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Aviation History
1939
1939 - 0226.PDF
SUPPLEMENT TO FLIGHT JANUARY 26, 1939 THE AIRCRAFT ENGINEER TABLE 1. COMPARATIVE FIGURES (AT 39.5 FT. PER SEC. MEAN PISTON SPEED) FOR PETROL AERO-ENGINE AT 35 IN. OF HG. INDUCTION PRESSURE AT 12,000 FT., AND FOR FOUR-STROKE C.I. AERO-ENGINE AT 1,000 LB. PER SQ. IN. MAXIMUM COMBUSTION PRESSURE. Bore and Stroke. mm. 158 147 137 129 "3 No. and Arrange ment of Cylinders. 12 V 14 2-R 16 X r6H 18 2-R 24 X 24 H Frontal Area. sq. in. 820 1,720 i,33o 1.130 i.55o 840 79o Weight, lb. Petrol Engine. 1.450 1,410 1,560 1.37° 1.350 1,410 CI. Engine. 1,710 1,670 1,820 1,630 1,610 1,670 Power at 12,000 ft. H.P. Petrol Engine. 1,000 1,000 1,000 1,000 1,000 CI. Engine. 1,050 1,05a 1,050 1,050 1,050 Weight per h.p., lb. Petrol Engine. i-45 1.41 1.56 J-37 i-35 1.41 CI. Engine. 1.63 i-59 i-73 i-55 1-53 I.59 Frontal Area per h.p. (Petrol Engine). sq. in. .82 1.72 133 I-I3 1-55 .84 •79 Power of the CI. Engine at S.L. h.p. 1,500 1,500 i,5°° 1,500 1,500 Weight of CI. Engine per h.p. at S.L. lb. 1.14 1.11 1.21 1.09 1.07 1.11 Frontal Area of CI. Engine per h.p. at S.L. sq. in. •55 115 .89 •75 1.03 •56 53 output of a C.I. engine at 30 lb./sq. in. boost and 1,000 Ib./sq. in. maximum pressure, with no cooling of the air supply, should be about 5 per cent, higher than that of a petrol engine at 3 lb./sq. in. boost, provided that the piston speed is the same in both cases (39.5 ft./sec). At sea level the power output of the C.I. engine should be higher by 50 per cent, than that of the petrol engine at 12,000 ft., the induction pressure being brought up to 40-45 Ib./sq. in., excess air coefficient and maximum combustion pressure being kept as before. Fuel con sumption of the C.I. engine should be in both cases (i.e. at 12,000 ft. and at sea level) about .425 lb./b.h.p. hour. So far as maximum pressures are concerned, it should be possible to obtain at 12,000 ft. a not much lower power output than at sea level by increasing the boost pressure up to the same value of 45 lb./sq. in. But temperatures would be too high, and the use of an additional super charger, either mechanically or turbine-driven, could scarcely be avoided. At any rate, temperatures could be 'owered and power output further increased considerably, not only at altitude but also at sea level, by the use of a cooler. Provision of the additional mechanically-driven supercharger should be a simple affair, resulting only in somewhat worse fuel economy. With regard to some 50 or more per cent, power increase at 12,000 ft., the pro vision of a cooler and an additional supercharger would probably be worth while, in spite of the somewhat increased weight, drag and fuel consumption. As may be seen from Table 1, the ratio of frontal area to power output would be lower in case of the C.I. engine, but the weight : power ratio would be somewhat higher, if the comparison is made at 12,000 ft., though considerably smaller at sea level. At any rate, as was mentioned above, provision of a cooler and of an additional supercharger could increase the power at altitude to such an extent that the weight: power ratio would decrease substantially. Finally, it is to be noted that increase of permissible mean piston speed and maximum combustion pressure, better cooling, improvements in fuel quality and perfection of general layout would improve the performance of the C.I. engine with low C.R. no less than of any other type of internal combustion engine for aircraft. Therefore the relationship between the four-stroke C.I. engine with low C.R., the ordinary four-stroke C.I. engine, and the petrol engine (so long as the combustible mixture is compressed in the cylinders) should remain the same as at present. REFERENCES. 1. v.d. Null, Die Gestaltung von Flugmotorenladern, Jahrb., 1937, d. deutsch. Luftfahrtforsch., II, pp. 143-164. 2. E. G. Whitney and H. H. Foster, The Diesel as a High-Output Engine for Aircraft, S.A.E. Journ., Vol. 42, No. 4, pp. 161-169 (April, 1938). 3. F. A. F. Schmidt, Thermodynamische Untersuchungen uber Abgasturbo- aufladung u. grundsatzliche Versuche an einer Abgasturbine, Jb., 1937, d.d. Lff., II, pp. 31-35. 4. M. Scheuermever, Leistungssteigerung von Dieselflugmotorea, Jb., 1937, d.d. Lff., II, pp. 43-47. 5. O. Kutz, Forschungsaufgaben u. Gestaltungsfragen bei Steigerung der Triebwerksleistung, Jb., 1937, d.d. LJj., II, pp. 11-19. Effective Degreasing CALLED by the picturesque name of " Gunk D.P." solu tion a very effective degreasing agent is now being marketed by Brown Brothers, Ltd. . Judging by the effects of a sample when applied to a par ticularly messy part of a car, we are fully prepared to accept the claims made for the solution. It is simply brushed or sprayed on to the greasy surface, when it at once converts the grease to a thin, black soapy liquid which can be completely hosed or washed away with cold water, leaving the metal without even an oily film. It is also claimed that the solution is harmless to fabrics, non-corrosive and safe to handle, and it is stated that it is being extensively used by transport undertakings, etc. It retails at 5s. 3d. per gallon drum, or at an attractive price in bulk. A Paper on Alloys REPRODUCED in the current Journal of the Royal Aero nautical Society is a paper read before the Manchester branch by Mr. F. R. C. Smith, B.Sc., A.F.R.Ae.S., of the Northern Aluminium Co., dealing with the uses of aluminium alloys in aeroplane construction from the practical workshop point of view. The paper deals briefly with the mechanical properties of the low-, medium-, and high-strength alloys in the form of sheet castings, extrusions and forgings, and indicates the rapid advances which have taken place in the development of these products, while attention is given to the many problems which arise during their use, and indicates close collaboration be tween the manufacturers of these products and the users. A.R.P. Shelters B ELL-SHAPED "Consol" armoured A.R.P. shelters for protecting key personnel on duty in factories, etc., are described in a leaflet issued by Constructors, Ltd., Nickel Works, Erdington, Birmingham, 24. They are made in sizes to accommodate from one to four men. A Non-inflammable Paint L AST week a member of the staff of Flight was present at a private demonstration of what is claimed to be a non- inflammable paint. The inventor is a Dutchman. Lighting a strong gas jet, he first held in it pieces of fabric and wood covered with ordinary paint, and, of course, they at once flared up. Then he put into the flame similar pieces painted with his solution. The flame burnt through them, but did not spread, and the moment that the piece was withdrawn from the jet all smouldering ceased at once. The inventor claims that his preparation can be economic ally added to any form of paint, including aircraft finishes, and will not affect the colour in the slightest. Further develop ments will be awaited with interest.
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