Diesel Cylinder Head Research Articles

Тепловая напряженность крышек цилиндров двигателей, конвертируемых в судовые

The article describes the characteristics of thermal loading of the cylinder covers of transport diesel engines during their conversion to marine diesels. The engines of the CHN14/14 type produced by the Yaroslavl Motor Plant are proposed as promising for use in marine power plants. A special feature of the engine design is the individual four-valve cylinder heads, which have a complex geometric shape. The conversion of automobile engines, the cylinder heads of which were made of aluminum alloys, to marine ones is accompanied by an increase in the degree of their acceleration. The cylinder heads in operation experience significant thermal and mechanical loads, which causes the need for increased requirements for the materials of the cylinder heads. The rational choice of the cylinder head material is one of the most important tasks to be solved when upgrading and boosting engines. Experience in the operation of marine diesel engines shows that in order to ensure the required reliability under prolonged exposure to elevated temperatures due to forcing, it is necessary to choose cast iron as a structural material. A three-dimensional model of the cylinder head is developed. When performing the calculations, the boundary conditions are justified, taking into account the local nature of the distribution of thermal and mechanical effects on the diesel cylinder head. As a result of numerical modeling, the stress-strain states of cylinder heads made of high-strength cast iron, ductile iron and cast iron with vermicular graphite are determined and analyzed. There has been proved the preference for using cast irons with vermicular graphite, which have satisfactory casting and physical and mechanical properties. The advantages of using cast iron with vermicular graphite include a decrease in the temperature of the cylinder head in the area of the inter-valve bridge. The possibility of increasing the engine power from 330 to 560 kW when replacing aluminum alloys with cast iron with vermicular graphite for the manufacture of cylinder heads is proved.

ПОВЫШЕНИЕ РЕСУРСА ГОЛОВОК ЦИЛИНДРОВ ДИЗЕЛЕЙ ПУТЕМ СОВЕРШЕНСТВОВАНИЯ ТЕХНОЛОГИИ ИХ ВОССТАНОВЛЕНИЯ

The article presents the results of studies of the thermal fatigue strength of diesel cylinder heads and their resource under operating conditions, by using the most advanced technology for their restoration. Based on the results of theoretical calculations of durability and operational studies, a restoration technology has been proposed, which makes it possible to increase the resource of cylinder heads by 2 ÷ 2.5 times. For this purpose, the non-uniformity of the temperature field on the firing bottom of the cylinder heads of YaMZ-238NB diesel engines was theoretically determined and experimentally confirmed. On the basis of theoretical calculations, the most heatstressed sections of the plane of the cylinder heads of diesel engines bonded to the cylinder block were determined, and the appearance of cracks in them. When developing a method for calculating the temperature fields of the fire bottom, the universal finite element method (FEM) was used. This method makes it possible to take into account the geometry and conditions of thermal loading of the cylinder heads quite accurately. For the determination of temperature fields, a well-founded assignment of the boundary conditions is crucial. With this in mind, a number of surfaces were determined that characterize the durability of the entire part during operation. As a result of calculations carried out on a computer, temperature fields have been obtained that make it possible to analyze the distribution of temperatures and temperature gradients at any point of the fire bottom. The highest temperatures (620...635K) are localized in the central part of the fire bottom, which is two times higher in thermal intensity than the peripheral one and confirms the appearance of cracks in these places during the operation of diesel cylinder heads.

Diesel engine combustion feature extraction based on time-frequency correlation

The use of diesel cylinder head vibration signal for fault diagnosis must eliminate signal interference non-periodic and random components. The periodic components related to the working cycle of the diesel engine are retained, so as to achieve the purpose of fault feature extraction. A time-frequency correlation-based diesel engine fault feature extraction method is proposed in this paper. First, the Wavelet transform is applied to the vibration signals of diesel engines collected in three continuous working cycles to realize the time-frequency distribution of the signals. Then three time-frequency distributions are estimated by cross-correlation, so as to eliminate noise interference and extract periodic transient characteristics. The experimental results of simulation signals and real signals show that this method can effectively extract the periodic transient impact characteristics of diesel engines.

THE ESTIMATION OF CARBON DEPOSIT INFLUENCE ON THE TEMPERATURE STATE OF THE MIDDLE SPEED DIESEL CYLINDER HEAD

Conception of cylinder head fractures origin in the locomotive diesels is expanded. The carbon deposit influence on the cylinder head temperature state is estimated. The nonuniform heat flux distribution is studied. Carbon layer presents on the fourstroke locomotive diesel cylinder head surface considering during its temperature state simulation is performed.

Fatigue Performance of Fluidized Bed Heat Treated 319 Alloy Diesel Cylinder Heads

Effects of various heat treatment tempers on fatigue performance of 319 alloy diesel cylinder heads were investigated. Castings were heat treated to T5, T6, and T7 tempers. Castings were solution heat treated and quenched using fluidized beds and aged using both conventional air convective furnace and fluidized bed for T6 and T7 tempers; while they were aged after casting for T5 temper using conventional furnace. Fatigue tests were performed at 373 K (100 °C) and stress ratio equal to −1. Results show that heat treatment has significant effect on the fatigue behavior of 319 alloy. The fatigue strength of T6 tempered 319 alloy is greater than T5 and T7 treatments. Weibull analysis shows that the Weibull modulus and characteristic fatigue life of castings treated (using conventional forced air circulation electrical resistance furnace) to T6 and T7 tempers are greater than T5 temper. This implies that castings treated to T6 and T7 tempers have greater reliability vis-a-vis T5 temper. Fractographic analyses reveal three distinct regions. These are: (I) crack initiation region from the surface, (II) crack propagation region, and (III) catastrophic or monotonic failure region. The relative size of the crack propagation region in T6 and T7 treated samples is greater than T5 treated samples. In general, the monotonic failure region shows typical dimple morphology, which implies significant plastic deformation prior to failure. Dimples on the fractured surface of T5 treated alloy are relatively more faceted than those treated to T6 and T7 tempers. This implies that the 319 alloy treated to T6 and T7 tempers underwent higher degree of plasticity prior to failure than that in the T5 condition.

Microstructure and Mechanical Properties of Heat-Treated B319 Alloy Diesel Cylinder Heads

Microstructure and mechanical properties of B319 alloy diesel cylinder heads were investigated in this study. Cylinder heads were heat treated to T5, T6, and T7 tempers using fluidized bed technology. Three different fluidized beds were used, each to solutionize, quench, and age the castings. For comparative purposes, castings were also aged using conventional forced-air circulation electric-resistance furnace. Effects of processing parameters such as temperature, time, and heating rate on microstructural evolution and mechanical properties namely tensile properties and hardness of B319 alloy castings were studied. The number density and size range of precipitates were measured. Results show that the T5 temper has no effect on eutectic phases such as Si- and Fe-rich intermetallic, and Al2Cu. On contrary, both T6 and T7 tempers result in spherodization of the eutectic Si and partial dissolution of the Al2Cu phase. Prolonged solution heat treatment for 8 hours in fluidized bed results in limited dissolution of the secondary eutectic Al2Cu phase. Aging (T6, T7, and T5) results in precipitation of Al5Cu2Mg8Si6 and Al2Cu phases in B319 alloy. The number density of precipitates in T6 temper is greater than in T7 and T5 tempers. The number density of precipitates is also affected by the duration of solution heat treatment. In general, long solution heat treatment (8 hours) results in greater precipitate density than short solution treatment (2 hours). The distribution of precipitates is inhomogeneous and varied across the dendritic structure. In general, precipitation rate of Al5Cu2Mg8Si6 phase is greater near the periphery of the dendrite as compared to the center. This is because Al5Cu2Mg8Si6 nucleates on Si particle, grain boundaries, and triple junction between recrystallized Al grains and Si particles. Similarly, heterogeneous sites such as grain boundaries and Al/Si interface also act as nucleating sites for the precipitation of Al2Cu phase. In general, the coarsening rate of precipitates near to the periphery of the dendrite is greater than in the center. This is because the Al matrix region close to the eutectic Si particles is subjected to in situ thermal stresses, which is generated due to the thermal mismatch between Al and Si particles. Thermal stress is highest at the Si/Al interface and decreases significantly away from the Al/Si interface. The precipitation and growth rate of the alloy aged in fluidized bed is greater than in conventional furnace. This is because heating rates of casting in fluidized bed (FB) are greater than conventional furnace, which result in greater precipitation rate. This study establishes a correlation between structure, thermal processing, and property of B319 alloy treated to various heat treatments. Reasonably good mechanical properties were obtained in less time using fluidized bed furnace. This work clearly demonstrates the significant potential of FB to save time and energy.

Diesel Engine Inlet and Exhaust System Fault Detection Based on PSO-BP NN

There is high failure rate in diesel engine inlet and exhaust system, so the inlet and exhaust system condition monitoring and fault diagnosis is of great significance.To overcome drawbacks of pure BP algorithm, a heuristic algorithm is adopted to give a transition from particle swarm search to gradient descending search to set up a Particle Swarm Optimized Back Propagation (PSO-BP) Neutral Network (NN). Then vibration signals have been measured from a diesel cylinder head by simulating two faults:the gas leak and abnormal lash; The diesel engine vibration frequency energy signals after wavelet packet decomposition are taken as the input feature vectors of NN. Finally, we carry out fault detection experiment by the PSO-BP NN model to validate the method. Experiment results show that the PSO-BP NN has more fast convergence speed and higher diagnosis accuracy than BP NN, and it provides a new fault detection method for engine inlet and exhaust system.

Analysis of strengthening local cooling on diesel cylinder head using nano-fluids with jet impingement technology

Analysis of strengthening local cooling on diesel cylinder head using nano-fluids with jet impingement technology

Development of a Structurally Optimized Heavy Duty Diesel Cylinder Head Design Capable of 250 Bar Peak Cylinder Pressure Operation

Development of a Structurally Optimized Heavy Duty Diesel Cylinder Head Design Capable of 250 Bar Peak Cylinder Pressure Operation

Thermomechanical fatigue of cast aluminium alloys for cylinder head applications–experimental characterization and life prediction

TMF loading in diesel cylinder heads made of cast aluminium alloys is expected to steadily become more severe in the future. This increasing loading condition will lead to an early crack initialization and eventually determine component life. Against this background several cast aluminium alloys have been studied with respect to their thermal and mechanical properties. In addition to standardized specimens, near component-shaped samples were tested under thermomechanical fatigue conditions in a testing device which represents near-service conditions, in order to characterize life until a long crack is formed. The sample geometry tries to represent the valve bridge of a diesel cylinder head, which is known to be the most thermomechanically loaded and hence critical part in this component. The results of the TMF tests with this new type of sample were compared with the results obtained on standardized specimens.The experimental results formed a sound basis to improve the thermomechanical life prediction methodology for cast aluminium alloys. Two different life prediction models were used to assess the TMF life of the near-component samples. Furthermore, an aging model for cast aluminium alloys was derived from the experimental results including the pronounced change of the mechanical properties which result from the combined effects of aging and cyclic plastic deformation. The comparison of the experimental and predicted results clearly shows that the new model leads to an improvement of the TMF life prediction.

Effect of Alloying Elements on Mechanical Properties for A356 Casting Alloy

A quantitative study of the interactions between microstructural features such as secondary dendrite arm spacing (DAS), eutectic structure and fatigue behavior of two Al-Si-Mg casting alloys with silicon contents of 7% and 10% respectively, has been conducted. In the condition of minimizing casting defects, the influence of microstructural features on the mechanical performance becomes more pronounced. Depending on the magnesium content affecting the strength of the matrix, the tensile properties were changed upon experimental conditions; the tensile strength was increased with magnesium content, whereas the elongation was increased in the reverse case. The increase of both of high cycle fatigue and low cycle fatigue lives with decreasing the secondary dendritic arm spacing is observed, mainly due to homogeneous deformation owing to the fine size of eutectic silicon and Fe intermetallic particles. The fatigue dynamometer of a diesel cylinder head shows the same tendency with the results of specimen fatigue tests with microstructures.

Holonic Approach for System Design of Reconfigurable Manufacturing Systems

The increasing global competition required the manufacturing enterprises to provide manufacturing systems with both high flexibility and high productivity functions. This is possible by using a new concept for creating of machine tools and systems namely the reconfigurable manufacturing systems (RMS). Intelligent Holonic approach is used to support the advanced hybrid system organization. The paper proposes and discusses new holonic reference architectures for reconfigurable manufacturing systems, which support the dynamically reconfiguration through a combination of the autonomy of reaction to disturbances with the co-operative tendencies found by centralized on-line scheduling holon. The suggested reference model is used to design a prototype of reconfigurable manufacturing system for processing of automotive diesel cylinder heads

Cracking in Cast Iron Diesel Engine Cylinder Heads

The nature and mechanism of cracking in cast iron diesel cylinder heads arising from the differential thermal strains which occur in service are reviewed. The results of experimental work with test apparatus simulating the conditions in a cylinder head are presented, illustrating the importance of controlling the boiling conditions of the water at the cooling face of the flame deck. It is concluded that cylinder head temperatures, and therefore the danger of cracking, can be successfully reduced by increasing the flow of cooling water over critical areas by some form of directed flow.