38 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Feb. 



CORDES AND LOCKE'S ROTARY ENGINE. 



We have received a copy of a report by Mr. Josiali Parkes on the 

 merits of " Cordes and Locke's condensing rotary steam engine." Tl)is 

 engine is a contrivance for gaining power from thft momentum or im- 

 pact of steam, unassisted by its expansive force. Tlie apparatus is so 

 siin|ile, that tlie n.iture of it may be readily compreliended witliout a 

 figure : it consists of a vertical paddle wheel, revolving freely in a 

 cylindrical case, und each float or paddle in succession is exposed to 

 the action of a current of steam ru-ihing against it from a pipe enter- 

 ing the side of the cylindrical case tangentially ; so that steam im- 

 pinges perpendicularly on each float. 



The action may be compared to that of an undershot vfater-wheel, 

 except that the steam does not act on the floats at their lowest position, 

 but when they are about half-way between their highest and lowest 

 position. The cylindrical case opens into a condenser, so that the 

 steam may be said to flow from the boiler through the case into the 

 condenser, meeting the paddles in its course. The extremities of the 

 paddle-wheels do not quite touch the internal cylindrical surface of 

 the case, and the expansive action of steam is in no way employed. 



Mr. Parkes makes out that under these circumstances the steam 

 acts with, as nearly as possible, the same efficiency as in an ordinary 

 cylinder condensing engine. He arrives at this result in the following 

 manner: — 



" I must first state that this kind of engine precluded the employment of 

 the indicator to ascertain its gross power, as in ordinary cylinder engines; 

 and even if that instrument could have availed for the purpose, it was deemed 

 to be of far greater importance to measure tlie amount of force actually dis- 

 posable, as delivered off by the engine, rather than the power of the steam 

 in action, which alone is denoted by the indicator. To attain this end it 

 was necessary to fix upon some sufticiently uniform load to be applied to your 

 engine, as well as upon some method of determining the resistance overcome. 

 The load selected was a screw-propeller, submerged and driven round in a 

 tank of water, 16 feet by 11 feet square. Tlie resistance was weighed by 

 Mr. Davies'a dynamometer, adapted to a strap-pulley on a couater-shaft, 

 ivorking intermediate between the engine and screw-shaft. 



These preliminary arrangements having been made, the engine was worked 

 during several days; tlie quantity of water, as steam, which passed through 

 the wheel-case, as well as through the small auxiliary engine which drove 

 the air-pumps, being carefully measured on each occasion. The resistance 

 sbown by the dynamometer was continually noted ; the number of revolu- 

 tions made by tlie wheel was exhibited by a counter ; the pressure of the 

 steam as it entered the wheel-case, was observed on a thermometric steam- 

 gauge ; the value of the vacuum in the wheel-case was obtained by an ordi- 

 nary gauge communicating with it ; and the amount of power employed to 

 drive the air-pumps and maintain the vacuum, was ascertained by an indica- 

 tor. The diameter of the steam-wheel in question is 11 feet 7 inches, and at 

 602 revolutions per minute, its periphery travels at the rate of about 208 

 mdes per hour. The width of the wheel-case is 15 inches; the number of 

 vanes and radial arms 28 ; the breadth of each vane inches, the depth 7 

 inches, and the area, therefore, of each vane about 42 square inches. The 

 orifice of the steam jet is of an oval shape, 3 inches by 2 inches, set verti- 

 cally. 



It appeared, after a great number of trials, that your engine gave the fol- 

 lowing results, when using steam in the boiler at a pressure of 2| lb. per 

 square inch above the atmosphere : 



Rerolutions of wheel per minute .. 502 



Horses power per dyr.amumeler ., 32 



Viicmira in the wheel-caae .. .. 2"*'2 in. of mercury. 



Water expended per horse power .. 100 lb. per hour. 



The same dynamometer and strap-pulley were then transferred to your 

 works at Newport, Monmouthshire, and applied to a condensing engine 

 made by Messrs. Bowman and Galloway, of Manchester, having the follow- 

 ing principal dimensions, viz. : diameter of cylinder 30 inches, length of 

 stroke 5 feet. Previously to the experiments, the engine was put into the 

 best possible working condition. My indicator was applied to the cylinder ; 

 the dynamometer to the engine-shaft ; cards were taken during several hours 

 iif continuous work, under an uniform load; the index of the dynamometer 

 was noted down every five minutes ; the water consumed, as steam, was ac- 

 curately measured. The subjoined may fairly be cousidered to represent the 

 mean result of numerous trials : 



Speed of piston per minutd 

 Hiean pressure per indicator 

 l^Iean vacuum throughout stroke 

 Vacuum In condenser 

 Water evaimruted per hour 



The indicated power amounted, from the above data, to 48'73 horses ; and 

 the water expended for each horse power, per hour, to GC'CS lb. 



The dynamomeiric, or effective power, as denoted by the instrument, was 



220 feet. 



10-;t42 lb. per square Inch. 



lo-lwi 



2ti-5 in. of mercury. 



■illbi lb. 



32-29 horses ; and the water expended for each effective horse power, per 

 hour, was 100'5 lb. 



It hence appears that the power actually delivered ofl' by the cylinder en- 

 gine, was less than the gross or indicated power by 33'73 per cent. ; and, 

 that a similar useful effect was obtained both from the cylinder, and your 

 rotary engine, with the same expenditure of steam and fuel." 



Mr. Parkes had some years ago the misfortune to publish, in the 

 third volume of the Transactions of the Institution of Civil Enginttrs, 

 a paper calculating the power of steam engines, in a manner much 

 more amusing than instructive. The reader who is curious in sucli 

 matters may find in the second edition of the Count de Pam- 

 bour's Treatise on Locomotive Engines, an ample critique upon this 

 piper, and exposure of its errors. We are not going out of the way 

 in referring to this matter, because we can only conjecture Mr. Parkes' 

 present mode of calculation, by comparison with what he did in 1S40. 

 At that time he could not understand that the effect of a steam engine 

 depends directly and absolutely on the evaporation, and that it is ut- 

 terly impossible to compute the effect without having estimated nu- 

 merically the quantity of steam generated in a given time. Seven 

 years of subsequent experience have not much mended matters, for 

 the calculations now presented to us are evidently independent of the 

 essential consideration just stated. The "mean pressure per indica- 

 tor," or cylinder pressure is given, together with the quantity of water 

 evaporated per hour; but nothing is said about the boiler pressure. 

 Now, having given the quantity of 7i»a^er evaporated per hour, we 

 must know the boiler pressure, in order to calculate tbe quantity of 

 steam generated per hour; and this being known, we may calculate the 

 velocity of the engine from the work done, or the work done from the 

 velocity. By omitting, however, a single element of this computation, 

 the whole chain of reasoning is broken, and when Mr. Parkes tells us 

 that the "power actually delivered off by the cylinder engine was less 

 than the gross or indicated power by 33'73 per cent." we are entitled 

 to attribute the fault not to the engine but to his calculations. 



The principal assertion, that an equal effect was produced from 

 both kinds of engines, with the " same expenditure of steam and fuel," 

 does not anywhere appear to have been corroborated by direct ex- 

 periment. With respect to the expenditure of steam, we know that 

 that could not have been ascertained, because tbe boiler pressure is 

 not recorded: and if the expenditure of fuel in the cylinder and 

 the rotary engines had been compared, something would have been 

 said to show that in both cases it was consumed in firegrates of the 

 same form aud dimensions ; as otherwise the comparison would not 

 be a fair one. 



Another altogether different application of the rotary engine was as 

 an auxiliary to the common cylinder engine, by causing the steam in 

 its course from the cylinders of the ordiniry construction to the con- 

 denser to pass through a circular steam case with revolving paddles, 

 as before described. The experiments on the rotary engine so em- 

 ployed were as follows : — 



" One of the wheel or rotary engines, divested of its air-pump, condenser, 

 &c., is connected at your works with a common reciprocating condensing 

 engine, in the following manner. The steam wheel is placed near to the 

 cylinder of the condensing engine, in the same room, and is simply acted 

 upon by the steam discharged from the latter. It therefore stands interme- 

 diate between the cylinder and the condenser, and derives all the power it 

 gives off from the waste steam of tne condensing engine, in its passage from 

 the cylinder to the condenser. 



Each engine drives a perfectly distinct load in the manufactory, that is to 

 say, each drives sets of machines perfectly distinct, and in separate buildings ; 

 the power of the cylinder engine being given off to a main upright shaft 

 connected with one kind of machinery, and the power of the wheel engine 

 applied to a strap communicating motion to machinery at a distance. This 

 condition of things has existed in actual daily operation at the works for 18 

 months past. In order to arrive at tbe separate value of the effect produced 

 by each engine, and of their combined effect, the following methods of proof 

 were adopted. 



The usual loads were disengaged, and friction breaks were applied in such 

 manner as to balance the whole power delivered off by each engine. Indi- 

 cator cards were frequently taken from the cylinder engine ; each break was 

 placed under tbe separate management of an experienced mechanic, with 

 every provision to maintain uniform friction ; the water evaporated was mea- 

 siu-ed throughout the experiments. The results were. 



