AVL measures up to emissions

The Smart Sample SPC-472 from AVL North America is a high-precision, partial-flow dilution system for the graviometric measurement of particulates for engine certification, research and development, and fuel and lube applications. Click to enlarge

AVL North America made several major announcements at the SAE 2002 World Congress, including the introduction of a new tunnel design for its SPC-472 sampler. According to William Silvis, Director of Research and Development at AVL, the design achieves full-flow constant volume sampler (CVS) correlation for particulate testing, producing partial-flow system results comparable to those from more expensive full-flow equipment. "This is of particular significance when we consider the standardization efforts underway to develop a worldwide method for testing and sampling heavy-duty diesel engines," he said.

Transient partial-flow systems have historically experienced two types of deposition losses—diffusion and thermophoretic—inside the sampling system. According to AVL emissions specialist Norbert Kreft, AVL modified the probe, transfer tube, and tunnel to minimize those losses. A shorter probe length and thinner probe wall, combined with additional insulation to the mixing point, contribute to reductions in thermophoretic losses. The thinner tube material allows for a quicker assimilation of the exhaust temperature, reducing particulate loss. An adjustment of the angle within the re-circulation zone diffuses the sample throughout the mixing zone and reduces deposits.

AVL North America introduced a new tunnel design for its SPC-472 sampler that achieved full-flow constant volume sampler (CVS) correlation for particulate testing. Click to enlarge

To compensate for system time delays, the SPC-472 implements "look-ahead" controlling, which "uses a pre-recorded exhaust flow signal to control the partial-flow sampling system," said Kreft. Accurate sampling methods rely on keeping the sample flow in direct proportion to the engine exhaust flow. "For emissions calculations, the actual measured flow is used. For controlling, a pre-recorded signal is time-shifted to completely compensate for unavoidable systemic and pneumatic time delays."

AVL also introduced a partial-flow, bag-sampling system, or bag mini-diluter (BMD), for measuring the emissions from super ultra-low emitting vehicles (SULEV). AVL claims the BMD-150 exceeds the basic requirements outlined by the AIGER consortium, including a flexible dilution circuit to provide the proper performance on a wide range of fuel types, from methanol and compressed natural gas to clean, reformulated gasoline.

The AVL BMD-150 is shown with a mass-flow controller inside a heated enclosure.

The U.S. EPA encourages the use of BMD sampling systems for all future low-emissions measurements because they measure exhaust emissions more accurately than traditional CVS units. According to the EPA, BMD systems eliminate water condensation, minimize and optimize the dilution ratio and effects of dilution gas background concentrations, and reduce system-generated hydrocarbons.

"Such partial-flow systems (as BMD) will be adopted as a worldwide standard for testing heavy-duty diesel engines, and are under consideration in the U.S. for regulating off-road engines," said Gerald Marek, AVL Global Product Manager of SPC systems.

- Jean L. Broge

Delphi fuel-cell APU for BMW

Delphi and BMW have joined forces to demonstrate the viability of a solid-oxide fuel-cell system as an auxiliary power unit.

Delphi Automotive Systems announced at the SAE 2002 World Congress that it and BMW are jointly developing a solid-oxide fuel-cell auxiliary power unit (APU). Applying the fuel-cell APU for transportation is part of a significant trend for the electrification of vehicle accessories. Many automotive systems are being converted to electric power to support cost, weight, and packaging objectives. Intermittent accessories, such as power steering and brakes, have already been adopted.

High-power accessories, such as air-conditioning and valvetrain systems, have been developed more slowly due to the limited onboard electrical capacity and their low efficiency. Now, high-power, high-efficiency electrical machines are being introduced for 42-V operation. These high-voltage systems will provide capacity to continue the electrification of new features. Fuel-cell systems have over a 50% fuel-to-electric conversion efficiency because of the direct chemical-to-electrical conversion. This efficiency allows for the continued transition to electric accessories that operate independent of the engine. Such capability is an important step for the introduction of mild hybrid vehicles.

Engineers from Delphi discussed at Congress the advantages of applying a fuel-cell power unit to the dual-voltage 42-/14-V automotive electrical system using the evolving 42-V PowerNet specifications. These vehicles require the APU to operate on fuels other than gasoline, such as diesel or jet fuel, and the applications are expected to play an important role in the introduction of this technology to the marketplace.

Delphi used a fuel-cell reformer supplied by Global Thermoelectric.

The solid-oxide fuel-cell-based APU is a major shift in the supply of electric power for transportation. Its applications can include premium class automobiles, work trucks, recreational vehicles, fire-rescue vehicles, military vehicles, ships, and aircraft. The separation of onboard electricity production from the vehicle's internal-combustion engine is consistent with providing increased comfort to the customer in an efficient, clean way. Solid-oxide fuel-cell technology also is easily applicable to stationary power. Residential primary and back-up power, distributed power, and co-generation are achievable with any liquid or gaseous hydrocarbon fuel.

Current development is focused on reducing cost; improving cycle durability, startup characteristics, and power density; and developing reformation technology for a broad range of hydrocarbon fuels. With solutions to these challenges, this technology offers the potential for high market penetration in the next decade.

- John Fobian