ENGR217 2024 Q A2 (ENGR5002)

ENGR217 2024 Q A2Past paperOld spec ENGR2172:125 marks30 min

Answer all parts (a) - (c).

Formulas you may need

Continuity: $Q = v_1A_1 = v_2A_2$ (on the formula sheet)
Bernoulli: $\dfrac{p_1}{\rho g} + \dfrac{v_1^2}{2g} + z_1 = \dfrac{p_2}{\rho g} + \dfrac{v_2^2}{2g} + z_2$ (on the formula sheet)
Steady-flow momentum balance: $\sum F_{ext} = (\dot m v)_{out} - (\dot m v)_{in}$ (on the formula sheet)
Pump similarity (affinity) laws: $\dfrac{Q_2}{Q_1} = \dfrac{N_2}{N_1}\left(\dfrac{D_2}{D_1}\right)^3$ , $\dfrac{H_2}{H_1} = \left(\dfrac{N_2}{N_1}\right)^2\left(\dfrac{D_2}{D_1}\right)^2$ (learn this; printed on the 2024 data sheet, not on the current sheets)
Lift and drag: $F_L = C_L\,\tfrac{1}{2}\rho u^2 A$ , $F_D = C_D\,\tfrac{1}{2}\rho u^2 A$ (learn this)
Power to overcome drag: $P = F_D\,u$ (learn this)
Weight: $F_g = mg$ (on the formula sheet)

(a)
A nozzle and hose are attached to the ladder of a fire truck. What force is needed to hold a nozzle supplied by a 100 mm diameter hose with a pressure of 2800 kPa? The nozzle outlet diameter is 50 mm.
v_1 (hose) =m/s
v_2 (jet) =m/s
F (holding force) =kN
[10]
(b)
A manufacturer desires to triple both the discharge and head on a geometrically similar pump. Determine the change in rotational speed and diameter under the new conditions.
N2/N1 =-
D2/D1 =-
[10]2:2
(c)
An aircraft with a mass, including payload, of 1500 kg and density $0.45\ \mathrm{kg/m^3}$ is designed to cruise at a speed of 100 m/s. The effective wing area is approximately $20\ \mathrm{m^2}$ . Determine the lift coefficient and the power required by the aerofoil during cruising. Assume a conventional aerofoil having a drag coefficient $C_D$ of 0.0065.
C_L =-
P =kW
[5]Third