Iveco Marine Diesel Engines, Installation Handbook

Page: 11 / 132

MARCH 2004 INTRODUCTION
1.11
MARINE ENGINES INSTALLATION
The driving torque M depends on the power according to:
where:
• M : driving torque [Nm]
• n : rotation rpm [rad/sec] (1 rev per min = π /30 rad/sec)
• N : power [kW]
The formula shows that with equal power it is possible to install engines with high torque and low rota-
tion speeds or vice versa, low torque and high rotation speeds.
High rotation speeds can generate a high torque by means of a speed regulator.
Figure 2 shows how a revolution reduction ratio of 4:1, obtained by coupling the gear wheels with this
ratio, makes the output torque increase by the same value 4.
Power
The air and fuel intake inside the cylinders and then burnt during combustion produces the same
heat energy which, translated into pressure and force, passes to the crank mechanisms and then to
the engine flywheel in the form of mechanical energy, less thermo-dynamic and friction losses. Such
energy referred to the time unit is the power that can be generated by the engine and is expressed
by the formula:
where:
• M : driving torque [Nm]
• n : rotation rpm [rad/sec] (1 rev per min = π /30 rad/sec)
• N : power [kW]
Figure 3 illustrates the process which generates power as the product of the torque by the angle speed,
corresponding to the work of the time unit referred to the rotating motion.
In addition, we provide the following equivalences:
■
1 kW = 1.36 CV = 1.34 HP
■
1 CV = 0.986 HP (unit of British Std. and S.A.E).
Figure 2