 'Optimization of air jet pump design for acoustic application' (OPA) to evaluate designs for low noise. The subsonic air jet pump for the air conditioning system must be located in close proximity to the passenger and crew cabins. Since noise is linked to hearing impairment, cardiovascular dysfunction, sleep disturbance and decreased mental function, noise reduction here is particularly important.

The team applied a fast-screening procedure for design concepts based on well-established Reynolds-averaged Navier-Stokes (RANS) equations. These time-averaged equations of motion for fluid flow are less time consuming and computation intensive than numerical methods for large eddy simulation (LES). The more accurate and more reliable LES is being employed for the most promising candidates.

Eight candidate solutions, one of which exploits well-studied fluidic injection for noise reduction, and a baseline configuration have been evaluated. All were evaluated using both RANS and LES methods except the one exploiting fluidic injection, which was studied only with LES. Based on the results of RANS and LES analyses, OPA scientists selected three designs and the baseline for further evaluation.

The baseline configuration has been manufactured and the three optimised solutions have been designed. In preparation for testing of the demonstrators, construction of the test rig has begun and the experimental test campaign has been defined.

Investigators are developing simulations of the unsteady regime of a simplified jet pump's operation. Outcomes will be compared to experimental data both to evaluate the performance of the test rig in producing accurate representations as well as to fine-tune the model for future development campaigns. The LES models have been completed and applied to several configurations. The fluidic injection design is particularly promising.

OPA is increasing knowledge regarding subsonic jet pump aerodynamics, noise propagation and reduction techniques through a combined numerical and experimental approach. Successful noise reduction will have important benefits for passengers, crew and manufacturers alike.