A study of partial admission characteristics on a small-scale radial-inflow turbine

Radial inflow turbines, characterized by a low specific speed, are a candidate architecture for the supercritical CO2 Brayton cycle at small scale, i.e., less than 5 MW. Prior cycle studies have identified the importance of turbine efficiency to cycle performance; hence, well-designed turbines are key in realizing this new cycle. With operation at high Reynolds numbers, and small scales, the relative importance of loss mechanisms in supercritical CO2 turbines is not known. This paper presents a numerical loss investigation of a 300 kW low specific speed radial inflow turbine operating on supercritical CO2. A combination of steady-state and transient calculations is used to determine the source of loss within the turbine stage. Losses are compared with preliminary design approaches, and geometric variations to address high loss regions of stator and rotor are trialed. Analysis shows stage losses to be dominated by endwall viscous losses in the stator. These losses are more significant than predicted using gas turbine derived preliminary design methods. A reduction in stator–rotor interspace and modification of the blade profile showed a significant improvement in stage efficiency. An investigation into rotor blading shows favorable performance gains through the inclusion of splitter blades. Through these, and other modifications, a stage efficiency of 81% is possible, with an improvement of 7.5 points over the baseline design.

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Meanline Modeling of Radial Inflow Turbine With Twin-Entry Scroll

Volume 5: Manufacturing Materials and Metallurgy; Marine; Microturbines and Small Turbomachinery; Supercritical CO2 Power Cycles ◽

10.1115/gt2012-69018 ◽

2012 ◽

Cited By ~ 7

Author(s):

Carl F. Fredriksson ◽

Xuwen Qiu ◽

Nick C. Baines ◽

Markus Müller ◽

Nils Brinkert ◽

...

Keyword(s):

Model Prediction ◽

Good Accuracy ◽

Cfd Analysis ◽

Test Results ◽

Analysis And Design ◽

Radial Turbine ◽

Partial Admission ◽

Radial Inflow Turbine ◽

Inlet Conditions ◽

Accuracy Of Prediction

Twin entry turbines are widely used in turbocharging as a means of using the exhaust pulse energy of multi-cylinder engines. For modern engines where high levels of EGR are required, an asymmetric twin-entry turbine has been shown to have considerable advantages. Such turbines require a more developed approach to analysis and design than usual. A meanline model for a radial inflow turbine with twin-entry scroll has been developed. Different total pressures and total temperatures may be specified at each entry. Each volute passage is solved separately from the inlet to the splitter location, where the static pressures of both passages are assumed to be the same. From the volute splitter to the rotor inlet, the two streams mix into one uniform flow following conservation laws of continuity, momentum and energy. Experiments have been conducted on a test stand with a radial turbine with an asymmetric twin-entry scroll, where the inlet conditions can be varied independently for each entry. The test results are compared with the model prediction. A good accuracy of prediction is achieved with a realistic set of modeling coefficients. In the future, insights gained from test data and CFD analysis will be used to develop further the volute mixing model and include explicit partial admission losses in the rotor.

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Performance Characteristics of a Small-Scale Axial-Type Turbine Operated in a Low Partial Admission Rate

International Journal of Turbo and Jet Engines ◽

10.1515/tjj.2006.23.4.211 ◽

2006 ◽

Vol 23 (4) ◽

Cited By ~ 1

Author(s):

Chong-Hyun Cho ◽

Tae-Hwan Cho ◽

Soo-Yong Cho

Keyword(s):

Admission Rate ◽

Performance Characteristics ◽

Small Scale ◽

Partial Admission

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Radial Inflow Turbine Assessment for Small-Scale Concentrated Solar Rankine Combined Heat and Power Technology

ASME 2010 4th International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2010-90250 ◽

2010 ◽

Author(s):

Deborah A. Sunter ◽

Van P. Carey ◽

Zack Norwood

Keyword(s):

Rural Communities ◽

Power Systems ◽

Residential Buildings ◽

Combined Heat And Power ◽

Operating Conditions ◽

Geometric Parameters ◽

Small Scale ◽

Brayton Cycle ◽

Analysis Tools ◽

Radial Inflow Turbine

Recent studies suggest that small scale (5–10kW) distributed solar Rankine combined heat and power could be a viable renewable energy strategy for displacing fossil fuel use in residential buildings, small commercial buildings, or developing rural communities. One of the primary obstacles of scaling down solar Rankine technology to this level is finding an appropriate expander design. This paper considers the radial-inflow turbine for such an application. Although well-tested methodologies exist for design analysis of radial inflow turbines, existing analysis tools are generally focused on machines using a combustion gases in a Brayton cycle. Use of Rankine cycle working fluids under conditions optimal for small scale Rankine solar systems result in turbine operating conditions that can be dramatically different from those in combustion-based Brayton cycle power systems. This investigation explored how analysis tools developed by NASA and others for conventional Brayton cycle power systems can be adapted to analyze and design radial inflow expanders for small scale Rankine solar combined heat and power systems. Using a 1D model derived from analysis methodologies used by NASA for conventional aerospace gas turbine power applications, the effect of reduced power output on performance is explored. Since the model contains several non-dimensional variables, a variety of geometries are surveyed, and performance sensitivity to various geometric parameters is observed. The interplay between radial inflow turbine performance and cycle efficiency for the system is examined in detail. Several fluids are compared to access how critical temperature and the shape of the saturation dome affect thermodynamic performance of the cycle and efficiency of the turbine. Conclusions regarding optimal fluids and geometric parameters for the radial-inflow turbine are discussed.

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Design and Optimization of a Radial Inflow Turbine for Use with a Low Temperature ORC

Energies ◽

10.3390/en14248526 ◽

2021 ◽

Vol 14 (24) ◽

pp. 8526

Author(s):

Richard Symes ◽

Tchable-Nan Djaname ◽

Michael Deligant ◽

Emilie Sauret

Keyword(s):

Fuel Cell ◽

Low Temperature ◽

High Efficiency ◽

Waste Heat ◽

Fluid Dynamic ◽

Organic Rankine Cycle ◽

Pem Fuel Cells ◽

Small Scale ◽

Heat Sources ◽

Radial Inflow Turbine

This study aims to design and optimize an organic Rankine cycle (ORC) and radial inflow turbine to recover waste heat from a polymer exchange membrane (PEM) fuel cell. ORCs can take advantage of low-quality waste heat sources. Developments in this area have seen previously unusable, small waste heat sources become available for exploitation. Hydrogen PEM fuel cells operate at low temperatures (70 °C) and are in used in a range of applications, for example, as a balancing or backup power source in renewable hydrogen plants. The efficiency of an ORC is significantly affected by the source temperature and the efficiency of the expander. In this case, a radial inflow turbine was selected due to the high efficiency in ORCs with high density fluids. Small scale radial inflow turbines are of particular interest for improving the efficiency of small-scale low temperature cycles. Turbines generally have higher efficiency than positive displacement expanders, which are typically used. In this study, the turbine design from the mean-line analysis is also validated against the computational fluid dynamic (CFD) simulations conducted on the optimized machine. For the fuel cell investigated in this study, with a 5 kW electrical output, a potential additional 0.7 kW could be generated through the use of the ORC. The ORC’s output represents a possible 14% increase in performance over the fuel cell without waste heat recovery (WHR).

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Study on the Steady and Unsteady Aerodynamic Performance of a Radial Inflow Turbine With Small Partial Admission in a Miniature ORC System

ASME 2011 Power Conference, Volume 1 ◽

10.1115/power2011-55268 ◽

2011 ◽

Author(s):

Ping Li ◽

Jianhui Chen ◽

Di Zhang ◽

Yonghui Xie

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Rotational Speed ◽

Rankine Cycle ◽

Maximum Efficiency ◽

Unsteady Aerodynamic ◽

Radial Turbine ◽

Partial Admission ◽

Excitation Force ◽

Radial Inflow Turbine

There is a great deal of residual heat under 350 °C being released into environment, without being used efficiently. Compared to the Rankine cycle with water as its working substance, it is effective to utilize Organic Rankine Cycle (ORC) to recover these waste heats. In the threshold of this paper, a miniature ORC system is proposed, and maximum efficiency of the system is achieved by means of optimal working substance. Moreover, numerical simulation of the partial admission (ε = 0.267) high rotational speed radial inflow turbine, which is the key unit in the system, is fulfilled. At the operating rotational speed of 60000 rpm and the proposed thermodynamic parameters, steady and unsteady flow field in the turbine are investigated with R11 as working fluid. The detailed parameters, such as axial force of rotor, power generated and thermal efficiency of the radial turbine, are analyzed. In addition, the unsteady flow pressure is integrated around the rotor blade profile to provide the unsteady aerodynamic blade force. And subsequently frequencies of unsteady disturbances and excitation force factors are obtained by spectrum analysis, which are of key importance for blade response analysis. The generation, development and dissipation process of the secondary flows, passage vortex and leakage vortex are observed in the flow channel. The results reveal that the partial admission greatly influences the parameters distributions in the flow field and the losses of radial turbine mainly occur at the frontier of the passage in the vicinity of blade root. As is discussed in the analysis of excitation force factor, the radial turbine is safe in the operation. The results discussed in this paper are beneficial for the sequent optimization and manufacture of the miniature turbine.

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