In a medium-speed marine propulsion engine equipped with direct admission air starting valves, the cylinders without air starting valves fire first because the __________.
• air starting systems on medium-speed diesel engines • effect of starting air expansion on cylinder temperature and ignition • which cylinders receive fuel injection first during cranking
• Think about what happens to the temperature in a cylinder when high‑pressure air is admitted and allowed to expand during starting. • Consider which cylinders are more likely to reach the temperature needed for fuel ignition: those with cold metal surfaces or those that have not been cooled. • Ask yourself whether fuel admission is normally cut off to some cylinders during cranking, or if all cylinders are treated the same.
• Verify how direct admission air starting valves operate in medium‑speed propulsion engines. • Check whether compression pressure is higher in cylinders with or without starting air valves. • Confirm what effect the expansion of starting air has on cylinder liner and head temperature before normal firing begins.
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