The oil platform construction support vessel to which you are assigned has main diesel engines fitted with intake and exhaust systems as shown in the illustration. If the main engine is running under a heavy load at maximum rpm, which pressure would ordinarily be negative? Illustration MO-0180
• Location of turbocharger blower wheel relative to the air intake and air box • How pressure changes across the blower/turbocharger and across the exhaust turbine at full load • Which parts of the system must be above atmospheric pressure to push air/exhaust through the engine
• Trace the flow of air from the atmosphere, through the intake, blower, intercooler, and into the air box. At which point does the air first become compressed above atmospheric pressure? • Trace the flow of exhaust gas from the cylinder to the exhaust receiver and then to the exhaust discharge/stack. Are these areas usually above, at, or below atmospheric pressure when the engine is working hard? • For a pressure to be negative (below atmospheric), would it be found before or after a driven compressor (blower)?
• Identify which components on the illustration are on the suction side of the blower and which are on the discharge side • Decide which spaces must have positive pressure to move gases through the engine (scavenging ports, exhaust receiver, stack) • Confirm that "negative" in this context means below atmospheric pressure, not just lower than another point in the system
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