Turboexpander Research Articles

Dimensioning Air Reactor and Fuel Reactor of a Pressurized Chemical Looping Combustor to Be Coupled to a Gas Turbine: Part 1, the Air Reactor

This paper provides a simple methodology for the design of the air reactor of a chemical looping combustor to optimize its characteristics when it is employed connected to a turbo expander to produce power. The design process, given a certain objective (e.g., electric power) defines the reactor specifics, namely height and diameter, taking into account the following aspects: solids inventory of the air reactor; gas velocity; air reactor transport disengaging height (TDH); solids concentration profile along the reactor height, dense bed height; freeboard height; pressure drop depending on air reactor injectors design and configuration. The total air reactor height was about 9.5 m, while the diameter was about 1.8 m. The total inventory was about 10,880 kg; while the circulation rate in the air reactor was about 110 kg/s. The operating pressure and temperature were, respectively, 12 bar and 1200 °C. The average velocity of the gases inside the reactor was about 4 m/s. The fluidization regime resulted to be comprised between turbulent and fast fluidization. Further work must be directed into the estimate of the pressure drop of the reactor, which will affect the plant efficiency in a considerable way.

Part-load performance analysis of a dual-recuperated gas turbine combined cycle system

To undertake peak shaving tasks, gas turbine combined cycle (GTCC) units often deviate from the design operating point. In order to improve the off-design performance of GTCCs, a dual-recuperated gas turbine combined cycle (DRGTCC) system based on partial recuperation and compressor inlet air heating is proposed in this paper. The operating characteristics of the novel system using the proposed operation strategy are investigated, and the effects of pressure drop in recuperators and ambient temperature on system performance are discussed. The results indicate that, compared with the GTCC system, the DRGTCC system has higher turbine inlet temperature (TIT) and turbine expansion ratio at the same power output, and the performance has been improved especially at lower power outputs. When the inlet temperature of the compressor is increased from 0 °C to 45 °C, the air mass flowrate can be regulated between 46.0% and 100% of the design value. The combined cycle efficiency of the DRGTCC system is improved by 2.55 percentage points at 45.5% design combined cycle load. Moreover, the sensitivity analysis shows that the system performance decreases with the increase of the pressure drop in recuperators, and the ambient temperature affects the load regulation range and efficiency.

Two-phase mass flow rate through restrictions in liquid-flooded twin-screw compressors or expanders

Liquid flooded twin-screw machines are commonly used as compressors for different applications and offer excellent prospects for energy conversion in lower and medium power ranges as expansion engines in Rankine cycles for example with regard to either waste heat recovery or electrical power generation from regenerative heat sources. With the aim of minimising internal leakages, lubricating moving machine parts, or reducing thermal stress and providing the benefits of wet expansion, a twin-screw machine can be operated with an auxiliary liquid or a two-phase working fluid. In this context, the present work provides a basic approach addressing the two-phase mass flow rate calculation in water-flooded twin-screw machines. Based on a generic inlet-geometry model, two-phase mass flow rates are recorded for different operating conditions and mass dryness fractions in particular. Appropriate approaches for the theoretical two-phase mass flow rate and discharge coefficient calculation considering restrictions in the flow section—such as orifices and nozzles—are applied. Finally, the two-phase discharge coefficients are compared with flow coefficients determined by means of experimental and theoretical two-phase mass flow rates revealing the limits and uncertainties of the models applied in this study.

A controllable gelatin-based microcarriers fabrication system for the whole procedures of MSCs amplification and tissue engineering.

Biopolymer microbeads present substantial benefits for cell expansion, tissue engineering, and drug release applications. However, a fabrication system capable of producing homogeneous microspheres with high precision and controllability for cell proliferation, passaging, harvesting and downstream application is limited. Therefore, we developed a co-flow microfluidics-based system for the generation of uniform and size-controllable gelatin-based microcarriers (GMs) for mesenchymal stromal cells (MSCs) expansion and tissue engineering. Our evaluation of GMs revealed superior homogeneity and efficiency of cellular attachment, expansion and harvest, and MSCs expanded on GMs exhibited high viability while retaining differentiation multipotency. Optimization of passaging and harvesting protocols was achieved through the addition of blank GMs and treatment with collagenase, respectively. Furthermore, we demonstrated that MSC-loaded GMs were printable and could serve as building blocks for tissue regeneration scaffolds. These results suggested that our platform held promise for the fabrication of uniform GMs with downstream application of MSC culture, expansion and tissue engineering.

Pressurised Chemical Looping Combustion (PCLC): Air Reactor design

Bioenergy combustion with Carbon Capture and Storage (BECCS) is a key technology to achieve carbon negative emissions power generation. This can be achieved by coupling the biofuels combustion with CO2 capture and storage (CCS). The lowest cost for CCS corresponds at the moment to the Chemical Looping Combustion (CLC) process. This can use biofuels which can be gaseous (biomethane, biogas or syngas etc.), liquid (biodiesel, bioethanol, biobutanol and pyrolysis oils etc.) or solids (wood dust, charcoal dust, wood chips, wood pellets etc.) While plant design with gaseous and liquid biofuels would be simpler, plants using solid biofuels and based on two couple fluidisd beds would need the use of a third reactor named carbon stripper. In the specific case if we plan to couple a CLC plant with a turbo expander (to achieve the high efficiencies of a combined cycle power plant) we have to work with pressurized reactors. However, there are some technical barriers to the coupling of a chemical looping combustor with a turbo expander, such as: the operation of the combustor in pressurised conditions; the inventory balance among reactors; elutriated particles reaching the turbo expander. This explaind why there is no commercial plant at the moment capable to do this. The aim of this paper is to present a model for the dimensioning of an air reactor to be coupled to a turbo expander of the power of about 12 MWe. Based on this, the air mass flow can be obtained and the geometric parameters can be calculated, to have an air velocity which is needed to achieve the fast fluidization regime and to ensure a high conversion rate as well as particles and heat exchage among air and fuel reactor.

Efficient Energy Recovery Scenarios from Pressure-Reducing Stations Intended for New Al-Alamein City in Egypt

Worldwide concerns over energy optimization and harnessing have sparked a variety of research on utilizing wasted energy. Natural gas, in particular, has been an essential energy commodity for domestic and industrial applications. This paper approaches the same principle throughout the Egyptian natural gas conventional national grid. The real case of Egypt’s Al-Alamein city gas line extension is analytically studied for energy harness. Thus, this paper aims to study the replacement of conventional energy-wasting pressure-reducing stations with power-producing expander generator systems to utilize pressure reduction in electricity generation. The mathematical equations that describe the energy recovery processes are presented. Reliable commercial software is used to verify the possible implementation of turbo expander stations in three scenarios. Each scenario is defined, and its main components and numerical parameters are introduced. Hence, the resulting energy outputs and applicability of all scenarios are compared to provide adequate energy recovery solutions.

Energy Recovery from Natural Gas Pressure Reduction Stations with the Use of Turboexpanders: Static and Dynamic Simulations

The application of expansion turbines at natural gas pressure reduction stations (PRS) is considered in order to recover energy contained in the natural gas. This energy is irretrievably lost at the reduction stations which use the traditional pressure reducer. Expanders allow for the electricity production for PRS own needs and for resale. The paper presents an analysis of the possibility of using turboexpanders at PRS in Poland. Authors performed static simulations for the assumed data sets and dynamic simulations for annual data from selected representative natural gas reduction and measurement stations. Energy balances are presented for the discussed scenarios that compare the energy requirements of natural gas pressure reduction stations which use a classic pressure reducer or turboexpander (TE). Using static simulations, authors investigated whether the use of a turboexpander is economically justified for the case if it is used only to supply the reduction station with electricity. Dynamic analyses were carried out using real data. In addition, static analyses were performed for a natural gas reduction and measurement station using a PEM fuel cell for the production of electricity in a combined gas heating system. At higher inlet temperatures and pressures, the expansion process was more economical due to the lower heat power requirement and the greater amount of produced electricity. The PRS with the turboexpander compared to the PRS with the reducer required the supply of thermal energy which did not allow the PRS to lower operating costs for the assumed prices of heat and electricity. The reduction system with the PEM fuel cell in the combined heating system positively achieved lower operating costs of the PRS (without taking into account the investment costs). Total annual costs for PRS with a reducer was PLN 1,593,167.04, and for PRS with TE + PEM PLN 1,430,595.60—the difference was PLN 108,571.44 in favor of the arrangement with TE and PEM. The payback time should be investigated, although the use of such a system gives the impression of oversizing. An increase in the electricity purchase price and a decrease in the natural gas purchase price may contribute to the investment in the future.

Energy, exergy and economic analyses of an optimal use of cryogenic liquid turbine expander in air separation units

Cryogenic liquid turbine expanders have emerged quite recently as a replacement for traditional Joule-Thomson valves in cryogenic processes for energy saving purpose. However, introducing a liquid turbine expander into the cryogenic air separation unit (ASU) can influence the operating points of ASU components, and the maximum benefits arising from the liquid turbine expander have not yet been reported. To fill such a gap, thermodynamic models are first established for ASU components, including the main air compressor, booster air compressor, cryogenic gas and liquid turbine expanders, main heat exchanger, cryogenic pump, and distillation column. To achieve the best possible use of the liquid turbine expander, an optimization method is developed by incorporating the thermodynamic models with the particle swarm optimization algorithm, in which the total minimization power consumption of ASU is the optimization goal while the flow rates and pressures of the high pressure air stream and the air stream drawn from the booster air compressor middle section together with the temperature of the medium pressure air stream exiting the main heat exchanger midway act as the optimization variables. Then, energy, exergy and economic analyses are conducted and the corresponding indexes are chosen to quantitatively evaluate the influence of the liquid turbine expander on the air separation process. For the case study, ASUs of 35000 Nm3/h oxygen production capacity with and without a cryogenic liquid turbine expander are optimized, respectively. The results show that the ASU total power saving through the use of liquid turbine expander is 4.2-fold its output shaft power; thus, the energy consumption of unit oxygen decreases by 2.12% and the overall exergy efficiency increases by 1%. In addition, the economic analysis shows that the period of return of the liquid turbine expander in the ASU is estimated to be 1.75 years.

Study on Dynamic Response Characteristics of Circular Extended Foundation of Large Wind Turbine Generator

In order to study the dynamic response characteristics of circular extended foundation of wind turbine in mountainous areas, a 1:10 scaled model test was carried out on the circular extended foundation of 2MW wind turbine, and the deformation characteristics of wind turbine foundation under random wind load were analyzed by ABAQUS numerical calculation. The results show that: (1) The wind turbine foundation has different stress types on the windward side and the leeward side. The components of the windward side foundation are subjected to tensile stress, while the components of the wind turbine leeward side foundation are subjected to compressive stress. (2) The strain of the foundation bolt, the strain of the foundation ring, and the strain of the foundation plate are within the allowable range of material deformation, but the relative deformation of the windward side and the leeward side is quite different. (3) The numerical calculation results of wind turbine foundation under strong wind load are compared with the failure results of scale model experiment, which shows that the overall overturning failure of foundation is a dynamic response mode of wind turbine foundation. In the design and construction, it is necessary to strengthen the research on the windward side and the leeward side and strengthen the anti-overturning design of the wind turbine expansion foundation.

Evaluation of the effect of pressure and heat transfer on the efficiency of a batch fuel reactor, using Iron-based Oxygen Carrier with a CFD model

Coupling a Chemical Looping Combustor fed with biofuels with a turbo expander is a promising Negative Emissions Technology (NET) to realize climate neutral targets in China and Europe. This is also an example of Bioenergy with Carbon Capture and Storage (BECCS) technology. To realize it, we need a Pressurized Chemical Looping Combustion process (PCLC). In this work, a Eulerian-Lagrangian hybrid model is developed in Barracuda-VRTM software, incorporating chemical reactions to predict the performance of a Fuel Reactor using Fe2O3 as oxygen carrier and syngas as fuel, under different pressures, ranging from 1 bar to 20 bars. The model predicted the conversion efficiency of syngas reduction using an iron-based oxygen carrier (Fe2O3/Al2O3). The results show, that the increase in pressure promotes the conversion of CO and inhibits the conversion of H2. When the two gases are considered together, the increase in pressure promotes the reaction between syngas and Fe2O3 and reduces the demand for Fe2O3 oxygen carrier per unit of syngas Lower Heating Value and so also the inventory of the reactor. Increasing temperatures promotes both the reaction of H2 and CO with Fe2O3. Dealing with CO conversion, this is more affected by pressure changes and temperature changes than H2. This represents important information for Fuel Reactor design, scale up and optimization. Further validation is neded in batch and continuous pressurised plants.

Influence of tooth geometrical shape on the leakage and rotordynamic characteristics of labyrinth seals in a cryogenic liquid turbine expander

Cryogenic liquid turbine expanders have been used in many refrigeration systems to save energy, and rotor stability is a top concern in their development. The present study focuses on the influence of tooth geometrical shape on the leakage and rotordynamic characteristics of labyrinth seals in a cryogenic liquid expander, whose rotordynamic characteristics are typically special because of the thermodynamic effect of cryogenic liquid and a large pressure drop. Computational fluid dynamics (CFD) simulations are conducted in thirteen-teeth labyrinth seals with isosceles trapezoid shaped teeth and two types of right-angle trapezoid shaped teeth for a given geometric parameter through the whirling rotor method and total energy model. The flow behavior in the three labyrinth seals with different tooth geometrical shapes is explored, and their influence on the leakage and rotordynamic characteristics of the labyrinth seal is obtained. The results show that the leakage flow rate of the labyrinth seal with front right angle trapezoid shaped teeth is 1.1% and 0.6% less than that with rear right angle trapezoid shaped teeth and isosceles trapezoid shaped teeth, respectively, because of a larger divergence angle and more leakage flow involved in dissipation, while the labyrinth seal with isosceles trapezoid shaped teeth produces a larger fluid-induced tangential force opposite to the direction of whirling velocity and is more favorable for rotor stability. In addition, a parametric study is conducted to analyze the influence of clearance, tooth height, tooth thickness and inclination angle on the leakage and rotordynamic characteristics of the three labyrinth seals.

Coal-derived graphene foam and micron-sized silicon composite anodes for lithium-ion batteries

Silicon-based materials demonstrate significant potential as lithium-ion batteries (LIBs) anode, but their expansion and degradation present engineering design challenges for commercial application. In this study, a porous three-dimensional (3D) graphene and micron-sized silicon composite anode (Si@G foam) was synthesized using humic acid (HA) derived from coal as a graphene precursor. In-situ formation of graphene structure through reducing HA was confirmed by Raman spectra. The reduced HA (rHA) shows similar electrical conductivity compared to the commercial conductive carbon. SEM images depict a 3D skeleton of coal-derived graphene, with silicon particles distributed on the 3D graphene foam's internal surface. The Si@G composite-anode displays a good reversible capacity of ∼656 mAh/g at a current density of 50 mA/g, as well as a high-rate capability of ∼433 mAh/g at a current density of 800 mA/g, and outstanding cycling stability –89.8% capacity retention after 300 cycles, which is significantly higher than that of other foam structures. During lithiation and de-lithiation, the graphene foam serves as a matrix of electrical conductors and a volume expansion support for silicon. This 3D graphene network will be beneficial for developing advanced silicon-based anodes for high-performance LIBs.

MXene interlayer space expansion: Alleviating coulomb attraction and steric resistance on multivalent charge carriers toward micro-supercapacitors with enhanced areal energy density

Sluggish bivalent Mg 2+ diffusion between MXene interlayers arising from narrow physical space and strong electrostatic attraction is significantly facilitated by interlayer expansion via the insertion of bacterial cellulose nanospacer, endowing the further fabricated symmetric Mg-ions aqueous micro-supercapacitors with enhanced areal energy density. • Mg 2+ diffusion between MXene interlayers is facilitated by interlayer expansion engineering. • An areal energy density up to 32 μWh cm -2 is realized on the fabricated symmetric Mg 2+ micro-supercapacitor. • A stretchable SMI-MSC array with stable output voltage under elongation up to 200% is fabricated. Sluggish multivalent charge carriers diffusion between MXene interlayers arising from narrow physical space and strong electrostatic attraction has long been a challenge in promoting the areal energy densities of MXene-based aqueous micro-supercapacitors (MSCs). Herein, a simple interlayer space expansion strategy of MXene-based self-assembled film electrode is proposed to alleviate coulomb attraction and steric resistance on divalent Mg 2+ transfer toward symmetric Mg-ions aqueous micro-supercapacitors (SMI-MSCs) with significantly enhanced areal energy density. The electrochemical tests prove that the enlarged interlayer space by introducing 1D bacterial cellulose (BC) nanospacer between Ti 3 C 2 T x flakes can effectively reduce the diffusion barrier of Mg 2+ within the obtained Ti 3 C 2 T x /BC composite film electrode. Benefiting from the simultaneously repressed kinetics of hydrogen/oxygen evolution on the Ti 3 C 2 T x /BC composite film electrode rooting in the employed neutral polyacrylamide/Mg(CF 3 SO 3 ) 2 hydrogel electrolyte, the as-fabricated SMI-MSCs acquire a high areal energy density of 32 μWh cm −2 and a cell voltage up to 1.2 V. Encouraged by the superior energy efficiency of single SMI-MSC unit, a stretchable SMI-MSC array has further been fabricated via integrating the SMI-MSCs on flexible circuit board with bridge-island architecture. The obtained SMI-MSC array can provide stable and adjustable output of voltage and energy under elongation up to 200%, revealing great application potential for wearable/flexible power source.

Formations and their driving forces

The purpose of this paper is to analyze and compare three systems: capitalism, socialism and digitalism through empirical and theoretical research methods. Its objectives are to describe the uniqueness of each formation, identifying their driving forces and the features used in the process of formation of one or another political-economic system. In defining capitalism, we note its reliance on capitalist capital as the main instrument and engine of expansion. As distinct from the liberals, the socialists declared as their principle the idea of universal equality, using as a catalyst the processes of unification of the working classes of the peoples and the struggle of the enslaved until the total victory of the exploited over the exploiters. Thus, to achieve the paradise of a communist political-economic formation the socialists needed a world revolution and the total suppression of the oppressed against the oppressors. Through studying these systems we can infer that they are similar in purpose and in the means of achieving their goals.

Bioenergy with Carbon Capture and Storage (BECCS) developed by coupling a Pressurised Chemical Looping combustor with a turbo expander: How to optimize plant efficiency

Bioenergy with Carbon Capture and Storage (BECCS) developed by coupling a Pressurised Chemical Looping combustor with a turbo expander: How to optimize plant efficiency

Experimental Assessment of a Reverse Brayton Cycle Based On Automotive Turbochargers and E-Chargers for Cryogenic Applications

Abstract The utilization of automotive engine components for the development of a reverse Brayton cycle is shown in this study. The well-known characteristics of turbochargers and electrical centrifugal compressors commonly used in the automotive industry is a starting point for developing an experimental cycle configuration of a reverse Brayton refrigeration cycle with the ability to achieve up to 115 K after a multi-stage compression with intermediate cooling and a single-stage expansion in a radial turbine using air (R-729) as working fluid. The use of a variable nozzle turbine allows to evaluate the optimum rack position for each operating point, while having control over refrigeration capacity. Studies over the minimum cycle pressure at the inlet of the first stage of compression have been performed to assess the possible benefit of creating vacuum or pressurize the working fluid. A 1 m^3 cooling chamber was attached to the installation to test the ability of cooling different thermal loads working under different operation ways, open or closed cycle, this is, letting the working fluid to interact with the thermal load or cooling it through a heat exchanger. The evaluation of thermodynamic parameters allows to obtain the coefficient of performance (COP) of the installation and the efficiency of each component. The analysis of turbomachinery performance will allow identifying weak points to improve cycle performance, and the coupling model between rotatory machines as well as to adapt the size of the installation to the refrigeration capacity required for different applications.

Performance improvement of ORC by breaking the barrier of ambient pressure

Decreasing the condensation pressure of organic Rankine cycle (ORC), which is usually limited by ambient pressure, can greatly increase the system efficiency. In this paper, the condensation pressure is extended from traditional ambient condensation to vacuum condensation. Liquefied natural gas (LNG) is used as the cold sink to generate vacuum condensation pressures between 0.001 MPa and 0.1 MPa. Nine substances with no or low flammability are chosen as the working fluids. The system main parameters are optimized with the objective of maximum exergy efficiency. The results show that the exergy efficiency of R227ea increases from 18.87% to 26.03% as the condensation pressure decreases from 0.1 MPa to 0.001 MPa. For some substances, however, their efficiencies turn to decrease as the condensation pressure is approaching 0.001 MPa and their optimal condensation pressures are different. The working fluids share the same optimal condensation temperature of around −90 °C under the studied conditions. R227ea is a generally good substance because of its higher critical temperature to match with heat source and lower triple point pressure (temperature) to reach lower condensation pressure (temperature). The condensation pressure always has opposite effect on exergy destructions of condenser and steam generator, as well as on direct expansion turbine and ORC turbine.

Multi‐stage flexible planning of regional electricity‐HCNG‐integrated energy system considering gas pipeline retrofit and expansion

The development of hydrogen-enriched compressed natural gas (HCNG) can make full use of the existing natural gas infrastructure, thereby alleviating the economic and technical pressure on the development of pure hydrogen. This paper proposes a multi-stage flexible planning method for the regional electricity-HCNG-integrated energy system (E-HCNG-IES), which considers the medium and long-term dynamic characteristics of the E-HCNG-IES. For each sub-regional energy station, an energy-hub type model including hydrogen/HCNG-related equipment and facilities is established. Considering the influence of hydrogen blending on the energy delivery capacity and line pack of pipelines, a hydrogen-resistant retrofit model for existing natural gas pipelines between sub-regions is proposed. Meanwhile, the model for newly constructed hydrogen pipelines is also presented. Subsequently, a series of flexibility evaluation indicators are proposed to support the performance analysis of planning schemes. The lateral comparison of sub-cases in Changzhou, China demonstrates that considering the hydrogen-resistant retrofit of natural gas pipelines can reduce the construction cost of hydrogen pipelines by about 37.12%. The peak shaving capacity of underground hydrogen storage (UHS), the energy recycling ability of turbo expander (TE), and the space-time decoupling ability of hydrogen in energy supply and demand have also been confirmed.

An Optimization Methodology for Turbines Driven by Pulsed Detonation Combustors

Abstract A step-change in efficiency of gas turbine technology and, subsequently, an emissions reduction from this technology requires conceptual changes. Substituting conventional combustion chambers with pressure gain combustion in the form of pulsed detonation combustion (PDC) is one of the promising methods that can reduce gas turbine emissions significantly. Nevertheless, the component matching for the respective systems and specifically that of turbine expanders working with the exhaust flow of PDC tubes is still not solved. The unsteady nature of PDC exhaust flow makes 3D-CFD simulations too expensive to be applied in optimization loops in early design stages. To address this question, the present paper introduces a new cost-effective but reliable methodology for turbine analysis and optimization, based on the unsteady exhaust flow of pulsed detonation combustors. The methodology unitizes a robust unsteady one-dimensional solver, a meanline performance analysis, and an adaptive surrogate optimization algorithm. A two-stage axial turbine is optimized considering all unsteady flow features of a hydrogen-air PDC configuration with five PDC tubes. A three-dimensional URANS simulation is performed for the optimized geometry and the baseline to evaluate the methodology. The results showed that the optimized turbine produces 16% lower entropy than the original one. Additionally, the turbine output power is increased by 14% by the optimized design. Based on the results, it is concluded that the approach is fast and reliable enough to be applied in optimizing any turbine working with unsteady flows, more specifically in PDC applications.

Stochastic multi-stage multi-objective expansion of renewable resources and electrical energy storage units in distribution systems considering crypto-currency miners and responsive loads

In order to mitigate the influence of global warming and greenhouse gasses emission, different proceedings are suggested such as utilizing renewable energies and demand response programs. This paper investigates the expansion of renewable resources and electrical energy storage units in distribution systems towards reducing investment costs and environmental pollution. Since the development of components is not possible in a single-stage due to the limitation of staff and funds, a multi-stage programming is applied to consider various restrictions. According to the penetration of crypto-currency miners in recent years, their impact is evaluated on the problem as the high-rate energy consumers. Moreover, the demand side management strategy and risk-averse scenario-based approach are implemented to analyze the role of responsive loads and model the renewable resources uncertainty, respectively. The results approve that simultaneous expansion of wind turbines, photovoltaics and electrical storage systems decreases the total pollution and cost by 100% and 99.98% after the third year, respectively. The simulations also validate that crypto-currency miners reduce the total revenue by 4.16%, whereas the responsive loads increase it by 9.89%. As well, the fluctuations of wind and solar power decrease the total revenue by 13.27%, in return, the robustness notably improves.