Cylinder Head Research Articles

A novel method to investigate the power generation characteristics of linear generator in full frequency operation range applied to opposed-piston free-piston engine generator _ Simulation and test results

The opposed-piston free piston engine generator (FPEG) has unique advantages because of its symmetrical structure and the cancellation of cylinder head. In this paper, a novel method which combines low frequency operation test with high frequency operation simulation is proposed to study the generation performance of linear generator in the full frequency operation range. The influences of operation frequency, stroke, power angle and load current on the generation performance of linear generator are analyzed. The results show that the resistive load can not efficiently absorb the electric energy generated by the linear machine, the system shows a small increase in power generation efficiency at high operation frequency, but exhibits a rapid upward trend in low-speed condition. When the generator operates under the rated condition of the opposed-piston FPEG, the generating power can reach 5 kW, and the generating efficiency is higher than 80%. Increasing the operation frequency can further improve the generating power of the generator due to the increasing energy input.

Optimization of Machining Cycle Time for Cylinder Head Cover

Optimization of Machining Cycle Time for Cylinder Head Cover

New Insights into Abnormal Combustion Phenomena Induced by Diesel Spray-Wall Impingement under Engine-Relevant Conditions

High altitude and low temperature is the common extreme environment for internal combustion engines. Under such operating conditions, heavy-duty diesel engines often suffer from serious abnormal combustion, such as knocking combustion, which results in piston crown breakdown and cylinder head erosion. Spray-wall impingement and pool fires are considered potential causes; however, the detailed mechanism remains poorly understood owing to the lack of research data. In this study, for the first time, the destructive abnormal combustion induced by diesel spray-wall impingement was identified using an optical rapid compression machine under engine-relevant conditions at high altitudes. Combining instantaneous pressure and temperature measurements with simultaneously recorded high-speed photography gives useful insights into understanding the detailed combustion processes. The experimental results show that depending on the extent of diesel spray-wall impingement, supersonic detonation-like reaction fronts featuring bright luminosity can be observed. The propagation of these reaction fronts in-cylinder results in severe pressure oscillations with an amplitude approaching hundreds of atmospheres, which is like the super-knock events in boosted direct-injection spark-ignition engines. Further parametric analysis indicates that the interplay between the diffusion combustion controlled by diesel spray and the premixed combustion dominated by attached film evaporation results in the formation of abnormal combustion. Destructive reaction fronts tend to occur at a prolonged ignition delay time, which facilitates the mixing between diesel evaporation and hot air.

Mathematical Model for Field Data Based for Productivity Enhancement of Cylinder Head Moulding Operation

Abstract The paper illustrates with an approach for formulation of generalized field data based model for cylinder head moulding operation. The aim of field data based modeling for cylinder head moulding operation is to evaluate variable responsible for productivity enhancement & with minimum human energy expenditure. The study identifies important ergonomic and other work environment related parameters which affect the productivity. The identified parameters are properties of sand, physical dimensions of tools, energy outflow of workers, workers anthropometric data, working environment. Out of all the variables responses and causes are identified. After dimensional analysis relationship between the dependent and independent parameters, a mathematical model is established having relationship between output parameters and input. To get the optimized values model is optimized using the optimization technique. Sensitivity analysis is a tool which can be used to find out the effect of input one parameter over the other. The model will be useful for an industrialist to select optimized inputs so as to get targeted responses.

Vibration-based identification of engine valve clearance using a convolutional neural network

Contemporary operation-related requirements for combustion engines force the necessity of ongoing assessment of their in operation technical condition (e.g. marine engines). The engine efficiency and durability depend on a variety of parameters. One of them is valve clearance. As has been proven in the paper, the assessment of the valve clearance can be based on vibration signals, which is not a problem in terms of signal measurement and processing and is not invasive into the engine structure. The authors described the experimental research aiming at providing information necessary to develop and validate the proposed method. Active experiments were used with the task of valve clearance and registration of vibrations using a three-axis transducer placed on the engine cylinder head. The tests were carried out during various operating conditions of the engine set by 5 rotational speeds and 5 load conditions. In order to extract the training examples, fragments of the signal related to the closing of individual valves were divided into 11 shorter portions. From each of them, an effective value of the signal was determined. Obtained total 32054 training vectors for each valve related to 4 classes of valve clearance including very sensitive clearance above 0.8 mm associat-ed with high dynamic interactions in cylinder head. In the paper, the authors propose to use a convolutional network CNN to assess the correct engine valve clearance. The obtained results were compared with other methods of machine learning (pattern recognition network, random forest). Finally, using CNN the valve clearance class identification error was less than 1% for the intake valve and less than 3.5% for the exhaust valve. Developed method replaces the existing standard methods based on FFT and STFT combined with regression calculation where approximation error is up to 10%. Such results are more useful for further studies related not only to classification, but also to the prediction of the valve clearance condition in real engine operations.

FEA Analysis and Experimental Investigation of the Ceramic Coating on Aluminum Piston Material By Plasma Spray Coating Technique

Abstract: Functionally graded materials are of widespread interest because of their superior properties such as corrosion, erosion and oxidation resistance, high hardness, chemical and thermal stability at cryogenic and high temperatures. These properties make them useful for many applications, including Thermal Barrier Coating (TBC) on metallic substrates used at high temperatures in the fields of aircraft and aerospace, especially for thermal protection of components in gas turbines and diesel engines. The application of TBC reduces the heat loss to the engine cooling-jacket through the surface exposed to the heat transfer such as the cylinder head, liner, piston crown and piston rings. The insulation of the combustion chamber with ceramic coating affects the combustion process and, hence, the performance and exhaust emissions characteristics of the engines improve. In this project, the main emphasis is placed on the study of thermal behavior of functionally graded coatings obtained by means of using a commercial code, ANSYS on aluminum and steel piston surfaces and the results are verified with numerical and experimental works. Keywords: Thermal Barrier Coating, Piston, Insulation, Corrosion, ANSYS, engine cooling-jacket.

A Simulation Tool for Calculation of Engine Thermal Boundary Conditions

<div class="section abstract"><div class="htmlview paragraph">Reducing emissions and the carbon footprint of our society have become imperatives requiring the automotive industry to adapt and develop technologies to strive for a cleaner sustainable transport system and for sustainable economic prosperity. Electrified hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and range extender powertrains provide potential solutions for reducing emissions, but they present challenges in terms of thermal management. A key requirement for meeting these challenges is accurately to predict the thermal loading and temperatures of an internal combustion engine (ICE) quickly under multiple full-load and part-load conditions.</div><div class="htmlview paragraph">Computational Fluid Dynamics (CFD) and thermal survey database methods are used to derive thermal loading of the engine structure and are well understood but typically only used at full-load conditions. These methods are limited in terms of computational overhead with CFD and the validity of the database when wishing to look at part-load conditions to build up a thermal map of the engine for transient solutions.</div><div class="htmlview paragraph">This paper presents a new analytical Finite Element (FE) based tool for calculating thermal boundary conditions of all the components of the power cylinder using physical models and semi-empirical correlations, without the need for CFD analysis, and which overcomes the limitation of database methods which are not predictive. An iterative solution is used that captures all the heat paths in detail and where each solution runs quickly enough to allow different design variants to be assessed for multiple operating conditions. The calculated temperatures and the corresponding deformations can then be used to predict piston secondary motion and ring dynamics and to better predict friction, wear and oil consumption of the power cylinder and the structural durability of the components.</div><div class="htmlview paragraph">The toolset is applied to a 2.0 liter 4-cylinder Gasoline Turbocharged Direct Injection (GTDI) engine and validated with measurements on the piston, cylinder head and cylinder bore for different full and part-load conditions.</div></div>

An Experimental Study of In-Cylinder Heat Transfer from a Pressurized Motored Engine with Varying Peak Bulk Gas Temperatures

<div class="section abstract"><div class="htmlview paragraph">The variation of in-cylinder heat transfer with parameters such as engine speed, air-to-fuel ratio, coolant temperature and compression ratio were frequently studied in classical research. These experimentally-obtained relationships are important for improving in-cylinder heat transfer models, essential in developing CO<sub>2</sub> reducing strategies. In this publication, a 2.0 liter compression ignition engine was tested in the pressurized motored configuration. This developed experimental setup allowed testing of the engine at speeds ranging between 1400 rpm and 3000 rpm, with peak in-cylinder gas pressures from 40 bar to 100 bar. The engine was motored using different gas compositions chosen specifically to have ratios of specific heats of 1.40, 1.50, 1.60 and 1.67 at room temperature. This enabled motored testing with peak in-cylinder bulk gas temperatures ranging from 700 K to 1500 K. This wide variation of peak bulk gas temperature was achievable even at constant peak in-cylinder gas pressure, which gave the possibility of varying the thermal load of the engine independently from the gas pressure load. This experimental setup offered the repeatability and robustness of motored testing, with the benefit of a fired-representative gas pressure and thermal load. Throughout the test matrix, the engine was instrumented with eroding surface thermocouples at two locations in the cylinder head; at the cylinder central axis, and at the periphery in the squish region. The steady-state and transient components of heat flux were investigated separately, along with the average surface temperature and its swing. The transient component of heat flux was computed using the Impulse Response method, coupled with a two-dimensional finite element model of the eroding thermocouples, as presented in SAE 2021-24-0018. This method takes into account the two-dimensional nature of heat flux through the thermocouples and hence presents a more robust analysis than the more common one-dimensional treatment using the Fast-Fourier Transform method.</div></div>

Fuel Injector Selection in Diesel Engine for BS6 Upgradation

<div class="section abstract"><div class="htmlview paragraph">For meeting the stringent BS VI emissions in a 3-cylinder diesel engine the Exhaust after treatment system (EATS) was upgraded from a single brick DOC (diesel oxidation catalyst) to 2 brick DOC+sDPF (Diesel Particulate Filter) configuration. To meet the demands of emission regulation and sDPF requirements, changes were also required in the Fuel injection system. Major changes were done to the fuel injector and fuel pump.</div><div class="htmlview paragraph">This paper primarily discusses the Fuel injector change from 1.1 to 2.2 family with changes in nozzle geometry, Nozzle tip protrusion (NTP), and injector cone angle and the effects on the emission and performance parameters. The various design values of NTP, cone angle, and Sac values are tested in an actual engine to meet the required power, torque and verified to meet NOx, HC, PM values as required by the new BS (Bharat Stage) VI regulation. Other boundary conditions are also checked - BSFC (Brake Specific Fuel Consumption), temperature, etc. The design change that was needed for the injector up-gradation - Cylinder head interface and injector clamp are also described in detail.</div><div class="htmlview paragraph">The paper also discusses the durability tests done for validating the new injector on parameters like nozzle coking, nozzle tip temperature, and various endurance tests reports are discussed. The finalized design has been validated on both engine testbed and vehicle successfully.</div></div>

LES-Predicted Flow Patterning in a Newly-Designed Reference Test Sample with Relevance to IC Engine-Related Cooling Channels

<div class="section abstract"><div class="htmlview paragraph">A test sample configuration with a circular cross-section has been conceptualized to reproduce all geometrically relevant flow-guided elements - straight segments, deflections, bifurcations, impingement regions, confluence - as they can also be found in the cooling systems of realistic Internal Combustion (IC) engines. This newly-designed reference test sample is termed as Water Spider Geometry (WSG), with the shape inspired by the flow guidance around an IC engine cylinder head. Computational investigations are carried out within the framework of a BMWi (German Federal Ministry for Economic Affairs and Energy) project by applying a well-resolved, highly comprehensive Large Eddy Simulation aiming at providing a meaningful assessment of the isothermal flow topology within the WSG. The basis forms a fully-hexahedral, block-structured grid arrangement comprising 290 million cells with the results considered to be a reference solution for further investigations.</div></div>

Wear Study of Cubic Boron Nitride (cBN) Cutting Tool for Machining of Compacted Graphite Iron (CGI) with Different Metalworking Fluids

Due to its desirable mechanical properties, compacted graphite iron (CGI) has been used to replace conventional gray cast iron (CI) in various applications, such as automotive engine blocks and cylinder heads. However, the poor machinability of CGI can lead to excessive tool wear and consequently high manufacturing costs. Various strategies have been developed to improve the machinability of CGI, including optimizing machining parameters and the development of novel metalworking fluids. In this study, machining of CGI was conducted using cubic boron nitride (cBN) tools under different cutting speeds, with both soluble and full-synthetic water-based metalworking fluids at different levels of sulfur addition and water dilution. The effects of the metalworking fluids on the tool wear behavior were examined. Results showed that at 200 m/min cutting speed, the soluble metalworking fluid at 4% dilution and 0.3% sulfur compound exhibited the best performance, with a cutting distance reaching 23.8 km. In contrast, the least effective soluble metalworking fluid at 9% dilution and 0.3% sulfur compound resulted in a 28.6% decrease in the cutting distance (17.0 km) compared to the best one. At a higher speed (300 m/min), the cutting distance for all metalworking fluids dropped to less than 6.0 km, with the full-synthetic metalworking fluid showing the shortest cutting distance of 4.8 km.

Experimental comparison between an optical and an all-metal large bore engine

Rising engine efficiency, increasingly stringent exhaust limits, and the use of synthetic and renewable fuels are all factors that demand a deeper knowledge of the combustion process. State-of-the-art investigations employ optical and laser-optical measurement techniques that rely on having optical access to the engine. In this paper, a new endoscopic system that provides full optical access to a high-speed large-bore engine is compared by thermodynamic experimentation to the equivalent all-metal engine. This comparison provides an insight into the altered combustion behavior resulting from modifying the engine to accommodate the optical elements. The successfully realized concept consists of two individually usable access points integrated in an engine with a bore of 170 mm and a stroke of 210 mm. The lateral endoscopic access is designed for full-load operating conditions and provides the best comparability to an all-metal engine. It is compared directly to the all-metal engine in the present investigations. Despite the changes in engine-out emissions from the optical engine, the experimental results display relatively equal combustion behavior in both setups. The lateral endoscopic access is then extended by adding a fisheye endoscope in place of one exhaust valve. This setup is compared to findings obtained with the endoscopic lateral access. The investigations reveal further deviations of the combustion process due to the more extensive modifications needed to fit the fisheye endoscope to the cylinder head. Nevertheless, the results display an overall good level of comparability of the combustion behaviors in these setups and, in turn, of the validity of further fundamental experiments based on the optical engine.

Microstructure related analysis of tensile and fatigue properties for sand casting aluminum alloy cylinder head

The microstructure and mechanical properties of top plate, force wall and bottom plate in low-pressure sand-casting aluminum alloy cylinder head were evaluated at room temperature. The results of the comparison study showed that with different positions of the cylinder head, the microstructure and mechanical properties were considerably different. For the convenience of analysis and discussion, the quality index (Q) was used to characterize tensile test data, which equals ultimate tensile strength plus 150 log elongation. The top plate has the best tensile performance with Q of 443.5 MPa, while the Q of the force wall (292 MPa) and bottom plate (355.5 MPa) is only 66% and 80% of that on the top plate. The tensile properties of the cylinder head are mainly controlled by dendrite arm spacing (DAS), including primary dendrite arm spacing (PDAS) and second dendrite arm spacing (SDAS). The influence intensity varies with the value of DAS. In general, the tensile properties decreased with the increase of DAS. When the aluminum alloy specimen has small DAS (PDAS ≤ 46.49 µm, SDAS ≤ 33.64 µm), Q increases rapidly with the decrease of DAS. However, when PDAS ≥ 104.33 µm, SDAS ≥ 49.82 µm, the effect intensity of DAS on tensile properties is partially reduced. When the number of cycles is 2.5 × 107, the fatigue stress limits of the top plate (69.2 MPa) and bottom plate (70.0 MPa) are highly comparable, which is mainly due to the similar SDAS and eutectic Si average area. Porosity defects also have a significant impact on fatigue performance. The presence of porosity defects increases the scatter of fatigue properties. In addition, more than 90% of the fractures are caused by porosity defects, which indicates that porosity defects are the main factor causing fatigue cracking of low-pressure sand-casting aluminum alloy cylinder head. Therefore, the casting process should be optimized to avoid porosity defects as much as possible in order to improve fatigue performance.

An exploratory numerical study of a diesel/methanol dual-fuel injector: Effects of nozzle number, nozzle diameter and spray spacial angle on a diesel/methanol dual-fuel direct injection engine

Methanol direct-injection makes it possible to the application of methanol at a high substitution ratio in diesel engines, but it is difficult to add a methanol injector to the already compact cylinder head. Therefore, an idea of a diesel/methanol dual-fuel injector is proposed, which can overcome both the inconvenience of arranging two injectors on the cylinder head and the disadvantage that the two injectors cannot be located in the center of the piston pit simultaneously. A three-dimensional simulation model coupled with chemical reaction kinetics is used to explore the effect of dual-fuel injector parameters including nozzle number and diesel/methanol spray spatial angle (β) on a diesel/methanol dual-fuel direct injection engine. The results show that more nozzles and smaller nozzle diameter contribute to fuel economy as well as the reduction of soot, THC, CO, and CH2O emissions, but higher ringing intensity (RI) and NOx emissions. It is found that 8 nozzles are the most suitable after weighing fuel economy, RI, and emissions. Secondly, influenced by the in-cylinder airflow, there exists an optimal spray spatial angle (β = 10°) to obtain the best fuel economy and emissions.

Probability of Detection applied to X-ray inspection using numerical simulations

In this work, we apply and adapt established Probability of Detection (POD) methods on inline inspection of aluminium cylinder heads using X-ray computed tomography. The CT simulation tool SimCT [4] is used to acquire virtual images of the specimens including artificial defects, which avoids the manufacturing of calibrated defects of known type (e.g., pore, inclusion, crack etc.), size and location. One of the exemplary defects is discussed as representative result together with the generated POD curves as well as its characteristics (i.e., the minimum detected defect, the maximum missed defect, POD(a90) =0.90 and a90/95).

Influence of DMC percentage in fuel on deposit formation and emission behaviour

E-Fuels are gaining in importance in the development of internal combustion engines. Their properties can differ from currently used fuels and affect the combustion behaviour. Here, the influence of the potential e-Fuel dimethylcarbonate (DMC) on the combustion process is investigated with the focus on combustion chamber deposit (CCD) formation. The effect of DMC on the CCD formation was observed. A one-cylinder research engine was equipped with changeable samples to investigate the deposit with a confocal microscope in addition to an in-situ measurement. The deposits on the top of the piston were compared to the deposits on the cylinder head. Furthermore, the dependency of the emissions on the DMC content in the fuel was characterized. The emphasis is on the gaseous emissions HC, NOx and CO2 and the emitted particle number. For a detailed analysis, an optical access was used to capture images of the combustion process.

Study of In-Cylinder Heat Transfer Boundary Conditions for Diesel Engines Under Variable Altitudes Based on the CHT Model

The reliability of combustion chamber components is mainly determined by the thermal load of diesel engines. Under the plateau operation condition, diesel engine performance degradation and ablation area appear. Therefore, it is crucial to study the engine heat transfer phenomenon at different altitudes, of which the Woschni formula cannot meet the accuracy requirement. With the motive of modifying and calibrating the Woschni formula at different altitudes, a modified conjugate heat transfer (CHT) model of the combustion chamber and the cooling medium was proposed to analyze the temperature distribution of the cylinder head. The results indicated that relative errors were controlled within 5% under variant altitudes, comparing the temperature field of the numerical simulation with the single-cylinder engine experiment test data. Therefore, the modified in-cylinder conjugate heat transfer model can be used to predict the thermal load of diesel engine combustion chamber components under different altitude operating conditions.

Thermo-mechanical fatigue life prediction based on the simulated component of cylinder head

As the vulnerable component of diesel engine, cylinder head is subjected to the thermo-mechanical coupling loads more and more heavily. For establishing a simple and effective technology to evaluate the damage degree, a prediction method based on simulated component is developed in the present work. By the comparison of temperature and stress at measured points, it shows that the simulation and testing results have a good agreement, verifying the effectiveness of simulated component. Applying Sehitoglu theory and loading spectrums, the failure locations are predicted successfully. Then damage characteristics of thermo-mechanical fatigue are analyzed at failure locations. It indicates that mechanical damage takes a leading role compared with oxidative damage and creep damage, and thermal load is more sensitive to mechanical damage in three damage types. This study may provide an effective way to estimate the service life of cylinder head.

An investigation on tensile and fatigue properties of cast Al-7Si-1.5Cu alloy applied in cylinder head considering size effect phenomenon

The cylinder head is one of the most critical diesel engine components. Under service conditions, different loads are exerted on the cylinder head, leading to the failure of various degrees at different positions of the cylinder head. In this study, the differences in mechanical properties at the different positions of the cylinder head are investigated by sampling specimens, metallography measurement, tensile and fatigue tests, and fracture surface analysis. Meanwhile, the Weibull statistical distribution method is used to analyze the size effect of the specimen. The results show that the microstructure features of the cylinder head exhibit high spatial heterogeneity. The mechanical properties are affected by microstructure features. The tensile properties of the top plate are optimum, followed by the flame plate, and the connecting wall has the worst properties. The difference in tensile properties at different positions is mainly affected by the grain and eutectic structure. In the same position, the tensile and fatigue properties of standard specimens are better than small specimens. The porosity is the critical parameter determining the tensile and fatigue properties of the different specimens. In addition, based on the statistical analysis of mechanical properties, the relationship of mechanical properties between the standard and small specimens was established. Through the established relationship, the mechanical properties of small specimens can be used to predict the mechanical properties of standard specimens, and the predicted value is in good agreement with the experimental data.

Influence of piston crown shape with different positions of spark plug and fuel injector, %EGR, and fuel system control on emissions from modified GDI engines compared with a base diesel engine

In this study, the combustion chamber profiles were developed for spray, wall, and air-guided gasoline direct injection (GDI) engines. For each combustion chamber geometry of GDI engine, the piston crown surface was modified, from hemispherical bowl, to trapezoidal bowl, and a pent roof shape that included a scoop type bowl on one side (towards injector position) to impart better squish, swirl, tumble, and turbulence effects to improve the mixing characteristics. Also, the cylinder heads were modified for each combustion chamber geometry by changing the locations of the spark plug and fuel injector. Further, the fuel split injection timings with duration, ignition timing, and the percentage of exhaust gas recirculation were optimized to reduce an engine out emissions; especially soot and nitrogen oxides. Emission tests were conducted on the base diesel engine and the GDI engine with the three different combustion chamber geometries. It is clear from the results that the emission of nitrogen oxides in the wall-guided mode was reduced by 5% till 75% of the load when compared with spray-guided and air-guided combustion modes. Overall, the GDI engine with the wall-guided combustion chamber geometry produced better results at 150 bar fuel injection pressure when compared with the base diesel engine; nitrogen oxides emission was reduced from 377 to 77 ppm and soot emissions were reduced from 29.3 to 4.5 g/km at high torque.