Fuel efficiency: the way forward
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The combined I Mech E/IRTE seminar on commercial vehicle fuel consumption considered many more ways to improve it than just through technical development. Tim Blakemore reports on the recent wide ranging London conference
INSTITUT ON of Mechanical Engineers ectures and seminars invariably have good solid technical content, but they have seldom attracted large numbers of operating engineers. That is probably because they generally have been regarded as toohighly technical and/or as being concerned with subjects several stages removed from the everyday problems facing fleet engineers.
However, a joint I Mech E/IRTE seminar in London two weeks ago demonstrated clearly that if the subject matter and speakers are right, there will be no lack of support from the operating side of the industry. The I Mech E's Birdcage Walk lecture theatre was packed for the seminar on "Commercial Vehicle Fuel Efficiency".
The main speakers were Peter Capon, product development director, Leyland Trucks; Jim Clifton, principal professional and technology officer from the Department of Transport's vehicle standards and engineering division; Jim Bodmer, technical director of High Technology Systems, a Swiss company which manufactures fuel flow measuring equipment; and Terry Goldrick, director, professional and engineering services, Freight Transport Association.
Peter Nevitt, director of truck operations at Ford was the seminar chairman and John Furness, former DTp chief mechanical engineer, gave the opening address and directed the general discussion that followed the individual presentations.
In his opening remarks Mr Furness put the importance of commercial vehicle fuel efficiency into perspective. "Commercial vehicles, light and heavy, account for about 30 per cent of road transport fuel used", he said. He then used Transport and Road Research Laboratory figures to show where most of the energy contained in each litre of diesel fuel is lost. He was in no doubt that the subject of commercial vehicle fuel efficiency would become increasinglY important in the future, warning that "crude oil prices may double or treble in the hext 15 years".
With due regard to the large number of operators present he drew attention to the importance of "correct and timely" maintenance and of correct vehicle specification in the first place. The role of legislation in encouraging (or not) fuel efficiency improvements was to b considered later in the day. For his part, Mr Furness did no more than acknowledg that "Government has a part to play also' r.
Peter Capon's paper the first of the day, was on "Design for Fuel Efficiency." It was later described by Michael Monaghan, technical director of Ricardo Consulting Engineers as "a logical and comprehensive review".
The availability and quality of diesel fuel were the first subjects addressed. Mr Capon began by posing the question: "Should diesel engines continue to be developed, or alternatives sought?"
Since we had been assured that the supply of petroleum products would continue until "well into the 21st century", he argued that the development of diesel engines should certainly also continue. But he was in no doubt that diesel fuel quality would deteriorate and he called on oil companies to release more information, for example on what future cetane numbers will be, and to hasten the introduction of an international standard. Diesel engine designers striving to improve fuel efficiency were being frustrated without this knowledge.
Mr Capon showed a slide illustrating the effect on engine performance of a reduction in its fuel's cetane number from 50 to 40. Specific fuel consumption dropped by 2 per cent, although power output was not significantly affected.
Two other factors which would make improved diesel engine fuel efficiency more difficult to achieve were increasingly stringent noise and exhaust emission regulations.
In spite of these negative influences on fuel efficiency, Mr Capon was optimistic about future improvements: "The thermal balance of the diesel engine still leaves major scope for improving fuel efficiency", he said, illustrating his statement with these typical figures from an engine of today.
Brake power 36 per cent Exhaust loss 32 per cent Conducted loss 9 per cent Mechanical loss 23 per cent Where would the improvements be made? Mr Capon outlined some of Ley land's development work on hotter running engines with ceramic coated cylinder heads and on detailed work to reduce friction losses, which comprise more than half of the 23 per cent mechanical losses.
Several manufacturers were pursuing the possibilities of an exhaust turbine geared to the flywheel to take advantage of the additional exhaust heat in an insulated engine. But Mr Capon was sure that "it will be a long time before this features in standard automotive products."
Leyland's product development director was unreservedly enthusiastic, however, about the benefits of the already established principle of air-to-air charge:ooling: "It can only be a matter of time before the overwhelming benefits offset the increased complexity and reduced lowspeed torque, and all engines are designed to be operated in this mode," he said.
Mr Capon was equally clear about the directions that would followed in the development of fuel injection systems: "In order to improve economy and reduce smoke, the injection must be advanced. To accept lower fuel quality, reduce invisible emissions and reduce noise it must be retarded. This conflict can be compensated by the use of a high-rate injection over a shorter periods. To achieve this, however, injection pressures up to 1,200 bar will be required with the considerable increased :ost of larger pumps."
Mr Capon saw electronically controlled unit injectors as the ideal way to achieve the accurate control over injection at all load and speed conditions that would soon be essential. But for engines not designed for unit injectors, electronic control of a conventional pump was "a major step forward".
Moving from engines to complete drivetrain design for improved fuel efficiency, Peter Capon described the cvt (continously variable transmission) currently under development at Leyland. Its first application would be on buses because their low average speed, stop/start duty cycles were seen as offering the greatest fuel saving potential for the Leyland cvt.
It was disclosed that, in conjunction with BP, Leyland is conducting a study into a flywheel regenerative braking system on a cvt equipped bus. An experimental vehicle is already running.
Mr Capon concluded by describing some of the recent work Leyland had done (CM March 24, 1984) on improving the aerodynamic characteristics of articulated vehicles. The research was now concentrating on internal and cooling system airflow he said.
The DTp's Jim Clifton admitted to being a little uncomfortable at the prospect of presenting a paper on categorisation of vehicles at a fuel efficiency seminar. He saw the link between the two subjects as tenuous, though he acknowledged that "if the meaning of fuel efficiency is taken broadly as being the efficient use of the vehicle in its operating environment in relation to the amount of fuel used, then ... legal requirements play a significant role ...". He assured his audience that the DTp would be paying more attention to the subject in the future.
This theme was examined in some depth in the discussion which followed Mr Clifton's paper which outlined the major legislative categories — Construction and Use, ECE and EEC — which affect goods vehicles in the UK.
He was in no doubt that EEC and ECE categories would become increasingly important but he made no reference to harmonisation,.or rather the persistent lack of it, in the Common Market.
Joe Teirlynk, a Belgian journalist who had spent some time at last month's Brussels Show explaining his country's weight and dimension uplift (CM January 22) was determined not to let the DTp's representative get away lightly with that omission.
"Size and weight are not so important," commented Mr Teirlynk, "but harmonisation certainly is. If heavier vehicles are required, roads and bridges should be built to suit them."
Mr Clifton said there was a difference between 32.5, 38, 40 and 50 tonnes. "There must be an economic and enviromental cornprom'se," he said.
Joe Teirlynk was a little unhappy with compromises which put road transport at a disadvantage.
Kit Mitchell, head of vehicle engineering at the Transport and Road Research Laboratory, told the seminar of research which had revealed a strong trend in the UK over recent years away from small vehicles towards larger ones which were more fuel efficient. The implication was clear — Government could make a significant contribution to improved commercial vehicle fuel efficiency if its rules on size and weight were less restrictive.
John Ostle, transport engineering manager of BOC (Gases Division) followed up this general point with a specific example. "The DTp could help fuel efficiency by allowing drawbar combinations to operate at 38 tonnes," he said.
"I am not sure the case is proven that drawbars would improve efficiency at 38 tonnes", responded Jim Clifton, but he conceded that there were "environmental, not technical" reasons for limiting drawbar weights to 32.5 tonnes. "The general public perceives these vehicles as bigger and more dangerous than articulated vehicles," he said.
Jim Bodmer, president of High Technology Systems of Switzerland, opened his presentation with an apt quote from Lord Kelvin — "If you cannot quantify what you are talking about, you don't know what you are talking about."
He proceeded to talk, knowledgeably, about an integrated on-board system for measuring fuel efficiency and storing data which his company is developing in conjunction with BPW — the leading West German axle and suspension manufacturer. This was the system which was being displayed on the BPW-Marcar stand at last year's Birmingham Show (CM October 27, 1984). Though the heart of the system is a fuel flow meter, its capabilities extend to a lot more than simply measuring how many litres of fuel the engine has used.
The main thrust of Mr Bodmer's paper was that the total fuel efficiency of a commercial vehicle depends on many factors,
including gross weight, axle loads, and utilisation as well as simply fuel consumption. Fleet managers needed access to this data. His company's system provides it, stored on cassette tape, as well as giving the driver a comprehensive warning light display linked to sensors for brake drum temperature, brake pressure, braking efficiency, temperature of wheel bearings, tyre pressures, lamp functions and axle loads. A microprocessor also monitors road and engine speed, and fuel consumption.
But John So!tau of JPS Engineering, the Solihull based manufacturer of fuel flow meters was less interested in the full capabilities of the HTS/BPW system than in the method of operation of its flow meter. He questioned its accuracy and the affect it would have on engine performance, which he said was "inevitable with any flowmeter system which does not work at zero pressure".
Mr Bodmer was not prepared to argue over constructional details but he reaffirmed his confidence in the system's accuracy.
Terry Goldrick's paper introduced a facet of commercial vehicle fuel efficiency which had been almost ignored up to that point. He called it "the human element"; almost all the technological solutions which had been described earlier could be negated by human error during the vehicle specifying, operating, driving and maintaining processes.
He sub-divided his paper into four parts: the vehicle — getting the right vehicle for the job; scheduling — making sure the vehicle is used efficiently; maintenance — having a maintenance system that takes into account fuel related faults; and the driver — seeking an economical driving style. Bad driving can negate all the benefits on fuel economy achieved elsewhere.
Mr Goldrick described how nowadays vehicle manufacturers can help their customers in at least two of these areas. Daf's Topec computer based vehicle selection system was given as one example, while 'Scania (GB)'s recently introduced driver training scheme was used to illustrate the scale of fuel economy improvements that professional training can bring. Even allowing for the usual "fall back" which occurs sometime after training, Scania estimates that a 7-8 per cent improvement is normal.
One of Mr Goldrick's reponsibilities at FTA is the association's well established Inspection Services. Under the subject of maintenance, he produced some interesting statistics from an analysis of inspection reports. The sample was 485 vehicle inspections selected at random from the FTA's usual weekly national total of 2,500. The analysis revealed that 390 fuel related defects were contained in the 485 inspection reports with low and high pressure leaks from the fuel injection system as the two most frequently recorded fault areas in the list of seven.
Terry Goldrick's concluded from this analysis that "Unless there is a conscious effort to closely monitor vehicle condition; an awareness of the effects of fuel related faults; and maintenance to rectify such faults, then fuel will be wasted".
Chris Cernes, director of new products, Leyland Bus when called upon to summarise just before general discussion, made it plain that he had been paying close attention throughout the day's proceedings. He skilfully and succinctly highlighted the problem areas which "had received most attention in the papers" and pointed out some possible technological solutions to them. These were divided into two categories — vehicular and non-vehicular.
Included under the latter heading were lower speeds, more basic research and better vehicle specification. The former category included further development of the diesel engine including turbocompounding; better drivetrain matching; drag reduction; and weight saving.
With a remark that might have been directed at the UK government, Mr Cernes emphasised the importance of maximum gross weights. "Supertankers are very efficient", he said, "and they get more efficient as they get bigger. So do lorries, 13.9 per cent more efficient for example at 38 tonnes than at 32.5 tonnes."