bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallelized Multiscale Off-Road Vehicle Mobility Simulation Algorithm and Full-Scale Vehicle Validation
Authors: Yamashita Hiroki , Chen Guanchu , Ruan Yeefeng , Jayakumar Paramsothy , Sugiyama Hiroyuki 
Published: March 2020

Abstract
In this work, a scalable parallel computing scheme for the hierarchical multiscale off-road vehicle mobility simulation capability is developed with the hybrid message passing interface (MPI)/OpenMP framework, and it is validated against full-scale vehicle test data. While the hierarchical multiscale modeling approach has been introduced to high-fidelity off-road mobility simulations to eliminate limitations of existing single-scale deformable terrain models, computational complexities associated with the large dimensionality of multibody vehicle equations, involving nonlinear finite element tires and multiscale terrain models, need to be addressed for use in full-scale vehicle mobility predictions. To this end, a co-simulation framework for the multiscale off-road vehicle mobility model is proposed by exploiting the moving soil patch technique. This allows for systematically extracting four moving soil patches for four tires in a vehicle model from the deformable terrain domain, and time integrations of the four tire–soil subsystems are performed concurrently to enable computational speedup. Furthermore, an automated updating scheme for multiscale moving soil patches for a full vehicle model is developed, considering the multipass effect in various vehicle maneuvering scenarios. To demonstrate the off-road mobility prediction capability using the proposed parallelized multiscale vehicle–terrain interaction simulation algorithm, full-scale vehicle validation is presented for the vehicle drawbar pull as well as variable grade hill climb tests on soft soil.
Parametric Estimation of Volterra Kernel for the Dynamic Response of an Offshore Structure Using Laguerre Polynomials
Authors: Son Jae-Hyeon , Kim Yooil 
Published: March 2020

Abstract
The behavior of a nonlinear dynamic system under arbitrary excitation can be represented by the Volterra series if the Volterra kernels of different orders are known. This study presents a methodology for a direct estimation of the Volterra kernel coefficients up to the second-order using prepared data obtained by running a time-domain analysis of the system of interest. To avoid potential problems during kernel estimation, the Volterra kernel is expanded into a polynomial series using the Laguerre polynomials, and the coefficients of the Laguerre polynomials are then estimated using a least-square method. A nonlinear oscillator with a quadratic stiffness term is introduced, and the methodology is applied to check the applicability and accuracy. The methodology is applied to a more realistic engineering problem of a simplified riser under irregular wave excitation.
Fatigue Life Estimation for HFMI-Treated Weldments Considering Weld Toe Magnification Factors
Authors: Kim Dong-Yub , Kim Myung-Hyun 
Published: March 2020

AbstractHigh-frequency mechanical impact (HFMI) post-treatment is a proven method to improve the fatigue life of welded structures. The positive effects of HFMI treatment are influenced by the weld toe geometries and residual stresses. This study investigates the effect of geometric and mechanical improvements by HFMI treatment on fatigue strength with explicit consideration of the weld toe magnification factor. General fatigue life estimation method is based on experiment data, and residual stress may be considered in addition. In terms of HFMI-treated structures, geometric improvement also affects the fatigue life. Thus, a more efficient method is suggested by considering the weld toe magnification factor to assess the effects of HFMI treatment. First, the weld toe magnification factor in HFMI-treated conditions is calculated to consider the geometrical effect of HFMI treatment at the weld toe region. Second, a stress ratio model is introduced to consider the compressive residual stress by HFMI treatment based on the Paris equation. The results were validated by comparing them with the estimated fatigue life from previous studies on HFMI-treated welded specimens.
Transient Fuel Spray Structure for Simulated Injection Strategies in Direct Injection, Spark Ignition Engines
Authors: Hutchison P. A. , Wicker R. B. 
Published: March 2020

Abstract
For two production DISI fuel injectors, flow visualization and particle image velocimetry (PIV) were utilized to illustrate the effect of fuel rail pressure and in-cylinder density (using in-cylinder pressure) on instantaneous fuel spray structure. Studies were performed within a non-motored research cylinder for two fuel rail pressures (3 MPa and 5 MPa) and two in-cylinder pressures (2 atm and 6 atm). Instantaneous flow visualization demonstrated the effects of changes in fuel rail pressure and in-cylinder density on transient spray structure. Increased fuel rail pressure resulted in increased narrowing of the spray cross-section and increased spray penetration distance. Increased in-cylinder density produced sprays with increased narrowing of the spray cross-section and shorter penetration distances. Spray velocities were shown to increase with increased fuel rail pressure and decrease with increased in-cylinder density.
A Study on the Breakdown Voltage Analysis of the Spark Plug Gap for Extraction of the Information About the Pressure in Cylinder
Authors: Park Jaekeun , Chae Jaeou 
Published: March 2020

Abstract
In-cylinder pressure of an internal combustion engine is considered to be a major source of information about combustion process. It is a generally accepted method to obtain an in-cylinder pressure signal using a pressure sensor (transducer). A different method of approach is presented in this study. The information about the in-cylinder pressure can be obtained by measuring breakdown voltage across the spark-plug gap.
The density of gas inside the combustion chamber effect on the breakdown voltage of the spark plug, which is derived by the application of a high bias voltage (30kV) to the sparkplug gap continuously. The correlation between maximum breakdown voltage position and peak pressure position is established by this principle. So it is possible to detect the peak pressure position by measuring the breakdown voltage of the spark plug. The analyzing method of the breakdown voltage signal is also presented.
Applying the Representative Interactive Flamelet Model to Evaluate the Potential Effect of Wall Heat Transfer on Soot Emissions in a Small-Bore DI Diesel Engine
Authors: Hergart Carl , Peters Norbert 
Published: March 2020

Abstract
Due to the wide spectrum of turbulent and chemical length- and time scales occurring in a HSDI diesel engine, capturing the correct physics and chemistry underlying combustion poses a tremendous modeling challenge. The processes related to the two-phase flow in a DI diesel engine add even more complexity to the total modeling effort. The Representative Interactive Flamelet (RIF) model has gained widespread attention owing to its ability of correctly describing ignition, combustion and pollutant formation phenomena. This is achieved by incorporating very detailed chemistry for the gas phase as well as the soot particle growth and oxidation, without imposing any significant computational penalty. The model, which is based on the laminar flamelet concept, treats a turbulent flame as an ensemble of thin, locally one-dimensional flame structures, whose chemistry is fast. A potential explanation for the significant underprediction of part load soot observed in previous studies applying the model is the neglect of wall heat losses in the flamelet chemistry model. By introducing an additional source term in the flamelet temperature equation, directly coupled to the wall heat transfer predicted by the CFD-code, flamelets exposed to walls are assigned heat losses of various magnitudes. Results using the model in three-dimensional simulations of the combustion process in a small-bore direct injection diesel engine indicate that the experimentally observed emissions of soot may have their origin in flame quenching at the relatively cold combustion chamber walls.
Theoretical Investigation on the Influence of Physical Parameters on Soot and NOx Engine Emissions
Authors: de Risi Arturo , Donateo Teresa , Laforgia Domenico 
Published: March 2020

Abstract
CFD simulations need a certain number of parameters to calibrate both empirical and analytical models. The present investigation aims at identifying the effects of these parameters on the numerical prediction of a modified version of Kiva 3V code, which includes the use of the RNG k-ε model for turbulence, the gas/wall convective heat transfer model proposed by Han, Kelvin-Helmholtz Rayleigh-Taylor spray injection and breakup models. Ignition delay was modeled with the Shell model, whereas the laminar-turbulent characteristic time model was used for combustion. Soot formation and oxidation were calculated using Hiroyasu and Nagle and Strickland-Constable models, respectively. NOx was predicted by using the extended Zel’dovich mechanism.
This study was carried out for a common-rail direct injection, small-bore Diesel engine, including the investigation of both numerical and physical parameters. Numerical parameters are intended to be variables related to breakup, turbulence, and combustion models that are adjusted according to grid resolution, engine and injection system geometry, and operating conditions. In particular, the effect of laminar and turbulent time scales, characteristic breakup length and time scales, initial turbulence kinetic energy density, initial swirl velocity profile, on engine emissions was analyzed.
The investigated physical parameters were initial swirl ratio, air water content, Schmidt number for mass diffusion.
All simulations were performed by changing one of the above parameters at each run and keeping approximately the same pressure and heat release rate curves. Results show that similar pressure vs. crank angle curves can be obtained with different values of these parameters but they lead to very different values of predicted emissions levels. In particular, changes of laminar and turbulent characteristic time resulted in a strong influence on NOx emissions but their effects on soot levels were minor. Mass diffusion characteristics (e.g. Schmidt number) were found to strongly affect both soot and NOx emissions. Spray parameters were found mainly to affect soot formation. Furthermore, NOx and soot emissions showed a dependence on swirl ratio and velocity profile.
The Effect of Subgrid Modeling on the In-Cylinder Unsteady Mixing Process in a Direct Injection Engine
Authors: Sone Kazuo , Menon Suresh 
Published: March 2020

Abstract
The process of fuel-air mixing in the Direct Injection Spark Ignition (DISI) engine is highly unsteady and three-dimensional with wide cycle-to-cycle variations involving vaporization of droplets and its interaction with large-scale turbulent flow field. Although the majority of the past numerical studies of mixing in an Internal Combustion (IC) engines have employed Reynolds-Averaged Navier-Stokes (RANS) equations with empirical turbulence model, here we have implemented a Large-Eddy Simulations (LES) with the Linear-Eddy Model (LEM) for subgrid scalar mixing into a commercial IC engine simulation code (KIVA-3V). This study shows that when time-accurate effects are included significantly different results are obtained. These differences between the original KTVA-3V and the new KIVALES in predicting the in-cylinder turbulent fuel-air mixing are discussed. LES shows highly unsteady, anisotropic in-cylinder fuel-air mixing process compared to the original KIVA-3V. The implications for combustion is also discussed.
Laser Based Measurements of Instantaneous Characteristics in High Pressure Fuel Injection and Swirl Spray
Authors: Ismailov Murad M. 
Published: March 2020

Abstract
Transient dynamics of two injection flows, upstream and downstream from a swirl injector, are investigated. Capillary n-heptane pipe flow is measured using laser Doppler anemometer to obtain the instantaneous time series of centerline velocity and to reconstruct a series of instantaneous and integrated flow rates and pressure gradients. A collimated laser sheet and a high-speed video camera visualize injected spray flow. Finally, the phase Doppler anemometer measurements are introduced to analyze instantaneous patterns of droplets, velocity-size and number density in the fuel spray.
All measurements are employed at similar temporal resolution close to 30 μs. Results indicate that both flows are strongly time-dependent and well correlated in time-phases. Initial transitions are completed by 100 μs. Opening or closing of the injector valve affects both flows as strong delta oscillation causes spray penetration dynamics and a post injection effect.
A combination of non-intrusive laser-based techniques allows indication of the basic injection and spraying characteristics needed to optimize high-pressure fuel injectors and the late injection combustion mode.
A Study on Cylinder Bore Deformation of a Diesel Engine With Dry Liner Structure
Authors: Yamamoto Shigeto , Sakita Hiroshi , Takiguchi Masaaki , Sasaki Shinichi 
Published: March 2020

Abstract
The deformation of the cylinder liner of a diesel engine in actual operation have been measured by the means of a rotary piston, and the deformation has been compared with those measured statically at room temperature. As a result, it is found that the deformation of the liner in engine operation is hardly affected by the deformation at room temperature, but it follows the deformation of the cylinder block where the liner is inserted. It is also found as follows: The deformation of the liner upper portion varies according to the head bolts and the engine load, while the effect of the cylinder pressure is insignificant. The deformation at the middle of the liner changes mainly by the thermal expansion in the thrust direction, while the deformation at the lower portion is not affected by the engine speed or the load.
Piston Slap Induced Noise Simulation Considering Elasto-Hydrodynamic Contact Conditions
Authors: Priebsch Hans H. , Herbst Hubert M. , Offner Günter 
Published: March 2020

Abstract
Main aims in the development process for the cylinder assembly of internal combustion engines are the reduction of friction and wear due to the contact between piston and liner as well as the minimization of piston slap induced noise.
In this paper, the authors extend their methodology for the simulation of structural dynamics in the area of piston and liner with the aim of predicting structure borne noise excited by the piston slap phenomenon. The simulation model uses linear, flexible bodies subjected to highly non-linear joint forces, as occurring in the piston-to-liner contact. Both, the theoretical background and the advantages of the coupled simulation procedure for such complex systems are discussed. The models are validated by comparison of measured and computed values of piston movements and modal structure behavior.
The result examples focus on the effects of piston secondary movement, the resulting impact on the lubricated liner and the analysis of vibration transfer behavior in the block structure. It is shown how noise excitation and structure borne vibration transfer paths can be analyzed in order to assess engine design. Result plots show typical results on the surface of a 4 Cylinder Diesel engine and the contribution of piston slap induced noise.
Analysis of Oil Film Thickness on a Piston Ring of Diesel Engine: Effect of Oil Film Temperature
Authors: Harigaya Yasuo , Suzuki Michiyoshi , Takiguchi Masaaki 
Published: March 2020

Abstract
This paper describes that an analysis of oil film thickness on a piston ring of diesel engine. The oil film thickness has been performed by using Reynolds equation and unsteady, two-dimensional (2-D) energy equation with a heat generated from viscous dissipation. The temperature distribution in the oil film is calculated by using the energy equation and the mean oil film temperature is computed. Then the viscosity of oil film is estimated by using the mean oil film temperature. The effect of oil film temperature on the oil film thickness of a piston ring was examined. This model has been verified with published experimental results. Moreover, the heat flow at ring and liner surfaces was examined. As a result, the oil film thickness could be calculated by using the viscosity estimated from the mean oil film temperature and the calculated value is agreement with the measured values.
Study on Wear of Piston Rings in Diesel Engines With Exhaust Gas Recirculation
Authors: Sato Tokuro , Saito Hideki , Korematsu Koji , Tanaka Junya 
Published: March 2020

Abstract
The wear of piston rings in the diesel engines with EGR system is studied experimentally. In order to clarify the effect of PM on the wear, the wear of the piston rings in the test engine is measured,
(1) when the non-soluble in the lubricating oil is removed by the oil filters,
(2) when PM in the re-circulating gas is removed by the DPF,
(3) when the carbon black is added in the lubricating oil.
The experimental results are discussed with the measured time history of kinematic viscosity, total base number, total acid number, ZDTP survival rate, and carbon residual content and its particle size in the engine oil.
Model Based Analysis of Turbocharger Power Assist Systems for Reduced Turbo-Lag
Authors: Upadhyay Devesh , Rizzoni Giorgio 
Published: March 2020

Abstract
As Diesel engines continue to find favor amongst automakers, two aspects common to all Diesel engines remain at the center of all research activity. While reduction of Diesel emissions, such as NOx, Particulate Matter (PM) and smoke continues to be the more serious challenge, the issue of acceleration performance remains to be fully resolved. If the diesel engine is to find acceptance amongst the US passenger car users, it must perform at the level of the Spark Ignition (SI) engine in terms of brisk acceleration response. It is imperative that the Diesel engine shakes off the image of “the sluggish machine”. Technically this amounts to either reducing turbo-Lag to an indiscernible level or eliminating it completely. Since turbo-Lag is linked directly to turbocharger (T/C) inertial dynamics, several techniques have been tried over the years to reduce this effect. In this paper we present a model-based evaluation of four techniques, namely:
1. Variable Geometry turbocharging (VGT).
2. Electrical Assist of turbochargers.
3. Hyperbar (HB) turbocharging.
4. External Air assist.
Variable Geometry turbocharging has already found wide application and is now considered an essential feature on all modern Diesel engines. Electrical assist of turbochargers for automotive application is still in its developmental stages but holds great promise. Hyperbar T/C and external air assist are unconventional techniques but offer possibilities of improvement for the T/C.
Dynamic Performance of Conventional and Electrically Activated Engine Thermostats
Authors: Gunter L. Alan , Nalim M. Razi 
Published: March 2020

Abstract
This study concerns the dynamic performance of passive and active wax-actuator driven thermostats. The study is extended to wax actuator driven thermostats that have been fitted with a heating device, such that the thermostat can be actuated electrically. The thermostat valve type chosen for this study is a balanced, sleeve-type thermostat typically used in large over-the-road and industrial diesel engines. The valve operates like a spool valve to direct the flow of the engine coolant to the bypass, the heat exchanger, or partially to each. Since conventional thermostats are passive devices they lag in response to dynamic engine conditions, and under certain circumstances overheating can occur as a result of the device’s inability to respond quickly. Also, conventional thermostats are designed to protect an engine against overheating year round. Therefore, a thermostat designed to protect against overheating in the summer will often result in an overcooling condition in the winter. One possible solution to the problem is to control the thermostat electrically through the electronic engine control system, or other system, making the thermostat an active control device instead of a passive one. In this study, a mathematical model is developed to determine wax temperature, and thereby predict the thermostat operation and response. The wax temperature depends on the heat transfer from the engine coolant through the brass cup that encapsulates the wax, as well as heat transfer from the heater. The simulations are compared with measurements of temperature, thermostat position and flow at several locations around the thermostat in an experimental set-up. The outcome is used to analyze the accuracy of the methods used in the thermodynamic calculations.
Bearing Characteristic Parameters to Estimate the Optimum Counterweight Mass of a 6-Cylinder In-Line Engine
Authors: Stanley Richard E. , Taraza Dinu 
Published: March 2020

Abstract
Two dimensionless relationships that estimate the maximum and average bearing load of a 6-cylinder 4-stroke in-line engine have been found. These relationships may assist the design engineer in choosing a desired counterweight mass. It has been demonstrated that: 1) the average bearing load increases with engine speed and 2) the maximum bearing load initially decreases with engine speed, reaches a minimum, then increases quickly with engine speed. This minimum refers to a critical speed at which the contribution of the inertia force overcomes the contribution of the maximum pressure force to the maximum bearing load. The critical speed increases with an increase of counterweight mass and is a function of maximum cylinder pressure and the operating parameters of the engine.
Air Bearing Models and Solutions for Sub-5 nm Spacings
Authors: Bogy D. B. , Wu Lin 
Published: March 2020

Abstract
When the flying height is below 5 nm, some physical phenomena that can be ignored for higher flying sliders need to be included in the modeling equations. Another challenging issue is the unavoidable asperity contact problem. It is known that zero spacing at asperities may cause some of the existing modified Reynolds equations to predict unphysical unbounded contact pressure singularities. In this paper we first review the source of these pressure singularities, showing which models have this problem and which do not. We also review here a new derivation of a compressible lubrication equation by using a different slip velocity boundary condition, in which additional slippage at the gas-solid interface due to pressure gradient is introduced. The new equation is free of any contact singularity [1]. Next we review our recent work on the non-negligible effect of the intermolecular forces on the slider’s flying attitude when the spacing is below 5 nm [2]. The additional force is attractive until the spacing is below about 0.1 nm for example and then it is repulsive. Finally we show the effect of these new force contributions on the flying attitude of a low flying slider.