Full Engine Cycle Research Articles

Finite Element Analysis of the Influence of the Assembly Parameters on the Fretting Phenomena at the Bearing/Big End Interface in High-Performance Connecting Rods

Fretting fatigue is a well-known and dangerous damage mode that occurs on the mating surfaces of mechanical components, mainly promoted by a combination of stress distribution, contact pressure distribution, and relative sliding (micro)motion between the surfaces. However, predicting this mechanism is challenging, necessitating specific studies for each assembly due to variable influences. This article presents a methodology for evaluating fretting fatigue damage at the contact between a titanium connecting rod big end and the bearing, adopting the Ruiz parameter as a quantifying damage index. For this purpose, a thermal-structural finite element model is prepared. In particular, the machining and assembly of the split conrod big end are simulated, considering thermal effects. A full engine cycle is first simulated, and results are used for identifying critical instants to be considered for accurate yet computationally efficient calculations. The dependence of fretting fatigue on three factors is studied: bearing crush, bolts tightening torque, and friction coefficient between the big end and the bearing. In summary, the damage increases with a higher crush and friction, while tightening torque has marginal effects. Following a 20% increase in crush height, a corresponding 10% rise in the Ruiz parameter is observed. Conversely, reducing the crush height by 20% leads to an approximately 8% decrease in the Ruiz parameter. When the influence of the bolt preload is taken into account, only a marginal 1% increase of the Ruiz parameter is recorded despite a 30% rise in preload. Evaluating the impact of the friction coefficient on the Ruiz parameter reveals an almost linear relationship. These findings suggest that adjusting the screw preload can enhance the hydrodynamic behavior of the bearing without exacerbating fretting. Furthermore, exploiting the linear correlation between Ruiz and the friction coefficient allows for the generalization of results obtained with specific coefficient values. This methodology can, therefore, serve as a valuable reference for adjusting different variables during the initial design phases of a four-stroke internal combustion engine’s dismountable connecting rod.

Unsteady Heat Transfer of Pulsating Gas Flows in a Gas-Dynamic System When Filling and Emptying a Cylinder (as Applied to Reciprocating Machines)

The thermal and mechanical perfection of the processes in the gas exchange system during the filling and emptying of the cylinder makes it possible to increase the productivity and efficiency of reciprocating machines for various purposes. The study was designed to obtain experimental data on the local heat transfer of pulsating flows in the intake and outlet pipelines of a piston engine model, their analysis, and mathematical description. The scientific novelty of the study is as follows: (1) the patterns of change in the local heat transfer coefficients of pulsating gas flows in the inlet and outlet pipelines for the piston engine model were obtained for the first time; (2) a mathematical description of the experimental data on local and average heat transfer in the inlet and outlet pipelines is proposed. The physical features of the change in the rate of heat transfer in the intake and exhaust systems for a full engine cycle are discussed. A spectral analysis of the harmonic functions of the change in the local heat-transfer coefficient in gas exchange systems is performed. A set of mathematical dependencies of changes in the local and average heat-transfer coefficients of flows in the inlet and outlet pipelines on operation factors are presented. These data can be used to assess the quality of filling and cleaning the cylinder, determining thermal stresses in the details of gas exchange systems, developing devices for using exhaust gas energy, creating engine control systems, and so on. Moreover, the results obtained can be used to adjust (and test) mathematical models, as well as refine engineering methods for calculating gas exchange processes in reciprocating machines for various purposes.

Heating and Evaporation of Droplets of Multicomponent and Blended Fuels: A Review of Recent Modeling Approaches

In this review, recent models for the heating/evaporation of multicomponent and blended fuel droplets and their implementation into numerical codes, used for the analysis of the processes in internal combustion engines, are reviewed. In these models, the diffusion of species, recirculation, and temperature gradient inside droplets are considered. The focus of the review is on the group of models based on the implementation of the analytical solutions to the heat transfer and species diffusion equations inside droplets into numerical codes. Four key aspects are summarized: (1) application of the Discrete Component (DC) model and the Multi-Dimensional Quasi-Discrete Model (MDQDM) to a broad range of fuels, including petrol, diesel, ethanol, and biodiesel fuels and their blends, (2) formulation of fuel surrogates, with a focus on the recently introduced Complex Fuel Surrogate Model (CFSM), (3) overview of the recently introduced transient algorithm, Transient Multi-Dimensional Quasi-Discrete Model (TMDQDM), for an autogeneration of quasi-components, and (4) implementation of the latter into a computational fluid dynamics (CFD) code for a realistic engineering application to full cycle simulation in internal combustion engines. The original and modified versions of the DC model and MDQDM are evaluated for the heating and evaporation of droplets of bio/fossil-fuel (e.g., ethanol/petrol/biodiesel/diesel) blends. These were implemented into commercial CFD software and validated. The feasibility of formulating complex fuel surrogates for fuel blends, their implementation into CFD codes, and their application in the full engine cycle simulation before and after the onset of combustion (autoignition) are described.

Precision in-cylinder H2O vapor absorption thermometry and the associated uncertainties

Water vapor absorption spectroscopy was used to measure crank-angle resolved temperature in an internal combustion engine for two intake pressures and a range of intake temperatures from 323 to 423 K. Measurements were acquired throughout the full engine cycle, for both motored and fired operating conditions. The methodology to convert absorbance measurements to processed temperatures up to values of 650 K are detailed in this work. The sensitivity of the processed temperature to the processing parameters was analyzed and quantified. The precision of the sampled mean with 95% confidence uncertainty bounds was 0.5%, and a comparison of the temperature estimates using the band shape thermometry technique was compared to both fast-response thermocouple measurements as well as a trapped-mass thermodynamic model.

Numerical analysis of methane slip source distribution in a four-stroke dual-fuel marine engine

We present the results of a numerical model which has been developed for estimating the contribution to the methane slip from different sources in a four-stroke dual-fuel marine engine running on natural gas. The model is a thermodynamic three-zone zero-dimensional full engine cycle model and considers methane slip contributions from short-circuiting, crevices and wall quenching. The model is applied to analyze the methane slip from a four-stroke dual-fuel medium speed marine engine using natural gas as primary fuel. At low loads, wall quenching is found to be the dominant contribution to the methane slip. At full load, the wall quenching contribution is comparable to the level of the short-circuiting and crevice contributions which only vary relatively little with load. At 75% load, the contribution from short-circuiting is highest. In addition, we found that in-cylinder post-oxidation of unburned fuel remaining after the main combustion is negligible.

Reactive computational fluid dynamics modelling methane–hydrogen admixtures in internal combustion engines part II: Large eddy simulation

Fuels based on admixtures of methane/natural gas and hydrogen are a promising way to reduce CO2 emissions of spark ignition engines and increase their efficiency. A lot of work was conducted experimentally, whereas only limited numerical work is available in the context of three-dimensional modelling of the full engine cycle. This work addresses this fact by proposing a reactive computational fluid dynamics modelling framework to consider the effects of hydrogen addition on the combustion process. Part I of this two-part study focuses on the modelling and crucial considerations in order to predict the mean cycle based on the G-equation combustion model using the Reynolds-averaged Navier–Stokes equations. There, the effect of increased burning speed was globally captured by increasing the flame speed coefficient A, appearing in the considered flame speed closure. The proposed simplified modelling of the early flame stage proved to be robust for the conducted hydrogen variation from 0 to 50 vol% H2 for stoichiometric and lean operation. Scope of this work, Part II, are cyclic fluctuations and the hydrogen influence thereon using large eddy simulation and the proposed modelling framework. The model is probed towards its capabilities to predict the fluctuation of the combustion process for 0 and 50 vol% H2 and correlations influencing the observed peak pressure of the individual cycle are presented. It is shown that the considered approach is capable to reproduce the cyclic fluctuations of the combustion process under the influence of hydrogen addition as well as lean operation. The importance of the early flame phase with respect to arising fluctuations is highlighted as well as the contribution of the resolved scales in terms of the flame front wrinkling.

Investigation of intake and exhaust manifolds parameters of a turbocharged diesel engine based on steady-state simulation

In the present work an approach to simulate and predict the flow characteristic in the intake and the exhaust manifolds of a six-cylinder four-stroke turbocharged diesel engine using GT-POWER and FORTRAN, for steady-state simulation. The simulation model covers the full engine cycle consisting of intake, compression, power and exhaust. The simulation and the prediction shown the diesel engine intake and exhaust manifolds parameters based on the crank angle degree. The results of the engine performances as well as pressure, temperature and mas flow rate in the intake and exhaust manifolds obtained by the developed program in language FORTRAN using the method of filling and emptying are presented. The commercial GT-Power software is used to the results validation. The range of variation of the rotational speed of the diesel engine chosen extends from 800 rpm to 2100 rpm. DOI: http://dx.doi.org/10.5755/j01.mech.25.2.21989

Performance and combustion analysis of diesel engine fueled with grape seed and waste cooking biodiesel

The study investigated the diesel engine performance and combustion using grape seed and waste cooking biodiesel blends. The experiment was conducted using a four-cylinder, four-stroke diesel engine coupled with an electromagnetic dynamometer. The biodiesel blend was prepared by a volumetric mixture of 5% biodiesel and 95% diesel, denoted as B5 and 10% biodiesel with 90% diesel referred as B10 for both grape seed and waste cooking biodiesel. The investigation on engine performance parameters, namely brake power, brake specific fuel consumption, and brake thermal efficiency were done by varying the engine speed from 1200 rpm to 2400 rpm at full load condition for both grape seed biodiesel blend (GS-B5, GS-B10) and waste cooking biodiesel blends (WC-B5, WC-B10) and compared with ultra-low-Sulphur diesel. In addition, the fuel combustion parameters, namely cylinder pressure, heat release rate, ignition delay, and combustion duration were analysed by varying crank for full engine cycle at a constant speed of 1400 rpm and 1600 rpm at full load condition. The study identified the GS-B5 as a better performing blend in terms of performance and combustion. Finally, the study developed a correlation between cylinder pressure (CP) and heat release rate (HRR) for GS-B5 blend only for 1400 rpm and 1600 rpm to observe the full cycle combustion phenomena. The study recommended further study on emission and tribological behavior of the fuel.

Numerical Study of a Direct Injection Internal Combustion Engine Burning a Blend of Hydrogen and Dimethyl Ether

In the reported study, various aspects of dimethyl ether/hydrogen combustion in a Reactivity Controlled Compression Ignition (RCCI) engine are numerically evaluated using Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES). Early direct injection and mixture propagation were also explored, along with peculiaritis of dimethyl ether combustion modeling. The numerical models are validated using available experimental results of a partially premixed dimethyl ether jet flames and an optically accessible internal combustion engine with direct hydrogen injection. LES showed more predictive results in modeling both combustion and mixture propagation. The same models were applied to a full engine cycle of an RCCI engine with stratified reactivity, to gain phenomenological insight into the physical processes involved in stratified reactivity combustion. We showed that 3D and turbulence considerations had a great impact on simulation results, and the LES was able to capture the pressure oscillations typical for this type of combustion.

Toward the accurate prediction of soot in engine applications

Soot emissions from internal combustion engines represent a major challenge to engine manufactures with ever most stringent emission regulations, not only in soot mass yielded but also in soot particle number. For example, a particulate number standard has been introduced in 2011 with Euro 5b for diesel engines and in 2014 with Euro 6 for petrol engines (a limit of 6 × 1011/km). Soot models provide a detailed insight into soot evolution processes and are thus an essential tool in today’s advanced engine designs. Therefore, continuous efforts are made to develop more physically based engine soot models and improve the prediction accuracy. The primary objective of this work is to identify and demonstrate the critical parameters for accurate soot predictions in internal combustion engine applications using the high-fidelity detailed soot model from an engineering point of view. A detailed soot model based on sectional method was used to solve the soot process in diesel and spark ignition direct injection gasoline engines. A series of sensitivity analyses were carried out to evaluate the importance and significance of wall boundary conditions, wall film formation and vaporization, multi-component fuel surrogate, and soot transport process in engine exhaust on soot predictions. The predicted results were compared in details to engine-out measurements in terms of soot mass, number density, and size distributions under various operating conditions. The model results demonstrate that the correct description of the spray–wall interaction and wall film vaporization, as well as the soot transport processes in full engine cycle, is critical for achieving reliable predictive capabilities in engine simulations, especially for spark ignition direct injection gasoline engines. The findings should help engineers in this field for more accurate soot predictions in engine simulations.

Piston ring performance in two-stroke marine diesel engines: Effect of hydrophobicity and artificial surface texturing on power efficiency

In the present work, an algorithm for the solution of the Reynolds equation incorporating the Elrod–Adams cavitation model and appropriately modified to account for hydrophobic surfaces has been developed and solved by means of the finite difference method. The algorithm has been utilized to calculate the frictional characteristics of piston rings of a large two-stroke marine diesel engine, and to evaluate their performance, in terms of minimum film thickness, friction force, and power loss over a full-engine cycle, including time-dependent phenomena. For improving frictional behavior, two surface treatments of the piston ring surface have been studied, namely hydrophobicity and artificial surface texturing, which are introduced at appropriate parts of the ring face. Following a parametric analysis, optimal texturing and hydrophobicity design parameters have been identified for operation with maximum value of minimum film thickness and minimum friction losses. The present results demonstrate that substantial performance improvement can be achieved if hydrophobicity or artificial surface texturing is properly introduced at the faces of a piston ring.

The Recuperated Split Cycle - Experimental Combustion Data from a Single Cylinder Test Rig

The conventional Diesel cycles engine is now approaching the practical limits of efficiency. The recuperated split cycle engine is an alternative cycle with the potential to achieve higher efficiencies than could be achieved using a conventional engine cycle. In a split cycle engine, the compression and combustion strokes are performed in separate chambers. This enables direct cooling of the compression cylinder reducing compression work, intra cycle heat recovery and low heat rejection expansion. Previously reported analysis has shown that brake efficiencies approaching 60% are attainable, representing a 33% improvement over current advanced heavy duty diesel engine. However, the achievement of complete, stable, compression ignited combustion has remained elusive to date. The challenge is to induct hot high pressure charge air close to top dead centre into the combustion cylinder and then inject and burn the fuel before the piston has travelled significantly down the expansion stroke. In this paper, we report results from a single cylinder split cycle combustion research engine. Stable, rapid combustion was achieved at 800 rpm and 1200 rpm at the retarded timings required for a split cycle engine. The calculated rate of heat release was more rapid than typically observed on conventional compression ignition engine suggesting good mixing of the fuel and air during induction. One dimensional cycle analysis was used to calculate the implications of the test results on the full engine cycle which indicated class leading brake efficiencies approaching and possibly exceeding, 60% are possible from a split cycle engine.

A proposed procedure for expressing the behavior of a full engine cycle by identifying its critical load timings

In the present study the authors propose a new algorithm for identifying the right loads that act upon a functional connecting rod during a full engine cycle. The loads are then divided into three categories depending on the results they produce, as static, semi-dynamic and dynamic ones Because an engine cycle extends up to 720°, the authors aim to identify a method of substitution of values that produce the same effect as a previous value of a considered angle did. In other words, the proposed method aims to pin point the critical values that produce an effect different as the one seen before during a full engine cycle. Only those values will then be considered as valid loads that act upon the connecting rod inside FEA analyses. This technique has been applied to each of the three categories mentioned above and did produced different critical values for each one of them. The whole study relies on a theoretical mechanical project which was developed in order to identify the right values that correspond to each degree of the entire engine cycle of a Daewoo Tico automobile.

A full engine cycle analysis of a turbofan engine for optimum scheduling of variable guide vanes

This paper proposes a full engine cycle analysis to derive the schedule of variable guide vanes (VGVs) in a multi-stage axial compressor for improving the performance of a turbofan engine with required surge margin. Most researchers assumed the operating line of a compressor in process of scheduling of VGVs. However, it has been known that the performance of a compressor is influenced by the angle of VGVs. As a result, the performance variation of a compressor can affect an engine. Therefore, a full engine cycle analysis is conducted to consider the effect of VGVs on a turbofan engine. The VGVs are applied to the front stages of the high pressure compressor in the low-bypass ratio turbofan engine. The compressor of the front stages is transonic three-stage axial flow compressor. The commercial engine simulation program, NPSSTM is employed to analyze the on- and off-design performance of the turbofan engine. 1D meanline analysis is used for performance prediction of a multi-stage axial flow compressor with VGVs. The engine simulation program is coupled with the compressor performance prediction tool to consider the engine performance variation with application of the VGVs. The proposed scheduling algorithm of the inlet guide vane (IGV) and stator vanes (SV) is adjusting the vanes angle to have the minimum loss incidence angle at all rotor blades and to satisfy the required surge margin at off-design condition. The result shows that the proposed algorithm can obtain the scheduling of the IGV, 1st and 2nd SVs angle with stable operation and improved specific fuel consumption of the engine.

The effect of injection timing and intake valve close timing on performance and emissions of diesel PCCI engine with a full engine cycle CFD simulation

A full-cycle computational fluid dynamics (CFD) simulation coupled with detailed chemical kinetics mechanism has been used to investigate the effect of start of injection (SOI) timing and intake valve close (IVC) timing on performance and emissions of diesel premixed charge compression ignition (PCCI) engine. By sweeping SOI timing from −35 to −5 °CA ATDC and IVC timing from −140 to −80 °CA ATDC with fixed 50% exhaust gas recirculation (EGR) and 1.8 bar intake pressure, the contour plots for ignition timing, nitric oxides (NO x ), soot, hydrocarbon (HC), carbon monoxide (CO), indicated specific fuel consumption (ISFC), and ringing intensity have been developed. The results indicate that the operating range can be divided into kinetically controlled region and mixing-controlled region, in which the ignition timing is solely controlled by IVC timing and SOI timing respectively. To Minimize HC, CO, NO x and soot emissions, SOI timing must be carefully adjusted within a limited range. With the retarded IVC timing, the operating range of SOI becomes wider for clean combustion. The IVC timing should be optimized with consideration of ignition timing and combustion efficiency at different SOI timing in order to improve fuel economy. For purpose of avoiding engine knock, the SOI timing around −20 °CA ATDC and early IVC timing are pursued.

Research on Combustion Process and NOx Formation in a Marine Diesel Engine

This paper presents the simulation results of histories of pressure, temperature and NO concentrations as well as combustion process and NOx formation in a marine diesel engine. The simulation was done within a full engine cycle with a three-dimensional, transient combustion model including a more accurate NO formation model. Simulation results were verified by data obtained from benchmark tests and further analyses of distributions of pollutants were carried out in this paper. Conclusions from simulation about engine combustion and NOx formation have been finally achieved.

In-Cylinder Flow Computational Fluid Dynamics Analysis of a Four-Valve Spark Ignition Engine: Comparison Between Steady and Dynamic Tests

Numerical and experimental techniques were applied in order to study the in-cylinder flow field in a commercial four-valve per cylinder spark ignition engine. Investigation was aimed at analyzing the generation and evolution of tumble-vortex structures during the intake and compression strokes, and the capacity of this engine to promote turbulence enhancement during tumble degradation at the end of the compression stroke. For these purposes, three different approaches were analyzed. First, steady flow rig tests were experimentally carried out, and then reproduced by computational fluid dynamics (CFD). Once CFD was assessed, cold dynamic simulations of the full engine cycle were performed for several engine speeds (1500 rpm, 3000 rpm, and 4500 rpm). Steady and cold dynamic results were compared in order to assess the feasibility of the former to quantify the in-cylinder flow. After that, combustion was incorporated by means of a homogeneous heat source, and dynamic boundary conditions were introduced in order to approach real engine conditions. The combustion model estimates the burning rate as a function of some averaged in-cylinder flow variables (temperature, pressure, turbulent intensity, and piston position). Results were employed to characterize the in-cylinder flow field of the engine and to establish similarities and differences between the three performed tests that are currently used to estimate the engine mean flow characteristics (steady flow rig, and cold and real dynamic simulations).

Full Engine Cycle CFD Investigation of Effects of Variable Intake Valve Closing on Diesel PCCI Combustion and Emissions

A full-cycle three-dimensional computational fluid dynamics (CFD) model coupled with detailed chemical kinetics has been developed to investigate the effect of late intake valve closing (IVC) on combustion and emission characteristics in a diesel engine with premixed charge compression ignition (PCCI) combustion. The application of late IVC was demonstrated to provide efficient control of ignition timing and significant reduction of nitrogen oxides (NOx) and soot emissions by decreasing the effective compression ratio and increasing premixing, but it possibly led to increases of hydrocarbon (HC) and carbon monoxide (CO) emissions due to low combustion temperature and insufficient oxygen amount. Parametric studies by varying intake pressure, exhaust gas recirculation (EGR) rate and start of injection (SOI) timing with varied IVC timing were conducted to explore the potential of late IVC for emission reduction in diesel PCCI engines. The results showed that, with assistance of increasing intake pressure, late IVC could reduce NOx, soot, HC, and CO emissions simultaneously. A certain EGR rate and optimized SOI timing were always necessary to maintain satisfactory NOx and soot emissions for diesel PCCI combustion.

Investigation of Diesel Engine Performance Based on Simulation

The single cylinder modeling and simulation for four-stroke direct-injection diesel engine requires the use of advanced analysis and development tools to carry out of performance the diesel engine model. The simulation and computational development of modeling for the research use the commercial of GT-SUITE 6.2 software. In this research, the one dimensional modeling of single cylinder for four-stroke direct-injection diesel engine developed. The analysis of the model is combustion performance process in the engine cylinder. The model simulation covers the full engine cycle consisting of intake, compression, power and exhaust. In this model it can to know the diesel engine performance effect with simulation and modeling in any speeds (rpm) parameters. The performance trend of the diesel engine model developed result of this model based on the theoretical and computational model shows in graphics in the paper.

Computational Visualization and Simulation of Diesel Engines Valve Lift Performance Using CFD

The paper visualized and simulated the intake and exhaust valve lift in the single-cylinder four-stroke direct injection diesel engine. The visualization and simulation computational development were using the commercial Computational Fluid Dynamics of STAR-CD 3.15A software and GT-SUITE 6.2 software. The one dimensional of valve lift modeling was developed using GT-POWER software and the visualization the model using STAR-CD. The model simulation covers the full engine cycle consisting of intake, compression, power and exhaust. The visualization and simulation shown the diesel engine intake and exhaust valve lifting and moving based on the crank angle degree parameters. The result of this visualization and simulation shows the intake and exhaust valve lift moving and air fluid flow of the diesel engine model.