Introduction to Marine Engineering potx

[...]... using a torsionmeter or with a brake The engine indicator An engine indicator is shown in Figure 2.8 It is made up of a small piston of known size which operates in a cylinder against a specially 16 Diesel engines Piston rod Calibrated spring Drum Linkage to provide straight line movement of stylus Piston Cylinder Indicator piston Section showing indicator piston ^vindicator cord —I Coupling *—' nut to. .. temperature) as the piston rises (Figure 2.1(b)) Fuel is injected as the piston reaches top dead centre and combustion takes place, producing very high pressure in the gases (Figure 2 l(c)) The piston is now forced down by these gases and at bottom dead centre the exhaust valve opens The final stroke is the exhausting of the burnt gases as the piston rises to top dead centre to complete the cycle (Figure... strokes of the piston, or two revolutions of the crankshaft In order to operate this cycle the engine requires a mechanism to open and close the inlet and exhaust valves Consider the piston at the top of its stroke, a position known as top dead centre (TDC) The inlet valve opens and fresh air is drawn in as the piston moves down (Figure 2.1 (a)) At the bottom of the stroke, i.e bottom dead centre (BDC),... Adjustments may then be made to the fuel supply in order to balance the cylinder loads Torsionmeter If the torque transmitted by a shaft is known, together with the angular velocity, then the power can be measured, i.e shaft power = torque x angular velocity The torque on a shaft can be found by measuring the shear stress or angle of twist with a torsionmeter A number of different types of torsionmeter are described... system Fuel injector HTuel pumps eated filter 22 Diesel engines After passing through centrifuges the cleaned, heated oil is pumped to a daily service tank From the daily service tank the oil flows through a three-way valve to a mixing tank A flow meter is fitted into the system to indicate fuel consumption Booster pumps are used to pump the oil through heaters and a viscosity regulator to the engine-driven... up, the ports at B are closed and the fuel is pressurised and delivered to the injector nozzle at very high pressure When the edge of the helix at C uncovers the spill port D pressure is lost and fuel delivery to the injector stops A non-return valve on the delivery side of the pump closes to stop fuel oil returning from the injector Fuel will again be drawn in on the plunger downstroke and the process... discharged into a manifold or rail which is maintained at high pressure From this common rail fuel is supplied to all the injectors in the various cylinders Between the rail and the injector or injectors for a particular cylinder is a timing valve which determines the timing and extent of fuel delivery Spill valves are connected to the manifold or rail to release excess pressure and accumulator bottles... cylinder and leaves at the top The outlet at the top of the cylinder may be ports or a large valve The process is shown in Figure 2.10(c) Each of the systems has various advantages and disadvantages Cross scavenging requires the fitting of a piston skirt to prevent air or exhaust gas escape when the piston is at the top of the stroke Loop scavenge Scavenge air in Opposed piston Tinir Exhaust valve Figure... port (Figure 2.3(b)) The burnt gases then begin to exhaust and the piston continues down until it opens the inlet or scavenge port (Figure 2.3(c)) Pressurised air then enters and drives out the remaining exhaust gas The piston, on its return stroke, closes the inlet and exhaust ports The air is then compressed as the piston moves to the top of its stroke to complete the cycle (Figure 2.3(d)) A timing... high-pressure fuel to their respective injectors The viscosity regulator controls the fuel oil temperature in order to provide the correct viscosity for combustion A pressure regulating valve ensures a constant-pressure supply to the engine-driven pumps, and a pre-warming bypass is used to heat up the fuel before starting the engine A diesel oil daily service tank may be installed and is connected to the system . alt="" Introduction to Marine Engineering This page intentionally left blank Second Edition Introduction to Marine Engineering D. A. Taylor, MSc, BSc, CENG, FIMarE, FRINA Marine . marine engineering 2nd ed. 1. Marine engineering I. Title 623.87 Library of Congress Cataloguing in Publication Data Taylor, D. A. Introduction to marine engineering/ D. A. Taylor. . blank As an introduction to marine engineering, we might reasonably begin by taking an overall look at the ship. The various duties of a marine engineer all relate to the operation