Combined Cycle Research Articles

Thermodynamic modeling and optimal short-term scheduling of a green H2-fueled combined heat and power generation system for industrial zones

This paper presents a novel green combined heat and power generation system for industrial applications. It composes of a hydrogen-fueled combined cycle power plant and a battery energy storage. Firstly, the hydrogen-air rich mixture enters the combustion chamber of the gas turbine cycle for generating electricity, while recovering the heating energy from the exhausted flue gases for driving a steam turbine cycle. The heating energy extracted from the condenser heat exchanger is also used to supply the heating demand of the end-user. Moreover, a comprehensive thermodynamic model and analysis of H2 combustion process is provided to estimate the adiabatic flame temperature based on enthalpies of reactants and products. The optimum operating point of the cogeneration system is found by solving a mixed-integer nonlinear problem using MATLAB and GAMS over a 24-h study horizon aiming to minimize its daily operation cost considering all technical constraints of system components and load-generation balance criterion. It is found that the energy efficiency of the hydrogen-fueled combined cycle changes from 46 to 58 % while generating 11.331–12.982 MW electricity and 4.436–4.984 MW heat. Two cases are studied without and with participation of battery in energy procurement strategy. It is demonstrated that the objective function of the optimization problem improves from 18 $ cost in case 1 to 29 $ revenue in case 2.

Experimental Study of Natural Gas and Hydrogen Co-Firing Characteristics Using Different Types of Single Nozzles of F-Class Practical Gas Turbine Combustors

Abstract Recent research on co-firing natural gas and hydrogen, a carbon-free clean fuel, aims to reduce greenhouse gas emissions from aging gas turbine power generation, a key energy issue. This approach can enhance old gas turbines and increase the proportion of combined cycle power plant utilization as coal-fired power plants in Korea gradually shut down. This study seeks optimal operating conditions for mixed fuels without modifying the F-class gas turbine combustor. Experiments were conducted using four different types of fuel nozzles (F-Class DLN combustors) under varying loads and co-firing rates. The test used actual machine operating conditions from 30% to 100% thermal load, with hydrogen co-fired with natural gas up to 70% at each load. OH high-speed imaging and an OH-PLIF technique analyzed flame structure and characteristics. Dynamic pressure was measured to check combustion instability, and exhaust gas emissions were evaluated for combustion characteristics. Key findings include critical co-firing rates for each nozzle based on NOx emission levels and combustion dynamics. As the hydrogen co-firing rate increased, flame length decreased, and NOx levels rose rapidly beyond 30%vol. Dynamic pressure oscillations showed no significant variations compared to natural gas combustion. This study successfully derived a characteristic operation map for a single nozzle based on the hydrogen co-firing rate.

Integrated scheme analysis and thermodynamic performance study of advanced nuclear-driven hydrogen-electricity co-production systems with iodine-sulfur cycle and combined cycle

A promising method for massive clean hydrogen production is the Very High Temperature Reactor (VHTR)-driven Nuclear Hydrogen Production (NHP) system using the Iodine–Sulfur (IS) cycle. Research on integrated scheme and thermodynamic performance of the VHTR-driven NHP system using the IS cycle has, however, received little attention up to this point, particularly when the combined cycle is employed as the power generation cycle. In order to bridge this research gap, this work proposed and studied two distinct VHTR-driven hydrogen-electricity co-production systems with the IS cycle and combined cycle: the independent operating system and the coupled operating system. Thermodynamics was used to model these two systems, and system thermodynamic performance was examined under the baseline operating conditions. A parametric study was further conducted on how two important operating parameters affected system thermodynamic performance. The primary findings indicated that the coupled operating system outperformed the independent operating system in terms of thermodynamic performance. Additionally, both the independent and coupled operating systems could produce hydrogen at the same rate of 289.8 mol/s, with net electrical power outputs of 61.07 MW and 102.7 MW, respectively, under the baseline operating conditions. Furthermore, it was discovered that a rise in the mass flow ratio for both operating systems would result in a notable reduction in system efficiency.

Simulation and Energy Analysis of Integrated Solar Combined Cycle Systems (ISCCS) Using Aspen Plus

The aim of this research is to simulate and analyze a combined power cycle (Steam turbine and gas turbine cycles) by studying the effect of changing the natural gas flow rate on the developed power. Therefore, reducing the amount of used natural gas in the combustion chamber of the gas turbine cycle from 9.2 to 4 kg/s showed a significant drop in the power produced by the gas turbine, i.e., from 123.7 to 57.7 MW. Additionally, this change in the combusted natural gas amount affected the heat recovered in both heat recovery steam generators (HRSGs), i.e., from 219.79 to 100.35 MW, respectively. Consequently, the amount of generated steam in the high pressure HRSGs and the power developed in the steam turbine changed from 60.88 to 27.79 kg/s and from 56.39 to 27.13 MW, respectively. A heat exchanger (HFHX) utilizing a heating fluid was used as an external source of energy to compensate the reduction in the generated heat and to increase the amount of generated steam up to 157.32 kg/s, which keeps the power plant capacity at 180 MW. Existing combined local plant data were used in this study and were simulated in Aspen Plus software V11. A sensitivity analysis was made to optimize the cycle operating conditions that use less natural gas and produce the same amount of power.

Hypomagnesemia as a predictor of the efficacy of combination EGFR-targeted drugs versus EGFR ADCs alone in HNSCC.

146 Background: EGFR-targeted drugs and ADCs in combination with EGFR-conjugated chemotherapy drugs can both cause hypomagnesemia. However, the predictive value of hypomagnesemia in response to treatment for head and neck squamous cell carcinoma (HNSCC) is unclear. Methods: This study retrospectively analyzed patients who participated in clinical trials of EGFR-targeted drugs and EGFR ADCs for HNSCC and solid tumors, from February 24, 2022, to March 25, 2024. The primary endpoint of the study was time to treatment failure (TTF). Results: This study conducted a retrospective analysis of 68 patients . All patients exhibited normal baseline serum magnesium levels prior to treatment, but following two cycles of treatment, varying degrees of hypomagnesemia were observed among them. Among the 46 patients who received 2 cycles of combination therapy with EGFR-targeted drugs, 33 were hypomagnesemia and 13 were normal serum magnesium, ORR[90.9%vs. 8.5%,(P=0.002)] (Table), TTF [151 days (95% CI: 212-380) vs. 87 days (95% CI: 52-230), HR 0.576 (95% CI: 0.270–1.230,P = 0.021)]. Among the 22 patients who received EGFR ADC alone for 2 cycles, 8 were hypomagnesemia and 14 were normal serum magnesium, ORR [37.5% vs.28.6%, (P=0.549)] (Table), TTF [97.5 days (95% CI: 68-300) vs. 108.5 days (95% CI: 60-160), HR of 0.877 (95% CI: 0.339–2.263; P = 0.547)]. Conclusions: The study demonstrates that, the occurrence of hypomagnesemia is associated with ORR and TTF following two cycles of combination of EFGR-targeted drugs, not observed in patients receiving EGFR ADCs as monotherapy in HNSCC. [Table: see text]

Flame evolution characteristics during ignition of a combined flameholder fueled by RP-3 liquid kerosene

This paper proposes a combined flameholder comprising a pilot flameholder and a bluff body flameholder, interconnected by a radial V-gutter. The configuration of this combined flameholder is widely utilized in current afterburners and ram combustors, and its outstanding performance in future advanced combined cycle engines has been proved. To avoid the issue of uniform airflow at the inlet observed in most previous studies, this research installed a diffuser to simulate relatively realistic inlet airflow conditions of combustor. Particle Image Velocimetry (PIV) and high-speed camera are employed to measure the flow field structure of the combined flameholder, as well as the ignition flame evolution process under inlet Mach number of 0.3 – 0.5, temperature of 500 – 700 K, and pressure of 0.05 – 0.1 MPa. This paper reveals the combustion organization method of the combined flameholder through combining flow field characteristics and the ignition flame evolution process. Furthermore, the research findings indicate that flame evolution processes, flame projection area, and ignition delay time are significantly influenced by the inlet conditions. The variations in these flame evolution characteristics with different inlet conditions are summarized and the contributing factors are analyzed. The results of the paper are expected to serve as a reference for the optimization and design of flame stabilization systems in current and future afterburners and ram combustors.

Predictive modeling of combined cycle power plant performance using a digital twin-based neural ODE approach

This study presents a novel digital twin-based predictive modeling approach to enhance the operation, maintenance, and management of combined cycle power plants. The research aimed to accurately forecast the combined cycle power (CCP) output, a critical performance indicator, to support intelligent decision-making for plant operators and engineers. The proposed framework leverages a neural ordinary differential equation (NODE) model integrated within a digital twin architecture to capture the complex, nonlinear dynamics of combined cycle gas turbine unit (CCGU) system. The predictive model was trained and validated using multivariate time-series data collected from a CCGU, achieving high accuracy with an R2_score of 0.993, a mean absolute percentage error of 0.325 %, and a root mean squared error of 1.518. Importantly, the NODE model demonstrated superior forecasting capabilities compared to traditional machine learning techniques. The digital twin (DT) concept enables seamless real-time data integration, physics-based models, and advanced data analytics to facilitate comprehensive CCGU lifecycle management. This novel approach provides operators with reliable, real-time insights to optimize plant performance, reduce maintenance costs, and improve overall sustainability. The generalization of the NODE model to an independent CCGU unit validated its applicability across diverse power plant configurations, highlighting the originality and practical value of the research. The key contribution of this work is the development of a digital twin-based predictive modeling framework centered on the innovative use of neural ordinary differential equations to enhance the operation and maintenance of critical energy infrastructure. This research advances the state-of-the-art in intelligent asset management for the built environment.

Effect of Fin Type and Geometry on Thermal and Hydraulic Performance in Conditions of Combined-Cycle Nuclear Power Plant with High-Temperature Gas-Cooled Reactors

Effect of Fin Type and Geometry on Thermal and Hydraulic Performance in Conditions of Combined-Cycle Nuclear Power Plant with High-Temperature Gas-Cooled Reactors

Acid rain resistance of geopolymer recycled pervious concrete featuring top-bottom interconnected pores under freeze-thaw cycles and fatigue loads

While pervious concrete with top-bottom interconnected pores enhances the performance of pervious concrete pavements, its resistance to acid rain under combined freeze-thaw cycles and fatigue loads remains unexplored. To fill this gap, this study investigated the influence of three different qualities of recycled coarse aggregates on the acid resistance, acid neutralization, and permeability of geopolymer recycled pervious concrete (GRPC) (Low-quality, middle-quality and high-quality geopolymer recycled pervious concrete (L-GRPC, M-GRPC and H-GRPC)) under the couple effects of simulated acid rain wet-dry cycle spraying, fatigue loads and freeze-thaw cycles. After experiencing the combined action of fatigue load and freeze-thaw cycle, only the compressive strength of L-GRPC increased slightly by 9.1 % after acid rain spraying, but it had a negative impact on the flexural strength. With the increase of coupling environmental factors, the neutralization depth of GRPC was less than 4 mm, and the permeability coefficient was higher than 0.5 mm/s. Furthermore, more gypsum crystals were observed in the SEM images, and new peaks corresponded to the gypsum phase (CaSO4) appeared at 2θ = 29.4° and 2θ = 21.6° in the XRD spectra. The research results provide a broader perspective for the application of GRPC in concrete pavement engineering in acid rain area.

Numerical and Experimental Study of Flow-Induced Vibrations in Micro-Tube Heat Exchangers

Abstract Thermal management presents an increasing challenge in future engineering systems, especially in applications like combined cycle precooling, waste heat recovery, and innovative propulsion systems. These systems face a growing demand for managing higher heat loads while coping with limited heat sink. Central to these thermal management systems is the heat exchanger, with micro-tube heat transfer emerging as a promising solution for future technologies. Micro-tube heat exchangers are becoming popular owing to their ability to significantly enhance the heat transfer surface area while maintaining a compact core volume. As the demand for high-performance, lightweight heat exchangers escalates, micro-tube heat exchangers are being designed to be increasingly compact yet highly loaded. This trend poses significant challenges to their structural integrity, particularly under harsh operational conditions. Flow-induced vibrations, a critical concern in the design of tubular heat exchangers, can lead to tube failures, compromising the safe operation of engineering systems. While the flow-induced vibrations of conventional-sized heat exchangers have been extensively studied, there is a noticeable gap in the research on similar phenomena in micro-tube heat exchangers. This paper details ongoing research at Reaction Engines Ltd to aid the design of safe and robust heat exchangers, focusing on the flow-induced vibrations in micro-tube heat exchangers and utilizing a cutting-edge laser vibrometry test facility. A predictive model, employing an unsteady flow simulation approach and eigenvalue analysis, has been formulated.

Reassessment of Thor® 115 parent metal performance including consideration of notch behavior

In recent years, the waning of creep rupture ductility in the long term, and sensitivity to creep damage tolerance of creep strength-enhanced ferritic (CSEF) steels were put under the spotlight. The loss of ductility and damage accumulation at stress concentrations may result in early failures of boiler components, and potentially result in severe economic impact and/or safety concerns. To address the potentially undesirable materials performance, the ASME Boiler and Pressure Vessel Code has recently introduced rules for identification of damage intolerant behavior by means of testing, and for design of boiler components with creep damage-intolerant CSEF steels, as Code Case 3048. As of today, only Grade 91 Type 2 material has been classified as a damage tolerant steel.The Thor® 115 (T115) CSEF steel has entered the market in recent years and has since been used for the construction of several combined cycle power plants. This CSEF steel was developed as an evolution to Grade 91, with chemical composition modifications to enhance the resistance to steam oxidation while ensuring long-term microstructural stability, and therefore permitting its use for the higher temperature boiler components, as an alternative to stainless steels. While chemical composition and manufacturing precautions prescribed for Grade 91 Type 2 also apply to T115, an assessment of the materials’ damage tolerance following design standards criteria, and including extensive metallurgical characterization, has not yet been published.This work presents up-to-date uniaxial creep testing results of T115 CSEF, and the derived creep-rupture ductility and damage tolerance parameter evaluation. In addition, results from notched bar creep testing are presented, illustrating the material's response to multiaxial stress states. Post-test metallographic examination of ruptured specimens was also performed and findings are discussed.

A Review for Combined Cycle Power Plants

A Review for Combined Cycle Power Plants

Study on the hypersonic separation of the parallel configuration of the combined cycle two-stage orbit vehicle

Study on the hypersonic separation of the parallel configuration of the combined cycle two-stage orbit vehicle

Incidence of hand-foot syndrome with protein kinase inhibitors in advanced hepatocellular carcinoma patients who received atezolizumab-bevacizumab combination.

Treatment of advanced HepatoCellular Carcinoma (HCC) is based on first-line (L1) combination of atezolizumab and high-dose (HD) bevacizumab while second-line (L2) refers one antiangiogenic protein kinase inhibitors (aaPKI). This prolonged antiangiogenic pressure let us to observe an increasing occurrence of Hand-Foot Syndromes (HFS) in patients receiving aaPKI after HD bevacizumab combination. This study reports observations and discussions about the evidence and hypothesis that could be made. Patients who received the L1 combination from September 1st 2020 to December 31st 2022 to identify L2 aaPKI. Demographic, biological, oncological data and occurrence of HFS were collected. In addition were collected the number of L1 combination cycles, type of aaPKI, and delay between last L1 cycle and L2 initiation. This study had a purely exploratory purpose, so no statistical analysis was planned. 17 patients received an aaPKI after the L1 HD bevacizumab combination with a median time of 26 days from last L1 cycle to L2 start. Five patients experienced HFS including grade 3 (n = 2) with sorafenib and cabozantinib. The HFS occurred with a median delay of 23 days (IQR: 21-28) from aaPKI start. Three patients experienced aaPKI-related dose-limiting toxicity. Proportion of patients experienced HFS in our cohort did not differ from pivotal trials data and the sample size do not allow to conclude. Hypotheses include timing of aaPKI start in HCC treatment, vascular toxicity at aaPKI start after HD bevacizumab discontinuation instead combination, patient-related outcome for a better understanding of these aaPKI-related HFS post HD bevacizumab.

Investigation of the impact of splitter rotation speed on mode transition characteristics of an over-under turbine-based combined cycle inlet

Investigation of the impact of splitter rotation speed on mode transition characteristics of an over-under turbine-based combined cycle inlet

Performance Improvement of Industrial Gas Turbine for Power Augmentation in the Nigeria Oil and Gas Sector

This paper provides a comprehensive overview of the electricity supply situation in Nigeria, focusing specifically on enhancing the performance of industrial gas turbines, GE GT13E2 (Afam Power Plant owned by FIPL) in Port Harcourt. The study encompasses two primary aspects. Firstly, it involves an examination of the nominal operating conditions of a combined cycle system and explores their dynamic performance through advanced simulations. Secondly, the research introduces a supplementary burner into the combined system and conducts a comparative analysis, considering factors such as system efficiency and power output. The power plant configurations are simulated using Gasturb14. The analysis is carried out by establishing the maximum attainable temperature in the Heat Recovery Steam Generator (HRSG), which determines the number of stages of supplementary firing that can be implemented. The results presented in this paper unveil the substantial potential for power generation with the addition of supplementary burners, indicating a remarkable increase in power output, yielding approximately 187.444 MW. However, this significant boost in power generation comes with an associated trade-off, wherein the overall system efficiency experiences a reduction. From an economic perspective, the additional power generated by the afterburner translates directly into increased revenue from electricity sales. Considering the average residential electricity rate in the U.S. as of February 2023, the calculated additional revenue from the afterburner amounted to approximately $25,641.58 per hour.

Integration of Steam Recovered from Molten Salts in a Solar Integrated Combined Cycle

In the current context of the energy transition, Integrated Solar Combined Cycle (ISCC) power plants are an alternative that are able to reduce carbon emissions from combined cycle (CC) power plants. In addition, the coupling to an energy storage system based on molten salts benefits hybridization, allowing the energy surplus to be to stored to cover peaks in energy demand. Because it is a recent technology, the determination of the optimal injection points for the solar-generated steam into the combined cycle is a critical issue. In this work, a thermodynamic model of a hybrid natural gas and solar thermal CC power plant has been developed using Thermoflex to analyze the integration effects in terms of efficiency and power. For all the steam injection candidate positions, the effects of ‘power boosting’ and ‘fuel saving’ operation modes have been simulated, considering operation conditions that are compatible with the useful range of molten salts. The results show that injection of steam at the high-pressure line before the steam turbine increases the cycle’s gross efficiency with respect to the reference case, estimating a reduction of carbon emissions of 6696 kg/h in the ‘fuel saving’ mode and an increase in gross power of 14.4 MW in the ‘power boosting’ mode. Hence, adapting current combined cycles for hybridization with solar power is a viable solution in the transition period towards more sustainable energy sources.

Energy and Exergy-Based Modeling and Performance Evaluation of a Natural Gas-Fired Combined-Cycle Power Plant

Energy and Exergy-Based Modeling and Performance Evaluation of a Natural Gas-Fired Combined-Cycle Power Plant

Studi Numerik Pengaruh Penambahan Turning Vane Terhadap Bentuk Aliran dan Distribusi Temperatur di Heat Recovery Steam Genertor (HRSG)

Tanjung Uncang Power Plant is one of the facilities in Indonesia that utilizes CCGT (Combined Cycle Gas Turbine). This cycle uses an HRSG (Heat Recovery Steam Generator) to heat steam using the exhaust gases from the gas turbine. At Tanjung Uncang's HRSG, the SOP requires that the gas turbine exhaust during cold start conditions must be below 400°C. Meanwhile, the gas turbine at Tanjung Uncang has a base load of 5 MW with a temperature range of 560°C - 580°C. Therefore, an asynchronous process is necessary to reach the FSNL (Full Speed No Load) condition for the gas turbine, with the damper angles set at 51°, 68°, and 90° for 45 minutes. Additionally, to achieve optimal conditions with the gas turbine running at 45 MW, a time span of 8 hours is required, which results in losses of up to 700 million. The extended time required can be due to uneven flue gas distribution, necessitating time for the HRSG to reach optimal conditions. This underscores the need to analyze the effects of adding turning vanes with angles of 35°, 53°, and 71°, and inlet temperatures of 400°C and 580°C on the characteristics of flue gas distribution. The analysis was conducted using CFD with ANSYS Fluent 2021 software. The simulation outputs include velocity vectors, velocity contours, and temperature distribution contours.

Studi Numerik Pengaruh Sudut Bukaan Damper dan Flue Gas Temperatur Terhadap Distribusi Temperatur Pada Heat Recovery Steam Generator (HRSG)

The Combined Cycle Gas Turbine Power Plant (PLTGU) utilizes the waste heat from the gas turbine to produce steam in a Heat Recovery Steam Generator (HRSG). The steam from the HRSG is then used to generate electricity in a steam turbine. In HRSG operation, several variables significantly impact its performance, including the damper angle and inlet temperature. At the Tanjung Uncang Power Plant in Batam, the manufacturer's standard operating procedure (SOP) requires that the exhaust gas temperature when the damper is open must be below 400°C. However, the gas turbine with an initial load of 5 MW has an exhaust gas temperature of 560°C - 580°C. Therefore, it is necessary to perform a gas turbine load release or FSNL (Full Speed No Load) to reduce the inlet temperature of the gas turbine. During FSNL, there are SOPs for diverter damper angles of 51°, 68°, and 90°. This leads to the need for analyzing the impact of diverter damper angles and inlet temperature on the flow pattern and temperature distribution. The analysis was conducted using CFD (Computational Fluid Dynamics) with ANSYS Fluent 2020 software. The variations used are diverter damper angles of 51°, 68°, and 90°, combined with inlet temperatures of 400°C and 580°C. The simulation outputs include velocity contours, temperature contours, and equivalent stress on the superheater tubes. The HRSG simulation results show that the flue gas is not distributed uniformly. The turbine exhaust gas only spreads along 4 – 11 meters, leading to slower steam production from the superheater. Additionally, when the superheater tubes are empty, the steady-state thermal and structural simulation results indicate that an inlet temperature of 580°C, whether at damper angles of 51°, 68°, or 90°, can cause a larger temperature difference between the inner and outer walls, ranging from 117.04°C to 125.5°C. This temperature difference can lead to thermal stress on the superheater tubes. This is shown in the S-N Curve for SA 213 T22 material, with a convection coefficient of 5 W/m² K (no steam), where the equivalent stress exceeds the endurance limit (infinite zone).