Cyclic Time Units

Cyclic Time Units are units of time where the time is specified as angular position with respect to a periodic rotation, such as a crankshaft. Cyclic Time Units are useful for specifying periodic events in simulations of reciprocating and electric machines.

At time t 0 = 0 , the cyclic time c 0 is equal to the specified starting offset:

Figure 1. EQUATION_DISPLAY
c i + 1 = ( c i + d t ⋅ r o t a t i o n _ r a t e ) mod ⁢   c y c l e _ l e n g t h ⁡
(15)

where d t = t i + 1 − t i , mod is the modulo operator, and cycle_length is the "Revolutions per Cycle" value in consistent units.

For example, if the starting offset is 0, d t is 15 min, and the rotation_rate is 6 deg/min, then:

c 1 = 0 + 15 * 6 = 90 deg.

So after 15 minutes the rotation would be 90 degrees.

Cyclic Time Units Properties

Units
Units used to represent and specify angular position.
Rotation Rate
Speed of the rotation in the chosen unit. For engine crankshafts the unit is typically rpm (revolutions per minute).
Starting Offset
The range of the periodic cycle is from the Starting Offset (inclusive) to the (Starting Offset + 360*Revolutions per Cycle) in degrees (exclusive).
Revolutions per Cycle

The number of 360 degrees revolutions in the cycle—usually given as an integer.

For example, for a 2 stroke engine, a cycle is 360 degrees, hence Revolutions per Cycle should be specified as 1.0. For a 4 stroke engine, a cycle is 720 degrees, thus Revolutions per Cycle should be set as 2.0.