Design and Stress Analysis of Extraterrestrial ... - The Black Vault

The transition from the oversaturated state of the working
medium to equilibrium is accompanied by a reduction in the efficiency
of the turbine. Since the size of the heat exchangers which ensure
heat transfer into the system increases in inverse proportion to
the efficiency of the turbine, the consideration of the supersaturation
processes makes it possible to create lighter structures as a whole.
The extraneous particles in the working medium are the condensation
nuclei. Therefore, working media used in such a device must
have a minimum of such particles. Condensation is the consequence
of the equilibrium expansion of any saturated vapor. It gives rise
to a reduction in turbine efficiency and causes the erosion of
blades and other structural elements. Erosion is caused by the
collision of the slowly moving film of condensed fluid and separate
drops of it wtth the rapidly moving parts of the rotor. Experience
shows that in order for erosion to occur, the quantity of liquid
phase of the working medium in the turbine should not exceed 10-12% and
circular velocity of the blades must not .xceed 275 m/s [51]. High
speeds are permissible only in turbines with the additional heating
of vapor between the stages of the turbine. In this case, the
vapor remains dry. However, intermediate heating necessitates an
increase in dimensions and weight of the steam generator and radiator.
The use of even one or two stages of vapor reheating complicates
construction and increases turbine weight. Therefore, the superheating
of steam can be recommended only as an extreme measure.
Some features of electric generators
Electric generators for extraterrestrial powier units, as a rule,
are mounted on one shaft with the turbine (i.e., without reducing
gear) and have high speed - 20,000 r/min and above (speed is limited
by the maximum possible speed from the point of view of strength
and by the circular velocity on the ends of the working blades).
Approximately 5 to 20% of the power supply to the generator
goes into the heating of the parts of the generator (the winding
of the rotor and the stator, etc.). To remove heat from the generator
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