This section was edited by Associate Editor Alan S. Brown.
| POWER TRANSMISSION AND MOTION CONTROL |
FROM HYBRID TO COOLING TOWER
What do power systems for hybrid vehicles and cooling towers have in common? Perhaps their drive trains and controllers, according to Baldor Electric Co. Hybrids use a permanent magnet direct-drive motor linked to a variable speed controller. Now Baldor has come out with a similar system for cooling tower fans.
The company’s new RPM AC cooling tower motor and VS1CTD variable speed controller were developed specifically for the application. According to Baldor, the combination of laminated steel finned frame construction and high strength permanent magnets yields a motor that has significantly better power density, torque (especially at partial loads), and efficiency than similar induction motors. The motor mounts directly onto the fan without a gearbox or shaft and operates at variable speeds to save energy.
Baldor uses a variable speed controller to operate the motor at slower speeds. This is an area where permanent magnet motors excel, since they are synchronous machines that achieve constant torque (without slip) at very precise partial speeds.
Baldor’s new motor mounts directly onto fans, eliminating the gearbox and driveshaft.
This makes a big difference when it comes to energy use. Although cooling towers are designed for worst case (highest airflow) scenarios, their fans often run considerably slower. Since the input power to the motor varies with the cube of the motor speed, operating the motor at half speed consumes only one-eighth the power.
The RPM AC permanent magnet motor and VS1CTD controller are designed for fast tuning and commissioning. The controller comes with a graphic keypad that leads users through setup and maintenance diagnostics.
Baldor claims the system is economical, even though permanent magnet motors cost significantly more than induction motors. The system achieves economies because it replaces gears, shaft, and the rest of the drivetrain with an electronic controller and reduces energy consumption to save money over the long term.
BLENDING FUELS TO BOOST EFFICIENCY
RESEARCHERS AT THE UNIVERSITY OF WISCONSIN–MADISON SAY THAT BLENDING DIESEL FUEL WITH GASOLINE CAN IMPROVE DIESEL ENGINE FUEL EFFICIENCY by an average of 20 percent while meeting U.S. government emissions mandates without costly pollution control equipment.
While fast-response fuel blending technology would require modification of diesel engines and separate fuel tanks for diesel and gasoline, it would use fuels readily available at the pump today. Rolf Reitz, a mechanical engineer who led the research, said the technology can also be applied to gasoline engines.
If all internal combustion vehicles were converted to dual fuel engines as efficient as his most efficient prototype—53 percent—Reitz estimates that the United States would save one-third of all petroleum used for transportation, or roughly 4 million barrels per day.
Industry is apparently listening. The Department of Energy and University of Wisconsin’s Diesel Emissions Reduction Consortium, which includes 24 industry partners, are funding Reitz’s research.
Rolf Reitz (with tie) and his research team believe diesel-gasoline mixtures
could slash vehicle fuel use by one-third.
Fast-response fuel blending calls for mixing the two fuels inside the engine’s combustion chamber. Ordinarily, gasoline does not burn in a diesel engine because it is less reactive than diesel fuel. When Reitz sprays the two fuels into the combustion chamber together, however, the diesel ignites the gasoline.
The blending technology matches the diesel-gasoline ratio to operating conditions. Under heavy loads, such as accelerating or climbing a hill, the fuel mix might go as high as 85 percent gasoline. Under lighter cruising loads, the percentage of gasoline would fall to 50 percent.
According to Reitz, the mix enables diesel engines to operate up to 40 percent cooler, which reduces energy loss through thermal transfer. Better yet, controlling the diesel-gasoline ratio not only improves burn efficiency but also reduces emissions. In fact, it enables trucks to meet particulate and nitrogen oxide emission levels mandated by the Environmental Protection Agency without buying expensive catalytic reduction or exhaust gas recirculation equipment.
Reitz used computer models to develop the blending strategy. This enabled him to run thousands of simulations and optimize his power strategies before testing the technology on a Caterpillar heavy-duty diesel engine. The tests confirmed the model’s predictions. The best tests achieved 53 percent thermal efficiency, 20 percent higher than conventional diesel engines. In fact, it was higher than today’s gold standard for commercial engines, the turbocharged two-stroke diesels used in maritime shipping.
“Even more striking, the blending strategy could also be applied to automotive gasoline engines, which usually average a much lower 25 percent thermal efficiency,” Reitz said. “Here, the potential for fuel economy improvement would even be larger than in diesel truck engines.”
SIMPLER MULTIAXIS APPLICATIONS
Several new products are intended to make it easier to design and control complex manufacturing systems using LabView software. National Instruments introduced LabView 23 years ago to enable PCs to make sophisticated scientific and engineering measurements. The software has morphed into a general purpose way to define I/Os, take measurements, and model and implement control systems in a single development environment.
LabView’s strength is its high-level graphical development interface, which hides many of the programming details (though users have the option of digging into those details) when developing automation applications. NI’s latest extensions make LabView a more practical real-world automation environment. They include a new motion control module, new drivers for servo and stepper drives, and a broader range of programmable automation controllers.
National Instruments’ new software and drive interfaces make
it easier and more practical to program motion control in
LabView.
The LabView NI SoftMotion Module simplifies advanced single- and multiaxis motion control by giving users access to powerful motion profiles through function blocks based on the open source PLCopen motion control library. PLCopen functions range from straight-line, arc, and contoured moves to electronic gearing and camming.
The SoftMotion interface also provides such powerful functions as trajectory generation, spline interpolation, and position and velocity control. SoftMotion also lets engineers simulate designs created in SolidWorks 3-D CAD using SoftMotion motion profiles.
NI’s new C Series drive interface modules let LabView users incorporate hundreds of NI and third-party drives and motors into motion systems. The NI 9512 module connects to stepper drives and motors, while the NI 9514 (single-encoder) and NI 9516 (dual-encoder) modules interface with servo drives and motors. Since drives are typically processing-intensive, all three modules perform on-board processing to free up the main processor in the controller.
The third leg of NI’s new automation platform is its CompactRIO line of reconfigurable programmable automation controllers. CompactRIO uses embedded chips to achieve high speeds and reliability. The newest addition to the line is the NI 9144 deterministic Ethernet expansion chassis, which makes it possible to daisy chain CompactRIO and other NI industrial controllers to create distributed motion applications. The company also introduced a stand-alone CompactRIO industrial controller.
LUBRICANTS FOR LOW-CARBON ENGINES
MANY NATIONS ARE CONSIDERING REGULATING CARBON EMISSIONS FROM VEHICLES. There are many ways to get there, from hybrids and plug-in electric vehicles to diesel exhaust recirculation and downsizing. One technology less often discussed is advanced lubricants.
U.K. engineering research consultant Ricardo plc is launching a consortium of automakers, Tier 1 suppliers, oil and lubricant additive manufacturers, and government agencies to address lubrication issues. The group will initially focus on soot created by exhaust gas recirculation and next-generation engines, ultralow-viscosity lubricants, and the effects of lubricants on emissions and after-treatment performance in future engines.
A new research consortium will study lubricant use in advanced and alternate fuel vehicle engines.
Exhaust gas recirculation systems are used to reduce nitrogen oxide emissions by recycling exhaust back to the engine. This produces soot, which ultimately ends up in the engine’s lubricant. Soot appears to cause wear through abrasion, lubricant additive absorption, and lubricating film gap creation (which produces hot spots). It is unclear which mechanisms dominate under what conditions.
Today exhaust gas recirculation systems are used on heavy-duty diesel engines. This is likely to change as engineers attempt to shrink gasoline engines without giving up power. While smaller, hotter engines have a smaller carbon footprint, they also produce more nitrogen oxides. Exhaust gas recirculation is one way to control their NOx emissions. Ricardo plans to irradiate engine components and measure radioactive wear particles to understand their wear mechanisms to help chemists create lubricants that handle soot under all conditions.
Biofuels, especially biodiesel (widely used in Europe), may oxidize and form gums and deposits that change lubricant viscosity. They also have chemically active components that can embrittle seals, corrode soft metal surfaces, and leach lead, tin, and copper from bearing steel alloys. Ethanol increases the solubility of water in lubricants or oxidizes to form corrosive chemicals. Ricardo’s program will look at how lubricants can help motors surmount these challenges.
Chemists have long sought to balance viscosity with lubricity. While viscous lubricants provide sturdy, low-friction films, engines have to work harder to overcome their viscosity. This leads to parasitic power losses. Ricardo wants to investigate new ultralow-viscosity lubricants.
The development of these lubricants may hinge on the redesign of engines to replace sliding contacts with rolling contacts and on the use of diamondlike carbon and other ultrasmooth surface coatings on moving parts.
Other lubricant advances may also require engine redesign, according to Craig Goodfellow, who directs the fuels and lubricants project at Ricardo. In the past, he said, engine and fuel developments have driven lubricant advances. Goodfellow believes further advances will require the more integrated approach, which the consortium hopes to prove.
SYSTEMS APPROACH IMPROVES FAN RELIABILITY
OVER THE YEARS, INDUSTRIAL PROCESSES HAVE GROWN HOTTER TO BOOST EFFICIENCY. That means fans increasingly operate at higher temperatures. They usually run at high speeds with light radial loads, moving air filled with particulates that settle unevenly on an impeller and move it out of balance.
According to SKF USA Inc., all this tends to heat up bearings, shortening bearing lubrication life and causing bearing failures that lead to unplanned fan downtime and production losses. No wonder SKF says it receives at least one urgent phone call daily about heat-related fan problems.
So SKF has launched an upgrade service that it says can prolong bearing and lubricant service life while lowering maintenance costs and improving the sustainability of industrial fans. The upgrade combines an automatic circulating lubrication system with a toolkit of optimized bearings, housings, and seals.
Centralized lubrication, self-aligned bearings, and plummer block housings
designed to disperse heat help fans last longer.
The company estimates that lubrication issues are the source of 36 percent of all premature bearing failures. SKF uses a centralized system to deliver precise amounts of grease to each fan on the system while avoiding over-lubrication.
The company’s bearing toolkit typically combines self-aligning bearings with plummer block housings and specialized seals to help manage heat. The plummer block housings are designed to draw heat away from the bearing while providing precise, high-stiffness support.
The self-aligning bearings combine the company’s CARB toroidal roller bearing in the non-locating position and a spherical roller bearing in the locating position. The toroidal bearing accommodates the thermal expansion of the fan shaft, reducing friction, temperature, vibration, and power consumption while supporting higher fan speeds.
SKF also provides condition monitoring systems. These range from basic units that warn of potential bearing failure to more advanced predictive maintenance systems.
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