Experimental investigation of the correlation between the dynamics of an impinging jet on a slotted plate and the acoustic field generated

In order to know the origin of the noise generation when an impinging jet hit a specific geometry, an experimental setup was used allowing the generation of the flow and the adjustments of its parameters (such as Reynolds number, confinement, alignment, etc…). The vortex dynamics in case of a high acoustic level for two different Reynolds numbers Re = 5684 and Re = 6214 are considered here. Indeed, many configurations allow self-sustaining sound loop to take place in confined spaces between the nozzle and the impinged surface. This feedback loop optimizes the energy transfer between the aerodynamic field and the acoustic field and creates a source of noise that can become very noisy. Thus, to control these phenomena, it is necessary to understand the aero-acoustic coupling in such configurations. As a result, we measured the 2C kinematic instantaneous fields (vx, vy) of the flow by the technique of Particle Image Velocimetry (PIV) with a sampling rate of 1 KHz and the acoustic field is obtained using a B&K Microphone. For the two considered Reynold numbers, we can distinguish two patterns for the vortices travelling from the nozzle toward the plate of impact.

Investigation of the pulsation-reduction characteristics of an expansion chamber attenuator in a hydraulic system

This paper investigates the expansion chamber attenuator utilized in marine hydraulic systems to determine the pulsation-reduction characteristics in hydraulic deck machinery applications. First, the background is briefly introduced. Next, the advantages and disadvantages of investigation methods borrowed from the aerodynamic field are discussed with regard to hydraulic use. Insertion loss is eventually selected to evaluate the performance of the attenuator. Finally, attenuator prototypes and a test rig that simulates an actual marine hydraulic system in a vessel are manufactured, and the experimental conditions are introduced in detail to calculate and measure the insertion loss. As indicated by the investigation conclusion, mathematic computation generally fits the test results. A better choice of length–diameter ratio ranges and other characteristics are discussed. This paper provides theoretical and experimental evidence regarding design expansion chamber attenuator use in hydraulic systems.

Study of Cold-State Aerodynamic Field Test on the Outlet of 2150t/h Supercritical Once-Through Boiler

The new unit putting into production is the supercritical boiler with a level of or above 600 MW, and most of them take the corner tangential combustion technology. The Long-term operation practice shows that there is gas temperature deviation on all the horizontal flues of boilers, which usually leads to the overheating tube burst of the high-temperature superheater and reheater, thus threats the safe and economic operation of power station. Towards the gas temperature deviation phenomenon that exists commonly in tangentially fired boiler, this paper went on the pertinent cold-state aerodynamic field test on the tangentially fired boilers in one new power plant and studied the airflow velocity at the furnace outlet in eight vertical levels by changing the SOFA horizontally rotating angle. The experiment showed that changing the baffles opening and horizontally rotating angle of SOFA air door could adjust airflow quite well and make it uniform, furthermore, the airflow can reach a basic balance at the biggest anti-tangential angle. This paper has some reference value towards improving the gas temperature deviation problem of tangentially fired boilers.

Comparison of Fluid-Structure Coupling Methods for Blade Forced Response Prediction

A time-marching coupled method has been applied to a high pressure compressor forced response case. The purpose of the study is to compare the contribution of the coupled scheme against the state of the art decoupled methodology. Although the time-marching scheme allows for a stronger coupling between the motion and aerodynamic field, results have shown good agreement with the decoupled method. The additional computing cost arising from the long transient state and the small difference in amplitude prediction with the decoupled scheme reduce the interest for the coupled one. A new transient state method is proposed to combine both coupled and decoupled schemes features. Here, the forcing and damping functions are extracted during the mechanical transient state of the coupled simulation and forced response is calculated as in the decoupled method. Results have shown good agreements with the experiment and all the methods are compared in terms of underlying assumptions and performances.

Effect of over-Fire Air Velocity on the Aerodynamic Characteristics in a Cold Model of an Arch-Fired Boiler with New over-Fire Air Arrangement

A new over-fire air (OFA) program is proposed for Foster Wheeler (FW) type arch-fired boiler: the OFA nozzles are setting on arches near the furnace center and emitting OFA flow into the furnace at an inclined angle. Cold airflow experiments were conducted to determine the effect of the OFA velocity on the aerodynamic field in a small-scale furnace modeled for a 660-MWe arch-fired boiler. As the OFA velocity increases, the penetration depth of the OFA flow increases and the turning point of the OFA flow moves to the furnace center. At the same time, the vertical velocity of arch-injected airflow reduced faster because of the attracted effect of the OFA flow with higher velocity. When the OFA velocity is 22.39m/s (corresponding to 30m/s in the actual boiler), the OFA flow could penetrate to the furnace center and mix with the upflowing gas completely, while the arch-injected airflow have sufficient travel distance and enough residence time in the lower furnace. Thus, considering the penetration depth of arch-injected flow and the OFA flow, an OFA velocity of 22.39m/s recommended according to the present work.