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The design of a complex system such as an automobile consists of the design of many highly complex subsystems. To address this level of complexity, traditionally the designers use a sequential and spiral design process with the goal of achieving a final feasible design that meets all of the competing and, sometimes, conflicting subsystem requirements. This process is highly influenced by designer's subjectivity and may lead to a suboptimal system design. Furthermore, the influence of subsystems on the overall design is reduced as the design progresses sequentially along the design spiral. This paper explores the development and applicability of an alternative Multidisciplinary Design Optimization (MDO) method, utilizing decomposition based optimization schemes. A simplified Synthesis Design Model (SDM) is developed that expresses the marketability of a standard midsize sedan on the U.S market based on fuel efficiency, curb weight and market price.

Understanding the physics and chemistry involved in diesel combustion, with its transient effects and the inhomogeneity of spray combustion is quite challenging. Great insight into the physics of the problem can be obtained when an in-cylinder computational analysis is used in conjunction with either an experimental program or through published experimental data. The main area to be investigated to obtain good combustion begins with the fuel injection process and the mean diameter of the fuel particle, injection pressure, drag coefficient, rate shaping etc. must be defined correctly. The increased NOx production and reduced power output found in engines running biodiesel in comparison to petrodiesel is believed to be related to the different fuel characteristics in comparison to petroleum based diesel. The fuel spray for biodiesel penetrates farther into the cylinder with a smaller cone angle. Also the fuel properties between biodiesel and petrodiesel are markedly different.

A zero dimensional computer code was developed to predict the performance of an spark ignition internal combustion fuel inducted engine. The code can be used to predict engine performance for automotive and racing applications. Expressions for turbulent flame speed were developed based on turbulent flame intensity and cylinder geometry. This turbulent flame intensity varies across the RPM span and was formulated based on a semi-empirical correlation study in a joint experimental/computational effort by the investigator which utilizes extensive dynamometer experimental results for automotive engine applications. In-cylinder wall temperatures are determined based on a newly developed empirical correlation which accounts for the influences of air-fuel ratio, compression ratio, spark timing and coolant temperature. Auto-ignition or knock is also predicted.

This study presents a computationally efficient numerical model that accurately predicts complex spray distribution and spray penetration for a direct injection compression ignition engine configuration. Experimental data obtained from available literature is used to construct a semi-empirical numerical model. A modified version of a multidimensional computer code KIVA-3V is used for the computations, with improved sub-models for varying mean droplet diameter, varying injection velocity and drop distortion and drag. Results show good agreement with the published in-cylinder experimental data for a Volkswagen 1.9 L turbo-charged direct injection under actual operating conditions.

With energy conservation and pollutant emission of paramount importance in today's society, it has emphasized the need for aerodynamic drag reduction in the automotive sector. Innovative ideas, better visualization, reduced time in the design process, and cost effective “computational testing” is all put together is the use of Computational Fluid Dynamics. In the present study the analysis of the complex flow structure around a bluff body is presented. The importance and advantages of the numerical simulations are discussed. The quality of the mesh is of great importance and the types of grid generation schemes are presented here. The shape of the rear of the body has a marked influence on the body drag. The importance of the back slant angle and its effect on the flow structure and in turn its effect on the drag force of the body is presented.

Previous research has shown that the homogeneous charge compression ignition (HCCI) combustion concept holds promise for reducing pollutants (i.e. NOx, soot) while maintaining high thermal efficiency. However, it can be difficult to control the operation of the HCCI engines even under steady state running conditions. Power density may also be limited if high inlet air temperatures are used for achieving ignition. A methodology using a small pilot quantity of diesel fuel injected during the compression stroke to improve the power density and operation control is considered in this paper. Multidimensional computations were carried out for an HCCI engine based on a CAT3401 engine. The computations show that the required initial temperature for ignition is reduced by about 70 K for the cases of the diesel pilot charge and a 25∼35% percent increase in power density was found for those cases without adversely impacting the NOx emissions.