22 May 1998


By Mike Williams

CLEANING UP exhaust emissions from tractors and other powered machines is one of the top priorities for engine manufacturers as stricter emissions limits are introduced. But the cost of meeting the regulations will eventually mean higher prices for tractors and equipment such as combines and telehandlers.

The contribution from engine-powered farm equipment to the total UK production of harmful exhaust emissions is probably less than 1%, and although the problem is relatively small, engine makers hoping to remain in the tractor and machinery market in Europe and America must meet the exhaust emission regulations.

Although the new generation of "clean burn" engines are a multi-million £ investment for the manufacturers, the actual cost spread over several years on a per engine basis is relatively small and should be balanced by additional benefits for the customer, according to Adrian Heath, design manager for Perkins Technology.

"Simply reducing exhaust emissions to meet the regulations is not very difficult," he said, "but it is more difficult to achieve without losing other desirable characteristics such as cold start capability, long-term reliability or fuel efficiency.

"The easiest way to reduce NOX (nitrogen oxide) emissions is to retard the engine timing, but the disadvantage of doing this would be unacceptable. It would increase the fuel consumption and also generate additional waste heat which would require a larger cooling system. We cant simply consider exhaust emissions in isolation because we have to provide other customers benefits as well, and it is certainly possible to reduce NOX and particulate emission levels while achieving other performance improvements."

One example is using fuel injection equipment which operates at higher pressures and has smaller nozzles to achieve more efficient atomisation. This can make a significant contribution to exhaust emission control, but it can also help to improve fuel efficiency and torque characteristics, said Mr Heath.

"In fact there is a correlation between a reduced level of particulates or smoke in the exhaust and the torque performance of the engine, and reducing the particulates can have a beneficial effect on torque characteristics. We used this very successfully on the new Perkins 1000 series engines which have a 20% increase in injection pressure, easily exceed the current exhaust emission regulations and have an improved torque performance."

Turbocharging and intercooling may also have dual benefits. Both can significantly reduce NOX and particulate levels in the exhaust, and both have a beneficial effect on fuel efficiency, said Mr Heath. "This helps explain the large increase in the number of tractor engines with a turbo and, in some cases, an intercooler as well."

Emission control

Efficient combustion is an important factor in emission control and in squeezing more work out of less fuel, and this has been a key area in the Perkins R&D programme.

Information gained from making detailed studies of what happens inside the combustion chamber will continue to play a part in improving engine design to meet stage 2 of the EC emission legislation, likely to be introduced in 2003 or 2004. Stage 2 brings in tougher standards for both NOX and particulates.

A different approach to reducing harmful exhaust emissions in the future would be burning alternative fuels such as natural gas or biodiesel, and Mr Heath said these could have a significant impact on the level of pollution caused by engine exhausts.

"Making use of these fuels is not a technical problem," he said. If the economic and political problems can be overcome, we would have no difficulty producing engines which would burn fuel derived from rapeseed, for example." &#42

Left: Latest generation of 1000-series motors

the 1004-40T.

Below: Another engine goes through the development phase.

Above: Adrian Heath, design manager at Perkins.

Perkins swirl induction and Fastram combustion system.