Water jet propulsion device

Abstract

A water jet propulsion device 10 for a water vehicle, such as a boat, is disclosed. The propulsion device 10 comprises a main duct 12 having a main inlet 14 that is arranged to be submerged in use and a main outlet 16 , an impeller 30 disposed within the main duct 12 between the main inlet 14 and the main outlet 16 , and at least one auxiliary duct 24 having an auxiliary inlet 26 that is arranged to be submerged in use and an auxiliary outlet 28 that opens into the main duct 12 upstream of the impeller 30.

1 . A water jet propulsion device for a water vehicle, comprising:
 a main duct having a main inlet that is arranged to be submerged in use and a main outlet;   an impeller disposed within the main duct between the main inlet and the main outlet; and   at least one auxiliary duct having an auxiliary inlet that is arranged to be submerged in use and an auxiliary outlet that opens into the main duct upstream of the impeller,   wherein a valve is disposed within at least one auxiliary duct.   
     
     
         2 . A water jet propulsion device according to  claim 1 , wherein there are a plurality of auxiliary ducts, each having an inlet that is arranged to be submerged in use and an outlet that opens into the main duct upstream of the impeller. 
     
     
         3 . A water jet propulsion device according to  claim 2 , wherein at least some of the plurality of auxiliary ducts are arranged side-by-side. 
     
     
         4 . A water jet propulsion device according to  claim 2 , wherein at least some of the plurality of auxiliary ducts are arranged downstream from one another. 
     
     
         5 . A water jet propulsion device according to  claim 1 , wherein at least part of the main duct is inclined. 
     
     
         6 . A water jet propulsion device according to  claim 5 , wherein the inclined main duct defines a main duct lip. 
     
     
         7 . A water jet propulsion device according to  claim 5 , wherein the or each auxiliary duct extends through the main duct lip. 
     
     
         8 . A water jet propulsion device according to  claim 1 , wherein the valve is a door disposed in the auxiliary duct and movable between at least a closed position in which the passage of fluid through the auxiliary duct is restricted and an open position. 
     
     
         9 . A water jet propulsion device according to  claim 8 , wherein the or each valve is a non-return valve. 
     
     
         10 . A water jet propulsion device according to  claim 9 , wherein the or each non-return valve only allows the flow of water into the main duct through the or each auxiliary duct. 
     
     
         11 . A water jet propulsion device according to  claim 8 , wherein the or each valve is arranged to open at a pre-determined pressure threshold. 
     
     
         12 . A water jet propulsion device according to  claim 11 , wherein the or each valve is spring loaded. 
     
     
         13 . A water jet propulsion device according to  claim 8 , wherein the or each valve can be selectively opened and/or closed. 
     
     
         14 . A water jet propulsion device according to  claim 8 , wherein the or each valve is arranged to be automatically opened and/or closed on the basis of a detected parameter. 
     
     
         15 . A water jet propulsion device according to  claim 8  comprising one or more auxiliary ducts which include a valve arranged to allow water to flow from the auxiliary duct outlet in the main duct to the auxiliary duct inlet.