The average exhaust temperature of a two-stroke/cycle diesel engine with a turbine-driven supercharger is lower than a similar four-stroke/cycle diesel engine at equal loads because __________.
• two-stroke vs four-stroke scavenging process and how fresh air moves through the cylinder • effect of scavenging air on the hot exhaust gases in a turbocharged two-stroke engine • relationship (or lack of it) between RPM / M.E.P. and exhaust gas temperature
• In a two-stroke turbocharged diesel, what happens inside the cylinder when the scavenge ports open and air flows through—does this tend to heat or cool the gases leaving the cylinder? • Which choice directly mentions a process that can physically lower the temperature of the exhaust gas, rather than just describing speed or pressure differences? • Think about whether later exhaust opening would normally give the gases more time to get hot, or some mechanism to cool them before they leave.
• Identify which option involves direct contact of cooler air with hot exhaust gases inside the cylinder. • Ask: Does higher RPM by itself guarantee lower exhaust temperature, or could it even increase it? • Ask: Does higher M.E.P. (mean effective pressure) automatically make exhaust cooler, or is there a clearer cooling mechanism described in one option?
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