GATE 2007 AEROSPACE ENGINEERING (Q 51-60)

  1. The on-board motor of a satellite of initial mass 2000 kg provides a specific impulse of 280 seconds. If this motor is fired to give a speed increment of 500 m/s along the direction of motion, the mass of propellent consumed is:
    1. 685 kg
    2. 333 kg
    3. 1666 kg
    4. 167 kg

    Answer:-

  2. Combustion between fuel (octane) and oxidizer (air) occurs inside a combustor with the following stoichiometric chemical reaction:

    2C8H18 + (25O2 + 94N2) → 16CO2 + 18H2O + 94N2

    The atomic weights of carbon (C), hydrogen (H), oxygen (O) and nitrogen (N) are 12, 1, 16 and 14, respectively. If the combustion takes lace with the fuel to air ratio 0.028, then the equivalence ratio of the fuel-oxidizer mixture is

    1. 0.094
    2. 0.422
    3. 0.721
    4. 2.371

    Answer:-

  3. The von Mises yield criterion or the maximum distortion energy criterion for a plane stress problem with σ1 and σ2 as the principal stresses in the plane and σas the yield stress, requires
    1. σ12 − σ1σ2 + σ22 ≤ σy2
    2. |σ1 − σ2| ≤ σy
    3. |σ1| ≤ σy
    4. 2| ≤ σy

    Answer:-

  4. An Euler-Bernoulli beam having a rectangular cross-section, as shown in the figure, is subjected to a non-uniform bending moment along its length. Vz = dMy/dx. The shear stress distribution τxz across its cross-section is given by 
    1. τxz =
    2. τxz =
    3. τxz =
    4. τxz =

    Answer:-

  5. At a stationary point of a multi-variable function, which of the following is true?
    1. Curl of the function becomes unity
    2. Gradient of the function vanishes
    3. Divergence of the function vanishes
    4. Gradient of the function is maximum

    Answer:-

  6. In a rocket engine, the hot gas generated in the combustion chamber exits the nozzle with a mass flow rate 719 kg/s and velocity 1794 m/s. The area of the nozzle exit section is 0.635 m2. If the nozzle expansion is optimum, then the thrust produced by the engine is
    1. 811 kN
    2. 1290 kN
    3. 1354 kN
    4. 2172 kN

    Answer:- 1290 kN

  7. For the control volume shown in the figure below, the velocities are measured both at the upstream and the downstream ends.
    The flow of density ρ is incompressible, two dimensional and steady. The pressure is pover the entire surface of the control volume. The drag on the airfoil is given by

    1. ρU2h/3
    2. 0
    3. ρU2h/6
    4. 2ρU2h

    Answer:-

  8. A gas turbine engine operates with a constant area duct combustor with inlet and outlet stagnation temperatures 540 K and 1104 K respectively. Assume that the flow is one dimensional, incompressible and frictionless and that the heat addition is driving the flow inside the combustor. The pressure loss factor (stagnation pressure loss non-dimensionalized by the inlet dynamic pressure) of the combustor is
    1. 0
    2. 0.489
    3. 1.044
    4. 2.044

    Answer:-

  9. The diffuser of an airplane engine decelerates the airflow from the flight MAch number 0.85 to compressor inlet Mach number 0.38. Assume that the ratio of the specific heats is constant and equal to 1.4. If the diffuser pressure recovery ratio is 0.92, then the isentropic efficiency of the diffuser is
    1. 0.631
    2. 0.814
    3. 0.892
    4. 1.343

    Answer:- 0.814
    pressure recovery factor = p01 / p0a = 0.92




    Putting all the values, we have ηi = 0.814

  10. An airfoil section is known to generate lift when placed in a uniform stream of speed U at an incident α. A biplane consisting of two such sections of identical chord c, separated by a distance h is shown in the following figure:
    With regard to this biplane, which of the following statements is true?

    1. Both the airfoils experience an upwash and increased approach velocity.
    2. Both the airfoils experience a downwash and decreased approach velocity.
    3. Both the airfoils experience an upwash and airfoil A experiences a decreased approach velocity while airfoil B experiences an increased approach velocity.
    4. The incidence for the individual sections of the biplane are not altered

    Answer:-

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