Tech Briefs
Millbrook expands

Homologation testing at Millbrook's emissions laboratory.

Millbrook Proving Ground has expanded its engine testing capability with the commissioning of a new Engine Technology Center (ETC). The facility includes 12 engine test cells, workshops, a metrology laboratory, facilities for engine construction and analysis, separate dirty and clean wash rooms, and a customer facility. Ten of the new cells are equipped with eddy-current dynamometers for durability and base engine development for large-truck engines up to 400 kW (535 hp), while two are equipped with 250 kW (335 hp) ac dynamometers for fully transient durability and research applications. The ac cells can simulate wind resistance, tire size, vehicle inertia, and driveline gear ratios, allowing road-going cycles to be conducted over long periods without using a vehicle.

Clive Lawson, Head of Powertrain at Millbrook, said of the new facility, "If a vehicle manufacturer needs to test an existing engine in another vehicle application, we can simulate that vehicle on the test bed. The savings are potentially enormous." Engines are built on pallets in the dedicated engine-build facility, then pre-rigged in a dummy cell to ensure that every connection and conduit will fit correctly when lifted into the cell. Each cell is of modular design with all conduits on movable arms, allowing it to accommodate a wide range of engine configurations. Change-over between engines can usually be completed in less than one hour. Each test can be monitored from a control desk in front of the cell or from a remote station at which all test cell data and controls are available. A video camera in each cell allows visual and audio inspection and can be zoomed to analyze specific components. Millbrook said it made a major effort to keep noise levels in the new facility as low as possible. Said Lawson, "For example, to take heat from the engine cooling water we have specified large, low-speed fans that are nearly silent. Where the generation of noise cannot be prevented, we have used high-density concrete to contain it."

"Advances made in exhaust emissions-test systems have been enormous," said Lawson. "Looking back 30 years, very basic equipment was in use, with exhaust gas collected in large Tedlar plastic bags, and domestic gas meters used to measure volume. Component measurements were also basic; just CO and hexane. The levels of emissions were just as basic, with vehicles producing in excess of 100 g (3.5 oz) of CO per test." But in the early 1970s things improved, with the ability to measure CO, CO2, NOx, and hexane measured although "big bag technology" was still necessary. By the mid-1970s, Millbrook was introducing automated testing although its first computer had a mere 34 K of memory. "I don't believe you can buy a personal organizer with that little memory now, but we still managed to write programs allowing second-by-second modal analysis. The vehicles had no catalyst, no fuel injection, no lead-free fuel, but emissions were beginning to reduce a little!"

But from that time to the present vehicle emissions have continued to be reduced and environmental pressures will ensure that the trend continues. A significant expansion at Millbrook has involved work on alternative fuels, with the achievement of emissions levels below those required for conventionally fuelled vehicles, for both regulated and unregulated emissions.