First I have to say Thank You to Ronald Fossum. Without his help the English speaking
world would have to wait for this English program version many years - and - I would be never ever
be able to translate it in this excellent way.
Originally I wanted a quick way to calculate the valve gear action for my
"Arkona" steam boat engine. Then I added a "Visualization" subroutine to the
program. Pictures and diagrams not only add clarity but -- particularly
if they're moving -- also increase interest in the function and performance
of steam machinery.
Insertion of engine particulars (length, radius, pressure, etc.) is done through
the individual windows. The basic unit of length or volume measurement throughout
the American translation of this program is the inch (You can change to
mm whenever you want). I and the program set up the appropriate geometrical mathematics. Below is a typical "input" window.
In the Main Window (seen below) are controls which immediately affect the computations and
influence the valve gear simulation. This is, as it were, the control station
of the engine. This is where certain data computations are displayed in
counters or registers. With this you influences also the animation of the control lever for instance - see animated picture at the right.
The graph below (one of three diaplays for valve movement) shows valve movement by angle of crank (0° is taken
at 12 o'clock and the degrees are numbered in a clockwise rotation. In America,
direction of rotation in marine engines is as viewed from the after end of the
engine, but you will have to look at the geometry of the engine--location of
reversing lever, movement of link, etc.--to decide if this is right for you.).
The four heavy horizontal black lines represent the edges of the valve face ports.
The upper two represent the port/passage at the top of the cylinder and the bottom
two, at the bottom of the cylinder.
The crank angle positions are noted in the horizontal plane. Here, vertical
lines denote the crank angle; from left to right: TDC (top dead center), 90°,
BDC (bottom dead center), 270°, and again top dead center.
The sine curves represent the position of the valve edges. Through these sine curves
one can easily see the amount a valve port is open at any crank position. The red
area represents steam admission and the blue, steam exhaust.
Here you can see, graphically, the resultant changes in steam flow -- and therefore
engine performance -- caused by variations in valve gear geometry, angle of advance,
and valve lap.
The Steam Diagram defines the potential output and efficiency of the engine. It displays measured and computed values and a theoretical card.
The values and the card are theoretical only. The actual (working) values are affected by many factors including (but, certainly, not limited to) the size of the engine. For example, if an engine is very small (like a model steamship engine) the proportionally large steam passages necessary for the model to work create clearance volumes well beyond acceptable practice.
However, the program calculated values given here, as well as the theoretical card, are a good starting point.
In the window Operating Parameters one inserts information about the pressures of the steam supplied to the engine -- and thereby directly affects the Steam Diagram. Here you will find all the information about steam consumption and output power of your engine.
If you like, you can download a free copy of the program here.