A trial to improve fuel-efficiency rates of a turbo-charged engine

The paper discusses theoretical bases and examples of practical application of the turbo-compound supercharging. The turbo-compound engines had been supposed to be used for propelling of buses, where it turned out that they were not fully meeting the expectations. This in particular applies to Volvo, where an axial-flow turbine was used as a power turbine. Such solution was given up in the construction of turbochargers for vehicles long time ago, for the benefit of turbines with radial flow (centripetal) due to much better dynamic rates of turbochargers with centripetal turbine and with centrifugal compressor. The solution with such turbocharger combined with the power axial-flow turbine impairs follow-up of the engine-turbocharger-power turbine set and hence the departure from such type of solution. As mentioned by the authors of the Volvo solution, it is much more suitable for aircraft engines (jet turbine engines) that operate at the maximum speed all the time, which is the most advantageous due to the efficiency of rotor machines. Application of the radial-flow turbine as a power turbine - as it is the case in the Scania engines -is much more advantageous solution. Results of simulation and operational tests of engines with such type of supercharging have been presented. A method of proceeding at determination of the engine operational parameters by means of simulation calculations has been described.