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Journal Article

The Effect of Engine Speed, Exhaust Gas Recirculation, and Compression Ratio on Isobaric Combustion

Abstract The present study evaluates the effect of engine speed, exhaust gas recirculation (EGR), and compression ratio on conventional diesel combustion (CDC) and two isobaric combustion cases, by utilizing multiple injection strategies. The experiments were conducted in a Volvo D13C500 single-cylinder, heavy-duty engine, fuelled with standard European Union (EU) diesel fuel. The engine was operated at three different speeds of 1200, 1500, and 1800 revolutions per minute (rpm). For each engine speed and combustion cases, the EGR rate was varied from 0% to 40%. The low-pressure isobaric combustion (IsoL) and high-pressure isobaric combustion (IsoH) were maintained at peak cylinder pressure (PCP) of 50 and 68 bar, respectively, which was representative of the peak motoring pressure (PMP) and PCP of CDC. This was possible by adjusting the intake air pressure to 1.7 and 2.3 bar—absolute for IsoL and IsoH, respectively, at 1200 rpm.
Journal Article

Mathematics of Turbomachinery: Centrifugal Impeller

Abstract The mathematics required to design and analyze turbomachinery were gathered from many sources and presented in its entirety as a single source, step-by-step procedure. An impeller was then designed and analyzed. A one-dimensional (1D) model explains the mathematics for performance in detail. The 1D model lacked the ability to predict flow-related phenomena such as flow surge but highlighted the direct connection between blade angle and rotation direction with pressure rise and efficiency. For the present study, positive blade angles pointing in the direction of rotation (clockwise in the present study) provided higher pressure rise and higher losses. Negative blade angles pointing in the opposite direction of rotation (counterclockwise in the present study) resulted in lower pressure rise and lower losses. Flow surge was studied with a three-dimensional (3D) model.
Journal Article

Analysis of Deflection and Contact Characteristics of a Pneumatic Tire Using Three-Dimensional Membrane Ring and Brush Models

Abstract This study predicts the dynamic characteristics for tires in the development stages of a vehicle with a focus on the generated forces. In particular, this investigation proposes an approximation analysis for the deflection and contact characteristics of a pneumatic tire. This consists of an integrated model for a three-dimensional membrane ring and brush models. This model is more complex than conventional models, which resulted in increased computational costs. Because the tire dynamic characteristics affects the contact pressure, the deformation of the tread rubber caused an interaction of forces. Therefore, the tread ring deformation was defined as a summation of the mode basis functions, which expressed vibrational behavior. This approximation linearizes the energy function, which helped calculate the potential energy of the tire structure using a theoretical equation without discretization.
Journal Article

Technological Stability of the Liner in a Separable Metal Composite Pressure Vessel

Abstract The article considers one of the possible mechanisms of loading the solidity of a cylindrical metal composite high-pressure vessel (MC HPV). This mechanism manifests itself as delamination of a thin-walled metal shell (liner) from a more rigid composite shell causing local buckling. A similar effect can be detected in the manufacturing process of MC HPV, when the composite shell is formed by winding with tension a carbon fiber-reinforced plastic tape on the liner. Pressure transfer from the composite shell to the liner is carried out by the method of temperature analogy, that is, by cooling the composite shell, thermally insulated from the liner. To solve the problem of externally confined liner local buckling an approach is proposed, which is based on three points: the introduction of local technological deviations inherent in actual structures, the determination of the general stress-strain state, and a real-time deforming.
Journal Article

Ducted Fuel Injection versus Conventional Diesel Combustion: An Operating-Parameter Sensitivity Study Conducted in an Optical Engine with a Four-Orifice Fuel Injector

Abstract Ducted fuel injection (DFI) has been shown to attenuate engine-out soot emissions from diesel engines. The concept is to inject fuel through a small tube within the combustion chamber to enable lower equivalence ratios at the autoignition zone, relative to conventional diesel combustion. Previous experiments have demonstrated that DFI enables significant soot attenuation relative to conventional diesel combustion for a small set of operating conditions at relatively low engine loads. This is the first study to compare DFI to conventional diesel combustion over a wide range of operating conditions and at higher loads (up to 8.5 bar gross indicated mean effective pressure) with a four-orifice fuel injector. This study compares DFI to conventional diesel combustion through sweeps of intake-oxygen mole fraction (XO2), injection duration, intake pressure, start of combustion (SOC) timing, fuel-injection pressure, and intake temperature.
Journal Article

Mathematical Model of Heat-Controlled Accumulator (HCA) for Microgravity Conditions

Abstract It is reasonable to use a two-phase heat transfer loop (TPL) in a thermal control system (TCS) of spacecraft with large heat dissipation. One of the key elements of TPL is a heat-controlled accumulator (HCA). The HCA represents a volume which is filled with vapor and liquid of a single working fluid without bellows. The pressure in a HCA is controlled by the heater. The heat and mass transfer processes in the HCA can proceed with a significant nonequilibrium. This has implications on the regulation of TPL. This article presents a mathematical model of nonequilibrium heat and mass transfer processes in an HCA for microgravity conditions. The model uses the equations of mass and energy conservation separately for the vapor and liquid phases. Interfacial heat and mass transfer is also taken into account. It proposes to use the convective component k for the level of nonequilibrium evaluation.
Journal Article

Multicriteria Optimization, Sensitivity Analysis, and Prediction of Bond Characteristics of Vacuum Diffusion Bonded Aero Engine Ti6Al4V Alloy Joints

Abstract Joining titanium (Ti) alloys with conventional processes is difficult due to their complex structural properties and ability of phase transformation. Concerning all the difficulties, diffusion bonding is considered as an appropriate process for joining Ti alloys. Ti6Al4V, which is an α+β alloy widely used for aero engine component manufacturing, is diffusion bonded in this investigation. The diffusion bonding process parameters such as bonding temperature, bonding pressure, and holding time were optimized to achieve desired bonding characteristics such as shear strength, bonding strength, bonding ratio, and thickness ratio using response surface methodology (RSM). Empirical relationships were developed for the prediction of the bond characteristics, and sensitivity analysis was performed to determine the increment and decrement tendency of the shear strength with respect to the bonding parameters.
Journal Article

Gas Metal Arc Welding Process Parameter Optimization to Reduce Porosity Defect in a Longitudinal Seam Welding of Pressure Vessels

Abstract Pressure vessels are critical equipment used in industries for storing liquids or gases at a pressure significantly different from ambient conditions. Porosity is one of the major weld defects in pressure vessels that leads to failure during inspection and as well as during its service. Gas Metal Arc Welding (GMAW) process is widely used in industries to fabricate pressure vessels using carbon steel “IS 2062 E250BR” material for storing compressed air. The main objective of this article is to reduce the porosity defect in the longitudinal seam (LS) welding of the pressure vessels. Detailed analysis is carried out to identify the parameters which are influencing the porosity defect. Central Composite Design (CCD) and Response Surface Methodology (RSM) approaches are used to find the optimum value of the weld parameters which produce weld without porosity or any major defects in the pressure vessel.
Journal Article

Experimental Analysis of Gasoline Direct Injector Tip Wetting

Abstract At gasoline direct injection, light-duty engines operated with homogeneous, stoichiometric combustion mode, particulate emissions are mainly formed in diffusion flames that result from prior fuel wall wetting. Besides the piston, liner, and intake valves, the injector tip acts as a main particulate source when fuel is adhered to it during an injection. Hence, this injector tip fuel wetting process and influences on this process need to be analyzed and understood to reduce engine-out particulate emissions. The present work analyzes the injector tip wetting process in an experimental way with a high-speed and high-resolution measurement system at an optically accessible pressure chamber. The performed measurements reveal that injector tip wetting can occur during the complete injection event by different mechanisms. Large spray cone angles at start and at end of injection or distortions of the spray result in direct contact of the fuel spray with the step-hole wall.
Journal Article

Numerical Study of Pore Size and Distribution Effects on Gasoline Particulate Filter Performance

Abstract The improved brake thermal efficiency of Gasoline Direct Injection (GDI) engines is accompanied by a significant increase in Particulate Matter (PM) mass and higher Particulate Number (PN) emissions as compared to (multi)Port Fuel Injected (PFI) engines. Gasoline particulate filters (GPFs) with high filtration efficiency and low backpressure will be required to meet the future, stringent PM/PN regulations. A two-dimensional (2D) CFD study was performed to determine the effects of pore size and distribution on the interdependent performance parameters of filtration efficiency and backpressure for clean GPFs. Simulation results show an on linear change infiltration efficiency as the pore size distribution tightens and determine a recommended distribution range, controlling the quantity of small-sized pores. Pore size distributions beyond this recommended range can cause a filtration performance loss or intolerable backpressure penalty for the GPF.
Journal Article

Torque and Pressure CFD Correlation of a Torque Converter

Abstract A torque converter was instrumented with 29 pressure transducers inside five cavities under study (impeller, turbine, stator, clutch cavity between the pressure plate and the turbine shell). A computer model was created to establish correlation with measured torque and pressure. Torque errors between test and simulation were within 5% and K-Factor and torque ratio errors within 2%. Turbulence intensity on the computer model was used to simulate test conditions representing transmission low and high line pressure settings. When turbulence intensity was set to 5%, pressure simulation root mean square errors were within 11%-15% for the high line pressure setting and up to 34% for low line pressure setting. When turbulence intensity was increased to 50% for the low line pressure settings, a 6% reduced root mean square error in the pressure simulations was seen.
Journal Article

A Multiscale Cylinder Bore Honing Pattern Lubrication Model for Improved Engine Friction

Abstract Three-dimensional patterns representing crosshatched plateau-honed cylinder bores based on two-dimensional Fast Fourier Transform (FFT) of measured surfaces were generated and used to calculate pressure flow, shear-driven flow, and shear stress factors. Later, the flow and shear stress factors obtained by numerical simulations for various surface patterns were used to calculate lubricant film thickness and friction force between piston ring and cylinder bore contact in typical diesel engine conditions using a mixed lubrication model. The effects of various crosshatch honing angles, such as 30°, 45°, and 60°, and texture heights on engine friction losses, wear, and oil consumption were discussed in detail. It is observed from numerical results that lower lubricant film thickness values are generated with higher honing angles, particularly in mixed lubrication regime where lubricant film thickness is close to the roughness level, mainly due to lower resistance to pressure flow.
Journal Article

Prediction and Control of Response Time of the Semitrailer Air Braking System

Abstract The response time of the air braking system is the main parameter affecting the longitudinal braking distance of vehicles. In this article, in order to predict and control the response time of the braking system of semitrailers, an AMESim model of the semitrailer braking system involving the relay emergency valve (REV) and chambers was established on the basis of analyzing systematically the working characteristics of the braking system in different braking stages: feedback braking, relay braking, and emergency braking. A semitrailer braking test bench including the brake test circuit and data acquisition system was built to verify the model with typical maneuver. For further evaluating the semitrailer braking response time, an experiment under different control pressures was carried out. Experimental results revealed the necessity of controlling the response time.
Journal Article

Tire Side Force Characteristics with the Coupling Effect of Vertical Load and Inflation Pressure

Abstract The tire vertical load and inflation pressure have great influence on tire steady- and non-steady-state characteristics and, consequently, on the vehicle handling and stability. The objective of this article is to reveal the coupling effect of tire vertical load and inflation pressure on tire characteristics and then introduce an improved UniTire side force model including such coupling effect through experimental and theoretical analysis. First, the influence of the tire vertical load and inflation pressure on the tire characteristics is presented through experimental analysis. Second, the theoretical tire cornering stiffness and lateral relaxation length model are introduced to study the underlying mechanism of the coupling effect. Then, an improved UniTire side force model including the coupling effect of tire vertical load and inflation pressure is derived. Finally, the proposed improved UniTire side force model is validated through tire steady-state and transient data.
Journal Article

Comparative Performance of 12 Crankcase Oil Mist Separators

Abstract Closed crankcase ventilation (CCV) systems are required in most automotive markets in order to meet emissions regulations. Such systems usually require a separator to recover oil and return it to the sump. Many end users fit improved separators in order to reduce intake/aftercooler contamination with soot/oil. This study measured clean and wet pressure drop and filter capture efficiency in 12 different crankcase oil mist separators which are commonly used for either original equipment (OE) or aftermarket fitment to passenger vehicles and four-wheel drives (≤200 kW). The filters tested spanned three different size/rating classes as well as included both branded and unbranded (imitation) models. In addition to filters, separators (often termed “catch cans”) and an OE cyclone separator were also examined. Testing was performed under controlled laboratory conditions using methods equivalent to previous work and current mist filter test standards.
Journal Article

Gasoline Particulate Filter Wall Permeability Testing

Abstract With the introduction of particulate matter emissions regulations for gasoline engines, most car manufacturers are considering using gasoline particulate filters (GPFs). Although very similar to diesel particulate filters (DPFs), GPFs operate at higher temperatures and generally have thinner monolith walls. In order to estimate the pressure loss through the filter, filter wall permeability is needed. This presents a number of challenges since wall losses cannot be efficiently isolated from other losses in a full-scale filter or filter core. Thin wall wafers have been used for DPF characterization. However, GPF wafers are generally thinner, which makes the testing less straightforward. This article presents a novel effective methodology for estimation of GPF wall permeability using thin wafers cut from the filter monolith. Both cold and hot flow permeabilities can be estimated, which allows to account for the change of apparent permeability due to the slip effect.
Journal Article

Uncertainty Assessment of Octane Index Framework for Stoichiometric Knock Limits of Co-Optima Gasoline Fuel Blends

Abstract This study evaluates the applicability of the Octane Index (OI) framework under conventional spark ignition (SI) and “beyond Research Octane Number (RON)” conditions using nine fuels operated under stoichiometric, knock-limited conditions in a direct injection spark ignition (DISI) engine, supported by Monte Carlo-type simulations which interrogate the effects of measurement uncertainty. Of the nine tested fuels, three fuels are “Tier III” fuel blends, meaning that they are blends of molecules which have passed two levels of screening, and have been evaluated to be ready for tests in research engines. These molecules have been blended into a four-component gasoline surrogate at varying volume fractions in order to achieve a RON rating of 98. The molecules under consideration are isobutanol, 2-butanol, and diisobutylene (which is a mixture of two isomers of octene). The remaining six fuels were research-grade gasolines of varying formulations.
Journal Article

Improving Hole Expansion Ratio by Parameter Adjustment in Abrasive Water Jet Operations for DP800

Abstract The use of Abrasive Water Jet (AWJ) cutting technology can improve the edge stretchability in sheet metal forming. The advances in technology have allowed significant increases in working speeds and pressures, reducing the AWJ operation cost. The main objective of this work was to determine the effect of selected AWJ cutting parameters on the Hole Expansion Ratio (HER) for a DP800 (Dual-Phase) Advanced High-Strength Steel (AHSS) with s0 = 1.2 mm by using a fractional factorial design of experiments for the Hole Expansion Tests (HET). Additionally, the surface roughness and residual stresses were measured on the holes looking for a possible relation between them and the measured HER. A deep drawing quality steel DC06 with s0 = 1.0 mm was used for reference. The fracture occurrence was captured by high-speed cameras and by Acoustic Emissions (AE) in order to compare both methods.
Journal Article

Passive Flow Control on a Ground-Effect Diffuser Using an Inverted Wing

Abstract In this experimental and computational study a novel application of aerodynamic principles in altering the pressure recovery behavior of an automotive-type ground-effect diffuser was investigated as a means of enhancing downforce. The proposed way of augmenting diffuser downforce production is to induce in its pressure recovery action a second pressure drop and an accompanying pressure rise region close to the diffuser exit. To investigate this concept with a diffuser-equipped bluff body, an inverted wing was situated within the diffuser flow channel, close to the diffuser exit. The wing’s suction surface acts as a passive flow control device by increasing streamwise flow velocity and reducing static pressure near the diffuser exit. Therefore, a second-stage pressure recovery develops along the diffuser’s overall pressure recovery curve as the flow travels from the diffuser’s low pressure, high velocity inlet to its high pressure, low velocity exit.
Journal Article

Development and Validation Procedure of a 1D Predictive Model for Simulation of a Common Rail Fuel Injection System Controlled with a Fuel Metering Valve

Abstract A fully predictive one-dimensional model of a Common Rail injection apparatus for diesel passenger cars is presented and discussed. The apparatus includes high-pressure pump, high-pressure pipes, injectors, rail and a fuel-metering valve that is used to control the rail pressure level. A methodology for separately assessing the accuracy of the single submodels of the components is developed and proposed. The complete model of the injection system is finally validated by means of a comparison with experimental high-pressure and injected flow-rate time histories. The predictive model is applied to examine the fluid dynamics of the injection system during either steady-state or transient operations. The influence of the pump delivered flow-rate on the rail-pressure time history and on the injection performance is analysed for different energizing times and nominal rail pressure values.