Environmental Engineering Reference
In-Depth Information
usefully operate with a proper balance between the powers coming from both the
engines, which are typically regulated to optimize the performance of the IC
engine in terms of exhaust emissions and fuel economy. This mixed operation
strategy is typically managed to operate the IC engine in steady-state regime, i.e.,
in a high efficiency working point. In this case, if additional power is required, it
can be taken from the electric motor, while a possible surplus of energy produced
by the IC engine can be saved into batteries through the electric motor which in
this case operates as a generator. The IC engine can be turned off when the battery
is fully charged or when the total power required by the road mission is low,
because in that case the thermal engine has a very low efficiency.
The 'degree of hybridization' is a useful parameter characterizing parallel
hybrid vehicles. The value of this parameter is defined as the total power of the
electric motor divided by the sum of the total power of electric motor and IC
engine, according to the following equation:
total power of electric motor
total power of electric motor
þ
total power of IC engine
DOH
¼
A high value of the degree of hybridization means that the hybrid vehicle has a
small IC engine that operates at its maximum efficiency for most of its operation
time.
There is a large number of possible variations for the parallel hybrid configu-
ration, besides that shown in Fig.
5.18
, proposed by most of the major automobile
companies. Some of them, for example, have a small electric machine in line with
the crankshaft, where is usually located the flywheel in a IC engine vehicle.
Another parallel hybrid configuration has the IC engine and the electric drive
connected to different axles, as shown in Fig.
5.19
, in particular in this case the IC
engine drives the front wheels, the electric system the rear wheels and the road
Rechargeable
BATTERY
ELECTRIC
MOTOR
DC-AC
CONVERTER
TRASMISSION
Electric Drive
IC Engine
TANK
Fig. 5.18
Parallel hybrid configuration
