The report discloses thermodynamic studies of the semi-closed oxy-fuel combustion combined cycle. The computer simulation and parametric optimization approaches are described in details. The oxy-fuel cycle net efficiency in relationship to the carbon dioxide turbine exhaust pressure and the steam turbine inlet pressure is shown. The power production efficiency reduction is related to the turbine cooling losses is described. It is shown that the semi-closed oxy-fuel combustion cycle maximal net efficiency of 52.5% occurs at the initial temperature and pressure 1400°C and 60 bar at the carbon dioxide turbine exhaust pressure 0.5 bar and the steam turbine inlet pressure 90 bar. The cooling losses consideration leads to the net efficiency of 47.76% that is reached at the carbon dioxide turbine exhaust pressure 1 bar and the steam turbine inlet pressure 90 bar.
The present paper continues the investigation started in Part I. The basic turbine stage remains the same as in Part I (an axial turbine stage with axisymmetric nozzles and mean diameter 103.5 mm). The numerical simulation method used in Part I was corrected by adding analytical correlation for disc friction losses. This approach was validated on the base of the experimental data for a geometrically close turbine. Variation of the radial velocity component at the rotor inlet was proposed as a new modification compared with Part I. The mathematical formulations of the rotor blade sweep and radial velocity component at the rotor inlet were proposed. The new modifications of the baseline were provided to establish the effects of the rotor blade sweep, velocity radial component at the rotor inlet and hub endwall contouring separately. The using of backward swept rotor blades together with the positive cinematic lean provided efficiency increasing up to 2.9% at the design conditions. It was also established that absence of a velocity radial component at the rotor inlet in the model with backward swept blades leads decreasing of the turbine performance. Axisymmetric hub contouring provided up to 1.9% efficiency growth at the part-load operation.
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