Sankey diagram (engine)

A Sankey diagram is an energy flow chart whose arrow widths are proportional to the energy each path carries, used to show an engine heat balance. For a marine diesel it splits the fuel energy input, set to 100 percent, into brake power, around 45 to 50 percent on a modern two-stroke, and the loss streams: exhaust gas, jacket and charge-air cooling water, lubricating oil, and radiation. The widths make the recoverable waste heat visible, which sizes the exhaust gas economizer and any waste heat recovery turbine. The diagram is a teaching and design tool, not a measurement, built from a tested or specified energy balance.