Detroit Diesel goes Emitless

Detroit Diesel Corp. (DDC) has a system that it claims will achieve further reductions in diesel-engine-exhaust emissions. Earlier this year, the company and Engelhard Corp. formed an alliance to develop a new exhaust-emissions-control system, integrating Engelhard's technology with Detroit Diesel Electronic Controls (DDEC) to reduce significantly emissions of particulate matter from diesel engines.

The system, a particulate filter integrated with DDEC controls, is named Emitless. It functions as a muffler, providing noise attenuation. As the exhaust gasses flow through Emitless, they pass over a proprietary catalyst and through a particulate filter. The filter can reduce particulate emissions by up to 90% when combined with low-sulfur diesel fuel. Under normal operating conditions, the filter continually self-regenerates, cleaning itself without external controls or heating devices. In addition, Emitless also reduces hydrocarbon and carbon monoxide emissions.

"The Emitless filter is truly a breakthrough for diesel-engine technology and can be applied to most modern diesel engines," said Pat Scully, Vice President of Bus & Coach Sales for Detroit Diesel. "Our first target is the transit bus industry. We are making this announcement to notify our current and future customers that Emitless is the exhaust filter device that DDC approves for use on its engines. Our engineers have developed a means for DDEC to monitor system performance, making the system fully integrated within the engine."

The filters will be marketed through authorized DDC outlets and will be available for use on trucks, generator sets, and other diesel-powered applications in the future. The Engelhard particulate filter is patented and has been tested on vehicles at several U.S. sites as well as in Sweden, France, and the Netherlands.

Midwest's ac-powered centrifuge

Midwest Engineered Product's CentraSep combines a bowl/blade clutch design with one ac motor and ac motor drive.

According to Midwest Engineered Products Corp., its centrifuge will enable OEMs and suppliers to filter and solidify the waste out of paint booth curtain water or phosphate baths, machining coolants, honing oils, deburring fluids, rinse tanks, or other wastewater systems.

The centrifuge combines an innovative bowl/blade clutch design with a single ac motor and ac motor drive. The centrifuge can remove particles from coolants or lubricants at a processing rate ranging from 95-510 L/min (25-135 gal/min). Called CentraSep, the centrifuge is able to remove as much as four times the quantity of fines as traditional centrifuges, according to Midwest; it is also able to extend the fluid life for any given process by at least four times.

The centrifuge is completely automatic and, once set up, "can operate out of sight and out of mind, while providing literally unprecedented fluid filtration-performance and product production benefits," said Jeffrey Beattey, President of Midwest Engineered Products. The centrifuge positively synchronizes the bowl and blade assembly—which consists of two scraper blades and two stilling vanes. A positive-locking clutch couples the bowl's main spindle and the blade together so that both rotate at precisely the same speed when processing fluids. The motor is linked to the main spindle via a single chevron-style "timing" belt and pulley design that prevents slippage.

A positive-locking clutch couples the bowl's main spindle and the blade together so that both rotate at the same speed when processing fluids.

"The fluid is forced to move smoothly throughout the bowl as it strikes an accelerator on entry and descends," said Beattey. When the automatic process cycle is complete, the feed pump turns off and the locking clutch uncouples the blade assembly from the main rotor spindle and locks the blades into a fixed position. The bowl is then rotated and the dry, dense particulate is scraped loose by the blades and falls into a collection drum, ready for recycling.

Midwest credits a fused electrical-control/mechanical design for making the new centrifuge a reality. Accelerating the bowl and blade very rapidly for the processing cycle, bringing the loaded bowl to a controlled stop, and turning the bowl against the scraper blades require high, breakaway torque and precise motor control. Built into the centrifuge is ABB's ACS 600, 7.5-kW (10-hp) motor drive featuring open-loop Direct Torque Control (DTC), which enables the drive to calculate the state (torque and flux) of a motor 40,000 times per second. This responsiveness to the motor load makes the drive virtually tripless. No encoder for feedback from motor to the drive is required, which reduces capital costs up to 25% when compared to similar flux vector or PWM drives, according to Midwest.

"Through the DTC feature, the drives can adapt to and handle changes in load, over-voltages, and short circuits immediately," said John Emmert, an electrical design consultant for Midwest. If the load in the bowl becomes too heavy, the ac motor enters a stall mode rather than turning the bowl and breaking the shaft or blade assembly.

The process and scrape cycles for the CentraSep. Click to enlarge

Use of proprietary software enables Midwest to program and operate the drive at extended torque parameters. To ensure that the exact same start-up software is programmed into every drive on all production units, Midwest uses ABB's DriveWindow tool.

This critical programming is not application specific. Instead, to adjust the speed—and centrifugal force—of the bowl for different types of process fluids, Midwest uses a call-out on a programmable logic computer (PLC) built into the panel. The drive, in tandem with the PLC, gives Midwest the flexibility to customize the centrifuge for any kind of application.