Page 204 - Handbook of Energy Engineering Calculations

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where n = 0.5 r/min, ihp = (107)(18/12)(6) (π/4)(300/2)/33,000 = 20.6 ihp
(15.4 kW) per cylinder. Since the engine has eight cylinders, total ihp = (8
cylinders) (20.6 ihp per cylinder) = 164.8 ihp (122.9 kW).

Related Calculations. Use this procedure for any reciprocating internal-
combustion engine using diesel oil, gasoline, kerosene, natural gas, liquefied-

petroleum gas, or similar fuel.

I-C ENGINE CHARACTERISTICS ANALYSES

What is the piston speed of an 18-in (45.7-cm) stroke 300 = r/min engine?
How much torque will this engine deliver when its output is 800 hp (596.8
kW)? What are the displacement per cylinder and the total displacement if the
engine has eight 12-in (30.5-cm) diameter cylinders? Determine the engine

compression ratio if the volume of the combustion chamber is 9 percent of
the piston displacement.

Calculation Procedure:

1. Compute the engine piston speed
For any reciprocating internal-combustion engine, piston speed = fpm =

2L(rpm), where L = piston stroke length, ft; rpm = crankshaft rotative speed,
r/min. Thus, for this engine, piston speed = 2(18/12)(300) = 9000 ft/min
(2743.2 m/min).

2. Determine the engine torque
For any reciprocating internal-combustion engine, T = 63,000 (bhp)/rpm,

where T = torque developed, in · lb; bhp = engine brake horsepower output;
rpm = crankshaft rotative speed, r/min. Or T = 63,000(800)/300 = 168,000 in
· lb (18.981 N · m).

Where a prony brake is used to measure engine torque, apply this relation:
T = (F − F )r, where F = brake scale force, lb, with engine operating; F =
b
o
o
b
brake scale force with engine stopped and brake loose on flywheel; r = brake
arm, in = distance from flywheel center to brake knife edge.