Thermohydrodynamic investigation for supercritical carbon dioxide high speed tilting pad bearings considering turbulence and real gas effect

The present study explores CFD analysis of a supercritical carbon dioxide (SCO2) radial-inflow turbine generating 100kW from a concentrated solar resource of 560oC with a pressure ratio of 2.2. Two methods of real gas property estimations including real gas equation of estate and real gas property (RGP) file - generating a required table from NIST REFPROP - were used. Comparing the numerical results and time consumption of both methods, it was shown that equation of states could insert a significant error in thermodynamic property prediction. Implementing the RGP table method indicated a very good agreement with NIST REFPROP while it had slightly more computational cost compared to the RGP table method.

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Dynamic simulation of the oscillation characteristics of supercritical carbon dioxide impacting jets

Journal of Vibration and Control ◽

10.1177/1077546318769558 ◽

2018 ◽

Vol 25 (1) ◽

pp. 61-71 ◽

Cited By ~ 1

Author(s):

Xinwei Zhang ◽

Yiyu Lu ◽

Jiren Tang ◽

Zhe Zhou ◽

Qian Li

Keyword(s):

Carbon Dioxide ◽

Numerical Model ◽

Supercritical Carbon Dioxide ◽

Oscillation Frequency ◽

High Speed ◽

Rock Breaking ◽

Target Distance ◽

Inlet Pressure ◽

Oscillation Characteristics ◽

Supercritical Carbon

A numerical model was established to investigate the dynamic oscillation characteristics of supercritical carbon dioxide (sc-CO2) impacting jets. The jet hydrodynamics, heat transfer, and physical properties of sc-CO2 fluid were incorporated into the model. The coupling of multiple fields with large velocity and pressure gradients was achieved using a modified SIMPLE segmentation algorithm. Laboratory experiments validated the reliability of the numerical model by detecting dynamic changes in the pressure on the centerline of the sc-CO2 impacting jet. Analysis of the flow field showed single or double high-speed sc-CO2 mass structures for the sc-CO2 impacting jet, revealing the generation mechanism of the impacting oscillation frequency and the mechanism of improved rock-breaking efficiency by sc-CO2 jet. The oscillation frequency equation was obtained through a quantitative treatment of the velocity and motion area of the sc-CO2 mass. Finally, the equation and simulation results were used to analyze the influences of the target distance, inlet pressure and temperature on the sc-CO2 jet oscillation characteristics. The results showed that the oscillation frequency and amplitude first increased and then decreased with increases in the target distance. The oscillation frequency and amplitude both increased with increasing inlet pressure; the oscillation frequency increased slowly with increasing temperature.

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The performance of spiral groove dry gas seal under choked flow condition considering the real gas effect

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650119891563 ◽

2019 ◽

Vol 234 (4) ◽

pp. 554-566

Author(s):

Hengjie Xu ◽

Pengyun Song ◽

Wenyuan Mao ◽

Qiangguo Deng

Keyword(s):

Carbon Dioxide ◽

Flow Condition ◽

Ideal Gas ◽

Leakage Rate ◽

Spiral Groove ◽

Real Gas ◽

Dry Gas Seal ◽

Choked Flow ◽

Real Gas Effect ◽

Gas Effect

By taking carbon dioxide and hydrogen as lubricating gas, respectively, this paper presents an analysis on the pressure characteristics and temperature distribution of spiral groove dry gas seal which influenced by real gas effect under choked flow condition. Numerical results show that the deviation between real gas and ideal gas, which expressed by the deviation degree between compressibility factor Z and 1, is the main reason for real gas effect affecting sealing performance. Compared with ideal gas model, real gas effect raises exit pressure, opening force, leakage rate, Mach number in dam region, and temperature for carbon dioxide ( Z < 1), while it decreases those characteristics for hydrogen ( Z > 1) under the same operating conditions. In addition, choked flow effect increases opening force and reduces leakage rate and temperature-drop between entrance and exit of sealing clearance. Meanwhile, it may cause an unstable behavior for the seal.

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Visualization of Supercritical Carbon Dioxide Flow Through a Converging-Diverging Nozzle

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2019-91691 ◽

2019 ◽

Author(s):

Chang Hyeon Lim ◽

Gokul Pathikonda ◽

Sandeep Pidaparti ◽

Devesh Ranjan

Keyword(s):

Carbon Dioxide ◽

Supercritical Carbon Dioxide ◽

Critical Point ◽

High Speed ◽

Operating Conditions ◽

Higher Plant ◽

Two Phase ◽

Pressure Profiles ◽

Flow Through ◽

Supercritical Carbon

Abstract Supercritical carbon dioxide (sCO2) power cycles have the potential to offer a higher plant efficiency than the traditional Rankine superheated/supercritical steam cycle or Helium Brayton cycles. The most attractive characteristic of sCO2 is that the fluid density is high near the critical point, allowing compressors to consume less power than conventional gas Brayton cycles and maintain a smaller turbomachinery size. Despite these advantages, there still exist unsolved challenges in design and operation of sCO2 compressors near the critical point. Drastic changes in fluid properties near the critical point and the high compressibility of the fluid pose several challenges. Operating a sCO2 compressor near the critical point has potential to produce two phase flow, which can be detrimental to turbomachinery performance. To mimic the expanding regions of compressor blades, flow through a converging-diverging nozzle is investigated. Pressure profiles along the nozzle are recorded and presented for operating conditions near the critical point. Using high speed shadowgraph images, onset and growth of condensation is captured along the nozzle. Pressure profiles were calculated using a one-dimensional homogeneous equilibrium model and compared with experimental data.

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Aerodynamic Optimization Design of a 150 kW High Performance Supercritical Carbon Dioxide Centrifugal Compressor without a High Speed Requirement

Applied Sciences ◽

10.3390/app10062093 ◽

2020 ◽

Vol 10 (6) ◽

pp. 2093 ◽

Cited By ~ 3

Author(s):

Dongbo Shi ◽

Yonghui Xie

Keyword(s):

Carbon Dioxide ◽

Supercritical Carbon Dioxide ◽

Flow Rate ◽

Centrifugal Compressor ◽

High Speed ◽

Design Method ◽

Pressure Ratio ◽

Aerodynamic Optimization ◽

Design Software ◽

Supercritical Carbon

Supercritical carbon dioxide (S-CO2) Brayton cycle technology has the advantages of excellent energy density and heat transfer. The compressor is the most critical and complex component of the cycle. Especially, in order to make the system more reliable and economical, the design method of a high efficiency compressor without a high speed requirement is particularly important. In this paper, thermodynamic design software of a S-CO2 centrifugal compressor is developed. It is used to design the 150 kW grade S-CO2 compressor at the speed of 40,000 rpm. The performance of the initial design is carried out by a 3-D aerodynamic analysis. The aerodynamic optimization includes three aspects: numerical calculation, design software and the flow part geometry parameters. The aerodynamic performance and the off-design performance of the optimal design are obtained. The results show that the total static efficiency of the compressor is 79.54%. The total pressure ratio is up to 1.9. The performance is excellent, and it can operate normally within the mass flow rate range of 5.97 kg/s to 11.05 kg/s. This research provides an intelligent and efficient design method for S-CO2 centrifugal compressors with a low flow rate and low speed, but high pressure ratio.

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Development of the Supercritical Carbon Dioxide Power Cycle Experimental Loop With a Turbo-Generator

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2017-64287 ◽

2017 ◽

Cited By ~ 2

Author(s):

Junhyun Cho ◽

Hyungki Shin ◽

Jongjae Cho ◽

Ho-Sang Ra ◽

Chulwoo Roh ◽

...

Keyword(s):

Carbon Dioxide ◽

Supercritical Carbon Dioxide ◽

High Speed ◽

Small Scale ◽

Brayton Cycle ◽

Power Cycle ◽

Turbo Generator ◽

Test Loop ◽

Class Test ◽

Supercritical Carbon

KIER (Korea Institute of Energy Research) has developed three supercritical carbon dioxide power cycle test loops since 2013. After developing a 10 kWe-class simple un-recuperated Brayton cycle, a second sub-kWe small-scale experimental test loop was manufactured to investigate the characteristics of the supercritical carbon dioxide power cycle, for which a high speed radial type turbo-generator was also designed and manufactured. Using only one channel of the nozzle, the partial admission method was adopted to reduce the rotational speed of the rotor so that commercial oil-lubricated bearings can be used. This was the world’s first approach to the supercritical carbon dioxide turbo-generator. After several tests, operation of the turbine for power production of up to 670 W was successful. Finally, an 80 kWe-class dual Brayton cycle test loop was designed. Before completion of the full test loop, a 60 kWe axial type turbo-generator was first manufactured and our previous 10 kWe-class test loop was upgraded to drive this turbo-generator. Due to leakage flow through the mechanical seal, a make-up loop was also developed. After assembling all test loops, a cold-run test and a preliminary operation test were conducted. In this paper, the power generating operation results of the sub-kWe-class test loop and the construction of the tens of kWe-class test loop which drives an axial type turbo-generator are described.

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