Abstract
In this paper, we report the global fuel energy
consumption in heavy-duty road vehicles due to friction
in engines, transmissions, tires, auxiliary equipment,
and brakes. Four categories of vehicle, representing an
average of the global fleet of heavy vehicles, were
studied: single-unit trucks, truck and trailer
combinations, city buses, and coaches. Friction losses in
tribocontacts were estimated by drawing upon the
literature on prevailing contact mechanics and
lubrication mechanisms. Coefficients of friction in the
tribocontacts were estimated based on available
information in the literature for four cases: (1) the
average vehicle in use today, (2) a vehicle with today's
best commercial tribological technology, (3) a vehicle
with today's most advanced technology based upon recent
research and development, and (4) a vehicle with the best
futuristic technology forecasted in the next 12 years.
The following conclusions were reached: In heavy duty
vehicles, 33% of the fuel energy is used to overcome
friction in the engine, transmission, tires, auxiliary
equipment, and brakes. The parasitic frictional losses,
with braking friction excluded, are 26% of the fuel
energy. In total, 34% of the fuel energy is used to move
the vehicle.Worldwide, 180,000 million liters of fuel was
used in 2012 to overcome friction in heavy duty vehicles.
This equals 6.5 million TJ/a; hence, reduction in
frictional losses can provide significant benefits in
fuel economy. A reduction in friction results in a 2.5
times improvement in fuel economy, as exhaust and cooling
losses are reduced as well.Globally a single-unit truck
uses on average 1500 l of diesel fuel per year to
overcome friction losses; a truck and trailer
combination, 12,500 l; a city bus, 12,700 l; and a coach,
7100 l.By taking advantage of new technology for friction
reduction in heavy duty vehicles, friction losses could
be reduced by 14% in the short term (4 to 8 years) and by
37% in the long term (8 to 12 years). In the short term,
this would annually equal worldwide savings of 105,000
million euros, 75,000 million liters of diesel fuel, and
a CO2 emission reduction of 200 million tones. In the
long term, the annual benefit would be 280,000 million
euros, 200,000 million liters of fuel, and a CO2 emission
reduction of 530 million tonnes.Hybridization and
electrification are expected to penetrate only certain
niches of the heavy-duty vehicle sector. In the case of
city buses and delivery trucks, hybridization can cut
fuel consumption by 25% to 30%, but there is little to
gain in the case of coaches and long-haul trucks.
Downsizing the internal combustion engine and using
recuperative braking energy can also reduce friction
losses.Electrification is best suited for city buses and
delivery trucks. The energy used to overcome friction in
electric vehicles is estimated to be less than half of
that of conventional diesel vehicles. Potential new
remedies to reduce friction in heavy duty vehicles
include the use of advanced low-friction coatings and
surface texturing technology on sliding, rolling, and
reciprocating engine and transmission components, new
low-viscosity and low-shear lubricants and additives, and
new tire designs that reduce rolling friction.
Original language | English |
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Pages (from-to) | 94-114 |
Number of pages | 10 |
Journal | Tribology International |
Volume | 78 |
DOIs | |
Publication status | Published - 2014 |
MoE publication type | A1 Journal article-refereed |
Keywords
- buses
- friction
- energy
- trucks