New Steam Technology
Page 27
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Could Revolutionize the Steam Road Vehicle
With the Adoption of Super-pressure and Forced Circulation, all Types Could be Operated on this Source of Power Derived from Home-produced Fuel
By David Brownlie
IT is not generally realized that the possibilities of steam propulsion for motor vehicles, including cars, have been revolutionized by the recent striking advances in steam technology represented by the forced-circulation superpressure steam generator, especially of the moio-tube variety.
Generators of this type are light in weight, can be built to suit almost any available space, and will operate without difficulty at pressures up to, say, 2,000-2,500 lb. per sq. in, and at .9501,000 degrees F. superheated-steam temperature.
There has, of course, never been any real reason Wliy Steam propulsion should not be a success and why we .should not have in Great Britain, say, 500,000 steam-propelled vehicles, not only coaches, buses, and lorries, but also cars. It will be remembered that in the period 1820-1850 there was developed in Great Britain a fair number of types of rteam road coach, which gave not unpromising results and-were already in commercial operation when the movement was checked by severe legislation.
19th Century Developments When the internal combustion engined vehicle, using petrol and alcohol, began to be a conertlercial proposition, after 1880, a considerable number of steam cars was produced and operated he France, Great Britain, and the United States, such as, for example, the Belle, De Dion, Locomobile, Ophir, Serpollet, Stanley, and White,
• So far back as 1865-1870, also, what May be termed the " modern " type of steam wagon was originated in Great Britain, and famous makers in this connection included Cla-yton and Shuttleworth, Ltd., Fodens, Ltd., Garrett and Cu . , Ltd., Leyland Motors, Ltd;, Robey and Co., Ltd., the Sentinel Waggon Works, Ltd., John I. Thomycroft and Sots, Ltd., and the Yorkshire Wagon Co., Ltd.
• It is well known that the steamer has again been .hounded off the roads by regulations, and to-day there are less than 1,000 at work, although not so many years ago the number exceeded 10,000. Their value in these days of transport difficulties would be considerable.
Later designs of steam wagon have boilers of what may be described as the vertical semi-locomotive type, operating at up to 259-300 lb. per sq. in. with. superheating, fired by anthracite or coke, either by hand or by mechanical stokers, and working in conjunction wikth compound reciprocating engines driving through a simple two-speed gear. The, results are excellent, and steam propulsion , has a number of obvious and ileportant advantages, including long life, freedom from breakdowns, good hill-climbing properties, low maintenance costs, low operating
costs, and, above all, that they use home-produced fuel. '
Naturally, however, it is an asset to be able to operate with steam at very high pressure, because to do so means smaller size and weight per unit of power output. In 1922 one, bf the greatest advances in the history of fuel and power was made by Mark Benson, who generated steam in narrow-bore steel tubes, with forced circulation of the water under actual " critical " conditions; that is, about 3,200 lb. per sq. in., and about 700 degrees F., although 'the arrangement included an extension of the tubes, forming a superheater, to give steam temperatures such as 850900 degrees F.
Under the critical conditions, water is converted into steam without change of volume; that is, without ebullition and the formation of steam hubbies.
A considerable number of Benson generators, for large power-station practice, is now in operation, but it was subsequently discovered that there was no need to work under the actual critical conditions and that pressures could be used, of, save 2,000-2,500 lb. per sq. in.
Big Advantages for Motive Plants Benson always had the idea, as he told me himself, that his generator represented particularly important possibilities for road vehicles and locomotives, as well as steamships, quite apart from stationary plant. So far as I am aware, however, no Benson generator has yet been used for motor vehicles or. even locomotives, although the advantages stand out a mile.
It should be pointed out that other pioneers before Benson recognized the vital importance of Super-pressure steam, especially when using unorthodox types of generator. Thus, Jacob Perkins, in the period 1820-1840, carried out some astonishing work in the use of steam at extremely high piessure, probably over 2,000 lb. per sq. in., whilst, about 1850, Martin Benson (no relation of Mark Benson) invented an advanced design of mono-tube forced-circulation generator which is similar to the modern La Mont device. After Benson there was developed, in 1922, a number of forced-circulation super-pressure steam generators, including the Atmos, Loeffler, Ramzin, Sulzer, and Velox, some of which are notably suitable for road transport. Both the La Mont and the Velox, of which the latter operates with combustion under pressure, have already been used to a limited extent for locomotives.
Apart from the Benson, none of the other well-known makes of super-pressure generator has yet been applied to the road motor, which, if there existed any adequate national, scheme for fuel and power, would undoubtedly represent one of their most important fields. Nevertheless, in spite of obstructions and difficulties, work is being carried out in
this connection. An example is the Doble steam vehicle, which ups a steel mono-tube generator, of about Fin. diameter (external) for the boiler and .f.-in. diameter (external) for the superheater and operates at about 1,000 lb. per sq. in, and 920 degrees F. It supplies a four-cylindered engine, having, in addition, on the most advanced lines, a double reheating between the engine stages.
Steamer Should Use Solid Fuel One of the main difficulties of the steam car, as distinct from larger vehicles, has been the fuel used for operating the boiler, which is mostly paraffin (kerosene) or similar medium petroleum fraction. Obviously, so far as Great Britain is concerned, the ideal practice is to wipe clean out the use of liquid fuel, in this connection, even if national scientific methods he adopted in conjunction with extensive low-teme perature carbonization of coal for the production of liquid fuel.
There seems to be "no reason why forced-circulation super-pressure monotube steam generators for road vehicles should not he operated with special high-grade solid fuel, such as that, for example, 'which is obtained by the lowtemperature carlaonization of briquettes made from well-washed, highgrade bituminous coal. Fuels of this kind, so far as concerns combustion, have peculiarly valuable properties, similar to charcoal, to which they are equal in fadiantheat emission, whilst being superior, because of their much greater density. When using washed coals, containing, say, not over 4-5 per cent, of ash, which is essential, the ash content of the briquetted smokeless' reactive fuels, although greater, is only about 6-7 per cent., which enables a high rate of combustion to be obtained, with no slagging difficulties.
The remarkable advances, made during the past 10-15 years in the production of alloy steels of very high heatresistiag properties, constitute also another matter of importance for steam propulsion. Moreover, in general, the conditions to-day are quite different from what they were, say, a quarter of a century ago.