6. CARBON DIOXIDE EMISSIONS
Carbon dioxide emissions can be influenced by two parameters, efficiency of the process and the fuel choice, i.e. how much carbon there is in the fuel compared to hydrogen. The efficiency development of the four-stroke engines from the author's company can be seen in Figure 19. The graph shows the technical development of the products as well as the size effect. The medium-speed engine on the market with the highest efficiency has a bore of 640 mm (Figure 20). By increasing maximum pressure in the cylinder it is possible to gain a couple of per cents more in efficiency from the diesel process itself. Further steps will demand a combined cycle process (Figure 21). In a normal diesel engine the exhaust gas is pretty cold, and therefore in order to optimize the diesel combined cycle process the engine process must be changed to Hot Combustion (Figure 22). In this concept the piston top is uncooled as is the cylinder head flame plate, and a minimum cooling is applied to the cylinder liner. Exhaust valve seats are very efficiently cooled in order to ensure reliability of the components. This concept is full-scale tested in a test power plant with a 12-cylinder 460 mm engine and a 12-cylinder 640 mm engine. At this point in time 6000 running hours have been gathered, and the target is to release the technology this year. Figure 23 shows the author's company's target curve for CO2 emissions. The lower part of the fork represents the combined cycle technology.
7. CONCLUSION
The reciprocating engines with diesel processes or Otto processes or combinations of both are able also in the future to respond to the market demands for low-emission engines capable of operation on any kind of fuel which might be deemed feasible.
