In a diesel engine, what determines its speed? I want to learn the main factors. For example, I think one factor is the amount of injected fuel, another factor is the torque demand.
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$\begingroup$ The governor... mechanical or computer control $\endgroup$– Solar MikeCommented Jun 24 at 15:41
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The two factors are 1) fuel flow rate which determines power output and 2) torque loading. The operator (or an automatic governor) modulates fuel flow rate to maintain desired operating speed as the torque load varies.
To help the engine manage widely varying torque loads, a multi-speed transmission is inserted between the engine and the load to exchange RPM for torque and vice versa, so the engine can be operated near its optimum RPM point for best power under all load conditions.
Note that a diesel engine has heavy-duty reciprocating components inside it to manage the high compression ratios typical for diesels. The mass of these oscillating components generates high dynamic loads which the engine must be stout enough to manage. Those loads grow quickly as the engine speed increases which means that diesel engines in practical use are RPM-limited so they do not self-destruct when run too fast. That means that you cannot extract more power from it simply by forcing more fuel through the engine to make it spin faster than its design limits: if you try, carnage and mayhem will result.
answered Jun 24 at 16:29