3. Effect of Oxygen Boosting on Power and Weight
[From P. H. Schweitzer and E. R. Klinge, “Oxygen-Boosting of Diesel Engines for Take-Off,” The Pennsylvania State College Bulletin (April 1, 1941), vol. 35, no. 14, p. 25.]
Practical Conclusions
Airplanes require about one third more power during the take-off than in flight. In diesel-engined airplanes the size of the engine could be reduced by 25 percent by feeding oxygen into the intake air during the takeoff. Applying the results of the experiments to a transport plane, Fig. 31 shows the possible weight saving with various oxygen boosts. The curves are based on 6000 cruising horsepower and an estimated engine weight of 2 lb per hp.
For the take-off 8000 hp are necessary. To supply the additional 2000 hp, 200 lb of oxygen are fed into the intake air during the take-off. The volume of 200 lb of liquid oxygen is approximately 20 gal. Standard liquid air containers of 55 litre capacity weigh 75 lb. Therefore the weight of the oxygen and container is 350 lb while the possible saving in engine weight is 4000 lb. The weight per take-off horsepower is thereby reduced from 2 to 1.54 lb. The calculation is shown in Table 1.
| Figure 38.—Effect of Oxygen Boost on Power and Weight. (Cruising horsepower 6000, takeoff horsepower 8000.) |
Oxygen addition may be used for starting diesel engines. The raising of the oxygen concentration from the normal 21 per cent to 45 per cent was found to be equivalent to a raise of approximately 10 cetane numbers as far as starting is concerned.
Five per cent increase in oxygen concentration eliminated exhaust smoke completely.
Table 1
| Normal horsepower | 6000 |
| Take-off horsepower | 8000 |
| Normal fuel consumption | 0.4 lb per hp-hr, or 53.5 lb per min |
| Normal air consumption | 900 lb per min |
| Normal oxygen consumption, 21 per cent oxygen concentration | 189 lb per min |
| Boosted oxygen consumption, 32 per cent oxygen concentration | 289 lb per min |
| Oxygen to be supplied | 100 lb per min |
| Weight of 8000-hp engine | 16,000 lb |
| Weight of boosted 6000-hp engine | 12,000 lb |
| Weight of oxygen for 2-min boost | 200 lb |
| Weight of container for 29 lb of liquid oxygen | 150 lb |
| Net weight saving by oxygen boost | 3650 lb |
| Weight per horsepower, nonboosted engine | 2 lb |
| Weight per horsepower, boosted engine | 1.54 lb |
Footnotes:
[2] Letter, Hermann I. A. Dorner to National Air Museum, March 3, 1962.
[3] See [p. 20 ff.]
[5] Aeronautics (October 1929), vol. 5, no. 4, p. 32.
[6] The Packard Diesel Aircraft Engine—A New Chapter in Transportation Progress (Detroit: Packard Motor Car Co., 1930), p. 5.
[7] A memorial to Woolson who was killed in the crash of a Packard diesel-powered Verville “Air Sedan” on April 23, 1930.
[8] Packard Inner Circle (April 18, 1932), vol. 17, no. 6, p. 1.
[9] Aero Digest (February 1932), vol. 20, no. 2, p. 54.
[10] Letter, Richard Totten to National Air Museum, January 28, 1964.
[11] Instruction Book for the Packard-Diesel Aircraft Engine (Detroit: Packard Motor Car Company, 1931), p. 3.
[12] S.A.E. Journal (April 1930), vol. 24, no. 4, pp. 431 and 432.
[13] Letter, Richard Totten to National Air Museum, January 28, 1964.
[14] Letter, Hermann I. A. Dorner to National Air Museum, December 16, 1961.
[15] The National Aeronautic Magazine (April 1932), vol. 10, no. 4. p. 18.
[16] Aviation (May 1931), vol. 30, no. 5, p. 281.
[17] The Packard Diesel Aircraft Engine, p. 5.
[18] Instruction Book for the Packard-Diesel Aircraft Engine, p. 3.
[19] “Test of Packard-Diesel radial air-cooled engine,” Navy Department, Bureau of Aeronautics, Report AEL-335, July 13, 1931, Bu. Aer. Proj. 2265.
[20] Aviation (May 1931), vol. 30, no. 5, p. 281.
[21] Letter, Clarence H. Wiegman to National Air Museum, November 1, 1961.
[22] Letter, Dorner to National Air Museum, January 15, 1962.
[23] Letter, Hugo T. Byttebier to National Air Museum, October 20, 1961.
[24] Letter, Clarence D. Chamberlin to National Air Museum, February 8, 1964.
[25] Ruth Nichols, Wings For Life (Philadelphia and New York: J. B. Lippincott Co., 1957), p. 205.
[26] Letter, Richard Totten to National Air Museum, January 28, 1964.
[27] Letter, Richard Totten to National Air Museum, January 28, 1961.
[28] Aero Digest (February 1931), vol. 18, no. 2, p. 58.
[29] “50-Hour Test of Packard Diesel Aircraft Engine,” Packard Motor Car Company, Detroit, Michigan, serial no. 426, test no. 234-73, February 19, 1930.
[30] Blower in this sense refers to a low-pressure air pump (supercharger) designed to increase cylinder scavenging efficiency by blowing out exhaust gasses. In doing this it also increases somewhat the amount of fresh air introduced into the cylinders. Woolson invented a 2-stroke cycle blown engine; the patent was issued in 1932 (patent 1853714) with rights assigned to the Packard Motor Car Company. (Woolson himself died in 1930.)
[31] A 2-stroke cycle engine completes 360° of crankshaft rotation in what it takes a 4-stroke cycle engine 720° to accomplish. A 3-cylinder two-stroke cycle engine therefore has the same capacity to do work as a 6-cylinder four-stroke cycle engine. For this reason the former type of engine is both more compact and lighter than the latter type.
The above advantages, plus the increased efficiency of the blown 2-cycle diesel, are discussed in Flight—The Aeronautical Engineer Supplement (December 26, 1940), vol. 19, no. 11, pp. 545 and 552.
[32] Packard advertisement—Aero Digest (June 1930), vol. 16, no. 6, p. 23.
[33] Aviation (March 15, 1930), vol. 28, no. 11, p. 531.
[34] The National Aeronautic Magazine (April 1932), vol. 10, no. 4., p. 18.
[36] See Woolson’s patent 1794047, issued in 1931 and assigned to the Packard Motor Car Company. “An object of my invention is to automatically regulate the compression ratio in an engine inversely to the speed....” See also his patent 1891321, issued in 1932 and assigned to the Packard Motor Car Company. It describes a similar but nonautomatic system. Woolson therefore fully realized the disadvantages of the high cylinder pressures his engine developed at high rpm’s.
[37] Letter, Clarence H. Wiegman to National Air Museum, November 1, 1961.
[38] Ibid.
[39] Major George E. A. Hallet, U.S. Air Service, former director of engineering division, McCook Field, Dayton, Ohio.
[40] “Test of Packard-Diesel radial air-cooled engine,” Navy Department, Bureau of Aeronautics, Report AEL-335, July 13, 1931, BuAer Proj. 2265.
[41] Aviation Week and Space Technology (February 19, 1962), vol. 76, no. 8, p. 101.
[42] Aeronautics (October 1929), vol. 5, no. 4, p. 31.
[43] Letter, Richard Totten to National Air Museum, January 28, 1964.
[44] According to Frederic E. Hatch of the National Air Museum, it is possible that the engine failed because the fuel injectors became clogged. He notes that the airplane refueled at several fishing ports, and therefore must have used diesel oil set aside for fishing boats. This oil was generally quite dirty. As a result it was routine for the fishermen to have to clean engine oil filters frequently enroute. The oil filters of the Packard diesel could not be cleaned in flight.
Transcriber’s Notes:
Other than the corrections noted by hover information in the text, printer’s inconsistencies in spelling, punctuation, and hyphenation usage have been retained.