Rankine Power System Research Articles

A Design Optimization of Organic Rankine Cycle Turbine Blades with Radial Basis Neural Network

In the present study, a 100 kW organic Rankine cycle is suggested to recover heat energy from commercial ships. A radial-type turbine is employed with R1233zd(E) and back-to-back layout. To improve the performance of an organic Rankine power system, the efficiency of the turbine is significant. With the conventional approach, the optimization of a turbine requires a considerable amount of time and involves substantial costs. By combining design of experiments, an artificial neural network, and Latin hypercube sampling, it becomes possible to reduce costs and achieve rapid optimization. A radial basis neural network with machine learning technique, known for its advantages of being fast and easily applicable, has been implemented. Using such an approach, an increase in efficiency greater than 1% was achieved with minimal design changes at the first and second turbines.

Energy and exergy analysis of combined power, methanol, and light olefin generation system fed with shale gas

Environmental problems and limitations of fossil fuel resources, especially crude oil, have intensified the importance of using cleaner and cheaper fuels besides enhancing energy conversion processes. Therefore, a novel power, methanol, and light olefin multi-generation system is designed and modeled in this paper. Chemical looping reforming, chemical looping combustion cycles, and Rankine power system are combined with methanol and light olefin production processes. The input fuel of the system is shale gas. The mass, energy, and exergy balance equations are applied for each system unit as a steady-state control volume to assess its thermodynamic operation. Then, the effects on the system performance of critical parameters are studied comprehensively. The results show that the necessary syngas can be supplied when 71.5% of the inlet shale gas is used in the steam reforming reactor of the chemical looping reforming cycle, and the steam to fuel ratio and carbon dioxide to fuel ratio are 0.61. Furthermore, if 31% of the produced methanol is consumed in the olefin production unit, the system energy and exergy efficiencies are achieved at 67.3% and 71.5%, respectively. In this case, the carbon dioxide flow rate is 800 kmol/hr, separated and stored in the chemical looping combustion cycle, leading to a clean thermodynamic system.

Design and manufacturing a small-scale radial-inflow turbine for clean organic Rankine power system

With growing on the energy demand and availability of the low-grade temperature heat source, the organic Rankine cycle as a power system can be efficiently utilized to generate electricity. The turbine design and its performance have the main impact on determining the system power and overall system efficiency. Therefore, design a small-scale organic Rankine system requires the development of an appropriate turbine. To achieve this aim, this work offers an innovative complete design method to develop a radial-inflow turbine for small-scale organic Rankine cycle power applications, which includes a preliminary design (i.e. one-dimensional design calculation phase) and a three-dimensional flow analysis using the computational fluid dynamic technique. A thermodynamic analysis of the organic Rankine cycle was integrated with the design methodology. Where the three-dimensional geometry model was built based on the thermodynamic and aerodynamic design, and then was imported into the ANSYS-CFX software to conduct viscous numerical simulations. The optimum design of the radial-inflow turbine was manufactured using a three-dimensional printing (pioneering) technique, and the experimental testing was conducted at off-design points to validate the turbine design.The evaluation of the turbine’s performance (efficiency and power) was presented under design and off-design points in terms of rotational speeds, expansion ratios, and inlet temperatures with five different organic fluids. The turbine numerical results showed that R600 as a working fluid has a higher predicted turbine efficiency of 78.32% and power of 4.8 kW with cycle thermal efficiency of 9.15% compared with 8.045% for R245fa. Depending on the experimental results at off-design points, the highest cycle thermal efficiency of 4.25% with a turbine efficiency of 45.22% was achieved. These results assured the precision of the proposed PD methodology at off-design points in making performance maps of the turbine.

Design and optimization of a novel cryogenic Rankine power generation system employing binary and ternary mixtures as working fluids based on the cold exergy utilization of liquefied natural gas (LNG)

A fundamental double-stage Rankine cycle system using the single-component working fluid in each stage for liquefied natural gas (LNG) cold exergy recovery is used as a base case in the present paper. An advanced scheme of three-stage Rankine cycle system with the cooling output part is then proposed and designed. A series of cases are simulated within the fundamental and the advanced system schemes by employing the single-component working fluid and binary or ternary mixture working fluids. To settle the optimization problem of the poly-stage system with the multi-component working fluids, the priority-oriented composition optimization is performed based on the Genetic Algorithm in the advanced three-stage system. The thermal efficiencies, the exergy efficiencies and the exergy analysis are conducted in all the cases. As a result, the performances of the thermal and exergy efficiencies rise from 3.5% and 7.16% in the initial case to 17.33% and 25.7% in the fully optimized case respectively. The heat transfer analysis and the parameter study of the pump outlet pressure of the working fluids in the advanced three-stage Rankine cycle system are presented. Furthermore, the economic analysis is conducted as well to evaluate the novel cryogenic Rankine power system for future engineering design.

A Thermodynamic Similarity Framework for Assessment of Working Fluids for Solar Rankine Power Generation

Numerous studies have compared the merits of different working fluids for use in Rankine power systems. Most often, however, these have considered a limited number of specific fluids for which the thermodynamic properties are known. In the investigation summarized here, the Redlich–Kwong fluid model was used to develop a thermodynamic similarity framework that can be used as a comparative model for evaluating the performance of Rankine cycle working fluids. This can be viewed as a reduced order model that, based on thermodynamic similarity, quantifies the characteristics of the working fluids in terms of a single dimensional coordinate space defined by the choice of critical temperature. The advantage of this framework is that it allows exploration of the performance advantages of working fluids for which full thermodynamic properties are not yet available. Predictions of the model for common fluids were examined and conclusions regarding optimal fluids for solar Rankine systems are discussed.

Modeling of a Magma Energy Geothermal Open Cycle Power Plant

We are currently investigating the engineering feasibility of drilling into an active magma body at a depth of roughly 5 km from the earth’s surface, establishing a downhole heat exchange region, and extracting thermal energy from the magma body by circulating fluid through this heat exchange region. In the present paper, we evaluate the overall thermodynamic performance of a conceptual magma energy system in which energy is added as heat to the fluid within the magma region and is converted to useful work in a power conversion cycle at the surface. Unusually high return temperatures and pressures may be available at the wellhead of such a circulating well. Investigated here is an open Rankine power system in which heated water from the magma well is circulated directly through a power conversion cycle. The downhole heat exchange region is established during the drilling process. As drilling proceeds into the magma, a solidified layer forms about the drilling tube due to heat exchange to the fluid. This solidified layer thermally fractures because of large temperature gradients between the cooled inner region and the heater outer region, thereby opening secondary flow paths. Two models of the downhole behavior have been used. In the simplest approach, denoted as the “infinite area model,” the water entering the pipe to return to the surface is assumed to be always at the temperature of the magma, independent of mass flow rate and other parameters. The other model is more detailed and the fractured heat exchange region is modeled as a cylindrical porous layer through which fluid flows vertically. The net power and other performance aspects for the systems are investigated in terms of various parameters, including the characteristics of the downhole heat transfer. It is concluded that the open Rankine cycle probably will not be appropriate for this application; however, the analysis provides the first insights into possible characteristics of this energy resource.

Combination solar photovoltaic heat engine energy converter

A combination solar photovoltaic heat engine converter is proposed. Such a system is suitable for either terrestrial or space power applications. The combination system has a higher efficiency than either the photovoltaic array or the heat engine alone can attain. Advantages in concentrator and radiator area and receiver mass of the photovoltaic heat engine system over a heat-engine-only system are estimated. A mass and area comparison between the proposed space station organic Rankine power system and a combination PV-heat engine system is made. The critical problem for the proposed converter is the necessity for high temperature photovoltaic array operation. Estimates of the required photovoltaic temperature are presented.