Design and Simulation of Two Stroke Engines

Design and Simulation of Two-Stroke Engines
BORE,mm= 60
STR0KE,mm= 60
C0N-R0D,mm= 110
EXHAUST 0PENS,eatdc= 100
TRANSFER 0PENS,2atdc= 120
INLET 0PENS,2btdc= 65
TRAP COMPRESSION RATI0= 7
SQUISH CLEARANCE,mm= 1.5
WRIST PIN-CROWN,mm= 25
WRIST PIN-SKIRT,mm= 25
DEFLECTOR HEIGHT,mm= 18
SWEPT V0LUME,cm3= 169.6
TRAP 5WEPT V0LUHE,Cm3=l 1 1
CLEARANCE V0LUME,cm3= 18.5 165.0
Fig. 1.13 Example of a calculation from Prog. 1.3, QUB CROSS ENGINE DRAW.
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pression and expansion strokes, reducing both power output and fuel economy. Therefore, the
QUB-type engine has enhanced engine reliability and efficiency in this regard over the life
span of the power unit.
The data values used for the basic engine geometry in Figs. 1.10-1.13 are common for all
three program examples, so it is useful to compare the actual data output values for similarities
and differences. For example, it can be seen that the QUB cross-scavenged engine is
taller to the top of the deflector, yet is the same height to the top of the combustion chamber
as the loop-scavenged power unit. In a later chapter, Fig. 4.13 shows a series of engines which
are drawn to scale and the view expressed above can be seen to be accurate from that comparative
sketch. Indeed, it could be argued that a QUB deflector engine can be designed to be
a shorter engine overall than an equivalent loop-scavenged unit with the same bore, stroke
and rod lengths.
1.5 Definitions of thermodynamic terms used in connection with engine design and
testing
1.5.1 Scavenge ratio and delivery ratio
In Fig. 1.1(c), the cylinder has just experienced a scavenge process in which a mass of
fresh charge, mas, has been supplied through the crankcase from the atmosphere. By measuring
the atmospheric, i.e., the ambient pressure and temperature, pat and Tat, the air density
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