68 



PRESIDENTIAL ADDRESS SECTION A. 



alcohol gives a slight!}' higher thermal efficiency. It is a well- 

 known fact that an increase in the compression ratio in an inter- 

 nal combustion engine gives increased thermal efficiency. The 

 calorific value of alcohol being only about 3/5 that of petrol, it 

 follows that for equal efficiency the consumption of alcohol 

 musl; be correspondingly higher to give the same power. But. 

 by increasing the compression in the case of alcohol to an extent 

 impossible with petrol, the thermal efficiency may be so in- 

 creased that the consumj^tion becomes practically equal, that is, 

 the product of the calorific value and the thermal efficiency be- 

 comes about the same. In the United States tests, an indicated 

 thermal efficiencyof 26 i:^er cent, was obtained with ]ietrol, with 



Jmc. 42. — Arrangement «if petnil engine for testing alcohol fuel. 



compression pressure of 70 lbs., as compared with 39 per cent, for 

 alcoiiol, with a compression pressure of 180 lbs. To accom- 

 plish this result would, however, involve an engine designed 

 for high compression ; it would be unsafe to subject an ordinary 

 petrol motor to such high compressions, which would naturallv 

 increase the explosion pressures. 



.\bout two years ago a Johannesburg resident succeeded in 

 ])ro(lucing a petrol substitute, having alcohol as the base, which 

 api)ears to meet the requirements of a motor fuel. On the sug- 

 gestion of the (iovernment Mining Engineer, I carried out, a 

 }-ear ago. a series of com])lete efficiency tests with this fuel, being 

 associated in the investigation with Mr. Vaughan, the Chief 



