Power Plant Engineering

8.8.3 BRAKE HORSE POWER (B.H.P.)
Brake horse power is defined as the net power available at the crankshaft. It is found by measur-
ing the output torque with a dynamometer.
B.H.P. = 
2 NT
4500
Π
where
T = Torque in kg.m.
N = Speed in R.P.NT.
8.8.4 FRICTIONAL HORSE POWER (F.H.P.)
The difference of I.H.P. and B.H.P. is called F.H.P. It is utilized in overcoming frictional resist-
ance of rotating and sliding parts of the engine.
F.H.P. = I.H.P. – B.H.P.
8.8.5 INDICATED THERMAL EFFICIENCY (
ηηηηη
i
)
It is defined as the ratio of indicated work to thermal input.
η
i
= 
(I.H.P. 4500)
(W C
J)
v
×
×
×
where
W = Weight of fuel supplied in kg per minute.
C
V
= Calorific value of fuel oil in kcal/kg.
J = Joules equivalent = 427.
8.8.6 BRAKE THERMAL EFFICIENCY (OVERALL EFFICIENCY)
It is defined as the ratio of brake output to thermal input.
η
b
= 
(B.H.P. 4500)
(W C
J)
×
×
×
v
8.8.7 MECHANICAL EFFICIENCY (
ηηηηη
m
)
It is defined as the ratio of B.H.P. to L.H.P. Therefore,
η
m
= 
B.H.P.
L.H.P.

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DIESEL POWER PLANT
241
8.9 FUEL SYSTEM OF DIESEL POWER PLANT
The fuel is delivered to the plant by railroad tank car, by truck or by barge and tanker and stored
in the bulk storage situated outdoors for the sake of safety. From this main fuel tank, the fuel oil is
transferred to the daily consumption tank by a transfer pump through a filter. The capacity of the daily
consumption should be atleast the 8-hour requirement of the plant. This tank is located either above the
engine level so that the fuel flows by gravity to the injection pump or below the engine level and the fuel
oil is delivered to the injection pump by a transfer pump driven from the engine shaft, Fig. 8.3. Fuel
connection is normally used when tank-car siding or truck roadway is above tank level. If it is below
tank level, then, an unloading pump is used to transfer fuel form tank car to the storage tank (dotted line).
Foot Valve
and Strainer
Unloading
Pump
Sounding Well
Fill Connection
Manhole
Vent
Day Tank
To
Engine
Transfer
Pump
Strainer
Suction
Line
Crain
Tank
car
Fig. 8.3. Fuel System.
The five essential functions of a fuel injection system are:
1. To deliver oil from the storage to the fuel injector.
2. To raise the fuel pressure to the level required for atomization.
3. To measure and control the amount of fuel admitted in each cycle.
4. To control time of injection.
5.To spray fuel into the cylinder in atomized form for thorough mixing and burning.
The above functions can be achieved in a variety of ways. The following are the systems, which
are usual on power station diesels:
1.Common Rail.
2.Individual Pump Injection.
3. Distributor.