While underway on a slow-speed propulsion diesel, the duty engineer is alerted to a high scavenging air temperature at one cylinder. Which of the following could be a possible cause?
• Scavenging air system operation and where temperature is measured • How combustion problems at one cylinder can affect scavenging air temperature locally • Difference between system-wide faults (common to all cylinders) and a fault at a single unit
• Ask yourself: if only ONE cylinder shows high scavenging air temperature, which problems would likely affect just that unit, not the whole engine? • Which options would normally cause a rise in temperature for ALL cylinders sharing the same air supply rather than just one? • How might hot combustion gases get into the scavenging space and raise its temperature locally?
• Check which options involve a common component (turbocharger, coolers) supplying all cylinders versus a local component (valves, piston area) at a single cylinder. • Verify whether a scavenge air box fire is a cause or a consequence of high temperature and poor combustion conditions. • Consider whether loss of after-cooler or scavenging cooler efficiency would realistically affect just one cylinder or the whole bank.
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