Turbocharged diesel still the best bet?
Page 40
Page 41
If you've noticed an error in this article please click here to report it so we can fix it.
Papers presented at symposium on performance or pollution give promise of gas-turbine viability, show that the battery 3lectric is no more efficient overall than the petrol-engined vehicle, that matched turbocharging provides multiple benefits and that the smaller diesel might benefit from turbocharging most of all )1/ Paul Brockington MIMechE DLC (Hons) BLMC engineer claimed at a sym)osium held in Southampton Uni7ersity on Wednesday that the gas urbine was a viable alternative to the hose! engine in spite of its "at present" tigher fuel consumption. But the case or the diesel with a matched turbo:harger, made by staff members of the nstitute of Sound and Vibration Reearch,was perhaps more convincing.
Called "Performance or pollution — t symposium on road transportation," he event was jointly sponsored by The nstitute of Fuel and the 1SVR and held Lt the University of Southampton.
Papers also included reviews of the role of the electric car in the energy crisis, of various aspects of pollution control relating to "alternative" power plants and of transport problems in urban planning.
For the gas turbine, Dr M. G. Hodskinson of British Leyland said that work was progressing with the Leyland Mk2 turbine, which had one heat-exchanger disc instead of the twin-disc arrangement of the Mk I. In lagged form the M k I had a noise level of 85dBA compared with a level of 88dBA when unlagged.
Favourable
After reviewing the favourable exlaust emission characteristics of the gas urbine, Dr H odskinson emphasized .hat modification of a diesel to enable it :o meet pollution requirements and to )perate at a low noise level without a xinsumption penalty would involve levelopment of variable-injection and .!xhaust-gas-recirculation systems and in increase in the cost of manufacture ind maintenance.
The fact that the turbine could burn a Nide-cut fuel had "obvious implica:ions in difficult fuel-supply con ditions". And because its efficiency was better than that of a cleaned-up petrol engine its consumption would be acceptable to the private motorist. Current development work was concentrated on improving the efficiency of the engine cycle, notably to cater for the requirements of hgv operators.
Dr D. Anderton and Mr V. K. Duggal of the 1SVR gave the results of investigations which had shown that a diesel with a matched turbocharger produced lower smoke, carbon-monoxide and hydrocarbon levels than a naturallyaspirated unit or an engine with an unmatched turbocharger, together with a better specific fuel consumption over part or all the operating range. Whether it was matched or unmatched a turbocharger reduced the noise level but the emission of oxides of nitrogen was not significantly effected.
The investigation covered engines of 74.6 kW to 2.61 kW (100 bhp to 350 bhp) and the results also indicated that specific emissions per litre were increased as the swept volume was reduced. There was therefore a greater need to control emissions in the case of smaller (direct-injection) automotive diesels than the emissions of big diesels, and unless recent developments such as the Perkins "squish-lip" combustion chamber enabled a socially acceptable diesel to be evolved, the type of small unit suitable for light commercial vehicles and cars would benefit to a greater extent by the application of turbocharging.
Comparing the efficiencies of internal-combustion-erkgined vehicles and battery electrics, MrJ. T. Griffith of the Electricity Council Research Centre said that they were about equal if estimates were based on losses following delivery of refined fuel to'the user of the first type of vehicle and to the power station in the second case and if allow ance were made for power absorbed b the vehicle transmission.
The overall efficiency range of petrol-engined van or car was 8 p( cent/ 13 per cent whereas the efficienc of a battery electric was 11 per cent/ 1 per cent. There did not appear a cleat cut case for either type of vehicle i terms of the fuel consumed aft( delivery and the eventual application c power to the driving wheels.
Looking into the future of a wid variety of power unit types, incuditi hybrids, Prof P. a Dunn of the Un versity of Reading compared the batter electric very unfavourably with th petrol-engined vehicle on the score th the former had an efficiency of 13 IN cent, if account were taken of electrict generation and storage, and the latter a efficiency of 20 per cent. Although th battery electric did not pollute th atmosphere the power station whic produced the energy it used could cams pollution.
R otaries
Referring to alternative power unit Prof Dunn maintained that the Wank( rotary engine was not a desirab development because of its lo' efficiency, whereas the Stirling had th efficiency of a diesel and occupied let space. In quantity production it woul cost 20 per cent more than the diesel. 1 had reached an advanced stage c development and production engint should be available by 1980, ft example from United Stirling c Sweden.
Mr J. A. Hoare and Mr D. Collins Ricardo and Co Engineers (1927) Lt also criticized the Wankel engine in paper on emission legislation an private cars and they particular] mentioned relatively high friction lossc as a cause of low efficiency. In a appraisal of two-stroke petrol engine: they said it might be possible to ove: come the charge-loss problem by the of direct injection and thus provide unit which operated at a low NoX 'eve and had a fuel consumption conparable to that of a four-stroke engine Although the paper presented by M A. J. Wilson of Hampshire Count Council mainly related to urba planning and road transport, he dealt 2' some length with alternative sources c fuel and described nuclear energy as th most insidious pollutant ever created b man. Any significant escalation c nuclear energy production would be ou of the question until scientists ha, discovered hoW to control an neutralize unwanted radiation.
On the subject of public v private transport, Mr Wilson said that policie: aimed at encouraging the greater use o public transport were unlikely to bt successful except in major urban areas Opposition to the cost of building nev roads and to their environmental impac was conditioned by response to existini traffic congestion and this made sucf policies unavoidable in these areas. A transportation study could take three oi more years to complete and cost up tc EV2m. Factors included the growth 9: real incomes and increases in the price o: fuel. Careful land-use planning coulc reduce the need to travel and improve transport efficiency, although it ww necessary to avoid infringement of the liberty of the individual to choose where he lived, worked, and had his leisure.
Pollution A paper on urban air-pollution trends and legislation, by Mr S. Wallin Warren Spring Laboratory, Stevenage included detailed comparisons 01 emissions from transport vehicles domestic premises, industrial and town. gas plants, petroleum refineries one power stations.
These comparisons showed, for ex. ample, that power stations were the chief offenders in production of sulphu: dioxide (50.2 per cent) and oxides o nitrogen (40.5 per cent) whereas trans port vehicles were the main culprits it the emission of carbon monoxide (48.", per cent) and were high on the list o producers of hydrocarbons (37.7 pei cent).
Next week: a report on the discussion