Direction Of Flame Propagation Research Articles

Optical study on the single and multiple regions of flame propagation and combustion characteristics of methane/air mixture ignited by pilot diesel

The combustion characteristics of lean methane/air mixtures ignited by single and multiple diesel sprays were investigated using an optical RCEM test bench. The experimental approach included flame natural luminescence photography, pressure data acquisition, and heat release analysis. The results revealed that the relationships of ignition delay and orifice diameter varied under single diesel and dual fuel combustion mode. Under dual fuel mode, increasing the orifice diameter of the single-orifice nozzle resulted in a reduction in ignition delay, an acceleration in flame propagation, and an increase in the heat release rate. Increasing the number of orifices multiplied the flame regions, expanded the flame propagation pathways, and enhanced the promoting effect between the flames, resulting in faster flame propagation and increased heat release. The orifice axis angle significantly affected the ignition position and flame propagation direction. An appropriate axis angle would shorten the flame propagation distance, optimize the flame propagation direction and mitigate the impediment effect between flames.

The Influence of Pre-Chamber Parameters on the Performance of a Two-Stroke Marine Dual-Fuel Low-Speed Engine

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity.

Impact of electric body force on lifted flame displacement speed: Numerical insights

Recent advancements in experimental capabilities have unveiled that externally applied electric fields primarily affect flames through flow modification induced by an electric body force. Specifically, the displacement speed of a flame could be significantly increased (decreased) by a parallel (orthogonal) electric field to the flame's propagation direction, while the flame's propagation speed remained negligibly influenced by an electric field. Here we present numerical findings attributing a modified upstream velocity to an electric body force created by redistributed space charges and a resulted electric field. Our investigation involved both simulation and experiment on propagating edge-flames from a stationary lifted flame exposed to the parallel external electric field. Nitrogen diluted methane jet in a coflow air was employed, and seven charged species (electron, H3O+, O2–, O–, OH–, CHO3–, and CO3–) were included in a reduced methane kinetic mechanism. Both the experiment and simulation consistently demonstrated that enhanced flame displacement speeds resulted from a reverse flow in the upstream, created by the electric body force. A stronger reverse flow, and thus more enhanced flame displacement, was achieved when the electric field direction was aligned with the flame propagation direction compared to the opposite direction. This difference in the reverse flow was attributed to variations in the electric field, caused by the different electric field screening zone within the flame. Surprisingly, space charge densities in the upstream were similar in both polarities, challenging previous hypothesis. The rapid transformation of electrons into O2–, CHO3–, and CO3– imposed a substantial number of charges in the upstream. This insight enhanced our understanding of how flame displacement can be controlled by applying electric fields. Importantly, we suggested that the use of a simple ionic kinetic model may fail to predict the flow field and, consequently, cannot adequately investigate modified flame characteristics.

An Experimental Study on Premixed Methane-Air Flame Propagation with Intrinsic Instabilities in a Hele-Shaw Chamber at Various Inclined Angles

ABSTRACT Flame propagation in narrow gaps can manifest intrinsic instabilities with appearance of wrinkles/cells on the reaction front, which is attributed to various physical mechanisms. For instance, the buoyancy effect is believed to be able to either stabilize or destabilize the reaction front depending on the flame propagation direction. In this paper, an experimental study of propagation of premixed methane-air flames at a variety of mixture equivalence ratios (from fuel-lean to fuel-rich) in a narrow gap (12 mm) formed by two parallel plates (termed Hele-Shaw chamber) is conducted. The magnitude of the gravitational component along the direction of flame propagation is manipulated via altering the inclined angle of the rotatable combustion chamber. Evolution features of flame-surface shapes during the propagation process under various conditions are recorded using high-speed imaging. Results show that generations of the flame wrinkles/cells are mainly driven by the Darrieus-Landau (DL) and Rayleigh-Taylor (RT) instability. For slowly propagating flames at an extremely fuel-lean condition, the RT is a pronounced mechanism, showing a stabilizing effect for downward propagating flames and a destabilizing effect for upward propagating ones. For the fast burning system at higher equivalence ratios, the DL plays a predominant role in generating instabilities among all the chamber inclined angles while the RT’s effect is noticeably weakened.

Effective Lewis number and burning speed for flames propagating in small-scale spatio-temporal periodic flows

Propagation of premixed flames having thick reaction zones in rapidly-varying, small-scale, zero-mean, spatio-temporal periodic flows is considered. Techniques of large activation energy asymptotics and homogenization theory are used to determine the effective Lewis number Leeff and the effective burning speed ratio ST/SL, which are influenced by the flow through flow-enhanced diffusion. The resultant effective diffusivity matrix is, in general, neither a scalar nor a diagonal matrix and therefore induces anisotropic effects on the propagation of multi-dimensional flames. As the flow Peclet number Pe becomes large, the flow-enhanced fuel diffusion coefficient and the thermal diffusivity behave respectively like (PeLe)σ and Peσ, where Le is the Lewis number and σ≤2 is a constant which depends on the flow and the direction of flame propagation. The maximal value σ=2 is achieved for steady, unidirectional, spatially periodic shear flows, while for steady two-dimensional square vortices, we have σ=1/2. In general, the constant σ is determined by solving a linear partial differential equation. The scaling laws for the diffusion coefficients lead to corresponding scaling laws for the effective Lewis number and the effective burning speed ratio of the form Leeff≃Le1−σ and ST/SL∼(Pe/Le)σ/2. Effects of thermal expansion and volumetric heat loss on the flame are also briefly discussed. In particular, it is shown that the quenching limit is enlarged by a factor 1/Leσ for Le<1 and diminished by the same factor for Le>1, due to the flow-enhanced diffusion. The potential implications of the results to better understand turbulent combustion are discussed. A special emphasis is placed on the dependence of the flame on Le in the presence of high-intensity, small-scale flows. In particular, it is shown that this dependence is intimately linked to the flow through Taylor-dispersion like enhanced diffusion, rather than through the traditional molecular diffusion coupled with curvature effects. The flow-dependent effective Lewis number identified may also provide an explanation to the peculiar experimental observation that turbulence appears to facilitate ignition in Le>1 mixtures and to inhibit it in Le<1 mixtures. Novelty and significance statementAn original study, combining asymptotic analysis and homogenization theory, is applied to describe flame propagation in small-scale, spatio-temporal periodic flow fields. Scaling laws are derived for the effective burning speed and the effective Lewis number for high-intensity small-scale flows, which are useful to better understand the behaviour of turbulent premixed flames in the distributed reaction zone regime. The formula for the flow-dependent effective Lewis number identified herein may explain the peculiar experimental observation that turbulence appears to facilitate ignition in Le>1 mixtures and to inhibit it in Le<1 mixtures. The high-intensity small-scale flows are shown to increase the quenching limit due to volumetric heat losses in Le<1 mixtures and decrease it in Le>1 mixtures

Effects of Flame Arrester Core with Different Thicknesses on Hydrogen/Methane/Air Explosion with Low Hydrogen Ratio

ABSTRACT In order to study the flame retardant performance of corrugated flame arrester core on the explosion characteristics of 9.5% hydrogen/methane/air premixed gas, a self-built experimental platform was used to study the explosive characteristics and propagation rules and the impact of varying thicknesses and different volumes of hydrogen. The results indicated that the corrugated flame arrester core on the explosion flame of premixed gas was observed with two scenarios, quenching and penetration. The flame is dominated by reverse vortex flow after quenching, reversing the axial direction of flame propagation. However, the flame penetration leads to more intense burning reactions as φ increases. And the increase in thickness changes the flame structure forms a spherical flame to a mushroom-shaped flame and finally form a turbulent flame. The velocity of flame decreased significantly when L = 60 mm with φ = 10% and 20% respectively. The quenching effect is more obvious in P2 with hydrogen added, and its better performance with increasing thickness, with 9.76% and 3.70% decrease when L = 40 mm with φ = 10% and 20%, respectively, and with 57.05% and 48.55% decrease when L = 60 mm with φ = 10% and 20%, respectively.

Comparison of combustion duration and end-gas autoignition in inwardly and outwardly propagating flames induced by different ignition configurations

Recently, multiple spark ignition has received great attention since it helps to increase thermal efficiency and to reduce misfire in engines. Multiple spark ignition also affects the combustion duration and thereby it can be used for knock control. However, previous studies reported opposite trends in terms of how multiple spark ignition affects engine knock. This work aims to assess and interpret the influence of flame propagation direction induced by different ignition configurations on combustion duration and end-gas autoignition/engine knock. Two simplified and idealised ignition configurations are studied theoretically and numerically. One is with infinite number of sparks at side circular wall, which induces an inwardly propagating flame (IPF); and the other is with a single central spark, which induces an outwardly propagating flame (OPF). In the asymptotic theoretical analysis, the canonical 1D formulations for IPF and OPF are reduced to 0D model. Based on the 0D model, OPF and IPF at different initial temperatures are studied and compared. Counterintuitively, it is found that the combustion duration of OPF is shorter than that of IPF when there is no end-gas autoignition. On the other hand, the combustion duration of IPF is shorter than that of OPF when end-gas autoignition occurs. Furthermore, end-gas autoignition is found to be more prone to occur in IPF than OPF. These interesting observations are interpreted through assessing the ignition delay time and different components of the absolute flame propagation speed. The theoretical results are validated by transient simulations considering detailed chemistry and transport which are conducted for IPF and OPF in an iso-octane/air mixture at different initial temperatures and pressures. Both theoretical and numerical results suggest that compared to infinite number of ignition sparks at side wall, the single central ignition has the advantages in shortening the combustion duration and reducing the tendency of end-gas autoignition.

Numerical Simulation of Premixed Methane–Air Explosion in a Closed Tube with U-Type Obstacles

Given the spatial structures and functional requirements, there are a number of different types of obstacles in long and narrow confined spaces that will cause a premixed gas explosion to produce greater overpressure and influence the flame behavior for different obstacles. Because the volume fraction of unburned gas changes with the changing height of the U-type obstacles, we can further study the influence on the volume fraction of the unburned premixed gas for the characteristics of the overpressure and the flame behaviors in the closed tube with the obstacles. The results show that after the premixed gas is successfully ignited in the pipe, the overpressure in the pipe greatly increases as the unburned premixed gas burns between the adjacent plates. Moreover, the increase of the overpressure in the closed duct becomes faster when the decrease of unburned gas becomes faster. The high-pressure areas between the plates move inversely compared with the direction of flame propagation when the height of the U-type increases, whereas the high pressure in the front of the flame moves further when the flame propagation passes all obstacles. In addition, the reversed flow structure of the flame is a coupling result for the overpressure caused by the flame propagation and the vortex between the plates. From the perspective of production safety, this study is a significant basic subject about the characteristics of overpressure and flame behaviors in a closed tube with obstacles.

Effect of diffusion time on the mechanism of deflagration to detonation transition in an inhomogeneous mixture of hydrogen-air

This study aimed to numerically investigate the effect of diffusion time between H2 injection and ignition on mechanisms behind deflagration to detonation transition (DDT) in an inhomogeneous H2/Air mixture. The combustion chamber is a closed, rectangular tube with seven obstructions and a blockage ratio of 30%. From the top wall of the air channel, hydrogen is injected with diffusion times of 3, 5, 7.5, and 10 s. As a result, the inhomogeneous mixtures with different concentrations gradients are formed in the vertical direction of flame propagation. The solution method is the finite-volume method with k−ωSST turbulence model and the Weller flame wrinkling combustion model. The current findings reveal that shortening the diffusion time between H2 injection and ignition, or increasing the mixture's inhomogeneity, causes DDT to occur faster for a lean inhomogeneous H2-Air mixture of 20%. The onset of detonation in a lean mixture is caused by shock waves focusing ahead of the flame front at the channel's top wall, where hydrogen concentration is higher. For a rich inhomogeneous H2/Air mixture of 35%, the concentration gradient weakens flame acceleration and delays the initiation of detonation. In the rich mixture, three different regimes of onset of detonation appear by changing diffusion time. In the first regime, a strong curved incident shock wave forms a Mach stem. Behind this Mach stem, chemical reactions are being activated. Finally, the flame front and the reaction region behind the Mach stem collide, causing DDT to happen. In the second regime, Mach stem does not form; however, DDT occurs in the direct vicinity of the flame where reflected shock waves from the obstacles collide flame front. In the third regime, neither the Mach stem nor the reflected shock waves play a significant role in detonation initiation.

Experimental and Numerical Study of Downward Flame Spread over Glass-Fiber-Reinforced Epoxy Resin.

For the first time, a comprehensive study of downward flame spread over glass-fiber-reinforced epoxy resin (GFRER) slabs in oxidizer flow has been carried out experimentally and numerically. Microthermocouples were used to measure the temperature profiles on the solid fuel’s surface and in the flame, and a video camera was used to measure the rate of flame spread (ROS). The ROS was found to be linearly dependent on the oxygen concentration, to be inversely proportional to the slab thickness and not to depend on the direction of the flame spread over the slab. The absence of the influence of the forced oxidizing flow velocity and the weak influence of the GFRER pyrolysis kinetics on the ROS were observed. For the first time, a numerical model of flame spread over reinforced material with thermal conductivity anisotropy was developed on the basis of a coupled ‘gas–solid’ heat and mass transfer model, using modifications of the OpenFOAM open-source code. The sensitivity analysis of the model showed that the thermal conductivity in the normal direction to the GFRER surface had a much greater effect on the ROS than the thermal conductivity along the direction of flame propagation. The numerical results show good agreement with the experimental data on the dependences of the ROS on oxygen concentration, slab thickness and the N2/O2 mixture flow velocity, as well as temperature distributions on the fuel surface, the maximum flame temperatures and the flame zone length.

Effects of obstacle layout and blockage ratio on flame acceleration and DDT in hydrogen-air mixture in a channel with an array of obstacles

Numerical simulations were performed to study flame acceleration and deflagration-to-detonation transition (DDT) in hydrogen-air mixture in a channel with a two-dimensional array of cylindrical obstacles. A high-order numerical algorithm with adaptive mesh refinement was applied to solve reactive Navier-Stokes equations. The effect of obstacle layout was examined by considering three layouts at a fixed blockage ratio of 0.5: staggered, inline-concentrated, and inline-scattered. Three blockage ratios, 0.33, 0.5, and 0.67, were used for the case of staggered obstacles to explore the influence of blockage ratio. The results show that both obstacle layout and blockage ratio have significant effects on flame acceleration and DDT occurrence, although the basic mechanism of detonation initiation is consistent for all the cases involving shock focusing. In the staggered case, the head-on collisions of flame and pressure waves with obstacles greatly promote the growth of flame surface area and thus lead to the fastest flame acceleration and shortest detonation onset time. In the inline-concentrated case, flame propagates slower than that in the staggered case due to smaller flame surface area. However, compared to the zigzag path in the staggered case, the straight passages parallel to flame propagation direction in the inline-concentrated case are more conducive to producing strong shock focusing and thus result in the shortest DDT distance. In the inline-scattered case, the straight passage along the centerline of channel facilitates the early acceleration of flame, but it has the slowest flame propagation in lateral directions and thereby the longest DDT time and distance. For the staggered obstacles at different blockage ratios, flame acceleration rate increases with increasing blockage ratio. The occurrence of DDT is hindered by the most congested obstacles, because the shock focusing is insufficiently strong to initiate detonation after passing through the excessively narrow gaps.

Numerical Simulation of Interaction between Large-Scale Congestion and Vent during the Natural Gas Explosion in a Kitchen

The influence of large-scale congestion on a confined natural gas explosion in a typical Chinese kitchen was studied using the computational fluid dynamics technology. It was found that opening the explosion venting surface promotes the development of turbulence, flame propagation velocity, and multipeak overpressure in the explosion flow field. Large-scale congestion can significantly strengthen the influence of the explosion venting surface on the flow field; the congestion and the explosion venting surface have a synergistic effect on the explosion flow field. At the moment of gas explosion, the flow fields in each area of the kitchen exhibit different distribution characteristics. A flow field near small-scale congestion is more likely to produce greater turbulence, combustion rate, and flame speed. The obstruction effect of large-scale congestion perpendicular to the flame propagation direction is dominant. The indoor flame propagation speed and overpressure development speed increase and the peak combustion rate and indoor peak overpressure decrease with an increase in obstacle blockage. Increases in the large-scale volume congestion rate and volume blockage in the kitchen induce changes in the indoor flame propagation mode and increase the external explosion overpressure. This paper investigated the correlation behavior between large-scale congestion and vent surface in a typical Chinese civil kitchen during natural gas explosion process and provided important support for understanding the mechanism of congestion on gas explosion process and the distribution of explosion hazards in a kitchen.

Flow directed spark stretch and flame propagation in a high-tumble production engine

This study performs endoscopic high-speed imaging to enhance the fundamental knowledge of in-cylinder flow structure and flame development process in a selected high-tumble production engine. The endoscopic high-speed particle image velocimetry (eHS-PIV) was performed for varied engine speeds and intake valve closing (IVC) timings to evaluate their impact on the in-cylinder flow structure in a motored engine condition. On another endoscope engine sharing the same hardware, high-speed flame imaging was conducted to visualise spark stretch and flame propagation. The flow and flame measurements were repeated for over 100 cycles and the ensemble-averaged results are compared. The eHS-PIV showed that a strong tumble vortex is generated during the piston compression with the flow directed towards the exhaust side. As the piston reaches top dead centre (TDC), however, a complex flow breakup involving multiple flow components occurs. This is followed by lateral flow vectors travelling back towards the intake side, which is termed as the bounce-back flow. For a tested engine speed range of 1700–2700 revolutions per minute (rpm), 2500 rpm shows the most significant bounce-back flow as a result of competition between the remaining exhaust-ward tumble flow strength and the newly formed bounce-back flow strength. At a retarded IVC timing, the flow loss leads to a weakened tumble flow and subsequently no bounce-back flow formation to maintain the exhaust-ward TDC flow direction. From the comparison between the flow results and spark/flame high-speed images, a strong positive correlation is found between the TDC flow direction and spark plasma stretch, and subsequently the flame propagation direction. The findings indicate that the TDC flow direction should be considered as a key parameter in the engine design and operating condition settings.

Multi-parameter imaging of in-cylinder processes during transient engine operation for the investigation of soot formation

Transient engine operation of direct-injection spark ignition engines can result in high particulate number emissions. To investigate the causes of soot formation, an engine test rig was developed to perform detailed measurements of real transient operation. For this purpose, a single-cylinder full-metal engine with a real combustion chamber geometry was equipped with minimally invasive optical accesses. Simultaneous high-speed endoscopic PIV, spray visualization, and combustion imaging were applied to investigate the in-cylinder processes in detail. Endoscopic PIV was first compared in the central symmetry plane with classical PIV performed at the equivalent optical engine at steady-state operation for verification. Then the engine parameters of a tip-in performed by the corresponding four-cylinder engine, which led to high particle number emissions, were applied to the single-cylinder engine. The engine parameters were in a good agreement and particle number emissions due to the maneuver were within the same range of several 106 #/cm3. In total, 19 repetitions of the tip-in maneuver were analyzed with respect to the in-cylinder processes and repeatability of engine parameters. Furthermore, the in-cylinder flow field during the late compression stroke, flame propagation, and soot luminosity of single cycles during the tip-in indicated cause-and-effect chains for the formation of pool fire and soot at the injector tip. The direction of the flow below the spark plug influenced the direction of flame propagation. An early arrival of the flame enhanced the formation of soot from fuel films formed on the piston surface or at the injector. In engine applications, counter measures can be applied to reduce the particle number emissions when accounting for these indicated cause-and-effect chains.

DNS analysis of boundary layer flashback in turbulent flow with wall-normal pressure gradient

The presence of swirl in combustion systems produces a marked change in their boundary layer flashback behaviour. Two aspects of swirling flow are investigated in this study: the effect of the swirl-generated wall-normal pressure gradient, and the effect of misalignment between the mean flow direction and the direction of flame propagation. The analysis employs Direct Numerical Simulation (DNS) of fuel-lean premixed hydrogen-air flames in turbulent planar channel flow with friction Reynolds number of 180. The effect of swirl on the flashback process is investigated by imposing a wall-normal pressure gradient profile. Analysis of the DNS data shows how the resulting differences in flow field and flame topology contribute to the differences in the overall flashback speed. Misalignment of the flow and propagation directions leads to asymmetry in the flame shape statistics as streaks of high velocity fluid in the boundary layer cleave into the flame front at an angle, yielding an increase in flame surface density away from the wall. Swirl has a stabilising effect on the turbulent flame front during flashback along the centre-body of a swirling annular flow due to the density stratification across the flame front, and produces a reduction in turbulent consumption speed. However the swirl also sets up a hydrostatic pressure difference that drives the flame forward, and the net effect is that the flashback speed is increased. The dominance of hydrostatic effects motivates development of relatively simple modelling for the effect of swirl on flashback speed. A model accounting for the inviscid momentum balance and for confinement effects is presented which adequately describes the effect of swirl on flashback speed observed in previous experimental studies.

Difficulties on the determination of the flammability limits of fuel mixtures by the Law of Le Chatelier

In the present article the inaccuracies related to the estimation of the upper flammability limits of fuel mixtures in air by using the Law of Le Chatelier are analyzed.A derivation of the Law of Le Chatelier was provided in order to understand the necessary conditions for its applicability. A statistical analysis was applied to the available experimental data for the lower and upper flammability limit of fuel mixtures. It was observed that the direction of flame propagation has a significant effect on the inaccuracies.The fuel mixtures for which the absolute values of the relative errors were higher than 10 % were selected for further study. Through the determination of the laminar flame speeds it was shown that those deviations were related to different heat release rates at the experimental and calculated upper flammability limits, respectively. A laminar flame speed sensitivity analysis was also applied to a selected group of fuel mixtures and two competing reactions for each mixture at the upper flammability limit were identified.

Experimental study on the influence of obstacle aspect ratio on ethanol liquid vapor deflagration in a narrow channel

A series of experimental tests were conducted in a narrow obstructed channel to investigate the influence of obstacle distribution mode (unilateral and bilaterally symmetrical distribution) and obstacle aspect ratio (the width-to-height ratio in flame propagation direction) on vapor deflagration. Rectangular obstacles with different aspect ratios 0.9–2.1 were used. The flame propagation speed, flame front structure, overpressure and local temperature near obstacles were recorded and analyzed. The results indicated that different obstacle distribution modes would not fundamentally alter the propagation mechanism of deflagration flame and overpressure. The shear action of obstacle edges and the confined space structural form between the obstacle and the channel boundaries both exerted a significant effect on deflagration flame propagation. And two acceleration stages existed in the deflagration, and the flame speed peaks appeared above obstacle and near the channel portal, respectively. Specifically, when aspect ratio was 1.8, the maximum flame speed peaked to 102.5 m/s. Moreover, obstacle aspect ratio has shown a significant influence on flame front, and the flame front structure experienced complex changes as it passed through obstacle. What's more, an interesting reverse flame phenomenon was observed, which resulted in a larger area of violent flame combustion. The maximum length of reverse flame decreased firstly and then increased with the increase of obstacle aspect ratio, which probably ascribed to the inertial force of fluid. Accordingly, a simple empirical equation was proposed to predict the reverse flame length during flame propagation in the narrow obstructed channel. This equation performs well in prediction of reverse flame length in current application range. Meanwhile, the local temperature peak is closely related to the local deflagration reaction intensity affected by obstacle aspect ratio. In addition, it is also found that the deflagration overpressure and flame propagation involved the obvious coupling mechanism. Deflagration overpressure and flame speed reached peaks almost simultaneously. This coupling mechanism could significantly expend the impact range of deflagration.

An energy storage capacity optimization method based on partition

With the vision of large-scale deployment of grid-connected distributed energy storage system (ESS) in the distribution network, it is necessary to study the capacity optimization of ESS for striking a balance among investment, renewable energy (RE) consumption, power supply security and price arbitrage. In this paper, an ESS partition model based on the improved flame propagation model is proposed. The results of ESS partition are obtained by constructing indexes such as the flammability of nodes, the wind direction of flame propagation, and the speed of flame propagation. Then, an optimization method for ESS capacity in partition is established, which is to maximize the annual net profit and the integer programming method is used to solve the model. Finally, the effectiveness and feasibility of the method are verified by conducting case studies on the IEEE 33 bus distribution network system. The case study results show that the rational configuration of ESS capacity can improve the economy of planning, and the proposed method can improve the Photovoltaic (PV) local consumption ability and power supply reliability of distribution network.

Optimal Location and Capacity of the Distributed Energy Storage System in a Distribution Network

Given the current situation of large-scale energy storage system (ESS) access in distribution network, a practical distributed ESS location and capacity optimization model is proposed. Firstly, a weighted voltage sensitivity is proposed to select the grid-connected node set of ESS. On this basis, the distributed ESS location model is established, which aims at reducing voltage deviation and active power loss of the distribution network. Then, an ESS partition method based on the improved flame propagation model is proposed, and the partition results are obtained by constructing the flammability of nodes, the wind direction of flame propagation, speed of flame propagation and other indicators. Based on partition results, the capacity optimization model is established with the maximum annual net income of energy stored in the partition as the objective function. Finally, the improved IEEE-33 bus distribution network is used to demonstrate the effectiveness and feasibility of the proposed model.

Effect of Pre-Combustion Chamber Nozzle Parameters on the Performance of a Marine 2-Stroke Dual Fuel Engine

In recent years and with the increasing rigor of the International Maritime Organization (IMO) emission regulations, the shipping industry has focused more on environment-friendly and efficient power. Low-pressure dual-fuel (LP-DF) engine technology with high efficiency and good emissions has become a promising solution in the development of marine engines. This engine often uses pre-combustion chamber (PCC) to ignite natural gas due to its higher ignition energy. In this paper, a parametric study of the LP-DF engine was proceeded to investigate the design scheme of the PCC. The effect of PCC parameters on engine performance and emissions were studied from two aspects: PCC nozzle diameter and PCC nozzle angle. The results showed that the PCC nozzle diameter affected the propagation of the flame in the combustion chamber. Moreover, suitable PCC nozzle diameters helped to improve flame propagation stability and engine performance and reduce emissions. Furthermore, the angle of the PCC nozzle had a great influence on flame propagation direction, which affected the flame propagation speed and thus the occurrence of knocking. Finally, optimizing the angle of the PCC nozzle was beneficial to the organization of the in-cylinder combustion.