Steam Locomotive Development

The success of the "Horatio Allen" and "John B. Jervis" higher steam pressure locomotives resulted in the Delaware and Hudson Railroad building the "James Archbald," as illustrated in Plate II, Figure I, and the "L. F. Loree" as illustrated in Plate II, Figure 2, each carrying 500 lb. boiler pressure; the first men tioned being equipped with combined cylinders, and the last men tioned being equipped with triple expansion cylinders, giving road service thermal efficiencies ranging from 10-5 to 12.5 per cent.

In Europe, the Schmidt high-pressure experimental ten-wheel passenger locomotive on the German State railways, which makes use of 855 lb. boiler pressure, is outstanding as an example of high efficiency. From the results, to date, of this locomotive, and its use of multiple pressure, super-heating and re-superheating, multiple expansion and feed-water heating and purification, it has been proven conclusively that high pressures are safe in operation, great fuel savings are effected, that the first are little more than the conventional pressure locomotive, and that the high pressure machine can be easily handled by competent locomotive engineers and engine-house and shop organizations. The German State railways built a second locomotive which makes use of 1,700 lb. steam pressure. These are, however, exceptional cases, and it is still debatable as to whether the increased weight and first cost necessary to steam pressures beyond 500 or 600 lb., in locomotive design, will be justified by the greater economy over what has already been obtained from the 350 and 400 lb. pressures in combination with multiple expansion. In 1928, for a locomotive having four pairs of coupled driving wheels, the Delaware and Hudson Company's Consolidation No. 1,401, "John B. Jervis," is the most powerful. For starting and acceleration up to 8 m. per hour, it develops a tractive power of 103,000 lb., above which speed it is reduced to about 85,000 lb., up to 10 or 12 m. per hour, when it is still further reduced to between 65,00o and 70,00o pounds.

The largest and most powerful steam locomotives in the United States are represented by the Mallet types. On the Kansas City Southern railway, Mallet articulated compounds of the 2-8-8-o type, carrying 250 lb. boiler pressure, have a tractive power in simple gear of 147,500 lb., and in compound gear of 122,500 pounds. When the tender truck booster is cut in, this produces an additional tractive power of about 13,000 lb. for starting and acceleration, thereby bringing the total up to about 160,00o pounds. The Virginian railway has in its service some of the largest steam locomotives in the United States. These are of the Mallet articulated compound 2-10-10-2 type, having a maximum tractive power of 176,000 lb. in simple gear, 147,200 lb. in corn pound gear and 108,000 lb. at a speed of 15 m. per hour. The modern American steam locomotive is quite deficient in super heating, as the conventional type of superheater brings the last pass of the superheated steam before it reaches the branch pipes to the steam chests, through the coldest part, or front end, of the boiler and the smoke-box, where the prevailing temperatures are usually less than that of the superheated steam. The possibility of preventing this waste and increasing the total temperature of the steam will make it advisable to use a different type of super heater in the future. The possibilities of utilizing the waste heat in the exhaust steam from the main engines and from the auxil iaries, such as the air brake pump, turbo-generator, booster engines and other appliances, and from the smoke-box gases, offer another probability for substantial increase in capacity and reduction in fuel. Various types of open and enclosed feed-water heaters and economizers, now being used on passenger and freight locomotives in the European countries and in the United States and Canada, have demonstrated that savings of from 6% to as high as 18% in fuel can be brought about in this manner. The development of a mechanically driven pump, whereby the operating power can be obtained from the main cylinders and which will reduce the steam requirements for pumping from about 8o lb. of live

steam per horse-power hour to from 16 to 20 lb., offers possibilities in this direction. The exhaust steam type of injector, as now de veloped, also enables substantial fuel savings, although these can be depended upon for operation with the exhaust steam only when the locomotive is running at a uniform speed of 6 m. per hour and more ; when the boiler pressure does not exceed 25o lb. and when the temperature of the feed-water does not exceed about 8o° F. The burning of coal and lignite in powdered form, in suspension, the same as oil or gas, has come prominently to the front during the past ten years. There were, in 1928, in the United States and Canada, in central power station and industrial use, about 65o stationary boilers, representing about 8,5oo nominal boiler horse-power, that are making use of powdered coal. Boiler capacities are being obtained of from 400 to 450% of the nominal ratings, and with combined boiler, furnace, superheater and econ omizer efficiencies of as high as from 90 to 92%, in terms of the heat value in the coal as fired, at between 125 and 275% of boiler rating. Progress is being made in marine service through the use of powdered coal, as well as on steam locomotives in America and Europe. One great advantage on railway systems using both coal and fuel oil is that when locomotives are transferred from the coal to the oil burning districts, and vice versa, it is not necessary to change the furnace and tender equipment to adapt them to the two fuels, and the method for firing the powdered coal or lignite is practically the same. The locomotive will have as great, if not more, an evaporative and superheating capacity with the solid as with the liquid fuel. (See COAL AND COAL MINING; PULVERIZED FUEL.) Steam Cylinders.—In Europe, the use of poppet valves as a substitute for piston valves is being brought forward, particularly in Austria, France and England. A few locomotives have also been equipped in the United States, but the applications are of an experimental nature, and the use of the piston valve in corn bination with a Walschaerts or some similar outside valve gear, even in combination with pressures as high as 500 lb., will no doubt be continued until the poppet valve in combination with an angular motion gear has conclusively demonstrated its ad vantages, both from an operating and maintenance standpoint as compared with the linear movement. In the use of steam, the general practice in the United States and foreign countries is single expansion cylinders. Recently, by limiting the maximum cut-off in these cylinders to from so to 75%, an effort has been made to increase the expansion of the steam, reduce the loss of heat and produce greater economy through the use of a shorter cut-off. Reduction in the loss of heat is accomplished by the compound, triple and quadruple expansion engine by expanding the steam in several stages, which reduces the range of tern perature in each cylinder and the condensation, when saturated steam is used, or waste of superheat, when superheated steam is used, but these multiple expansion engines have greatly increased the steam contacting cylinder and piston areas, and must be operated at relatively long cut-off. Furthermore, the counter flow use of the steam causes a great waste in heat. Therefore, the uniflow cylinder offers special inducements in locomotive practice. It has advantages over compounding in that the same results can be accomplished with shorter cut-off, and by the peculiarities of the flow of the steam in the cylinder. After enter ing the cylinder the steam does not retrace its steps, but con tinues to go forward from the point of entrance until it passes out, and in this way the steam in exhausting does not sweep the heat from the inlet port surfaces, nor from the cylinder heads. This method greatly reduces the cut-off, condensation and ex pulsion of heat with the exhaust, and enables the single cylinder non-condensing engine to excel in economy to a substantial degree the compound or any similar multiple expansion non-condensing engine.