Inlet Swirl Flow Research Articles

Nonaxisymmetric instabilities in a dump combustor with a swirling inlet flow

A series of experiments was conducted to explore large-scale oscillations observed in a dump combustor with a swirling inlet flow. Inlets with different swirl profiles, namely constant angle, forced vortex, and free vortex, were used in these experiments. Three levels of swirl strength for the constant-angle swirl profile case and one swirl strength for the two other cases were tested. Well-organized large-scale oscillations were observed in all cases. Spatial correlation and phase measurements clearly identified different modes of nonaxisymmetric instabilities as the source of these energetic oscillations. The results also showed that swirl profile has as much effect as swirl strength on the combustor flowfield characteristics.

Experimental study of isothermal swirling flows in a dump combustor

Detailed mean and turbulence data were obtained in a dump combustor with and without swirling inlet flow. A two-component LDV was used, and large samples were collected to resolve the second- and third-order correlations of velocity fluctuations with good accuracy. Large-amplitude well-organized oscillations were observed in the swirling flows and discussed. The swirling flows with and without vortex breakdown exhibited significantly different mean flow and turbulence field behavior.

A Method for Predicting Annular Diffuser Performance with Swirling Inlet Flow

A method for predicting the performance of annular diffusere with swirled flow at inlet is presented. The method is based on the assumptions of one-dimensional potential flow using a frictional coefficient parameter to account for friction losses. Theoretical predictions are in good agreement with available experimental data for a variety of annular diffuser geometries. In addition a computer program has been developed, allowing the present analytical technique to be readily applied to the design of any annular diffuser with swirled flow at inlet.

Optimum Strut-Configuration for Downstream Annular Diffusers With Variable Swirling Inlet Flow

Using three conical wall annular diffusers, geometries of struts mounted at the inlet tube were studied which were suitable for both the swirling inlet flow and the nonswirling inlet flow. Struts with an airfoil section which were installed at a small stagger angle served as a decelerating cascade for the swirling inlet flow, and a pressure rise was achieved across the struts. Furthermore, the residual weak swirl behind the struts improved the performance of downstream diffusers. For nonswirling inlet flow the struts induced a weak swirl which improved the performance of the diffuser. That is, if struts are designed properly, the performance of annular diffusers is improved by struts for a wide variation of swirl angle of inlet flow.

Novel Ball Type Fluid Components

A unique fluid oscillator and a timed valve have been designed and they both incorporate a ball in a simple cone-shaped cavity. The design of the fluid oscillator is based on the fluid dynamic force and inertia effect of the fluid in the discharge tube. The general form of the oscillator consists of a cone-shaped chamber having a fluid inlet from the top and two outlet discharge tubes from the bottom. A ball is placed inside the chamber controlling the water discharge through these tubes. A wide range of frequencies can be obtained by simply varying the outlet tube diameter and length. An analytical model has been developed using momentum exchange analysis and the results substantiated by experimental data. The operating principle of the timed valve is based on the vortex flow phenomenon. The vortex timed valve consists of a cone-shaped cavity with tangential inlet and a ball seating above a central exit port. In operation, the ball is first pushed away from its seating position and the time interval in which the ball will again move back to its original position is dependent on the inlet swirl flow condition.

Effects of swirling inlet flow on pressure recovery in conical diffusers

An experimental investigation was conducted to determine the effect of swirling inlet flow on the performance and outlet flow profile of conical diffusers. Twenty four different diffusers were tested, with total divergence angles ranging from 4.0 to 31.2°, and with area ratios from 1.30 to 8.27. The effect of swirling inlet flow on diffuser performance was found to be a strong function of flow regime in the same diffuser with axial inlet flow. Swirling inlet flow did not affect performance of diffusers which were unseparated or only slightly separated with axial inlet flow. For diffusers which were moderately or badly separated for axial inlet flow, swirling inlet flow caused large performance increases based on total inlet kinetic energy. The results indicate that optimum diffuser performance for swirling inlet flow may be higher than that for axial inlet flow. However, the geometry of the optimum diffuser will differ considerably from that for axial inlet flow. New optimums are presented for the three swirl ratios investigated.