37
The most accurate method
of determining the power of
mechanical losses of the motor when it operates as a deacceleration
brake during braking is the method of turning the crankshaft of the
ICE by an electric motor on a special assembly shown in (Figure 3).
Figure 3 – Installation for determining the magnitude of mechanical
losses of ICE by crankshaft scrolling method using an electric motor
with visualization and registration of parameters: torque M
c
and
rotation speed n
e
.
At the stand, the dependence of the resistance torque of the
internal combustion engine on its shaft speed is obtained. The power
of mechanical losses of an internal combustion engine is calculated
by the formula:
9549
TD
e
M
M
n
N
(2)
where:
TD
M
– motor resistance torque (N.m);
M
N
– power of mechanical losses in the internal combustion
engine (kW);
e
n
– speed of motor’s shaft (rpm).
In Figure 4 presents the dependences of mechanical losses
power of gasoline engines VAZ-21124 and VAZ-21126 with
modernized piston on crankshaft speed [5].
38
Figure 4 – Power characteristics of mechanical losses of gasoline
engines: VAZ-21124 (upper curve) and VAZ-21126 9 with
modernized piston (lower curve 2).
Analysis of Figure 4, shows that the mechanical loss capacity
of
the piston motor is small, it is several times less than its power,
and it decreases rapidly when the motor shaft speed decreases, which
negatively affects the braking efficiency. By optimizing the piston
parameters, the mechanical losses of the internal combustion engine
are further reduced. This is the goal of almost all researchers of
combustion engines [5],[6],[7],[8],[9],[10], but to increase the
efficiency of engine braking, its mechanical losses should be
increased, but only during braking. So, it
is important to determine
the extent to which it is necessary to increase the power of the
engine's mechanical losses in order to ensure efficient service
braking of the car.
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