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Exhaust emissions debate hots up

16th March 1985, Page 33
16th March 1985
Page 33
Page 34
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Page 33, 16th March 1985 — Exhaust emissions debate hots up
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Which of the following most accurately describes the problem?

US-style exhaust emission controls may one day become law in the EEC, but are catalytic converters the answer? Not everybody at the recent annual congress of the International Association of Vehicle Design thought so. Tim Blakemore reports on a lively debate in Geneva

IT WAS INEVITABLE that an international conference on power train development and technology, held just days before EEC ministers were due to meet to discuss proposed new European exhaust emission standards (and particularly catalytic converters) should be preoccupied with that subject. The delegates at last week's Geneva conference, like the ministers as it turned out, could not agree.

In general the American engineers at the conference, including Dr Charles Amman, head of engine research at General Motors, believed that Europe would have no choice but to follow the American route and fit catalytic converters.

Sivet Hiljemark, Austin Rover's chief engineer, summed up the different view held by many European engineers when he suggested that it would be better to develop "lean-burn" engines which did not need the converters, But nobody at the congress argued this case quite so strongly as Society of Motor Manufacturers and Traders president Harry Hooper. Speaking at the opening of the Geneva (car) Motor Show, which ran concurrently with the congress, he said: "The motor industry has demonstrated that the use of catalytic converters is an outdated, expensive and unreliable form of emission control. They use up more fuel and are ineffective in many driving conditions, such as town traffic.

"Most importantly, from American experience, large numbers of motorists knowingly and unknowingly drive around with defective converters on their cars,"

Any visitor to the, Geneva

Show who was interested in looking more closely at the detail of exhaust systems equipped with these controversial catalytic converters would have had plenty of examples to choose from. The West German and Swiss proposals to legislate for them along American lines, despite the EEC ministers' inability to agree, prompted numerous manufacturers to display new types.

They also prompted Harry Hooper to describe the imposition of such "an outdated system" (of emission control) as "flying in the face of all that the motor industry is doing to be at the forefront of technology."

Some of the technology was described in papers presented at the Geneva technical conferences organised by the International Association for Vehicle Design at its second annual congress. In addition to the one on power train development there was a second devoted to automotive electronics and controls and a third concerned with materials technology. Although the emphasis was on cars, the commercial vehicle side of design was not entirely neglected and, anyway, there are areas of overlap between the two sectors.

An example is Ford's electronic engine control system (which has been confusingly dubbed EEC-IV) for a lean-burn petrol engine. This was described in a paper at the IAVD congress as destined for use in cars and •light commercials wherever emission control regulations are in force. On display at the show was a Ford "people and cargo carrier" concept vehicle, the Aerostar, which was equipped with an EEC-1V, 1.6-litre CVH engine. The Aerostar is due to go into production in the USA very soon. In van form it will carry a payload of about 3/4 ton. It should not be confused with the Transit replacement for Europe, which is also on the way. Although this will share the Aerostar's wedge-shaped styling, pioneered in the Trafic and Master vans by Renault, it will be an entirely different "Europeanised" vehicle.

The paper on Ford's electronic engine control system demonstrated that not all American manufacturers accept catalytic converters as the only viable solution to the exhaust emissions problem. Blair Thompson from Ford's electrical and electronics division described the development of a microprocessor based control system for a fuel injected CVH Ford engine which allowed it to run at air/fuel ratios as lean as 20:1 instead of the usual ideal of 14.6:1.

A key part of the system is an exhaust gas oxygen sensor made from a ceramic material, Zirconia, which monitors closely the amount of oxygen in the exhaust gas and signals the microprocessor so that the required air/fuel ratio may be maintained. According to Blair Thompson all that is holding up the start of production of this engine was the lack of a suitable exhaust gas oxygen sensor.

Dr Kit Mitchell, head of the Transport and Road Research Laboratory's vehicle engineering division, presented two papers loosely linked by the topic of commercial vehicle noise. The first described a study by Ricardo Consulting Engineers of Shoreham into how a Stirling engined London bus, a Routernaster, would compare with a conventional diesel engined

Stirling engines are certainly not in themselves new: they have been around in one form or another since about 1910. But modern diesel engines are having to satisfy increasingly stringent demands in the areas of noise, exhaust emissions and ability to run on lower quality fuel — all areas in which the Stirling, an external combustion engine, excels.

That is what has prompted the latest spate of research which, apart from Britain, is concentrated in Sweden and the USA.

Dr Mitchell admitted that when he began to look at the most recent work on Stirling engines he was sceptical about their future development. But now he believes that soon the balance between the Stirling and the diesel may tilt in favour of the former.

Ricardo Consulting Engineers, a highly respected organisation wqh some very level headed engineers, reached a similar conclusion in the study it recently conducted for the Government. Ricardo reckoned that the greater complexity of a Stirling engine would make it about 50 per cent more expensive than an equivalent diesel engine if it were in full production. On an [80,000 vehicle the Stirling engine's initial cost would be about £10,000 compared with about E7,000 for a diesel, and maintenance costs would probably be higher.

On whole-life costs it was estimated that there would be little or no difference. Ricardo's model showed "no significant difference" in fuel consumption between the diesel and Stirling engine on various, typical London bus duty cycles. The most serious practical problem of the Stirling engine for bus applications appears to be that it will not stop running immediately its fuel is switched off. Indeed it will go on running for some 10 minutes until its working gas, hydrogen, loses its pressure. The hydrogen could not simply be dumped because that would cause parts of the engine to melt.

Clearly, Ricardo feels that this problem is not insurmountable and that the Stirling's many advantages warrant further study. The second phase of Ricardo's study would involve the procurement and test of a prototype engine, at an estimated cost of £250,000.

The company is so keen to continue its Stirling research that at present it is trying to raise this money, but there seems little likelihood of it coming from Government. Stirling engine development work in this country could be just one more casualty of the recent sharp reduction in motor vehicle research and development funding which the Government's own Business Monitor figures have revealed.

In the lively debate that followed his paper Kit Mitchell described some of the work being done by the Swedish company, United Stirling AB. The low noise and smooth running of the Stirling makes it attractive for military applications, including submarines, but United Stirling also has some prototypes running in trucks and buses. The drive-by noise level of one of these, according to the latest EEC legislation, is reported to be 70-74dB(A) compared with a normal diesel engined vehicle's 85d6(A).

Dr Amman told the conference that his experience at General Motors with a Stirling engined car had made him less optimistic about its future. "One must look beyond the engine itself to its installation," he said. "The car I drove was not vibration free," He explained why a Stirling engine needs a larger than normal radiator and fan, and how this characteristic led him to be concerned about its ability to operate at high ambient temperatures. He also had reservations about fuel consumption and said it was "surprisingly bad, particularly at idle" on the GM car, but he confirmed that it had low noise and exhaust emissions.

An American professor from the University of Arkansas, David Renfroe, described how his department was working on using a Stirling engine to make an electric vehicle more attractive by extending its range — from 137km to 685km were the figures he quoted for an electric car. The engine used is coupled to a thermal energy storage system which uses a eutectic salt. Instead of the usual Stirling engine's high pressure working gas, hydrogen, the thermal energy storage system uses a fluid at a much lower pressure.

The concept is certainly not confined to the motor industry, explained Dr Renfroe. A submarine engine is under development in France and, remarkably, a thermal energy storage system/Stirling artificial heart is reported to be in the latter stages of development at the University of Washington.

Dr Kit Mitchell's second paper at the power train conference described the UK's QHV 90 programme. This £10m, five year project, which is being funded half by the Government and half by industry, involves the development of quiet versions of three 16-ton gross vehicle weight rigids, from Bedford, Ford and Leyland; three tractive units, from ERF, Foden and Leyland; and eight different types of diesel engine, from Bedford, Cummins, Ford, Gardner and Perkins.

The Ford two-axle rigid in the QHV 90 programme has just returned to the UK from AVL in Austria. Like Concept Cargo it has a despeedeci, turbocharged Dover engine. With encapsulation of the engine it is reported to be capable of staying below 79dB(A) on the latest EEC driveby test.

One of the messages from the IAVD conference on materials technology was that although engineers have a natural mistrust of adhesives, they are certainly going to see more of them in the future. Dr Bill Lees, technical director of Permabond Adhesives, presented a paper which described in detail some recent advances in the calculation of stress distribution in bonded joints.

Using several examples he emphasised how joint design and adhesive formulation in teract, a consequence of this being that it is unwise for designers to reach conclusions on the use or non-use of bonded joints Wore making careful calculations, including finite element analysis, though it was acknowledged that this can be expensive and slow, But Dr Lees was confident that, given an appropriately designed joint, "toughened" adhesives based on epoxy or acrylic material such as his company had introduced some 10 years ago, could bond joints highly satisfactorily — even in areas where most engineers might think bonding inappropriate.

One interesting example was of a propeller shaft tube made of a composite material for a 35 tonne gross combination weight tractive unit. Permabond adhesive was used to bond this to its metal flange coupling. In the severe clutch drop test of this vehicle at its maximum design weight it was reported that the steel and composite components of the shaft broke before the adhesive did.

Alan Haward from National Adhesives and Resins urged vehicle designers to "design with adhesives in mind". He too had some interesting examples of where adhesives had replaced more traditional fixing methods and would do so in the future. These included ERF cab doors, made from smc (sheet moulding compound) in two halves which are bonded together with a hot-melt adhesive. Some car rear lamp lenses

are already bonded this way, and Mr Howard forecast that this would become more common in the future, So many diverse subjects were covered in the three technical conferences of the lAVD's second congress, from automotive electromagnetic compatibility to special high-strength steels, that any attempt to summarise the event in a limited space would be bound to fail. However, if any one paper came close to doing this it was, paradoxically, the first that was presented at Geneva, by Mark Snowdon, managing director of Austin Rover, on Technology and the Marketplace.

His own company is more concerned with cars than commercial vehicles, but he could have been speaking specifically about the latter category when he said: "In comparison with the available technology our products are very conservative, and despite this the customers are suspicious of product inno vations and are often unwilling to pay for the new features which we devise."

Mr Snowdon warned that "the motor industry is faced with two gaps which could grow into chasms. One is between the technology of its products and the available technology at the forefront of research. The second gap is between its own technological capacity and what the customer is ready to accept."

Mr Snowdon's message was that the successful manufacturers of the future will be the ones who bridge these gaps.

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