Decrease In Power Output Research Articles

Experimental investigation on performance of hydrogen additions in natural gas combustion combined with CO2

Natural gas with H2 is widely used for lean-burn combustion, which leads to NOx emission as the main problem for it. For decreasing NOx emission and increasing thermal efficiency, the investigation on seeking the influence of H2 fractions on the mixture of CH4 and CO2 was conducted. Firstly, the ignition timing was decided through thermal efficiency and brake mean effective pressure (BMEP) for CH4 only. Then, combustion characteristics of CH4, CH4+CO2 and CH4+CO2+H2 were compared with volume percentage of H2 changing from 5% to 30%. Finally, the H2 injection strategy was checked between closed and open valve injections. Among these discussions, thermal efficiency, power output, BMEP and fuel consumption were evaluated. Results show that CO2 addition decreases power output and BMEP, leading to much more fuel consumption and lower thermal efficiency. When H2 is added, at the rich mixture conditions (λ＜1.0), power output and thermal efficiency decrease sharply as the mixture is enriched. However, at the lean-burn conditions (λ＞1.0), the decrease in flow rate of lower heating value (LHV) and increase in power output finally result in the higher efficiency with H2 addition. Moreover, when λ＞1.0, both low fuel consumption and high efficiency can be obtained with H2 addition to achieve the high BMEP. Furthermore, the open valve injection could obtain higher thermal efficiency, power output and BMEP with lower fuel consumption, suggesting that the H2 injection strategy should be well controlled with the ignition timing.

Degeneration of power output of a flexible and wearable thermoelectric module under bending fatigue

Strength and energy conversion efficiency of thermoelectric (TE) thin films upon cyclic mechanical loading are major concerns for flexible thermoelectric generator (TEG) applications. A comprehensively analysis model for the performance evaluation and fatigue failure of a TEG is constructed in this paper. The analytical solutions of temperature field, stress field, fatigue life, power output and energy conversion efficiency of the flexible TEG under cyclic loading are presented. A bending experiment is carried out to validate the analytical model and to fitting the model parameters. The results show that a continuing increase of electrical resistance and decrease of power output under the cyclic bending. The electrical resistance and power output of the TEG varies with the bending radius. The thickness ratio of the substrate to the TE film has a great influence on power output and energy conversion efficiency. A critical bending radius can be obtained from the model to provide a guideline for future flexible TEG design.

Output power boosting of a photovoltaic panel based on various back pipe structures: a computational study

The efficiency of photovoltaic panels (PV) drops due to the rise in temperature, which leads to a decrease in the PV output power. A PV/Thermal system is therefore used as a solution to increase the output power from the PV panels. Comsol Multiphysics software program, a simulator-based Finite Element Method (FEM) tool, and Matlab program simulations are used to perform this electro-thermal model. The simulation process for different back pipes follows a serpentine, and a new shape of pipes called (square shapes) which are attached under the PV module. These shapes were specifically chosen for higher conversion efficiency and increase the heat transfer of the system. Additionally, a comparison between electrical parameters and heat transfer characteristics of water and CuO/water nanofluid in a PV cooling system has been studied. The new shape leads to improve the photovoltaic (PV) module parameters, such as short circuit current ISC, open-circuit voltage VOC, and maximum power Pmax for a new shape more than the serpentine shape. These parameters are calculated under Air Mass 1.5 G (AM1.5G) with 1000 W/m2 of irradiance which is considered the average irradiance at the MENA (The Middle East and North Africa) region throughout the year. The results exhibit the PV module’s total enhancement by using the new shape with CuO nano-fluid about 24.7 %.

DOES RAMADAN FASTING AFFECT DIURNAL VARIATION ON SWIMMING PERFORMANCE AND ANAEROBIC POWER?

The aim of this study is to see whether Ramadan fasting has an effect on the diurnal variations in anaerobic power and swimming performance or not. Ten participants whose mean ± SE for age, height, body mass are 19.4 ± 1.4 years, 1.72 ± 0.1 m and 72.8 ± 6.6 kg, respectively. They are tested at 3 testing periods [i.e., one week before Ramadan (BR), the middle period of Ramadan (MPR), the end period of Ramadan (EPR)], tests are performed at 07:00 h and 17:00 h throughout every course. The test sessions were started with oral temperature and body mass measurements. Regularly doing first the Wingate test then a 25-m swim at maximal speed at each test session. During the three experimental periods, dietary intake was assessed. The result shows a significant diurnal variation of muscle power and fatigue throughout the Wingate test before Ramadan. Likewise, there is a daily rhythm in the stroke parameters and swimming performance in the mentioned period. These diurnal variations change during the month of Ramadan with a decrease in power output, swim performance, swim speed and stroke length in the evening, with no changes for the morning tests. Moreover, the diurnal variations of muscle fatigue during the three morning tests show no changes and remain the same. Whereas the three evening tests show a gradual increase towards tiredness. The results show that Ramadan may has a great effect on the circadian rhythm of muscle power and swimming performance. The time-of-day effects the anaerobic power variables during the normal days which disappear during Ramadan. Ramadan fasting effects performance in the evening; however, the morning performance tests are unchangeable during Ramadan. Additionally, Ramadan fasting has no adverse effect on energy intake, and percentages of macronutrient intake.
 
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New mechanisms of cavity facet degradation for GaN-based laser diodes

We investigated the cavity facet degradation of unsealed GaN-based laser diodes (LDs). It was found that the decrease of optical output power accompanied by undulation for unsealed LDs is related to the facet degradation. Deposits containing Ga, Al, Si, and O were observed on the LD facet for the first time, explaining the reason for the degradation behavior. Considering the shorter wavelength of GaN-based laser diodes, we propose that the splitting of water molecules induced by high-energy photons triggers the oxidation of the facets and the deposition of SiO2. The shape of the deposits is closely correlated with the field distribution on the facet, influencing the LDs’ output power. Improving the tightness of the package is necessary to avoid the fast degradation of GaN-based LDs.

Severe loss of mechanical efficiency in COVID‐19 patients

BackgroundThere is limited information about the impact of coronavirus disease (COVID‐19) on the muscular dysfunction, despite the generalized weakness and fatigue that patients report after overcoming the acute phase of the infection. This study aimed to detect impaired muscle efficiency by evaluating delta efficiency (DE) in patients with COVID‐19 compared with subjects with chronic obstructive pulmonary disease (COPD), ischaemic heart disease (IHD), and control group (CG).MethodsA total of 60 participants were assigned to four experimental groups: COVID‐19, COPD, IHD, and CG (n = 15 each group). Incremental exercise tests in a cycle ergometer were performed to obtain peak oxygen uptake (VO2peak). DE was obtained from the end of the first workload to the power output where the respiratory exchange ratio was 1.ResultsA lower DE was detected in patients with COVID‐19 and COPD compared with those in CG (P ≤ 0.033). However, no significant differences were observed among the experimental groups with diseases (P > 0.05). Lower VO2peak, peak ventilation, peak power output, and total exercise time were observed in the groups with diseases than in the CG (P < 0.05). A higher VO2, ventilation, and power output were detected in the CG compared with those in the groups with diseases at the first and second ventilatory threshold (P < 0.05). A higher power output was detected in the IHD group compared with those in the COVID‐19 and COPD groups (P < 0.05) at the first and second ventilatory thresholds and when the respiratory exchange ratio was 1. A significant correlation (P < 0.001) was found between the VO2peak and DE and between the peak power output and DE (P < 0.001).ConclusionsPatients with COVID‐19 showed marked mechanical inefficiency similar to that observed in COPD and IHD patients. Patients with COVID‐19 and COPD showed a significant decrease in power output compared to IHD during pedalling despite having similar response in VO2 at each intensity. Resistance training should be considered during the early phase of rehabilitation.

Performance Evaluation of Photovoltaic Modules by Combined Damp Heat and Temperature Cycle Test

Standard damp heat (DH), temperature cycle (TC), and combined DH-TC tests were performed using monocrystalline Si 72-cell modules with a conventional ethylene vinyl acetate (EVA) encapsulant, and their module performance and electroluminescence images were investigated. During the DH test, a significant drop (~20%) in the maximum output power of the module was noticed, primarily because of the degradation of fill factor and an increase in series resistance at 5500 h of DH testing (DH5500), presumably due to the corrosion of metal electrodes by moisture ingress. Conversely, it was revealed that temperature cycling did not seriously degrade module performance until 1400 cycles. However, the combined DH5000-TC600 test suggested in this study, with a sequence of DH1000-TC200-DH1000-TC200-DH1000-TC200-DH2000, was confirmed to provide harsher conditions than the DH-only test by causing a 20% decrease in maximum output power (Pmax) after DH3000/TC400. Promisingly, we confirmed that the module with a polyolefin elastomer encapsulant showed better durability than the module with EVA even in the combined DH-TC test, showing a limited decrease in Pmax (~10%) even after the DH5500/TC600 test.

A model for booster station matching of gas turbine and gas compressor power under different ambient conditions

Transporting natural gas across different locations require compressor stations to provide the pressure needed to keep the gas moving. This paper presents a model for matching the gas turbine and gas compressor power required under different environmental conditions to support the continuous gas transmission across other locations. The trans-Saharan gas pipeline (TSGP) project proposed to transport gas from Nigeria to Algeria has been used as a case study in this paper. The TSGP project is a Nigerian Government initiative to rejig its gas development and transportation infrastructure to meet its internal and external market demand. The numerical method used in this paper integrates the effect of the ambient temperature in the power matching of the gas turbine and gas compressors. There are 18 compressor stations across the TSGP network, and compressor station 2 is used as the reference point. The daily temperature fluctuation is segmented into hours of the day, emphasising considerable ambient temperature variation at 3:00 h, 9:00 h, 15:00 h. One benefit of the model against others in the open literature is accounting for changes in the ambient temperature along the pipeline network and gas compression stations. Accounting for changes in ambient temperature provides accuracy to near real-life operational experience for gas distribution via pipelines. The model also accounts for variations in turbine entry temperature (TET) to compensate for changes in the ambient conditions to meet the power requirements of the gas turbine and the gas compressor. The results show that for every 1% increase in ambient temperature, a 3.5% increase in power is required to drive the gas compressor and a 1% decrease in gas turbine output power. The effect of the 1% increase in ambient would require a 3.5% increase in TET to meet both the gas turbine and gas compressor requirement.

Comparison of Ultraviolet B Light‐Emitting Diodes with Single or Triple Quantum Wells

Light‐emitting diodes (LEDs) with an emission wavelength of 310 nm containing either a single or a triple quantum well are compared regarding their efficiency and long‐term stability. In addition, the influence of the thickness of the lower quantum well barrier and the quantum well thickness in single quantum well (SQW) LEDs is investigated. Electroluminescence measurements show a 28% higher initial output power for the SQW LEDs compared with the triple quantum well (TQW) LEDs because of larger spatial overlap of the carriers in the SQW as revealed by electro‐optical simulations of the LED heterostructures. However, TQW LEDs show a higher output power than SQW LEDs after 1 h operation under harsh conditions. For SQW LEDs, it is found that for a thicker lower quantum well barrier (65 nm instead of 25 nm) the initial output power decreases by ≈15%. A thicker SQW (3 nm instead of 1.6 nm) reduces the initial output power by even 45% but increases the lifetime by a factor of 6 which is attributed to reduced Auger recombination from an enhanced spatial separation of electrons and holes in the quantum wells due to the quantum‐confined Stark effect.

Review on dust deposition and cleaning methods for solar PV modules

Dust accumulation significantly affects the solar PV(Photovoltaic) performance, resulting in a considerable decrease in output power, which can be reduced by 40% with the dust of 4 g/m2. Understanding the dust deposition characteristics of PV modules can provide theoretical support for selecting dust cleaning methods and formulating cleaning strategies. This paper introduced the factors affecting dust accumulation and presented the research status of dust deposition mechanisms. Moreover, the dust cleaning methods were discussed and compared. In future research, a comprehensive particle deposition model including surface energy and other factors could be established to explore the dust accumulation mechanism. Additionally, investigating the particle deposition condition to determine the deposition of particles is beneficial to understanding the dust accumulation characteristics and predicting the dust accumulation amount. Compared with mechanical cleaning methods, the cleaning effect of electrostatic (cleaning efficiency can reach 90%), coating, and acoustic wave methods is superior. If the three methods can be combined, using an electrostatic or coating method to remove small particles and acoustic waves to remove large particles is a promising approach.

Performance Analysis and Optimization for Irreversible Combined Carnot Heat Engine Working with Ideal Quantum Gases.

An irreversible combined Carnot cycle model using ideal quantum gases as a working medium was studied by using finite-time thermodynamics. The combined cycle consisted of two Carnot sub-cycles in a cascade mode. Considering thermal resistance, internal irreversibility, and heat leakage losses, the power output and thermal efficiency of the irreversible combined Carnot cycle were derived by utilizing the quantum gas state equation. The temperature effect of the working medium on power output and thermal efficiency is analyzed by numerical method, the optimal relationship between power output and thermal efficiency is solved by the Euler-Lagrange equation, and the effects of different working mediums on the optimal power and thermal efficiency performance are also focused. The results show that there is a set of working medium temperatures that makes the power output of the combined cycle be maximum. When there is no heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are parabolic-like ones, and the internal irreversibility makes both power output and efficiency decrease. When there is heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are loop-shaped ones, and the heat leakage loss only affects the thermal efficiency of the combined Carnot cycle. Comparing the power output of combined heat engines with four types of working mediums, the two-stage combined Carnot cycle using ideal Fermi-Bose gas as working medium obtains the highest power output.

Neuromechanics and Energetics of Walking With an Ankle Exoskeleton Using Neuromuscular-Model Based Control: A Parameter Study.

Powered ankle exoskeletons that apply assistive torques with optimized timing and magnitude can reduce metabolic cost by ∼10% compared to normal walking. However, finding individualized optimal control parameters is time consuming and must be done independently for different walking modes (e.g., speeds, slopes). Thus, there is a need for exoskeleton controllers that are capable of continuously adapting torque assistance in concert with changing locomotor demands. One option is to use a biologically inspired, model-based control scheme that can capture the adaptive behavior of the human plantarflexors during natural gait. Here, based on previously demonstrated success in a powered ankle-foot prosthesis, we developed an ankle exoskeleton controller that uses a neuromuscular model (NMM) comprised of a Hill type musculotendon driven by a simple positive force feedback reflex loop. To examine the effects of NMM reflex parameter settings on (i) ankle exoskeleton mechanical performance and (ii) users’ physiological response, we recruited nine healthy, young adults to walk on a treadmill at a fixed speed of 1.25 m/s while donning bilateral tethered robotic ankle exoskeletons. To quantify exoskeleton mechanics, we measured exoskeleton torque and power output across a range of NMM controller Gain (0.8–2.0) and Delay (10–40 ms) settings, as well as a High Gain/High Delay (2.0/40 ms) combination. To quantify users’ physiological response, we compared joint kinematics and kinetics, ankle muscle electromyography and metabolic rate between powered and unpowered/zero-torque conditions. Increasing NMM controller reflex Gain caused increases in average ankle exoskeleton torque and net power output, while increasing NMM controller reflex Delay caused a decrease in net ankle exoskeleton power output. Despite systematic reduction in users’ average biological ankle moment with exoskeleton mechanical assistance, we found no NMM controller Gain or Delay settings that yielded changes in metabolic rate. Post hoc analyses revealed weak association at best between exoskeleton and biological mechanics and changes in users’ metabolic rate. Instead, changes in users’ summed ankle joint muscle activity with powered assistance correlated with changes in their metabolic energy use, highlighting the potential to utilize muscle electromyography as a target for on-line optimization in next generation adaptive exoskeleton controllers.

Agricultural soil moisture sensor based on U-bend Plastic Optical Fibre (POF)

Soil moisture has an essential role in agriculture. The growth of specific vegetation requires a certain level of soil moisture. Therefore, monitoring soil moisture is very important for farmers. In monitoring, the first essential component is the sensor. Nevertheless, the existing proper soil moisture sensor is an electric-based system sensor with low water resistance. It easily damaged in extreme environments which can reduce sensor ability. Based on these problems, we developed a soil moisture sensor based on plastic optical fibre with a U-bend structure. Optical fibre was developed as an alternative sensor due to low prices, immunity to water, and resistance to extreme conditions. U-bend optical fibre can measure soil moisture depends on changes in the refractive index. The changes of refractive index caused by changes in external force which causes a decrease in the optical fibre output power are following the concentration of water contained in the soil. Plastic material is used because of its high durability and high responsiveness in refractive index-based measurements. In this experiment, a plastic optical fibre with a U-bend radius of 30 mm and a wavelength of 930 nm is used. The result shows that the U-Bend structure plastic optical fibre sensor is highly potential to use as a soil moisture sensor with sensor sensitivity of 2.885x10 W/%VWC, R of 97.14%, and standard deviation of 0.6%.

UV-Protective, Self-Cleaning, and Antibacterial Nanofiber-Based Triboelectric Nanogenerators for Self-Powered Human Motion Monitoring.

Equipping wearable electronics with special functions will endow them with more additional values and more comprehensive practical performance. Here, we report an ultraviolet (UV)-protective, self-cleaning, antibacterial, and self-powered all-nanofiber-based triboelectric nanogenerator (TENG) for mechanical energy harvesting and self-powered sensing, which is fabricated with Ag nanowires (NWs)/TPU nanofibers and the TiO2@PAN networks through a facile electrospinning method. Due to the added TiO2 nanoparticles (NPs), the TENG presents excellent UV-protective performance, including the ultraviolet protection factor (UPF) of ∼204, the transmittance of UVA (TUVA) of ∼0.0574%, and the transmittance of UVB (TUVB) ∼0.107%. Furthermore, under solar lighting for 25 min, most surface contamination can be degraded, and the decreased power output would be recovered. Owing to the coupled effects of TiO2 NPs and Ag NWs, the TENG shows excellent antibacterial activity against Staphylococcus aureus. Due to the micro-to-nano hierarchical porous structure, the all-nanofiber-based TENG can serve as self-powered pedometers for detecting and tracking human motion behaviors. As a multifunctional self-powered device, the TENG prompts various applications in the fields of micro/nanopower sources, human movement monitoring, and human-machine interfaces, potentially providing an alternative energy solution and a multifunctional interactive platform for the next-generation wearable electronics.

Cardiorespiratory Response and Power Output During Submaximal Exercise in Normobaric Versus Hypobaric Hypoxia: A Pilot Study Using a Specific Chamber that Controls Environmental Factors.

Takezawa, Toshihiro, Shohei Dobashi, and Katsuhiro Koyama. Cardiorespiratory response and power output during submaximal exercise in normobaric versus hypobaric hypoxia: a pilot study using a specific chamber that controls environmental factors. High Alt Med Biol. 22: 201-208, 2021. Background: Many previous studies have examined hypoxia-induced physiological responses using various conditions, e.g., artificially reduced atmospheric oxygen concentration [normobaric hypoxia (NH) condition] or low barometric pressure at a mountain [hypobaric hypoxia (HH) condition]. However, when comparing the results from these previous studies conducted in artificial NH and HH including real high altitude, we must consider the possibility that environmental factors, such as temperature, humidity, and fraction of inspired carbon dioxide, might affect the physiological responses. Therefore, we examined cardiorespiratory responses and exercise performances during low- to high-intensity exercise at a fixed heart rate (HR) in both NH and HH using a specific chamber where atmospheric oxygen concentration and barometric pressure as well as the abovementioned environmental factors were precisely controlled. Methods: Ten well-trained university students (eight males and two females) performed the exercise test consisting of two 20-minute submaximal pedaling at the intensity corresponding to 50% (low) and 70% (high) of their HR reserve, under three conditions [NH (fraction of inspired oxygen, 0.135; barometric pressure, 754 mmHg), HH (fraction of inspired oxygen, 0.209; barometric pressure, 504 mmHg), and normobaric normoxia (NN; fraction of inspired oxygen, 0.209; barometric pressure, 754 mmHg)]. Peripheral oxygen saturation (SpO2) to estimate arterial oxygen saturation and partial pressure of end-tidal carbon dioxide (PETCO2) were monitored throughout the experiment. Results: SpO2, PETCO2, and power output at fixed HRs (i.e., pedaling efficiency) in NH and HH were all significantly lower than those in NN. Moreover, high-intensity exercise in HH induced greater decreases in SpO2 and power output than did high-intensity exercise in NH (NH vs. HH; SpO2, 78.2% ± 5.0% vs. 75.1% ± 7.1%; power output, 120.7 ± 24.9 W vs. 112.4 ± 23.2 W, both p < 0.05). However, high-intensity exercise in HH induced greater increases in PETCO2 than did high-intensity exercise in NH (NH vs. HH; 54.2 ± 5.9 mmHg vs. 57.2 ± 3.4 mmHg, p < 0.01). Conclusions: These results suggest that physiological responses and power output at a fixed HR during hypoxic exposure might depend on the method used to generate the hypoxic condition.

Study of the Effect of Reflections on High-Power, 110 GHz Pulsed Gyrotron Operation.

The effect of reflection is studied experimentally and theoretically on a high-power 110 GHz gyrotron operating in the TE22,6 mode in 3 μs pulses at 96 kV, 40 A. The experimental setup allows variation of the reflected power from 0 to 33 % over a range of gyrotron operating conditions. The phase of the reflection is varied by translating the reflector along the axis. Operating at a higher efficiency point, at 4:40 T with 940 kW of output power, reflected power exceeding 11% causes a switch from operation in the TE22,6 to simultaneous operation in the TE22,6 and TE21,6 modes with a large decrease of the total gyrotron output power. This switching effect is in good agreement with simulations using the MAGY code. Operating at a more stable point, 4:44 T with 580 kW of output power, when the reflection is increased, the output power remains in the TE22,6 mode but it decreases monotonically with increasing reflection, dropping to 200 kW at 33% reflection. Furthermore, at a reflection above 22%, a power modulation at 25 to 30 MHz is observed, independent of the phase of the reflected wave. Such a modulated signal may be useful in spectroscopic and other applications.

Factors Influencing the Determination of the Gyrosures Potential of Small Rivers

The article examines the main trends in the use of renewable energy sources in the world. The article examines the main trends in the use of renewable energy sources in the world. The use of renewable sources is associated with the depletion of reserves of carbonaceous minerals and a decrease in greenhouse gas emissions into the atmosphere. The article presents the main, according to the authors, reasons for the incorrect determination of the potential of small hydro resources in the Republic of Tajikistan. In recent years, many small hydroelectric power plants have been built, which are ineffective. For this, the authors propose a more detailed study of the watercourse regime and the determination of its potential for the minimum and maximum tributaries and the possibility of its use, the influence of hydrological, socio-economic factors on the determination of the potential of small rivers during the construction of small hydroelectric power plants. Zoning of small watercourses is proposed for a more detailed determination of the watercourse capacity and the possibility of constructing small hydroelectric power stations on them. The influence of altitude above sea level on the output of the rated power of installations of renewable energy sources is considered. As it shows, the experience of operation and the above statistical analysis at the existing small hydroelectric power plants with an altitude of SHPPs above sea level, their nominal capacity will decrease. The decrease in the nominal output power of small hydroelectric power plants with an air-cooling system is associated with the rarefaction of atmospheric air.

Study on the Influence of Inlet Drag at Front and Rear Sides of Compressor on the Performance of Supercharged Engine

In this paper, the influence of inlet drag at the front and rear sides of a compressor on the performance of a supercharged engine is tested. The test results show that the air flow into the engine, the combustion pressure and the engine output power decrease, the specific fuel consumption and the exhaust temperature behind the turbine increase with the increase of air intake drag. Especially when the engine at low speed operation, with the increase of inlet drag, engine performance will worsen sharply. Compared with the influence of the drag after compressor on the engine performance, the drag before compressor is more sensitive to the influence of the engine performance. When the engine speed is 1500r/min, 1900r/min and 2400r/min, the reduction in engine power caused by inlet drag in front of the compressor is 2.63 times, 4.1 times and 7.5 times that caused by the same inlet drag after the compressor. Also, the former results in an increase in specific fuel consumption 2.18 times, 3.1 times and 5.16 times of the latter. So optimizing the structure of the inlet system in front of the compressor can reduce the performance loss of the engine more effectively. The conclusions of this paper will provide guidance for the selection and matching of air filters, the spatial arrangement of multi-stage air filters in turbocharged engines, and the structural design of air intake system.

Identification of the piston machine combustion chamber tightness

PurposeThe lack of integrity of the piston machine combustion chamber manifests itself in leakages of the working fluid between the piston and the cylinder liner, at valves mounted in the cylinder head and between the head and the liner. An untight combustion chamber leads to decreased power output or efficiency of the engine, while leaks of a fluid may cause damage to many components of the chamber. The actual value of working chamber leak is a desired and essential piece of information for planning operations of a given machine.Design/methodology/approachThis research paper describes causes and mechanisms of leakage from the working chamber of internal combustion engines. Besides, the paper outlines presently used methods and means of leak identification and states that their further development and improvements are needed. New methods and their applicability are presented.FindingsThe methods of leak identification have been divided into diagnostic and non-working machine leak identification methods. The need has been justified for the identification of leakage from the combustion chamber of a non-working machine and for using the leakage measure as the value of the cross-sectional area of the equivalent leak, defined as the sum of cross-section areas of all leaking paths. The analysis of possible developments of tightness assessment methods referring to the combustion chamber of a non-working machine consisted in modelling subsequent combustion chamber leaks as gas-filled tank leak, leak from another element of gas-filled tank and as a regulator of gas flow through a nozzle.Originality/valueA measurement system was built allowing the measurement of pressure drop in a tank with the connected engine combustion chamber, which indicated the usefulness of the system for leakage measurement in units as defined in applicable standards. A pneumatic sensor was built for measuring the cross-sectional area of the equivalent leak of the combustion chamber connected to the sensor where the chamber functioned as a regulator of gas flow through the sensor nozzle. It has been shown that the sensor can be calibrated by means of reference leaks implemented as nozzles of specific diameters and lengths. The schematic diagram of a system for measuring the combustion chamber leakage and a diagram of a sensor for measuring the cross-sectional area of the equivalent leak of the combustion chamber leakage are presented. The results are given of tightness tests of a small one-cylinder combustion engine conducted by means of the set up measurement system and a pre-prototype pneumatic sensor. The two solutions proved to be practically useful.

X-Ray CT Measurement of Lithium Metal Morphological Changes of All-Solid-State Lithium Battery

Global warming, air pollution, and depletion of fossil fuels stimulate the transition of energy sources from conventional fuels to renewable energies. Electric vehicle (EV) with longer cruising range is desired to enhance the utilization of renewable energies in transportation. In order to develop the EV with longer cruising range, it is important to improve the energy density of rechargeable batteries due to the limited space in EV. All solid state battery (ASSB) is expected to realize higher energy density compared to conventional lithium-ion battery because it is able to use a higher voltage cathode and/or lithium metal anode. Hence, ASSB is promising as a power source of the next-generation EV. In order to maximize the energy density of ASSB, active material with a higher capacity is necessary. This instigates the research toward the application of lithium metal anode, which possesses the highest theoretical capacity among anode materials. The key point for realizing lithium metal anode is to secure a good contact between lithium metal anode and solid electrolyte, since the decrease of reaction area would result in the increase of interfacial resistance and the decrease of power output. In other words, lithium metal deposition and dissolution should play important roles on the cell performance through the morphological changes of lithium metal at the interface. Previous research suggested that lithium metal dissolution causes deterioration in the contact [1][2]. On the other hand, the behavior of deposition has not been revealed. In this study, we try to understand the effect of lithium metal morphological behavior during deposition on the cell performance. Here, we develop a nondestructive visualizing method of lithium metal with X-ray and visualization of lithium metal’s morphological changes under dissolution/deposition conditions is conducted. In order to observe the morphological behavior of lithium metal, it is required to distinguish solid electrolyte (SE), lithium metal, and void. However, it is difficult to distinguish void from lithium metal due to the similarity of absorption coefficients between lithium metal and argon used as inert gas. Therefore, in this study, high pressure xenon method is developed. In this method, the X-ray imaging jig (and the void in the cell) is filled with high pressure xenon (8 atm) that has significant difference in absorption coefficient compared to lithium metal, making enough contrast to distinguish lithium metal from void. By using this high pressure xenon method, the distribution of SE, lithium metal, and void (xenon) is successfully visualized. In this study, a cylindrical symmetry cell (lithium metal/SE (LPS-glass)/lithium metal, diameter of 2 mm) is used. The symmetry cell is installed into X-ray imaging jig, sandwiched by stainless-steel current collectors and pressurized to 0.5 MPa with a spring. In order to induce lithium dissolution/deposition, constant current of 0.2 mA/cm2 for 15 hours is supplied to the cell. Before and after the current supply, three dimensional images of the cell are captured by using X-ray CT. Then, these raw images are segmented into SE, lithium metal, and void regions respectively with the intensity of X-ray transmission. Figure 1 shows X-ray CT images of lithium deposition side electrode (a) before the current supply and (b) after the current supply. SE, lithium metal, and void are shown as yellow, white, and transparent respectively. Especially, the contact area of SE and lithium metal is colored by green. Before the current supply, good contact condition is achieved between the SE and lithium metal. However, after current is applied, the contact remains only around the center of the cell. Figure 2 shows the trend of the cell voltage when current is applied. Meanwhile, the voltage gradually increases. It is assumed that the decrease in the contact area between lithium metal and SE during lithium deposition would lead to this increase of voltage.