592 Professor W. E. Dal by [May 26, 



interval of time. In another experiment the mixture was diluted 

 with 1 part of hydrogen and 6 parts of air ; this caused delay in 

 the combination, which took six-hundredths of a second to complete. 

 In such diluted mixtures the energy has to be shared by all the 

 molecules which do not take part in the change. 



The engineer is faced with two problems : the problem of a too 

 rapid combustion, becoming a detonation, and the problem of a 

 combustion too slow for complete combustion at high speeds. 



In practice the turbulence and eddies caused by the rapid 

 admission of a charge through the narrow annulus of an open 

 admission valve results in quickening the rate of combustion, and it 

 is owing to this cause that the gas engine can run at speeds greater 

 than those corresponding to the measured rate of flame propagation 

 for an efficient mixture. Sir Dugald Clerk found a striking difference 

 in the area of indicator diagrams according to whether the mixture 

 was exploded immediately after the admission valve was closed or 

 whether it was exploded after precautions had been taken to damp 

 out the eddies. 



Among the problems arising from running internal combustion 

 engines at high speeds is that of torsional oscillations, and synchro- 

 nous oscillations. There is also the balancing problem. The four- 

 cylinder petrol engine is usually constructed so that it is perfectly 

 balanced for primary forces and couples, but gives the maximum 

 error for unbalanced secondary forces. At certain speeds a model of 

 this type suspended from springs will oscillate twice as fast as the 

 speed of rotation of the engine, while at the same speed and on the 

 same springs a model, balanced to eliminate the secondary forces, 

 will run steadily at all speeds. 



Other problems have also to be considered. Accurate records of 

 the pressure-volume relation in the internal combustion engine must 

 be obtained, and the difficulties are increased owing to the high speed 

 at which the cycles take place. The direct measurement of tempe- 

 rature is also a difficult matter, and there are various fuel problems. 



Sufficient has been said to show that the future of the internal 

 combustion engine is not settled ; it is full of problems requiring 

 continuous and laborious research. We may well ask what provision 

 has been made for this research. Before the war purely scientific 

 research on the internal combustion engine was focussed largely in 

 a Research Committee established by the British Association at the 

 Dublin meeting in 1908. This Committee was the only one of its 

 kind, and the work was carried on vigorously until the war under 

 the successive distinguished chairmen, Sir AVilliam Preece and Sir 

 Dugald Clerk. The Committee is still in existence. There is also 

 the Research Laboratory at Shoreham under the direction of Mr. H. R. 

 Ricardo, himself a distinguished scientific investigator. 



During the war official organisations have been established, and 

 now the Department of Scientific and Industrial Research provides 



