HOMEWORK 1: Due date February 25th, 2015

1. A pickup truck has a five liter, V6, SI engine operating at 2400 rpm. The compression ratio is

10.2, the volumetric efficiency is 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/s)

c) Clearance volume (liter)

d) Air flow rate into engine (g/s)

2. A single cylinder four stroke cycle CI engine with 12.9 cm bore and 18 cm stroke, operating at

800 rpm, uses 0.113 kg of fuel in four minutes while developing a torque of 76 Nm.

Calculate: a) Brake specific fuel consumption (g/kW-h)

b) Brake mean effective pressure (kPa)

c) Brake power (kW)

d) Specific power (kW/cm2)

e) Output per displacement (kW/liter)

f) Specific volume (liter/kW)

3. Cylinder conditions at the start of combustion in an SI engine operating at WOT on an air

standard Otto cycle are 60 C and 98 kPa. The engine has a compression ratio of 9.5. Estimate the

heat input for the cycle if the fuel lower heating value is 40 MJ/kg and the AF = 15.5. (neglect

exhaust residual). Use the estimated heat input in air standart cycle calculations and

Calculate: a) Temperature at all states in the cycle (K)

b) Pressure at all states in the cycle (kPa)

c) Specific work done during power stroke (kJ/kg)

d) Heat added during combustion (kJ/kg)

e) Net specific work done (kJ/kg)

f) Indicated thermal efficiency (%)

4. Computer use:

Use the fuel air otto cycle applet which is available at

(http://www.wiley.com/college/mechs/ferguson356174/apps/otto/otto.html)

to study the change of imep, and ideal thermal efficiency with the equivalence ratio. Plot imep and ideal

thermal efficiency versus equivalence ratio for gasoline and diesel fuels. (select default values of the

applet for the other variables).