03-11-2015, 12:12 AM
John; you forgot steam engines...... then there are steam piston and steam turbines. Also; electric drives (diesel electrics, stepper, universal and induction motors.
In general; efficiencies rule the day when the customer and engineer are deciding what power plant to use. But other considerations can hold sway depending on the job and where the machine will be used. The military is less interested in efficiencies and more interested in winning the battle. Costs can take secondary importance to winning also. In general, efficiencies will reduce costs for a customer but high maintenance or difficulties in obtaining cheap fuel will guide power plant choices too. Large radial engines lost out to jets and turbines because they were more efficient to operate at high altitude, became much more reliable (cheaper to operate!) and longer times between major overhauls (cheaper to operate!) even though they are bloody more expensive to buy.
Gas engines work well in environments where speed is always changing (commuter cars) where diesel works best where speed is a steady state (boating, transports); mainly because of their efficiencies and the way they put power to final drive.
So when it comes to power plant choice there are many criterion that are taken into account; the order they are taken will depend upon the job and who is paying the bills.
In general; efficiencies rule the day when the customer and engineer are deciding what power plant to use. But other considerations can hold sway depending on the job and where the machine will be used. The military is less interested in efficiencies and more interested in winning the battle. Costs can take secondary importance to winning also. In general, efficiencies will reduce costs for a customer but high maintenance or difficulties in obtaining cheap fuel will guide power plant choices too. Large radial engines lost out to jets and turbines because they were more efficient to operate at high altitude, became much more reliable (cheaper to operate!) and longer times between major overhauls (cheaper to operate!) even though they are bloody more expensive to buy.
Gas engines work well in environments where speed is always changing (commuter cars) where diesel works best where speed is a steady state (boating, transports); mainly because of their efficiencies and the way they put power to final drive.
So when it comes to power plant choice there are many criterion that are taken into account; the order they are taken will depend upon the job and who is paying the bills.