SECTIONAL TRANSACTIONS.— G. 353 



Afternoon. 

 Visits to Works : — 



The Leeds Forge Co., Aimley and Newlay. — Railway rolling-stock construction. 

 Well House Foundry, Messrs. Joshua Buckton, Ltd. — Testing machines, heavy 

 machine tools, enveloping worm-gear. 



Tuesday, September 6. 



Prof. W. T. David. — The Efficiency of Internal Combustion Engines. 



The suggestions made in this paper are (i) that calculations of the ideal efficiencies 

 of internal-combustion engines should be higher than those usually made, and (ti) that 

 they increase with compression ratio at a greater rate than is generally supposed. 



(»') Experimental work has been carried out during the last few years at Leeds 

 in conjunction with Messrs. S. G. Richardson, W. Davies, R. A. Smith and B. H. 

 Thorp, upon explosions of inflammable gaseous mixtures contained in closed vessels 

 by means of flame photography and optical indicators. The experiments suggest 

 that the usually accepted values for the specific heats at high temperatures of gases 

 constituting the products of combustion are too high. The reason for this is that 

 specific heat values have been calculated from explosion experiments on the assump- 

 tion that the whole of the gaseous mixture has been burnt and is in thermal 

 equilibrium by the time that the maximum pressure is reached. The flame photo- 

 graphs, together with pressure measurements in explosions covering a wide range of 

 mixtures in which the proportion of H 2 or CO and 0., and N 2 were varied, show that 

 this assumption is not justifiable even in the case of those mixtures in which a large 

 excess of the reacting gas is present. The significance of this in connection with 

 internal combustion engines is that the ideal efficiencies calculated on the basis of 

 specific heat values deduced from explosion experiments are too low. 



Engine experiments by Mr. H. Ricardo support this view. He finds that the 

 measured thermal efficiency of an engine approaches too closely to the ideal value 

 calculated upon the basis of the generally accepted specific heat values to give one 

 confidence in the latter. 



(ii) Closed vessel explosions also show that for a mixture of any given composition, 

 the ratio of the maximum pressure reached on explosion to the initial pressure of the 

 mixture before explosion increases as the initial pressure is increased. I have 

 suggested that the causes responsible for this are (i) more complete combustion with 

 increasing density, and («) that the specific heats of CO., and water vapour at high 

 temperatures decrease with increasing density. 



Engine experiments by Messrs. Tizard and Pye are of interest in this connection. 

 They show that the thermal efficiency of an engine working on a mixture of any given 

 composition increases as the compression ratio increases to a greater extent than that 

 to be expected from their efficiency calculations which are based upon specific heat 

 values assumed to be independent of density. If, as I have suggested, combustion 

 becomes more complete in the early stages of the expansion stroke, and the specific 

 heats of the products of combustion at high temperatures decrease as the density 

 increases, the explanation is clear. 



Mr. H. R. Lupton and Mr. J. H. W. Gill. — Low-lift Axial Floiv and 

 Centrifugal Pumps. 



Mr. R. Borlase Matthews. — Transport on the Farm by the Aid of 

 Electricity. 



It is contended that agriculture — the largest industry in every country — must be 

 industriabsed if it is to be profitable. To attain this end transport must be done 

 electro-mechanically. In the field wagon loaders should be employed, and at the 

 barn the loads should be removed and transported in single lifts. Any redistribution 

 of the crops should be made by aid of automatic grapple forks. Chain conveyors 

 should supply the threshing machine, and mechanical or pneumatic conveyors should 

 carry away its products to granary, chaff room and straw barn. Thus the complete 

 threshing operation can be carried out with three or four men as compared with the 

 usual round dozen. With every electro-mechanical aid in the cow byres the work 



1927 A A 



