scholarly journals Mean-Line Design of a Supercritical CO2 Micro Axial Turbine

2020 ◽  
Vol 10 (15) ◽  
pp. 5069 ◽  
Author(s):  
Salma I. Salah ◽  
Mahmoud A. Khader ◽  
Martin T. White ◽  
Abdulnaser I. Sayma
Keyword(s):  
Waste Heat ◽  
Expansion Ratio ◽  
Design Tool ◽  
Single Stage ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Parameters ◽  
Axial Turbine ◽  
Inlet Conditions ◽  
Line Design

Supercritical carbon dioxide (sCO2) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800 ∘C. However, for distributed-scale systems (0.1–1.0 MW) the choice of turbomachinery type is unclear. Radial turbines are known to be an effective machine for micro-scale applications. Alternatively, feasible single-stage axial turbine designs could be achieved allowing for better heat transfer control and improved bearing life. Thus, the aim of this study is to investigate the design of a single-stage 100 kW sCO2 axial turbine through the identification of optimal turbine design parameters from both mechanical and aerodynamic performance perspectives. For this purpose, a preliminary design tool has been developed and refined by accounting for passage losses using loss models that are widely used for the design of turbomachinery operating with fluids such as air or steam. The designs were assessed for a turbine that runs at inlet conditions of 923 K, 170 bar, expansion ratio of 3 and shaft speeds of 150k, 200k and 250k RPM respectively. It was found that feasible single-stage designs could be achieved if the turbine is designed with a high loading coefficient and low flow coefficient. Moreover, a turbine with the lowest degree of reaction, over a specified range from 0 to 0.5, was found to achieve the highest efficiency and highest inlet rotor angles.

Axial Turbine Design for a Twin-Turbine Heavy-Duty Turbocharger Concept

2018 ◽  
Author(s):  
Nicholas Anton ◽  
Magnus Genrup ◽  
Carl Fredriksson ◽  
Per-Inge Larsson ◽  
Anders Christiansen-Erlandsson
Keyword(s):  
Engine Performance ◽  
Operating Conditions ◽  
Single Stage ◽  
Flow Coefficient ◽  
Speed Ratio ◽  
Heavy Duty ◽  
Turbine Stage ◽  
Axial Turbine ◽  
Radial Turbine ◽  
Turbine Design

In the process of evaluating a parallel twin-turbine pulse-turbocharged concept, the results considering the turbine operation clearly pointed towards an axial type of turbine. The radial turbine design first analyzed was seen to suffer from sub-optimum values of flow coefficient, stage loading and blade-speed-ratio. Modifying the radial turbine by both assessing the influence of “trim” and inlet tip diameter all concluded that this type of turbine is limited for the concept. Mainly, the turbine stage was experiencing high values of flow coefficient, requiring a more high flowing type of turbine. Therefore, an axial turbine stage could be feasible as this type of turbine can handle significantly higher flow rates very efficiently. Also, the design spectrum is broader as the shape of the turbine blades is not restricted by a radially fibred geometry as in the radial turbine case. In this paper, a single stage axial turbine design is presented. As most turbocharger concepts for automotive and heavy-duty applications are dominated by radial turbines, the axial turbine is an interesting option to be evaluated for pulse-charged concepts. Values of crank-angle-resolved turbine and flow parameters from engine simulations are used as input to the design and subsequent analysis. The data provides a valuable insight into the fluctuating turbine operating conditions and is a necessity for matching a pulse-turbocharged system. Starting on a 1D-basis, the design process is followed through, resulting in a fully defined 3D-geometry. The 3D-design is evaluated both with respect to FEA and CFD as to confirm high performance and durability. Turbine maps were used as input to the engine simulation in order to assess this design with respect to “on-engine” conditions and to engine performance. The axial design shows clear advantages with regards to turbine parameters, efficiency and tip speed levels compared to a reference radial design. Improvement in turbine efficiency enhanced the engine performance significantly. The study concludes that the proposed single stage axial turbine stage design is viable for a pulse-turbocharged six-cylinder heavy-duty engine. Taking into account both turbine performance and durability aspects, validation in engine simulations, a highly efficient engine with a practical and realizable turbocharger concept resulted.

Preliminary Design of Small-Scale Supercritical CO2 Radial Inflow Turbines

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Tina Unglaube ◽  
Hsiao-Wei D. Chiang
Keyword(s):  
Optimum Design ◽  
Supercritical Co2 ◽  
Velocity Ratio ◽  
Design Procedure ◽  
Expansion Ratio ◽  
Maximum Efficiency ◽  
Design Parameters ◽  
Small Scale ◽  
Preliminary Design ◽  
Line Design

Abstract In recent years, supercritical CO2 (sCO2) Brayton cycles have drawn the attention of researchers due to their high cycle efficiencies, compact turbomachinery, and environmental friendliness. For small-scale cycles, radial inflow turbines (RIT) are the prevailing choice and one of the key components. A mean line design procedure for sCO2 RIT is developed and design space exploration conducted for a 100 kW-class turbine for a low-temperature waste-heat utilization sCO2 Brayton cycle. By varying the two design parameters, specific speed and velocity ratio, different turbine configurations are setup and compared numerically by means of computational fluid dynamics (CFD) simulations. Results are analyzed to conclude on optimum design parameters with regard to turbine efficiency and expansion ratio. Specific speeds between 0.2 and 0.5 are recommended for sCO2 RIT with small though flow (3 kg/s). The higher the velocity ratio, the bigger the turbine expansion ratio. Pairs of optimum design parameters that effectuate maximum efficiency are identified, with smaller velocity ratios prevailing for smaller specific speeds. The turbine simulation results for sCO2 are compared to well-established recommendations for the design of RIT from literature, such as the Balje diagram. It is concluded that for the design of sCO2 RITs, the same principles can be used as for those for air turbines. By achieving total-to-static stage and rotor efficiencies of 84% and 86%, respectively, the developed mean line design procedure has proven to be an effective and easily applicable tool for the preliminary design of small-scale sCO2 RIT.

Design Parameters Exploration for Supercritical CO2 Centrifugal Compressors Under Multiple Constraints

2016 ◽  
Author(s):  
Wenyang Shao ◽  
Xiaofang Wang ◽  
Jinguang Yang ◽  
Huimin Liu ◽  
Zhenjun Huang
Keyword(s):  
Cfd Simulation ◽  
Velocity Ratio ◽  
Tangential Velocity ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Parameters ◽  
Working Fluid ◽  
Rotating Speed ◽  
Thermodynamic Conditions ◽  
Velocity Coefficient

The Supercritical Carbon Dioxide (SCO2) Brayton cycle has been getting more and more attentions all over the world in recent years for its high cycle efficiency and compact components. The compressor is one of the most important components in the cycle. Different from traditional working fluid, SCO2 has a risk of condensation at the impeller inlet because of the particular properties near the critical point. In order to determine the possibility of the condensation, a concept called “Condensation Margin (CM)” suited for SCO2 is introduced. It is associated with the total and saturated thermodynamic conditions. A design parameter called velocity ratio at the impeller inlet (IVR) is defined to control the state of working fluid at impeller inlet based on CM. In terms of different constraints and design requirements, such as impeller efficiency, operating range and processing technic, especially in small size cases, the design parameters at the impeller outlet are explored by establishing a function of outlet width, the number of blades, rotating speed, outlet tangential velocity coefficient and outlet meridional velocity coefficient. A preliminary design result of a low-flow-coefficient SCO2 centrifugal compressor is presented as an example of the application of the design parameters exploration results; then CFD simulation is performed, and consistent results are obtained compared with exploration results.

Numerical Investigation on the Labyrinth Seal Design for a Low Flow Coefficient Centrifugal Compressor

2010 ◽  
Author(s):  
Zhiheng Wang ◽  
Liqun Xu ◽  
Guang Xi
Keyword(s):  
Centrifugal Compressor ◽  
Labyrinth Seal ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Parameters ◽  
Centrifugal Impeller ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Isentropic Efficiency ◽  
Low Flow Coefficient

The leakage flow across the shroud of a centrifugal compressor impeller has an important effect on the compressor’s performance, in particular, in the low flow coefficient compressor. This paper presents the three-dimensional CFD simulations and the Radial Basis Function (RBF) model to investigate the aerodynamic performance of the labyrinth seal as well as the low flow coefficient centrifugal impeller. The CFD simulations are performed on the computational domain consisting of the labyrinth seal and the impeller. The relationship between the leakage loss coefficient and the isentropic efficiency is indicated. With the application of the RBF model, the global sensitivity analysis to the seal geometric design parameters is carried out, and the geometry of the labyrinth seal is optimized. The leakage of the optimized labyrinth seal is reduced remarkably and the impeller’s isentropic efficiency improved by 2% in a wide operating range.

Preliminary Design Tool for Centrifugal Compressors

2021 ◽  
Author(s):  
Lily Baye-Wallace ◽  
Grant O. Musgrove
Keyword(s):  
Pressure Ratio ◽  
Operating Parameter ◽  
Ideal Gas ◽  
Design Tool ◽  
Design Parameters ◽  
Compressor Design ◽  
Previous Design ◽  
Inlet Conditions ◽  
Total Pressure Ratio ◽  
Design Experience

Abstract Commonly, compressor designs rely on previous machines that can be slightly modified to achieve new operating requirements. In some cases, however, a completely new design is needed because no previous designs are available for the specific operating range of interest. Without a previous design, it is difficult to make initial trade studies of an appropriate impeller diameter, speed, and number of compression stages. While new compressor designs are a common occurrence in applied research applications, conceptual design typically require a point-by-point process to balance the requirements with acceptable design parameters. This can be done manually or through automation to optimize for a specific operating parameter, such as efficiency. The authors are unaware of any tool available that bounds the range of design parameters for a centrifugal compressor stage without applying a point-by-point method. In this work, two common references for conceptual compressor design were cross-checked to develop an Excel-based tool to quickly determine the design space for a given set of compressor requirements. The tool relies on design experience presented by Aungier and Baljé as well as other experience drawn from available literature [1],[2]. The sheet functions from a series of assumptions based within the design experience and requires inputs regarding the desired power, fluid flow rate, and total-to-total pressure ratio, as well as inlet conditions. While the tool currently assumes an ideal gas, future revisions can include calls to REFPROP for a real gas.

Design of Highly Loaded Turbine Stage for Small Gas Turbine Engine

2016 ◽  
Author(s):  
Prathapanayaka Rajeevalochanam ◽  
S. N. Agnimitra Sunkara ◽  
Balamurugan Mayandi ◽  
Bala Venkata Ganesh Banda ◽  
Veera Sesha Kumar Chappati ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Mechanical Design ◽  
Gas Turbine Engine ◽  
Single Stage ◽  
Flow Coefficient ◽  
Total Efficiency ◽  
Turbine Stage ◽  
Axial Turbine ◽  
Turbine Engine ◽  
Highly Loaded

Aero-thermodynamic and mechanical design of a single stage axial turbine stage has been carried out for small gas turbine engine in Propulsion Division, CSIR-NAL. From the engine design configuration extract, it is envisaged that the single stage axial gas turbine operating close to 50500 rpm and at an elevated temperature of 1095K would meet the power requirement of mixed flow compressor of 385kW. This paper presents the aero-thermodynamic, mechanical design and analysis of a single stage highly loaded axial turbine stage with a stage loading coefficient of 1.45 and a flow coefficient of 0.67. The mean-line and detailed 3D aero-thermodynamic design is carried out using commercially available dedicated turbomachinery design codes Axial® and Axcent™ of Concepts NREC. The number of blades of the rotor and stator are 50 & 19 respectively. The turbine stage has undergone a series of design improvements. The final configuration of single stage turbine is analyzed using commercially available RANS CFD software ANSYS-CFX™ and NUMECAFINE™/Turbo flow solver. The design is carried out by aiming 88% total-to-total efficiency. Detailed 3D-RANS CFD analysis of the turbine shows that, the design requirements of turbine are achieved with enhanced efficiency of 90%. Mechanical design & analysis of the turbine stage is carried out using ANSYS-Mechanical™ software. Nimonic-90 material is selected for fabrication. Detailed non-linear steady thermal-structural analysis is carried out for both stator assembly and rotor BLISK. Burst margin of rotor disk is estimated to be around 63% at design speed.

scholarly journals The Problem of Accounting for Heat Exchange between the Flow and the Flow Part Surfaces When Modeling a Viscous Flow in Low-Flow Stages of a Centrifugal Compressor

2020 ◽  
Vol 10 (24) ◽  
pp. 9138
Author(s):  
Sergey Kartashov ◽  
Yuri Kozhukhov ◽  
Vycheslav Ivanov ◽  
Aleksei Danilishin ◽  
Aleksey Yablokov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Centrifugal Compressor ◽  
Calculation Model ◽  
Flow Coefficient ◽  
Low Flow ◽  
Relative Width ◽  
Adiabatic Wall ◽  
Flow Part ◽  
Computational Fluid Dynamics Cfd

In this paper, we review the problem of accounting for heat exchange between the flow and the flow part surfaces when creating a calculation model for modeling the workflow process of low-flow stages of a centrifugal compressor using computational fluid dynamics (CFD). The objective selected for this study was a low-flow intermediate type stage with the conditional flow coefficient Փ = 0.008 and the relative width at the impeller exit b2/D2 = 0.0133. We show that, in the case of modeling with widespread adiabatic wall simplification, the calculated temperature in the gaps between the impeller and the stator elements is significantly overestimated. Modeling of the working process in the flow part was carried out with a coupled heat exchanger, as well as with simplified accounting for heat transfer by setting the temperatures of the walls. The gas-dynamic characteristics of the stage were compared with the experimental data, the heat transfer influence on the disks friction coefficient was estimated, and the temperature distributions in the gaps between disks and in the flow part of the stage were analyzed. It is shown that the main principle when modeling the flow in low-flow stage is to ensure correct temperature distribution in the gaps.

scholarly journals Structural Response of a Single-Stage Centrifugal Compressor to Fluid-Induced Excitations at Low-Flow Operating Condition: Experimental and Numerical Study

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4292
Author(s):  
Kirill Kabalyk ◽  
Andrzej Jaeschke ◽  
Grzegorz Liśkiewicz ◽  
Michał Kulak ◽  
Tomasz Szydłowski ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Structural Response ◽  
Flow Coefficient ◽  
Low Flow ◽  
Dynamic Strain ◽  
Duct Acoustics ◽  
Numerical Noise ◽  
Partial Load ◽  
Compressor Impeller

The article describes an assessment of possible changes in constant fatigue life of a medium flow-coefficient centrifugal compressor impeller subject to operation at close-to-surge point. Some aspects of duct acoustics are additionally analyzed. The experimental measurements at partial load are presented and are primarily used for validation of unidirectionally coupled fluid-structural numerical model. The model is based on unsteady finite-volume fluid-flow simulations and on finite-element transient structural analysis. The validation is followed by the model implementation to replicate the industry-scale loads with reasonably higher rotational speed and suction pressure. The approach demonstrates satisfactory accuracy in prediction of stage performance and unsteady flow field in vaneless diffuser. The latter is deduced from signal analysis relying on continuous wavelet transformations. On the other hand, it is found that the aerodynamic incidence losses at close-to-surge point are underpredicted. The structural simulation generates considerable amounts of numerical noise, which has to be separated prior to evaluation of fluid-induced dynamic strain. The main source of disturbance is defined as a stationary region of static pressure drop caused by flow contraction at volute tongue and leading to first engine-order excitation in rotating frame of reference. Eventually, it is concluded that the amplitude of excitation is too low to lead to any additional fatigue.

A Parametric Examination of the Factors Affecting the Performance of a Diffusion Absorption Refrigeration System

2021 ◽  
pp. 1-38
Author(s):  
Noman Yousuf ◽  
Timothy Anderson ◽  
Roy Nates
Keyword(s):  
Waste Heat ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Low Grade ◽  
Absorption Refrigeration ◽  
Factors Affecting ◽  
Thermally Driven ◽  
Mass Flowrate ◽  
Diffusion Absorption

Abstract Despite being identified nearly a century ago, the diffusion absorption refrigeration (DAR) cycle has received relatively little attention. One of the strongest attractions of the DAR cycle lies in the fact that it is thermally driven and does not require high value work. This makes it a prime candidate for harnessing low grade heat from solar collectors, or the waste heat from stationary generators, to produce cooling. However, to realize the benefits of the DAR cycle, there is a need to develop an improved understanding of how design parameters influence its performance. In this vein, this work developed a new parametric model that can be used to examine the performance of the DAR cycle for a range of operating conditions. The results showed that the cycle's performance was particularly sensitive to several factors: the rate of heat added and the temperature of the generator, the effectiveness of the gas and solution heat exchangers, the mass flowrate of the refrigerant and the type of the working fluid. It was shown that can deliver good performance at low generator temperatures if the refrigerant mass fraction in the strong solution is made as high as possible. Moreover, it was shown that a H2O-LiBr working pair could be useful for achieving cooling at low generator temperatures.

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