High Load Operation Research Articles

Emission control in a dual fuel low temperature combustion engine at intermediate loads

Intermediate to high load operation in dual fuel reactivity controlled compression ignition (RCCI) techniques is restricted due to uncontrolled combustion that causes engine knocking. Dual fuel strategies with advanced pilot injection and near-top dead center (TDC) main injection timings are reported to enhance combustion control, albeit with increased soot emissions, reduction of thermal efficiency, and emergence of an intricate trade-off between total hydrocarbon (THC) and oxides of nitrogen (NOx) emissions. In order to address these conflicting issues, an intermediate engine load, corresponding to 6 bar gross indicated mean effective pressure at 1500 and 2200 rev/min engine speeds was investigated in this work. The main objectives of this work are (1) to obtain combination of control parameters to achieve near-zero engine-out NOx and soot emissions and high thermal efficiency while minimizing THC and CO emissions; (2) to understand the effectiveness of diesel oxidation catalysts (DOCs) for the oxidation and reduction of exhaust gas species in the dual fuel mode; and (3) to understand the oxidation characteristics of the soot generated from the dual fuel mode. Optimum dual fuel low temperature combustion strategies, in terms of diesel injection timings, quantity and exhaust gas recirculation levels, were identified using the statistical multi response signal to noise (MRSN) ratio method in which NOx, soot and indicated efficiency were response variables. The performance of commercial DOCs, with different precious metal (Pt and/or Pd) loadings, were also studied at optimum dual fuel strategies for gasoline-diesel dual fuel operations. High DOC outlet temperatures (>∼340°C), due to the exotherm generated by the oxidation of high concentrations of THC and carbon monoxide (CO) emissions from dual fuel operations, resulted in greater than 90% THC conversion efficiency. The exotherm decreased the nitric oxide (NO) oxidation whereas the nitrogen dioxide (NO2) reduction reactions were favored over the DOC in the dual fuel mode at the intermediate load operating condition. Thermogravimetric analysis of the soot showed higher activation energy (177.2 kJ/mol), formed at the dual fuel optimum condition, relative to the activation energy (162.7 kJ/mol) of the soot formed in conventional diesel combustion (CDC).

Characteristics of Combustion and NOx Emission in a 600 MWe Wall-Fired Boiler Under Varying Coal Mill and Burner Damper Configurations

ABSTRACT To accelerate China’s transition toward providing capacity support and prioritizing electricity generation, detailed research is necessary regarding the continuous peak output of coal-fired boilers during peak periods. However, high-load operation of coal-fired boilers may lead to issues such as NOx emission and increased flue gas temperature. This study conducted industrial experiments on a 600 MWe wall-fired boiler operating under peak conditions (500 MWe), using different pulverized coal mill operating modes. The boiler was optimized by adjusting the damper openings of the burners. Experimental results showed coal powder ignited within 0.2 m of burner outlets, indicating good performance. With the reduction in the damper openings of the burners, the concentration of NOx decreased, and the flue gas temperature gradually dropped, with the maximum temperature differential being 179°C. The ABCEF pulverized coal mill case had high water consumption and flue gas loss, unfavorably affecting economic operation. The ABDEF case delayed temperatures by 100°C, with the lowest NOx concentration at 277 ppm, enhancing environmental friendliness. In addition, the ABCDE case exhibited optimal coal burnout, with 0.838% fly ash carbon content, and the lowest flue gas temperature at 111.49°C, reducing flue gas loss by 5.9% compared to the ABDEF case, showing good economic performance.

Investigation of high percentage of dimethyl ether on biodiesel usage in a diesel engine

Demand for cleaner energy sources both as additive and alternative fuels that can substitute or contribute to the usage of conventional fuels is growing. Researchers have mainly focused on improving or finding a renewable fuel from vegetable oil or addition of chemicals and alcohols for IC engine. This study analyzed the effects of a high percentage of dimethyl ether (DME) combined with biodiesel in a diesel engine. Transesterification method was selected for conversion of pure safflower oil to biodiesel. DME was blended with biodiesel at concentrations of 50% and 25% on a volume basis, respectively. Engine performance and emissions tests demonstrated that the thermal efficiency values were increased at high load operation when the engine was fueled with high percentage of DME. Furthermore, compared to conventional diesel, there has been a notable decrease in NOx emissions. Nevertheless, the introduction of DME blend had negligible effects on CO2 emissions. However, when using a high ratio of DME blend, HC emissions were found to increase, whereas a low ratio of DME blend resulted in decreased HC emissions. Apart from these, some irregularities were observed both on heat release rate and cylinder pressure especially for 50% of DME usage. Finally, the values for both brake-specific fuel consumption and mass fuel of DME-blended fuels were deteriorated.

A denoising algorithm based on ARIMA and competitive K-SVD for the diagnosis of rolling bearing faults

Rolling bearings are extensively employed in industrial production as essential support components for rotating machinery. However, under conditions of high load and harsh operation, bearings are highly susceptible to failure. The weak vibration signals associated with these failures may be obscured by complex harmonic interference and strong noise, posing challenges for the accurate diagnosis of rolling bearing failures. In this paper, an autoregressive integrated moving average and competitive K-singular value decomposition (ARIMA-CK-SVD) algorithm is proposed to realize effective extraction of faulty pulse signals in a strong interference environment. First, the ARIMA model is used to preprocess the original signal to eliminate the interference of harmonic components. Second, a method is proposed for the adaptive selection of parameters in the ARIMA model, with consideration given to the characteristics of K-SVD. Subsequently, a competitive mechanism is introduced during the dictionary update phase of the algorithm to adjust the pattern of atomic updates and eliminate noise atoms. Finally, the effectiveness of the ARIMA-CK-SVD has been validated through simulation experiments and engineering tests.

Novel load allocation analysis for energy management and carbon emissions reduction of chiller system in hotel buildings

The operation of chiller systems for cooling energy generation in hotel buildings consumes the highest proportion of electricity. This study aims to introduce load allocation analysis to assess the potential for energy savings by a chiller system. The cooling load profile of a hotel in a subtropical climate is simulated using EnergyPlus. Eleven design options for the system include 4 to 8 chillers of the same or different capacities. Restoring chiller sequencing with high load operation can reduce the system's energy use intensity (EUI) by 12.7 %. An optimal design of four large and two small chillers with proper sequencing can reduce the EUI by up to 26.82 % or carbon emissions by 551,516 kgCO2-e. Increasing capacity steps above ten brings no significant energy savings and imposes complicated chiller staging. The area of the load allocation region can be evaluated simply from the chiller system design and used to analyze the system's energy performance. The EUI can be reduced by 0.3261 % for a 1 % drop in the area of load allocation region. The novelty of this study lies in using the load allocation region to assess energy savings of a chiller system without referring to sophisticated operating data at short timesteps. The significance of this study is to highlight the limitations of energy savings from the optimum chiller system design and address the need for incorporating more low energy technologies to enhance decarbonization.

Simulations of design and high load operation of a model Francis turbine using bridged approach to turbulence modelling

Abstract Off-design operation of hydraulic turbines is contemporarily frequented for balance of variable energy intermittence in the electric grid. Being operationally highly flexible, these turbines allow a quick transition to off-design operation from the design point. However, such operational flexibility, and therefore the grid balancing capability is impeded by generation of flow instabilities like vortex breakdown during off-design operation. Vortex breakdown causes losses in efficiency and pressure recovery, pressure fluctuations and possibly mechanical vibrations in event of resonance between system natural and flow field fluctuation frequencies. While substantial experimental and numerical effort has already been made to study draft tube vortex breakdown, an accurate numerical flow characterization of the phenomenon is still a challenge. To this end, operation of a high head model Francis turbine under design and high load regimes using a bridged turbulence modelling approach is simulated. The approach allows a seamless transition between direct numerical simulation and Reynolds averaged Navier-Stokes equations. The highest attainable accuracy is limited by the mesh size. As such a satisfactory compromise between desired accuracy and invested computational effort is attained. The flow in the draft tube is free of anomalies under design specified operation. However, at high load an axial flow stagnation occurs centrally, and the flow is separated about the stagnated zone. The core of the vortex is enlarged with flow recirculation within it. Shear layers between the central stagnant zone and surrounding outflow kink and roll up transforming it into a spiral structure. In this work, a basic yet accurate numerical flow characterization of the aforementioned flow situations is achieved.

Experimental investigation for enhancing the performance of hydrogen direct injection compared to gasoline in spark ignition engine through valve timings and overlap optimization

Recent advances in hydrogen internal combustion technologies highlight its potential for high efficiency and zero carbon emissions, offering a promising alternative to fossil fuels. This paper investigates the effects of valve timings and overlaps on engine performance, combustion characteristics, and emissions in a boosted direct-injection single-cylinder spark ignition engine using both gasoline and hydrogen. Optimized direct hydrogen injection effectively eliminates backfires and hydrogen slip during positive cam overlaps, significantly reducing the pumping mean effective pressure. The study’s primary finding demonstrates the potential of hydrogen to operate as a direct substitute for a gasoline engine without necessitating changes to the cam profiles at the high load operation. Furthermore, the study demonstrates that hydrogen leads to much higher thermal efficiencies across a wider range of engine loads when operated at a lean, air-to-fuel ratio of 2.75. The engine operating with such a lean-burn hydrogen mixture keeps the engine-out NOx emission at ultra-low levels. Compared to gasoline, hydrogen exhibits greater stability and a reduced reliance on camshaft timing during engine operation.

Impact of RON on a heavily downsized boosted SI engine using 2nd generation biofuel – A comprehensive experimental analysis

Sustainable energy solutions are paramount in the urgent global drive against climate change, especially in transportation. This research focuses on second-generation biogasolines and their potential in the context of decarbonisation. Two biogasolines, 99 RON E20 and 95 RON E20, were rigorously tested in a downsized single-cylinder engine. Their performance, combustion, and emissions were compared against the conventional fossil fuel, 95 RON E10, under varying engine loads. Additionally, a comprehensive injection parameter sweep was conducted for both biofuels at low and high loads, shedding light on their unique operational characteristics and operational regimes. This research significantly enhances our knowledge about the potential of these new biofuels and their implications for a more sustainable energy future. The findings of the experiments demonstrate no substantial difference between the tested biofuels and fossil fuels. Biofuel with a higher octane number provides more knock resistance than fossil fuel, resulting in increased thermal efficiency due to spark advance ability. However, more significant hydrocarbon emissions were detected for biofuels than fossil fuels due to more extensive aromatic content. Both biofuels have stable combustion in low and high-load operations under varying injection pressures and injection start times. 99 Bio E20 has a wider operational range than 95 Bio E20. However, due to very high HC emissions, especially at high-load operations, an early injection start with more significant injection pressure is not recommended for biofuel. From a broader perspective, both biofuels exhibit the promising potential to serve as drop-in replacements in spark ignition engines.

Comparative Analysis for Titanium alloy and Silicon Nitride (Si3N4) of Thermal Analysis for Deep Groove Ball Bearing

In this paper, the analysis of the directional heat flux and total heat flux for the bearing balls of Titanium alloy and Silicon Nitride has been demonstrated across a temperature range between 150 to 250 degree celcius. The obtained data allowed comparing the values of total heat flux and various directional heat flux. By comparing directional and total flux of heat in materials it enables the choice of the best-suited material creating bearings with regard to the performance needed. The use of the findings of the current comparison is to ensure efficiency and durability in particular operations. The data presented in the paper helped to analyze the patterns of heat distribution and see the differences between the materials and results a better material for ball bearing. Titanium alloy has excellent mechanical properties like mechanical strength and corrosion resistance. Silicon Nitride is characterized by thermal stability and high thermal resistance and also has excellent wear properties. Thus, using the results of the analysis allows choosing the material for bearing production for high-velocity and high-load operation based on a profound comparison to select the right material. The choice of right material will allow for a more efficient and durable bearing in an industrial setting.

AI-Enhanced design of excavator engine room cooling system using computational fluid dynamics and artificial neural networks

Excavators mainly perform high-load operations in fixed positions, so the stability of their performance depends solely on their cooling system. In this study, computational fluid dynamics (CFD) analysis was conducted using Fluent 2022 R22 software to analyze the cooling system in the engine room of an excavator. A comprehensive parametric study was performed, considering different cooling fan layouts and operating rates, to establish a database of cooling performance data for the excavator. Artificial neural network (ANN) models were trained on the constructed database and were then applied to design the cooling system and predict the performance. Further, optimal designs that maximized the cooling performance and energy efficiency were selected. This study demonstrates the feasibility of using ANN models to quickly and accurately predict and design the cooling system of an excavator in a cost-effective manner.

Optimization of Realistic Accelerated Stress Tests for PEM Fuel Cells Using Standardized Automotive Driving Cycles

Proton exchange membrane (PEM) fuel cells have so far not achieved the targeted lifetime necessary to be an economical alternative for automotive applications. This is mainly caused by their high degradation rates. To better understand the degradation mechanisms, the use of accelerated stress tests (ASTs) at the component level is widespread. However, it is still a challenge to transfer their results to real-world applications.To address this problem, the approach of this work is to derive load profiles from standardized driving cycles for passenger cars. In combination with a fuel cell system model that is used to define the operating conditions of the media, such as temperature or pressure, a test procedure is obtained that results in a realistic degradation of the fuel cell. The proposed test procedure exposes the PEM fuel cell (PEMFC) to the most important degradation conditions in mobile applications. Dynamic operation is responsible for deterioration processes within the PEMFC and is the underlying cause of typical hygrothermal and voltage cycling events. Such cycling also occurs during start-stop operations, causing severe damage to the PEMFC catalysts. In addition, idling conditions may prompt open-circuit voltage (OCV) conditions in the PEMFC, resulting in dissolution of the Pt catalyst and subsequent chemical degradation of the PEM. Additionally, high load operation may also lead to catalyst degradation. Finally, the inertia of the auxiliary components, such as the humidifier, during load changes causes not ideal conditions, such as relative humidity changes, resulting in further mechanical stress on the membrane.Due to the targeted PEMFC lifetime of up to 8,000 hours for automotive applications [1], realistic degradation test procedures have a very long test duration, making them particularly challenging and costly to conduct. To overcome this hurdle, the load profile of the proposed test procedure is shortened by using an in-house developed optimization algorithm. For this purpose, four operation modes are defined as degradation-accelerating: voltage cycling, relative humidity (RH) cycling, OCV/idling, and high load operation. Based on state-of-the-art AST procedures, a sub-algorithm is developed for each operating mode. Such sub-algorithms are capable of identifying all occurrences within a given test procedure that may lead to accelerated fuel cell degradation. For each sub-algorithm, the degradation parameters (namely upper and lower potential limits for voltage cycling, membrane tensile stress for RH cycling, fluoride emission rate for OCV/idling, and voltage degradation rate for high load) are specified by the user. This allows the comparison of different fuel cells in terms of their resistance to conventional degradation mechanisms.The developed algorithm can be used to optimize various driving cycles such as the worldwide harmonized light vehicles test cycle (WLTC) for various mobile applications. All cycle events identified as accelerating degradation are connected with a point connector function based on the fuel cell polarization curve. This ensures moderate voltage steps between the identified phases and thus prevents the algorithm from inducing further degradation of the fuel cell.The optimization algorithm obtained can reduce the test duration by up to 40%. The method can be repeated frequently during AST operation by repeatedly measuring the polarization curve to consider the continuous degradation in the test procedure. Decreasing fuel cell performance leads to more severe voltage drops during load changes and thus an increase of degradation-accelerating phases over the test period. Furthermore, start-stop ASTs developed by Bisello et al. [2] are also included due to their strong contribution to fuel cell degradation in automotive applications.Finally, the optimized cycles are analyzed using two simulation tools to evaluate the degradation. The first tool by Ao et al. [3] uses the electrochemical surface area (ECSA) to quantify the proceeding degradation during cycle operation. A characteristic voltage and the voltage change rate are extracted from the driving cycle. For both values, the resulting decrease in ECSA is modeled and aging is defined as the ECSA loss rate. The second tool by Pei et al. [4] examines the driving cycle according to the four degradation-inducing conditions and combines them with experimentally determined degradation rates. Both tools allow an analysis of the degradation derivative between the initial and optimized test procedures. By adjusting the degradation rate for the different degradation mechanisms, the AST procedure is improved in terms of its representativeness for real-world applications.

The Formation Mechanism of Ordered Mesoporous Carbon with Network-Structure: A Novel Support Material for Pt-Based Catalysts in PEFC Cathodes

INTRODUCTIONTo achieve carbon neutrality in the upcoming sustainable society, it is crucial to utilize hydrogen as a fuel in the transportation sector. Fuel cell vehicles are expected to play an important role in the future hydrogen society, but there are still challenges to be overcome before their widespread adoption. For example, Pt/C-based catalysts used in PEFC cathodes have an issue with poisoning of the Pt due to direct contact with the ionomer, especially during low-load operation. Recently, a new approach using accessible-pore carbons has been proposed, where Pt is placed at an appropriate position within the nanopores of a carbon support to suppress ionomer poisoning of Pt [1]. In order to realize this concept, it is essential to design a mesoporous carbon support that possesses nanopores with appropriate size and proper ordering. We have developed an ordered mesoporous carbon with a hierarchical network structure (Net-OMC) consisting of small OMC particles of several tens of nm in size, which are connected to form a network structure with well-developed primary pores. The Net-OMC exhibited highly ordered nanopores on the surface of the OMC primary particles, with a pore size ca. 5 nm and an interpore distance of ca. 8 nm. Pt nanoparticles were loaded selectively within the Net-OMC nanopores by the selective Pt-deposition technique developed by our research group. Pt/Net-OMC catalyst exhibited higher mass activity and durability for the ORR in comparison with those for a commercial Pt/CB catalyst [2]. In this study, the formation mechanism of Net-OMC and the relationship between the catalytic properties of Pt/Net-OMC and its pore structure was investigated in detail.EXPERIMENTALNet-OMC powder was synthesized with resol-nonionic surfactant micelles as a carbon source and structure-directing agent. Resol-F127 (nonionic surfactant) micelles were synthesized by mixing phenol, formaldehyde, water and F127 with sodium hydroxide. After hydrothermal treatment of the mixture, the resulting solid was filtered and washed thoroughly and dried under vacuum. The obtained powder was carbonized at 700 ºC followed by annealing at 1000 ºC. Pt was deposited on the Net-OMC powder by selective deposition techniques. Cyclic voltammetry and linear sweep voltammetry were carried out in N2-saturated and O2-saturated 0.1 M HClO4 solution at 25 ºC using the conventional rotating disk electrode (RDE) technique. Potential step cycling measurements simulating load cycling between 0.6 V and 1.0 V vs. RHE were carried out according to the FCCJ protocol. Coating of the catalyst on a glassy carbon disk substrate was carried out by an electrospray (ES) coating technique developed by our group [3]. N2 adsorption measurements at liquid nitrogen temperature were carried out. The morphology of the Pt/ns-OMC was observed by scanning transmission electron microscopy (STEM).RESULTS AND DISCUSSIONSTEM images for the ordered mesoporous carbon particles with network structure (Net-OMC) with varying concentration during hydrothermal synthesis are shown in Figure 1. In Fig. 1(a), the network structure formed by connection of OMC primary nanoparticles with developed macropores is clearly observed. The OMC nanoparticles were tightly connected via a thick necking structure. From the high magnification image (Fig. 1(a), inset), highly ordered nanopores were observed on the surface of the OMC particles. The OMC primary particle size and the connecting neck diameter changed with the resol micelle concentration during the hydrothermal treatment. When the concentration of the micelle solution was decreased, both the primary particle size and necking length decreased. At a concentration of 1.8 mmol l-1, the formation of monodisperse particles with roughly the same size from the resol-F127 micelle particles was observed, as estimated by dynamic light scattering analysis. Thus, it is believed that the Net-OMC structure is formed through the self-assembly of micelle particles during the hydrothermal synthesis. The controllable network structure of Net-OMC is expected to provide a favorable porous structure of the catalyst layer for the MEA measurement even during high-load operation.

Modelling Analysis of MEA Dynamic Operation Under Real-World Automotive Driving Cycle

In last years, Proton Exchange Membrane Fuel Cells (PEMFC) have received an increasing interest as a candidate for light and heavy-duty vehicle application1. To guarantee an efficient and durable operation of PEMFC, the understanding of local conditions, experienced by MEA, during dynamic operation is highly important. Effective numerical modelling can help to gain insights on the local heterogeneity linked to water and thermal management of the cell.A 1 + 1D multiphase dynamic non isothermal PEMFC model, implemented into MATLAB Simulink environment, was used to investigate experimental data obtained on a segmented cell hardware 2. Particular attention was paid to properly model the mass transport and kinetic related phenomena in catalyst layer(CL), as the local oxygen transport resistance through the ionomer thin film3 and the platinum oxide formation/reduction reaction, and their mutual interaction. Exploiting experimental data, obtained from tests on the segmented cell hardware, it was possible to give a robust validation to the 1+1D model, both at global and local level, thanks to the spatially-resolved information available. By simulating real-world driving cycle (DLC) protocol, developed within the ID-FAST project4, drying-up periods of ionomer contained in catalyst layers and in membrane, as well as flooding periods of porous layers and channels, were identified and analyzed during low-load and high-load operation.The performance model was coupled with a catalyst durability model, such to investigate the effect of ageing on dynamic performance of PEMFC. An innovative semi-empirical electrochemical surface area (ECSA) loss model was developed, based on the platinum dissolution mechanism, and validated initially on accelerated stress tests on different operating conditions5. The simulated load profile and local operating conditions in CLs were processed by a proper algorithm, to convert a driving cycle into a combination of elementary steps and to associate a loss factor for the ECSA to each of the identified elements, thus to estimate the retained local and global ECSA. Exploiting experimental database made up of 1000 operating hours performing ID-FAST DLC, the effect of local operating conditions on PEMFC degradation and performance was furtherly comprehended, focusing mainly on the effect of reactant humidification. The developed model framework succeeded in estimating performance loss during driving cycle operation, as visible in Figure 1(a-b). Simulated and experimental ECSA decay over time is shown in Figure 1(c), demonstrating good model prediction capability. The obtained results showed the potentiality of the model to capture complex two-phase and non-isothermal transport phenomena both in the along channel and through-MEA direction, consistently with a large set of experimental data.Experimental data on single cell were collected under ID-FAST project (Grant Agreement No 779565, Joint Undertaking, EU Horizon 2020).References D. A. Cullen et al., Nat. Energy, 6, 462–474 (2021) https://www.nature.com/articles/s41560-021-00775-z.E. Colombo, A. Baricci, A. Bisello, L. Guetaz, and A. Casalegno, J. Power Sources, 553, 232246 (2023) https://doi.org/10.1016/j.jpowsour.2022.232246.T. Suzuki, H. Yamada, K. Tsusaka, and Y. Morimoto, J. Electrochem. Soc., 165, F166–F172 (2018) https://iopscience.iop.org/article/10.1149/2.0471803jes.F. Wilhelm et al., ID-FAST -D4.3 – Analysis of coupling between mechanisms and definition of combined ASTs, p. 49, (2021) https://www.id-fast.eu/uploads/media/ID-FAST_D4-3_Analysis_of_coupling_between_mechanisms_and_definition_of_combined_ASTs_OK.pdf.A. Kneer and N. Wagner, J. Electrochem. Soc., 166, F120–F127 (2019) https://iopscience.iop.org/article/10.1149/2.0641902jes. Figure 1

Impact of Position and Platinum Loading of Recombination Interlayers in Proton Exchange Membranes on the Anodic Hydrogen Content in Water Electrolysis

Hydrogen crossover through the membrane is a significant safety concern in proton exchange membrane water electrolyzers (PEMWEs). This issue is predominant at low loads, which contradicts the application of PEMWEs in conjunction with fluctuating renewable energy sources that require the electrolyzer to switch between low- and high-load operation. The risk of flammable or explosive oxygen-hydrogen mixtures on the anode side of the electrolyzer prevents the application of membranes as thin as in fuel cells, which results in relatively large Ohmic losses. A means to mitigate the accumulation of hydrogen in the oxygen compartment is the integration of platinum nanoparticles as a recombination catalyst interlayer within the membrane that catalyzes the recombination of hydrogen and oxygen to water. It was shown that such an interlayer effectively minimizes the hydrogen concentration on the anode side without reducing the cell performance.1 Thus, this technology can pave the way toward thinner membranes and more efficient electrolyzers.However, the interlayer should not increase the costs of the membrane electrode assembly by excessive Pt loading. Hence, we investigated the ideal position of this recombination interlayer within the membrane,2 and we performed a parameter study on the minimum required catalyst loading for an effective hydrogen-in-oxygen reduction.3 We find that the best position for the interlayer is close to the anode due to the lower oxygen permeability of the membrane. Also, a loading of 10 µg per cm² of platinum nanoparticles is sufficient to reduce the anodic hydrogen content from more than 2.5 vol.% (without interlayer) to approx. 0.5 vol.% when operating a PEMWE cell with a 110 µm thick membrane at 0.5 A/cm² and a differential pressure of 10 barc/1 bara. In summary, we are able to show that low platinum loadings within the membrane are sufficient to reduce the anodic hydrogen content in PEMWEs to safe values without impairing the electrochemical performance of the cell.References C. Klose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach and S. Thiele, J. Electrochem. Soc., 165(16), F1271-F1277 (2018).A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele and R. Hanke-Rauschenbach, J. Electrochem. Soc., 168(9), 94509 (2021).D. Abbas, A. Martin, P. Trinke, M. Bierling, B. Bensmann, S. Thiele, R. Hanke-Rauschenbach and T. Böhm, J. Electrochem. Soc., 169(12), 124514 (2022).

Durable Testing and Analysis of a Cleaning Sieve Based on Vibration and Strain Signals

Cleaning is one of the most important steps in the harvesting process, and the prolonged and high-load operation of the vibrating sieve can decrease its reliability. To uncover the structural flaws of the cleaning sieve in the crawler combine harvester and establish a foundation for quality inspection, this paper proposes a method for durability testing and analysis using vibration and strain signals. Via the modal analysis of the cleaning sieve, the most susceptible areas for fault signals are identified. Subsequently, a specialized test rig exclusively designed for the examination of the durability of the cleaning sieve is constructed. After following 96 h of uninterrupted operation, the vibration plate of the cleaning sieve sustains damage, resulting in atypical noise. A signal analysis reveals that the primary vibration signal of the cleaning sieve primarily consists of a fundamental frequency of 5 Hz, corresponding to the driving speed, as well as a frequency doubling signal of 50 Hz. After the occurrence of damage, the peak amplitude of the received vibration signal increases by over 86.3%. Furthermore, the strain gauge sensor situated on the support plate of the rear sieve detects anomalous signals with frequencies exceeding 300 Hz, which are accompanied by a considerable rise in the power spectral density. This research has significant importance for enhancing the service life of the cleaning sieve and optimizing the overall machine efficiency.

Characteristics of heat, power generation, and energy efficiency study on a novel air-cooled PEMFC stack based on micro heat pipe arrays

This study introduces a novel kilowatt-scale air-cooled proton exchange membrane fuel cell stack utilizing micro heat pipe arrays (MHPA-PEMFC stack). This innovative stack design addresses issues commonly associated with conventional air-cooled fuel cell stacks, such as low heat transfer efficiency, suboptimal performance, and safety concerns, especially during high-load operations. In addition to the output performance of the stack, this study investigates the heat and power generation performance limits, operational security, and energy utilization efficiency of the MHPA-PEMFC stack under high power output and varying flow rates. The study introduces two novel evaluation indexes, namely, relative load gain (RLG) and relative safety gain (RSG), to provide a comprehensive evaluation. These indexes are utilized to link energy efficiency and exergy efficiency to the performance of the MHPA-PEMFC stack. The results show that the MHPA-PEMFC stack exhibits superior heat dissipation performance, uniform temperature distribution, and enhanced load capacity and safety compared with conventional PEMFC stacks. The maximum RLG and RSG achieved by the MHPA-PEMFC stack are 100% and 7.53, respectively. The energy efficiency of the MHPA-PEMFC stack surpasses 29% while maintaining a guaranteed maximum RLG. Notably, a higher RSG leads to a sacrifice in both energy and exergy efficiency.

Measurement of Temperature and Load Versus Bearing Displacement in a Thrust Foil Bearing: Differences Between Light Load and High Load Operation

Abstract This paper presents a test rig for evaluation of gas thrust foil bearings (GTFBs) and details measurements of load capacity conducted with a commercial GTFB comprising a single 360 deg, 0.127 mm thick top foil divided into six continuous arc segments with a formed taper of 0.102 mm. Coated with Teflon®, the top foil rests on a stack of shims above six underspring structures, each comprising three strips of bump foils, 0.102 mm thick. Measurements include the applied static load and break-away torque, rotor speed, bearing axial displacements at three locations 120 deg apart, the flow of a cooling stream, and temperatures in and out of the bearing. Static load tests produce the underspring deformation and a dry-sliding friction coefficient f ∼ 0.12. The underspring is rather flexible though quickly hardening for specific load (P*) > 25 kN/m2 to reach an ultimate deformation of ∼0.320 mm. Measurements at 30 krpm (OD surface speed = 111 m/s) and increasing static loads produce bearing displacements that parallel the displacements without shaft rotation. Most importantly, the difference between displacements approaches ∼0.060 mm for P* > 45 kN/m2. The test bearing operated safely to P* = 90 kN/m2 and failed at P* = 120 kN/m2. When heavily loaded, the GTFB is significantly stiffer than when lightly loaded. Designed for easiness of installation and operation, the test bearing demonstrated a stable and repeatable performance with likely a uniform gap or film thickness even for the largest loads applied.

Determination of the optimum biogas energy ratio in dual-fuel biodiesel used in cooking oil-biogas operation

ABSTRACT This study aims to examine the effects of biogas input ratio on the engine performance, combustion characteristics, and emissions of dual-fuel mode diesel engines fueled by waste cooking oil biodiesel combined with biogas. The engine test was carried out in dual-fuel mode biodiesel-biogas operation with variations in the methane content of the biogas and biogas energy ratio in excess of 90%. The methane gas content was varied from 40%, 60%, 80%, and 100% with different applied loads. A constant engine speed of 2400 rpm is used for all tests. It has been shown that increasing the methane content of the biogas can improve the brake thermal efficiency, particularly at high loads. A maximum brake thermal efficiency of 29.3% can be achieved on dual fuel with 100% methane gas content. This value has increased by 7.51% compared to biodiesel fuel under the same load conditions. Biogas with 100% methane gas also reaches cylinder pressures of 8.07 MPa and rate of heat release of 35.8 J/deg-1 at high load operation. This study confirmed that the use of biogas with more than 90% biogas energy ratio can be operated in a dual fuel mode. At low and medium loads, nitrous oxide emissions are drastically reduced at biogas energy ratios of up to 90%, 82.8%, and 65.1%, respectively. The study also identified the optimum biogas energy ratio operating range of 60–90% for maximum thermal efficiency and low emissions.

Energy optimization of main hydraulic system in a forging press by simulation and experimental methods

The primary cause of the low energy efficiency of hydraulic presses (HPs) is the mismatch between installed power and demanded power. This study adopts the concept of a high-pressure waterjet cutting system and presents an energy-saving method to reduce the energy dissipation of HPs, where a single drive system composed of multi motor-pumps and superchargers-accumulators, is integrated into an HP and partitioned into several drive zones corresponding to load profiles. Meanwhile, a method for scheduling the above system is presented to realize an orderly energy supply with no conflict and shorten the idle time. Pump units, accumulators, and superchargers were selected according to the different load profiles to energize the actuators in various operation stages. Since the kinetic power of the hydraulic oil output from superchargers are significantly higher than those of a conventional power unit, a press with low installed power could achieve high power load operations. Finally, the proposed system was applied to a 31.5 MN forging HP as a case study. Results showed that the installed power and the energy dissipation were reduced by 56% and 52% in one working cycle, respectively. Moreover, the novel HP displayed a processing performance equivalent to that of the conventional setup.

Tribological Performance of Brass Journal Bearing Working Under Contaminated Conditions

Abstract: Bearings for sugar mills are known to withstand high load and low speed operations. A temperature rise was detected in the warehouse of a sugar factory, when working in the polluted or contaminated environment of the sugar industry. Therefore, an experiment was conducted on brass (CuZn) plain bearings when lubricated with water with different flow rates. In this study, the rise in temperature of a plain bearing in a sugar factory was analyzed. By simulating the operating conditions in a sugar mill the causes for rise in temperature in the bearing were identified and commissioning in a plain bearing test rig that takes into account the combination of operating conditions (self-load, speed, dirt, lubricants, etc). Insufficient supply of internal lubricant can lead to plain bearing failure. This affects the production costs of the industry and can also endanger human lives. The brass journal bearing gives the best performance under the Q3 flow of water and also have lesser rise in temperature.