Short subsonic diffuser for large pressure ratios

Claim 1

In a longitudinal divergent fluid diffuser, comprising means for converting a portion of the kinetic energy of a high velocity moving fluid in said diffuser into a higher pressure upon deceleration of the fluid stream wherein the diffuser includes means for preventing boundary layer detachment of the moving fluid along the divergent wall of the diffuser by increasing the momentum of the boundary layer in a direction parallel to the direction of longitudinal fluid flow by injecting a continuous thin layer of fluid along the diffuser wall through a slot immediately upstream of each point where the boundary layer detachment is likely to occur, means for collecting a central core portion of the high pressure decelerated fluid stream flowing in the diffuser in a central core region, away from the disturbed fluid flow near the diffuser wall, where the stagnation pressure has a value higher than the terminal pressure at the outlet of the diffuser and means for feeding back the collected high pressure central core portion fluid to said means for preventing boundary layer detachment, and means for introducing a high velocity fluid with said kinetic energy to be converted into the diffuser.

Claim 11

A method for transforming a portion of the kinetic energy of a moving fluid into fluid pressure comprising the steps of providing a longitudinally divergent wall duct having a relatively wide angle diverging wall adjacent the fluid outlet of the duct for confining the high velocity moving fluid and converting a portion of the kinetic energy of the high velocity moving fluid in said duct to pressure by deceleration of the fluid stream in the duct, the angle of the divergent wall being selected for minimizing frictional losses and developing large pressure gradients along the wall thereby rendering it prone to boundary layer detachment, collecting a central core portion of the fluid in the duct in a region having a stagnation pressure exceeding the pressure at the fluid outlet, and introducing the collected core portion of the fluid at a plurality of longitudinally preselected and spaced apart locations along the diverging wall of the duct and in the direction of the moving fluid for mixing with the moving fluid as it moves therethrough for increasing the momentum of the boundary layer against the prevailing pressure gradient in the duct, each of said locations being selected in relationship to the other points whereby the boundary layer would otherwise tend to detach for preventing the detachment of the fluid boundary layer from the duct walls as it moves through the duct.

Claim 12

A method for transforming a portion of the kinetic energy of a moving fluid into fluid pressure comprising the steps of providing a longitudinally divergent wall duct having a relatively wide angle diverging wall adjacent the fluid outlet of the duct for confining the high velocity moving fluid and converting a portion of the kinetic energy of the high velocity moving fluid in said duct to pressure by deceleration of the fluid stream in the duct, the angle of the divergent wall being selected for minimizing frictional losses and developing large pressure gradients along the wall thereby rendering it prone to boundary layer detachment, collecting a central core portion of the fluid in the duct in a region having a stagnation pressure exceeding the pressure at the fluid outlet, and introducing the collected core portion of the fluid at a plurality of longitudinally preselected and spaced apart locations along the diverging wall of the duct and in the direction of the moving fluid for mixing with the moving fluid as it moves therethrough for increasing the momentum of the boundary layer against the prevailing pressure gradient in the duct, each of said locations being selected in relationship to the other points whereby the boundary layer would otherwise tend to detach for preventing the detachment of the fluid boundary layer from the duct walls as it moves through the duct.