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a. Reciprocating Cycles:
The air-standard cycles such as
the Otto cycle or the Diesel cycle used for modeling reciprocating engines (spark ignition
or compression ignition) are analyzed using the Closed-Process Cycle Daemons. A closed cycle is a sequence
of closed processes executed by a trapped gas, assumed uniform, in a piston
cylinder device; consequently, closed-cycle daemons build upon closed-process
daemons by adding a cycle panel, where results from the constituent processes
are integrated producing cycle-related variables such as the thermal efficiency or mean effective pressure.
If the details of the constituent processes are unimportant, an overall
analysis of a cycle can be carried out by the Closed-Steady daemon.
Closed-cycle daemons are located in Daemons. Systems. Closed. Process. Specific. ReciprocatingCycle page. As with most other daemons, the choice of working fluid is the last step in launching a particular daemon. While the PG or IG models are used mostly for Otto and Diesel cycles, a binary or even a general custom mixture can be formed (using IG/IG or n-IG models) as the working fluid. Use of H2O as the working fluid allows reciprocating steam engine to be analyzed. b. Process Panel: Image of the process panel for a closed-cycle daemon is shown in Fig. 1. Except for the schematic of the system, the equations and process variables are almost identical to the ones found in a closed-process daemon. The only other difference is having the boundary work W_B as the only means of work transfer for the processes making up the cycle. For most processes (isentropic, constant-pressure, constant-volume) W_B is automatically calculated if the anchor states are fully known. For polytropic processes, if any, the polytropic coefficient, n, can be entered in the process panels. The state panel is identical to the state panel found in the system state daemon since the anchor states of the constituent processes (strokes) are uniform system states (discussed in the Tutorial>Daemons> States>Manual chapter). After having the anchor states for each constituent
process evaluated, the processes are analyzed one by one (discussion can
be found in the Tutorial>Daemons>ClosedProcess>Manual chapter). |
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| Fig. 1 Image of the process panel in a Closed Cycle daemon. |
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c. The Cycle Analysis Panel:
Once all the processes making up
the cycles have been analyzed, all the cycle variables are automatically updated
in the cycle panel (see Fig. 2). The cycle must be complete, that is, the calculated
processes must form a loop (1-2, 2-3, 3-4, 4-1, for instance) for the cycle
variables to be evaluated.
In case of regenerative cycles such as the Starling cycle or the Ericson Cycle, the cycle panel allows the donor and receiver processes to be specified to indicate the regeneration direction. The only variables that can be entered in this panel is N, the number of cycles per sec. It relates the work produced per cycle to the power produced by the engine, Wdot. |
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| Fig. 2 Image of the Cycle panel in a Closed Cycle daemon. |
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d. Parametric Studies: Once a closed cycle has been set up, it is relatively simple to evaluate the effect of changing one or more variables. Simply change the independent variable, say the compression ratio, to a new value, Calculate and Super-Calculate . The states, processes and the cycle are all re-calculated with a detailed report, spreadsheet friendly table and TEST-codes generated in the I/O panel |
| Copyright 1998-: Subrata Bhattacharjee |