Over the years, a variety of stored chemical energy, motion producing systems have been proposed. Frequently, but not always, such systems have been intended for use in providing the propulsion for a naval torpedo. In the usual case, chemical reactants are combined to generate heat which in turn is utilized to generate steam to power a turbine or the like.
Initially, such systems employed open cycle Rankine apparatus including a turbine and which essentially required that spent steam be dumped overboard. When used in a torpedo, a number of disadvantages resulted. For one, the torpedo was relatively noisy as the spent steam was discharged. Secondly, in some instances, the gaseous material being dumped would leave a visible trail highlighting the path that the torpedo was taking.
Thirdly, because the spent steam had to be dumped under water, the pressure against which the steam was being dumped would vary depending upon the running depth of the torpedo. Thus, the rate of propulsion of the torpedo was sensitive to the depth of operation.
In order to avoid these and other difficulties, closed cycle Rankine apparatus or the placing of the power plant in a pressure hull were proposed. Such systems, rather than dumping spent steam from the turbine, condensed the steam and recirculated it to the boiler for re-use or contained it within the pressure hull. As a consequence, noise and gaseous trails associated with steam charge were eliminated. Depth sensitivity was completely avoided.
However, in reverting to closed cycle Ranking apparatus, a new difficulty is encountered. It is the inefficiency in operation of Rankine cycle apparatus associated with the presence of non-condensibles, typically air, in the working fluid flow path of the apparatus. In particular, at the operating temperatures of such apparatus, the much lesser sensible heat of non-condensible gases such as air as compared to steam substantially lowers efficiency.
Where stored energy systems are being utilized in torpedos and employ closed cycle Rankine power plants, evacuation of the system upon manufacture is not practical since the torpedo may be stored for a considerable period prior to use and leakage may occur. Other methods of ridding the system of non-condensibles as may be employed with conventional boiler systems are not satisfactory.
Torpedos optimumly require operation at full power immediately at start-up. Thus, to avoid the inefficiencies associated with the presence of non-condensibles that would prevent utilization of full power at start-up, the non-condensibles must be removed extremely rapidly as part of the start-up sequence.
Moreover, because of the typical storage of torpedoes for a considerable period of time prior to use, it is undesirable to charge the Rankine cycle apparatus with the working fluid at any time prior to start-up. Corrosion can conceivably be a problem over a period of extended storage and leakage of the working fluid from the Rankine cycle apparatus would create inefficiencies. Consequency, it has been typical to store the working fluid in a reservoir until start-up is required. In the usual case, a pressurized gas is applied to the reservoir which then pressurizes the working fluid, typically water, out of the reservoir and into the Rankine cycle apparatus.
While this approach to charging the Rankine cycle apparatus with working fluid has been satisfactory, a fair quantity of gas under pressure must be stored on board the torpedo for ultimate use in charging the Rankine cycle system. The container for such gas is necessarily of substantial strength and consequently is relatively heavy. Desirably, the weight of this container could be reduced.
The present invention is directed to overcoming the previously mentioned difficulties.