Comparison of Different Small Steam Turbines for Steam Turbocharger

As a consequence of the high cost of energy, waste heat recovery schemes are becoming more attractive. One such scheme is a Rankine cycle utilizing steam as a working fluid and exhaust gases from petrol or diesel engine as a heat source. The turbine is connected with radial compressor to supercharge the engine. Turbines for this steam turbocharger in the range from 5 to 15 kW are not of the conventional type and require special design. To attain high cycle effeciency of the Rankine cycle for power systems of small capacity, the enthalpy drop should be as high as possible. This results in low mass flow rates obtained by the use of partial admission usually associated with low efficiencies. To avoid the use of partial admission, in the present work a simple Hero steam turbine with radial outward flow direction is used. Also some other designs are discussed and the efficiencies of these different types are compared. The choice of the main parameters of these turbines are very important in order to obtain the maximum possible efficiency. A method is presented for the analyses and design of simple construction.