This paper presented an off-design framework of gas turbine (GT) and its corresponding waste heat recovery system (WHRS) composed of a heat recovery steam generator (HRSG) and an organic Rankine cycle (ORC). Two different GT control strategies named turbine inlet temperature control (TITC) and inlet air throttling control (IATC) methods were chosen, as well as a novel combined IAT-TITC method was proposed. The CHP system was optimized based on the maximum thermal efficiency first at GT full-load conditions. Then, the off-design evaluation was conducted to predict the part-load conditions and system performance. Results showed that the novel proposed IAT-TITC method effectively increased the thermal efficiency during the entire part-load conditions, and could avoid the low temperature exhaust gas phenomenon. The maximum efficiency difference between traditional TITC and new IAT-TITC was about 13.78% at half-load conditions.
Keywords CHP system, Off-design analysis, Gas turbine control strategy, Organic Rankine cycle