Le renouveau du cycle de Rankine

Adaptations of the Rankine cycle to new applications are described. The first move has been to increase the efficiency of thermal generating stations operation on liquid fuels by using the combined gas turbine/steam turbine cycle. In these systems the steam produced is by the exhaust fumes of the high temperature gas turbine (1000°C). One has been able to increase the efficiency of the station to a very high value, ie 47% and it is expected that a figure of 50% is possible. There is also an attempt to use coal with these cycles by employing gasifiers. The second move has been to use binary cycles consisting of a Rankine water cycle for the high temperature side and a Rankine ammonia cycle for the low temperature side, the cycles being linked in cascade. These binary cycles enable one to: increase the maximum possible power for a given rotating speed of the machine, eliminate the problems of erosion which are encountered in low pressure steam turbines, and employ dry coolers by using low outside temperatures to the best advantages. The third line of research has been the adaptation of the Rankine cycle to producing mechanical or electrical energy from fairly low temperature heat such as recuperated heat or solar heat. After having pointed out system drawbacks in using water as the working fluid and the advantage of ammonia and fluorocarbon fluids, the report shows how to achieve the optimal cycle. A comparison is made between optimal cycles for NH3. R 11 and R 114. A description is given of a novel free-piston machine developed by D. Vokaer at the Institute for Applied Mechanics of the University of Brussels. The drive components of a Rankine cycle and the compressor of a refrigeration cycle are grouped in the same mechanical assembly. This system will produce refrigeration by heat from a fairly low temperature source (between 50° and 75°C). Performance curves are given for R 114 producing cooling at 10°C for a range of ambient and hot source temperatures. © 1982.SCOPUS: ar.j