Turbo-compound engine

In a turbo - compound engine is an internal combustion engine, in which the energy of the exhaust gases out through the turbine of a turbocharger utilized by a power turbine downstream. Upon opening of the exhaust valves, the exhaust gas has a higher pressure than the ambient air; with a non-turbocharged engine, this pressure escapes unused. In a turbo engine, part of this pressure gradient is used to drive a turbocharger compresses the air in the intake system of the engine with that energy. In a turbo - compound engine, the exhaust gas is expanded through another turbine, which transfers the energy to 30:1 on a mechanical or hydraulic transmission with a reduction ratio of about 20:1 on the crankshaft, which in optimum conditions of an increase in efficiency of the motor leads.

Benefits

A fuel savings can only be achieved if the turbocharger despite the power turbine, which reduces the pressure gradient for the turbocharger turbine can provide enough air for combustion and the charge exchange losses are not too high. Use a larger scale did not exist before, because only in small areas of engine map a consumption advantage over conventional turbo engines can be achieved and the turbo-compound technology is relatively expensive. The most effective can be turbo-compound systems used in machines for prolonged periods in constant high load ranges. A use as ship propulsion (eg Zvezda M520 ), as an aircraft engine or road trains makes more sense than a truck in regional traffic, which works with a focus power to 100 kW ( 136 hp ), large parts of its working life in partial load ranges. The reducing power consumption of a stationary compound machine compared to the pure turbocharged engine is under the most favorable conditions, about five to seven percent.

Application

One of the most famous examples is the Curtiss -Wright R -3350, which came to be incorporated in the military field in the bomber Boeing B-29 and reconnaissance aircraft Canadair CL -28 and the Lockheed Super Constellation passenger aircraft and Douglas DC-7. With it, the conventional piston aircraft engine went into its final stage of development.

For large ship propulsion MAN has developed a power turbine, which develops up to 4700 kW additional power. This drives the turbine via a transmission to a generator, which outputs the generated electrical energy either to the electrical system or to a propeller shaft coupled to the electric motor. Wherein up to ten percent increase in performance of the propulsion system is achieved.

In the truck sector, for example, Scania and Volvo put a turbo - compound technology.

Future

In hybrid - electric drive rises through the downsizing of internal combustion engine, the average power, which could be an interesting application of the turbo-compound engine, such as city buses or delivery vehicles arise here as well.

Alternatives

In addition to the mechanical coupling by the turbo compound turbine, a direct conversion of thermal energy from the exhaust gas into electric power is possible.