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Railways NTPC (Technical Ability) Turbomachinery Question Bank Turbomachinery

  • question_answer
    In an axial flow gas turbine, the hot gases approach the rotor inlet with an absolute velocity of 600 m/s in a direction \[30{}^\circ \] from the wheel tangent. The gases leave the rotor axially. If the blade speed is 300 m/s, then the theoretical power output per kg/s of gas flow will be approximately:

    A) 132 kW            

    B) 156 kW

    C) 172 kW            

    D) 205 kW.

    Correct Answer: D

    Solution :

    \[{{v}_{w\,1}}=v{{a}_{1}}\,\,\cos {{\alpha }_{1}}=600\,\cos 30{}^\circ =519.615\,\,\text{m/s}\] \[{{v}_{w\,2}}=0,\,\,u=300\,\,\text{m/s}\] Power output per kg/s of gas flow, \[P=\frac{{{v}_{w\,1}}\times u}{{{10}^{3}}}=\frac{519.615\times 300}{{{10}^{3}}}=155.9=156\,\,k\,W\]


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