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Aviation History
1924
1924 - 0688.PDF
out, exhaust gas will follow by the same route and fill the trunks, finally escaping into the atmosphere. This is all plain sailing so long as the airship is climbing or flying hori zontally ; if she dives at more than about 50 ft. per min. the whole supply of exhaust gas could not make up for the shrinkage, and it is necessary to admit air to the top of the airship again, either through automatic valves or by pumping it in from the slip-stream of the propellers in the usual way. It is argued by some that it is unnecessary to supply this gas protection, as a Zeppelin has already been struck by lightning in flight without harm, and the metal framework or net gives sufficient protection. That may be so but it does not provide for the case of spontaneous com bustion from oily waste left in the ring space, or from the accidental firing of a Verey light into the gas-bags, etc., which the layer of exhaust gas has been proved capable of doing. It only fails where a stream of incendiary bullets is concen trated on one spot from a machine gun, when hydrogen may be carried by the hose effect into the open air and ignited there ; but one does not expect to meet with a machine gun firing incendiary bullets at close range in a commercial ship. In any case I feel convinced of the importance of supplying inert gas to the exhaust trunks of the airship. Steps are now taken to see that an explosive mixture of hydrogen and air does not remain in the trunks, by scouring them with air, but as soon as a hydrogen gas valve is opened an explosive mixture must be formed. The hydrogen passing out into the atmosphere is a good conductor of electricity, and if any atmospheric discharge does travel down it, it is better that it should find a mixture of hydrogen and exhaust gas at the bottom than a mixture of hydrogen and air. Nothing would happen in the first case ; the second would involve a violent explosion in the trunk—which may account for the loss of the Dixmude. Having in mind the desirability of using the exhaust gas for protective purposes, let us glance further at the types of heavy fuel engines available. While the use of the Beardmore type engine removes our petrol trouble, it does not provide the greatest possible econony in running. In an airship, for every ton of liquid fuel consumed 33,000 cubic ft. of hycl.ogen have to be got rid of to keep the airship in trim. This hydrogen is a valuable fuel. In 1 lb. of hydrogen (which is about 190 cubic ft.) there are approximately 62,000 British thermal units compared to some 19,000 in 1 lb. of petrol. Previously it was necessary to blow this hydrogen into the atmosphere, and waste it, in order to keep the ship in trim. The Eastern Asiatic Oil Company and Mr. Ricardo carried the tests on with kerosene, getting the consumption down to 0-35 lb. per b.h.p. hour. Since then, by a slight modification in the original process, an engine has been run on gas oil. Using these heavy oils the engines will doubtless require frequent cleaning, but if they will run for 50 hours non-stop it is sufficient for our purpose. The engines should be specially designed for rapid dismantling. The War-time " May bach " was very good in this respect, it being possible to lift the cylinders in flight and have the engine running again within four hours, and this can doubtless be repeated. Under this system, using gas oil, we require 350 lbs. of liquid fuel, costing £1, and 5,000 cubic ft. of hydrogen, costing £1 55., total £2 5.9., per 1,000 h.p. per hour. Compare this with the cost of running on petrol alone, when the fuel for 1,000 h.p. hour would cost £5 17s., plus 7,000 cubic ft. of gas wasted, costing £1 15s., total £7 12s. A new process of using crude oil commercially has recently been introduced. This oil only costs 3$d. per gal., as com pared to 5d. for gas oil and lOd. for kerosine. I am not at liberty to describe the process as the inventor has not yet published his system. A plant using this process is working in London, so it has reached the practical stage. Suffice to say that crude oil is put into a generator which weighs about 50 lbs. for an engine requiring 60 gals, of fuel an hour. The crude oil is converted into gas, which is cooled and cleaned. If used in the ordinary engine without a supei- charger, 78 per cent, of the maximum h.p. is obtainable. The consumption is about 0-6 lb. per h.p. hour. Using hydrogen in conjunction with this gas, full power can be obtained from the engine, and the consumption drops to about 0-45 lb. per h.p. hour, so that for our 1,000 h.p. unit we should require 450 lbs. of liquid fuel, costing 14s. 7d., and 6,400 cubic ft. of hvdrogen, /l 12s., total /2 6s. 7d. 0 <$> R.A.F. Airman Rewarded ACTING FLIGHT-SF.RGT. J. S. BRETT, R.A.F., of Bircham Newton Aerodrome, Norfolk, was among several recipients of awards for bravery in saving life made on October 17 by the Society for the Protection of Life from Fire. Brett was presented with the bronze medal of the Society for his per 1,000 h.p. hour. Thus this process is not quite so economical as the last as regards cost, whilst the extra weight of liquid fuel required, which amounts to about a ton per 1,000 h.p, unit per 24 hrst) reduces the amount of paying load which can be carried. There are other possibilities of this process, however. It is customary for airships to carry about 10-15 per cent, of their total lift in the form of water ballast. Suppose we sub stitute crude oil. When it is required to use it as ballast, instead of throwing it overboard, we can make it into gas, which can be stored till required for use in the engines, and this gas is slightly lighter than air. We have thus got rid of our deadweight and yet have the fuel. The extra weight involved in this system is the generator, and diaphragms in two or three gas-bags to allow of the crude oil gas being stored there, replacing the hydrogen as used in the engines. A ton should cover the total extra weight involved in a ship like the Z.R.3, a sacrifice well worth making in view of the increased radius of action obtainable. Of course, this process of discharging ballast is slow, perhaps half a ton an hour could be reached, but in a sudden emergency the whole supply of crude oil could be discharged overboard, just like water ballast. Sudden emergencies should generally be dealt with by the use of swivelling propellers, which in my view should be fitted in all commercial ships. It is sometimes pointed out that as airships increase in size, the smaller proportionate horse-power is required to drive them at a given speed, and consequently the effect of swivelling propellers decreases as size increases, which is true. Nevertheless I think that they are always worth fitting for navigational and economic reasons. I believe we can meet with disturbed air, when rudders and elevators are little use, and if caught in down draught the ability to be able to apply the equivalent of 5 tons of ballast by means of your engines in a ship of the Z.R.3 type is most useful. The same effect could be got by dropping water ballast, but this can only be done a limited number of times, while swivel ling propellers can be applied as often as necessary. They are also available for ascent in a violent up-draught, when a ship might be carried up and lose a lot of irreplaceable gas. They are also useful for working down through low clouds when it might be dangerous to dive a long ship through them. On the economic side we can imagine a ship without swivelling propellers, lying at her mooring" mast with a full load and full of gas. Starting with a small initial lift she will put her helm up and force herself up to her safe flying height (which may be taken at three times the ship's length) by means of her engines and elevators. If we take this to be 2,000 ft., the ship will blow off 6 per cent, of her gas in so doing, which is entirely wasted. In an 80-ton ship this would amount to 158,000 cub. ft., cost ^39 10s. With swivelling propellers this gas need not have been taken on board, as no initial lift is necessary for leaving the mooring mast. In considering the design of commercial airships due weight must be given to the important question of working them with the smallest number of men, as this is of even greater import ance in the air than it is on the sea. Thus in British and German naval airships two men were allowed for each engine besides an engineer officer, and nine other officers and men. By simplification of design it should be possible to reduce this to one man per engine and an engineer officer ; one man looking after two engines in normal flight. Again, in the control car was a helmsman, a man for the elevator controls, and an officer for navigating, etc. In small airships one man could, and frequently did, perform all these duties for long periods. There is no reason why he should not do so in large ships if suitable relay gear is used for operating controls. Also we might follow the practice of some merchant ships and put our control position aft. In the streamline fins fitted in recent practice, ample room can be provided for rudder and elevator controls, so avoiding the long leads of wire and the necessary arrangements for taking up the slack. What is now wanted is some process of manufacturing hydrogen with the airship's own resources. Sitting on the sea there is plenty of hydrogen in the water around, if some reasonablv light electrolytic process can be found. Perhaps some system of cracking oil may meet our requirements, but it is a point that requires the earnest consideration of every aeronautical engineer who wishes to see the empire linked up by real commercial aircraft at the earliest possible date. <•> <5> courageous action on July 2 last whilst carrying out flying practice with anti-aircraft batteries. One engine of the machine caught fire and continued to burn. Brett climbed out on the wing with a hand extinguisher and sprayed the engine, keeping the flames under while the pilot dived and brought the machine to land. y^
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