THE losses that occur in torque converters are of two types: flow losses and shock losses. The causes of these losses and how they are minimized in the polyphase converter are dis- cussed in this paper. O. K. KELLEY (M' 26) is in charge of Automatic Trans- mission Development of General Motors Central Engineer- ing. He has held this position since 1940. He served a year as assistant chief engineer of Detroit Transmission Division manufacturing the Hydra-Matic, before his ap- pointment to his present position.Polyphase THE efficiency of the hydrokinetic torque con- verter is the efficiency of its fluid flow-from pump to turbine to stator and back to the pump. The best efficiency results from getting the greatest weight of fluid through the path with the least amount of energy expenditure. Density and vis- cosity of the fluid are naturally important. The denser the fluid and the freer flowing the fluid, the better the efficiency. The only practical fluids for torque converters at the present time seem to be the petroleum oils, which leave quite a bit to be desired from both density and viscosity considerations. The torque converter designers can do nothing to improve this situation, beyond continuing to urge the oil and chemical industries to search for a more suitable fluid. The torque converter designers can merely analyze and learn to control the inevitable losses taking place in the flow of such liquids as have been made available to them. These losses can be grouped into two major categories: the flow losses and the shock losses. The flow losses are the minimum, unavoidable losses suffered through the path of the converter when all the blades are receiving the flow from the most efficient direction. These losses are due to the following: 1. Wall friction of the core and shell and both sides of all the blades contacting the flow. 2. Edge losses of the entrances and exits of all the blades. 3. Bend loss due to the circular path around the core ring. 4. Loading loss due to the specific curvature and the change in radius of the working blades.5. Expansion and contraction losses due to the change in cross-section of various flow channels. 6. Turbulence caused by cross-flows due to un- even blade loading. 7. Labyrinth leaks which short-circuit a part of the flow. 8. Cavitation losses due to inadequate charging pressure in the converter. For any given path design, the summation of all flow losses is in proportion to the square of the flow velocity. The shock losses, as the name implies, are the additional entrance losses suffered from a wrong angle of entrance in relation to the blades. All blade shapes receive the flow best in only one direc- tion. When this direction is deviated from, addi- tional losses result. These additional losses, re- ferred to as shock losses, deteriorate the efficiency of the converter very rapidly as they develop under the conditions of a radically wrong angle of en- trance. Like the flow losses, the shock losses are also proportional to the square of the flow velocity. Careful attention can be paid to the efficiency of the flow path to minimize the flow losses. We shall assume that in the following illustrations the flow losses have been designed to an irreducible point. The remaining losses then? left to consider are the shock losses as they form with the changing direction and velocity of the flow and the changing speed of rotation of the members. If we consider a simple, three-element converter as in Fig. 1, we can see the fundamental trend of the entrance shock losses and their importance relative to the flow loss. First, we note the gener- ally diminishing flow loss. This is due to the dimn- 138 SAE Quarterly TransactionsDownloaded from SAE International by Larry Glover, Saturday, November 24, 2018Torque Converter O. K. Kelley, Transmission Division, CMC This paper was presented at the SAE Summer Meeting, French Lick, Ind., June 4, 1951 ishing flow velocity as the turbine speed picks up and leaves