Effect Of Impingement Research Articles

Conductive panel cooling by using coupled effects of nano-jet impingement, double rotating cylinders and magnetic field under cross-flow

Purpose This study aims to examine the effects of cross-flow and multiple jet impingement on conductive panel cooling performance when subjected to uniform magnetic field effects. The cooling system has double rotating cylinders. Design/methodology/approach Cross-flow ratios (CFR) ranging from 0.1 to 1, magnetic field strength (Ha) ranging from 0 to 50 and cylinder rotation speed (Rew) ranging from −5,000 to 5,000 are the relevant parameters that are included in the numerical analysis. Finite element method is used as solution technique. Radial basis networks are used for the prediction of average Nusselt number (Nu), average surface temperature of the panel and temperature uniformity effects when varying the impacts of cross-flow, magnetic field and rotations of the double cylinder in the cooling channel. Findings The effect of CFR on cooling efficiency and temperature uniformity is favorable. By raising the CFR to the highest value under the magnetic field, the average Nu can rise by up to 18.6%, while the temperature drop and temperature difference are obtained as 1.87°C and 3.72°C. Without cylinders, magnetic field improves the cooling performance, while average Nu increases to 4.5% and 8.8% at CR = 0.1 and CR = 1, respectively. When the magnetic field is the strongest with cylinders in channel at CFR = 1, temperature difference (ΔT) is obtained as 2.5 °C. The rotational impacts on thermal performance are more significant when the cross-flow effects are weak (CFR = 0.1) compared to when they are substantial (CFR = 1). Cases without a cylinder have the worst performance for both weak and severe cross-flow effects, whereas using two rotating cylinders increases cooling performance and temperature uniformity for the conductive panel. The average surface temperature lowers by 1.2°C at CFR = 0.1 and 0.5°C at CFR = 1 when the worst and best situations are compared. Originality/value The outcomes are relevant in the design and optimization-based studies for electric cooling, photo-voltaic cooling and battery thermal management.

Influence of operating parameters on metal flow and thermal characteristics in an EMBr-single-ruler controlled CSP funnel-shaped mould

Electro-magnetic brake (EMBr), as a necessary technique to adjust the metal flow within the mould, has been extensively applied in the continuous casting (CC) production. The EMBr technique, if appropriately applied, can take the benefit of braking effect to weaken jet impingement effect, suppress fluid disturbance and stabilize surface fluctuation. As a result, to obtain a reasonable flow pattern within the CC mould, the braking performance of EMBr technique needs to be flexibly adjusted according to the variation of operational parameters. In this article, to obtain a braking performance of a commonly used EMBr-single-ruler technique within an optimal range, the effect of operating parameters on the metal liquid flow and thermal characteristics in a compact strip production (CSP) thin slab mould is described through a 3-D mathematical modeling of multi-physical field coupling. The results illustrate that the braking performance of the EMBr-single-ruler device is weakened with the increase of the casting speed or the mould width. For the effect of the casting speed and mould width on the metal flow with the application of an EMBr device, an optimum braking performance of the EMBr-single-ruler device can be obtained under the matching parameters of a magnetic induction intensity of 0.30 T and a casting speed of 4.5 m ∙ min‒1 together with a mould width of 1500 mm. Relative to the absence of the EMBr-single-ruler device, the maximum surface fluctuation height is controlled at 6.2 mm, and the mean surface temperature is raised to 1803.6 K. Based on these findings, we conclude that the proper utilization of the EMBr-single-ruler device can avoid the entrainment of flux powder and improve the melting performance of flux powder.

Aerothermodynamic features of a Coriolis-applied smooth U channel for gas turbine blade

Rising temperature of gas turbine inlet brings great challenge for blade temperature tolerance, thus high effective cooling structure for turbine blade is vital. In this paper, aerothermodynamic features including heat transfer and pressure drop of a Coriolis-applied rotating smooth U channel are studied in detail. Both experiment and numerical methods are utilized in the study. A rotating cooling structure experiment rig system has been established and validated. The experiments were conducted in the rotating cooling structure experiment rig. Besides, RANS was chosen in the simulation. In the experiment and numerical studies, Reynolds number is constant at 16000 and Rotation number ranges from 0 to 0.024. The results indicate that Coriolis force plays a dominant and positive role on heat transfer ability on trailing wall, and that bend outlet impingement effect is the primary factor compared to Coriolis force for the Nusselt number of smooth leading surface. Besides, Coriolis force at bend region probably suppresses the formation of K–H vortices, thus boosts the flow stability, reduce pressure loss of channel and weakens second heat transfer peak of impingement at the bend outlet. What's more, the total performance of the Coriolis-applied smooth U channel at Ro of 0.006 and 0.024 are 2.18 % and 8.51 % higher than the channel at Ro of 0, which means that rotation is good for the Coriolis-applied smooth U channel and that the channel has superior performance and is encouraging in future rotating blade cooling application.

Modeling of the spray-induced wall stress acting on the ignition assistance device

This research introduces a novel wall-stress model called the Spray-Induced Wall Stress (SIWS) model, which considers the effects of spray-wall impingement and the resulting formation of wall stress within the Lagrangian spray modeling framework. The primary objective of this paper is to provide a mathematical description of the fundamental physics underlying the model. Subsequently, the proposed model is validated using existing experimental data. The remainder of the study focuses on the practical application of the model to an ignition assistance device. Specifically, this device is installed in a compression ignition engine and designed to enhance ignition in aviation-fueled high-altitude aircraft propulsion systems. The research sheds light on the mechanical impulse caused by the high-speed impact of the spray jet, leading to the accumulation of mechanical stress on the rigid body of the ignition assistance device. Previous studies on fluid–structure interaction have only considered the interaction between the gas phase and the solid wall. However, the SIWS model incorporates the additional impact of the impinging liquid spray jet. Consequently, the simulated stress distribution on the ignition assistance device can be estimated by considering both the gas-phase-induced term and the spray-induced term simultaneously.

Plume effects on Martian surface: Revealing evolution characteristics of plume-surface interaction at Tianwen-1 landing site

Engine plumes can seriously erode the Martian surface during the landing phase, causing a substantial alteration of the terrain of the immediate touchdown area and beyond. Furthermore, large amounts of lifted dust can block the view of boulders or craters, posing a serious threat to the lander's safety. Improving our understanding of the plume-surface interaction can reduce the risk of failure on a Mars landing mission. In situ studies on this subject are limited, particularly those relating to high-thrust single-nozzle engines. The Tianwen-1 represents the only Mars landing mission that employed such an engine with a thrust of ∼3000 N during the landing phase: Its success represents a unique opportunity in addressing this issue, providing an important reference for future Mars return missions. Here, we report the evolution characteristics of the plume-induced regolith erosion and the plume impingement effect measurements at the Tianwen-1 landing site. The results show that depressions and infilling are a complex process accompanying the changing of patterns as the lander descends. Specifically, the plume will seriously erode the area beneath the nozzle, causing the formation of a deep crater. Meanwhile, the expanding radial flow tends to flatten the peripheral area of the lander, which depends on the homogeneity of the regolith. To better quantify the impingement effects, some crucial parameters were extracted. The measured volume, diameter, and depth of the crater are 0.115 ± 0.019 m3, 1.50 m, and ∼0.35 m, respectively. We also calculated the total erosion area and volume as 4879.4 ± 297.7 m2 and 376.9 ± 102.2 m3. In addition, plume-induced infilling/erosion depths and rates during the landing phase were measured. Further, we investigated the shallow stratigraphic architecture exposed by the plume-induced crater beneath the lander, showing that it represents probably dust/sand-coated black rocks above at least ~35 cm thick, bright reddish materials. These results provide valuable insights into the plume impingement effects on the Martian surface and the shallow subsurface layer at the Tianwen-1 landing site, which will benefit future Mars explorations.

Effects of impinging object on geometrical flame features of horizontal jet flames

Accidental release of hydrocarbons can result in jet fires which have the potential to escalate accidental events to catastrophes. Jet fire can impinge on nearby equipment surface or a pasive firewall to make the fire plume temperature and the radiant heat flux complex. The present work experimentally investigated the flame characteristic of free horizontal jet fires and the impingement effect using propane as fuel, with different nozzle diameter, and exit velocity. To analyse the effect of flowrate to jet flame condition, the flow rates range between 30 and 600 g/min were employed with horizontal separation distance from the main source to target was at 0.8-m and 1.2-m. The results show that, the incremenet of flame features are faster for free release than impinging release. The presence of object downstream affect the flame profiles at some point. Thus, new correlations were proposed for the prediction of projected flame length and trajcetory length.

Flow and heat transfer in rotating smooth and ribbed multi-channel double-wall structure with multiple-jet impingement cooling

In this study, the heat transfer of multiple-jet impingement in rotating smooth and ribbed multichannel double-wall cooling structure with film extraction are investigated. The dimensionless jet-to-target spacing is 1, and the dimensionless jet-to-jet spacing is 3.55. In ribbed channel, the rib height is 1 mm and rib spacing is 8 mm. The experimental jet Reynolds number ranges from 2000 to 8000, and the maximum jet rotation number is 0.22. The test section contains five impingement channels. The local average convective heat transfer coefficient is measured by the “copper plate method”. The SST k-ω model is used to study the effect of rotation on the flow in channels. The results show that the heat transfer gap between high and low radius is more evident with an increase of the Roj. This is because the rotation effect increases and decreases the mass flow rate at high and low radius, respectively. Moreover, rotation can strengthen the impingement effect of the trailing side (TS) while weakening the effect of the leading side (LS) when the Roj is less than 0.06, Which causes differences in the heat transfer between the LS and TS of the impingement channel. Furthermore, affected by the ribs, the average heat transfer of ribbed target surface is improved. The area of high heat transfer region generated by impingement decreases, and an inverted butterfly-shaped high heat transfer region is generated near the film hole. Finally, the rib weakens the effect of rotation on the flow of target surface to some extent.

Benchmark Experiments for Turbulent Mixing in the Scaled-Down Upper Plenum of High-Temperature Gas-Cooled Reactors Under Accident Scenario

The time-averaged particle image velocimetry technique has been applied to measure flow mixing in the Michigan Multi-jet Gas-mixture Dome (MiGaDome) facility, a 1/12th, scaled-down model of the high-temperature gas-cooled reactor upper plenum. Measurements were first conducted with one jet injection into the upper plenum for various Reynolds numbers (Re = 1022, 2038, 4097, and 6021). The experimental region of interest includes a plane within the dome located above one of the jet inlets of interest. First- and second-order statistics are presented and discussed to analyze the local mixing process and turbulent characteristics under the effects of jet spreading and jet impingement. Results have shown that the normalized statistics of the jet reach asymptotic behavior as the inlet Reynolds number is increased. By investigating the two-dimensional budgets for the momentum equation on the measurement plane, it was concluded that the contribution of turbulent diffusion is minor near the enclosure surface where strong convection is present due to impingement. An additional measurement on a triple-jet injection case has shown that jet spreading is suppressed by a recirculation zone, which causes a redistribution of turbulent fluctuations. The detailed local fluctuation patterns/coherent structures have been examined through a proper orthogonal decomposition analysis.

Effect of Femoroacetabular Impingement on Hip Fractures

AIM: The aim of this study is to find out if there is a relationship between femoroacetabular syndrome and the risk of hip fractures that have been known with high morbidity and mortality rates.
 MATERIAL AND METHOD: Between January 1st of 2015 and January 1st of 2020, data of 243 patients with intertrochanteric fracture, 126 patients with femoral neck fracture and 250 trauma patients of over 65 years old that had admitted to our hospital’s emergency department but had no fracture on both pelvis AP x-ray and pelvis CT, were evaluated retrospectively. While central edge angle, acetabular index and singh index were measured on AP x-ray of pelvis, alfa-angle, anterior offset and anterior offset ratio were measured on pelvis CT.
 RESULTS: No significant differences were found between the groups forming the hip fracture and the control group in terms of gender, age and Singh index, indicating that these factors were homogeneously distributed between the groups and had no effect on the factors investigated (p>0.05). The central edge angle, acetabular index, alpha angle, anterior offset and anterior offset ratio were found to be significantly different (p

Influence of pin-fin patterns and geometry on the effectiveness of jet impingement boiling – A computational study

Jet impingement combined with phase change in the form of boiling has been proven to enhance heat transfer in thermal management applications. When added to surface enhancement, a further increase in heat transfer can be envisaged. Surface enhancement in the form of pin-fins are investigated numerically for a confined single jet of HFE 7100 impinging on a copper surface under boiling conditions. ANSYS Fluent with the Rensselaer Polytechnic Institute boiling model embedded in the Eulerian multiphase framework is utilised. After validating the resulting boiling curve against experiments with an in-line arrangement of pin-fins, a parametric study to investigate the effect of pin geometry, and pattern was performed. Key parameters included Reynolds numbers, pin-fin heights, pin-fin spacing and a star pattern. The objective of the parametric analysis was to limit the dry-out regions in the domain. Finding that local dry-out is decreased through decreasing flow obstruction and heat transfer is mainly linked to surface augmentation. Our results show that for the experimental configuration, 17 % of the pin-fin area experienced dry-out at the 23.2 W/cm2 input heat flux. Dry-out was practically eliminated for low pin-fins spaced far apart as expected. But, when keeping the surface augmentation factor constant in a star pattern, the dry-out area was reduced from 17 % to 1 % at the same input heat flux without a significant change in the wall superheat. In addition, the star pattern distribution allowed for a substantial increase in the critical heat flux compared to the in-line arrangement. It was also demonstrated that the pressure drop over the domain was independent of the surface enhancement as it was dominated by the jet stagnation pressure.

Cooling water intake system safety analysis based on impingement probability

Invasion or aggregation of marine organisms in cooling water intake systems (CWIS) has gradually become an important problem affecting the safety of nuclear power plants with environmental and climate changes. In this study, a 3-dimensional numerical model (TELEMAC-3D) was used to determine the impingement probability in a typical nuclear power plant with a once-through cooling system, and the effect on CWIS safety. The factors controlling impingement probability were also analyzed. Results show that (1) impingement probability decreased rapidly with an increase in distance from the CWIS. In addition, the distance of the impingement effect of a nuclear power plant with six units was mainly within 1 km of the CWIS. (2) Impingement probability increased with water withdrawal, and as distance to the CWIS increased, the increase in probability increased. (3) Generally, an increase in tide strength led to a decrease impingement probability. (4) Near the CWIS, the impingement probabilities of areas upstream or downstream of the CWIS along the tidal flow direction were much higher than those not in those areas. (5) An increase in water depth significantly reduced impingement probability. When the water depth of the CWIS increased from 5 m to 15 m, impingement probability was reduced up to 30%. Based on the above findings, the following suggestions were made to minimize the impingement effects on CWIS safety: first, the CWIS of coastal nuclear power plants should be set in an area with low aquatic biomass, strong tides, deep water, and few surface species within the range of 1 km, and second, the amount of cooling water withdrawal or velocity should be reduced as much as possible.

The Investigation of the Mixture Formation and Combustion Characteristic of the Spray-wall Impingement

In recent years, investigations into the formation of mixture or combustion characteristics of diesel spray-wall impingement have been summarized. On one hand, the air entrainment strength and fuel concentration distribution in the near-wall area during the spray-wall collision process have been studied. On the other hand, the combustion characteristics of the impinged spray, including ignition and combustion characteristics, have also been discussed. Additionally, the effect of impingement between spray and wall on real diesel engines’ operating condition has been analyzed and summarized. Results showed that increasing the pressure of the injection and shortening the collision distance could enhance the air entrainment strength of spray-wall impingement. Moreover, increasing the injection pressure, shortening the impingement distance, decreasing the environmental pressure, increasing the wall temperature, and reducing the nozzle diameter all improved the mixture formation. Conversely, reducing the environmental temperature, decreasing the nozzle diameter, and increasing the impingement distance all reduced the concentration of soot, and even achieved no soot formation. Under real diesel engine operation conditions, some of the soot formed in the spray-wall collision and deposited on the wall. The structure of these deposits was mainly a simple cluster structure composed of several basic particles, and the porous structure of the deposits was conducive to the oxidation of soot and reduced the deposition rate.

Numerical study on thermal and hydraulic performance of a stacked-plate jet-impingement/microchannel heat sink

This paper presents a stacked-plate jet impingement microchannel (SP-JIMC) heat sink with highly-dense micro-fins and numerically investigates the thermal and hydraulic performance with single-phase water as coolant. Comparative analysis with the parallel microchannel heat sink and the micro-gap heat sink indicates that the SP-JIMC can achieve a better cooling performance and improve the temperature uniformity. With the inlet water temperature of 300 K and flow rate of 1 L/min, SP-JIMC has a thermal resistance of 0.45 cm2⋅K/W and a pressure drop of 208.2 Pa, and the maximum temperature difference is 2.2 K under 100 W/cm2 over a span of 35 mm. When the flow rate is increased to 10 L/min, the thermal resistance decreases to 0.21 cm2⋅K/W, and the pressure drop increases to 5085.9 Pa. The heat transfer analysis shows the micro-fins dissipate 77.5 % with a flow rate of 1 L/min. As the flow rate increases to 10 L/min, the jet impingement heat transfer is enhanced and the percentage of heat transfer over micro-fins drops to 56.2 %. Parametric study is performed to investigate the influence of structural parameters on the heat transfer characteristics. The results show the thermal performance is improved by increasing jet length and separator thickness, and reducing separator gap. The lowest thermal resistance is achieved at a jet width of 0.35 mm when the combined effects of jet impingement and micro-fins reach the optimum situation. In order to further improve the thermal performance of SP-JIMC, dual-side micro-fins and convex/concave impinged surfaces are simulated. The results show that adding the micro-fins on the out-flow plate can increase the heat transfer percentage over fins by 9.4 % and reduce the thermal resistance to 0.39 cm2⋅K/W under a flow rate of 1 L/min. The maximum heat transfer capacity is achieved when the inlet flow rate 35 L/min under 300 W/cm2 heat flux, the average temperature of the heating surface is 349.5 K, the pressure drop is 55.1 kPa and the thermal resistance is 0.165 cm2⋅K/W.

Particle size distribution effects on cavitation erosion in sediment suspensions

Synergistic cavitation–particle erosion often occurs in high-speed sediment-laden flow in hydraulic structures and machines. However, erosion prediction is challenging due to the unclear relationship between erosion and the characteristics of sand- and silt-sized sediments, particularly the sediment particle size distribution (PSDS). In this study, vibratory erosion tests for carbon steel were conducted in suspensions of continuously graded sand–silt mixtures, and the influence of PSDS characteristics, such as the number of modes and sand-to-silt ratios, was investigated. The results indicated that both the total sediment concentration and PSDS parameters had a major impact on synergistic erosion. The changes in the PSDS patterns resulted in different erosion behaviors, even when the sand and silt concentrations were fixed. Based on the viscosity-enhancing effects of silt particles and the impinging effects of sand particles, a new theoretical model for determining the particle impact energy was developed by incorporating PSDS. A deeper understanding of the influence of PSDS and the application of the PSDS-based model can help predict and prevent synergistic erosion.

Conjugate heat transfer and flow analysis on double-wall cooling with impingement induced swirling and film cooling

A novel double-wall cooling configuration with impingement induced swirling film cooling is investigated in present paper. The effects of impingement inclined angle, blowing ratio, film hole length-diameter ratio and Biot number on conjugate heat transfer characteristics are studied by numerical simulations. The formation, development and evolution of the vortex and the reconstruction process of vortex structures are analyzed. The results indicate that impingement inclined angle can increase the swirling intensity and destroy the kidney-shaped vortex of external film cooling. The spanwise average overall cooling effectiveness is improved by about 20% when the impingement inclined angle is increased from 15° to 30°. Increasing blowing ratio makes the kidney-shaped vortex gradually evolve into multiple vortex structures in the mainstream, thereby increasing the adhesion of coolant and improving the overall cooling effectiveness. The overall cooling effectiveness fluctuates with the increase of length-diameter ratio, due to the large length-diameter ratio destroying the external film cooling. When the Biot number is small, the internal impingement induced swirling cooling determines the cooling performance, and when the Biot number is large, the cooling performance is mainly affected by the external film cooling.

Numeričko ispitivanje pojedinačnih i višestrukih udara sintetičkih mlazova na polje protoka i prenos toplote na malim rastojanjima između otvora i ploče

In the present numerical study, the thermal performance and fluid flow properties have been investigated to show the effect of single-orifice and multiple-orifice impingement of synthetic jets for dimensionless orifice-toplate distance (H/D) of lower than one. Investigations have been done for an actuation frequency of f=500 Hz, 0.10 ≤ H/D ≤ 0.75, and dimensionless pitch ratio of 1.25 ≤ Do/D ≤ 1.75. The results were validated with experimental results from the literature, and a fair agreement was obtained. The results showed that at low nozzle-to-plate spacing, lower target plate temperatures could be obtained. It was observed that with the use of multiple orifices at especially higher Do/D higher heat transfer values are present. The study was performed to add knowledge to the electronics and aviation industries where high temperatures in small cavities occur.

Study on the metallurgical function of mold electromagnetic stirring in continuous casting bloom

The metallurgical function of mold electromagnetic stirring(M-EMS) was investigated by simulation according to the following factors: flow field, temperature field, solidification, removal of inclusions, slag entrainment, and macrosegregation. When the current intensity increased from 0 A to 490 A, the rotational flow induced by M-EMS enhanced gradually, and the impinging effect of jet flow on the solidification front decreased obviously. The average speed on the top surface increased from 0.015 m/s to 0.038 m/s. The temperature of the molten steel was more uniform, and the temperature on the top surface decreased from 1788.5 K to 1785.9 K. The depth of depressions induced by the jet flow decreased from 6.1 mm to 0.7 mm. When the current intensity of M-EMS was 390 A, the removal fraction of inclusions was the highest. When the current intensity of M-EMS was 0 A, no slag entrainment occurred. With the current intensity of M-EMS increasing from 290 A to 490 A, the net slag entrainment rate was 0.003, 0.013, and 0.047 kg/s. When the current intensity of M-EMS increased from 0 A to 490 A, the minimum carbon content of negative segregation in the subsurface of the bloom worsened from 0.176% to 0.167%. For the bloom CC process, the M-EMS scheme should be weak or no M-EMS to decrease the occurrence of slag entrainment and improve the negative segregation in the subsurface of the bloom.

Simulation study of supercritical carbon dioxide jet fracturing for carbonate geothermal reservoir based on fluid-thermo-mechanical coupling model

Geothermal energy is a kind of renewable, sustainable and clean energy resource. Geothermal energy is abundant in carbonate reservoirs. However, low matrix permeability limits its exploitation. The supercritical carbon dioxide (SC–CO2) jet fracturing is expected to efficiently stimulate the carbonate geothermal reservoirs and achieve the storage of CO2 simultaneously. In this paper, we established a transient seepage and fluid-thermo-mechanical coupled model to analyze the impact performance of SC-CO2 jet fracturing. The mesh-based parallel code coupling interface was employed to couple the fluid and solid domains by exchanging the data through the mesh interface. The physical properties change of SC-CO2 with temperature were considered in the numerical model. Results showed that SC-CO2 jet fracturing is superior to water-jet fracturing with respect to jetting velocity, particle trajectory and penetrability. Besides, stress distribution on the carbonate rock showed that the tensile and shear failure would more easily occur by SC-CO2 jet than that by water jet. Moreover, pressure and temperature control the jet field and seepage field of SC-CO2 simultaneously. Increasing the jet temperature can effectively enhance the impingement effect and seepage process by decreasing the viscosity and density of SC-CO2. The key findings are expected to provide a theoretical basis and design reference for applying SC-CO2 jet fracturing in carbonate geothermal reservoirs.

Combined effect of intake pipe deflection and injection timing on In-cylinder flow and combustion characteristics of a gasoline direct injection Wankel rotary engine

To improve the fuel–air mixing and burning processes in a rotary gasoline engine to achieve efficient combustion, this paper used a computational fluid dynamics method to establish numerical simulation models for the in-cylinder flow and combustion of the rotary engine with a peripheral intake system. The effects of the intake pipe deflection angle and fuel injection timing on the in-cylinder flow, fuel distribution, and combustion characteristics were studied. The results showed that deflecting the intake pipe to the left generated a stronger tumble flow in the cylinder to effectively increase the turbulence intensity. A greater deflection angle provided a more obvious improvement. Moreover, deflecting the intake pipe to the left made the fuel distribution more towards the rear part of the combustion chamber and a more uniform fuel distribution in the cylinder. The spray impingement effect on the rotor surface was also greatly improved. Fuel injection timing also has a great impact on the mixing process of the combustible mixture in the cylinder. More advanced fuel injection timing resulted in longer mixing time of the fuel and air to make the mixture more uniform. Finally, deflecting the intake pipe to the left significantly increased the in-cylinder peak pressure and improved accumulated heat release. However, these effects became weakened when the fuel injection timing was retarded. Particularly, when the intake pipe was deflected to the left by 10°, the in-cylinder peak pressure increased most with a 27.9% increase compared with the original design. When the intake pipe was deflected to the left by 30°, the turbulent kinetic energy increased most with a 93% increase compared with the original design. The intake pipe was deflected by 10° to the left and the fuel injection timing was 250° CA BTDC, which is the most helpful for improving engine performance. This study can provide guidance for design of the injection and intake systems of the rotary engine.

Evaluation of impingement effects on high-power diesel engine mixing process with an optimized stochastic combustion model

• The mixing-controlled combustion can be modelled by a stochastic combustion model. • The impingement is evaluated by a volume ratio between squish part and total spray. • The modeling is classified into different types according to the impinging location. • The spray impingement significantly enhances the mixing rate. Spray impingement has been proved to have remarkable influence on the mixing process, and particularly for high-power diesel engines, where the dominant diffusion combustion is mixing-controlled. Therefore, in this paper, the stochastic combustion model, which has the capability to indicate the heterogeneity of the fuel–air mixing, was optimized to account for the influence of spray impingement. The combustion chamber was divided into squish region and non-squish region, and by judging the location of the spray/wall impingement, the spray was correspondingly divided into squish part and bowl part. After that, a parameter that was defined as the volume ratio between squish part and the total spray was introduced to evaluate the influence of impingement on spray mixing rate. Finally, the optimized stochastic combustion model was validated by a single-cylinder high-power-density diesel engine to have the ability to estimate the influence of spray impingement on the mixing rate of mixture and the performance of diesel combustion with a pretty good accuracy, and the results showed that, spray impingement significantly enhanced the fuel–air mixing rate, contributed to leaner and more homogenous mixture and hence optimizing the combustion.