Hybrid internal combustion engine and air motor system and method
A hybrid internal combustion engine and air motor system is provided and includes at least one chamber having a drivable member and at least one intake valve and at least one exhaust valve, and a reservoir connected to the chamber through at least one of the intake valve and the exhaust valve. The system further comprises a computer configured to calculate air compressor efficiency during an air compressor mode of operation and select an intake and exhaust valve opening and closing timing sequence for maximizing air compressor efficiency and/or a computer configured to calculate air motor efficiency during an air motor mode of operation and select an intake and exhaust valve opening and closing timing sequence for maximizing air motor efficiency.
1. A method for operating a hybrid internal combustion engine and air motor system comprising at least one chamber having a drivable member and at least one intake valve and at least one exhaust valve, and a reservoir connected to the chamber through the exhaust valve, comprising:
in an air motor mode of operation, calculating air motor efficiency according to the following equation:
η
AM
=
efficiency
of
air
motor
=
-
ⅆ
W
ⅆ
A
and wherein
A
=
thermodynamic
availability
in
reservoir
=
(
E
-
E
o
)
+
P
o
*
(
V
-
V
o
)
-
T
o
*
(
S
-
S
o
)
dA=rate of change of A
E=Internal energy of air in reservoir=f(m, T t )
m=mass of air in reservoir=P t *V/(R*T t )
T t =Temperature of air in reservoir
P t =Pressure of air in reservoir
V=Volume of reservoir at P t and T t
R=gas constant
E o =Internal energy of air in reservoir at ambient pressure and temperature
P o =Ambient pressure
V=Volume of air in reservoir at ambient pressure and temperature
T o =Temperature of ambient air
S=Entropy of air in reservoir=f(P t , T t )
S o =Entropy of air in reservoir at ambient pressure and temperature
POW=Engine brake power=N*T b
N=Engine speed (rev/time)
T b =Engine brake torque
W=Engine brake work=POW dt
dW=rate of change of W
and
selecting an intake and exhaust valve opening and closing timing sequence for maximizing air motor efficiency so that
ⅆ
(
η
AM
)
ⅆ
(
Valve
Timing
)
=
0
and
ⅆ
2
(
η
AM
)
ⅆ
2
(
Valve
Timing
)
<
0.