Equation-oriented methods for design optimization and performance analysis of radial inflow turbines

Brede A.L Hagen,Roberto Agromayor,Petter Nekså

doi:10.1016/j.energy.2021.121596

Brede A.L Hagen, Roberto Agromayor + Show 1 more

Open Access

https://doi.org/10.1016/j.energy.2021.121596

Copy DOI

Abstract

This paper presents methods for design optimization and performance analysis of radial inflow turbines. Both methods are formulated in an equation-oriented manner and involve a single mathematical problem that is solved by an efficient, gradient-based optimization algorithm. In addition, the comparison of the model output with experimental data showed that the underlying mean-line flow model accurately predicts the variation of mass flow rate and isentropic efficiency as a function of the pressure ratio, rotational speed, and nozzle throat area. Moreover, the capabilities of the proposed methods were demonstrated by carrying out the preliminary design and performance prediction of the radial inflow turbine of an organic Rankine cycle. The results indicate that the design optimization method converges to the global optimum solution, regardless of the start values for the independent variables. In addition, the performance maps generated by the performance analysis method are physically consistent and agree with general findings from experimental data reported in the open literature. Considering the accuracy, robustness and low computational cost of the proposed methods, they can be regarded as a powerful tool for the preliminary design and performance prediction of radial inflow turbines, either as a standalone component or as part of a larger system.

Highlights

The Rankine cycle using an organic working fluid, conventionally referred to as the Organic Rankine Cycle (ORC), is an attractive technology for power production from low-temperature heat sources [1]
Capra and Martelli [8] demonstrated that a design optimization that takes into account the off-design performance of the Rankine cycle can significantly increase the cost-effectiveness of the system with respect to a conventional design approach that only accounts for the system performance at the nominal operating point
We believe that the proposed design optimization and performance analysis problem formulations have some advantages that are worth highlighting: 1. The independent variables, constraints and the objective function are written in non-dimensional form

Summary

Introduction

The Rankine cycle using an organic working fluid, conventionally referred to as the Organic Rankine Cycle (ORC), is an attractive technology for power production from low-temperature heat sources [1]. The ORC is currently applied for power production from waste heat [2] and renewable energy sources such as biomass combustion [3], concentrated solar energy [4] and geothermal energy [5]. Despite these energy sources could provide a significant fraction of the world's power demand [6], the full potential of ORC power systems has not yet been realized because the specific investment cost of this technology is relatively high compared with that of conventional power plants based on the combustion of fossil fuels [7]. Capra and Martelli [8] applied the two aforementioned methods to design a combined heat and power Rankine cycle and showed that the former resulted in up to 22 % higher annual profit than the latter [8]

Methods

Results

Discussion

Conclusion