Search Results

Abstract With the use of the stepped surface of the friction pairs of the stepped bearings (SB) in the high-speed centrifugal pumps, its liquid film thickness is suddenly changed and it was discontinuously distributed in the direction of motion of pump. To ensure the continuity of the liquid film thickness and enhance the lubrication efficiency of the pump, based on the lubrication model of the SB, two other structures of the inclined surfaces [inclined bearings (IB)] and curved surfaces [curved bearings (CB)] used to replace stepped surfaces of the SB are investigated, respectively. Under the same conditions of the minimum thickness of the liquid film and initial dimensions of the sliding friction pairs, the influence of both the thickness ratio (α) of the liquid film and dimension ratio (β) in the direction of motion of SB, IB, and CB on the bearing capacity and friction coefficient of the liquid film are simulated and analyzed, respectively.

Abstract In view of the combustion efficiency and emission performance, various new clean combustion modes put forward higher requirements for the performance of the fuel injection system, and the cavitating two-phase flow characteristics in the injector nozzle have a significant impact on the spray atomization and combustion performance. This article comprehensively discusses and summarizes the factors that affect cavitation and the effectiveness of cavitation, and presents the research status and existent problems under each factor. Among them, viscosity factors are a hot research topic that researchers are passionate about, and physical properties factors still have the value of further in-depth research. However, the importance of material surface factors ranks last since the nozzle material was determined. Establishing a more comprehensive cavitation–atomization model considering various factors is the focus of research on cavitation phenomena.

Abstract Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance.

Abstract Vehicle vibration is the key consideration in the early stage of vehicle development. The most dynamic system in a vehicle is the powertrain system, which is a source of various frequency vibration inputs to the vehicle. Mostly for powertrain mounting system design, only the uncoupled powertrain system is considered. However, in real situations, other subsystems are also attached to the powertrain unit. Thereby, assuming only the powertrain unit ignores the dynamic interactions among the powertrain and other systems. To address this shortcoming, a coupled powertrain and driveline mounting system problem is formulated and examined. This 16 DOF problem is constructed around a case of a front engine-based powertrain unit attached to the driveline system, which as an assembly resting on other systems such as chassis, suspensions, axles, and tires.

Abstract Optimization is essential in real-life mechanical engineering problems that mostly are nonlinear, depend on mixed decision variables, and are usually subject to constraints. However, most of the studied problems are modelled assuming continuous variables. A limited number of studies have been devoted to cases with mixed variables. Moreover, there is a lack of algorithm treating mixed variable problems properly. This article introduces a hybrid algorithm that can handle constrained problems depending on continuous or mixed variables. The proposed algorithm combines two meta-heuristics, Jaya and particle swarm optimization (PSO). PSO is one of the most popular methods to solve nonlinear problems, and Jaya is a novel parameter-free optimization algorithm. This new hybrid optimization algorithm is proposed in order to improve the convergence speed and to investigate what improvements it will bring to optimization problem solutions.

Abstract Under the influence of the interactions between the vibratory drum/wheel and deformable terrains, the ride comfort of the soil compactors is greatly affected. Therefore, the isolation systems of the cab and driver’s seat of the soil compactors have been researched and developed to improve ride comfort. Based on the existing research results, this study provides an overview of the development of the isolation systems of the cab and driver’s seat of the soil compactors. The research result shows that the cab isolations used by the semi-active hydraulic mounts (SHM) or semi-active hydraulic-pneumatic mounts (SHPM) can greatly improve the driver’s ride comfort and control the cab shaking, whereas the driver’s seat suspension embedded by the negative stiffness structure (NSS) strongly improves the driver’s ride comfort.

Abstract The use of converging-diverging (C-D) variable area nozzle (VAN) in military aeroengines is now common, as it can give optimal expansion and control over engine back pressure, for a wide range of engine operations. At higher main combustion temperatures (desired for supercruise), an increase in the nozzle expansion ratio is needed for optimum performance. But changes in the nozzle throat and exit areas affect the visibility of engine hot parts as the diverging section of the nozzle is visible for a full range of view angle from the rear aspect. The solid angle subtended by engine hot parts varies with change in visibility, which affects the aircraft infrared (IR) signature from the rear aspect. This study compares the performances of fixed and variable area nozzles (FAN and VAN) in terms of engine thrust and IR signature of the engine exhaust system in the boresight for the same increase in combustion temperature.

Abstract Gasoline compression ignition (GCI) is a promising combustion technology that can help the commercial transportation sector achieve operational flexibility and meet upcoming criteria pollutant regulations. However, high-pressure fuel injection systems (>1000 bar) are needed to enable GCI and fully realize its benefits compared to conventional diesel combustion. This work is a continuation of previous durability studies that identified three key technical risks after running gasoline-like fuel through a heavy-duty, common rail injection system: (i) cavitation damage to the inlet check valve of the high-pressure pump, (ii) loss of injector fueling capacity, (iii) cavitation erosion of the injector nozzle holes. Upgraded hardware solutions were tested on a consistent 400- to 800-hour NATO durability cycle with the same gasoline-like fuel as previous studies. The upgraded pump showed no signs of abnormal wear or cavitation damage to the inlet check valve.

Abstract The objective of this work is to analyze the signal of a piezoelectric washer installed under the spark plug and to compare the combustion metrics evaluated with such signal to the indexes from a standard piezoelectric sensor for the in-cylinder pressure measurement, considered as the reference. In the first part of the article, the spectrum analysis of the piezoelectric washer pressure trace is proposed. It is demonstrated how such a signal can be used to measure the main combustion and knock indexes. Nevertheless, due to the intrinsic characteristics of the system, the knock index evaluated from the raw pressure trace cannot be directly used to estimate the instantaneous knock intensity. For this reason, a model-based algorithm for Real-Time (RT) application is developed to calculate a corrective factor of the high-frequency content of the signal.

Abstract Fretting is a surface damage phenomenon and is typically observed at the contact interfaces such as bolted, gasketed joints, and the like. It occurs due to the combined effect of normal and tangential loads, which produces a small-amplitude relative sliding between two components that are held together using clamping forces. Fretting-related failures are also observed in multiple components of an internal combustion engine. This article presents the fretting fatigue damage evaluation of a single layer head gasket using a relative new approach, i.e., deviatoric strain amplitude-based method, further combined with the Ding’s empirical parameter D fret2. Corresponding fretting damage results are compared with the traditional approach based on the Ruiz’s parameter F1.

Abstract The gear whine in the electric drive system of an electric vehicle is important and remains a challenge in developing novel electric vehicles. A gearbox dynamic model is established, and the effects of modification parameters on the sound pressure level, transmission error, and contact stress of the gear pair are introduced to reduce the gear whine. A multi-objective optimization study of four modification variables under multiple torque conditions is carried out by using transmission error and maximum contact stress as the objective functions. The eclectic programming method is imported to solve the convergence problem of multi-objective optimization. The influence of modification variables on objective functions is studied by establishing an approximate model of the optimal Latin hypercube design.

Abstract In real-life mechanisms, the design parameters differ from their theoretical values. This difference is due to the manufacturing tolerances of link dimensions and revolute joints of mechanisms. In this article, the effect of link dimensions manufacturing tolerances and joints clearance on the kinematic and dynamic performances of a planar mechanism is studied. A slider-crank mechanism with two joint clearances is considered as a case study. Furthermore, an analytical method based on the partial derivatives is used to determine the mathematical equation representing the kinematic errors of the mechanism. This error depends on the manufacturing tolerances of link dimensions and revolute joints of the mechanisms. The Lagrangian equation is adopted to define the mathematical expression of the mechanism motion. Two objectives are considered regarding the acceleration error and the dynamic performance.

Abstract Due to their high strength and good flexibility, wire ropes are widely used in various intense applications. A wire rope will present complex wave mechanics, especially under impact conditions. In this article, wire ropes (steel core rope and hemp core rope alternately twisted) were used to study the wave dynamic response of steel wire ropes with preload shock. The transmission law of wire rope shock waves was obtained through actual measurements. The results showed that the compression wave and shear wave were generated and propagated along the rope after impact. The conduction of shear waves had significant reflection characteristics, and the reflected waves overlapped with each other. The conduction velocity of the impact shear wave of the steel core wire rope increased with increasing pretension. The peak tension caused by impact decayed exponentially.

Abstract Stress-based sheet metal fatigue near nuts welded to thin sheets is one of the necessary design processes for car bodies. In this investigation, the influence of the attachment contact on the localized fatigue mechanism is examined through finite element (FE) models and controlled fatigue experiments. First, a fatigue experimental setup, which includes a thin-sheet closed-hat section with a weld nut bolted to a thick attachment piece, is designed to minimize the uncertainty of the influence of the fixtures on the experimental results. The experiments are carried out on 0.9- and 1.0-mm thick hat sections with a square weld nut under force control conditions with complete reversed loading. Due to the contact, the test specimen performs as a bilinear spring that has a lower stiffness in the upstroke direction when compared to the downstroke direction where full contact of the attachment occurs with the hat section.

Abstract The thermal error of ball screw is the main factor affecting the accuracy of machine tool. Establishing an accurate thermal error model of ball screw is the key to compensate the error of machine tool. The ultimate goal of the research work in this article is to develop a comprehensive modeling method that can predict the temperature rise and thermal error of ball screw. In view of the problem that the reciprocating motion of ball screw nut was ignored in the traditional thermal error model, a transient thermal-structural coupling model considering the actual working conditions was proposed. ANSYS parametric design language (APDL) was used to set the ball screw nut as the moving heat source load, and the displacement-time relationship between the ball screw nut and the ball screw was defined. The temperature and thermal deformation distribution of the ball screw under the action of the bearing and the heat source of the ball screw nut were simulated.

Abstract A new approach of the crankpin bearing (CB) surface designed by different partial textures (PTs) with spherical dimples (SDs), conical dimples (CDs), or circular-cylindrical dimples (CCDs) is proposed to enhance the lubrication performance and reduce the friction power loss of engines. To assess the effect of the geometric dimensions of different PTs, such as the distribution density, depth, and shape of dimples on the lubrication performance and friction power loss (LP-FPL), a hydrodynamic model of the engine’s CB lubrication is then built. Then a genetic algorithm (GA) developed in MATLAB software is applied for optimizing the geometric dimensions of the PTs to further improve the LP-FPL. Both the oil film pressure and friction force of the CB are chosen as the objective functions to evaluate the LP-FPL of engines.

Abstract In today’s era, due to increasing energy demands, it is necessary to make vehicles lightweight without affecting their strength. In order to achieve this, the subassemblies of the automobile should be optimized. Optimizing the product not only saves energy consumption but also reduces the material required for manufacturing and increases the overall performance of the product. Taking the same as the base, this article focuses on optimization of a straight bevel gear pair used in automotive differential and performing finite element analysis (FEA) to validate its results. FEA is carried out on the optimized bevel gear to check its durability, and topology optimization is performed on the optimized gear to reduce the mass. Finally, the optimized gear is checked for fatigue. For design optimization, nonlinear multi-objective problem is formulated with a number of teeth and modules as the design parameters.

Abstract Electrification has become less of a catchphrase and increasingly commonplace when discussing today’s locomotives. Engineers developing thermal management strategies (both component suppliers and system-level analysts) must be armed with effective tools to design and analyze essential components such as coolant pumps and study their behavior in an actual system. This study focuses on the analysis of twin screw pumps for cooling battery packs in hybrid and battery electric vehicles via three different approaches—experimental measurements, a one-dimensional (1D) thermodynamic chamber model, and a three-dimensional (3D) computational fluid dynamics (CFD) model. Experimental measurements are conducted to quantify the coolant’s volume flow rate and estimate hydraulic power consumption over a range of operating speeds and pump discharge pressures.

Abstract The article contains the results of operational investigations of deposit formation on external and internal surfaces of injector nozzles of the marine self-ignition engines during their operational use. The aim of this article is to introduce an image analysis method for global assessment of the quantity and quality of injector nozzle deposits in piston internal combustion engines. The components of medium-speed marine engines fueled with distillation and residual fuels were investigated. Digital images of new and used injector nozzles without deposits and with random deposits formed after natural operation on marine ships, respectively, were taken. Macro and microscopy images of external surfaces were taken in a shadowless tent and were illuminated with low-temperature lamps. The characteristic surfaces of the injector nozzles were virtually separated from the white background.

Abstract To enhance the lubrication performance of the crankpin bearing (CB) at the elastic hydrodynamic lubrication regime (EHLR), the spherical dimples (SD) of the partial textures (PT) is designed on the EHLR of the CB. Based on a hydrodynamic model of the slider-crank mechanism (SCM) combined with the CB lubrication and a multi-objective optimization program of the genetic algorithm (MOGA), the initial design parameters of PT including the depth hsij and the diameter Dij of each SD defined as chromosomes in the MOGA are then optimized to further enhance the CB’s lubrication performance. Three indexes of the oil film pressure p, friction force F f, and friction coefficient μ of the CB are chosen as the objective functions. The research results indicate that based on the optimal approach of the MOGA with its good stability and repeatability, the CB’s lubrication performance is remarkably improved by the optimal parameters in comparison with the initial parameters of the SD.