Environmental Engineering Reference

In-Depth Information

Problem 8.4

A new sports utility vehicle averages 22 miles per gallon. It is expected to travel an average of

12,000 miles per year during a lifetime of 14 years. If fuel sells for $1.50 per gallon, calculate the

lifetime expenditure on fuel.

Problem 8.5

Using the data of Table 8.1 for the year 1995, calculate for each vehicle class its fraction of the

annual fuel consumed by transportation vehicles.

Problem 8.6

The engine power and size of a light duty vehicle is related to vehicle mass. For the vehicles

of Table 8.2, calculate the average values of power/displacement, power/mass, and displacement

per cylinder. Using these values, calculate the typical engine power, displacement, and number of

cylinders for a 2-ton vehicle.

Problem 8.7

A passenger vehicle diesel engine has a minimum brake specific fuel consumption of 0.22 kg/kWh.

Calculate its maximum thermal efficiency.

Problem 8.8

A 1.5-ton SI vehicle accelerates from rest to 100 km/h, then decelerates to a stop by braking. The

average vehicle speed during this cycle is 50 km/h, and the cycle lasts 30 seconds. (a) Calculate the

kinetic energy of the vehicle at its peak speed. (b) Calculate the time-average (W) and distance-

average (J/km) of the energy dissipated in braking. (c) If 25% of the fuel heating value (31.6 MJ/L)

is delivered to the wheels, calculate the average vehicle fuel economy in km/L for this start/stop

mode, neglecting everything but the dissipation of braking. Compare this with the highway fuel

economy of Table 8.2.

Problem 8.9

Motor vehicle manufacturers list the maximum torque as well as the maximum power of the vehicle

engine. Explain why the maximum torque has no direct influence on the vehicle performance.

Problem 8.10

A 1.5-ton vehicle has a frontal area of 2 m
2
, a rolling resistance coefficient of 0.1, and a drag

coefficient of 0.3. Calculate the mechanical power delivered to the wheels at steady vehicle speeds

of 50 and 100 km/h, if the atmospheric density is 1.2 kg/m
3
.