Design and Simulation of Two Stroke Engines

Design and Simulation of Two-Stroke Engines
Plate 7.2 The spray pattern from the TH Zwickau ram-tuned liquid fuel injection system.
Its utilization in a QUB research engine is described by Carson et al. [7.28] and the test
results of its behavior at light load and low speed are discussed below and shown in Figs. 7.60
to 7.63.
There is an alternative, and potentially simpler method of achieving the same hydraulic
ram effect, proposed by Heimberg [7.54].
Air-blast injection of gasoline fuel into the cylinder
This is actually the oldest technique for injecting fuel into diesel engines, employed by
Dr. Diesel no less [7.41], and was replaced (for compression-ignition engines) by the invention
of the jerk pump giving liquid injection at the turn of this century. In a form suitable for
the injection of gasoline into today's high-speed two-stroke engines, the system uses electromagnetic
solenoid-actuated poppet valves, although that too would appear to have a precursor
[7.42]. Landfahrer describes the inventive work of the research laboratory of AVL in this
arena [7.44].
The method of operation of a modern air-blast fuel injector is sketched in Fig. 7.50. The
injector is supplied with air at about 5 bar and liquid fuel at about 6 bar. The pressure difference
between the air and the fuel is carefully controlled so that any known physical movement
of the fuel needle would deliver a controlled quantity of fuel into the sac before final
injection. In Fig. 7.50(a) the injector is ready for operation. Both of the electromagnetic solenoids
are independently activated by a control system as part of the overall engine and vehicle
management system. The fuel solenoid is electronically activated for a knov» period of lift
and time, as seen in Fig. 7.50(b), the result being that a prec ,e quantity of fuel is metered into
the sac behind the main needle. The fuel needle is then closed by the solenoid, assisted by a
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