It is not the purpose of this article to delve deeply into the debatable subject of Diesel-electric drive for auxiliary machinery on battleships. However an attempt will be made to correlate some of the data and opinions that have resulted from the past experience of certain engineering personnel.
On the West Virginia and Maryland were installed, for experimental purposes, two vertical 6-cylinder, single-acting, air-injection, 2-cycle, Busch-Sulzer Diesel engines, designed to develop 950 b.hp. at 350 r.p.m. Each engine is directly connected to a 400kw., d-c generator, which can supply power to the distribution boards similar to the auxiliary turbo-generators.
That a Diesel-electric plant under many conditions can produce power at less cost than the turbo-generators is generally conceded. But the present-day battleship auxiliary plant has many demands that are not met with volts and amperes, namely, evaporators, galley, laundry, heating system, icemaking, cold storage, etc. Some of these requirements can be and are satisfied by electricity, but at present it is general to supply the first three with steam. The making of approximately 15,000 gallons of fresh water per day requires a considerable heat supply not easily met by electrical power.
The Diesel engines of the Maryland are equipped with a water-tube type of waste-heat boiler designed for the dual function of a muffler and source of auxiliary steam. The boiler has not proved satisfactory for either purpose. Engine vibration has made it almost impossible to keep the casing tight and the maximum steam pressure generated has been about six pounds with a very low rate of flow. The faulty casing could be very easily corrected by a change of design; likewise it is believed a much greater boiler efficiency could be gained if means were provided for easy cleaning of the tubes. Exhaust gas temperatures have been found to vary with the load from 450° to 600° F. Since approximately 230 pounds of fuel oil are burned hourly, a considerable heat source is available, but only a fraction of that needed to produce sufficient steam to meet the desired requirements. The waste- heat boiler can be modified to accommodate a Mayflower burner which, together with the exhaust gases, could supply sufficient steam to meet all at-anchor demands during periods of low steam consumption, weekends, and from taps to reveille. If the ship is equipped with the usual electrical devices— ice machines, pantry-warming and bakery ovens, fresh-water heaters, air heaters, feed and fuel pumps, and other common auxiliaries—the steam demands will be reduced to the requirements of the galley, laundry, pressing shop, air pump, evaporators, and a few smaller units. Then the total steam consumption should be well within the capacity of the proposed boiler. No doubt one of the main boilers with 5,500 square feet of heating surface is operating less efficiently at such low rates, and in addition there is increased radiation loss due to the large surface area. Comparing fuel-oil consumption, when operating the Diesel generating set in conjunction with the steam plant and the steam plant alone, after correcting the oil- consumption of the two systems of operation for the difference in kilowatt-hour output and gallons of water made, we get approximately 1,600 gallons of fuel used by the Diesel plus steam plant as compared with 2,500 gallons for the steam plant alone, or a saving of about 35 per cent. The figures represent a 16-hour test with almost similar conditions of load for the other operating auxiliaries. Data are not available for making a similar comparison for the operation of the Diesel plant alone, using a waste-heat boiler with a Mayflower burner, but the author is of the opinion that the saving would exceed 15 per cent. However, the vessel employing this type of auxiliary power supply assumes the necessary hazard of an increased time requirement in making preparations for getting under way. In addition, fuel-oil consumption alone does not give a fair comparison, since the lubricating oil used and repairs required have been found to be higher for the Diesels. The ultimate result, however, affords an appreciable monetary saving when the Diesels are operated in conjunction with a main boiler or alone.
The rules for engineering performances assign a penalty of 0.125 per cent for failure of light and power. Due to the experimental nature of the Diesel engines as installed, this penalty has been justly waived when they are in operation. The department has considered that this work should be conducted with the authorized personnel and all expenditures to be met by the ship’s unchanged engineering allotment. For the past several years much interest has been shown by the engineering personnel of the Maryland in the Diesel installation, as it afforded the best opportunity for increasing the engineering score. Various problems have been solved and the occasional Diesel failures tended to keep the engine-room and Diesel personnel more alert. The dual installation permits the operation of one set at a time, thus affording the necessary overhaul periods for the idle Diesel engine and various steam units. It is conceivable that during battle auxiliary machinery derangements might be such as to reduce the electrical supply below requirements, thus establishing the military possibilities of the installation. Experience has proved the units to be of real value during dry-docking periods where direct current is not available.