| SCREEN 1
Selections on this screen determine whether the engine is a recessed or flush face surface design, a 2 cycle or 4 cycle engine, and when a 2-cycle engine, whether it has 1 or 2 undulations (stations). Although the information is not used in this program version, partition framing in the annular cavity selection is possible. Partition framing in the cavity can significantly reduce partition mass in high compression engines.) SELECTIONS: i1) Select Engine design with a recessed face surface. Enter 1 i2) Select 2 cycle engine design. Enter 2 i3) Select 1 undulation (station) engine design. Enter 1 i4) Select partition framing in the cavity. Enter 1. (The resultant adjusted partition values shown at the end of this program section are not used further in this version.) |
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With the selections on this screen are determined whether the 2 cycle engine is a standard cycle type, selection 1 or a Very Low Pressure engine design, selections 2 through 9.
When the latter is selected, the ratio of variable volume to constant volume fuel injection is set along with the arc size between the intake and combustion region.
Unless fuel flame characteristics demand otherwise, choose one of the shorter intervals. (e.g. 6,7,8,9)
These selections reduce partition acceleration and combustion mass loss under constant volume (no work) conditions.
SELECTIONS:
i1) Select the shortest region. Enter 9
i2) Enter a serial number to help track data.
To this point we've selected a very low pressure engine design with 1 undulation and the shortest
available intake and fuel injection region.
Therefore, most injection occurs during VVV expansions; i.e. while the VVC are performing work.
We next -with reference to the design manual discussions- select the actual design dimensions of the
engine.
SELECTIONS:
i1) Enter the engine's major radius. Enter: 7" (Enter numbers without the dimension symbols.)
i2) Enter the partition's minimum radius in the annular cavity. Enter: 2"
i3) Enter the number of VVC (working chambers) in the engine. Enter: 8
i4) Enter the partitions' minimum angular extension into the VVC. Enter: 16°.
i5) Enter the partitions' maximum angular movement in the annular cavity. Enter: 20°.
i6) Enter the face surface angle. Enter: 135°.
Here the rotor has a 45° conic section like shape with the wave surface on its outer conic surface.
i7) Enter the partitions' maximum radius in the annular cavity. Enter: 7"
i8) Enter the partitions minimum thickness (at its very tip). Enter (x 1/31): 1
When the tapered partition design is selected later, this will be the partition thickness at the taper end.
Next displayed is the range of possible VVC volume ratios for the engine.
The value entered here closely determines the engine's expansion ratio.
To high a ratio here, and the engine dump pressure will be lower then atmospheric pressure and the program section 5FRASCA will abort.
To low a ratio, and an inefficient engine results.
Inherent with the low pressure in the VVC at the end of the combustion region (dump pressure) is quite engine operation.
Also displayed immediately below the input line for the VVC volume ratio are the engine SN and the partitions' actual minimum and maximum radii in the engine cavity.
i9) Enter the maximum to minimum volume ratio. Enter: 3
The program next generates and displays basic engine data.
The displayed information is generally self-explanatory.
The VVC volumes A(45) & A(46) are determined with partition thickness set to 0.
The adjusted VVC volumes A(41) & A(42) are determined with partition thickness set at their minimum thickness.
The engine intake per revolution utilizes the latter values.
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On this screen the partition material and pivot bearing information are selected.
i1) Partition material selections. Enter for SiC : 10
Silicon Carbide ceramic is the optimum chose here, given the lack of heat transfer programming.
It is very light and strong, and most importantly has excellent heat conductivity.
After a material is selected the screen displays its the physical properties which are used later in the programing to determine the partition's taper.
Although hydraulic bearings designs, with their minimal dimensional requirements, their high effectiveness with oscillating loads (squeeze load response) and their lubricants usability as a cooling medium are preferred,
the pivot bearing design for partition taper determination is comprised of a radial bearing at the partition pivot axis in a mating partition hole and co-axial thrust bearings flanking the partition sides.
i2) Enter a partition's pivot radial bearing outside radius. Enter .25"
i3) Enter a partition's thrust bearing outside radius. Enter 1"
i4) Enter a partition's thrust bearing load radius. Enter .9"
Further self explanatory engine dimension data is also then displayed.
SCREEN 4
On this screen the ambient air pressure and temperature are enter.
(where the engine operation is expected to occur.)
The screen then displays the intake temperature and pressure as if the engine had standard 2 cycle operation and gives a warning that purging is extant.
i1) Enter the ambient pressure. Enter (p.s.i.): 14.7
i2) Enter the ambient temperature. Enter (F°): 110
i3) Enter the ambient pressure as the intake pressure. Enter (p.s.i.): 14.7
i4) Enter the ambient temperature as the intake pressure. Enter (F°): 110
With the above information, the program generates & displays the thermodynamic properties of dry air at intake.
SCREEN 5
The program next generates and displays the thermodynamic properties of the VVC under the constant and variable volume conditions using the Sweigert & Beardsley equations to adjust the Specific heats increment by increment.
This data will next be used with the partition material characteristics acquired earlier in the program to determine the loads on the partitions and their subsequent required thickness and taper, or at the program users discretion the partition's through and through thickness.
SCREEN 6
This screen displays acquisition of the required partition thickness.
It then requires a response to the query whether the pseudo or actual area data should be used to determine the partition taper.
i1) For taper by Tmax (thickness) [L(12)] rather then L(11) enter 1. Enter 1.
The program then displays the partition stresses and the required partition taper angle in degrees and permits selection of the alternative constant thickness partition.
i2) For a constant thickness partition at approximately 5.4 x 1/32" enter 1. Press Enter.
Find below the data screen, SCREEN 7X, for an engine design without partition taper.
Now using the partitions new volume the program regenerates and displays for the last time the final dimensional properties.
Also displayed are the thermodynamic properties used in the the above determinations along with some non relative HT data.
We now select the flat partition rather then the tapered and generate a data set parallel to the topic VLP FRE for comparison.
Generally the flat partition design data will be on a green background and suffixed with an "X".
In the Very Low Pressure FRE, the flat partition engine design is the most effective design path.
When manufacturing cost and simplicity of construction are considered, the minor detriment to engine performance by using flat partitions is more then justified.
i1) For taper by Tmax (thickness) [L(12)] rather then L(11) enter 1. Enter 1.
i2) For a constant thickness partition at approximately 5.4 x 1/32" enter 1. Enter 1.
Note that in the case of the VLP FRE the displacement difference between the tapered and flat partition designs is minor.
The final engine dimensional data with flat partitions follows as:
