Cylinder Wall Research Articles

Impacts of diesel injection timing and syngas fuel composition in a heavy-duty RCCI engine

This research aimed to assess the impacts of Diesel Direct Injection Timing (DDIT) [−6 to −16 Crank Angle (CA) After Top Dead Center (ATDC) with 2 CA steps], syngas to diesel energy ratio [0 (Pure Diesel Combustion (PDC)), 20% (DSC20), and 40% (DSC40) of total fuel energy per cycle], and syngas fuel composition [H2 to CO volumetric ratio of 75%-25% (R = 3), 50%-50% (R = 1), and 25%-75% (R = 0.33)] in a heavy-duty RCCI engine. The numerical findings revealed that increasing syngas energy ratio to 40% at DDIT of −10 CA ATDC and R of 1 is an effective strategy to reduce NOx, PM, HC, and CO2 emissions by about 12%, 88%. 82%, and 40.36% versus the baseline PDC case, respectively. Regarding engine performance, by advancing the DDIT from −6 to −16 CA ATDC under all engine operating conditions, Gross Indicated Efficiency (GIE) enhanced by about 2.76%, 1.93%, and 1.34%, respectively, in comparison to the baseline PDC, DSC20, and DSC40 cases. Besides, at DSC40 conditions, exhaust gas loss was improved by nearly 4.74% but combustion loss and heat transfer loss were increased by 2% and 3.4%, respectively, compared to the baseline PDC operating mode. Also, increasing syngas energy ratio to 40%, R to 3, and diesel injection at −16 CA ATDC led to about 15.9% and 41% reduction of HC and CO emissions, respectively, compared to the baseline DSC40 case. In addition, under diesel-syngas combustion conditions, regions near cylinder walls and the center of the piston bowl are the main sources of unburnt syngas emission.

Performance investigation and evaluation of an engine operating on a modified dual cycle

In this study, a novel high-performance engine cycle composed of 5 processes and including constant temperature process has been developed by using novel numerical methods and compared with the classical dual cycle. The results of the classical thermodynamic model demonstrated that the proposed cycle which has a constant temperature process is better in terms of thermal efficiency and dimensionless net work compared to the classical dual cycle. After the validation of superiority of the developed cycle over the classical dual cycle, performance investigations of the novel cycle engine have been carried out in terms of power, power density, destructed exergy, thermal efficiency, ecological coefficient of performance, effective ecological power density by developing a novel fuel-air cycle model. The influences of design and operational parameters such as cut-off ratio, compression ratio, cycle temperature ratio, equivalence ratio, engine speed, stroke length, cylinder bore, cylinder wall temperature, air intake temperature, pressure ratio, on the performance specifications have been numerically derived.

ECN Spray D visualization of the spray interaction with a transparent wall under engine-like conditions, Part II: Impinging spray combustion

In spite of the ever more comprehensive studies on diesel combustion, there is still an important gap on the fundamental knowledge about the interaction of fuel sprays with the piston and cylinder walls in internal combustion engines. The present research corresponds to the second part of an extensive investigation about the spray/wall impingement process at engine-like conditions and its sensitivity to several operating conditions. A constant pressure-flow test rig, which was filled with air extracted from the environment, was employed to perform the experiments at reactive conditions. A single-hole injector from the Engine Combustion Network, referred to as Spray D was employed and a quartz flat wall was set in front of the nozzle by using a supporting structure attached to the vessel. Parameters varied in this work are injected fuel, ambient density, gas temperature, injection pressure, and wall position in terms of distance from the injector hole and inclination angle. Three cameras were simultaneously used to observe the spray–wall interaction (SWI): Schlieren visualization to record the macroscopic evolution of the spray vapor phase and also to determine the ignition delay, a high-speed camera was placed in the front of the wall to directly observe the natural luminosity of the flame through the transparent wall and, finally an intensified camera was used to determine the lift-off length by observing the chemiluminescence of OH*. An extensive geometrical characterization of the spray geometry evolution was made and different metrics were introduced in this work as it is the case of wall lift-off radius to parametrize the observed formation of a lift-off area onto the wall. Similarly, ignition delay showed to be shortened by the presence of the quartz wall up to 15%due to its nearly isothermal configuration and its improvement on air–fuel mixing.

Optimization of structure matrix of mold forms

Purpose. Optimization of the method of design and calculation of the composite matrices of molds for the manufacture of products from powder materials.
 Research methods. Analysis of stresses in the walls of solid and composite thick-walled cylinders and their existing calculations.
 Results. The peculiarities of stress formation in the wall of solid and composite thick-walled cylinders under the action of internal pressure are investigated. The possibility of applying the obtained results to determine the strength and stiffness of the wall of the mold for the manufacture of products from powder materials is analyzed. Limitations in ensuring the strength of the matrix by only increasing its thickness are determined. It is shown that the use of a matrix composed of an inner cylinder and an outer holder allows to use optimal stress redistribution in the walls of such matrix in order to reduce the size and, accordingly, save materials for its manufacture. The possibility of using various, better adapted materials for the manufacture of the inner wall of the matrix and permiting the reduction of the cost of manufacturing the mold are analyzed.
 The method of calculation of stresses in dangerous points of walls of a matrix at an estimation of their strength and stiffness is generalized. Formulas for determination of the guaranteed tension which will provide effective redistribution of stresses in walls of the composite matrix under the set operating conditions are given.
 Scientific novelty. Approaches to the analysis of stresses in the walls of composite matrices of molds under the influence of internal pressure are optimized and generalized . Mathematical dependences are given, which make it possible to determine the optimal dimensions of mold elements at action of pressing pressure.
 Practical value. The principles of design and methods of calculation of composite matrices of molds for the manufacture of products from powder materials are proposed.

Applied Systems Theory: Mathematical and Numerical Simulation of Strength of Thick-wall Pipe by Using Static Elastic Problems

In Systems Theory, the Mathematical and numerical simulation of strength of thick-wall pipe by using static elastic problems is an important problem and has attracted the attention of many researches, academicians and practitioners. the The present work studies the change in the strength of a quite long isotropic thick-wall pipe (circular cylinder) for the varying pipe diameter, wall thickness and material. The pipe is in the plane deformed state, i.e. plane deformation is considered. Based on the problems of statics of the theory of elasticity, a mathematical model to calculate the strength of the thick-wall pipe was developed and the problems of statics of the theory of elasticity were set and solved analytically in the polar coordinate system. The analytical solution was obtained by the method of separation of variables, which is presented by two harmonious functions. The dependence of the pipe strength on the thickness and material of the pipe wall, when (a) normal stress is applied to the internal boundary (internal pressure) and external boundary is free from stresses and (b) normal stress is applied to the external boundary (external pressure) and the internal boundary is free from stresses, is studied. In particular, the minimum thicknesses of the walls of homogeneous isotropic circular cylinders of different materials and diameters with a plane deformed mode when the pressures in the cylinders do not exceed the admissible values were identified. Some numerical results are presented as tables, graphs and relevant consideration.

Effect of natural gas energy fractions on combustion performance and emission characteristics in an optical CI engine fueled with natural gas/diesel dual-fuel

Natural gas/diesel dual-fuel combustion is one of the most promising low-temperature combustion strategies. However, unstable combustion processes under low engine loads restrain the development of this strategy. To overcome this problem, a visualization technique and numerical simulations were used at low engine load conditions to investigate herein how the natural gas energy fraction (NGEF) coupled with split injection affects flame development, performance, and the emission characteristics of natural gas/diesel dual-fuel engines. The results reveal that increasing the NGEF retards the start of combustion and decreases the peak pressure. The NGEF significantly affects the distribution of the ignition kernel, with a higher NGEF scattering the ignition kernel. Combustion first occurs in regions of richer mixture near the cylinder wall and then propagates towards the interior. The amount of methane produced by diesel fuel through NC7H16 → C7H15-2 → PC4H9 → C2H4 → CH4 is relatively small compared with natural gas. Unburned methane is detected near the central axis of the cylinder, which is mainly due to the limited coverage of the flame. The lower soot volume fraction and unburned hydrocarbon emissions can be obtained by increasing the NGEF from 0% to 70%, whereas further increasing the NGEF to 85% deteriorates combustion.

Dynamic modelling and experimental validation of Coupled Vane Compressor

The newly developed Coupled Vane Compressor (CVC) consists of a unique feature that is a couple of vanes cut through the rotor diametrically. Theoretically, this allows the rotor of any diameter which can accommodate the coupled vanes, to be able to operate CVC. Thus, unlike other rotary compressors, CVC design is mostly free of geometrical constraints imposed on the size of its rotor, making it one of the most compact compressors. Nevertheless, CVC suffers from frictional losses similar to other rotary compressors and therefore, studies of dynamic forces acting in CVC is of great interest. In this paper, dynamic forces acting on its components and frictional losses occurring due to rubbing of various components were studied and analysed. Unlike in other vane compressors, in which frictional losses are mostly due to the rubbing of vane tips against cylinder wall and vane sides against vane slot in the rotor, in CVC, the loss also occurs due to rubbing between the coupled vanes. A CVC prototype of 44 cm3 was developed and the compressor power consumption was experimentally studied in an open-type test circuit using air as an operating fluid. The predicted and measured power consumed by CVC were compared and the predicted results were found to have maximum discrepancy of ±15% with the measured results.

Development of a wall jet model dedicated to 1D combustion modelling for CI engines

Diesel engines are becoming smaller as technology advances, which means that the fuel spray (or jet) interacts with the cylinder walls before combustion starts. Most fuel injection 1D models (especially for diesel fuel) do not consider this interaction. Therefore, a wall-jet sub-model was created on an Eulerian 1D diesel spray model. It was calibrated using data from the literature and validated with experimental data from a fuel spray impacting a plate in a constant volume combustion chamber. Results show that the spray moving along the wall has a higher mixing rate but less penetration as an equivalent free jet, therefore they show a similar volume. Spray-wall interaction creates a stagnation zone right before the impact with the wall, and friction of the jet with the wall is relatively low. All these phenomena are well captured by the wall-jet sub-model.

Two-dimensional unsteady inertial flows of a yield stress fluid around a cylinder

• Without slip at the wall, alternate vortex shedding occurs behind the cylinder • With slip at the wall, double shedding occurs behind the cylinder. • Good correlation between the numerical predictions and experimental results. • Vortex frequency decreases as yield stress increases or inertia decreases • Viscoelastic effects are slight. Two-dimensional unsteady inertial flows of a yield stress fluid around a cylinder were studied experimentally. Carbopol aqueous gels, well-known model yield stress fluids, are used. The influence of interface conditions on vortex shedding was studied in particular by modifying the roughness of the cylinder. When wall adherence was guaranteed, it was possible to observe alternate vortex shedding similar to the Von Karman street occurring in Newtonian fluids. In contrast, when the fluid was able to slip on the cylinder wall, a highly particular flow morphology was observed. The effects of the Reynolds and Oldroyd numbers and that of confinement on the critical Reynolds number for vortex shedding and on the Strouhal number were demonstrated. The experimental results were compared with the numerical predictions using a Herschel-Bulkley viscoplastic model.

MHD Double Diffusive Convection of Al2O3-Water Nanofluid in A Porous Medium Filled an Annular Space Inside Two Vertical Concentric Cylinders with Discrete Heat Flux

The magnetoconvection phenomenon of a double diffusive free convection in an annular porous space inside two concentric cylinders saturated by a (Al2O3, water) nanofluid has been investigated in the current study. The transport equations for vorticity, energy and concentration as well as stream function are solved using the finite difference method. At lower temperatures and concentrations, the outer cylinder is sustained, the discrete heat flux with the unheated adiabatic portions as well as the higher concentrations are imposed in the inside walls of the central cylinder. The base walls are insulated and impermeable. In the vertical direction, external magnetic field (MF) with uniform intensity is applied. The results of the obtained numerical simulation are presented to exhibit the consequences of various numbers such: Rayleigh RaTh, Hartmann Ha, Buoyancy forces ratio N and the solid nanoparticles (NPs) volume fraction  on the pattern of the nanofluid flow and the transferred mass and thermal energy in the active wall. It is noted that the transferred mass and thermal flux in the active wall augments as the RaTh and N augments. The thermal energy transferred augments with the growth of , while the transferred mass in the active wall decreases. The greater magnetism declines the rate of the mass and thermal energy transport in the active wall.

Nozzle configuration and in-cylinder pressure effects on fuel spray behaviour: studies using a rapid cycling machine

Efforts to improve the efficiency of internal combustion engines in applications such as heavy-duty vehicles where electric propulsion is currently unfeasible or need complementing are essential. However, studying the conditions of actual internal combustion engines whilst accessing their combustion chambers whilst they are in operation remains difficult. To allow for the characterization of practical operating conditions of diesel engine designs, detailed studies examining the influence of the injector nozzle configuration, peak in-cylinder pressure conditions, and fuel injection pressure values up to 25% greater than those hitherto typically reported using rapid cycling machines for diesel spray diagnosis were carried out. A rapid cycling machine using a production diesel engine piston design, equipped with optical windows and fitted with a high-pressure common rail fuel injection equipment was used with temporal spray liquid and vapour penetration values obtained using Schlieren and Mie scattering imaging techniques for injector nozzles of various k-factor values. Even though the effects of the different injector nozzle conicity values on the fuel spray liquid and vapour penetration values observed were not significant, the studies supported the use of such methods to evaluate the piston and cylinder wall wetting which can have significant effects on the emissions and fuel consumption from internal combustion engines. These are also useful for internal combustion engine design and numerical spray code development.

Effect of hydrogen direct injection strategies and ignition timing on hydrogen diffusion, energy distributions and NOx emissions from an opposed rotary piston engine

Opposed rotary piston (ORP) engines as a new type of internal combustion engines are free of connecting-rod mechanisms, have small engine size and mass. ORP engines have the abilities of delivering high power density. Hydrogen fuel applications in internal combustion engines contribute to nearly zero carbon emissions in the combustion processes. In this paper, the effect of hydrogen direct injection strategies and ignition timing on hydrogen diffusion, in-cylinder combustion, energy distributions, and nitric oxide (NOx) emissions are investigated using a numerical simulation method regarding this novel internal combustion engine. The results showed that hydrogen was the most unevenly distributed in the combustion chambers for the start of injection (SoI) of −68.2° crank angle (CA) after top dead centre (aTDC) among the three hydrogen injection strategies; meantime, it presented the lowest combustion efficiency, being smaller than 98.5%. The peak in-cylinder pressure ranged from 40 bar to 83 bar for the given scenarios. The combustion durations were in the range of 20 °CA ~ 30 °CA for the ignition timing of −20.85 °CA aTDC ~ −11.06 °CA aTDC. The indicated thermal efficiency was higher than 38% over early ignition cases; the energy losses in total fuel energy by cylinder walls were lower than 15%. NOx emissions factors were lower than 36 g/kWh, and they were reduced by the retarded hydrogen injection. The engine performance and NOx emissions under early hydrogen injection scenarios are less sensitive to late ignition; additionally, the crank angle corresponding to the optimal efficiency was almost the same under different hydrogen injection strategies.

A quasi-isentropic model of a cylinder driven by aluminized explosives based on characteristic line analysis

A quasi-isentropic study on the process of driving a cylinder with aluminized explosives was carried out to examine the influence of the aluminum (Al) reaction rate on cylinder expansion and the physical parameters of the detonation products. Based on the proposed quasi-isentropic hypothesis and relevant isentropic theories, the characteristic lines of aluminized explosives driving a cylinder were analyzed, and a quasi-isentropic model was established. This model includes the variation of the cylinder wall velocity and the physical parameters of the detonation products with the Al reaction degree. Using previously reported experimental results, the quasi-isentropic model was verified to be applicative and accurate. This model was used to calculate the physical parameters for cylinder experiments with aluminized cyclotrimethylenetrinitramine explosives with 15.0 % and 30.0 % Al content. The results show that this quasi-isentropic model can be used not only to calculate the cylinder expansion rule or Al reaction degree, but also to calculate the physical parameters of the detonation products in the process of cylinder expansion. For explosives with 15.0 % and 30.0 % Al, 24.3 % and 18.5 % of the Al was found to have reacted at 33.9 μs and 34.0 μs, respectively. The difference in Al content results in different reaction intensity, occurrence time, and duration of two forms of reaction (diffusion and kinetic) between the Al powder and the detonation products; the post-detonation burning reaction between the Al powder and the detonation products prolongs the positive pressure action time, resulting in a continuous rise in temperature after detonation.

Prediction of oil dilution formation rate due to post injections in diesel engines by using Gaussian process

Post-injection strategies are commonly used in diesel engines for various purposes, such as cleaning diesel particulate filters from soot, heat-up and heat maintenance strategies. Usage of post injections in diesel engines with upcoming legislation is expected to be increased because of increasing regeneration frequencies, de-sulfation of catalysts and challenges in cold emission. Post injections with retarded timing and high quantity under certain charge conditions can cause oil dilution by creating liquid fuel impingement on lubricated cylinder walls and the fuel absorption into the oil film. Fuel contamination to engine oil can cause deterioration in oil properties. Engine components can only bear a certain level of degradation in oil properties. Thus, exceeding a certain level of oil dilution should be avoided not to harm engine durability. The engine oil must be replaced within a specific interval due to various mechanisms affecting engine oil lubrication performance such as ageing, soot content etc. Depending on the fuel rate going into the engine oil, oil dilution due to post injections can limit engine oil change intervals. Engine oil change interval is essential for the cost of ownership and environment. Parameters such as charge conditions at post-injection timing and post-injection configuration are effective over the formation rate of oil dilution due to post injections. Therefore, the formation rate of oil dilution due to post injections must be minimized and modelled not to exceed a specific limit in different cycles. With this study, a series of engine testing is conducted to investigate the correlation between empirical spray parameters and fuel in oil formation rate due to post injections. During the studies, various charge conditions and post-injection configurations were tested. In addition to fuel addition to oil, fuel evaporation from oil was also investigated. A correlation between penetration depth and the formation rate of oil dilution was observed. However, a correlation between Sauter means diameter and formation rate of oil dilution was only kept when penetration depth was filtered within a specific range in test results. Evaporation of fuel in oil has shown an asymptotic behaviour based on test duration and initial heavy fraction ratio under constant oil temperature conditions. A statistical modelling approach is applied to predict the formation rate of oil dilution as a function of normalized spray penetration depth, Sauter means diameter and engine speed. Moreover, such a model was validated over various transient cycles.

Distribution of fluid flow pressure through tandem square cylinders with the addition of triangular cylinder as a disturbance object

Flow across a square cylinder in a tandem arrangement is a shape characterization that is often used in structural engineering, transportation, and heat exchangers, where wind and water loads are one of the main factors that need to be considered in the design because they are associated with loss of energy. This is a problem faced by various industries in increasing the efficiency and stability of their systems. To reduce this energy loss, flow modification can be carried out in the form of adding disturbance objects that are placed in the front area of the main object, so that the fluid flow can pass through the object without any flow separation and produce a uniform flow after passing through the object. The research objective is focused on analyzing the effect of adding a triangular cylinder as a disturbance object to the characteristics of the flow pattern and the pressure distribution on the walls of the square cylinder in a tandem arrangement. This research used numerical computation methods and was validated through experimental testing at an upstream velocity of 19 m/s. The hydraulic diameter of the disturbance object was determined to be 0.033 m and the distance ratios M/D were 0.05, 0.15, 0.25, 0.35, 0.45, and 0.55, respectively. The results showed that the application of a triangular cylinder as a disturbance object had an effect on the characteristics of the flow pattern and the pressure coefficient, where the lowest pressure coefficient on the front side and the highest pressure coefficient on the side and rear sides were obtained in a model with a distance ratio M/D = 0.45.

A Compendium of Methods for Determining the Exergy Balance Terms Applied to Reciprocating Internal Combustion Engines

Abstract Exergy analysis of the reciprocating internal combustion (IC) engines is studied by estimating various input and output energy transfer parameters concerning a dead state reference. Exergy terms such as fuel input, work output, cooling, and exhaust gas are measured and are set into the exergy balance equation to determine the amount of loss or destruction. Exergy destructions are found in many forms such as combustion (entropy generation), cylinder wall, friction, mixing, blow-by, and others. These exergy terms have been estimated by considering various factors such as engine type, fuel type, environmental condition, and others. In this article, the different methods employed in estimating these exergy terms have been reviewed. It attempts to make a compendium of these evaluation methods and segregates them under individual exergy terms with necessary descriptions. The fuel input measurement is mostly based on Gibb's free energy and the lower heating value, whereas its higher heating value is used during the fuel exergy calculation on a molar basis. The work output of the engines is estimated either from the crankshaft or by analyzing the cylinder pressure and volume. The exergy transfer with cooling medium and exhaust gas depends on the temperature of the gas. The maximum achievable engine performance is quantified by estimating the exergy efficiency. This piece of study will not only provide plenty of information on exergy evaluation methods of IC engines but will also allow future researchers to adopt the appropriate one.

MODELING OF OPERATING MODES GAS COMPOSITE CYLINDERS

Statement of the problem. The emergence of composite cylinders on the market offers a range of technological and operational advantages in comparison with metal cylinders of liquefied hydrocarbon gas. At the same time, the absence of substantiated recommendations for determining the vapor capacity of cylinders by modes of their operation in the scientific literature limits their wide implementation into gas practice. Results. A mathematical model considering the operation of the cylinder in the mode of periodic gas consumption is developed, the coefficient of non-uniformity of gas consumption during the day is calculated, the values of the heat transfer coefficient of the composite cylinder wall are identified, the approximate dependence of the heat transfer coefficient is obtained. Conclusions. As a result of the research, the criteria influencing steam productivity of compositecylinders of the liquefied hydrocarbon gas in various operating modes are found.

Modeling and FEM simulation of a pressurized and rotated functionally graded thick walled cylinder

ABSTRACT The present study investigates the effect of material inhomogeneity on thick cylinders under rotation with uniformly applied internal and external pressure. In line with that, a finite element method (FEM)-based simulation is performed for the elastic analysis of thick cylinders made of functionally graded materials (FGMs). The property of FGMs is assumed in an exponential functional form of radial position with a constant Poisson’s ratio. Stress distributions along the radial and circumferential directions are studied, considering the stress in an axial direction to be zero. The results show that the property of FGMs has a significant influence on stress distributions by reducing the overall radial stress and completely changing the distribution of circumferential stress compared to an isotropic cylinder under the same load. Thus, the use of exclusively designed FGMs for manufacturing parts can increase their pressure handling capacity and improve their functionality.

Thermo-elasto-plastic analysis of thick-walled cylinder made of functionally graded materials using successive approximation method

In this paper, the thermo-elasto-plastic behavior of a thick walled cylindrical shell made of a Functionally Graded Material (FGM) is analyzed by Successive Approximation Method (SAM). The FGM ingredients include Aluminum and Silicon Carbide in which the effective material properties are estimated using the Modified Rule of Mixture. The shell is subjected to a combination of internal pressure and temperature gradient. After application of equilibrium equations for derivation of governing equations, the Differential Quadrature Method (DQM) is used for numerical solution. It is assumed that the two ends of the cylinder are closed and the plane strain conditions are established. The distribution of elastoplastic stresses and strains along the cylinder's thickness is presented in terms of characteristics of material composition and thermo-mechanical loadings such as volume fraction, in-homogeneous index, internal pressure and thermal loadings. Trueness and accuracy of the present problem is justified through comparison with available results in literature. The results show that by enhancement of ceramic particles percentage in the outer layers of cylinder's wall, amount of plastic strains is reduced at that layers, but at the same time, the amount of plastic strains and range of plastic region, increases at inner layers of thickness.

Influences of FOX-7 and NTO on the metal driven ability and underwater explosion power of HMX-based aluminized explosives

In order to investigate the metal driven abilities of two newly HMX-based aluminized explosives (XL: 31% HMX, 31% FOX7, 30% Al, 8% binder; EL: 31% HMX, 31% NTO, 30% Al, 8% binder), multiple cylinder tests were conducted to gain the cylinder wall expansion process and evaluate Gurney energy. Then the parameters of JWL-Miller equation of state were determined based on experimental expansion data. For evaluating the underwater explosion power of XL and EL, we numerically simulated the propagation of shock wave and bubble pulsation under water. The experimental and modeling results showed that the metal driven ability and underwater explosion overpressures of XL were obvious better than EL, but the specific bubble energy of XL was only about 3% higher than EL. Compared with NTO, FOX-7 better improve metal driven capacity, underwater explosion power and secondary combustion rate of aluminized explosives. Those conclusions may provide useful suggestions for designing HMX-based insensitive aluminized explosives.