Chapter 2 Operating Characteristics
Problems
2.1 As Becky was driving "Old Besty," the family station wagon, the engine finally
quit, being worn out after 171.00 miles. It can be assumed that the average
speed over its lifetime was 40 mph at an engine speed of 1700 RPM. The
engine is a five-liter V8 operating on a four-stroke cycle. Calculate:
(a) How many revolutions has the engine experienced?
(b) How many spark plug firings have occurred in the entire engine?
(c) How many intake strokes have occurred in one cylinder?
2.2 A four-cylinder, two-stroke cycle diesel engine with 10.9-cm bore and 12.6-
cm stroke produces 88 kW of brake power at 2000 RPM. Compression ratio, rc
=18.1. Calculate:
(a) Engine displacement. [cm3, L]
(b) Brake mean effective pressure. [kPa]
(c) Torque. [N-m]
(e) Clearance volume of one cylinder. [cm3]
2.3 A four-cylinder, 2.4-liter engine operates on a four-stroke cycle at 3200 RPM.
The compression ratio is 9.4:1, the connecting rod length r = 18 cm, and the
bore and stroke are related as S=1.06B. Calculate:
(a) Clearance volume of one cylinder in cm3, L, and in.3.
(b) Bore and stroke in cm and in.
(c) Average piston speed in m/sec and ft/sec
2.4 In Problem 2-3, what is the average piston speed and what is the piston speed
when the crank angle = 90 aTDC? [m/sec]
2.5 A five-cylinder, 3.5-liter SI engine operates on a four-stroke cycle at 2500
RPM. At this condition, the mechanical efficiency of indicated work are
produced each cycle in each cylinder. Calculate:
(a) Indicated mean effective pressure [kPa]
(b) Brake mean effective pressure [kPa]
(c) Friction mean effective pressure [kPa]
(d) Brake power in kW and hp.
(e) Torque. [N-m]
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Chapter 2 Operating Characteristics
2.6 The engine operating at the conditions in Problem 2-6 is square, with S = B.
Calculate:
(a) Specific power. [kW/cm2]
(b) Output per displacement. [kW/cm3]
(c) Specific volume. [cm3/kW]
(d) Power lost to friction in kW and hp.
2.7 The engine operating at the condition in Example Problem 24 has a combustion
efficiency of 97%. Calculate:
(a) Rate of unburned hydrocarbon fuel that is expelleded into the
exhaust system [kg/hr]
(b) Specific emission of HC. [(gm/kW-hr]
(c) Emission index of HC.
2.8 A construction vehicle has a diesel engine with eight cylinders of 5.375- inch
bore and 8.0- inch stroke, operating on a four-stroke cycle. It delivers 152-
shafthorsepower at 1000 RPM, with a mechanical efficiency of 0.60.
Calculate:
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(a) Total engine displacement. [in. ]
(b) Brake mean effective pressure. [psia]
(c) Torque at 1000 RPM. [lbf-ft]
(d) Indicated horsepower.
(e) Friction horsepower.
2.9 A 1500- cm 3 , four-stroke cycle, four-cylinder CI engine. Operating at 3000
RPM, produces 48 kW of brake power. Volumetric efficiency is 0.92 and air-
fuel ratio AF = 21:1. Calculate :
(a) Rate of air flow into engine.[kg/sec]
(b) Brake specific fuel consumption. [gm/kW/hr]
(c) Mass rate exhaust flow. [kg/hr]
(d) Brake output per displacement. [kW/L]
2.10 A pickup truck has a five-liter four-stroke cycle, V6, SI engine operating at
2400 RPM. The compression ratio rc = 10.2:1, the volumetric efficiency
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Chapter 2 Operating Characteristics
u = 0.91, and the bore and stroke are related as stroke S = 0.92 B.
Calculate:
(a) Stroke length. [cm]
(b) Average piston speed. [m/sec]
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(c) Clearance volume of one cylinder. [cm ]
(d) Air flow rate into engine. [kg/sec]
2.11 It takes a man 12.5 hours to complete a 500-mile trip in his automobile,
during which 18 gallons of gasoline are consumed. During this trip the
average Emission index for carbon monoxide is (EI)co = 28 (gm/sec)
/(kg/sec). Density of liquid gasoline is 0.692 kg/L. Calculate:
(a) Fuel economy in English units. [mpg]
(b) Fuel consumption rate using started SI units of L/100 km.
(c) Amount of CO emitted of environment during trip. [kg]
2.12 A 5.6-liter V10 compression- ignition truck engine operates on a four-stroke
cycle at 3600 RPM producing 162 kW of brake power. The bore and stroke
of the engine are related as s = 1.12 B. Calculate:
(a) Average piston speed. [m/sec]
(b) Torque. [N/m]
(c) Brake mean effective pressure. [kPa]
2.13 A 4.8-liter, spark-ignition, four-stroke cycle, V8 industrial engine operates
24 hours per day for five days at 2000 RPM using gasoline with AF =
14.6.the engine has a volumetric efficiency of 92%, with bore and stroke
related as B = 1.06 S. Calculate:
(a) Stroke length. [cm]
(b) Average piston speed. [m/sec]
(c) number of items each spark plug has fired.
(d) mass flow rate of air into engine. [kg/sec]
(e) mass flow rate of fuel into engine. [kg/sec]
2.14 A small single-cylinder, two-stroke cycle SI engines operates at 8000 RPM
with a volumetric efficiency of u = 0.85. the engine is square (bore =
011
Chapter 2 Operating Characteristics
stroke) and has a displacement of 6.28 cm 3 . the fuel-air ratio FA = 0.067.
Calculate:
(a) Average piston speed. [m/sec]
(b) Flow rate of air into engine. [kg/sec]
(c) Flow rate of fuel into engine. [kg/sec]
(d) fuel input for one cycle. [kg/cycle]
2.15 A single-cylinder, four-stroke cycle CI engine with 12.9-cm stroke, operating
at 800 RPM, uses 0.113 kg of fuel in four minutes while developing a torque
of 76 N-m. Calculate:
(a) Brake specific fuel consumption. [gm/kW-hr]
(b) Brake mean effective pressure. [kPa]
(c) Brake power.[kW]
(d) Specific power. [kW/cm 2 ]
(e) Output per displacement. [kW/L]
(f) Specific volume. [L/kW]
2.16 A 302-in.3 displacement, V8, four-stroke cycle SI engine mounted on a
hydraulic dynamometer has an output of 72 hp at 4050 RPM. Water absorbs
the energy output of the engine as it flows through the dynamometers at a
rate of 30 gallons per minute. The dynamometers has an efficiency of 93%
and the water enters at a temperature of 46F. Calculate:
(a) Exit temperature of the water. [F]
(b) Torque output of the engine at this condition. [lbf-ft]
(c) what is the bmep at this condition? [psia]
2.17 A 3.1-liter, four-cylinder, two-stroke cycle SI engine is mounted on an
electrical generator dynamometers. When the engine is running at 1200
RPM. Output from the 200-volt DC generator is 54.2 amps. The generator
has an efficiency of 87%. Calculate:
(a) Power output of the engine in kW and hp.
(b) Engine torque. [N-m]
(c) Engine bmep.[kPa]
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Chapter 2 Operating Characteristics
2.18 An SI, six-liter, V8 race car engine operates at WOT on a four-stroke cycle at
6000 RPM using stoichiometric nitro methane. Fuel enters the engine at a
rate of 0.198 kg/sec and combustion efficiency is 99%. Calculate:
(a) Volumetric efficiency of engine. [%]
(b) Flow rate o air into engine. [kg/sec]
(c) Heat added per cycle per cylinder. [kJ]
(d) Chemical energy from unburned fuel in the exhaust. [kW]
2.19 A large V8 SI four-stroke cycle engine with a displacement of 4.6 liters is
equipped with cylinder cutout. Which converts the engine to a 2.3 liter V4
when less power is needed. At a speed of 1750 RPM the engine, as a V8, has
a volumetric efficiency of 51%, a mechanical efficiency of 75%, an air-fuel
ratio of 14.5, and produces 32.4 kW of brake power using gasoline. With
cylinder cutout and operating at higher speed as a V4, the engine has a
volumetric efficiency of 86%, a mechanical efficiency of 87%, and uses an
air-fuel ratio of 18.2. Indicated thermal efficiency can be considered the
same at all speeds, and combustion efficiency is 100%. Calculate:
(a) Mass flow rate of air into V8 engine at 1750 RPM. [kg/sec]
(b) Mass flow rate of fuel into V8 engine at 1750 RPM [kg/sec]
(c) The bsfc as V8 at 1750 RPM. [gm/kW-hr]
(d) Engine speed needed as a V4 to produce same brake power
output. [RPM]
(e) The bsfc as V4 at higher speed. [gm/kW-hr]
2.20 A 1900-kg hybrid automobile which operates on ethanol fuel is equipped
with a multipurpose motor-generate-flywheel. When the vehicle slows or
stops,51% of the kinetic energy is recovered as electrical energy in the
battery. When the IC engine is used to recharge the battery there is a 24%
efficiency of converting chemical energy in the fuel to electrical energy
stored in the battery. The vehicle slows from 70 MPH to 20 MPH.
Calculate:
(a) Electrical energy recovered in battery [kJ]
(b) Mass of fuel needed to store same amount of energy in battery [kg].
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