DIESEL ENGINE EMISSIONS LEGISLATION: THE ... - Sauer-Danfoss

Sauer-Danfoss Emissions Solutions
DIESEL ENGINE EMISSIONS LEGISLATION: THE IMPACT ON
HYDRAULIC CIRCUIT DESIGN CRITERIA
Rick Sporrer, Sales Quality and Technical Services Director, Sauer-Danfoss
August 26, 2009
The increasingly strict regulations on emissions from diesel engines are having an affect on the decision criteria vehicle design
engineers use when designing a hydraulic circuit. The increase in fuel prices and engine installation costs require the design
engineer to scrutinize circuit designs for optimum power utilization. In addition to key decisions on control systems, hydraulic
flow sources, and hydraulic actuators, the decision criteria used for hose and tubing selection must be re-examined as well.
Traditionally, the decision on hydraulic hose/tubing size and selection is dominated by the purchase costs of the material, and less
importance is given to power utilization and heat generation. Due to the purchase costs of the material, design engineers have
been encouraged to use the smallest-diameter, lowest-pressure rating material permitted by design guidelines. If the design
resulted in higher pressure losses and additional heat due hydraulic flow velocities, the lower cost of fuel and excess capacity in
vehicle cooling systems accommodated these design compromises.
With the phase-in of the fourth level of emissions standards (Tier IV/Stage IV) in 2011, additional criteria associated with
optimized power utilization and minimal heat generation must be considered.
Specialty Agricultural Harvester
A specialty agricultural harvester can serve as a case study of how
the new emissions regulations will impact the hydraulic circuit
selection process. This vehicle will have a variety of hydraulic
actuators (cylinders, harvesting motors, steering) and multiple
directional flow and pressure control valves located at various
points on the vehicle.
The harvesting head and crop handling system may be comprised
of a single hydraulic flow source, a directional flow control valve,
and multiple hydraulic motors.
The total length for all of the hydraulic hose/tubing installed on the vehicle for the harvesting head and crop handling hydraulic
system may exceed 76 meter (250 feet). When the vehicle is in harvesting mode, the hydraulic flow in this section of the system
may average 121 litres/minute (28 gallons/minute) and experience operating pressures of 275 bar (4000 psi).
The traditional selection criteria for the hydraulic hose/tubing connecting these various components would have been dominated
by two factors:
• Hydraulic flow velocities design guideline of 6 - 9 meter/second (20 – 30 feet/second)
• Lowest purchase cost for the material
Based on the conditions and these two criteria, the decision to use a 16 mm (0.625 inch) diameter hose could be predicted. This
decision would have resulted in an average fluid velocity of 8.8 meter/second (29 feet/second) and be supportive of the lowest
material purchase cost criteria.
The by-product of this decision would be a pressure loss due to viscosity (frictional loading between the hydraulic oil and hose)
of 68 bar (1000 psi) at these conditions. This equates to a non-value-added power load of 14 kW (19 hp) within the vehicle,
resulting in additional fuel usage, additional system heat, and additional engine exhaust emissions.
With the new emphasis on engine emissions, fuel usage, and total vehicle cost of ownership, the design engineer could consider
an alternative solution – using a 19 mm (0.75 inch) diameter hose. This decision would reduce the average fluid velocity to 6.4
meter/second (21 feet/second). The 27% reduction in fluid velocity would reduce the pressure losses by over 57%, generating a
pressure loss of 30 bar (420 psi). This pressure loss, then equates to a power loss due to fluid flow of 6 kW (8 hp) on the engine.
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Sauer-Danfoss Emissions Solutions
While the initial purchase cost increases (76 Euro, in the example below), this cost is more than offset by the reduction in annual
fuel usage (1200 Euro in the example):
Installed cost increases by
76 Euro
Annual fuel cost decreases
by over 1200 Euro
Perhaps most importantly, the design engineer now has an additional solution to offset the challenges (increased heat load,
reduced power available) presented with Tier IV/Stage IV compliant diesel engines.
Sauer-Danfoss has developed a hydraulic circuit cost analysis tool to assist the design engineer in addressing these new criteria.
This tool provides the vehicle design engineer the ability to consider variables like:
• machine usage
• fuel costs
• hydraulic circuit line lengths
• hydraulic circuit conduit diameters
• flow rates
• oil viscosities
All of these considerations can be taken together to achieve an effective balance between cost, efficiency, and total cost of
ownership.
Contact your Sauer-Danfoss representative for more information on this tool and a demonstration on the many ways it can be
used to help solve your design challenges.
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