scholarly journals Numerical Analysis of the Rotor of a 30 kW ORC Microturbine Considering Properties of Aerodynamic Gas Bearings

2020 ◽  
Vol 22 (2) ◽  
pp. 425-436
Author(s):  
Łukasz Breńkacz ◽  
Grzegorz Żywica ◽  
Małgorzata Bogulicz
Keyword(s):  
Rotational Speed ◽  
Dynamic Properties ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Geometrical Parameters ◽  
Gas Bearings ◽  
Lubricating Film ◽  
Working Medium ◽  
Optimal Dynamic ◽  
Free Machine

AbstractThe paper focuses on the analysis of a 30 kW microturbine operating in the organic Rankine cycle (ORC) with a low-boiling working medium. The nominal speed of the rotor is 40,000 rpm. The investigated microturbine is an oil-free machine, which means that its bearings use the ORC working medium as a lubricant. We created a numerical model, which was used to assess the dynamic properties of the newly designed microturbine. The conducted analyses covered, inter alia, the optimization of some geometrical parameters of each bearing in order to cause the lubricating film to be created at a correspondingly low rotational speed as well as to obtain optimal dynamic properties of the system. The article provides a full dynamic picture of the rotor supported by two aerodynamic gas bearings. The included graphs demonstrate the vibration amplitude of the shaft as a function of the rotational speed as well as the results of the modal analysis in the form of natural vibration modes of the system and their corresponding natural frequencies.

scholarly journals New Start-up Method for a Closed-Cycle Compression System with Gas Bearings and Its Characteristics

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Huaqi Lian ◽  
Hong Wu ◽  
Yulong Li ◽  
Chengjun Rong
Keyword(s):  
Rotational Speed ◽  
Load Capacity ◽  
Initial Pressure ◽  
Frictional Resistance ◽  
Closed Cycle ◽  
High Rotational Speed ◽  
Compression System ◽  
Gas Bearings ◽  
Start Up ◽  
Working Medium

AbstractGas bearings, which have the advantages of low frictional resistance and power loss, high rotational speed and high temperature operation, and long life, are more suitable than are traditional liquid lubricated bearings because of their high precision, high rotational speed, and special condition support. However, the problem of starting a closed-cycle compression system with gas bearings still needs to be solved for practical application. Thus, a new start-up method for a closed-cycle compression system with aerostatic gas bearings is proposed in this paper. Further, this paper presents a numerical simulation and experimental investigation of the method’s feasibility and characteristics during the start-up process when the gas tank’s initial pressure is fixed. The results show that the gas tank volume is approximately directly proportional to the start-up time allowable, and a gas tank volume sufficiently small, which not only ensures the feasibility of start-up, but also affects other components only slightly, can be obtained. A perfect combination of radial and axial loads also can be achieved to make the start-up time allowable as long as possible. R134a is a better choice for the working medium than is air, as the start-up time allowable is longer, which leads to a smaller gas tank. This research proposes a new start-up method for a closed-cycle compression system with aerostatic gas bearings which has sufficient load capacity to support system during the start-up method.

Performance Evaluation of a Turbine Used in a Regenerative Organic Rankine Cycle

2012 ◽  
Author(s):  
Maoqing Li ◽  
Jiangfeng Wang ◽  
Lin Gao ◽  
Xiaoqiang Niu ◽  
Yiping Dai
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Electrical Power ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Low Grade ◽  
Low Grade Heat

Due to environmental constraints, the Organic Rankine Cycle (ORC) is widely used to generate electricity from low grade heat sources. In ORC processes, the working fluid is an organic substance, which has a better thermodynamic performance than water for low grade heat recovery. The design of the turbine which is the key component in the ORC system strongly depends on the operating conditions and on the scale of the facility. This paper presents an experimental study on a prototype of an axial-flow turbine integrated into a regenerative ORC system with R123 as working fluid. The power output is 10kW scale, and the single-stage turbine is selected. The turbine is specially designed and manufactured, and a generator is connected to the turbine directly. In the experiment, the turbine is tested under different inlet pressure conditions (0.6–1.5MPa), different inlet temperature conditions (80–150°C) and different flow rate conditions. The experimental data such as the pressures, temperatures of the turbine inlet and outlet, flow rate, rotational speed, and electrical power generation are analyzed to find their inner relationships. During the test, the turbine rotational speed could reach more than 3010 r/min, while the design rotational speed is 3000 r/min. The isentropic efficiency of the turbine could reach 53%. The maximum electrical power generated by the turbine-generator is 6.57KW. From the test data the peak value of the temperature difference between the inlet and the outlet of the turbine is 53 °C, and the expansion ratio reaches about 11. The computational fluid dynamics (CFD) solvers is also used to analyze the performance of the turbine. The distributions of the pressure, Mach number, and static entropy in the turbine flow passage component are examined and the reasons are also obtained. This study reveals the relationships between the performance of the axial-flow turbine and its inlet and outlet vapor conditions. The experiment results and the CFD results lay a foundation for using this type turbine in the ORC systems which product electrical power from a few KW to MW.

scholarly journals The influence of selected design and operating parameters on the dynamics of the steam micro-turbine

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Grzegorz Żywica ◽  
Jan Kiciński
Keyword(s):  
Computational Analysis ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Combined Heat And Power ◽  
Operating Conditions ◽  
Design Parameters ◽  
Load Analysis ◽  
Micro Turbine

AbstractThe topic of the article is the analysis of the influence of selected design parameters and operating conditions on the radial steam micro-turbine, which was adapted to operate with low-boiling agent in the Organic Rankine Cycle (ORC). In the following parts of this article the results of the thermal load analysis, the residual unbalance and the stiffness of bearing supports are discussed. Advanced computational methods and numerical models have been used. Computational analysis showed that the steam micro-turbine is characterized by very good dynamic properties and is resistant to extreme operating conditions. The prototype of micro-turbine has passed a series of test calculations. It has been found that it can be subjected to experimental research in the micro combined heat and power system.

scholarly journals Design analysis of ORC micro-turbines making use of thermal energy of oceans

2013 ◽  
Vol 20 (2) ◽  
pp. 48-60 ◽  
Author(s):  
Marian Piwowarski
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Power Plants ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Design Parameters ◽  
Thermal Energy Conversion ◽  
Working Medium ◽  
Ocean Thermal Energy ◽  
Cycle Efficiency

Abstract The article presents the results of the analysis of energy conversion cycles making use of thermal energy of oceans. The objects of analysis were two cases of closed Organic Rankine Cycle (ORC) power plants, which were: the cycle in which the vapour of the working medium was produced by warm oceanic water in the circum-equatorial zone, and the so-called “arctic” cycle in which this vapour was produced by non-frozen water in the circumpolar zone. Between ten and twenty low-boiling media were examined for which operating parameters were optimised to obtain the highest cycle efficiency. A preliminary design of an ORC turbine which was obtained by optimising basic design parameters is included. It has been proved that realisation of the Ocean Thermal Energy Conversion (OTEC) cycle is possible both in the warm and permanently frozen regions. The results of the calculations have also revealed that the efficiency of the OTEC cycle is higher in the circumpolar zone. Selecting a low-boiling medium and designing a highly efficient turbine operating in both abovementioned regimes is technically realisable.

DESIGN AND THEORETICAL ANALYSIS OF A PROTOTYPE TILTING-PAD RADIAL BEARING WITH ADJUSTABLE CLEARANCE

Tribologia ◽  
2020 ◽  
Vol 292 (4) ◽  
pp. 7-16
Author(s):  
Artur Olszewski ◽  
Grzegorz Żywica ◽  
Tomasz Żochowski
Keyword(s):  
High Speed ◽  
Dynamic Properties ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Original Design ◽  
Generator Rotor ◽  
Low Viscosity ◽  
Turbo Generator ◽  
Tilting Pad ◽  
Rotor Assembly

The article introduces a design and analysis results of a prototype ORC (organic Rankine cycle) turbo generator rotor assembly of 300kW power, supported by tilting-pad bearings of original design. The calculations were performed for a prototype turbo generator rotor. The shaft of this machine is supported with two radial bearings, lubricated with an unusual lubricant – a low-boiling-point agent. The main objective of the presented research was to perform calculations verifying the feasibility of using hydrodynamic tilting-pad radial bearings with a low-viscosity lubricant to support a rather massive and high-speed rotor of the developed turbo generator and to determine the geometry and design of the bearings which would ensure optimal kinetostatic and dynamic properties of the rotating system, while simultaneously providing ease of assembly and smooth clearance adjustment.

Parametric Optimization of Organic Rankine Cycle by Genetic Algorithm

2014 ◽  
Vol 672-674 ◽  
pp. 741-745
Author(s):  
Shuang Bian ◽  
Teng Wu ◽  
Jin Fu Yang
Keyword(s):  
Genetic Algorithm ◽  
Parametric Optimization ◽  
Parametric Design ◽  
Waste Heat ◽  
Lower Boundary ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Pinch Point ◽  
Working Medium ◽  
Net Power Output

Organic Rankine Cycle (ORC) is widely used in the field of low temperature waste heat recovery, including solar, biomass and geothermal energy, among others. Based on the thermodynamic model of ORC system built up in Matlab, this study employ Genetic Algorithm (GA) on ORC system for parametric optimization and select a ratio of heat transfer area to total net power output as the performance evaluation criterion to predict the economy of system. R11, R113, R123 and isopentane are choosed as the working medium. The results show that the ORC system with isopentane has the minimum objective function value of 0.429m2/kw. The corresponding condensing temperature and degree of supercooling are generally located at lower boundary over their parametric design ranges, and the corresponding pinch point temperature difference are located at upper boundary. For different working fluids, there exist an optimum evaporating temperature and degree of superheat.

scholarly journals The working medium for the megawatt class utilization heat and power complex based on Organic Rankine Cycle

2018 ◽  
Vol 1105 ◽  
pp. 012094 ◽  
Author(s):  
O O Milman ◽  
B A Shifrin ◽  
V B Perov ◽  
V V Lukin ◽  
S V Chebanuk
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Medium ◽  
Power Complex

Advances in Working Medium for Organic Rankine Cycle

2013 ◽  
Vol 860-863 ◽  
pp. 1362-1365
Author(s):  
Han Lv ◽  
Wei Ting Jiang ◽  
Qun Zhi Zhu
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Research Direction ◽  
Heat Energy ◽  
Low Grade ◽  
Existing Problems ◽  
Working Medium ◽  
The Future ◽  
Working Principle ◽  
Low Grade Heat

Organic Rankine cycle is an effective way to recover low-grade heat energy, working medium is an important part of the cycle, it is one of the important factors that affects its performance. This paper introduces the working principle of organic Rankine cycle, composition, and it analyzes the excellent characteristics of medium, and the current research advances at home and abroad. Finally, aiming at existing problems, it puts forward the research direction and the key of development in the future.

scholarly journals A Quasi-dimensional Numerical Investigation of the Scroll Expander of an Organic Rankine Cycle Unit

2020 ◽  
Vol 197 ◽  
pp. 11001
Author(s):  
Antonio Cantiani ◽  
Annarita Viggiano ◽  
Emanuele Fanelli ◽  
Vinicio Magi
Keyword(s):  
Strong Dependence ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Low Noise ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Geometrical Parameters ◽  
Specific Work ◽  
Scroll Expander

Scroll compressors are often used in air conditioning and refrigeration systems thanks to their high efficiency, low noise and vibrations, light weight and high reliability. Scrolls are also widely used as positive displacement expanders in small-scale power generation systems, such as Organic Rankine Cycles (ORCs). In recent years, the research has focused on the development of mathematical models that help to predict the scroll expander performances under different operating conditions. In this work, a quasi-dimensional model of a scroll expander of an Organic Rankine Cycle unit is presented. Such an expander consists of two identical circle involute spirals, with appropriate starting segments. Specifically, the model is able to design the scroll expander geometry with either a “circular cutter” or a “perfect mesh profile” (PMP) approach, which are two of the most common scroll geometry starting segments. As regards the thermo-fluid dynamic aspects, specific sub-models have been used to account for radial and axial leakage, wall heat transfer, intake and exhaust of the working fluid. The model has been validated with available experimental data in order to assess its accuracy and, at the same time, to calibrate the implemented sub-models. The influence of some geometrical parameters on the expander performances has been assessed. In particular, a study of the influence of the wrap geometry is presented. The results show that the circular cutter approach returns better performances at the expenses of a higher mass consumption. Nevertheless, the circular cutter modification returns a higher specific work. Lastly, the influence of one of the PMP parameters on performances has been assessed. The results show a fairly strong dependence of both mechanical power and specific work, suggesting that the global optimization of all geometric parameters of the scroll expander may radically improve its performances.

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