Abstract
The performance and design criteria of air powered multistage turbines are studied thermodynamically in this paper. In-house code is developed in the C++ environment and the characteristics of four-stage turbines with inter-heating are analyzed in terms of maximum thermal efficiency, maximum exergy efficiency and maximum work output over the inlet temperature range of 293 K–793 K with inlet pressure of 70 bar. It is found that the maximum thermal efficiency, maximum exergy efficiency and maximum work output are 62.6%, 91.9%, 763.2 kJ/s, respectively. However, the thermal efficiency, exergy efficiency and work output are not equivalent for the four-stage radial turbine. It is suggested that at low working temperatures both maximum exergy efficiency and maximum work output can be used as the design objective, however, only maximum work output can be used as the design objective for the four-stage radial turbine over the working temperature range in this work.
Highlights
Radial turbines have been widely used for small scale gas turbines, cryogenic expanders and automotive turbochargers because of their simplicity, low cost, relatively high performance and good installation features [1]
With total expansion ratio increasing, multistage radial turbines are urgently needed for waste heat and pressure recovery, solar thermal power and compressed air energy storage [7,8,9,10]
It is found that the maximum thermal efficiency, maximum exergy efficiency and maximum work output of the four stage radial turbine with inter-heating are 62.6%, 91.9%, and 763.2 kJ/s, respectively
Summary
Radial turbines have been widely used for small scale gas turbines, cryogenic expanders and automotive turbochargers because of their simplicity, low cost, relatively high performance and good installation features [1]. Extensive investigations have been made into single-stage radial turbines, including design methodology, thermodynamic analysis, internal flow and heat transfer, and optimization [2,3,4,5,6]. There is a need to investigate the multistage radial turbine in order to achieve both high expansion ratios and high performance. Internal flow and heat transfer in single stage and multistage radial turbines are similar, the stage matching and design criteria of the multistage radial turbine are more complex. A four-stage radial turbine with inter-heating will be analyzed thermodynamically by using the methodology based on both the first and second laws of thermodynamics, and the thermal efficiency, exergy efficiency and work output will be discussed in detail for a better understanding of the stage matching and design criteria
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