Helium Turbine Research Articles

Design and Performance Evaluation of Multi-Generation System based on Transcritical CO2 Rankine Cycle and Helium Gas Turbine with Hydrogen Production

The advancement in nuclear energy embodied by the gas-cooled modular reactor (GCMR), incorporating the transcritical CO2 Rankine cycle (tRC) and a helium turbine (He tur.) for hydrogen (H2) production, signifies a substantial leap forward in this domain. This research endeavor aimed to amalgamate various technologies to enhance energy conversion efficiency and generate clean hydrogen, a versatile energy carrier. Helium, selected as the GCMR coolant, boasts advantageous properties such as superior heat transfer capabilities, chemical inertness, and the capacity to operate at elevated temperatures. These attributes facilitate effective heat extraction from the reactor core, mitigating corrosion risks while boosting both power output and energy efficiency. A pivotal aspect of this design lies in integrating the tRC with the helium turbine, maximizing energy conversion efficiency and resource utilization by harnessing waste heat from the He turbine to generate additional power through the CO2 Rankine cycle. Furthermore, the system incorporates a hydrogen production module, enabling the clean generation of hydrogen as a byproduct of the nuclear power generation process. According to analysis results, the net power obtained from the Helium turbine was calculated as 241679 kW, and the net power produced from the tRC was calculated as 9902 kW. Additionally, with this developed system, 23.11 kg/h H2 and 183.4 kg/h O2 can be produced. The energetic and exergetic performance of the overall system is computed as 41.8% and 54.28%, while the total amount of exergy destruction is determined as 212199 kW. Moreover, analytical findings reveal that the reactor core exhibits the highest exergy destruction among system components at 91282 kW, whereas the heat exchanger (HEx) registers the lowest exergy destruction at 3.56 kW. In addition, in this study, parametric analyses are also performed to determine the effect of helium outlet temperature analysis and pressure ratio on system performance.

Thermodynamic analysis of two very-high-temperature gas-cooled reactor-driven hydrogen and electricity cogeneration systems under off-design operating conditions

This study conducts a thermodynamic analysis for two very-high-temperature gas-cooled reactor-driven hydrogen and electricity cogeneration systems integrating an iodine-sulfur cycle and a helium turbine direct cycle under off-design operating conditions. Control strategies are proposed based on inventory control. The calculation model is established for the main components of the system under off-design conditions. Two operation modes are proposed, one is to maintain the split ratio at the reactor outlet at the rated value, and the other is to maintain the hydrogen generation rate at the rated value. The off-design performance of the two systems under partial load in two modes is analyzed. For Systems 1 and 2, the suggested lower limits of reactor thermal power are 68.80 % and 69.00 % of the rated value in mode 1, and 72.04 % and 64.98 % in mode 2. As the reactor thermal power decreases from the rated value to the suggested lower limit, in modes 1 and 2, the hydrogen-electricity efficiency of System 1 decreases from 37.46 % to 36.20 % and 31.81 %, and that of System 2 decreases from 42.40 % to 41.45 % and 35.21 %. The decrease in overall efficiency is more significant in mode 2.

Study of the behavior of dust particles in helium turbines considering the effects of particle deposition and resuspension

The deposition of graphite dust poses significant challenges to the helium turbines in high-temperature gas-cooled reactors. In this study, FLUENT, a Computational Fluid Dynamics (CFD) program was used with a discrete-phase model and a random-walk model to calculate the trajectories of particles (assumed spherical). Considering the interactions between particles and the wall as well as the resuspension effect of the fluid, a particle-deposition model was established and coupled to the flow-field calculations of blades with film cooling using user-defined functions. The influence of different deposition models, particle diameters, and blowing ratios on deposition were investigated. The results show rebounding and resuspending particles significantly affect the particle-deposition rate and its distribution. With increasing particle diameter, the deposition rate initially increases and then decreases. The influence of blowing ratio on deposition is complex; as the blowing ratio is increased, the deposition rate of small particles increases, while that of large particles decreases.

The design and research of two-stage series-connected helium turbine expanders for hydrogen liquefaction system

The helium turbine expander, is a crucial part of hydrogen liquefaction systems, that determines the overall efficiency of the system. In this paper, a two-stage series-connected helium turbine expanders is designed to achieve a hydrogen liquefaction capacity of 1.7 tonnes per day (TPD). The proposed expander is based on the reverse Brayton cycle and realizes a high pressure ratio of 8.32 to meet the design objective. A dynamic design process in the expansion end is developed and numerically simulated based on the turbine expander design methodology. The off-rated condition performance of the turbine expander is predicted by adjusting the rotational speed and flow rate. The results show that the reasonable rotational speed range of the turbine expander is 46000–54000 RPM, and the reasonable flow coefficient range is 0.6–1.2, which can maintain a high level of efficiency. The internal flow characteristics of the turbine expander are analysed through numerical simulation. The results show that the outlet temperature is suitable for hydrogen liquefaction, and flow loss mainly occurs in the upper-middle part of the impeller and near the tip clearance, followed by the throat of the nozzle. In the prototype tests to verify the rationality of the design of the turbine expanders, the experimental results show that the two turbine expanders can achieve a temperature drop of 31 K, and isentropic efficiencies of 76.8 % and 80.5 %, respectively, which are higher than the design requirements of 75 %. The actual outlet temperature and isentropic efficiency are compared with the numerical simulation results. The errors are less than 4 % and 10 %, respectively, which means that the prototype manufacturing precision meets the system requirements perfectly. Thus, the design of the two-stage series-connected turbine expanders can satisfy the performance design requirements.

Dynamic simulation of CHL at SNS

A dynamic simulation model of Central Helium Liquefier (CHL) has been developed by the process simulation software; EcosimPro™. CHL consists of 4 K and 2 K cold boxes to sustain the operation of LINear ACcelerator (LINAC) which is composed of Superconducting Radio Frequency (SRF) cavities installed in the Cryomodules. 4 K cold box is a modified Claude cycle refrigerator, having LN2 precooler with two Brayton Cycle turbines, followed by the series connected Turbines (Tu3 and Tu4), and a Supercritical Helium (SHe) turbine (Tu5) for high thermodynamic efficiency. The product of 125 g/s of SHe is subcooled at the LHe immersed Heat eXchanger (HX) before supplying to Cryomodules, which has its own precooled HX for He II vapor vs. SHe, to have high liquid yield for He II at 2.1 K. Four series connected Cold Compressors (CCs) keep the LINAC pressure at 0.04 bar for the proton beam acceleration. The paper discusses the modeling of CHL, including four CCs. The benchmark of the model against a design specification of CHL and the validation of CC model is also described in detail.

Development of helium turbine loss model based on knowledge transfer with neural network and its application on aerodynamic design

Helium turbines are widely used in the Closed Brayton Cycle for power generation and aerospace applications. The primary concerns of designing highly loaded helium turbines include choosing between conventional and contra-rotating designs and the guidelines for selecting design parameters. A loss model serving as an evaluation means is the key to addressing this issue. Because of the property disparities between helium and air, turbines utilizing as working fluid experience distinct loss mechanisms. Consequently, directly applying gas turbine experience to the design of helium turbines leads to inherent inaccuracies. A helium turbine loss model is developed by combining knowledge transfer and the Neural Network method to accurately predict performance at design and off-design points. By utilizing the loss model, design parameter selection guidelines for helium turbines are obtained. A comparative analysis is conducted of conventional and contra-rotating helium turbine designs. Results show that the prediction errors of the loss model are below 0.5 % at over 90 % of test samples, surpassing the accuracy achieved by the gas turbine loss model. Design parameter selection guidelines for helium turbines differ significantly from those based on gas turbine experience. The contra-rotating helium turbine design exhibits advantages in size, weight, and aerodynamic performance.

Comprehensive analysis of a high temperature solar powered trigeneration system: An energy, exergy, and exergo-environmental (3E) assessment

In the present work, helium serves as the primary working fluid within the supercritical Brayton cycle, employed to generate power through a solar power tower system. The conventional Brayton cycle for recovering the wasted heat is combined with a cascaded vapor absorption-compression refrigeration system to increase the overall system’s performance. Additional benefits of this integrated system include the ability to supply enhanced heating and cooling for food storage applications at lower temperatures. A comprehensive analysis of the combined system was conducted based on exergy, energy, and exergo-environmental (3E) factors a using computational technique engineering equation solver. The combined system’s energy, exergy efficiency, and power output were determined to be 28.82%, 39.53%, and 14.865 kW, respectively. The coefficient of performances for cooling and heating were observed as 0.5391 and 1.539 respectively. Approximately 78.18% of the total exergy destruction within the entire plant can be attributed to the solar subsystem, which amounts to 22.763 kW. As direct normal irradiance rises, the environmental impact index decreases from 1.6504 to 0.6801, while the system’s environmental stability factor improves, increasing from 0.3773 to 0.5952. Moreover, the parametric assessment highlights the substantial influence of heliostat and receiver efficiencies, as well as the helium turbine’s inlet temperature, on the trigeneration system’s performance. In addition, compared to previously published research, the current proposed system outperforms supercritical CO2 cycle systems and the conventional steam Rankine cycle systems.

Performance evaluation of a solar based Brayton cycle integrated vapor compression-absorption trigeneration system for power, heating and low temperature cooling

Among the various solar technologies, solar power tower (SPT) technology is being widely used for large-scale energy generation. Therefore, this work developed a trigeneration system for SPT plant that produces power, heating and cooling at low temperature efficiently from a high temperature SPT heat source. In order to create heating and low temperature (at −20°C) cooling benefits for food preservation, this trigeneration unit integrates a cascaded vapor compression-absorption refrigeration system combined with a helium Brayton cycle for power generation. The exergy-energy analysis was performed by the numerical technique using engineering equation solver software to evaluate the performance of the proposed SPT plant. The power output, exergy and energy efficiency of the SPT plant were found as 14,865 kW, 39.53% and 28.82%, respectively. The coefficient of performances values for cooling and heating were observed as 0.5391 and 1.539, respectively. Exergy evaluation revealed that approximately 78.18% of the total energy destruction of the entire plant is attributed to the solar subsystem only. Furthermore, a parametric investigation shows that the temperature of the evaporator, generator and helium turbine inlet, and the efficiency of the heliostat and receiver all have a significant impact on the plant performance. Furthermore, a comparative analysis with relevant previous studies has shown that the proposed system outperforms systems based on supercritical CO2 cycles and the Rankine cycles.

Thermal effect on the modal characteristics of the rotor of a typical cryogenic turbine for helium refrigerator

The helium turbine is a critical component of the cryogenic system for nuclear fusion devices. To ensure the turbine's steady functioning and avoid resonance, it is essential to understand and clarify the influence of key factors on its modal characteristics. This paper investigates the influence of thermal effect, fluid-structure interaction and rotational effects on the intrinsic frequency of a helium turbine used in the Comprehensive Research Facility for Fusion Technology (CRAFT) cryogenic system. The effects of coefficient of thermal expansion, thermal conductivity and Young's modulus on the intrinsic frequency of the rotor are explored, considering these thermal factors that vary with temperature. The results indicate that thermal effect has the greatest influence on the intrinsic frequency of the rotor over rotational effectand fluid-structure interaction. Lower-order modes are more sensitive to changes in thermal conductivity, while higher-order modes are more sensitive to changes in Young's modulus at low temperatures. The intrinsic frequency of the rotor is more sensitive to changes in the thermal factors of the shaft rather than the thermal factors of the impellers.

Performance analysis of a solar based novel trigeneration system using cascaded vapor absorption-compression refrigeration system

Solar power tower technique has a strong potential among several solar systems for large-scale power generation. It is crucial to make new, efficient trigeneration unit for solar power tower plant. This work makes a novel supercritical Brayton cycle based combined cycle in which helium is considered as the working fluid for power generation. The cascaded vapor absorption-compression refrigeration system is integrated with traditional Brayton cycle for recovering waste heat to produce additional heating and low temperature cooling effects for food storage. The energy, exergy efficiency and power output of the proposed plant were found as 28.82%, 39.53% and 14,865 kW respectively. The COPcooling and COPheating values were observed as 0.5391 and 1.539 respectively at 850 W/m2 of direct normal irradiation, 80 °C of generator temperature (Tc) and -20°C of evaporator temperature (Te). Solar sub system is responsible for high exergy destruction around 78.18% (22,763 kW) of total destruction of the overall plant. Moreover, parametric study reveals that performance of trigeneration system is highly affected by the heliostat and receiver efficiency, Tc, Te and inlet temperature of helium turbine. Also, a comparison with related earlier research has demonstrated that the performance of the current system is superior to that of systems based on the Rankine cycle and supercritical CO2 cycles.

Design and analysis of 5 kW helium turbine for EAST cryoplant

The helium turbine is an important core component in the refrigerator, which provides support and guarantee for the stable operation of the cryogenic system. This paper refers to the parameters of one of the four helium turbines in EAST, designs a 5 kW helium turbine. The overall structure of the turbine has been described, and the design and analysis of the impeller and bearing have been carried out. Through CFD analysis, the internal pressure and temperature change law of the flow is analyzed. The variable-condition operating characteristics of the turbine are predicted, and it is found that the turbine can maintain efficient operation within a wide range of mass flow changes. The bearing performance is calculated by solving the Reynolds equation. After determining the optimal bearing clearance 28 μm based on the principle of maximum stiffness, bearing performance parameters of load capacity and stiffness can be further calculated.

Design and performance analysis of the thrust gas bearing with single orifice for helium turbine

Thrust bearing is an important component for the stability of helium turbo-expander, and is a critical part to ensure the stable operation of helium refrigerator. A thrust bearing with single orifice is designed at the end of the fan brake for a home-made 500W@4.5K helium turbine. This design optimizes the mechanical structure of the rotor and improves the overall stability of the helium turbine. To increase the axial capacity, the static and dynamic calculation model of this thrust bearing is established to analyse the performance. This paper describes the variation curve of parameters and studies the influence of temperature on bearing performance by numerical simulation method. The analysis as more simple and efficient method is used to obtain the important parameters of this thrust gas bearing with single orifice, which meets the demand of the whole engineering design for helium turbine expander.

Design and analysis of an eddy current brake helium turbine for CFETR refrigerator

Due to the large-scale cryogenic system of the fusion device and the existence of pulse heat load, higher requirements are put forward for the adaptability and adjustability of the cryogenic system. This paper proposes an eddy current brake helium turbine structure, which can realize the rapid adjustment of the turbine through the electric current. The design and analysis of the turbine are carried out from the three core components of the flow part, the brake device and the bearing. The results show that the rated speed of impeller is 121,000 rpm and the impeller power calculated by computational fluid dynamics simulation is 5.88 kW. The performance of the eddy current brake is shown by electromagnetic simulation, and the rated braking current of 1.1 A is determined. Through the compiled bearing finite element calculation program, the bearing clearance is optimized to 30 μm, and the bearing performance is further predicted.

Student Research Projects With Industrial Impact

Abstract This paper describes six final year undergraduate research projects supported by a collaboration between the Whittle Laboratory at the University of Cambridge and Reaction Engines (RE), a UK aerospace company. The collaboration is now in its fourth year of projects relating to RE's synergetic air breathing rocket engine (SABRE). The approach taken in these projects combines modern teaching pedagogy with a best practice methodology for industrial-academic collaboration and a well established framework for structuring research problems. This paper explains how the three methodologies are tailored and adapted for use with final year undergraduate research projects. The approach is mapped on to an annual project cycle which begins with the industry and academic partners deciding which topics to investigate and proceeds through student selection, the project work itself and concludes with student assessment and end-of-year reporting. The projects combine analytical, computational and experimental work and have covered counter-rotating turbomachinery, S-ducts in compressors and Helium Turbine design, all of which are topics of primary importance to the design of SABRE. Following descriptions of each of the six completed projects, the impact of the work and lessons learned are considered from the point of view of the students, the industrial partner and the academic supervisors. Overall, the students found the work extremely engaging and have all been encouraged to pursue careers in engineering, either in industry or through postgraduate study. For the industry partner the collaboration provides expertise and an approach which is not available in-house as well providing a “second look” at key technical questions. For the academics involved, the opportunity to lead research on a “real” problem with an industrial partner has proved highly motivating as well as providing opportunities for personal and career development.

Design and 3E analysis of a hybrid power plant integrated with a single-effect absorption chiller driven by a heliostat field: A case study for Doha, Qatar

This study suggests a novel zero-emission combined cooling and power (CCP) system using a high-temperature solar field, i.e., heliostat reflectors and a central receiver as the heat supplier of the whole system. In addition to the solar field, the proposed system consists of a hybrid power plant comprising a closed Brayton cycle using helium gas and a Kalina cycle, and a cooling production unit through a single-effect absorption chiller. To ameliorate the technical contribution of the current research work, the system suggested here was considered for a case study in Doha, Qatar. Hence, a comprehensive parametric analysis taking into account the energy, exergy, and exergoeconomic (3E analysis) performance criteria based on crucial design parameters is conducted. Furthermore, the economic feasibility analysis of the system is carried out through appraising the net present value. Regarding the parametric analysis, the 3E criteria evaluated here exhibited more sensitivity to variation in heliostat field efficiency and helium turbine inlet temperature, respectively. Moreover, the baseline design mode demonstrated that the electricity was produced by 15.29 MW, the coefficient of performance (COP) of the cooling production unit was 0.812, and also the overall exergy efficiency and sum unit cost of products were obtained as 29.87% and 4.34 $/GJ, respectively. Likewise, for the electrical unit exergy cost of 0.05 $/kWh and cooling unit exergy cost of 0.08 $/kWh, the calculated net present value and payback period of the suggested system were correspondingly equal to 1.605×107 and 3.1 years.

Research on structure characteristics of the helium-lubricated spiral grooved thrust bearing for helium turbine expander

The helium-lubricated spiral grooved thrust bearing of helium turbo expander was studied by numerically simulating the steady-state non-linear Reynolds equation, the Reynolds equation of the pressure was solved by finite difference method (FDM), the film pressure distribution is calculated iteratively by MATLAB program, the structural parameters including the spiral angle, the groove length ratio, the groove width ratio influenced on the static characteristics were analyzed. The results show that: The bearing loading capacity of helium lubricated spiral grooved thrust gas bearing is lower than that of air lubricated bearing under the same conditions; The viscosity of the lubricant only affects the gas carrying capacity of the thrust disc when the spiral groove is on the bearing, while the density of the lubricant has a greater influence on the bearing loading capacity; When the spiral groove is designed on the rotor thrust disc, the bearing loading capacity of the spiral grooved thrust bearing increases by 6% on average compared with that of the spiral groove on the bearing.

Rotational Effect on Flow Field and Thermal Characteristics of a Turboexpander for Helium Liquefaction System: A Numerical Perspective

Abstract Cryogenic turboexpander is an essential component to produce the refrigeration effect in various helium liquefaction systems. The convergent nozzle and small-scale radial inflow turbine (turboexpander) are the important components that are responsible for increasing the performance of the cycle. In this paper, an optimum preliminary design approach of the turbine and nozzle is explained using real gas properties. Initially, the Sobol method is used to determine the sensitivity indices and optimized range of ten important nondimensional and geometrical variables for better performance of the radial turbine. Three turboexpanders of a modified Collins cycle-based helium liquefaction system have been designed considering the optimized ranges. The proposed method improves the isentropic efficiency and power output of the turbine up to 3.86% and 5.14%, respectively, as compared to the initial design. Hereafter, a comparative three-dimensional numerical analysis is conducted to characterize the flow physics and thermal properties of three turboexpander systems (16 bar and 40 K, 6 bar and 20 K, and 16 bar and 10 K). The thermal and fluid flow properties such as temperature, Prandtl number, static enthalpy, entropy, velocity vectors, Reynolds number, and turbulence kinetic energy are determined at different spans and streamwise locations. Moreover, the present numerical results are also verified with the experimental and numerical results obtained from the existing literature. The study highlights the optimal range of design variables for helium turbine, the methodology for helium liquefaction system, and the numerical analysis to understand the flow physics and thermal properties of helium near its boiling point.

Dynamic simulations of medium-sized hydrogen liquefiers based on EcosimPro simulation software

Dynamic simulations of medium-sized hydrogen liquefiers have been performed using process simulation software EcosimPro. Two hydrogen liquefier process flows have been simulated. One process flow is a helium refrigerator with one helium turbine providing cooling power for hydrogen liquefier, the other one is a helium refrigerator with two helium turbines providing cooling power for hydrogen liquefier. Control logics and control strategies for these two hydrogen liquefiers have been proposed. The cooling down simulations have been performed separately. One turbine hydrogen liquefier, pressure ratio is 2/16 bara, helium mass flow rate is 111 g/s, hydrogen mass flow rate is 4.3 g/s, the liquefaction rate of hydrogen is about 191 L/h. Two turbines hydrogen liquefier, pressure ratio is 1/14 bara, helium mass flow rate is 110 g/s, hydrogen mass flow rate is 5.2 g/s, the liquefaction rate of hydrogen is about 184 L/h. Comparison and discussion have been proposed.

Trailing edge loss analysis of high-speed cryogenic microturbines used in helium applications

The trailing edge flow characteristics have significant impact on the turbine performance. To improve the performance of the turbine, a detailed analysis of the turbine flow field and the loss generation mechanisms associated with trailing edge is called for. This is of much importance in cryogenic helium turbines as the flow characteristics would be different from other turbines due to its characteristics like higher speed and smaller dimensions. In this paper, the trailing edge loss mechanism and the effect of trailing edge profile on the performance of a cryogenic helium turbine was analysed using CFD. The effect of flow separation, base pressure and trailing edge blockage were analysed. The study observed that the trailing edge loss became significant only when its thickness was increased beyond 3% of the blade pitch. This will provide some leeway for the manufactures to have thicker trailing edges without compromising on the turbine performance.

A methodology for the performance prediction: flow field and thermal analysis of a helium turboexpander

Helium liquefaction systems are widely used in nuclear fission, superconductivity, space industries, and other scientific instruments. However, the efficiency of these systems is quite low due to the cryogenic operating temperature. In this regard, the one-dimensional design methodology of the helium turbine and nozzle (hereafter, renowned as turboexpander) is important to increase the efficiency of the system. This paper demonstrates the sensitivity analysis and optimal range of non-dimensional design variables on which the radial inflow turbine has maximum efficiency, minimum losses, and maximum power output using artificial intelligence techniques. On this basis, three turboexpander models are developed within the optimal range of predicted non-dimensional variables. After that, a comparative numerical study is carried out to highlight the flow field and thermal characteristics of helium fluid. The standard two equations \(k{-}\omega \) SST model is used to solve the three-dimensional incompressible flow inside the computational domain. The numerical results are validated with the available experimental data from the existing literature. The variation of Mach number, Reynolds number, Prandtl number, static entropy, static enthalpy, temperature, and pressure inside the turboexpander is significantly affected by blade profile which is enormously affected by the design methodology. The study also demonstrates the flow separation region, vortex formation, tip leakage flow, secondary losses, and its reasons along with the spanwise location. The results highlight the importance of the design methodology, sensitivity analysis, the prediction capability of the artificial intelligence network, numerical methodology, and development of the helium turboexpander prototype models.