264 ENGINE TESTS. 



from the motor is not properly utilized, it may be so great 

 as to largely offset the economy otherwise resulting from the 

 use of the condenser. 



The tests furnish some data as to the economy produced by 

 a condenser in compound engines. In Engine No. 33, with 

 practically the same load, the use of the condenser reduced 

 the consumption of steam per I. H. P. per hour from 22.53 

 Ibs. to 18.92 Ibs., or 16%. In Engine No. 45, the use of 

 the condenser, with a nearly constant load, reduced the con- 

 sumption from 23.24 Ibs. to 16.07 Ibs., or 31%. A compari- 

 son may be made between Engines 41 and 42. The latter 

 (42 B), running non-condensing, used 25.2 Ibs. per I. II. I*, 

 per hour ; and the former (41 Bj, running condensing, used 

 19.1 Ibs. The reduction due to condensing here is i' I . 

 Engine No. 46, which is run non-condensing, mav be com- 

 pared with Engine No. 48, which is run condensing, making 

 allowance for the difference in the condition of the steam. 

 In this instance the condenser appears to have leduced the 

 feed-water consumption about :> > (| ', . In all these no account 

 is taken of the steam used by the condensing apparatus, the 

 percentages given being the gross savings. Throwing out Kn- 

 gine No. 33, which may he regarded as of special design, and 

 possibly not useful for general comparison, it appeal's that tin- 

 effect of the condenser on the compound engines is considerably 

 greater than in the case of the simple engines. It will he seen, 

 however, that the advantage of the condenser in compound 

 engines depends largely upon the boiler pressure; and a com- 

 parison made on an engine like No. 41, which is running at lo<> 

 Ibs., would show very differently from what it would in an en- 

 gine like No. 54, for example, which is run at 167 Ibs. The 

 effect of the vacuum on the low-pressure cylinder is much more 

 telling when the boiler pressure is low, and less work is done 

 in the high-pressure cylinder, than it is when the boiler pressure 

 is high. 



At pressures ranging between 120 and 140 Ibs., it would 

 appear from these records that a 4- valve compound engine run- 

 ning non-condensing would use not over 21.5 Ibs. of feed-water 



