Optimization of organic Rankine cycle power systems considering multistage axial turbine design

Abstract

Organic Rankine cycle power systems represent a viable and efficient solution for the exploitation of medium-to-low temperature heat sources. Despite the large number of commissioned units, there is limited literature on the design and optimization of organic Rankine cycle power systems considering multistage turbine design. This work presents a preliminary design methodology and working fluid selection for organic Rankine cycle units featuring multistage axial turbines. The method is then applied to the case of waste heat recovery from a large marine diesel engine. A multistage axial turbine model is presented and validated with the best available data from literature. The methodology allows the identification of the most suitable working fluid considering the trade-off between cycle and multistage turbine designs. The results of the optimization of cycle and turbine suggest that the fluid n-butane yields the best compromise in terms of cycle net power output, turbine cost and efficiency for the considered case study. When a conservative design approach is adopted, the turbine features a two-stage configuration with supersonic converging nozzles and post-expansion. Conversely, a single-stage turbine featuring a supersonic converging-diverging nozzle and Mach number up to 2 is the resulting ideal choice when a more advanced design approach is implemented.

One-Dimensional Annular Diffuser Model for Preliminary Turbomachinery Design

“…Macchi and Perdichizzi [3] Axial flow Fixed recovery a Lozza et al [5] Axial flow Fixed recovery a Da Lio et al [6] Axial flow Fixed recovery b Astolfi and Macchi [7] Axial flow Fixed recovery b Da Lio et al [8] Axial flow Fixed recovery b Al Jubori et al [9] Axial flow Not considered Talluri and Lombardi [10] Axial flow Not considered Tournier and El-Genk [11] Axial flow Not considered Meroni et al [12] Axial flow Not considered Meroni et al [13] Axial flow Not considered Meroni et al [14] Axial flow Fixed recovery b Perdichizzi and Lozza [15] Radial inflow Fixed recovery a Uusitalo et al [16] Radial inflow Not considered Rahbar et al [17] Radial inflow Not considered Da Lio et al [18] Radial inflow Not considered Pini et al [19] Radial outflow Fixed recovery a Casati et al [20] Radial outflow Fixed recovery a Bahamonde et al [4] Axial flow Radial inflow Radial outflow Not considered a Fixed recovery of the total kinetic energy. b Fixed recovery of the meridional kinetic energy.…”

“…Equations (10)-(13) pose a system of ordinary differential equations (ODE) that can be expressed more compactly in matrix form as given by Equation (14). The solution vector U, coefficient matrix A, and source term vector S are given by Equation (15).…”

A methodology for the preliminary design and performance prediction of high-pressure ratio radial-inflow turbines

“…The Monte Carlo method was applied using a numerical model written in the MATLAB language [57], which is documented in Ref. [74]. A uniform probability distribution without correlation control was used for the input calibration coefficients.…”

Simultaneous Cycle Optimization and Fluid Selection for ORC Systems Accounting for the Effect of the Operating Conditions on Turbine Efficiency

“…For a radial turbine, this typically involves optimizing six turbine design parameters, alongside the working fluid and cycle parameters. Examples of such studies include those by Bahamonde et al (2017) and Meroni et al (2018). However, the major disadvantage of these studies, particularly for preliminary sizing, is the complexity of the resulting model and optimization problem.…”