Search Results

This article first analyzes the driving characteristics of vehicles in Intelligent Vehicle Infrastructure Cooperative Systems, summarizing and proposing four characteristics, including a wider field of view, easier lane-changing conditions, less speed loss, and more flexible cooperation among vehicles than in the traditional lane-changing situation. Analysis and comparison of the update sequence in cellular automata based on the four characteristics, namely, synchronous update and asynchronous update, longitudinal vehicle sequence update and random update, horizontal express vehicle priority, and random priority. Three kinds of cooperative lane changes unique to the vehicle-road collaborative environment were discovered, which are dangerous lane change, slow car giving way, and space redistribution. The three kinds of coordinated lane change were simulated and compared with the basic diagram of the improved model and the traditional model.

Primary breakup of a liquid jet is a process of enormous complexity, involving interfacial dynamics, topology changes, and turbulence. In macro-scale simulations for practical problems, the primary breakup is usually too expensive to be fully resolved and thus is typically represented by phenomenological models. The recent advancement of numerical methods and computer power enables large-scale high-fidelity simulations of primary breakup. The high-level details provided by simulation can be used to verify the assumptions made in existing models and also to develop new models through both physics- or data-based approaches. The present paper will present the state-of-the-art high-fidelity simulation of the primary breakup of a gasoline surrogate jet. The simulation parameters were chosen following the Engine Combustion Network (ECN) ``Spray G" conditions and thus are similar to realistic engine conditions.

The non-conventional diesel nozzles have attracted more and more attention for their ability to promote jet breakup. In the present study, the internal nozzle flow and jet breakup relying on the convergent-divergent nozzle are investigated by combining the cavitation model and LES model with Multi-Fluid-Quasi-VOF model based on the OpenFOAM code. This is a novel method for which the interphase forces caused by the relative velocity of gas and liquid can be taken into account while sharpening the gas-liquid interface, which is able to accurately present the evolution processes of cavitation and jet breakup. Primarily, the numerical model was verified by the mass flow rate, spray momentum flux, discharge coefficient and effective jet velocity of the prototype Spray D nozzle from the literature.

ADAMS, SIMULINK, and ADAMS-SIMULINK co-simulation models of component test systems, Multi-Axis-Simulation-Table (MAST) systems, and spindle-coupled vehicle testing system (MTS 329) were created. In the ADAMS models, the mechanical parts, joints, and bushings were modeled. Hydraulic and control elements were absent. The SIMULINK models modeled control and hydraulic elements including actuator dynamics, servo valve dynamics, closed loop control, three-variable control, matrix control, and coordinate transformation. However, the specimen had to be simplified due to the limitation of SIMULINK software. The ADAMS-SIMULINK co-simulation models considered hydraulic and control components in the SIMULINK portion and mechanical components in ADAMS portion. The interaction between the ADAMS and SIMULINK portions was achieved using ADAMS/Control.

This paper presents the latest development of using an integrated modeling approach to estimate the statistical ranges of key vehicle dynamics performance in the early design phase. The virtual analytical tools predict the statistical confidence interval for specified ride and handling (R&H) metrics to enable a robust design by concurrently simulating the dimensional tolerance of the structural parts as well as the compliance variation. The compliance variation can be defined as load deflection properties of bushings as well as vehicle weight effects on preload. The model can then be used to better represent real world customer experience, allowing prediction of performance ranges relative to targets. In order to better predict these targets, measurements of physical vehicles were made and compared to the model to reveal the actual interactions relative to the theoretical.

During the vehicle development process, dimensional variation simulation modeling has been applied extensively to estimate the effects of build variation on the final product. Traditional variation simulation methods analyze the tolerance inputs of structural components, but do not account for any compliance effects due to stiffness variation in tuning components, such as bushings, springs, isolators, etc., since both product and process variation are simulated based on rigid-body assumptions. Vehicle performance objectives such as ride and handling (R&H) often involve these compliance metrics. The objective of this paper is to present a method to concurrently simulate the tolerance from the structural parts as well as the variability of compliance from the tuning components through an integration package. The combination of these two highly influential effects will allow for a more accurate prediction and assessment of vehicle performance.

Dimensional variation simulation is a computer aided engineering (CAE) method that analyzes the statistical efforts of the component variation to the quality of the final assembly. The traditional tolerance analysis method and commercial CAE software are often based on the assumptions of the rigid part assembly. However, the vehicle functional attributes, such as, ride and handling, NVH, durability and reliability, require understanding the assembly quality under various dynamic conditions while achieving vehicle dimensional clearance targets. This paper presents the methods in evaluating and analyzing the impacts of the assembly variations for the vehicle dynamic performance. Basic linear tolerance stack method and advanced study that applies various CAE tools for the virtual quality analysis in the product and process design will be discussed.

A HCCI engine has been run at different operating boundaries conditions with fuels of different RON and MON and different chemistries. The fuels include gasoline, PRF and the mixture of PRF and ethanol. Six operating boundaries conditions are considered, including different intake temperature (Tin), intake pressure (Pin) and engine speed. The experimental results show that, fuel chemistries have different effect on the combustion process at different operating conditions. It is found that CA50 (crank angle at 50% completion of heat release) shows no correlation with either RON or MON at some operating boundaries conditions, but correlates well with the Octane Index (OI) at all conditions. The higher the OI, the more the resistance to auto-ignition and the later is the heat release in the HCCI engine. The operating range is also correlation with the OI. The higher the OI, the higher IMEP can reach.

The influence of boost pressure (Pin) and fuel chemistry on combustion characteristics and performance of homogeneous charge compression ignition (HCCI) engine was experimentally investigated. The tests were carried out in a modified four-cylinder direct injection diesel engine. Four fuels were used during the experiments: 90-octane, 93-octane and 97-octane primary reference fuel (PRF) blend and a commercial gasoline. The boost pressure conditions were set to give 0.1, 0.15 and 0.2MPa of absolute pressure. The results indicate that, with the increase of boost pressure, the start of combustion (SOC) advances, and the cylinder pressure increases. The effects of PRF octane number on SOC are weakened as the boost pressure increased. But the difference of SOC between gasoline and PRF is enlarged with the increase of boost pressure. The successful HCCI operating range is extended to the upper and lower load as the boost pressure increased.

The concept of design for six sigma (DFSS) offers a framework to design a product and process right the first time. In general, Taguchi's robust design method has been widely adapted in design optimization, which is a critical phase in any DFSS projects. The objective of the paper is to develop an advanced strategy in selecting an optimized product design and manufacturing process that should be insensitive to various multivariate variation patterns of the multi-stage manufacturing system. A Monte Carlo variation simulation based method is presented that integrates Mohalanobis Distance (MD) method, a discriminant analysis technique, to analyze the manufacturing variation patterns detected by using the multivariate statistical tool, such as principal component analysis (PCA). The proposed method will be explained with an example of an automotive assembly.

Manufacturing variation effects on the fit and function of a finished product, e.g., a vehicle, can be analyzed into designs using 3D dimensional simulation method. In an effort to reduce the predicted process variation for improving the dimensional quality during design phase, an integrated analytical approach is presented using robust design and variation simulation method that leads to select the optimal product datum and locating schemes for the process design. The Taguchi’s robust design and ANOVA (analysis of variance) are used in the algorithm to generate meaningful information about the effects of several processes simultaneously on the variability of the measured products. The application of the proposed method in process control with the dynamic factor, such as powertrain roll, is also discussed.

The effects of cooled EGR on combustion and emission characteristics in HCCI operation region was investigated on a single-cylinder diesel engine, which is fitted with port injection of DME and methanol. The results indicate that EGR rate can enlarge controlled HCCI operating region, but it has little effect on the maximum load of HCCI engine fuelled with DME/methanol dual-fuels. With the increase of EGR rate, the main combustion ignition timing (MCIT) delays, the main combustion duration (MCD) prolongs, and the peak cylinder pressure and the peak rate of heat release decreases. Compared with EGR, DME percentage has an opposite effect on HCCI combustion characteristics. The increase of indicated thermal efficiency is a combined effect of EGR rate and DME percentage. Both HC and CO emissions ascend with EGR rate increasing, and decrease with DME percentage increasing. In normal combustion, NOX emissions are near zero.

The effects of Exhaust Gas Recirculation (EGR) and octane number of PRF fuel on combustion and emission characteristics in HCCI operation were investigated. The results show that EGR could delay the ignition timing, slow down the combustion reaction rate, reduce the pressure and average temperature in cylinder and extend the operation region into large load mode. With the increase of the fuel/air equivalence ratio or the fuel octane number (ON), the effect of EGR on combustion efficiency improves. With the increase of EGR rate, the combustion efficiency decreases. The optimum indicated thermal efficiency of different octane number fuels appears in the region of high EGR rate and large fuel/air equivalence ratio, which is next to the boundary of knocking. In the region of high EGR rate, HC emissions rise up sharply as the EGR rate increases. With the increase of octane number, this tendency becomes more obvious.

By mixing iso-octane with octane number 100 and normal heptane with octane number 0, it was possible to obtain a PRF fuel with octane rating between 0 and 100. The influence of PRF fuel’s octane number on the combustion characteristics, performance and emissions character of homogeneous charge compression ignition (HCCI) engine was investigated. The experiments were carried out in a single cylinder direct injection diesel engine. The test results show that, with the increase of the octane number, the ignition timing delayed, the combustion rate decreased, and the cylinder pressure decreased. The HCCI combustion can be controlled and then extending the HCCI operating range by burning different octane number fuel at different engine mode, which engine burns low octane number fuel at low load mode and large octane number fuel at large load mode. There exists an optimum octane number that achieves the highest indicated thermal efficiency at different engine load.

Homogeneous charge compression ignition (HCCI) is considered as a high efficient and clean combustion technology for I.C. engines. Methanol is a potential fuel for HCCI combustion. In this research, a single cylinder diesel engine was applied to HCCI operation. Methanol and dimethyl ether (DME) were fueled to the engine by fuel injection system with an electric controlled port in dual fuel mode. The results show that the stable HCCI operation of DME/methanol can be obtained over a quite broad speed and load region. And compared with higher speeds, the load region is even wider at low engine speed. E.g., at the engine speed of 1000 r/min, the maximum indicated mean effective pressure(IMEP) can reach 0.77 MPa, while at 2000r/min it is 0.53 MPa. Both DME and methanol influence HCCI combustion strongly, and by regulating DME/methanol proportions the HCCI combustion process could be controlled effectively.