Off-design Conditions Research Articles

Modeling and Performance Analysis of Variable Cycle Engine with Ceramic Matrix Composite Turbine Blades

To meet the requirements of future aircraft for power systems, the turbine inlet temperatures of aero engines are gradually increasing. Ceramic matrix composite (CMC), with its higher thermal limit, has become the preferred material for the turbine blades of variable cycle engines (VCEs). However, the impact of CMC turbine blades on the performance of a VCE is still unknown. In this research project, the comprehensive cooling-efficiency characteristics of CMC are determined through a fluid–solid coupling calculation; a cooling calculation model for turbine blades is established, and cooling airflow solution and control technology (CSCT) for an air system is developed. Additionally, a VCE simulation model is established to analyze the influence of CMC turbine blades on the cooling airflow of the air system and the overall performance of the engine. The results show that, for the design condition, the CMC turbine blade can reduce the cooling airflow of the air system by approximately 10%, and the net thrust is increased by 6.07–7.98%. For the off-design conditions, with the CSCT, the specific fuel consumption can be reduced by 3.06–5.73% while ensuring that the engine net thrust remains unchanged. A comprehensive analysis of the performance for both the design point and off-design points indicates that the use of CMC for high-pressure turbine (HPT) guide vanes and rotor blades yields significant performance benefits, while the performance improvement from the use of CMC for low-pressure turbine (LPT) rotor blades is minimal.

Computational Study of Pump Turbine Performance Operating at Off-Design Condition-Part I: Vortex Rope Dynamic Effects

As global power demand increases, hydropower plants often must operate beyond their optimal efficiency to meet grid requirements, leading to unstable, high-swirling flows under various load conditions that can significantly shorten the lifespan of turbine components. This paper presents an in-depth computational study on the performance and dynamics of a pump-turbine operating under 80% partial load, focusing on the formation and impact of vortex ropes. Large Eddy Simulation (LES) was utilized to model the turbulent flow, revealing complex patterns and significant pressure fluctuations. A pronounced straight vortex rope was identified in the draft tube, maintaining its trajectory and core size consistently, profoundly affecting flow characteristics. Pressure fluctuations were observed at various cross-sectional planes, with peaks and troughs primarily near the runner, indicating areas prone to instability. The standard deviation of pressure fluctuations ranged from 4.51 to 5.26 along the draft tube wall and 4.27 to 4.97 along the axial center, highlighting significant unsteady flow. Moreover, the frequency corresponding to the highest amplitude in pressure coefficient spectrographs remained consistent at approximately 9.93 to 9.95, emphasizing the persistent influence of vortex rope dynamics. These dynamics affected power generation, which was approximately 29.1 kW, with fluctuations accounting for about 3% of the total generated power, underscoring the critical impact of vortex rope formation on the performance and operational stability of pump-turbines under off-design conditions. This study provides essential insights vital for enhancing the design and operational strategies of these turbines, ensuring more efficient and reliable energy production in the face of increasing power demands.

Mixing enhancement with minimal thrust loss for the Mach 1.76 jet issuing from different beveled collar nozzles

The main objective of the present investigation is to enhance the jet mixing by introducing a nozzle collar exit inclination having bevel angles of 30°, 45°, and 60°. In addition to this, the present study also addresses the problem of investigating the jet which attains maximum mixing from beveled collar nozzle with the imposition of a minimal overall thrust loss penalty. The nozzles of the present study have been designed to deliver a uniform Mach 1.76 jet at the nozzle collar exit. The results thus obtained through numerical computations have been compared with that of the reference nozzle which has zero exit inclination. The investigations have been performed under both design and off-design conditions of the jet by varying the nozzle pressure ratio (NPR) from 4.5 to 6.5 with unit step size. It is seen that the rate of jet mixing is augmented with the increase in the bevel angle. Thus, the 60° beveled collar nozzle demonstrated the highest jet mixing in comparison to the reference nozzle, 30° and 45° beveled collar nozzle at each nozzle pressure ratio. However, 60° beveled collar nozzle has been substantially penalized with the highest thrust loss of about 6.5% at nozzle pressure ratio 4.5 and about 3.5% at nozzle pressure ratio 5.5 with respect to the reference nozzle and other nozzles of the present study. The 45° and 30° beveled collar nozzles reported the thrust penalty below 2.3% and 1%, respectively. The overall performance, which includes mixing enhancement along with the minimal thrust loss, has been found in the 45° beveled collar nozzle, which clearly justifies its preference over the other investigated nozzle configurations.

Feasibility evaluation of a wind/P2G/SOFC/GT multi-energy microgrid system with synthetic fuel based on C-H-O elemental ternary analysis

Power to gas (P2G) uses electrical energy from access renewable power and captured carbon dioxide (CO2) to generate methane (CH4). The technology provides opportunity for replacing fossil fuels with green-powered hydrocarbon, benefiting the reducing of carbon emission. However, the methanation process in P2G requires high H2/CO2 ratio with available amount of hydrogen (H2) restricted by fluctuation of renewable power, bringing limits to the reusing of captured CO2. This paper presents a feasibility analysis of a novel wind/P2G/SOFC/GT multi-energy system (MES) for microgrid. Green-powered CH4 generated from P2G is mixed with captured CO2, bringing additional flexibility to balancing the overall H2/CO2 ratio for utilization. To comprehensively analyze the feasibility of synthesis CH4/CO2 fuel, evaluation of MES is carried out from both design and off-design conditions. For the design condition, a methodology of C-H-O elemental ternary analysis is applied to reflect the process of fuel utilization and reveal its connection with the trade-off feature of multiple components. For the off-design condition, fluctuations of user's load and renewable source during winter and summer scenarios are considered in a case study. Results show that under C-H-O distribution of 5.8 %, 61.2 % and 33.0 %, the SOFC/GT could operate safety with electrical efficiency of 62 %, capable of participating as a secondary power source for MES. Meanwhile, the overall H2/CO2 utilization ratio of the system is reduced from 4:1 to 2.4:1, where extremes conditions during winter and summer scenarios are evaluated with renewable penetration level of 94 % and wind curtailment rate below 5 % reached.

Performance of Rough-Ribbed Low-Pressure Turbine Blades Under Varying Loading and Operating Conditions

Abstract In this research, we pursue the efficacy of riblets in reducing blade profile loss of Low-Pressure Turbine (LPT) blades under various design and off-design conditions. We adopt a strategy in which surface roughness is employed in the transitional regime to minimize the separation bubble-related losses and flush mounted riblets downstream to mitigate the boundary layer losses due to an increase in the turbulent wetted area. Several high-fidelity scale resolving simulations are carried out to test the efficacy of this ‘rough-ribbed’ LPT blade for loadings ranging from low-lift (LL), high-lift (HL) and ultra-high-lift (UHL) conditions. Furthermore, two exit Reynolds numbers - 83,000 and 166,000 pertaining to engine-relevant design and off-design conditions, respectively, are considered. The streamwise evolution of skin friction coefficient, boundary layer integral parameters, instantaneous flow features and second-order statistics are analyzed to determine the design and off-design performance of riblets. The results demonstrate the efficacy of scallop-shaped riblets in reducing the profile loss and the blockage due to boundary layers with loading and Reynolds number. This resulted in a net skin-friction reduction of 3.4% for LL and 8% for UHL loading at cruise and a corresponding reduction in the trailing edge momentum thickness from 10% to 15%. Furthermore, the study highlights the necessity to optimize the riblet ramp to achieve skin friction reduction under off-design conditions.

Effects of propeller cavitation on ship propulsion performance in off-design operating conditions

The propeller cavitation is closely related with its hydrodynamic performance. When the propeller works in the cavitating flow, the propeller hydrodynamic performance, in terms of thrust and torque coefficients, is reduced due to the propeller cavitation. When the high-speed and high-power ship sails in adverse sea, the varying loads on propeller will cause severer cavitation on propeller. The reduction in propulsion performance caused by cavitation will further affect the propulsion system, impacting the ship sailing performance and safety. The VP1304 propeller cavitation CFD simulation are conducted to validate the CFD method. Furthermore, the influence of propeller advance ratio and cavitation numbers on the performance of low-speed high-power series propeller in cavitating flow are studied and illustrated. This influence of cavitation has also been transferred to the propulsion system and this process are calculated by the ship propulsion system numerical model. Additionally, the sailing performance of ship propulsion system under off-design conditions, where the cavitation is more likely to occur, has been investigated in this article. Under severe heavy load conditions, it can even result in a complete loss of propulsion capability, posing significant risks. Therefore, it is necessary to further optimize control strategies for the propulsion system to mitigate the hazards caused by cavitation.

Influence of the shock wave-turbulence interaction on the swirl distortion in hypersonic inlet

This study uses the Large Eddy Simulation (LES) technique to conduct an exhaustive analysis of the flow characteristics within the Rectangular-to-Elliptical shape Transition (REST) inlet under Mach 6 conditions. It mainly focuses on investigating the influence of the shock wave-turbulence interaction on the swirl distortion at the inlet exit. At the design condition, characterized by 0° Attack and 0° Sideslip, the incident shock wave at the inlet lip undergoes multiple reflections within the boundary layer of the domain wall, culminating in the formation of turbulent structures. The first reflected shock wave has the highest energy, exerting a significant impact on the boundary layer and the exit swirl distortion. On the contrary, the energy of the incident shock wave is progressively reduced due to repeated reflections, which results in reducing the exit swirl distortion. Under off-design conditions, characterized by 6° Attack and 0° Sideslip as well as 6° Attack with 6° Sideslip, variations in the incoming flow make the incident shock wave move inward, decreasing the frequency of shock wave reflections and even significantly reducing the reflected shock waves under conditions of 6° Attack and 6° Sideslip. However, this results in significantly increasing the exit swirl angle and distortion intensity. The obtained results demonstrate that changes in the incoming flow conditions significantly affect the level of exit swirl distortion by modulating the shock wave-turbulence interaction, especially in terms of the positioning of the incident shock wave and the quantity of reflected shock waves. In addition, this paper studies the wall heat transfer coefficient of the inlet. The obtained results show that the interaction between shock waves and the boundary layer significantly affects the heat transfer coefficient. This study provides a foundation for the comprehension and prediction of the performance of hypersonic inlets across a spectrum of flight conditions, and for the guidance of the design and optimization of such inlets.

Using bionic tubercles to control swirling flow instabilities of a hydraulic turbine during the load rejection process

With the development of renewable energy sources, operations of hydroelectric units under off-designed conditions and frequently transition processes have gradually become normalized, which is accompanied by threats from swirling vortex ropes, high amplitude pressure fluctuations, and strong hydraulic vibrations. This study introduces bionic tubercles into the Francis turbine's draft tube and guide vane design to suppress pressure fluctuation and stabilize swirling vortex rope during the load rejection process. Results reveal that the bionic Francis turbine (BFT) reaches its maximum speed of 686.4 rpm at 3.804s, marking a 6.08 % reduction from the prototype Francis turbine's maximum speed during load rejection. Moreover, it significantly diminishes the principal frequency amplitude of low-frequency pressure fluctuations caused by swirling flow instability from the draft tube cone, achieving a reduction by one to two magnitude orders. It is interesting that the scale of the circumferential vortex in the vaneless region and blade vortices within the runner channels is verified to decrease. More importantly, it is attributed that the bionic tubercles effectively disrupt and disintegrate the walled circumferential vortex structures in the draft tube.

Analysis of submersible axial flow pump fitted with variable IGV at design and off-design conditions

Abstract Submersible axial flow pump is capable of generating large flow rate at high efficiency and is widely used in agriculture, irrigation, water supply and drainage in factories, urban areas, etc. Pumps are always designed to operate at the designed conditions of flowrate and head, but in certain practical applications, their off- design operation seems to be more important, like if there is waterflooding due to heavy rainfall or in case of variable flowrate, variable head operations or long-distance water supply. These situations arise for limited operation (time) and hence it is not economical to change the existing pumping system. The present work deals with the analysis of submersible axial flow pump at design as well as off-design conditions. This off-design operation was controlled by the variable inlet guide vane (VIGV) with the task of making it energy efficient for all conditions. The scope of this work was to investigate the performance of selected pump at designed rotational speed, at designed flowrate (Q/Qd =1) as well as Q/Qd =0.8 and Q/Qd =1.2, using Computational Fluid Dynamics (CFD) and at various VIGV angles in the range of ±25°. The fluid flow analysis was performed using commercial CFD tool ANSYS CFX v17.0. From the numerical study, it was concluded that the performance of the considered AFP significantly increased due to the presence of VIGV at positive rotation angles. The best performance was observed for IGV angle of +25° for all flowrates. As compared to the reference case of 0° IGV rotation, the performance of the AFP increased by 28.42% in terms of head ratio and 0.235% in terms of hydraulic efficiency, for +25° IGV angle, at the designed flowrate. Also, an increment of 69.05% in terms of head ratio and 14.49% in terms of hydraulic efficiency was observed at overload condition of Q/Qd =1.2.

Investigation into the Energy Loss Mechanism of Pump Turbine During the Runaway Process Based on Entropy Production Theory

Abstract The power-trip of the pump under certain conditions leads to the runaway of the unit, causing dangerous transitional process in pumped storage power stations. This process is characterized by transient hydraulic features like flow separation and vortex structures, which increase hydraulic losses significantly and severely impact unit efficiency and stability. This paper aims to elucidate the mechanism of energy loss due to unstable flow during pump turbine runaway. It focuses on a high-head model pump turbine, examining the transient flow process from pump conditions to runaway conditions. It conducts quantitative analysis of energy loss using entropy production theory, besides, further clarifies the location and causes of hydraulic losses by integrating with internal flow analysis. The results show that a significant high-entropy production zone is captured in the pump braking condition, indicating extremely chaotic internal flow in this area during the runaway transition process. Additionally, throughout the transition process, turbulent entropy production initially increases, then decreases. Turbulent entropy production accounts for more than 80% of total entropy production, indicating that turbulent entropy production dominates throughout the entire transition process. The energy of the water is primarily dissipated within the runner during the runaway process. The maximum proportion is 87%, which is in the pump braking condition. Correlation analysis between flow and hydraulic losses reveals that vortex structure induced by flow separation under off-design conditions is the primary contributor to increased hydraulic losses.

Numerical study on unsteady characteristics of backflow vortex cavitation in an axial flow pump

Abstract Axial pumps play a crucial role in various industries such as agriculture, construction, and chemical engineering, exhibiting optimal efficiency under design conditions. However, in practical applications, these pumps often operate under off-design conditions due to environmental constraints, which would lead to a series of problems such as increased vibration, elevated noise levels, and a shortened pump lifespan, thereby endangering its safe and stable operation. This study addresses the issue by using a modified RNG k-ε turbulence model combined with the Zwart cavitation model to simulate the cavitation characteristics of an axial-flow pump. The calculated cavitation characteristics are consistent with the experimental results, proving the exactitude of the numerical approach. A noteworthy observation is the severe cavitation occurrences at the backflow vortex, termed backflow vortex cavitation. This phenomenon undergoes inception, development, and eventual collapse constantly. According to the severity of the backflow vortex cavitation, different periods are divided into the bimodal stage and small-peak stage. Significantly, it is identified that the backflow vortex cavitation interacts with the impeller blades, as the impeller moves, thereby inducing blade vibration, and noise, and exacerbating cavitation erosion. The research results offer a theoretical foundation that is beneficial to enhancing the safe and stable operation of axial flow pumps.

A Comparative Study of Sustainable Energy Brayton Cycles in the Oil and Gas Industry. Part 1: Performance

Brayton cycles are open gas turbine cycles extensively used in civil aviation and the petrochemical industry because of their advantageous volume and weight characteristics. With the bulk of engine emissions associated, it is necessary to promote their environmentally-friendliness, including sound technical performance regularly. This research considers high bypass-low specific power plants in aviation and aero-derivative gas turbines combined-heat-and-power generation in the petrochemical industry. The investigation encompasses the comparative assessment of simple and advanced gas turbine cycle options including the component behaviour of the systems. This comprises the performance module. The research has contributed to understanding the technical performances of simple and advanced cycle helicopter engines, and aero-derivative industrial gas turbine cycles at design and off-design conditions. The simple cycles were modified for better fuel burn and thermal efficiency by using some additional components to form the advanced cycles. The helicopter engine investigated was converted to a small-scale aero-derivative industrial engine. Modeling the combined-heat-and-power performance of the small, medium, and large-scale aero-derivative industrial gas turbines was also implemented. The contribution also includes understanding the technical performances of both simple and advanced aero-derivative gas turbines combined heat-and-power at design and off-design A case study underlies the development and deployment of this model. The novelty is the conception of a tool for predicting the most preferred simple and advanced cycle aero-derivative engines combined heat-and-power generation in the petrochemical industry and the derivation of simple and advanced cycle small-scale aero-derivative industrial gas turbines from helicopter engines.

Numerical study of steam flow on the low-pressure turbine under off-design conditions: a case study of the Neka steam power plant

Numerical study of steam flow on the low-pressure turbine under off-design conditions: a case study of the Neka steam power plant

Impact of extracorporeal blood pump gap sizes on the performance and hemocompatibility under off-design operation.

Hemocompatibility remains the dominant challenge in rotary blood pumps, and more information on the relationship between individual pump design features, hemodynamics, and blood trauma in various operation conditions is necessary. The study evaluated the variation of gap sizes in extracorporeal blood pumps concerning their influence on blood compatibility, particularly during off-design conditions. We developed a parametric generic blood pump framework for in-silico and in-vitro design feature analysis. Thirty-six designs with varying axial and radial gap sizes between 0.5 mm and 3 mm were generated. CFD was applied to calculate and compare device hemodynamics and evaluate the performance and hemocompatibility during off-design and target operation conditions. The following quantities were analyzed: pressure difference, hemolysis potential, residence times, hydraulic efficiency, and recirculation ratio. The in-vitro prototype showed excellent agreement with in-silico predictions regarding hydraulic performance (R2 = 0.996 with a RMSE = 2.07). Our results show a modest impact of gap size variations ±10% on key metrics. Domain-resolved analyses revealed a significant contribution of the gap regions to the device's overall hemolytic performance, with an increasing contribution for off-design flow rates. Overall elevated hemolysis levels were identified if at least one gap size was held minimal. We introduced and showed the feasibility of a parametric rotary blood pump framework to systematically investigate design feature impact. Results suggest, larger and uniformly sized gaps being overall beneficial regarding hemocompatibility.

Operational characteristics and performance optimizations of the organic Rankine cycle under different heat source/condensing environment conditions

The fluctuating heat sources and seasonal condensing environments are critical to the operation of Organic Rankine Cycle (ORC) under off-design conditions. This paper presents a comprehensive steady-state mathematical model developed using a newly built experimental platform. Focusing on the operational characteristics, including the evaporation pressure, condensation temperature, mass flow rate, and the performance of key equipment during the regulation of the expander, working fluid pump, and cooling water pump. Results show that the net efficiency initially increases before decreases, with both evaporation pressure and mass flow rate rising alongside the working fluid pump frequency. The quasi-two-stage single screw expander achieves an isentropic efficiency above 65 %. Additionally, flexible adjustments to the cooling water pump effectively regulate the cooling system, with timely cleaning of cooling pipelines enhancing net efficiency by up to 3.27 %. Optimization using the particle swarm algorithm improves system performance, achieving net efficiency enhancements of 1.8 % and 12.3 % under specific conditions. The novelty of this study lies in directly regulation of the expander, working fluid pump, and cooling water pump, significantly enhancing the off-design performance. This research provides valuable insights for researchers and designers, enabling flexible regulation of ORC operations to ensure efficient performance under varying conditions.

Accuracy assessment of the turbomachinery performance maps correction models used in dynamic characteristics of supercritical CO2 Brayton power cycle

The supercritical CO2 Brayton cycle (SCO2BC) has emerged as a promising next-generation power generation technology due to its potential for high thermal efficiency and compact components design. Dynamic modeling of SCO2BC is crucial for understanding and analyzing its performance under design and off-design conditions. Turbomachines are critical components in SCO2BC dynamic models. While turbomachinery components are often modeled using their design-point turbomachinery performance maps (TPM), these maps become less accurate during off-design operations. Despite the existence of various TPM correction methods that ensure model validity, the implementation of the accurate ones within dynamic SCO2BC models remains scarce in the literature. This is crucial as it potentially compromises the accuracy of the obtained results. Therefore, there is a need to investigate the errors in the existing literature TPM correction models (in dynamic SCO2BC simulation) by comparing them against dynamic SCO2BC models employing a highly accurate correction method. Thus, in the current work, the common TPM correction methods from the literature are implemented in SCO2BC dynamic models and compared against a baseline mode, which uses the highly-accurate Pham method (at both the component and cycle levels). To the authors’ knowledge, this is the first work to address this research gap for the SCO2BC dynamic simulations and on both component and cycle levels. Additionally, another novelty is the usage of Simcenter Amesim software to dynamically model the SCO2BC aided with Pham model. Multible dynamic models for both the turbomachines of SCO2BC and the whole cycle are constructed and equipped with the different TPM correction methods found in literature to compare their dynamic behaviour that of Pham model. The Ideal Gas Compressibility factor (IGZ) method demonstrates a better performance than the other tested methods, as it exhibits the lowest discrepancy compared to the Pham model. Many of the other tested methods show significant errors. Furthermore, a popular hybrid correction combining IGZ and Pham (IGZ-Ph) is also investigated. Surprisingly, while seemingly beneficial, this hybrid approach negatively impacts accuracy, even resulting in predictions as if no correction was applied.

Research on Operation Characteristics of Passive Containment Heat Removal System in Typical Accident Conditions

In order to verify the feasibility of the design of the third generation of nuclear power plant independently developed in China, this study investigated the operation characteristics of the passive containment heat removal system under five working conditions using the passive containment heat removal system general performance verification facility: the design conditions, low water level conditions, low pressure conditions in the containment, extreme accidents conditions and resistance increasing conditions are analyzed, and the thermal characteristics, power requirements and thermal parameters of the containment under different operating conditions are analyzed. The results show that the heat dissipation capacity of the passive containment heat removal system exceeds the design requirements under the design conditions. Under off-design low pressure conditions, the pressure in the system is significantly affected. The decrease in the cooling water tank’s water level not only did not adversely affect the operation of the system but instead led to a significant increase in the system’s heat dissipation power. In the case of extreme accidents, the system may initially stall, but a stable natural cycle can then be established. As the system resistance coefficient increases, the heat dissipation power of the passive containment heat removal system exhibits an approximate linear decreasing trend.

CFD-based shape optimization of flashing converging-diverging nozzles in pelton turbines for domestic carbon dioxide heat pumps including off-design conditions

A path to enhance the coefficient of performance (COP) of domestic heat pumps is to replace the throttling valve with a turboexpander. Designing this component requires addressing supersonic flashing flows localized within the nozzle. In particular, two-phase flows prevent the application of the method of characteristics to design efficient converging–diverging shapes. To overcome this issue, we propose a shape optimization combined with a homogeneous equilibrium flow model as a design tool. Kriging models are used as surrogates of the objective function and constraint to reduce the overall computational burden associated with shape optimization. The infilling criterion to improve surrogate accuracy involves the maximization of the constrained expected improvement. A multi-point optimization is formulated, including design and off-design conditions in both objective and constraint, for a total of four relevant operating conditions. The off-design conditions are derived from system analysis, accounting for variations in the evaporator temperature and outlet gas-cooler temperature. The optimized nozzle results in a COP improvement of 7.6%, compared to a 6.6% increase when replacing the throttling valve with a baseline geometry designed as recommended by the literature. The adoption of a multi-point optimization strategy ensures that this enhancement in design conditions is not offset by off-design performance decay, which is 0.3 percentage points over the three off-design conditions. Overall, replacing the throttling valve with the optimized expander leads to an average COP improvement of 8.6%.

Performance prediction and design optimization of a transonic rotor based on deep transfer learning

Deep transfer learning is frequently employed to address the challenges arising from limited or hard-to-obtain training data in the target domain, but its application in axial compressors has been scarcely explored thus far. In this paper, a multi-objective optimization framework of a transonic rotor is established using deep transfer learning. This framework first pre-trains deep neural networks based on the peak efficiency condition of 100% design speed and then fine-tunes the networks to predict the performance of off-design conditions based on the small training dataset. Finally, the design optimization of the transonic rotor is carried out through non-dominated sorting genetic algorithm II. Compared to neural networks that are trained directly, transfer learning models can achieve higher prediction accuracy, particularly in scenarios with small training datasets. This is because the pre-trained weights can offer a better initial state for transfer learning models. Moreover, transfer learning models can use fewer samples to obtain an approximate Pareto front, making the optimized rotor increase the isentropic efficiency at both peak efficiency and high loading conditions. The efficiency improvement of the optimized rotor is attributed to the reduction of the loss associated with the tip leakage flow by adjusting the tip loading distribution. Overall, this study fully demonstrates the effectiveness of transfer learning in predicting compressor performance, which provides a promising approach to solving high-cost compressor design problems.

Renewable fuel-powered micro-gas turbine and hydrogen fuel cell systems: Exploring scenarios of technology, control, and operation

Two technology options, a proton exchange membrane (PEM) fuel cell and a recuperated micro-gas turbine (MGT) consisting of equipment with variable efficiencies and a controllable bypass valve, are modeled numerically. The validated simulations are studied under multiple scenarios, including technology, control, and operation. Under the technology scenario, the PEM fuel cell depicts higher net heat energy (1390.5 kW) with an overall efficiency of 93.27 %, significantly reducing thermal dissipation compared to the MGT, which has a low heat-to-power ratio (0.69) with the same hydrogen combustion rate (0.018 kg s−1). Following the fuel scenario, at 40 %-part load and 100 % bypass valve position, the highest net power (137.08 kW) and heat generation (635.07 kW) are achieved when 0.009 kg s−1 of hydrogen is combusted in MGT, exceeding other fuel utilization. In addition, the heating control strategy determines the availability status of the proposed technologies. The observed operational trends indicate effective fulfillment of urban heating needs by hydrogen combustion during Winter and Fall. However, the utilization of biogas leads to significant functional limitations. Finally, the operating function of the PEM fuel cell under off-design conditions is evaluated, resulting in notable enhancements in energy outputs and hydrogen consumption when considering the combination of control parameters compared to their individual evaluations.