bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Ammonia/Methane Combustion in an RQL Combustor
Authors: Sun Jihao , Zhao Ningbo , Luo Shaowen , Zheng Hongtao
Published: August 2024

To gain a comprehensive understanding of the combustion characteristics of CH4-enhancing NH3 combustion in an industrial RQL gas turbine combustor, a numerical study was conducted using the CFD-CRN method. The study investigated flow and temperature distributions, flame structures, and NOx formation characteristics. Two methods of introducing CH4 were examined: premixing with NH3 before burning, and direct introduction in the inner swirl stage without premixing with NH3. The results revealed that NH3 combustion displayed a longer flame and higher NOx emissions compared to methane combustion. NOx was mainly generated at the flame front and the primary combustion zone. The addition of CH4 was found to increase combustion efficiency without significantly altering the flow and temperature distributions. Direct introduction of CH4 showed higher combustion efficiency compared to the premixing method. Moreover, the addition of CH4 contributed to an increase in NOx emissions. The direct introduction of CH4 in the inner swirl stage demonstrated promising results for NH3 combustion. This approach enhanced combustion efficiency and reduced NOx emissions without requiring fuel premixing systems.
A Comparison of Model Predictive Control Architectures for Application to Electrified Aircraft Propulsion Systems
Authors: Hill Elyse D. , Simon Donald L. , Connolly Joseph W.
Published: August 2024

As electrified aircraft propulsion (EAP) systems continue to mature, more sophisticated hardware and software are being developed to balance operations among electric machines and gas-turbine engines. In hybrid-electric propulsion systems, the increased complexity resulting from integrating turbine-engine shafts with electric machines necessitates control methodologies to account for various physical domains. Ideal controllers for hybrid-electric engines manage systems, subsystems, and their interactions in a coordinated fashion, able to account for safety and performance goals while being computationally efficient. In a previous work, linear model predictive control (MPC) schemes were implemented in centralized and distributed frameworks on a nonlinear turbofan engine model as a proof of concept. However, these schemes were not evaluated for computational complexity, prompting further study. The research presented here develops hierarchical MPC schemes to reduce the computational burden of the previous MPC schemes. A two-tier framework is implemented, where a slower sampling MPC controls electric machines and determines fan-speed tracking goals for a faster sampling controller, which is either a MPC or a proportional-integral (PI) controller. The proposed designs are compared to the centralized MPC investigated previously, and performance is measured via fan speed tracking error, energy storage state-of-charge, and computation time. Results reveal that the hierarchical MPC scheme employing a lower-level PI controller improves computation time while maintaining comparable tracking and state-of-charge regulation to the centralized scheme.
Investigation of Pressure Effects on Combustion Characteristics of Hydrogen Annular Micro-Mixing Nozzles
Authors: Liu Jian , Qiu Penghua , Wang Xiyu , Hu Qiming , Liu Li , Zhang Linyao , Xing Chang
Published: August 2024

In pursuit of achieving near-zero emissions and preventing flashback, micro-mixing combustion technology has been developed and implemented in hydrogen gas turbines. This investigation proposed an annular micro-mixing nozzles comprising seven annular nozzles arranged in a regular hexagonal pattern. Experimental investigations based on OH* Chemiluminescence with OH-PLIF synchronous measurement technique were performed. Results indicate that with increasing pressure, the flames become smaller and shorter, and the interaction between flames weakens compared to atmospheric pressure. At higher pressures, the flames predominantly rely on the bluff bodies of the annular nozzles for stability. This leads to a more concentrated flame reaction zone, increased local heat release, and an exponential increment in NO emissions. However, the experiments reveal that at combustion pressures equal to or below 0.2 MPa., NO emissions under the test conditions remain below 10ppm (@15%O2).
Numerical and Experimental Study on Flow Loss Reduction Effect of Micro-Textured Surface on Compressor Cascade
Authors: Wang Liyue , Wang Cong , Sun Gang , Feng Jinzhang
Published: August 2024

Surface structures with excellent aerodynamic performance can reduce the flow loss of aero-engine caused by the harsh working environment to a certain extent. Inspired by the dentate micro-texture over shark skin, micro-texture surface has been proposed as an emerging and effective means to reduce the flow loss of aero-engine. However, for a realistic compressor cascade configuration with micro-texture, using massive grids to describe the flow within the boundary layer makes the simulation of multi-scale flow field unfeasible. This paper presents an innovative numerical simulation method for compressor cascade with micro-textured surface using a machine learning wall modification model. The wall modification model is trained based on the near-wall microflow data obtained by LBM, which can reproduce the flow effects of micro-textured surface. The mechanism of reducing the total pressure loss of the compressor cascade is that the micro-textured surface structure delays the laminar transition and decreases the intensity of the turbulent region. In addition, wake measurements through experiment are performed to validate the proposed multi-scale numerical simulation method in the high-speed linear cascade wind tunnel. This paper demonstrates the flow loss reduction effect of micro-textured surface on compressor cascade through numerical and experimental study.
Performance of sCO2 Cycles for Waste Heat Recovery and Techno-Economic Perspective As Gas Turbine Bottoming Cycle
Authors: Thielens Vincent , Demeyer Frederiek , De Paepe Ward
Published: August 2024

Supercritical carbon dioxide (sCO2) cycles are compact, cost-effective and widely adaptable to various heat sources, including the waste heat from gas turbine (GT) exhaust gases. While the addition of a steam cycle enhances the typical 40%-efficiency of GTs up to 60%, their substantial investments render them less appealing for smaller GTs. This creates an opportunity for sCO2 cycles, but a comprehensive comparison of their performance with that of steam across a range of applications remains lacking. Moreover, their applicability to various industrial scenarios based on existing installations is missing from a techno-economic standpoint. To address these needs, four promising sCO2 cycles are evaluated and optimized using Aspen, and compared with the simple steam cycle. Their techno-economic performances are then investigated for 20 industrial GTs of different size up to the larger CCGT units incorporating amine-based carbon capture systems. Due to the significant investments required by the carbon capture unit, the implementation of a CC unit is only investigated for the largest CCGT units. The analysis yielded performance maps demonstrating comparable performances for sCO2 and steam cycles, as well as significant techno-economic advantages for sCO2 bottoming cycles for smaller GTs. However, when it comes to larger GTs combined with reheats and expansions steam cycles, sCO2 cannot outperform them in current technological standards. Nevertheless sCO2 cycles offers an attractive alternative, facilitating cogeneration. Among the different approaches designed to integrate the heat requirements of amine-based capture, steam cycles have always proved more suitable because of the thermal stability of amines. In conclusion, the research underscores the cost-effectiveness and adaptability of sCO2 cycles for heat recovery applications, particularly as bottoming cycles for smaller GTs, while larger GTs present a challenge. The work conducted sheds light on the substantial promise of sCO2 cycles, encouraging further exploration and implementation of these systems in the energy sector.
Generalized Method for the Conceptual Design of Compact Heat Exchangers
Authors: Miltén Petter , Jonsson Isak , Lundbladh Anders , Xisto Carlos
Published: August 2024

The paper introduces a novel method for generalized heat exchanger design and evaluation, freeing the process from predefined geometries. It aims to facilitate early-stage conceptual exploration, allowing the designer to make informed decisions. The paper explores heat transfer and fluid friction principles in order to set key parameters for estimating aerothermal performance, introduced by LaHaye. Arguing against a single metric, the paper proposes a custom cost function for evaluating the integrated generalized heat exchanger. A case study applies the method to a particular aircraft engine scenario, using cost functions to evaluate intercooler designs based on pressure loss and heat transfer surface weight. The study determines suitable heat exchanger families for further development, considering factors like finned area, compactness and flow distribution.
Compressor Development for CO2-Based Pumped Thermal Energy Storage (PTES) Systems
Authors: Held Timothy J. , Miller Jason , Sedlacko Kyle , Cameron Joshua , Morris Scott , Kang Jeongseek , Turner Mark
Published: August 2024

Pumped thermal energy storage (PTES) offers a cost-effective means to store electrical energy for long duration by utilizing a heat pump cycle to transfer thermal energy from a low temperature reservoir (LTR) to a high temperature reservoir (HTR). A key component of the PTES system is the heat pump compressor, which represents a significant driver to the cost, performance and operating characteristics of the PTES system. At the power rating of the charging process (> 100 MW), traditional compressor scaling charts indicate that the operating conditions needed would be best served by a multistage axial compressor. While frame gas turbine compressors at these power ratings exist and operate at higher pressure ratios than needed for the CO2 PTES system, the inlet pressure and fluid density of this application exceeds experience values. The conceptual design of a large-scale CO2 axial compressor was completed, including mean-line estimates of the compressor performance at full power conditions. At steady state, full power operation, the isentropic efficiency and mechanical efficiency of the compressor have significant impact on the cycle design and round trip efficiency of the PTES system. The results of the conceptual design were used to refine the PTES cycle design, and updated operating conditions provided for further aero design optimization. An important characteristic of the PTES system is its ability to charge at variable rate, which provides significant challenges on compressor operability, especially for a compressor that will be coupled to a fixed-speed synchronous motor. Cycle studies of variable charging rate processes have been conducted, and the impact of compressor operating map characteristics explored. Based on initial modeling studies, single compressor operation can be achieved down to at least 50% of rated power, with further reductions possible depending on the characteristics of the compressor map speedlines.
Comprehensive Experimental Assessment of Unsteady Pressure and Heat Flux in a Small-Core Turbine Over-Tip Shroud
Authors: Castillo Sauca Antonio , Bhatnagar Lakshya , Inhestern Lukas Benjamin , Paniagua Guillermo
Published: August 2024

For novel high-speed small core turbines, with tip clearance below 0.5mm, even small blade-to-blade tip clearance variation is significant. The assessment of these complex flows is pertinent to the design of the next generation of small-core turbines. This manuscript provides a thorough experimental analysis of the shroud’s unsteady heat flux and static pressure in a small-core squealer-tip blade turbine. Atomic Layer Thermopile sensors (ALTP) and fast response pressure transducers were used to perform high-frequency acquisition at 2MHz around the 51% axial blade chord on the shroud. Measurements were taken at engine-representative conditions at several operational conditions and tip clearances. The signals were phase-locked averaged over the revolution period and synchronized to identify individual blade and row signature. The linear relationship between the rotational tip Reynolds and the static pressure ratio across the blade tip reveals the transition point to reverse over-tip flows. Total heat flux is decomposed into the different steady and unsteady heat flux contributions. It is demonstrated that the adiabatic wall temperature governs the unsteady heat flux and contributes to one third of the total surface heat flux. A linear trend was observed between the unsteady heat flux and the tip clearance measured at the pressure and suction side rims. Similar trends were observed between the local heat flux and the pressure ratio across the tip. A comparison with CFD predictions highlights some limitations on resolving the detached and secondary flows, evidencing the necessity of complementary experimental data.
Multirow Film-Cooling Effectiveness of Vertically Oriented Slot Cross-Section Diffusion Holes on a Turbine Nozzle Guide Vane Suction Surface
Authors: Hu Jia-Jun , An Bai-Tao
Published: August 2024

In this paper, a multirow film cooling effectiveness experiment was conducted on a turbine nozzle guide vane suction surface using the pressure-sensitive paint (PSP) measurement technique. Five rows of film holes were designed at the suction side with a streamwise staggered arrangement and a 6D spanwise hole spacing. Two diffusion holes constructed based on a vertically oriented slot cross-section with 14 deg and 20 deg exit expansion angles were tested. A fan-shaped hole and a horizontally oriented slot cross-section diffusion hole were chosen as the baselines, and both had a 14 deg exit expansion angle. The experiment was carried out in a linear cascade with a mainstream Renolds number of 62000, a mainstream turbulence intensity of 3.7%, and a coolant-to-mainstream density ratio of 1.5. The four averaged blowing ratios ranged from 0.5 to 2.0. The results showed that, regardless of the blowing ratio, under intense multirow film interactions, the vertically oriented slot cross-section diffusion holes can always produce uniform and consistent film coverage on the vane suction surface. The vertically oriented slot cross-section widens the distance between the up- and downstream walls and narrows the lateral width, thereby weakening the influence of the entrance “jetting effect”. The resulting flow pattern can adapt to a larger exit expansion angle. In addition to the smaller difference under a low blowing ratio, two vertically oriented slot cross-section diffusion holes yield prominently greater multirow effectiveness than do the horizontally oriented slot cross-section diffusion hole and conventional fan-shaped hole, in which the case with a 20 deg expansion angle performs better.
Flow Analysis of Various Intake Configurations of an Unmanned Aircraft Considering External Flow and Different Flight Conditions
Authors: Grois Andreas , Remiger Jonas , Stößel Marcel , Krummenauer Michael , Kozulovic Dragan
Published: August 2024

The importance of unmanned aircraft systems (UAS) is rapidly increasing in various fields of aerospace development. Modern military UASs require a compact full-engine integration to optimize the use of the limited installation space and to prevent radar reflections from the easily detectable fan. These goals are commonly achieved by highly bent intake ducts or by the position of the intake’s inlet section. However, an inconvenient position and an extremely compact intake shape can lead to strong flow inhomogeneities and influence the engine’s stability and performance. Previous studies at the Institute of Jet Propulsion (IJP) have focused on evaluating the flow distortions at the isolated intake duct. The effect of the external flow and the aircraft configuration was neglected. In this work, the impact of external flow on the intake aerodynamics for different aircraft intake configurations at various flight conditions, such as angles of attack or flight Mach numbers, is investigated. A generic remote carrier is used as a virtual test platform on an overall mission that covers most of the aircraft’s flight envelope. The intake systems investigated comprise strongly bent ducts and flush-intake configurations. Different flow inhomogeneities parameters allow detailed consideration of diverse aerodynamic phenomena along the intake and their impact on the Aerodynamic Interface Plane (AIP) flow. As an example, one parameter is the distorted mass flow fraction based on the average deviation from the mean total pressure. Traditional turbomachinery distortion parameters such as the DC60 or SC60 are also analyzed to allow a comparison with existing engine integration studies at the IJP and the open literature. In addition, these evaluation capabilities also enable the use of different flow distortion parameters as input to the IJP’s Engine Mission Simulation System (EMSS) to study the effects on compressor behavior and engine performance (see ASME Turbo Expo 2024 by J. Remiger). For this study, the steady-state RANS simulations of the entire remote carrier were performed using ANSYS CFX flow solver. Initial low-fidelity simulations were done using the EMSS to calculate the flight conditions and, therefore, the boundary conditions for the CFD setup. The study reveals that the external flow significantly influences the flow inhomogeneities in the intake and, therefore, cannot be neglected by evaluating an applicable flight case of a coupled aircraft and intake system. It turned out that a change in the angle of attack and the axial positioning of the intake caused a significant variation in the inflow condition. This major impact is noticeable in the distortion parameters along the intakes and leads to a sharp change in the distortion pattern at the AIP.
Numerical Investigation on the Influence of Wet Compression Aerodynamic Performance of Multi-Stage Transonic Compressor
Authors: Zhu Zihuan , Ming Lele , Zhang Xinze , Wu Yadong , Ouyang Hua
Published: August 2024

In this paper, the gas-liquid two-phase flow in a multistage transonic compressor was numerically simulated based on the Euler-Lagrange method. The influence of wet compression aerodynamic characteristics of the compressor was investigated under different spraying conditions (spraying rates and droplet sizes). The results indicated that the compressor choking boundary moves to a smaller flow rate after spraying. Wet compression improves efficiency of the compressor. The evaporation cooling effect of wet compression decreases total temperature ratio and increases the specific power, resulting in the promotion of the total pressure ratio. After the water droplets are injected into the compressor, due to the small rise of the airflow temperature in the first stage area, the evaporation cooling effect of droplets is weak. Negative effects of droplets lead to a decreasing in the first-stage pressure ratio after spraying. As water droplets move downstream, the gradual increase in airflow temperature enhances the evaporation cooling effect, thereby improving the compressor performance. Water droplets migrate radially inside the compressor and gather toward the blade tip area, causing the gas phase mass flow inside the compressor to be redistributed in the radial direction. Wet compression leads to an increase in the compressor twist velocity, enhancing the capability of the rotor blades to perform work on airflow.
Gas Turbine Combined Cycle System Integration with Carbon Capture Plant for Improved Value
Authors: Sammak Majed , Smith Raub , Kulkarni Parag , N. Ravi , Sholes John
Published: August 2024

The aim of this study is to analyze methodologies that can reduce performance impact on natural gas combined cycle (NGCC) plant when integrated with carbon capture plant (CCP) and lower the capital expenditure (CapEX) associated with carbon capture. The conventional approach of providing steam to the carbon capture reboiler for CO2 regeneration is the use of a bolt-on system, which entails an external auxiliary boiler. The study presented four promising technologies that can enhance the integration of NGCC with CCP: steam integration, exhaust gas recirculation (EGR), gas turbine improvement, and enhanced control system. The paper analyzes how EGR can decrease CCP CapEX and footprint, focusing on equipment with the most significant CapEX reductions.

The steam integration approach refers to extracting steam from various locations in the steam cycle such as the crossover between the intermediate pressure (IP) and low pressure (LP) sections of the steam turbine using a throttle and control valve.

The EGR method refers to recirculating a part of the flue gas from the stack back into the gas turbine inlet, where it is combined with ambient air. The analysis reveals that EGR contributes to an increase in the concentration of CO2 in exhaust while simultaneously decreasing the amount of flue gas directed to the CCP. This dual effect is expected to result in a reduction in both the overall CCP CapEX and its footprint. The study delves into the impact of EGR return temperature and EGR ratio on the output of gas turbine and combined cycle systems.

NGCC performance has been evaluated utilizing GE’s internal mass and heat balance tools. CCP performance and cost were assessed using commercial tools ProMax and Aspen Process Economic Analyzer.

The study demonstrates that providing steam to CCP through a steam integration solution is more effective than using a bolt-on solution. The steam integration solution has a potential to achieve up to 30% decrease in CCP CapEX compared to the bolt-on solution utilizing an auxiliary boiler. In addition, using a 30% EGR in the steam integration solution decreases the CapEx for the CCP by an additional 7%.

EGR return temperatures ranging from 27°C to 44°C at 1°C intervals are considered, alongside studied EGR ratios of 10%, 20%, 30%, and 40%. The analysis demonstrates that the output of the studied NGCC increases at all studied EGR return temperatures and EGR ratios, reaching a peak at a 35% EGR ratio before leveling off.
Investigation of Predictive Methods for Flow Resistance in Channel With Asymmetric Rib Arrangements Under Rotating Condition
Authors: Xu Yunteng , You Ruquan , Che Junxin , Li Haiwang
Published: August 2024

Turbine blade cooling demands vary between the leading and trailing surfaces. To achieve a refined design of blade cooling structures and maximize the utilization of cooling air, an asymmetric ribbed structure design method is proposed. The prediction of resistance is a crucial issue that urgently needs to be addressed in the design of this structures. Numerical simulation (Large Eddy Simulation) is adopted to investigate the flow characteristics and resistance properties of straight channels with asymmetric (different rib spacing) and symmetric rib arrangements, within the range of Re = 30000 and Ro = 0–0.5. The ribbed channel’s friction factor is analyzed under rotating condition. The asymmetric effects within the rotating ribbed channel and the mechanism of rotational impact on the flow are revealed, and a predictive method for the flow resistance in rotating asymmetric ribbed channels is summarized and proposed. Placing asymmetric ribs on the wall causes the airflow to shift and squeeze toward positions of lower resistance, creating a “rib-induced pushing effect” and leading to a trend of resistance between wall surfaces moving towards equilibrium development. Affected by this effect, the peak streamwise velocity shifts towards the side without ribs by 11% in single-sided ribbed channel under stationary conditions. In double-sided ribbed channels, the peak streamwise velocity increases by 13% compared to a smooth channel. Under rotational conditions, the Coriolis force effect acts in conjunction with the rib-induced propulsion effect on the airflow, resulting in regular flow within the channel. Therefore, the Coriolis force effect and ribbed-induced pushing effect are the main factors affecting the flow resistance in the rotating asymmetric rib channel, and the flow resistance coefficient in the rotating asymmetric ribbed channel can be judged according to their magnitude. In this paper, a method for predicting the flow resistance of asymmetric ribs is proposed, considering the coupled effects between wall surfaces.
Development of 1400°C (2552°F) Class Ceramic Matrix Composite Turbine Shroud and Demonstration Test With JAXA F7 Aircraft Engine
Authors: Watanabe Fumiaki , Yamanaka Shohei , Noguchi Toshihito , Hirano Hiroto , Sato Hayao , Makida Mitsumasa , Hojo Masahiro
Published: August 2024

Serviceable temperature for turbine components material of aircraft engines is increasingly needed to be higher in order to improve engine performance and durability. Recently SiC/SiC Ceramic Matrix Composites (CMCs) are commercialized instead of Ni-base super alloys which have been used for turbine components. The Authors developed 1400°C (2552°F) class CMC material system which consist of SiC fibers and SiC matrix and ytterbium silicate base matrix, aiming for higher temperature capability on consignment from the New Energy and Industrial Technology Development Organization (NEDO). Then they designed and manufactured high pressure turbine shrouds for aircraft engines using that 1400°C class material system, and they conducted strength tests and thermal cycle tests for turbine shroud components. After that they conducted engine tests for the CMC turbine shrouds demonstration in the actual engine environment jointly with the Japan Aerospace Exploration Agency (JAXA) in 2021. The test vehicle for this demonstration engine tests was the F7 engine which was introduced in 2019 at JAXA as the first case of a commercial transfer of the F7-10 turbofan engine which was developed by the Acquisition, Technology & Logistics Agency (ATLA) for the P-1 maritime patrol aircraft. The engine test was conducted for over 75 hours including over 35 hour hot time. After the test teardown inspection was conducted. No spallation of EBC, no recession and no wear on CMC turbine shrouds were found. As the result of the microstructure observation for cut faces of CMC turbine shrouds, no oxidation in SiC fibers, no chemical reaction in matrix, and no microcrack in matrix were found, but, some oxidation in fiber interface coating and microcrack in EBC were found. Bending strength tests with specimens cut out from CMC turbine shrouds were conducted in order to survey the degradation of material. Two types of specimens were prepared. One was the specimen cut out from the high temperature portion. The other was the specimen cut out from the high stress portion. As the result of bending test, the strength of the specimens cut out from engine tested shrouds were equivalent to the strength of the specimens cut out from unused shrouds. The CMC turbine shrouds after engine test were determined to be serviceable, therefore the developed 1400°C class CMC shrouds was proven to be sound in an actual engine environment.
Application of Ultrasound Gas Detectors in Gas Turbine Package
Authors: Sorrentino Viola , Viti Riccardo , Minotti Stefano , Tonno Giovanni , Azzini Francesco
Published: August 2024

A Gas Turbine (GT) usually has hot surfaces and it is installed with the fuel gas system inside a ventilated acoustic enclosure. Several connections are present in the fuel gas system and in the GT combustion chamber that could become sources of leakage. For this reason, the introduction of hydrogen as fuel for Gas Turbines requires attention in the design phase due to properties such as a large flammability range and low ignition energy. To prevent hazardous events in case of unexpected leakage, it is required to have a Gas Detection system which command an emergency shut down of the GT train. Fundamental characteristics of a gas detection system include its reliability and the response time. Since hydrogen is more reactive than conventional natural gas, the time required to detect gas leaks becomes a crucial factor. For this reason, an intervention as fast as possible is strongly recommended. Ultrasound gas detectors have these features but they regularly work in open environment and there is no evidence of their application in GT enclosures. This work describes some tests of Ultrasonic Gas Leak Detectors carried out in operating GT package. Ultrasound gas detectors were installed in several locations inside a GT enclosure and tested during different GT load conditions up to Full Speed Full Load. Hydrogen leaks have been simulated using helium as surrogate to verify GD performances. Promising results achieved from this test are shown in this paper.
Optimum Design of Scaled-Down Wind Turbines Based on Field Data
Authors: Jauregui Juan , Franco Jesus Alejandro
Published: August 2024

This paper presents a method for designing wind turbine-scaled models based on field data. The development of more giant wind turbines significantly contributes to power generation with renewable sources. Thus, scaling models are a crucial element in the design process of large wind turbines. The scaling process requires careful consideration of the system’s physical laws and similarity criteria. Scaling methods depend on the prototype’s operating conditions (full-size wind turbine) and the experimental conditions (scaled model dimensions and wind tunnel capabilities). The data from a field turbine is the input for creating a scaled model and testing it in a wind tunnel. However, in general, there are few field data available. The task is not straightforward since most operating conditions must be satisfied, and the similarity criteria could result in different scaled models and wind tunnel conditions. The drawback of the scaling models is their inability to reproduce all the operating conditions. The method presented here considers most of the recommended similarities, including the dynamic modeling of the system. The final scaled-model design was obtained by modifying the blade profile to reproduce similar power, pitch momentum, and trust coefficients, keeping the same twist angle as the prototype. Since the possible profiles are too large, the best approximation was obtained by comparing the coefficient curves of different blade profiles with the prototype’s curves. The curves were calculated using the BEM method. It was found that the scaled model has an entirely different design.
Thermodynamic Analysis of a Novel Transcritical CO2 Pumped Thermal Energy Storage System With a Vortex Tube Driven by Photovoltaic Thermal Collector
Authors: Chen Liangqi , Lou Juwei , Wang Bofeng , Wang Jiangfeng , Zhao Pan , Dai Yiping
Published: August 2024

With the growing global emphasis on the utilization of renewable energy sources, the field of energy storage has garnered significant attention. Among the various storage technologies, Pumped Thermal Energy Storage (PTES) stands out as a highly adaptable solution that is not limited by geographical boundaries. This flexibility makes PTES an attractive option for a wide range of applications, as it can be implemented in diverse settings to support the integration of renewable energy into power systems. To enhance the roundtrip efficiency of PTES, this paper proposed a PTES system based on the transcritical CO2 cycle. Furthermore, the proposed system is combined with photovoltaic thermal (PVT) collectors to improve the coefficient of performance (COP) during the energy storage process by recovering the waste heat of PVT collectors. PVT can not only improve the power efficiency of photovoltaic, but also increase the inlet temperature of compressor to reduce the energy consumption. Considering the low critical temperature (about 31°C) of CO2, the vortex tube is utilized as a condensation equipment in the proposed system to condense CO2 to liquid under ambient conditions, so that the proposed system can be more flexible in the process of application. A computational framework is developed to examine the impact of parameters on thermodynamic performance. The sensitivity analysis of key parameters such as temperature of storage tank, turbine inlet pressure and vortex tube outlet pressure are carried out to determine the energy storage characteristics of the proposed system. In addition, multi-objective optimization is performed using a genetic algorithm to achieve the optimal design performances including round-trip efficiency and average electricity growth rate of PVT.
Lean Blow-Off Behaviour of Premixed Bluff-Body Stabilized Hydrocarbon-Air Flames and Ammonia/Hydrogen/Nitrogen-Air Flames
Authors: Su Tong , Xu Boyan , Bastiaans Rob , Worth Nicholas A.
Published: August 2024

Ammonia blends have great potential to be utilized in gas turbine combustors as carbon-free fuels. This paper investigates and compares the lean blow-off behavior of premixed bluff-body stabilized hydrocarbon flames and ammonia/hydrogen/nitrogen flames both experimentally and numerically. Simultaneous high-speed PIV and OH-PLIF are employed to resolve temporal flame and flow field information, allowing the curvature and hydrodynamic strain rates along the flame surfaces to be calculated. OH* and NH2*, chemiluminescence images are also used to examine flame structures at the same bulk flow velocity but at four equivalence ratios which span a range of flame stability behaviour from far away from to near lean blow-off. The NH3/H2/N2 flames blow off at leaner conditions as the hydrogen volume fractions increase. A NH3/H2/N2 (70%/22.5%/7.5%) flame is slightly more resilient to lean blow-off compared with methane and propane flames at a velocity of 20 m/s despite having a significantly lower laminar flame speed. The flame structure for all fuel blends change from a ‘V-shape’ to ‘M-shape’ when approaching lean blow-off, as observed in the Abel deconvoluted OH* fields for methane and propane flames and NH2* fields for ammonia fuel blends, which can result in incomplete reactions and finally trigger the lean blow-off. However, the strong OH* intensity in the shear layer near flame root for the NH3/H2/N2 flames indicate that a robust reaction is maintained in this region for this fuel blend, increasing flame stability. The flame and recirculation zone lengths both decrease with equivalence ratio. Widely-distributed positive curvature along the flame surface of the ammonia fuel blend flames which have a Lewis number less than unity, may also enhance combustion for these flames. As blow-off is approached hydro-carbon flame fronts undergo increasing strain rates along their flame fronts, which may be due to their migration towards the inner shear layer region of the flow. In comparison the strain rates along NH3/H2/N2 flames fronts do not change significantly as blow-off is approached due to less dramatic changes to the flame shape. The faster consumption rates of hydrogen than ammonia near the flame root for the ammonia blend flames, and the lower temperature loss compared with the adiabatic temperature may also contribute to the stabilization of ammonia blends near lean blow-off.
A Physics-Informed Deep Learning Approach for HDGT Compressor Performance Simulation
Authors: Wei Manman , Jiang Xiaomo , Liu Yiyang , Ge Xin
Published: August 2024

Owing to the complicated structure of a heavy-duty gas turbine, its efficiency is largely impacted by the ambient and operating conditions. Real-time control and predictive maintenance based on performance model becomes a powerful method widely utilized to improve the operating efficiency of the gas turbine. However, the thermodynamic balance-based performance model is hardly applied for real-time control and predictive maintenance of the gas turbine due to its time-consuming computation. In this study, we designed a deep learning operator network (DeepONet) model to simulate the thermodynamic heat balance of axial compressor. The DeepONet is then employed to rapidly predict the efficiency and mass flow of the compressor. First, a physics-based model is built by seamlessly integrating the thermodynamic balance mechanism, structural characteristics, and operating data of the axial compressor. Then, a high-efficiency and high-precision DeepONet model is constructed with reference to the structure of the physics-based model. The yielded surrogate model is utilized to quickly predict key parameters of the compressor including its mass flow and efficiency. The accuracy and effectiveness of the proposed methodology is evaluated by comparing the prediction outputs with measured data through a case study of an axial compressor. A comparison study with conventional long short-term memory model shows that the proposed DeepONet-model provides a promising tool for performance-based smart maintenance of the compressor.
Prediction of High-Speed Hydraulic Dynamometer Safety Envelope Base on Deep Learning Neural Network
Authors: Chen Guo , Xiao Hong , Zhou Li , You Rui
Published: August 2024

High-speed hydraulic dynamometer is widely used for turbine component experiment in aircraft engine area. It usually works through measuring main performance parameters of turbine for verifying design method by absorbing huge shaft work which is passed from turbine. However, its water flow can generate strong turbulence phenomena between impellers in dynamometer’s case. In addition, high water temperature may generate cavitation phenomenon and cause high-frequency pressure pulsation. Both can lead to dynamometer’s performance degradation.

Artificial experience diagnosis, though not suggested, is used commonly to prevent high-speed hydraulic dynamometer from working unsteadily. This method depends on the experience of workers, which may cause fuzzy definition and lead to safety hazard.

In this paper, we propose a two-stage model of highspeed hydraulic dynamometer based on deep learning neural network. It utilizes the ideas of Transformer Model, which makes our model become more sensitive and stable. Accuracy and stability are proved by verifying actual device operation data. Based on two-stage model, we can draw work safety envelope by predicting performance parameters that delimit the safety boundary. Follow this guide workers can be able to make operation safer and stabler.
Burner and Flame Transfer Matrices of Jet Stabilized Flames: Influence of Jet Velocity and Fuel Properties
Authors: zur Nedden Philipp , Eck Mattias Ettore Giulio , Lückoff Finn , Paschereit Christian Oliver , Orchini Alessandro
Published: August 2024

To achieve the decarbonization of electrical power generation, gas turbines need to be upgraded to combust high-hydrogen content fuels reliably. One of the main challenges in this upgrade is the burner design. A promising burner concept for a high-hydrogen fuel mixture are jet burners, which are highly. flashback resistant thanks to their high bulk velocity. Due to its non-acoustically compact extension and the presence of hydrogen in the fuel mixture, new challenges arise in assessing the (thermo)acoustic response of this burner design. A burner transfer matrix (BTM) and the flame transfer function (FTF) or transfer matrix (FTM) are typically measured with the multi-microphone method (MMM) to assess the performance of new burner types in relation to thermoacoustic stability. With the switch towards hydrogen, the fuel/air mixture is significantly altered in its properties regarding the speed of sound and density, which are of fundamental importance for acoustic waves propagation and their reconstruction via the MMM, as highlighted in recent work. In this work, we extend this discussion by studying the influence of the gas composition within the burner when measuring BTMs, and its indirect effect on the assessment of FTFs. Experimentally, we achieve this by adapting the preheating temperature during the measurement of the BTM with a non-reactive mixture in order to match the speed of sound of the hydrogen-air mixture required to flow in the burner under reactive conditions. Additionally, we present an analytical model for the jet burner transfer matrix, which is validated against the experimental data. Since the BTM is fundamental for the assessment of the FTM and FTF, the propagation of the error of changing fuel mixtures in the burner is evaluated. The influence of the variation in reactant composition of the BTM on the FTM assessment is noticeable, particularly in the gain of the FTFs. Furthermore, the influence of the total mass flow and, thus, the bulk flow velocity on the FTF is analyzed.
Experimental Investigation Into the Generation Mechanisms of Additional Loss due to Incoming Wakes in Low-Pressure Turbine Cascades
Authors: Kodama Hidekazu , Funazaki Ken-ichi
Published: August 2024

For low-pressure (LP) turbines, there exists the loss due to incoming wakes, whose magnitude is sometimes comparable to the profile loss. For a substantial improvement in LP turbine performance, it is necessary to reduce not only the profile loss but also the additional loss. This paper aims at clarifying the generation mechanisms of additional loss so that a design guide for reducing the additional loss is introduced. A parametric set of boundary layer measurements was conducted using a low-speed linear turbine cascade test facility with a moving-bar mechanism for blades with no separation bubble on the suction surface. Four different wake-passing frequencies and three different Reynolds numbers were examined. From the boundary layer measurements, the streamwise variations of the boundary layer integral parameters were obtained along the rear part of the blade surfaces. Also, the wall-normal profile of root-mean-square of streamwise velocity fluctuation was obtained at each boundary layer measurement location. The sources of additional loss were derived by using the measured boundary layer integral parameters together with the estimated profile loss under each flow condition. It was found that the wake-boundary layer interaction loss was attributed to the breakdown of Klebanoff streaks generated in the suction surface boundary layer and the magnitude of the loss was determined by the wake-passing frequency.
Development of a Hydrogen Micro Gas Turbine Combustor: NOx Emissions and Secondary Air Injection
Authors: Tanneberger Tom , Mundstock Johannes , Rex Christoph , Rösch Sebastian , Paschereit Christian Oliver
Published: August 2024

On the way to defossilization, green hydrogen is a promising way to substitute natural gas and oil in the gas turbine industry.

In the scope of the H2mGT project, a micro gas turbine (mGT) burner with 100 % hydrogen firing is developed and validated. The project is funded by the German BMWK and it is a collaboration between TUB and the manufacturer Euro-K GmbH. It consists of three phases: 1. Atmospheric pressure tests with a fused silica combustion chamber; 2. Atmospheric pressure tests with counterflow-cooled steel flame tube and secondary air injection; 3. Validation of the burner in the mGT at elevated pressure levels. The current study will present the results of Phase 2.

The hydrogen burner used in the project is based on a swirl-stabilized burner of TUB and was scaled to 36 kW thermal power at atmospheric conditions. The burner design features a variable swirl intensity, additional axial momentum of air in the mixing tube, a movable central fuel lance and pilot nozzles at the front plate. Furthermore, the burners steel flame tube is exchangeable, which allows the evaluation of different dilution hole patterns and, thus, the variation of the ratio of primary and secondary air. The study presents temperature, pressure, and emission measurements. It is found that the flame can be operated over a large range of equivalence ratios and preheating temperatures up to 500 °C. As expected, the NOx emissions are mainly influenced by the local equivalence ratio, which can be controlled by the fuel mass flow or the dilution hole pattern in the flame tube. Furthermore, the results show a decrease of NOx when the power density is increased at constant equivalence ratios, and a rise of NOx during the fuel transition from natural gas to hydrogen. The results indicate certain differences to the findings of Phase 1.
Micro-Mixing Combustion: Experimental Assessment of the Impact of Fuel Preheating on Combustion Stability
Authors: Bellavance X. , Landry-Blais A. , Plante J.-S. , Picard M.
Published: August 2024

Micro-mixing combustion is a promising technology in the field of gas turbine combustion because of its safeness against autoignition and flashback while having NOx emissions near premixed levels. This technology is especially well suited for the combustion of hydrogen because of its high reactivity. Because of the potential safety and low NOx emissions of micro-mixing combustion, there is the desire to use this technology with a larger fuel spectrum. However, using micro-mixing technologies, stable combustion is limited to reactive fuels such as hydrogen or high hydrogen fuel blends. Our previous work demonstrated excellent combustion stability with high inlet temperatures up to 1000K with hydrogen, propane, natural gas or Jet fuel A1 as fuels. However, using propane as fuel, stable combustion was limited to inlet temperatures higher than 600K. In this paper, the impact of preheating the fuel prior to its injection on the combustion stability is assessed using propane as fuel because of its stability limitation. For micro-mixing injector configuration discussed in this publication, preheating fuel prior its injection allowed to decrease dynamic instability magnitude under 3 dB for most of the unstable data points (Sound pressure level variation at instability dominant frequency). Those stability gains were obtained while achieving similar levels of NOx emissions. Thermoacoustic instabilities were then linked to observed flame positions.
Validation of Transition Prediction of Baseline and High-Lift Airfoils in a Low Speed Cascade
Authors: Jennerjohn Christianer Mary K. , Nguyen Bao Q. , Rogers Daniel , Giebert Dietmar , Aksoy Hakan , Marks Christopher R. , Fletcher Nathan J. , Clark John P.
Published: August 2024

Due to the high cost of fuel, mitigation methods to reduce the engine weight while improving efficiency are necessary. One method for reducing engine weight includes a reduction in airfoil count. However, this approach can have the potential for added risk due to increased losses at off-design conditions. For the low-pressure turbine, the low Reynolds number off-design conditions become particularly of concern for increased loss generation. This current paper focuses on the validation of transition predictions for two low-pressure turbine airfoils using linear turbine cascade data. The baseline airfoil had a Zweifel loading coefficient of 1.1, and this airfoil was re-designed at a higher pitch spacing to increase the loading to 1.3. The experimental data includes pressure loadings at various Reynolds numbers ranging from 20K to 200K as well as loss measurements to quantify the Reynolds lapse rate at two levels of incoming turbulence. Additional tests for the high lift airfoil included simultaneously acquired suction surface hot film and midspan PIV data at two low Reynolds numbers and three different turbulence intensities. Comparisons between the Reynolds lapse rate of the baseline and increased lift airfoil show it is possible to increase the lift on the airfoil while only marginally increasing the loss for two turbulence conditions. Suction-side reattachment locations are indicated by three different methods: airfoil loading using Cp, suction surface hot film data, and midspan particle image velocimetry (PIV). These are in turn compared to results of flowfield simulations using a commercial solver where the Langtry-Menter Transition model was employed. Overall, the flowfield simulations for both airfoils compared favorably with experimental data for the Reynolds lapse rate as well as boundary layer separation and reattachment points on the suction surface at low Reynolds numbers.