• Due to process compulsions, to reduce boiler size and piping, steam generation normally happens at high pressure whereas usage happens at low pressure.
• The reduction of this pressure is done using a pressure reducing valve (PRV). The process in a PRV is isenthalpic and irreversible.
• The economic implication will be limited to brake efficiency and additional mass flow of steam which is proportional to work done. This typically works out to be Rs1 to 1.2/KWH generated.
• The isentropic efficiency will not affect the generation cost since the outlet of the expander is going to process.
• However, lower the isentropic efficiency lower the power generated and hence longer the return on investment.
• The present available technology cannot give high isentropic efficiency for the entire range of operation. However, it provides a useful alternative.

• The present invention relates to a mechanism for controlling admission volume (as shown in Fig. 1) of inlet gas for a fixed revolutions per minute (RPM) operation of a rotary or reciprocating expander.

SYSTEM

• The system has a boiler for generating a steam at a higher pressure for heating application in a process.
• A pressure reducing valve (PRV) controls a boiler pressure to process pressure.
• Inlet ports and exhaust ports are configured by intersection of opening on a rotor housing and opening on a rotating valve.
• The inlet ports are designed in such a way that a port opening duration can be controlled to admit required volume of a steam corresponding to a mass flow requirement of the process.
• A port capable of changing the area and timing of opening in such a way that the duration and starting of exhaust can be controlled.
• Higher part load efficiencies, the variation in isentropic efficiency in the entire range of operation can be within 10%. The pressure v/s rotation angle of Wankel expander (Fig. 2) demonstrates this.