Estimation Of Energy Losses Research Articles

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ФАЗОВЫХ ШУМОВ МОДУЛЯТОРОВ ЦИФРОВЫХ СИГНАЛОВ НА ВЕРОЯТНОСТНЫЕ ХАРАКТЕРИСТИК ПРИ ИХ ПРИЕМЕ

The results of studies of the distorting effect for phase noise of digital signal modulators, generated by short-term instability of clock generators, on the degradation of probabilistic characteristics (bit error probability) when receiving digital signals with two-dimensional "constellations" (signals with multi-position phase shift keying and signals with amplitude-phase shift keying) are presented. Research is carried out for two models of phase noises with parameters of their power with uniform and normal laws of phase density distribution. Numerical estimates of energy losses are given, obtained by theoretical calculation and computer simulation of the algorithm for receiving digital signals using the considered models of phase noise with respect to additive white Gaussian channel noise. It is shown that the energy losses calculated using the analytical relation for these signals are fairly approximate estimates in relation to the simulation results. It is also shown that for signals with 2-position phase shift keying and for amplitude-phase keying with a keying order equal to 8, in the presence of phase noise with specified powers and distribution density laws, the bit error probabilities are practically equivalent to the theoretical values of the bit error probabilities for channel with additive white Gaussian noise - in this case, the energy loss is almost equal to 0. Signals with 8-position phase-shift keying are most susceptible to the distorting effect of phase noise - for the considered phase noise power parameter, the energy loss exceeds 1.5 dB. The method of reducing energy losses when receiving the considered series of digital signals is based on the use of clock generators with a decrease in the power of phase noise

Abschätzung der weltweiten Energiebilanz von Wälzlagern

This paper presents two methods for estimating energy losses when using catalog bearings on a global scale. These methods, which are based on current standards, provide an approximation for determining the energy balance of bearings. The advantages and disadvantages of the proposed methods are discussed.

Friction-Induced Efficiency Losses and Wear Evolution in Hypoid Gears

A correct methodology to evaluate the friction coefficient in lubricated gear pairs is paramount for both the estimation of energy losses and the prediction of wear. In the first part of the paper, a methodology for estimating the coefficient of friction with a semi-empirical formulation is presented, and its results are also employed to analyze mechanical efficiency losses in a hypoid gearset. Hypoid gears have complex tooth surface geometries, and the entraining kinematics of the lubricant is quite involved. The second part of the paper showcases a simulated wear investigation based on the Archard model. The main focus is on the impact of the frequency adopted for updating the worn geometry of the gear and pinion teeth on the fidelity and consistency of the tribological outcomes. These are measured in terms of overall quantity of material removed and characteristics of the loaded contact pattern. More in detail, a sensitivity analysis is presented that compares the total wear of a hypoid gearset after 30 million cycles estimated using different geometry update steps. Contact pressures, which are necessary to perform the aforementioned analyses, are calculated through an accurate, state-of-the-art loaded tooth contact analysis solver.

Empirical roughness coefficients for moderate floods in an open conduit cave: Fullers stream canyon, Culverson Creek Cave System, West Virginia

Open conduit modeling of cave stream floods can yield useful information about water velocities and shear stresses, which can in turn be used to estimate sediment transport capabilities. All such calculations require roughness coefficients for estimating energy losses and a priori knowledge of either discharge or flow depths to set model boundary conditions. However, the difficulties associated with observing in-cave floods generally preclude measuring discharge; roughness coefficients must be assumed based on channel properties. To overcome these challenges, we monitored stream flow depths in Fullers Cave, Greenbrier County, West Virginia using pressure transducers, and simultaneously measured stage and discharge in a karst window immediately upstream of the cave. Five pressure transducers were deployed opportunistically along a 93-meter-long reach in a 10+ meter high canyon averaging 1.5 to 3 meters wide. Stage-discharge relationships were determined for the karst window using an electromagnetic flow meter for floods with peak discharges of 1.66 m3 s-1 or less. The collected data was used to obtain the empirical Manning’s n roughness values, head losses, and energy gradients. Calculated floodwater velocities are comparable to values obtained from scallops on passage walls. Major energy losses were observed where breakdown partially occludes the passage. At peak flow, Manning n values average 0.053 for reaches typified as cobble-floored canyons, but n was 0.069 in the breakdown reach. Roughness values declined exponentially with increasing discharge, but friction slopes calculated using head losses show more complex relationships with discharge. Notably, n values back calculated using bed gradients differ from those calculated using measured head losses by as little as 12%, so the use of bed gradients in roughness estimations will generally yield reasonable approximations of flow conditions. Fullers Cave experiences significantly larger open conduit floods than we observed, so additional work is needed to estimate roughness coefficients for higher discharges. Our empirical roughness coefficients can be applied to similar cave passages in other caves and contexts, including modeling slot canyon-like channels, and our methods demonstrate a technique for measuring hard to obtain data. The addition of data for open conduit conduits significantly expands the range of environments that can be modeled using empirical data beyond pipe-full caves. Applications include studying flooding, sediment transport, and bedrock erosion process. All of these topics will be addressed in Fullers in the future.

Estimation of Carbon and Biomass Energy Loss Along Shoghi-Shimla-Dhali Bypass in Mashobra Range, Himachal Pradesh

The present study was conducted during 2018−2019 to estimate biomass, carbon storage, CO2 sequestration rate, CO2 mitigation potential and biomass energy of dominant tree species like Pinus roxburghaii, Quercus oblongata, Cedrus deodara, Pinus wallichiana grown along the National Highway-22 (Shoghi−Shimla−Dhali) bypass, Himachal Pradesh, India. Present investigation was carried out by non-destructive method. About 13,967 trees were cut down during road expansion along National Highway-22. The trees <20 cm dbh dominated the structure of stand density in the study area. The diameter class IV (10−19 cm dbh) showed highest stand density among all the species occurred in study area. Among species, the proportion of Pinus roxburghaii was 64.73%, 74.22% for Quercus oblongata, 73.27% for broad leaves, 53.64% for Cedrus deodara and 51.86% for Pinus wallichiana under class (10_20 cm dbh). The maximum biomass of 2205.3 t ha-1 was observed for Quercus oblongata. Total carbon ranged from 139.26 t ha-1 to 1102.61 for diameter class 10−19 cm dbh to IE>100 cm dbh. The total carbon sequestered rate was found to be 10,306.57 t ha-1. The total CO2 mitigated potential was estimated to be 7498.24 t ha-1 with average biomass energy of 4319.88 t oil equivalent. The study revealed that Quercus oblongata was the major contributor to the total carbon loss and has highest proportion of 39.36% among all species.

Abnormal flow conduction through pulmonary arteries is associated with right ventricular volume and function in patients with repaired tetralogy of Fallot: does flow quality affect afterload?

Flow through the proximal pulmonary arteries (PAs) of patients with repaired Tetralogy of Fallot (TOF) is known to be highly disordered and associated with significant regurgitation. The purpose of this study was to evaluate 4D-Flow MRI-derived viscous energy loss [Formula: see text])-as a result of non-efficient flow propagation, and relate this parameter to standard right ventricular (RV) size and function markers in patients with repaired TOF. Thirty-five patients with TOF and 14 controls underwent comprehensive 4D-Flow MRI evaluation for qualitative flow analysis and to calculate [Formula: see text] in the main and right pulmonary arteries. Sampled [Formula: see text] indices were correlated with the MRI-derived RV size and functional indices. All patients with TOF exhibited abnormal, supra-physiologic helical/vortical formations in the PAs. Patients with TOF had significantly increased peak systolic [Formula: see text] (8.0 vs 0.5 mW, p < 0.001), time-averaged [Formula: see text] (2.5 vs. 0.2 mW, p < 0.001), and peak systolic [Formula: see text] indexed to stroke volume (0.082 vs. 0.012 mW/mL, p < 0.001). [Formula: see text] indexed to stroke volume correlated with the RV end-diastolic volume (R = 0.68, p < 0.001), end-systolic volume (R = 0.62, p < 0.001), ejection fraction (R = -0.45, p = 0.002), and cardiac index (R = 0.45, p = 0.002). The mean estimated energy loss due to [Formula: see text] with regard to input RV mechanical power was 4.7%. This study demonstrates that patients with repaired TOF have highly abnormal flow conduction through the PAs which result into extensive viscous energy loss. This significant flow-mediated energy loss is associated with the RV volume and function, and might represent considerable loss of mechanical power generated by each cardiac cycle. Future studies are required to assess whether the abnormal flow conduction adds to the RV afterload and remodeling. • Abnormal flow patterns through proximal pulmonary arteries in patients with TOF are associated with excessive viscous energy loss. • Inefficient flow conduction is associated with the RV dilation and reduced function and might contribute to the RV adaptive remodeling.

Energetics and Mixing of Stratified, Rotating Flow over Abyssal Hills

Abstract One of the proposed mechanisms for energy loss in the ocean is through dissipation of internal waves, in particular above rough topography where internal lee waves are generated. Rates of dissipation and diapycnal mixing are often estimated using linear internal wave generation theory and a constant value for mixing efficiency. However, previous oceanographic measurements found that nonlinear dynamics may be important close to topography. To investigate the role of nonlinear interactions, we conduct idealized 3D direct numerical simulations (DNS) of steady flow over 1D topography and vary the topographic height, which correlates to the degree of flow nonlinearity. We analyze the spatial distribution of energy transfer rates between internal waves and the nongeostrophic portion of the time-mean flow, and of dissipation and diapycnal mixing rates. In our simulations with taller, more nonlinear topographies, energy transfer rates are similar to previously unexplained oceanographic observations near topography: internal waves gain energy from time-mean flow through horizontal straining and lose energy through vertical shearing. In the tall topography simulations, buoyancy fluxes also play a significant role, consistent with observations but contrary to linear wave theory, suggesting that quasigeostrophy-based approximations and linear theory may not hold in some regions above rough topography. Both dissipation and mixing rates increase with topographic height, but their vertical distributions differ between topographic regimes. As such, the vertical profile of mixing efficiency is different for linear and nonlinear topographic regimes, which may need to be incorporated into parameterizations of small-scale processes in models and estimates of ocean energy loss.

Analytical and numerical investigation of mechanical energy balance and energy loss of three-dimensional steady turbulent flows in open-channels

Abstract Study about the mechanical energy balance and the energy loss of 3-D turbulent flows in open-channels has its own complexities. The governing equation of the mechanical energy in turbulent flows has been previously known and includes turbulence parameters that their calculations or measurements are not easy. In this study, a form of the total mechanical energy equation that leads to a number of significant physical insights is analytically investigated, from which analytical relationships for the energy loss estimation in 3-D turbulent flows are defined. The effect of different turbulence parameters is reflected on the new relationships and analyzed by equalizations replacing unknown correlations with closure approximations using the numerical turbulence simulation. In order to investigate the application of the analytical relationships, numerical simulations are performed by using OpenFOAM software to solve the Navier-Stokes equations with the RSM turbulence model in open-channels with different geometries. Then, the contribution of the turbulence parameters to the total mechanical energy balance is evaluated in uniform and nonuniform turbulent flows and their difference is analyzed, that leads to identify the parameters affecting the friction and local losses. The results demonstrate that the magnitudes of the turbulent diffusion, the work done by the viscous stresses pertaining to the mean motion and the viscous diffusion of the turbulence energy are substantially smaller than the other terms of the total energy equation for turbulent flows in open-channels with different geometries, while the effect of the variations of the turbulence kinetic energy and the work done by the turbulence stresses, that has not been considered in the previous mechanical energy equations, is more important in complex flows. From a practical viewpoint, in order to study the details of the total mechanical energy balance and the energy loss in 3-D turbulent flows with the presence of the secondary currents, the proposed method can be useful.

Estimate of energy loss from internal solitary waves breaking on slopes

Abstract. Internal solitary waves (ISWs) emerge in the ocean and seas in various forms and break on the shelf zones in a variety of ways. This results in intensive mixing that affects processes such as biological productivity and sediment transport. As ISWs of depression propagate in a two-layer ocean, from the deep part onto a shelf, two mechanisms are significant: (1) the breaking of internal waves over bottom topography when fluid velocities exceed the wave phase speed that causes overturning of the rear face of the wave, and (2) the changing of polarity at the turning point where the depths of the upper and lower layers are equal. We assume that the parameters that describe the process of the interaction of ISWs in a two-layer fluid with an idealized shelf-slope topography are (1) the nondimensional wave amplitude, normalized on the upper-layer thickness; (2) the ratio of the height of the bottom layer on the shelf to the incident wave amplitude; and (3) the angle of the bottom inclination. Based on a proposed three-dimensional classification diagram, four types of wave propagation over the slopes are distinguished: the ISW propagates over the slope without changing polarity and wave breaking, the ISW changes polarity over the slope without wave breaking, the ISW breaks over the slope without changing polarity, and the ISW both breaks and changes polarity over the slope. The energy loss during ISW transformation over slopes with various angles was estimated using the results of 85 numerical experiments. “Hot spots” of high levels of energy loss were highlighted for an idealized bottom configuration that mimics the continental shelf in the Lufeng region in the South China Sea.

Estimation of electrical energy losses in a DC traction rail network during heavy traffic

The growth of traction current leads to losses of electrical energy in the traction rail network, which entails losses for railway companies, including the Russian Railways holding. Additional losses arise due to the deterioration of the resistance of the elements, which occurs in a shorter time in terms of sections on which the movement of trains of increased mass and length is not carried out. Equations for estimation of the power and electrical energy losses in the DC traction rail network have been obtained. These equations are applicable both for the calculation at the sections of the circulation of freight trains, the mass of which does not exceed the weight norm established by the schedule on the route of this train, and taking into account the correction for the passage of long and heavy trains. A simulation model that makes it possible to assess the power losses in a section of a traction rail network depending on changes in the resistance of both individual elements and entire groups that make up the traction rail network, as well as to analyze the effect of the transition resistance rail-ground on the magnitude of leakage currents has been prepared. The need to constantly maintain the elements of the traction rail network in a working condition is determined. It is explained by a significant increase in losses in electrical energy when passing trains of increased weight and length, even with minor deviations of the resistance values from those established by the regulatory documentation. To maintain an operable state and reduce the likelihood of the appearance of faulty elements of the traction rail network, entailing the loss of electrical energy, it is proposed to develop automated monitoring systems for the traction rail network, which ensure the adoption of decisions on the need for maintenance or repair of an element of the traction rail network and transmit information about this repair personnel on duty.

Elaboration of a Promising Design of the HTS Conductor for the Central Solenoid of a Compact Thermonuclear Reactor TRT

The results of the preliminary development of the HTS conductor based on the VS-type design and parallel stacks for the central solenoid of the compact thermonuclear reactor TRT are presented. One of the main problems that need to be solved for the successful implementation of such projects is the creation of high-current high-temperature superconducting (HTS) conductors for Toroidal Field coils (TF) and Central Solenoid (CS) sections. The conductor must have a high engineering current density of at least 90 A/mm2. The induction of the magnetic field in the central solenoid reaches 14 T, which leads to the occurrence of large mechanical stresses due to the influence of Lorentz forces. Like many large magnets, CS has a lot of stored energy. For the safe withdrawal of stored energy from the magnet, it requires the inclusion of elements in the conductor that provide an acceptable level of electrical voltage and heating of the conductor insulation. Thus, a sufficient amount of stabilizing and reinforcing materials should be placed in the conductor. In addition, the “cable-in-conduit” type of conductor must have channels for pumping the refrigerant. Two fundamentally different versions of the conductor based on radially arranged REBCO tapes and on the basis of pre-assembled tape packages are considered. Based on the analysis of the magnetic field distribution in the conductor by finite element method, the design characteristics of the proposed conductors under various operating modes of the electromagnetic system (EMS) of the tokamak TRT was evaluated. The results of the evaluation of the current carrying capacity of the conductor and the estimation of energy losses in a changing magnetic field in comparison with known methods are also presented.

Estimation of Energy Losses in Nanocrystalline FINEMET Alloys Working at High Frequency

Soft magnetic materials are at the core of electromagnetic devices. Planar transformers are essential pieces of equipment working at high frequency. Usually, their magnetic core is made of various types of ferrites or iron-based alloys. An upcoming alternative might be the replacement the ferrites with FINEMET-type alloys, of nominal composition of Fe73.5Si13.5B9Cu3Nb1 (at. %). FINEMET is a nanocrystalline material exhibiting excellent magnetic properties at high frequencies, a soft magnetic alloy that has been in the focus of interest in the last years thanks to its high saturation magnetization, high permeability, and low core loss. Here, we present and discuss the measured and modelled properties of this material. Owing to the limits of the experimental set-up, an estimate of the total magnetic losses within this magnetic material is made, for values greater than the measurement limits of the magnetic flux density and frequency, with reasonable results for potential applications of FINMET-type alloys and thin films in high frequency planar transformer cores.

Evaluation of Energy Losses in Auxiliary Systems and Mechanisms Subject to Friction in a Stationary Diesel Engine

This research has developed a methodology to estimate energy losses associated with auxiliary systems and mechanisms subject to friction in a stationary diesel engine. The study methodology is based on mathematical models used to calculate engine friction forces and power losses. The analysis involves the cooling, the lubrication, the fuel injection system, and the engine's valve train, bearings, and piston mechanism. A stationary diesel engine with four load conditions and three rotational speed conditions has been taken as a reference for the study. The analysis of the results has showed that fuel injection is the auxiliary system with the highest energy consumption. In general, the cooling system, the lubrication, and the injection represent loss energy equivalent to 0.3%, 0.5%, and 0.9% of the chemical energy of the fuel. The interaction between the cylinder liner and the piston skirt is the main source of energy loss associated with friction processes. For valve train mechanisms, bearings and pistons it has been evidenced that these represent 1.25%, 1.91%, and 5.26% of the chemical energy of the fuel. In general, the methodology proposed in this research is a tool that allows diagnosing energy losses in auxiliary systems and engine mechanisms, which is useful for evaluating future strategies focused on energy improvement.

Abstract 9587: Combined Aortic Regurgitation and Stenosis of the Bicuspid Aortic Valve Increases Ascending Aortic Wall Shear Stress and Left Ventricle Energy Burden

Introduction: The bicuspid aortic valve (BAV) opening pattern and the degree of aortic stenosis (AS) are reportedly associated with the aneurysmal formation in the ascending aorta. Although AS is often accompanied by aortic regurgitation (AR), the combined effect of AR and AS on the wall of the ascending aorta and energy loss of the blood flow are not well understood. Hypothesis: We hypothesize that AR along with AS can increase the wall shear stress (WSS) to develop the aneurysm in the ascending aorta and increase the load on the left ventricle (LV). Methods: The effects of AR along with AS BAV on the hemodynamic features were assessed using an image-based subject-specific LV-aorta integrated computational model. The computational model was constructed based on an MRI dataset of a 72-year-old healthy volunteer. Four different types of stenosed (52% stenosis) BAV models were created: Type 0, RL fused, RN fused, and LN fused. Then, physiological boundary conditions were given based on a parameter-adjusted 0-1D cardiovascular model of the AS BAV with no AR, mild AR (17% regurgitant fraction (RF)), and severe AR (48% RF) to assess hemodynamic indices such as time-average of WSS in the ascending aorta and pulsatile energy loss index (PELI), an index to estimate energy loss in the aorta. Results: Averaged WSS was highest in the severe AR with AS BAV in 4.1±0.2 Pa, followed by the mild AR with AS BAV in 3.1±0.21 Pa, and no AR with AS BAV in 2.7±0.3 Pa. The intra-ventricular flow (LV) showed more disturbed flow in mid-diastole in severe AR with AS BAV. PELI was augmented in mild AR with AS BAV in 0.34±0.05 and severe AR with AS BAV in 0.25±0.06, compared to no AR with AS BAV in 0.19±0.16. Conclusions: AR along with AS in BAV has a great impact on increasing the WSS in the ascending aorta and increasing the energy loss of the flow in the aorta. These features imply that advanced AR along with AS in BAV may raise the risk of the development of aortic aneurysm as well as heart failure due to the increased workload on the LV.

Lifecycle cost analysis of an insulated duct with an air gap.

The insulation materials are used to reduce heat loss to/from the ducts with additional investment. This study introduces an air gap between insulation and duct surface to reduce the quantity of insulation. It uses lifecycle cost (LCC) analysis to determine the economic benefits of the air gap, considering four insulation materials for insulating the duct and natural gas as an energy source for chiller operation. The preliminary data regarding design and operating parameters were obtained from a renowned pharmaceutical company. The duct's annual energy loss was estimated for given operation hours in a year using the preliminary data and ambient conditions. The estimated energy loss through the duct was fed in LCC analysis to determine the impact of the air gap on optimum insulation thickness (OIT) corresponding to the minimum LCC and payback period. Results revealed that OIT thickness for a duct with an air gap was lower than insulated duct without an air gap, resulting in maximum cost savings within a shorter payback period. Among different insulation materials, insulated duct with expanded polystyrene was investigated as cost-effective insulation material with maximum cost savings of USD (508.8-766.8)/m/year and a payback period of 1.15-1.17years. On the contrary, the air gap was the most effective in terms of cost savings for the ducts insulated with rock wool. In conclusion, an air gap is a cost-effective design approach for duct applications.

Technical and Nontechnical Energy Loss Estimation Including Volt/Var Control for Active Distribution Systems

Technical and Nontechnical Energy Loss Estimation Including Volt/Var Control for Active Distribution Systems

An efficacious model for predicting icing-induced energy loss for wind turbines

The wind industry in cold climates has shown strong growth in recent years, but turbine icing in these regions can cause significant energy loss leading to a reduction in reliability of wind energy. Previous studies on estimating wind turbine icing (WTI) generally rely on complex physical models, and many only model the ice growth itself while failing to correlate ice growth with energy loss. It is the estimation of icing-induced energy loss that is critical for power grid management to cope with energy deficits associated with extreme weather conditions. This study focuses on bridging this modeling gap through developing an efficacious methodology for predicting icing-induced energy losses for wind turbines in cold weather events. Specifically, this study uses measurements of 11 WTI events between 2018 and 2020 from a 2.5 MW wind turbine (Eolos site, University of Minnesota) to create a statistical correlation between meteorological conditions and icing-induced energy loss. Meteorological icing parameters generated from a Weather Research and Forecasting simulation are used as inputs to the model. The model is validated against in-situ data for all events, and against two additional 1.65 MW wind turbines for one event (Morris site, University of Minnesota). When comparing average estimated energy loss to measured loss, it shows a relative mean absolute error of 37% at Eolos and 2.9% at Morris (after power curve scaling). The new model is additionally implemented for 30 large-scale wind farms in the Midwest region of the United States for estimation of WTI energy loss. The method proposed in this study enables fast and accurate prediction of WTI energy loss for wind turbines.

Correct calculation of nitrogen charge state passing through highly ionized carbon plasmas.

In the present work, we reanalyze the energy loss experimental data from Cayzac etal. [Nat. Commun. 8, 15693 (2017)10.1038/ncomms15693] using our successful ion charge state theoretical model. We predict lower nitrogen charge values, from 3.5+ to 5.0+, than the ones calculated by Cayzac etal., fitting better to their data. For energy loss estimations, we use the same stopping model, so our predictions agree better with the experimental data only due to our charge state model. Different projectile electron loss and capture processes are taken into account to estimate the projectile charge state. The projectile electron loss, or ionization, with plasma ions and free electrons are considered. On the other hand, the projectile electron capture, or recombination, with plasma free or bound electrons are also considered. The projectile ionization with plasma ions is shown as the main factor that modifies the mean charge of the projectile. Here, the new Kaganovich fitting formula for this projectile ionization is used because it seems to be more accurate than Gryzinsky's fitting in the low energy range. Our charge state model fits better with experimental data than any other model in the bibliography. Thus, it should be considered in any charge state and any energy loss estimation to obtain reliable results in future work.

Reallocation of Distributed Generation for Optimal Placement in Real-Time Delivery System Using Evolutionary Algorithms

Integration of renewable energy sources at the distribution side can boost the benefits of a smart grid. Due to a growing awareness of the environmental effect of electric power production and current technology utilized in many generations that are more environmentally friendly than traditional plants, distributed generation (DG) is gaining traction. The growing demand for power in emerging nations necessitates the use of DG to generate additional energy. Because of advancements such as greater competition, real-time pricing, and spot pricing, precise energy loss assessment is critical for obtaining more technical and economic advantages.The modeling of load is very important while finding location and size of DG. The improper modeling of load may give rise to poor benefits. This paper examines the impact of load models on the estimated energy loss in DG planning using Genetic Algorithm (GA) and Ant Lion Optimization (ALO). With the provided information, the suggested technique investigates the impact of load models on the estimation of energy loss based on the year's seasonal pattern. Comparative tests of the traditional static load model and the Voltage Dependent Load Model (VDLM) for energy loss at various load levels are conducted using one of the substations delivering energy from a state utility and a 13-bus system.

Strange wave formation and detonation onset in narrow channels

Experiments are conducted in a smooth 10 × 10 mm square cross-section, 1-m long channel, closed at the ignition end and open at the other end. Simultaneous two-direction schlieren visualization is used to investigate the three-dimensional dynamics of transition to detonation for a stoichiometric H2–O2 mixture. Results show the existence of two distinct structures before detonation onset: (i) asymmetric, composed of an oblique shock trailed by a flame, that runs preferentially along the wall, and seems to get ignited inside the boundary layer developed by the precursor shock; (ii) symmetric, referred to as strange wave in literature, propagating roughly at the speed of sound in combustion products. The combined effect of shock induced preheating and viscous heating near walls seem to be responsible for the formation of the complex flame-shock interactions observed. A simple thermodynamic analysis applied to the strange wave using the experimentally measured wave speed yield a pressure ratio of ~ 15 during its steady propagation; furthermore, an estimate of the total energy losses required to thermodynamically realize such propagation regime revealed that approximately half of the energy released by combustion should be dissipated (i.e. momentum and heat losses). Finally, simultaneous two-direction optical access allows to map the exact location of detonation onset, showing that 78 % of cases exploded in corners, highlighting the role of corner flows and boundary layers in transition to detonation at this scale.