Efficiency gains with modern components
By Steve Skinner09 November 2010
While engine manufacturers have been tasked with meeting emissions compliance, component manufacturers will play an important role in maintaining the power output and productivity of next generation equipment.
Tier 4 Interim emission compliance will change the power characteristics of off-highway equipment and, in cases where exhaust gas recirculation (EGR) has been adopted, will create greater heat rejection than found in current models.
EGR is an engine-based system that cools and then re-circulates approximately 15% of the exhaust gases to reduce the combustion temperature in order to minimise the creation of Nitrous Oxide (NOx). This system inherently creates heat that needs to be dissipated efficiently to prevent excessive engine and engine bay temperatures. As a result, cooling systems will be more important than ever before.
Vice president of sales for the Americas at Sauer-Danfoss, Rick Sporrer told iC, "For those of us in the mobile equipment sector and especially hydraulics and electronics, the first two emissions tiers were really non-events as all the changes were to the internals of the engine.
"With Tier 3 and Tier 4 Interim, and especially with Tier 4 Final in due course, everything is going to be external to the engine and this has created opportunities for us."
Mr Sporrer said that heat rejection will increase because of EGR and as such cooler manufacturers are going to have to redesign their system installations. "In this respect, OEMs have contacted us about fan drives because they want to get rid of their belt drives. They want a modulating fan drive that will save power and allow greater flexibility in the positioning of the cooler," he said.
Sauer-Danfoss launched its high pressure, heavy duty D Series cast iron fan drive gear motors and its SGM2 and SGM3 lightweight aluminium fan drive motors at Bauma featuring integrated valve systems that match the fan speed to the cooling demand. All three units also feature reverse fan rotation to blow chaff from the radiator so that it remains clear to operate at its optimum capacity.
"Alongside the D Series, we also launched our sub-system fan drive application software at Bauma, which controls the time and speed of hydraulic fan drives," said Mr Sporrer. Featuring Sauer-Danfoss Plus+1 microcontrollers the system monitors cooling parameters, calculates cooling demand and provides an electronic signal that controls the fan speed.
As well as heat rejection, another area that is likely to be affected by the emissions legislation is hydraulic flow. "To date, the engine manufacturers have told us that by the time we get to Tier 4 Final compliance, they believe they'll have to slow down the engine to optimise the combustion process. This could see engine speeds cut by -10% to lengthen the combustion time, but such a move would directly affect the hydraulic flow," said Mr Sporrer.
In order to address this reduction in hydraulic flow, Sauer-Danfoss believes there are two options that can be taken. The first is to increase the pressures in the hydraulic system, while the second is to more accurately tailor the hydraulic system to the application.
Mr Sporrer told iC that the company is exploring the idea of increasing system pressures by up to +10%, but any increase has to be achieved with suitable lifetime characteristics maintained. "To go in this direction we need to understand machine duty cycles better than we have in the past. Increasing pressures is a whole system issue because it affects not only the pump, but also the hydraulic lines, control valves and fittings," he said.
The other area which is seeing development is bespoke hydraulic systems. Mr Sporrer said that in the past hydraulic components were sized based on a single worst case operating mode, in which multiple functions were simultaneously demanded. "In understanding power management, we have been able to develop systems so that even when an operator is commanding multiple functions, we can manage the power levels to ensure the work can still be done while decreasing the maximum power requirements," he told iC.
A key element of optimising power management is to eliminate parasitic components on the hydraulic line. "In the past when we sized hydraulic lines, fittings and control valves we did so without really considering line loss and pressure drops because our prime driver was to reduce component costs. The criteria have now changed in that power utilisation and parasitic drain are now more important than individual component costs," said Mr Sporrer.
In a practical context, Mr Sporrer explains that one of the peak power conditions for a wheeled loader, for example, is when it is pushing into the pile and lifting the bucket at the same time. With the Sauer-Danfoss hydraulic fan drives, controlled by the company's sub-system fan drive application software, as soon as the loader begins to strain, the hydraulic fans can be automatically switched-off for 90 seconds to enable the operator to complete the maximum power task with up to +20 kW of additional power made available.
"This is what we class as distribution of power and the operator wouldn't even know it was happening. It is a way of coping with any net power reduction from the next generation engines and depending on the power consumption of the fans, could even enable an OEM to downsize engine capacity," he said.
Bosch Rexroth believes a key element in achieving Tier 4 Interim and Tier 4 Final compliance will be through the adoption of energy-saving hydrostatic drives. Director of sales pumps and motors for the hydraulics business unit, Peter Dschida said, "The hydrostatic travel drive represents an approach to conserve dynamic energy and cut engine emissions.
"Proper dimensioning of the hydrostatic drives with high-pressure pumps and motors can significantly increase the efficiency of the travel drive and this clears the way for either engine down-sizing or reducing fuel consumption through reduced engine speed while still maintaining performance."
Bosch Rexroth has developed a new generation of pumps and motors designed to meet the requirements of Tier 4 Final compliant equipment. The A4VG axial piston pump and the A6VM motor have been revised to cope with peak pressures of up to 500 bar, while at the same time improving rated speed and component efficiency.
Both units feature a modular control enabling OEMs to employ anything from simple mechanical control to on-board electronics to achieve the optimum strategy.
"Thanks to the higher performance, it is possible to maintain machine performance even when the installed drive output is reduced," said Mr Dschida.
At Bauma the company launched its diesel hydraulic control (DHC) that combines management of the engine and hydraulics. Chairman of the hydraulics business unit, Helmut Wagener said, "Via the combined demand control our DHC can reduce fuel consumption by up to +20%. Most importantly, the system ensures that the same amount of power will be available to Tier 4 Final machines despite the sluggish load properties expected from the compliant engines."
The DHC system takes information from the joystick and passes it to the engine's electronic control unit to prepare the engine for imminent mechanical load. "Because the system controls the diesel engine to produce only the power that's needed at any given time, tests have shown us that fuel consumption will be reduced without any sacrifice to the dynamic response of the travel drive and hydraulics," said Mr Wagener.
Bosch is currently developing its CRS2-18-OHW common rail fuel injection with a system pressure of up to 1800 bar. The system, which will go into production in mid-2012, operates with a new injector featuring a pressure-balanced solenoid valve.
Compared to previous generations, the new fuel injection system will offer lower fuel consumption and improved service life. The modular design means the system can be integrated easily into existing and Tier 4 Interim engines producing up to 130 kW across four cylinders or 200 kW in six cylinder configuration.
Bosch has also developed a common rail fuel injection system for engines with between four and 16 cylinders, developing between 200 and 560 kW. The CRSN 3.3 is configured for pressures of between 2000 and 2500 bar and will also offer lower fuel consumption and reduced CO2 emissions.
ZF has developed a three stage technology road map for construction equipment, which commenced with an upgrade of its transmissions and axles to gain efficiency. Vice president of construction machinery systems, Herman Beck said, "With the efficiency package we have already attained fuel savings of up to +20% and an increase in productivity of up to +40%."
At Bauma, ZF launched its hydrostatic-powersplit CVT transmission with even greater potential to reduce fuel consumption. It also unveiled its continuously variable cPower system designed to cope with lower and constant engine speeds.
The final step will be towards hybrid technology in the shape of ZF Ergopower, which will represent further reductions in fuel consumption, an increase in work output and a reduction in exhaust emissions.
Mr Beck said, "An intelligent driveline design can provide an improvement in fuel efficiency of up to +30%, thus allowing a significant contribution to emission reduction without negatively affecting productivity."
Axiomatic has introduced a series of low cost sensors that can measure + 900 of tilt or 3600 of angular rotation. The AX06025X series features CANopen networking and an RS-232 port or three voltage outputs for communicating the angular measurement while the J1939 inclinometer is fully configurable using the Axiomatic electronic assistant programming tool for PCs.
The company has also launched its bucket positioning system (BPS) for continuous assessment of an attachment's position as part of a 2D or 3D OEM machine control system.
A spokesperson said, "The BPS machine control interface calculates and monitors the angular position of multiple inclinometers on an excavator and communicates the data over Ethernet or CAN bus to the operator display in the machine cab. As an OEM application platform, the BPS is a cost-effective way to integrate machine control systems on a variety of equipment."
Sensors are at the heart of Fozmula's new T/LL171 fuel level sender, which measures fuel levels at elevated ambient temperatures of above 800 C. "Despite the tendency for electronic circuits to drift at high temperatures, the new sender is able to provide a stable process output," said a spokesman.
Fozmula's range of liquid level senders and sensors and temperature and pressure switches are already used in diesel engine applications to provide warning data about water, oil and air temperatures to engine management systems. With the introduction of Tier 4 Interim compliant equipment on the horizon data collection and transmission will be of greater importance than ever before.
OEM suppliers will play an important role in the switch to Tier 4 emissions compliance and maintaining the performance of equipment. As Mr Sporrer told iC, "We can find ways to cope with the changes to equipment systems without having to add significant cost or demanding additional installation space. The key thing now is to highlight the impact on equipment of Tier 4 Interim compliance so we can help OEMs deal with the changes.