Page images
PDF
EPUB

The temperature which may theoretically be obtained in a gas engine is, therefore, with this gas nearly 300° C. higher than when burned in the open air.

The following calculation of the temperature obtained from a carburetted water gas is an example of a more complicated

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

Using volumetric specific heats at constant pressure.

.8372 × sp. ht. CO2 at 1900° (=.706) = .5910
1.0876 x sp. ht. H2O at 1900° (=.588)
4.7565 x sp. ht. N at 1900° (.404)

[ocr errors]

= .6395

1.9216

[blocks in formation]

3.1521

673 B. T. U. per cubic foot (experi5990 calories per litre.

theoretical combustion temperature in

degrees C.

* The assumption is made that the unsaturated hydrocarbons are made up of ethylene and propylene in equal volumes.

[blocks in formation]

The following calculations are for a theoretically perfect blast furnace gas of 33% CO and 67% N2, volume of products of combustion .33 volume CO, and 1.297 N.

Using volumetric specific heats at constant volume.

33 X sp. ht. CO, at 1700° (= .584) 1.297 X sp. ht. N2 at 1700° (= .306)

Net heating value 111 B. T. U. per cubic foot.

[blocks in formation]

.1927

.3969

.5896

When considering the relation which these temperatures thus calculated bear to those actually obtained, we may take into account, first, the influence of dissociation of the carbon dioxide and water vapor at high temperatures. The extent of this dissociation has been summed up by Nernst in his Theoretical Chemistry from Le Chatelier's work as follows:

"In the smelting furnace the temperature only extends to about 2000° C. and the partial pressure of carbon dioxide only amounts to about 0.2 of an atmosphere; now, the carbon dioxide is decomposed only to about five per cent., whereby the capacity of the furnace for work is somewhat diminished, though not very much. With explosives, the temperature of combustion rarely rises above 2500° C. and never reaches 3000°. Inasmuch as the pressure of the carbon dioxide is here estimated in thousands of atmospheres, dissociation has no influence.”

It is not easy to assign any definite value to the influence of the other factors which prevent the attainment of the full theoretical temperature. The heat liberated never goes

completely to raising the temperature of the combustion. gases, but there are nearly always local points where the heat is almost entirely utilized in this way. In the case of a Bunsen burner flame, the highest temperature found by the author experimentally was 1780° C., while the temperature calculated was 1850° C. Though the calculated temperatures are always somewhat high, they afford valuable information. Some conversion factors.

I calorie 3.968 British thermal units.

I small calorie .003968 British thermal units.
I calorie per litre 112.36 B. T. U. per cubic foot.
I small calorie per litre .11236 B. T. U. per cubic foot.

I small calorie per litre I large calorie per cubic metre.

THE PRESIDENT :-Gentlemen, you have heard this very interesting and instructive address on gas engines by Mr. White. Are there any questions you would like to ask him?

MR. ALFRED E. FORSTALL (Montclair, N. J.) :—Mr. White stated that the reason why the efficiency of the blast furnace gas was greater than the efficiency of the water gas is that it can be compressed to a higher temperature. The point strikes me that it is not perfectly clear how the extra work of compression is compensated for. I think I would like him to explain that.

MR. WHITE-I have explained that in the paper. So long as you are considering an actual gas engine running, there will be a loss of work in compressing the gas; but if you consider there is no loss of heat in compressing the air or gas, which expands again, you will see that you will get all the work back. If you have a water jacket, and the gas has cooled off, of course there is some loss of heat. Of course, if you have the ten atmospheres of compression plus the seven atmospheres, there will be an actual pressure of seventeen atmospheres in the cylinder, but only seven atmospheres due to explosion of the compressed charge.

MR. W. CULLEN MORRIS (Long Island City, N. Y.) :-As I understand Mr. White, in comparing the several gases he

only compressed the blast furnace gas and not the carburetted water-gas. I ask him if the carburetted water-gas were compressed, would its efficiency be increased?

MR. WHITE-Its efficiency would rise. If the pressure is increased to five atmospheres, its explosion pressure would go up, I should say, to nearly nine atmospheres.

MR. HENRY L. DOHERTY (New York City) :-I want to congratulate the Association on taking up a matter which I believe is of the greatest importance in engineering work. I · have absolute faith in the future of the gas engine.

We have

a central station at Madison, Wis., which is now generating one-half of its current by gas engines. We have another at Long Branch which will generate more than half the current capacity of the station by gas engines. At Long Branch we have put in producer gas engines and intend to use producer gas. I think some of the reputable builders of producer gas machines and gas engines are now ready to guarantee if you do not make the guarantee too rigid—that they will give you a brake horse power for one pound of coal.

I have been interested in Mr. White's lecture. In the first place he gives the calorific value of blast furnace gas as I— by that I mean per cubic foot-that would mean practically no CO, and you do not get that efficiency in blast furnace gas. I understand the Koerting engines at the Lacka wanna Steel Works get gas of 18 B. T. U. per cubic foot, and it is hardly reasonable to suppose that the blast furnace gas there would contain as a maximum more than 70 and probably down as low as 50; because they would force the blast with the idea of getting a higher fuel economy without endangering their charge by the presence of free oxygen.

Mr. Donald McDonald in a remark just made to me compliments Mr. White on his curves. He says the only curves he could ever get for gas engines look like a mule kicking up behind. I do not get anything like that. I could not verify the figures given by Mr. White. I was rather surprised at the figures he put upon the blackboard, and was a little surprised at his statement of the increased temperature due to adiabatic compression, or nearly adiabatic compression, of ten

atmospheres. I am surprised that does not add more than 500°.

As a matter of interest I want to call the attention of the members to a publication by Mr. Humphrey, of England. It is a very comprehensive bit of literature-I do not know what you would call it-on large gas engines, and if anyone is interested in the subject they should look it up in that book, because our text books are behind the times as regards gas engines. The Diesel motor, which is the one called a rational heat motor, I do not think has been a success in this country. I understand they have been trying abroad to work a 100 horse power engine with crude oil, and it was a failure, and we have been anxious to hear more about it.

I was rather sorry that Mr. White did not touch upon the relation between the efficiency of the gas engine and the efficiency of the steam engine, and go into the reasons why both are limited, and why the gas engine has such wonderful possibilities. If we were to figure that we were limited to the flame temperature of lubrication, which most people think we are, the gas engine efficiency would not be as high as it is now; but we can retain a hot core of gas in the centre of the cylinder, and we cannot do it with steam; for as soon as steam condenses the hot core goes to the cylinder walls, and owing to the greater possibility in the gas engine it seems to me fitting the gas men should be much more interested in the subject of gas engines than they apparently are at present.

THE PRESIDENT :-Gentlemen, are there any further questions to be asked on this subject?

Mr. White, I wish to thank you in the name of the Association for your kindness in presenting this paper to us. We will now go into Executive Session, as there is some special work which we desire to take up.

(The meeting then adjourned to Executive Session.)

THE PRESIDENT :-We will now resume the open session. The next order of business is a paper by Mr. W. C. Morris, of Long Island City, N. Y., on "Notes on the Operation of Large Carburetted Water-Gas Sets."

(For paper see Appendix, page lxiv.)

« ՆախորդըՇարունակել »