Truck & Off-Highway Engineering – June 2019

TECHNICAL

INNOVATIONS

6 June 2019 TRUCK & OFF-HIGHWAY ENGINEERING

SAE INTERNATIONAL

BOARD OF DIRECTORS

Paul Mascarenas, OBE

President

Mircea Gradu, PhD

2018 President

Todd Zarfos

2020 President Elect

Pascal Joly

Vice President – Aerospace

Ken Washington, PhD

Vice President – Automotive

Landon Sproull

Vice President –

Commercial Vehicle

Pierre Alegre

Treasurer

David L. Schutt, PhD

Chief Executive Officer

Gregory L. Bradley, Esq.

Secretary

Donald Nilson

Jeff Varick

Rhonda Walthall

SAE International Sections

SAE International Sections are local

units comprised of 100 or more SAE

International Members in a defined

technical or geographic area. The purpose

of local Sections is to meet the technical,

developmental, and personal needs of the

SAE Members in a given area. For more

information, please visit sae.org/sections

or contact SAE Member Relations Specialist

Abby Hartman at [email protected].

SAE International

Collegiate Chapters

Collegiate Chapters are a way for SAE

International Student Members to get

together on their campus and develop

skills in a student-run and -elected

environment. Student Members are vital

to the continued success and future of

SAE. While your course work teaches

you the engineering knowledge you

need, participation in your SAE Collegiate

Chapter can develop or enhance other

important skills, including leadership,

time management, project management,

communications, organization, planning,

delegation, budgeting, and finance. For

more information, please visit students.

sae.org/chapters/collegiate/ or contact

SAE Member Relations Specialist Abby

Hartman at [email protected]. DANFOSS POWER SOLUTIONS

THERMAL MANAGEMENT

Achieving better power management by optimizing

thermal management

Four primary power transmission subsystems
work together in a wheel loader: the transmission
system, the work functions system, the steering
system, and the thermal management system.
Optimizing any one of these without considering
how it impacts the rest of the machine design
can result in poor vehicle performance. On the
flip side, looking at the machine as one cohesive
system can result in true, overall optimization.
In particular, optimizing the thermal man-
agement system on a wheel loader—or any
piece of construction equipment—can posi-
tively impact power management.
Strategies developed by companies like
Danfoss Power Solutions can help address
many of the challenges facing machine design-
ers, including peak engine power, engine over-
speed and challenging ambient conditions.

Creating short windows of increased
power availability
During the dig cycle on a wheel loader, peak en-
gine power can be reached when filling the buck-
et. This means engine speed torque demanded
causes engine rpm to drop below an acceptable
level. Effective engine power management is key
to achieving operating efficiencies.
In these conditions, it can be particularly ad-
vantageous to utilize a variable ratio cooling fan
system. Utilizing the capabilities of such a system,
the cooling fan speed can be reduced signifi-
cantly (or even turned off) to partially offset the
effects of engine droop. As fan power is typically
about 10 to 15% of engine power, the increase in
available work power can be significant.
The challenge with this approach is the
charge air cooler (CAC) performance must be

maintained at all times. One method to accom-

plish this is by implementing a split cooling

system with two separate fan drives—one with

a larger fan responsible for the fluids (including

the hydraulic oil, radiator coolant, transmission

oil, etc.) and one with a smaller fan dedicated

to the charge air system. In times where peak

engine power may be reached, the machine

can be programmed to trim the larger fan sys-

tem while keeping the smaller system running,

effectively managing power, cooling demands,

and emissions compliance.

CAC cooling power is typically around 10% of

the liquids’ cooling fan power demands; most

of the total installed cooling fan power can be

saved. This means power needs are being man-

aged most efficiently during times when the

demands are highest. In addition, a smaller fan

drive provides the flexibility for consideration

of a hydraulic or electric drive solution.

Thermal mass, or the ability of a material to

absorb and store heat energy, enables this capa-

bility. The liquids in the first system typically

have a large thermal mass, therefore tempera-

ture changes typically occur over several sec-

onds (or minutes). The charge air system, on the

other hand, is a much more dynamic, faster re-

sponding system—meaning its cooling needs

cannot be suspended. Plus, changes in tempera-

ture in the charge air system directly correlate to

the ability to remain emissions-compliant. In

short, the liquids cooler can accommodate brief

periods of undercooling that the CAC cannot.

Our studies have shown liquids cooling sys-

tems can be suspended for up to a minute while

still maintaining the fluids’ temperatures within

acceptable working levels. This is well over the

Optimizing the thermal

management system on a

wheel loader—or any piece

of construction equipment—

can positively impact power

management.