A main propulsion diesel engine is fitted with a pneumatically actuated governor, having an operating range of 10 to 60 psig. The current fuel rack setting is 15 mm at 30 psig. If the air pressure to the governor is increased to 40 psig, the fuel rack setting will change to __________.
ā¢ Linear relationship between governor control air pressure and fuel rack position over its operating range ā¢ How to find the slope (change in rack per psi) from the data given ā¢ Checking if the new pressure is higher or lower than the original, and what that does to fuel quantity
ā¢ What is the total pressure range of the governor, and how much of that range is being used in the example from 30 psig to 40 psig? ā¢ From the given rack setting at 30 psig, how can you estimate how much the rack would move for each 1 psi change, assuming a straight-line relationship? ā¢ If air pressure to this type of governor is increased, does that usually correspond to more or less fuel, and therefore a larger or smaller rack setting?
ā¢ Assume a proportional (linear) relationship unless the question states otherwise ā¢ Be sure you are measuring from the correct reference point in the pressure range (start of range vs. current operating point) ā¢ Confirm that your final rack value is reasonable in direction: should it be greater than, less than, or equal to 15 mm when pressure rises from 30 to 40 psig?
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