The First Airplane Diesel Engine: Packard Model DR-980 of 1928 Part 6

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.

[Ill.u.s.tration: 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 189 lb per min concentration

Boosted oxygen consumption, 32 per cent oxygen 289 lb per min concentration

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:

[1] Appendix, p. 43.

[2] Letter, Hermann I. A. Dorner to National Air Museum, March 3, 1962.

[3] See p. 20 ff.

[4] Appendix, p. 46.

[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.