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Comparison of Liąuid Propellant Rocket Engine Feed Systems - 1 - 12

Finally, combining the above expressions with 2.2.1 the gas generator mass can be obtained:

2o-,

(2.7.5)

where p_lgg is the gas generador wali materiał density (kg/m³).

2.8. Turbinę mass

To estimate this mass, it is followed the same argumentation as for the electric motor, changing only for the right values. So, the finał expression becomes:

Pcⁿ

*mt

(2.8.1)

where S_lu is the turbinę power density (W/kg).

As for the electric motor case, a similar expression can be obtained in the case when separated turbines for each pump are considered.

2.9. Propellant mass consumed by the turbinę

The propellant bumed by the gas generator is used to drive the turbinę, and conseąuently, it must be included in the estimation of the turbo-pump total mass.

The pump power can be related to the one required by the turbinę, through the pump and turbinę efficiencies, as shown in the following expressions:

pu

(2.9.1)

(2.9.2) where, Turbinę efficiency.

Pn_u: Turbinę inlet power (W).

Pot,,: Turbinę outlet power (W).

As the power consumed by the turbinę is due to the thermal expansion of the GG gases inside the turbinę, the following expression may be proposed:

P_ilu

(2.9.3)

being v_gg the velocity of the gases that impels the turbinę (m/s).

Assuming an isentropic gas expansion inside the turbinę, the velocity of the gases passing through can be expressed as: