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how to compare efficiencies for a diesel and a diesel-electric engine?

I have no idea how to possibly even begin interms of comparison. i know for a standard diesel engine i can just look at fuel efficiency and overall engine efficiency, but how would i do this for a diesel electric engine??


You need to identify and analyze each of the components in each system. The diesel drive system consists of the engine with its auxiliaries such as water pump, oil pump, starting system etc. plus the mechanical power transmission system. The transmission system would include the transmission and drive train components. The diesel-electric system consists of the engine and auxiliaries, a different set of mechanical drive train components, an electric generator, one or more electric motors and an electronic control system. Note that the electronic control system is a major item. All of the electrical power output of the generator passes through power conversion circuitry in the electronic control unit. The engine is likely to operate at different speed and torque operating points in each case. The diesel-electric system may utilize a narrower speed range and a wider torque range. If the diesel-electric system uses energy storage, there will be a battery charge/discharge control unit in addition to the other control units described. The system may operate with a smaller engine that operates mostly at a fixed speed and torque.
Dec 7, 2017
Very similar to comparing Apples to Oranges. Diesel Engine provides mechanical output. When connected to a Generator it becomes Diesel Electric with Electric out put. In terms of efficiency you rate the Diesel, the coupling and the Generator power factor to rate efficiency.
Dec 7, 2017
That is a good question! We do not want to make things to be too good, we after all live in a capitalistic society. If we wanted to make this very good we would have a 2 stroke diesel that runs on a mixture of 51% ethanol and 49% water with a caster oil lube. Then we could tune this engine to only run at a speed that is matched to the speed of a PM generator. Using this as the basis of the hybrid system. One gallon of ethanol makes almost 2 gallons of fuel. So right off the bat you would have double the fuel economy. Then another double for the hybrid system. Now you add a few PV panels to the roof so that your car will charge while you are in work. You might NEVER need to buy any fuel. But who is going to invest in a machine that does not make lots of money for somebody? After all we can not sell sunshine now can we. John.
Dec 7, 2017
Simple. You know the efficiency of the diesel. If you're going to add an electric drive, simply allow for the 10% or so losses in the in the generator - motor drive set vs. the smaller mechanical losses in a gear drive set.
Dec 7, 2017

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