MOTOR-CAR EXHAUST

New Zealand Times, Volume LII, Issue 12181, 4 July 1925, Page 18

MOTOR-CAR EXHAUST

CARBON DIOXIDE DANGERS. In his third and concluding Howard Lecture, delivered on May 4th, at the Royal Society of Arts, Professor Brame reviewed some of the problems upon which research is now concentrated. Tables and curves tie exhibited showed that there is little variation to the calorific values of the different kineb of fuel, petrol, benzol, alcohol, on the basis of weight. Purchase is, however, made on the volume basis, and the number of British therma. units produced by the combustion o? 1 gallon is higher for the denser than for the lighter fuels. But the possible .thermal units are not realised in a motor because combustion is not complete. Theoretically the fuel-air mixture should be so proportioned that, in the case of petrol, the exhaust contains about 14 per cent, of carbon dioxide. The usual mixtures are overrich; from experiments conducted bj the Bureau of Mines American motors 1 seem to work with an exhaust containing only from 7 per cent. to 12 per cent, of CO2. The advantages claimed are easier starting, better acceleration and greater power. But the combustion of over-rich mixtures must lead to the formation of carbon n onoxide and thus to low thermal efficiency. The late Professor "NY. Watson, who dealt with these problems in his. Cantor lectures of 1010, found that the presence cf 4.5 per cent, of carbon monoxide in the exhaust meant an efficiency loss of 20 per cent. In the recent American experiments good results were obtained with from 13.7 per cent, to 14.7 per cent, of 002. and the hiehest thermal efficiency was realised with an air-fuel ratio of 17.1. Professor Frame’s chief objection to weak mixtures was on account of thejr slow and uneven burning, especially vhen cold. put recommended for high thermal efficiency, i.c., good mileage per gallon warm weak mixtures, and for maximum pov.c* co«M strong Tmx* tures. Power had to be sacrificed to gain economy. As regards the danger from carbon monoxide poisoning, the experiments made in connection with the Brooklyn tunnel scheme and elsewhere proved that the dangers are verv real, evmi ill garages. The absorption of the CO by the blood is slow and varies individually, but 0.2 per cent, is dangerous because even the weak gas quickly makes a man helpless. In a closed of 1500 cubic feet capacity, 5 ant found tbat an automobile created in *or 10 minut-s an containing 0.5 pr cerr. to 0.7 per cent. °f 00. and Frefo<scnr Brame mentioned that (O prmr.ents havp onmtrred in garages over hero.— Engineering.