(6) For this engine all kinds of non fossil fuels including wood tips, plastic fossil fuels and pellet, and all biomes fuel and solar heat can be used.
(7) It fits well to ship uses, because condenser can be applied easily, then, high efficiency and good and clean working water circulation can be attained much better than land or car uses.
2. PRINCIPLE OF POWER GENERATION OF MARINE SSSE
For this engine, there are three cases, the one is single expansion with low-pressure steam, and the second is two or more stage expansions by high-pressure steam, the third is the case accompanied with a bottoming turbine. At Fig. 1 the illustration of basic principle of double expansion SSSE with single boiler and two burners and with one bottoming turbine and one condenser case is shown.
There are two stages Stirling engine type reciprocating steam expanders. PP1 and PP2 is power piston each in power cylinders.
DP1 and DP2 are displacer pistons containing stacked wire mesh heat regenerators RG1 and RG2 in each inside same as Stirling engines.
PP1, DP1, RG1 makes the first stage, and PP2, DP2, RG2 makes the second stage, and H1 and H2 are each stage's head Stirling type heaters heated by two burners or by any furnces just same as conventional Stirling engines. The two stages have 180｡?hase difference.
B1 is a boiler and its steam is furnished to the engine through a horizontal rotary valve RV, and it sends steam to each stage one by one with appropriate timing.
Steam is injected first into the bottom part of DP1 cylinder and steam expands in PP1 at high temperature after passing RG1 and H1.
On the return of steam from PP1, it goes outside at lower temperature after passing RG1.
Then steam is sent to the second stage by RV at lower pressure and works same cycle as the first one, MG1 is the main motor generator.
Exhaust steam from the second stage is expanded more by the bottoming turbine.
BT, and sent to the condenser which is cooled by outside water.
The turbine BT runs high frequency motor generator MG2, and both MG1 and MG2 motor generator move the screw motor in combination. So Fig.1 is a general sketch of one example of the principle of an electric ship propulsion system. There will be many variations in engine types.
At Fig. 2 an idealized p〜v diagram of this engine is shown, P1 is the input boiler pressure, and starting pressure of PP1. P2 is the input of the second PP2 stage, and V1 and V2 are the volume of each power pistons. Pa is the atmospheric pressure. X and Y are the p-v diagrams of both power cylinders. As seen there, the cycles of this two parts are the hybrid of Stirling and Rankine Cycle.
P3 is the input pressure of bottoming turbine BT, and Pc is the pressure of condenser. Z is the diagram of the bottoming cycle.
The thermal efficiency of this engine is just between Rankine and Stirling cycles. So, about 25 to 30% efficiency is hoped to be get at early stage. The power size range may be 20〜200KW.
Actually, by rough theoretical calculations, thermal efficiency becomes higher with higher temperature and pressure of boiler working steam, while smaller consumption of steam per KW, is attained. This means the ratio of Stirling cycle to Rankine cycle is hoped to be bigger to get higher efficiency.