Facts about Wright turbo compound. It is incorrect and therefore not possible to compare the wright turbo compound (Exhaust blow-down turbine geared directly to the crankshaft through a fluid coupling) to a turbo-supercharger system. One part of the system used by F1 power unit.
The turbo-supercharger, like the blow-down turbine is an exhaust power recovery device. However, it has a different purpose that of allowing the engine to develop sea level power at high altitude. Therefore, it utilises a different method of performing this duty. In a turbo-supercharger installation, all cylinders exhaust into a common collector with two exit paths, one through a variable opening waste-gate, and the other through nozzles aimed at a turbine wheel. With the waste-gates fully open, there is no restriction, and collector pressure is nearly atmospheric. However, as the waste-gate is closed, pressure builds-up in the collector. The gas is forced through the nozzles, turning a turbine, which drives a supercharger. No power recovery is possible in such a system unless the collector is above exiting at atmospheric pressure.
The turbo-supercharger, therefore, utilises a ‘pressure’ turbine. It is basically different from a blow-down turbine since it converts blow-down velocity energy into pressure energy in a manifold collector. The conversion to pressure energy reflects on the scavenging ability of the cylinders.
The use of a pressure turbine to recover exhaust energy is quite inefficient, this is due to loss of basic engine power which accompanies the increase in exhaust system pressure. The increase of exhaust pressure also has an adverse effect on engine cooling and detonation margin.
The F1 additional system to the turbo-supercharging that of operating the supercharger in electric mode, called FREE LOAD MODE. Produces the maximum power output from the power unit. In this mode with ICE at full fuelling and with waste=gates fully open the supercharger is operated by the ‘H’ with the ‘H’ sharing battery power with the ‘K’.