25-Nav-B5 Marine Control Systems, December 2014: worked solutions

Paper format: National Examination 98-Mar-B5 Fluid Machinery, December 2014 — closed book, three hours, 60 marks. Section A is calculative (Q1–Q5) and Section B is descriptive (Q6–Q8); the rubric asks for four questions of Section A plus two of Section B (six questions, each of equal value, 10 marks). All eight questions are solved in full as a study resource. General constants supplied with the paper: g = 9.81 m/s², p_atm = 100 kPa, p_vapour = 2.34 kPa (20 °C), ρ_water = 1000 kg/m³, ρ_air = 1.21 kg/m³ (15 °C), c_p,air = 1.005, c_v,air = 0.718 kJ/kg·K.

Reference texts. S. L. Dixon & C. A. Hall, Fluid Mechanics and Thermodynamics of Turbomachinery (7th ed.); R. A. Sabersky, A. J. Acosta, E. G. Hauptmann & E. M. Gates, Fluid Flow: A First Course in Fluid Mechanics (4th ed.) — source of the pump-selection charts Figs 15.11/15.12; H. Cohen, G. F. C. Rogers & H. I. H. Saravanamuttoo, Gas Turbine Theory; R. W. Fox, A. T. McDonald & P. J. Pritchard, Introduction to Fluid Mechanics.

the same misfiling pattern already documented for other 98-Mar-coded papers in this discipline. It is solved here exactly as printed. Separately, Questions 3 relies on chart reads from the examination attachments (Figs 15.11 & 15.12); values read from those charts (φ_e, σ_c, η) are quoted to the precision the graphs allow and are flagged where used. The induction-motor pole count is not stated in Q3, so a standard 4-pole (1800 rev/min synchronous) machine is assumed — the governing method is unaffected.

25-Nav-B5 Marine Control Systems: December 2014