Start-stop Operation Research Articles

Running-in effects on friction of journal bearings under slow sliding speeds

Hydrodynamic thrust and journal bearings are facing challenges in modern heavy-duty machinery where full film lubrication cannot always be achieved or sustained. This is due to reasons such as start–stop operation, increased power density and the use of thinner lubricants. Although this leads to increased overall efficiency, bearings are operating more often under mixed lubrication conditions. This is why the running-in behavior of the bearing material is important. In this study, running-in behavior of traditional leaded tin bronze and its environmentally sustainable alternative, bimetal bismuth, was studied. Experimental friction tests were performed with journal bearings under full film and mixed lubrication conditions in order to find the Stribeck curves. The results are analyzed using frictional energy, and friction coefficient values based on continuous friction monitoring. Remarkable reduction of friction was observed with both bearing materials due to running-in.

Analysis on End-face Temperature of High-speed Oil-Gas Two-Phase Backflow Pumping Seal

This paper aims to analyze the end-face temperature in the open state & unopened state, and to verify the feasibility of oil-gas two-phase backflow pumping seal (OG-BPS) in oil-gas two-phase lubrication conditions. The thermal boundary, shear heat, heat distribution, convection heat transfer coefficient and other relevant conditions are applied to the theoretical models establishing. The effect of the seal operation parameters such as the speed, pressure difference and liquid-gas ratio on the end-face temperature is analyzed by calculating the thermo-structural coupling models and conducting experiments. The results show that the end-face temperature in the unopened state is much higher than that in the open state, which can be regarded as a criterion for whether the seal works normally. In the open state, the end-face temperature increases slightly with the increase of the rotation speed and liquid-gas ratio. In the unopened state, the end-face temperature increases sharply with the increase of the rotation speed and the pressure difference. However, with the increases of the liquid-gas ratio, the end-face temperature will decrease rapidly, so the oil-gas two-phase medium will be beneficial to start-stop operation. This paper verifies the feasibility of the OG-BPS, and provides a basis for further study of the effect of end temperature on seal performance.

Theoretical and experimental investigation of an absorption refrigeration and pre-desalination system for marine engine exhaust gas heat recovery

Absorption-refrigeration-cycle-based exhaust gas heat recovery technology is effective in improving the thermal efficiency and fuel economy of marine diesel engines. However, the absorption refrigeration system is inflexible in the start–stop operation, and this cannot fulfil the fluctuating demand of refrigeration. This paper presents both the theoretical and experimental investigations of an absorption refrigeration and freezing pre-desalination-based marine engine exhaust gas heat recovery system. The energy storage subcycle is introduced to overcome the energy underutilisation and balance the excessive refrigerating output of the absorption refrigeration cycle. Seawater is utilised as the phase-change material and it is pre-desalinated in the energy storage subcycle. A mathematical model of the system is established and experimental investigation is conducted. Furthermore, the theoretical and experimental performances are compared, and an economic analysis of seawater desalination is performed to evaluate its economy. The results show that the total refrigeration output of the system ranges from 6.1 kW to 9.9 kW, and the system COP (Coefficient of Performance) can reach 16% under the experimental operating conditions. Additionally, the salinity of pre-desalinated seawater can be reduced to below 10 ppt. Moreover, the cost of RO (Reverse Osmosis) seawater desalination can be reduced by 26% through the pre-desalination process of seawater.

Optimal gas turbine inlet temperature for cyclic operation

Historically, the development of gas turbine technologies is intrinsically linked with the increase in the initial temperature of the working fluid, which provides an increase in the thermal efficiency and thermodynamic efficiency of the gas turbine cycle. The increase in the gas turbine initial temperature leads to the unit costs reduction and the unit capacity is increased. However, higher turbine inlet parameters increase significantly thermal stresses in the metal, especially during a start-stop operation. In this study we compared the efficiency of three gas turbines with different values of the turbine inlet temperature during covering different parts of the daily electric load curve. The sum of fuel and depreciation costs is chosen as an optimization criterion. Service life parameters were determined for the most thermal stressed gas turbine element, namely the first stage gas turbine blades. To implement the low-cycle fatigue analysis, the numerical simulations were implemented using ANSYS®. The modelling was divided in two stages. Firstly, the fluid dynamics behaviour was analysed around the blade cascade with the aim to determine the thermal state during the whole startstop cycle. In the second stage of calculation, the mechanical loads were added caused by centrifugal force and the fluid flow forces from the working fluid side. To determine depreciation costs, the modified equivalent operating hours principle was used. Obtained results showed that for cyclic operation mode with a high number of start-ups and shutdowns, the costs associated with service life reduction exceed markedly the fuel economy, making turbines with lower turbine inlet temperature more profitable.

Challenges of friction reduction of engine plain bearings – Tackling the problem with novel bearing materials

Abstract This study specifically focuses on the friction properties of bearing materials. By means of laboratory test rigs using ring on disc and bearing segment systems extensive investigations under mixed friction conditions and start stop operation were carried out in this area. One the one hand, commonly used bearing products including bimetal and trimetal bearings with various coatings are studied resulting in elucidation of the underlying mechanisms of the friction performance. On the other hand, based on the conclusions thereof, novel bearing coatings are introduced and are verified regarding friction performance. The results emphasize the changing behaviour of the friction characteristics of bearing materials. Furthermore, the outstanding mixed friction capabilities of the herein proposed novel bearing coatings are documented.

Research on the energy control of a dual-motor hybrid vehicle during engine start-stop process

In this paper, motor torque control methods are proposed to suppress the vibration of a dual-motor hybrid powertrain during start-stop operation. Firstly, a co-simulation ADAMS and MATLAB/SIMULINK model is built to study the dynamic characteristics of the hybrid vehicle during modes switching process. Secondly, a torque compensation control method of electric motors is established to compensate the vibration energy source. Thirdly, a vibration transfer path control is built to change the dynamic properties during the engine start-stop process. The results show that the proposed methods can reduce the longitudinal acceleration amplitude of the vehicle to less than 0.4 m/s2, which is only about 30% of the uncontrolled system, during the engine start process. While in the engine stop process, the longitudinal acceleration amplitude of the vehicle is reduced to less than 0.3 m/s2, and the vibration amplitude is only about 20% of the unchanged system. The established methods are effective for suppressing the vehicle vibration and controlling the energy during the modes switching.

Degradation Mechanisms and Accelerated Stress-Test Protocols for Polymer Electrolyte Water Electrolyzers

If polymer electrolyte water electrolysis (PEWE) is to be deployed to serve as an energy storage technology in the grid, the potential challenges related to the component durability need to be understood and addressed. The US Department of Energy (DOE) targets a cost of 2 $/kg H2 for the year 2020. Maintaining stack efficiency is key to a competitive end-cost of H2, as the main contribution is projected to come from the cost of electricity (1). The development of tailored PEWE components therefore needs to go hand-in-hand with the development of accelerated stress-tests that trigger specific degradation mechanisms. In this study, different degradation mechanisms were induced by subjecting commercial catalyst-coated membranes (CCMs) to specific operating conditions. PEWE cells were operated for 300 h to estimate the effects of the imposed stressors, and the cell performance was compared to the 300 h non-stressed benchmarks. The cell response was analyzed using electrochemical impedance spectroscopy (EIS). Individual catalyst layer (CL) characteristics were probed in the H2/N2 regime, and the cyclic voltamograms were recorded. Finally, samples were post-test investigated using scanning electron microscopy (SEM). The effect of the cell compression on the CL performance was stessed using cell assemblies with Ti-sintered porous transport layers (PTLs) of different morphological surface properties. Rigid PTL-surface features have induced local variation in CL porosity, and increased CL proton transport resistance (RCLa H+). In the case of PTLs with large voids, CCM creep led to the formation of thin spots and an increase in measured H2 in the O2 outlet. We have found that the increased gas crossover with mechanically stressed and locally thinned CCM results in a higher fluoride release rate over 300 h. The effects of start-stop operation on the CL stability were quantified over 300 h by periodically analyzing the anodic water using ICP-mass spectroscopy for traces of precious metals. Additionally, elemental mapping was done on the post-test CCM cross-sections to deterime if potentially dissolved species had deposited in the PEM (2). As water impurities are an important factor determining the electrolyzer lifetime (3), we have designed Ir2+ doping experiments to simulate the accelerated reverisble contamination of the CCM. A detalied overpotential analysis was done to determine the effect on the ohmic, activation and mass-transport overpotential. A specially designed cell was used to conduct operando neutron imaging of the contaminated CCM, and track the distribution of metal cations in the CCM cross-section under various operating conditions. EIS was done in paralell to correlate the impact of contaminants on the cell performance with their cross-sectional position. We established an comprehensive degradation matrix based on the PEWE degradation-inducing experiments, highlighting the stressors, degradation mechanisms and the affected aspects of PEWE performance.

Highly-Durable Membrane Electrode Assembly for Direct Formate Solid Alkaline Fuel Cells

Solid alkaline fuel cells (SAFCs) have attracted much attention as next-generation energy conversion electrochemical devices. Despite numerous advantages of SAFCs including the usages of various type catalysts and liquid fuels with high energy density, the practical applications of these devices are limited because of the drastic decrease in the cell performance during the high temperature operation under alkaline condition. This low performance of the device is mainly attributed to the severe degradation of membrane-electrode assembly (MEA). Therefore, the development of a durable and stable MEA is critical to improve the cell performances and stabilities in this system. Here we report the development of highly-durable MEA using a new carbon-free cathode catalyst and an aromatic polyelectrolytes without an ether linkage. As shown in Fig. 1A-a, the carbon-free catalyst consists of a nanosized beaded network formed by the connection of Pt–Fe nanoparticles.[1–3] The beaded metal network is electrically conductive, enabling the removal of carbon supports from catalyst layer. Hence, carbon corrosion problems can be avoided, leading to high durability against the cyclic start-stop operation of the system. We successfully demonstrated the high durability of this carbon-free catalyst in alkaline electrolyte solution. In addition, the specific activity of a connected Pt–Fe catalyst for oxygen-reduction-reaction (ORR) is about five times higher than that of a commercial Pt-nanoparticle catalyst supported on carbon black. Fig. 1A-b represents the chemical structure of new spirobifluorene-based aromatic ionomer with no ether-linkage. This anion-conductive ionomer exhibited high alkaline and oxidative durability because the backbone did not contain ether linkages, heteroatoms, and benzylic C–H bonds. It was also demonstrated that the thin-layer coating (< 1 μm) of spirobifluorene-based ionomer on the anion-exchange membrane (Fig. 1A-c) improved alkaline and oxidative stability, and suppressed the permeability of potassium formate (HCOOK) as fuel. We fabricated the MEA using the in-house made durable catalyst and membrane material, i.e., the carbon-free connected Pt–Fe catalyst, spirobifluorene-based ionomer, and anion conductive pore-filling membrane with durable thin layer. The in-house made MEA, operated at a high temperature of 80 °C, exhibited high power density of 220 mW cm−2 and high open circuit voltage of about 1.0 V (Fig. 1B), here, a mixture of aqueous solutions of 4M HCOOK and 2 M KOH was used as the fuel. Further, more importantly, the high performance of the MEA retained even after the operation at 80 °C and 0.2 A cm−2 for 150 h. Therefore, for the first time, we demonstrated a highly durable and stable MEA in alkaline medium for the direct formate SAFCs. [1] T. Tamaki, H. Kuroki, S. Ogura, T. Fuchigami, Y. Kitamoto, and T. Yamaguchi, Energy Environ. Sci., 8, 3545–3549 (2015). [2] H. Kuroki, T. Tamaki, and T. Yamaguchi, J. Electrochem. Soc., 163(8), F927–F932 (2016). [3] H. Kuroki, T. Tamaki, M. Matsumoto, M. Arao, Y. Takahashi, H. Imai, Y. Kitamoto, and T. Yamaguchi, ACS Appl. Energy Mater., 1(2), 324–330 (2018). Figure 1

(Invited) Durability Evaluation of PEM Fuel Cells for Automotive Application

Proton exchange membrane fuel cells (PEMFC) technology is already in commercialization phase for automotive applications. However, the biggest challenges for its successful mass commercialization are cost and durability. Current PEMFC technology can meet the lifetime targets but the cost to achieve it can be very high due to material’s cost and system level mitigation complexities. Understanding of the membrane electrode assemblies (MEA) degradations using relevant durability accelerated tests at early stages of development is essential. PEMFCs for automotive applications goes through thousands of cycles during normal operation of the vehicle over the expected life span of 10 years. These cycles include a combination of load or voltage cycles, start and stop cycles, humidity cycles and temperature cycles. Study have shown that start-stop cycling accounts for 44% of operation mode while load cycling and idling for 28% each (1). Under these cycles, fuel cells suffer from severe degradations of its main components; cathode, anode, membrane and bipolar plates. The PEMFC cathode can degrade during start-stop operation via carbon corrosion (2). Cathode degradation can be mitigated by using stable materials or by applying system mitigations. System mitigation by a voltage limiting control (VLC) can be one of the effective measures (3). The VLC can, however, lead to voltage spikes (high positive potentials) at the anode during fuel cell start-up and shut-down. Moreover, during fuel (H2) starvation conditions, the potential at the anode can give rise to high positive potentials leading to anode catalyst layer degradation. During idling operation mode, PEMFC is at or near open circuit conditions which is known to accelerate proton exchange membrane (PEM) decomposition especially under low humidification (4). Peroxy-radicals originating from hydrogen peroxide produced at the anode catalyst surface cause the PEM degradation (5). Pt band formation in the membrane is also known to promote peroxide formation leading to membrane decomposition (6-7). Several accelerated protocols are currently being used to evaluate the durability of PEMFC. At Nissan, our durability protocols are focused on understanding the material degradation under relevant automotive cycles and correlating single cell durability to the stack level. Start-stop accelerated protocol to evaluate the cathode support durability consist of potential cycling from 1.0 V to 1.5 V using triangular waveform for 1000 cycles with diagnostics conducted intermittently after certain number of cycles. Cathode catalyst durability is evaluated using load cycling accelerated protocol wherein the potential is cycled between 0.6 V to 0.95 V to simulate peak load and OCV/idle using a square wave profile with 3 second hold at each potential. The upper potential is known to have significant impact on catalyst degradation (8). Load cycling is performed for 10,000 cycles with diagnostics conducted intermittently. Anode degradation under cell reversal condition is evaluated using a protocol designed to simulate high voltage spikes at the anode. Cell reversal cycling is performed by applying a load of 0.2 A/cm2 for 1 sec while flowing N2 at the anode and air at the cathode while measuring the cell voltage under the applied load for a total of 200 cycles. Membrane durability is evaluated using humidity cycling (mechanical durability) and potential hold at open circuit (chemical durability). Membrane’s chemical durability is evaluated at 90 °C and 30% RH under hydrogen and oxygen by operating MEA at open circuit. The target of OCV hold test is 500 hrs while maintaining potential above 0.8 V. Mechanical durability of membrane is evaluated by cycling RH to simulate dry condition (0%) and wet condition (100%) for target of 20,000 cycles. All these accelerated tests are performed at ambient pressure and summarized in the Table 1 below. Acknowledgments: The author would like to gratefully acknowledge Nissan Technical Center North America Fuel Cell Research team members (Dr. Amod Kumar, Dr. Ramesh Yadav and Dr. Cenk Gumeci) and Nissan Motor Co. Ltd Japan Fuel Cell research team members (Dr. Atsushi Ohma, Dr. Yoshihisa Furuya) for technical discussions and data.

In-plane and through-plane non-uniform carbon corrosion of polymer electrolyte fuel cell cathode catalyst layer during extended potential cycles

The impact of electrochemical carbon corrosion via potential cycling durability tests mimicking start-stop operation events on the microstructure of the cathode catalyst layer in polymer electrolyte fuel cells (PEFCs) is investigated using focused ion beam (FIB) fabrication without/with the pore-filling technique and subsequent scanning electron microscope (SEM) observations. FIB/SEM investigations without pore-filling reveals that the durability test induces non-uniform cathode shrinking across the in-plane direction; the thickness of the catalyst layer decreases more under the gas flow channel compared to the area under the rim of the flow field. Furthermore, FIB/SEM investigations with the pore-filling technique reveal that the durability test also induces non-uniform cathode shrinking in the through-plane direction; the pores in the area close to the membrane are more shrunken compared with those close to the microporous layer. In particular, a thin area (1–1.5 μm) close to the membrane is found to be severely damaged; it includes closed pores that hinder mass transport through the catalyst layer. It is suggested that uneven carbon corrosion and catalyst layer compaction are responsible for the performance loss during potential cycling operation of PEFCs.

(Invited) Pt/RuO2-TiO2 (RTO) As Cell Reversal Tolerant Anode Catalyst for PEFCs

The PEFC cathode can degrade during start-stop operation via carbon corrosion (1). To prevent cathode degradation, a voltage limiting control (VLC) protocol can be one of the effective measures to protect the cathode during cell start-up and shut-down (2). The VLC can, however, lead to voltage spikes (high positive potentials) at the anode during fuel cell start-up and shut-down. Moreover, during fuel (H2) starvation conditions, the potential at the anode can give rise to high positive potentials leading to carbon corrosion and, subsequently, anode catalyst layer degradation. To avoid degradation of the anode catalyst layer during start-up and shut-down with imposed VLC and/or during fuel starvation, a mixed oxide of ruthenium oxide-titanium oxide (RTO) was investigated as a suitable corrosion-resistant replacement for carbon in the anode catalyst. RTO has previously been demonstrated to be an excellent corrosion-resistant support material at the PEFC cathode (3). In this study, 40% Pt/RTO was used as the anode catalyst in a fuel cell and its durability was measured under cell reversal conditions using a protocol designed to simulate high voltage spikes at the anode. The reverse cell potential for the baseline TKK TEC10EA30E reached -2.0 V (MEA failure criteria) well before the target of 200 cycles. The reverse cell potential for the 40% Pt/RTO anode remained steady even after 400 cycles of the cell reversal protocol, indicating higher H2 starvation tolerance for 40% Pt/RTO compared to the baseline TKK TEC10EA30E (Pt/Graphitized Ketjen Black) catalyst, as shown in Figure 1. The reverse cell potential for 40% Pt/RTO did not reach -2.0 V (MEA failure criteria) even after 400 cycles. The high retention in durability of Pt/RTO catalyst compared to TEC10EA30E was attributed to the avoidance of support-corrosion-induced loss and to the excellent activity of RuO2, present in RTO, for the oxygen evolution reaction (OER). From the hydrogen oxidation reaction (HOR) study, the polarization resistance (Rp) of 40% Pt/RTO was found to be higher than that of TEC10EA30E (36.6 mOhm-cm2 compared to 23.9 mOhm-cm2) indicating lower initial HOR activity of 40% Pt/RTO. However, the Rp for HOR of TEC10EA30E increased to 6.6x its initial value after cell reversal cycling, indicating severe degradation of the catalyst layer. The Rp of the 40% Pt/RTO increased to only 1.4x its initial value after cell reversal cycling, which supported the conclusion made earlier that the anode made from 40% Pt/RTO catalyst was considerably more durable than the anode made out of baseline Pt/GKB catalyst. Using limiting current experiments, H2 gas transport resistances were measured in the anode catalyst layer and the resistances: Rdiff (due to diffusion resistance of H2 in the GDL and flow fields) and Rother (arising primarily from H2 gas diffusion in the catalyst layer) resistance values were calculated (4). Rdiff (at 101.3 kPaabs) was found to increase 10 fold for TEC10EA30E anode after durability cycling compared to a 1.3x increase for the 40% Pt/RTO anode. This indicated that the anode GDL could also have corroded under the cell reversal protocol. After durability cycling, the Rother resistance for baseline TEC10EA30E increased by a factor of 12 when compared to 40% Pt/RTO, which retained a relatively constant Rotherdue to its excellent corrosion resistance. Acknowledgments: The authors would like to gratefully acknowledge Guanxiong Wang for synthesizing the catalyst supports and catalysts used in this study and Dr. Ellazar Niangar for research design and planning and helpful discussions.

Highly active and durable methanol electro-oxidation catalyzed by small palladium nanoparticles inside sulfur-doped carbon microsphere

In this work, small palladium nanoparticles (Pd NPs) inside sulfur-doped carbon microsphere (S-CMS) were synthesized to achieve both high electro-catalytic activity and long durability for methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). The highly dispersed Pd NPs encapsulated in S-CMS with an architectural feature like the plum pudding model were obtained via a facile one-pot hydrothermal synthesis employing reduced glutathione (r-GSH) as both reducing and capping agents, followed by a simple carbonization procedure. The synthesized Pd NPs inside S-CMS was found to provide larger effective surface for MOR compared to commercial Pd/C. Mass activity 5.9 times higher than that of Pd/C was acquired, originating from the small size of Pd NPs and their interactions with the heteroatom-modified CMS coating. Due to the decreased agglomeration and dissolution, the proposed encapsulated Pd NPs also kept more stable during continuous start-stop operation, suggesting its great potential as an effective anode material to be used in DMFCs.

Quality-related process monitoring for dynamic non-Gaussian batch process with multi-phase using a new data-driven method

In this paper, a quality-related monitoring scheme of batch process using multi-phase dynamic non-Gaussian model is presented. Product quality of a batch process is difficult to be effectively guaranteed because of its frequent start-stop operation, variable operating conditions, strong dynamic and non-Gaussian character of process data. A direct dynamic PLS (DDPLS), in which weighted time-lagged matrix is used to extract dynamic components, is introduced to the dynamic problem. Meanwhile, independent component analysis (ICA) is proposed to deal with non-Gaussianity of dynamic components in DDPLS. Considering most batch processes are multi-phase in nature, in order to well describe the characteristics of every phase and set up sub-models, GMM algorithm is adopted for phase division and fuzzy membership method for transition identification. TE benchmark is used to verify the validity and superiority of our new method over traditional PLS, DPLS. Then the new method is applied to a real hot strip mill production plant.

Wear characteristics of commercial gas turbine components

Wear is one of the common degradations in a commercial gas turbine. A stainless steel grade 304 (SS 304) fuel nozzle and its collar made of nickel-based superalloy (Hastelloy X) are two vital components that normally suffer from rapid wear. During an installation, the fuel nozzle is slotted into the collar of the combustion liner. In operation, these two surfaces are subjected to high pressure from the fuel combustion, hence continuously rubbing against each other causes vibrations. During the start–stop operation, these surfaces had undergone a large relative motion. The vibration is the main cause of the wear occurrence on the surfaces. Physical properties of the worn surfaces were obtained through visual observations: wear measurement, hardness and microstructure examination. Through visual observations, fretting wear was mainly suspected as the dominant wear mode, particularly after 8,000 of running hours at high temperature and vibration. In short, this paper discusses the preliminary findings of wear on the fuel nozzle and its collar. It also discusses the changes in the mechanical properties before and after the operation. Solutions for mitigating the problem were discussed.

Tribological study of crankshaft bearing systems: Comparison of forged steel and cast iron counterparts under start–stop operation

The current work investigates the tribological functionality of crankshafts bearing systems focusing on the variation of shaft materials and their surface conditions. Tribological tests were carried out with a ring-on-disc test configuration representing the bearing-shaft contact under start–stop motion. Forged steel and cast iron shaft materials were sliding against an Al based bearing alloy. The surfaces in contact were analyzed by light and electron microscopy subsequently. The performance of forged steel depends on the overall roughness of the surface, whereas the tribological functionality of cast iron is mainly determined through its microstructure and the occurrence of metal flaps with burrs. The results prove the significance of proper surface finishing of forged steel and cast iron shaft materials in order to minimize wear in journal bearing systems. For both shaft materials good sliding performances with respect to optimized surface finishing can be noted.

Hydrogen production by bioethanol partial oxidation over Ni based catalysts

The xNiAlZn catalysts with different Ni loading (x=5, 10 and 20wt%) and nearly constant Al/Zn weight ratio (Al/Zn=0.73) were prepared by the citrate method and characterized by different techniques – SBET, TPR, XRD, XPS, and TEM. The influence of parameters, such as reaction temperature, oxygen-to-fuel molar ratio, and Ni loading on hydrogen production was investigated. The catalysts were active in the partial oxidation of ethanol at atmospheric pressure in the temperature range 600–750°C. The conversion was always complete at temperatures above 600°C, regardless of the changes in other reaction conditions. A syngas is produced which can be used in solid oxide fuel cell applications. Selectivity to hydrogen and CO increased with increasing temperature and decreased with increasing Ni loading. The highest selectivity (S) was obtained over 5NiAlZn. At 700°C this sample showed S(H2) of 90%, S(CO) of 92%, and only small amounts of byproducts such as CO2 and CH4 were detected. Morphological and structural modifications in the catalysts under reaction conditions, determined by the amount of nickel, were closely related to the activity of the samples. The effect of the parameters on side reactions and distribution of byproducts were also discussed. During 100h time-on-stream, ethanol conversion and selectivity to H2 and CO over 5NiAlZn and 10NiAlZn remained unchanged demonstrating stable performance of the catalysts. Additionally, the stability of the Ni catalyst was studied by means of simulated start–stop operation cycles during the partial oxidation reaction to simulate thermal cycles during the solid oxide fuel cell lifetime. With increasing number of thermal cycles a slight decline in ethanol conversion was observed and the selectivity to hydrogen and CO decreased. By using a molar ratio oxygen/ethanol of 0.75 a syngas with high selectivity to H2 and CO was obtained.

Impact analysis of sampling time interval and battery installation on optimal operational planning of residential cogeneration systems without electric power export

The impact of the sampling time interval for energy demands on the optimal operational planning of residential cogeneration systems without electric power export was analyzed. To improve their operational flexibility, focus was also placed on battery installation. First, an optimal operational planning problem was modeled on the basis of a mixed-integer linear programming. The features of the model are to consider the operational constraints of the cogeneration units, i.e., a daily maximum number of start–stop cycles, minimum up- and downtimes, and starting and shutdown energies, and to introduce a battery in consideration of electric power consumption in a built-in bidirectional inverter. Then, the developed model was applied to an energy-saving analysis of the following residential cogeneration systems under 5–60 min sampling time intervals for the simulated energy demands. A gas engine-based cogeneration system is operated at a constant power output; a polymer electrolyte fuel cell-based cogeneration system employs daily start–stop operation; and a solid oxide fuel cell-based cogeneration system is operated continuously. The results revealed that optimal operational planning under a sufficiently short sampling time interval is required to evaluate not only the energy-saving effect of the residential cogeneration systems without electric power export, but also the effectiveness of battery installation.

Control System for a Technological Line for the Production of Electronically Secured Cards with RFID Labels

The paper presents the structure of a control system incorporated into a process line for the production of documents secured with RFID labels. The line enables a flexible and easy manufacture of goods with different shapes and sizes in a low-cost experimental production undertaken to meet the needs of continuing improvement of prototypes and short series of innovative products with increased durability and higher level of security, which is possible to be obtained due to the application of electronic and graphical protection systems [1]. The line is intended for the assembly of multilayer documents. The documents are made of a raw stock in form of paper web, an RFID inlay and a protective film which all are glued together with the use of cold gluing and hot-melt techniques or in which a transfer tape with an adhesive film is applied. The tape and the elements mounted on it are transported and stopped by drive modules, whereas maintenance procedures are executed by actuators. These modules initiate proper strain of the tape, and as a result the material is flattened and a stable distance between the elements mounted on it is preserved. In the case of a start-stop operation and close distances between individual guide rollers, a proper tape strain and the time-space synchronization of all the modules constitute an important aspect of the control over the flexible technological system.

In-Situ Electrochemical Studies of Li-Ion Start-Stop Vehicle Batteries through a Novel Cell Design

Lithium ion batteries are now used extensively for vehicle traction applications. Because of their high specific power and long usage life, lithium ion batteries are very appealing for power assist vehicular applications. Implementation of Li-ion batteries for start-stop systems is one of the pragmatic approaches being considered for reducing vehicle fuel consumption. During start-stop operation, the engine automatically shuts down when the vehicle comes to stop and then quickly restarts when propulsion is desired by the operator. Such start-stop operations of the vehicle can effectively reduce the amount of engine idling time, leading to fuel savings.One of the main challenges for start-stop applications is meeting the cold-cranking power requirements at -30oC. Due to the kinetic limitations, pulse power performance of Li-ion batteries drop dramatically at low temperatures. Given the requirement for starting the engine at low temperature, it is typical that the cold cranking power capability determines the module size needed for start-stop systems; and therefore directly impacts the system weight and cost. It is essential to understand the source of the kinetic limitations (e.g. electrolyte resistance, electrode-electrolyte interfacial resistance, or diffusion resistance) and design a system that can dramatically improve the cold cranking power.In this talk, we demonstrate the implementation of a new cell design to investigate the pulse power performance of LiMn2O4 (LMO) / Li4Ti5O12 (LTO) batteries for start-stop applications. Figure 1 shows the schematic of the cell design; it is composed of four electrodes, with two LTO and two LMO electrodes adjacent to each other. The current collectors are porous, allowing the ions to pass through them. This type of design enables the in-situ investigation of LTO/LTO, LTO/LMO, LMO/LMO cells in a single cell while the neighboring electrodes are used for voltage monitoring. In this report, our focus is to investigate the kinetics of each individual electrode under low temperatures. Using EIS and linear voltage polarization studies, we provide insight on the source of resistance limiting the pulse power capability of the cell at low temperatures (-30oC). We found that electrolyte transport limitations control the cell performance at low temperatures, which directly impacts the cold cranking power.

固体酸化物燃料電池の起動停止を想定した多孔質電極の電気化学・変形連成解析

固体酸化物燃料電池の起動停止を想定した多孔質電極の電気化学・変形連成解析