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The net work produced is also represented by the area enclosed by the cycle on the p–V diagram. The net work is produced per cycle and is also called the useful work, as it can be turned to other useful types of energy and propel a vehicle (kinetic energy) or produce electrical energy. The summation of many such cycles per unit of time is ...
The net work equals the area inside because it is (a) the Riemann sum of work done on the substance due to expansion, minus (b) the work done to re-compress. Because the net variation in state properties during a thermodynamic cycle is zero, it forms a closed loop on a P-V diagram.
The efficiency of the Diesel cycle is dependent on r and γ like the Otto cycle, and also by the cutoff ratio, r c, which is the ratio of the cylinder volume at the beginning and end of the combustion process: [4] = () The Diesel cycle is less efficient than the Otto cycle when using the same compression ratio.
A key feature of the diagram is that the amount of energy expended or received by the system as work can be measured because the net work is represented by the area enclosed by the four lines. In the figure, the processes 1-2-3 produce a work output, but processes from 3-4-1 require a smaller energy input to return to the starting position ...
p–V diagram for the ideal diesel cycle. The cycle follows the numbers 1–4 in clockwise direction. Most truck and automotive diesel engines use a cycle reminiscent of a four-stroke cycle, but with temperature increase by compression causing ignition, rather than needing a separate ignition system. This variation is called the diesel cycle.
Expansion of working fluid takes place isentropically and work is done by the system on the piston. The volume ratio / is called the "isentropic expansion ratio". (For the Otto cycle is the same as the compression ratio /). Mechanically this is the expansion of the hot gaseous mixture in the cylinder known as expansion (power) stroke.
The timing of ceasing to inject fuel would then control power, also allowing enough time with the piston still descending in order to allow the work done on the piston during the expansion phase of the cycle to represent the output work of the engine. Thus Diesel's initial air blast slow-speed Diesel engine.
An indicator chart records the pressure in the cylinder versus the volume swept by the piston, throughout the two or four strokes of the piston which constitute the engine, or compressor, cycle. The indicator diagram is used to calculate the work done and the power produced in an engine cylinder [2] or used in a compressor cylinder.