3.1.2 Cycle of a two-stroke DF engine in gas mode
The sequences of a two-stroke DF engine in gas mode are as follows (refer to Figure 3-2):
•
Sequence 1 - 2
The piston moves up and thus compresses the scavenge air. Gas is injected into the
combustion chamber. The temperature and the pressure of the gas-air mixture increase.
•
Sequence 2 - 3
At almost TDC a small quantity of pilot fuel is injected into the combustion chamber. The
gas-air mixture ignites and combustion starts.
•
Sequence 3 - 4
The gases expand and push the piston down. The pressure in the combustion chamber
decreases.
•
Sequence 4 - 1
The scavenge air replaces the exhaust gas as follows:
â—‹
At (4) the exhaust valve opens.
â—‹
At (a) the scavenge ports get uncovered. Scavenge air enters the cylinder and
pushes the exhaust gas into the exhaust gas manifold.
â—‹
At (b) the scavenge ports get covered.
â—‹
At (1) the exhaust valve closes.
The cycle is completed and starts again.
Fig 3-2 Pressure - volume diagram and schematic of the two-stroke otto cycle
X92DF
AA00-0000-00AAA-020B-A
Operation Manual Short description of the DF engine
Winterthur Gas & Diesel Ltd.
- 66 - Issue 002 2020-08