Fluid Flow 1 Turbine 2 Stator 3 Impeller When the engine is running, the rotating impeller acts as a centrifugal pump, picking up fluid at its centre and discharging fluid at high velocity through the blades on its outer rim. The design and shape of the outer row of blades and the impeller outer body cause the fluid to rotate in a clockwise direction as it leaves the impeller. This improves the efficiency of the fluid as it contacts the outer row of blades on the turbine. The centrifugal force of the fluid exiting the impeller outer blades is passed to the curved inner surface of the turbine via the outer row of blades. The velocity and clockwise rotation of the fluid causes the turbine to rotate. Turbine The turbine is similar in design to the impeller with a continuous row of blades. The fluid entering the tip of the blades is directed around the curved body of the turbine to the root of the blades. The curved surface of the turbine redirects the fluid back in the opposite direction to which it entered the turbine, increasing the turning force applied to the turbine from the impeller. This is known as torque multiplication. When the engine is idling, the impeller is rotating at a slow speed. The force of the fluid exiting the impeller does not have sufficient force to turn the turbine at high speed. In this condition the vehicle can be in gear without any forward or reverse motion being generated. When the engine speed increases, the turbine speed also increases. The fluid leaving the inner row of the turbine blades is rotated in an anticlockwise direction due to the curve of the turbine and the shape of the blades. The fluid is now flowing in the opposite direction to the engine rotation and therefore the impeller. If the fluid was allowed to hit the impeller in this condition, it would have the effect of applying a brake to the impeller, eliminating the torque multiplication effect. To prevent this, the stator is located between the impeller and the turbine. Stator The stator is mounted on the transmission shaft on a roller clutch. The stator comprises a number of blades which are aligned in an opposite direction to those of the impeller and the turbine. The main function of the stator is to redirect the fluid returning from the turbine, changing its direction of rotation to that of the impeller. The redirected fluid from the stator is directed at the inner row of blades of the impeller, assisting the engine in turning the impeller. This sequence increases the force of the fluid emitted from the impeller and thereby increasing the torque multiplication effect of the torque converter.
AUTOMATIC TRANSMISSION – GM 5L40-E DESCRIPTION AND OPERATION 44-1-17