Piston Surface Research Articles

Establishing Thermal Stability in an Optically-Accessible CIDI Engine

<div class="section abstract"><div class="htmlview paragraph">Optically-accessible engines are a key tool for the study of sprays, mixing, and ignition and combustion phenomena in internal combustion (IC) engines. Due to their construction, they are typically operated for limited durations, resulting in significant thermal transients in the in-cylinder surface temperatures and cycle-to-cycle in-cylinder gas temperature. This makes collection of highly repeatable data difficult and can introduce considerable uncertainty in the in-cylinder thermal conditions. In this paper, rigorous analyses of transient in-cylinder boundary conditions and in-cylinder gas temperature were performed in an optically-accessible compression-ignition engine. Piston surface thermometry, in-cylinder pressure measurements, and in-cylinder gas thermometry were employed to determine the engine warmup time required to reach a quasi-steady thermal state for motored operation over a range of intake air temperatures and pressures from 300-420 K and 100-300 kPa, respectively. The effect of fueling on thermal stability was investigated for single-injection mixing-controlled compression-ignition combustion utilizing a range of skip-fire ratios from 5:1 to 50:1 and loads from 0.8 to 10.1 bar gross indicated mean effective pressure. Both optical and metal pistons were studied. A motored warmup time of 300 s was found to be sufficient for the engine to reach a thermally stable condition regardless of piston material or intake condition. Piston temperature was found to increase with load, but the increase was modest for even the highest load studied (~4 K) for 10 injection sets typical of late direct-injection optical engine studies.</div></div>

Thermal efficiency improvement of super-lean burn spark ignition engine by stratified water insulation on piston top surface

In order to improve thermal efficiency of spark ignition engine under super-lean burn conditions (excess air ratio [Formula: see text]), thermal stratification technique by in-cylinder water injection toward piston surface (stratified water insulated combustion architecture), in which low temperature water vapor layer is formed on the surface, is proposed. From the water spray visualization using the optically accessible engine, injected water is distributed near the piston top surface at ignition timing and thermal stratification can be achieved in the case that water injection timing (SOIw) is set at earlier stage of a compression stroke. In addition, heat flux on the piston surface measured at the same time is reduced by water injection. The 0.5-L single-cylinder engine test at λ = 2.0 at a constant ignition timing also shows that water injection at earlier stage of a compression stroke makes it possible to mitigate knock without significant increase in combustion instability. On the other hand, part of water is distributed near the spark plug at ignition timing with the water injection at SOIw = −60 °ATDC, resulting in unstable combustion. In addition, the engine test at λ = 2.0 and water/fuel ratio(W/F) = 18% shows that knock mitigation by water injection enables spark advance and following combustion enhancement. As a result, combustion period becomes short and cooling loss decreases, followed by the 1.0-pt improvement of gross indicated thermal efficiency. Moreover, the engine can be operated at minimum spark advance for best torque by increasing W/F up to 35%. Finally, stratified water insulated combustion architecture concept is applied at λ = 1.9 with a higher compression ratio of 17, showing that water injection at SOIw = −120 °ATDC and W/F = 50% enables minimum spark advance for best torque operation, and remarkably high gross indicated that thermal efficiency of 52.63% can be achieved with a sufficiently low knock level and coefficient of variation of indicated mean effective pressure.

Improving the usability of biodiesel blend in low heat rejection diesel engine through combustion, performance and emission analysis

Utilization of biodiesel which is of renewable in nature was enhanced in single cylinder, 4-S diesel engine based on combustion, performance and emission analysis. Esterified jatropha biodiesel (EJO) at 4%, 10% and 20% was added in normal diesel by v/v ratios to form B04, B10 and B20 blends. The crown surfaces of piston, cylinder head and valves were coated with 250 μm thick mullite material (Metco 6150) to form low heat rejection engine (LHRE). The optimum EJO blend for the conventional engine (CE) as well as LHRE was investigated by comparing their characteristics from all biodiesel blends with the normal diesel of CE operation. B10 was obtained as an optimum blend for both engines. For CE at B10 operation, the CO, HC emissions (except NOx) and brake thermal efficiency (BTE) were reduced as compared with CE at diesel fuel. For LHRE operation, the emissions were further reduced but BTE was slightly reduced. Finally to improve the usability of biodiesel, 5% anhydrous ethanol was added into optimum blend to form E05B10 mixture. Ethanol required higher latent heat for evaporation; this caused reduction of NOx and improved BTE. Emission load on environment (GWP, RIP and TAP) was reduced by optimum blend operation.

Further study on wall film effects and flame quenching under engine thermodynamic conditions

In direct-injection engines, the formation of fuel wall film on piston surface and liner wall is a primary cause for emissions of unburnt hydrocarbons and particulate matter. It is therefore important to investigate the behavior and effect of a wall fuel film under typical engine conditions. Following our previous study of wall film effects on flame propagation and quenching under constant thermodynamic conditions (Tao et al. IJER, 2018), more complexities rooted in real engine conditions have been considered in the current work, including two real engine in-cylinder thermodynamic trajectories occurring at catalyst warming (CW) and low-speed high-load (LSHL) conditions, varying fuel wall film thickness accounting for both vaporization and condensation, and the stagnation boundary layer flow over the wall film. To shed light on the role of wall heat transfer, parameter sweeping of wall temperature is conducted from 303 K to 363 K. Two representative wall film models using empirical vaporization rate and gas-liquid interface heat flux are compared with our numerical simulation. A good correlation between vapor boundary thickness and quenching distance has been found. Competition between enhanced vaporization due to tangential convection and aggravate condensation from elevated pressure is also demonstrated. The results lead to useful insights into the behavior of a wall film in real engine in-cylinder thermodynamic conditions and could be used to construct low dimensional empirical wall film models in three-dimensional engine combustion modeling.

ANALYSIS OF CI ENGINE PERFORMANCE BY THERMAL BARRIER COATINGS ON PISTON UNDER DIFFERENT COOLING RATES

To analyze performance of a twin cylinder four stroke CI engine whose piston is coated with a ceramic material and experiments are carried out at different cooling rates. Research & Development technique is used for decreasing costs and consumption of fuel in internal combustion engines and technological innovation studies are going on continuously. Through various constructional changes engine efficiency development efforts are augmented day by day; for instance, parallel to development of advanced technology ceramics, ceramic coating applications in IC engines grows fast. In order to get better engine performance, fuel energy must be converted to machine energy at the most possible rate. Lower heat rejection from combustion chamber through thermally insulated components leads to increase in available energy that will raise the cylinder work and total energy carried by the engine exhaust, which could be also utilized. The research engine was a four-stroke, direct injection, twin cylinder, water cooled CI engine. It was tested at constant speed and different load conditions before coating. Also Piston was coated with 0.5mm size of Zirconia (ZrO2) over a 150 μm thickness of NiCrAlY bond coat. The engine was tested at standard conditions to study the effect of coated surfaces of piston on its performance and emissions of the engine. The ceramic-coated engine performance is to be compared with conventional uncoated engine performance. Engine exhaust such as NOx CO, CO2 and Unburned Hydro Carbons are to be determined with the aid of exhaust gas analyzer by conducting several experimental cycles at various loads i.e., at 0.5,1,1.5,2,2.5& 3 K.W load after piston is coated by ceramic material.

Effects of ethanol injection strategies on mixture formation and combustion process in an ethanol direct injection (EDI) plus gasoline port injection (GPI) spark-ignition engine

The mixture formation process is vital for ethanol direct injection (EDI) plus gasoline port injection (GPI) engine, as the mixture preparation quality directly affects the combustion process and emission characteristics, especially for the dual-injection system. In this study, engine tests were first conducted to investigate the effects of ethanol injection timings (430 °CA, 570 °CA, 620 °CA and 670 °CA) and injection pressures (40 bar, 60 bar and 90 bar) on engine performance and combustion process. Then, the numerical simulations were performed with the focus on detailed mixture formation process, including in-cylinder flows, wall wetting and fuel evaporation. The experimental and numerical results indicated that the injection timing has a significant effect on the mixture formation in EDI + GPI engine. Due to the long evaporation time and strong in-cylinder TKE, early injection timing (430 °CA) can lead to a uniform mixture and complete combustion. The effect of ethanol injection pressure on mixture formation was not significant at this ethanol injection timing. As the injection timing was retarded, due to the reduced evaporation time, the formation of the homogeneous mixture became harder, and the effect of injection pressure on the mixture preparation became obvious. At injection timing of 620 °CA, high injection pressure generated high fuel spray momentum, which deformed the original in-cylinder vortex, and more ethanol fuel collided on the piston surface and the wall, resulting in uneven distribution of the mixture and poor combustion. When the injection timing was retarded to 670 °CA, the injection pressure of 60 bar could obtain a good balance among the fuel evaporate rate, the amount fuel impinging on the wall and the fuel evaporation time, resulting more complete combustion.

Features of theoretical models of hardening of piston aluminum alloys in aqueous electrolytes

Currently, an effective method of increasing the surface strength and heat resistance of the piston bottom is the method of electrical deposition of chemical coatings based on various compositions. The article deals with the theoretical aspects of the formation of oxide films on piston aluminum alloys during microarc oxidation. Possible schemes of formation of barrier and outer layers of surface coating in aqueous electrolytes are also considered. The mechanism of formation of the interface and possible schemes of deposition of nonmetallic inclusions on the surface are shown. The stepwise formation of oxide layers on the piston surface, which has a fundamental difference from conventional films obtained by anodizing, is described.

Temperature analysis of oxide coating of aluminum alloy piston used in diesel engine

The task of increasing in the efficiency (lowering of fuel consumption) of diesel engines is considered. The distribution of temperatures and stresses on the surface of oxide-coated piston coated by galvanic plasma modification is analized. The basic equations are obtained using the finite element method and solved using the ANSYS Workbench 18.1 and Solidworks 17. It is found thatthe surface temperature increases with increasing of coating thickness due to decrease in thermal outflow. The increase in maximum temperature relative to the uncoated piston is 64.3 % for 0.13 mm thickness coating. The temperature curves obtained for different thicknesses of the bottom are similar to each other and approximately equidistant. The numerical modeling showed that higher temperature in the combustion chamber is provided by thermal barrier coatings, which increases the efficiency of the engine. Lowering the surface temperature of the piston (substrate) creates favorable conditions for the piston to work.

Experimental assessment of new insulation coatings for lean burn spark-ignited engines

Clean and highly efficient internal combustion engines will still be necessary in the future to meet the ambitious CO2 emissions reduction targets set for light-duty vehicles. The maximal efficiency of stoichiometric Spark-Ignited (SI) gasoline engines has been steadily increasing in recent years but remains limited by the important relative share of cooling losses. Low heat rejection engines using ceramic barrier coatings have been presented in the past but smart insulation coatings are gaining a renewed interest as a more promising way to further increase the engine maximal thermal efficiency. This article is highlighting some important effects of smart insulation coatings developed for lean-burn spark-ignited gasoline engines. Five different coatings with low heat conductivity and capacity are applied on aluminum engine parts with the atmospheric plasma spray technique and are tested with two different engines. The laser induced phosphorescence technique is firstly used in an optical single cylinder engine to quantify the thermal performance of these coatings in terms of temperature swing during combustion. A maximal increase in the piston surface temperature of around 100 °C is measured at low load, confirming thus the expected impact of the low heat conductivity and capacity, and suggesting thus a positive impact on fuel consumption. Thanks to the tests performed with a similar metal single cylinder engine, it is shown that the unburned hydrocarbon emissions can significantly increase by up to 25% if the open porosity on top of the coating is not properly sealed, while the surface roughness has no impact on these emissions. When applied on both the piston and the cylinder head, the optimized coating displays some distinct effects on the maximal heat release rate and NOx emissions, indicating that the thermal environment inside the combustion chamber is modified during combustion. Thanks to the temperature swing between cold and hot engine phases the volumetric efficiency can also be kept constant. However, no increase in efficiency can be measured with this optimized coating which suggests that the heat balance is not affected only by the reduction in the temperature differential between the walls and the gas.

Piston Failure Analysis on Four-Wheeled 1000cc Engine Cylinder Capacity

Pistons are one of the main components of a 1000 cc engine that functions as a pressure suppressor and a recipient of pressure combustion in the combustion chamber. In the examination of the 1000 cc sedan engine that has been operating for 30,000 hours found a rough sound on the engine and experienced loss compression on the cylinder block number 2. The purpose of the study was to obtain the factors causing the deformation of the piston 1000 cc sedan vehicles. The research method used is metallographic observation using ASTM E 3 and ASTM E 112, testing hardness using ASTM E 92 and SNI 19-0409-1989 and testing chemical composition using ASTM A 751. The results of research on piston damage can be seen that observation macrostructure proves that there is plastic deformation on the surface area of the piston material, the results of microstructure observation are known to occur microcrack on the top surface of the right side of the piston, there is no change in microhardness between the piston material in the deformed area with the deformed piston material hardness, piston material made of alloy Al-Si. In the area of the piston surface that experiences deformation, Mg2Si and Mg2Al3 compounds are formed, these compounds which cause microcrack on the piston's upper surface. Plastic deformation on the piston surface occurs due to a collision between the piston surface and the cylinder head due to the buildup of crust on the piston surface.

Effect of fish scale texture on friction performance for reciprocating pair with high velocity

PurposeThis paper aims to study the frictional performance of reciprocating pair with high velocity by using hydrodynamic lubrication principle and fish scale textured piston model.Design/methodology/approachBased on the idea of function characteristic approximation and coordinate change, a mathematical representation model of imitating fish scale texture pit section is established. According to the principle of dynamic pressure lubrication of the textured fluid, a three-dimensional numerical model of flow field for fish scale texture is established without considering cavitation. Numerical analysis of the model carp scale texture unit by orthogonal experimental design and FLUENT software is carried out.FindingsEffects of fish scale pit texture on friction properties for a reciprocating pair piston surface with high velocity (impact piston) are acquired. Effects of texture characterization parameters and flow rate on the surface friction performance for impact piston are found. Effects of different characteristic parameters combination of imitating fish scale texture on friction performance for impact piston surface are obtained.Originality/valueThe model is an effective tool to study the friction and wear of reciprocating pair with high velocity. The effects of fish scale textured piston pair supply a theory lead to design the reciprocating pair with better friction performance.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2019-0398

Optimization of the effect of thermal barrier coating (TBC) on diesel engine performance by Taguchi method

In this study, thermal barrier layers were coated on piston and valve surfaces using plasma spray method. The effects of coated layers on torque, power and brake specific fuel consumption (BSFC) were investigated experimentally, and statistically using the Taguchi optimization method. Coating materials used in this study were Al2O3 + 13% TiO2, Cr2O3, and Cr2O3 + 25% Al2O3. Each coating material was tested at different speeds, which were 1400 rpm, 2000 rpm, 2600 rpm and 3200 rpm. The results showed that engine torque and BSFC reached their optimum values with the use of Al2O3 + 13% TiO2 at the speed of 2600 rpm. However, engine power showed the best performance with the same coating material but at the speed of 3200 rpm. The results of the experiment were also tested using Taguchi optimization method with coating material and engine speed parameters. The design of Taguchi analysis was carried out with L16 (42) orthogonal array. The highest S/N ratios of engine torque and BSFC were observed with the coating material of Al2O3 + 13% TiO2 at the speed of 2600 rpm. However, the highest S/N ratio of engine power was seen with the use of Al2O3 + 13% TiO2 at the speed of 3200 rpm. In order to determine the statistical significance of experimental parameters on engine torque and power and BSFC, ANOVA and F-test were carried out. The results of statistical analysis showed that the coating materials (P < 0.05) and engine speed (P < 0.05) parameters were statistically significant on the engine torque, power and BSFC.

Tribological study of piston–cylinder interface of radial piston pump in high-pressure common rail system considering surface topography effect

Based on the theory of thermal fluid dynamic lubrication, the Reynolds equation and energy equation of the average flow of a piston–cylinder interface of a radial piston pump in a high-pressure common rail system are established, considering the surface topography effect. The tribological properties of the piston–cylinder interface are calculated by solving the Reynolds equation and energy equation. A surface wear model is established and the wear distribution and trend of the piston–cylinder interface are studied. The wear characteristics of the piston–cylinder interface are verified through experiment, and the wear lubrication of the piston–cylinder interface is discussed. The surface topography effect has a considerable influence on the characteristics of the piston–cylinder interface film. Different surface morphologies change the film characteristics of the piston–cylinder interface, yielding different wear behaviors on the mating surface. The wear of the piston–cylinder interface first decreases along the film outlet to the inlet and then rises. The cylinder surface mainly exhibits abrasive, cavitation, and micro-convex scratch wear, whereas the piston surface mainly shows cavitation wear. The results obtained in this study are of considerable significance as they reveal the tribological properties of the piston–cylinder interface under the surface topography effect.

Friction and wear performance of bionic stripped piston of BW-160 slime pump

Bionic strips were designed and processed on the piston of BW-160 slime pump to improve its friction performance, decrease wear mass losses, and prolong service life. Nine stripped pistons were processed and manifested by different strip depths and included angles between stripes and piston surface. A workbench of slime pump piston was created to test the frictional force, oil film width, and wear mass losses. Test results demonstrated that the stripped structure can significantly decrease the frictional force on the piston. Optimal strip depth, included angle, and resistance reduction rates for stripped piston reached 2 mm, 90°, and 53.89%, respectively. The oil film on stripped piston was significantly wider compared with that of the standard piston, thus reducing frictional force between the piston and cylinder sleeve. The wear mass losses and the wear rate of the bionic piston are lower than that of the standard piston. Finally, the friction and stress of the piston are analyzed by finite element method, and the influencing mechanism on performance of pistons was discussed. The test results provide parameters for piston design of BW-160 slime pump for engineering.

Effect of grooved cylinder liner depths on the tribological performances of cylinder liner-piston ring

PurposeFrictions in cylinder liner-piston ring often cause an inevitable loss of energy loss in the diesel engine. This study aims at evaluating the effect of depths in the cylinder liner groove texture on friction, wear and sealing performances.Design/methodology/approachFive depths of groove texture cylinder liners (50, 100, 150, 200, 250 µm) were fabricated, and experiments were carried out using a special-purpose diesel engine tester. Comparative analyses of cylinder liner contact resistances, piston ring wear losses and surface appearances were conducted with respect to different surface textures and applied loads.FindingsUnder no-load conditions, the cylinder liner with a 100 deep thread groove can significantly improve sealing and optimize its lubrication performance. On the other hand, the sealing is highly correlated with the depth of groove and the load within the cylinder liner. Under loaded conditions, the thread groove has less effect on the sealing performance.Originality/valueThe findings can provide feasible basis for the tribological design and production of diesel engines.

Analysis of the interaction of Spray G and in-cylinder flow in two optical engines for late gasoline direct injection

An investigation of the interaction between the in-cylinder flow and the spray topology in two spray-guided direct injection optical engines is reported. The bulk flow field in the combustion chamber is characterized using particle image velocimetry. Geometrical parameters such as the axial penetration and the spray angle of the liquid spray are measured using Mie scatter imaging and/or diffuse back-illumination. The measured parameters are compared with data from a constant volume chamber available in the literature. For a late injection strategy, the so-called ECN Spray G standard condition, the mean values of the spray penetration do not seem to be significantly perturbed by the in-cylinder flow motion until the plumes approach the piston surface. However, spray probability maps reveal that cycle-to-cycle fluctuations of the spatial distribution of the liquid spray are affected by the magnitude of the in-cylinder flow. Particle image velocimetry during injection shows that the flow field in the vicinity of the spray plumes is heavily influenced by air entrainment, and that an upward flow in-between spray plumes develops. Consistent with previous research that demonstrated the importance of the latter flow structure for the prevention of spray collapse, it is found that increased in-cylinder flow magnitudes due to increased intake valve lifts or engine speeds enhance the spray-shape stability. Compared with cases without injection, the influence of the spray on the in-cylinder flow field is still noticeable approximately 2.5 ms after the start of injection.

Diagnosis of Liner Scuffing Fault of a Diesel Engine via Vibration and Acoustic Emission Analysis

Cylinder liner, piston rings, and piston are the key components which contribute to the overall performance and efficiency of the IC engines. Excessive temperature and pressure inside the combustion chamber, abrasive wear on the surfaces of liner and piston are major factors which degrade the performance and efficiency of the IC engines. The abnormal function of IC engine components causes an increase in sound and vibration levels of the engine structure and degrades the overall performance. The purpose of this work is to use signal processing techniques to extract fault-related information from sound and vibration signals of the IC engine. This work considers Fast Fourier transform and statistical feature extraction methods for monitoring the liner scuffing fault developed in the diesel engine. The performance, emissions, and cylinder pressure were also monitored to analyze the effect of liner scuffing fault. The results demonstrated that the aforementioned vibration signal analysis methods can be employed for the detection of liner scuffing fault in a diesel engine. The vibration and acoustic emission levels of the diesel engine were increased due to liner scuffing fault at all the loading conditions. The statistical feature parameters were increased at all the loading conditions due to the spurious effect of high-frequency amplitudes of vibration and acoustic signals. Furthermore, the performance parameters of the diesel engine were affected due to frictional losses caused due to liner scuffing fault.

Experimental determination of flame speed and flame stretch using an optically accessible, spark-ignition engine

The current research experimentally studied flame speed and stretch under engine in-cylinder conditions. A direct-injection, spark-ignition, and optically accessible engine was utilized to image the flame propagation, and E10 was selected as the fuel. Also, three fuel–air mixtures (stoichiometric, lean, and rich) were examined. The flame front was located by processing high-speed images. This study introduces a novel approach for calculation of equivalent spherical flame radius for analysis of flame speed and stretch. Flame front propagation analysis showed that during the flame propagation period, the stretch decreased until the flame front touched the piston surface. This was a common trend for stoichiometric, lean, and rich mixtures, which occurred because the flame radius was the dominant factor in the stretch calculation. In addition, the rich fuel–air mixture showed a lower flame stretch compared to stoichiometric or lean mixture. This was the result of a lower Markstein number for the rich fuel–air mixture. To study the sensitivity of different fuel–air mixtures to the flame stretch, the trajectory of the flame centroid was tracked until the flame front touched the piston surface. The results showed that the end centroid for the lean mixture deviated from the start point more than those of the rich and stoichiometric mixtures because the lean mixture had a higher flame stretch and lower flame speed. Furthermore, comparing the flame stretch at three different engine speeds revealed that increasing the engine speed increased the flame stretch, especially during the early flame development period. According to previous studies which discussed flame stretch as a flame extinguishment mechanism, the probability of flame extinction is higher when the engine speed is higher. Also, uncertainty analysis was conducted to determine the effect of camera setting on the flame stretch. Results showed that a maximum relative uncertainty of 4.5% occurred during the early flame development.

ПОВЫШЕНИЕ ЭНЕРГЕТИЧЕСКОЙ И ЭКОЛОГИЧЕСКОЙ ЭФФЕКТИВНОСТИ СИСТЕМ ГАЗООЧИСТКИ НА ТЭС

Актуальность исследования обусловлена необходимостью повышения энергетической и экологической эффективности систем очистки выбросов систем пылеприготовления и дымовых газов ТЭС при угольной генерации и систем подготовки газа при газовой генерации, во исполнение Федерального закона № 261-ФЗ от 23.11.2009 г. (ред. от 29.07.2017) «Об энергосбережении и о повышении энергетической эффективности и о внесении изменений в отдельные законодательные акты Российской Федерации», а также требований по контролю за выбросом парниковых газов (напр., приказа № 330 от 29.06.2017 года «Об утверждении методических указаний по количественному определению объёма косвенных энергетических выбросов парниковых газов» и др.) выбросов систем пылеприготовления и дымовых газов ТЭС с угольной генерацией и в системе подготовки газа с газовой генерацией. Цель: разработка устройства циклонной фильтрации для повышения эффективности систем газоочистки на ТЭС, снижения выбросов взвешенных частиц в атмосферу от систем пылеприготовления и дымовых газов при угольной генерации и увеличения надежности работы агрегатов газотурбинных и парогазовых установок ТЭС вследствие снижения износа рабочих поверхностей поршневых и винтовых дожимающих компрессоров дожимных компрессорных станций, предотвращения попадания продуктов внутренней коррозии газопроводов в газотурбинных установках, в соответствии с п.п. 93, 94 ФНиП в области промышленной безопасности «Правила безопасности сетей газораспределения и газопотребления» (Серия 12, вып. 13). Объект: модель циклона на базе ЦН-11-200, обеспечивающая повышение энергетической и экологической эффективности систем газоочистки на ТЭС. Методы: стендовые испытания циклонного фильтра, изготовленного путем модернизации циклона ЦН-11-200, аэродинамические расчёты; численное моделирование аэродинамических параметров работы циклона-фильтра на основе методов вычислительной гидродинамики. Для математического моделирования процесса сепарации использована система уравнений, состоящая из осредненных по Рейнольдсу уравнений движения однофазного потока Навье–Стокса и уравнения движения частиц, основанного на законе Ньютона. Для определения эффективности отделения взвешенной части потока в циклоне-фильтре использован безразмерный комплекс Rer, с помощью которого численные значения параметров осаждения взвеси из многофазного потока в сепараторе найдены расчетным путем. Результаты. Анализ литературных источников показал отсутствие конструкций циклонов-фильтров, которые обеспечивали бы надлежащую (более 98 %) степень очистки выбросов без резкого увеличения энергозатрат на обработку выбросов. Проведенные опыты показали целесообразность конструктивного дополнения возвратно-поточных циклонов фильтрующей вставкой в зоне, где происходит инерционное осаждение пыли. Для определения эффективности отделения взвешенной части потока в данном циклоне-фильтре был использован безразмерный комплекс Rer. Расчеты показали соответствие результатов теоретических и натурных исследований.

Effect of engine conditions and injection timing on piston-top fuel films for stratified direct-injection spark-ignition operation using E30

Mid-level ethanol/gasoline blends can provide knock resistance benefits for stoichiometric spark-ignition engine operation, but previous studies have identified challenges associated with spray impingement and wall wetting, leading to excessive particulate matter emissions. At the same time, stratified-charge spark-ignition operation can provide increased thermal efficiency, but care has to be exercised to avoid excessive in-cylinder soot formation. In support of the use of mid-level ethanol/gasoline blends in advanced spark-ignition engines, this study presents spray and fuel-film measurements in a direct-injection spark-ignition engine operated with a 30 vol.%/70 vol.% ethanol/gasoline blend (E30). Crank-angle resolved fuel-film measurements at the piston surface are conducted using two different implementations of the refractive index matching technique. A small-angle refractive index matching implementation allows quantification of the wetted area, while a large-angle refractive index matching implementation enables semi-quantitative measurements of fuel-film thickness and volume, in addition to fuel-film area. The fuel-film measurements show that both the amount of fuel deposited on the piston and the shape of the fuel-film patterns are strongly influenced by the injection timing, duration, intake pressure, and coolant temperature. For combinations of high in-cylinder gas density and long injection duration, merging of the individual spray plumes, commonly referred to as spray collapse, can cause a dramatic change to the shape and thickness of the wall fuel films. Overall, the study provides guidance to engine designers aiming at minimizing wall wetting through tailored combinations of injection timings and durations.