Continuously Variable Ratio Transmissions for Single-Shaft Gas Turbines

The single-shaft gas turbine was combined with various CVR transmission. Of the three variants studied in detail—purely hydrostatic transmission, hydrostatic transmission with internal power splitting, and hydrodynamic transmission with variable pitch converter—the latter gives the best transmission efficiency. However, comparison with the two-shaft gas turbine shows quite clearly that in practically all cases a large part of the gain in efficiency achieved by increasing the process temperature to 1623 K is absorbed by the losses from the CVR transmissions. Because of the great significance attached today to fuel consumption, the combination of single-shaft gas turbine with CVR transmission—on the basis of these investigations—cannot be recommended. This statement would even apply if it was to be proved that the simple design of the single-shaft gas turbine alone permitted the use of ceramic material and thus the higher process temperatures. This is because the conditions along the traction resistance line for level ground have a much greater effect on everyday fuel consumption than the efficiency ratings at full load. The latter only has an effect during acceleration or when steep gradients are being negotiated.