of ENGINEERING-HUNEDOARA, ROMANIA 115 1. THE INFLUENCES OF AIR TEMPERATURE ON THE INTAKE PROCESS BY NUMERICAL SIMULATION

Dan Moldovanu, Florin, Bogdan Varga
unpublished
The intake process of an internal combustion engines is one of the most important. The importance of the intake process study is underscored by the need to generate superior engine performance, but also directly related to reducing emissions. There are a multitude of parameters that influence the intake process (functional, constructive, and environmental) that involving a series of complex studies and experiments. One of the easiest ways for researchers is to use computer modeling and
more » ... n, which can provide early indications and new directions in the optimization of the study. This paper shows the influence of ambient temperature on the intake process of an internal combustion engine. The turbulence kinetic energy of the intake air was analyzed. KEYWORDS: air intake process, air temperature, turbulence kinetic energy, computer simulation INTRODUCTION Functioning of the internal combustion engine is well established by the four major functional processes well known as the "motor cycle": intake, compression, combustion and exhaust. Each of these processes has their importance, in order to increase overall energy efficiency of the internal combustion engine. And further, each process is influenced by several internal and external factors: physically, functional, constructive and nature of fuel [1,3,9]. The importance of cylinder air-charging process is given the necessity to fill the engine cylinder as large is possible quantity of fresh air, to achieve a greater amount of air-fuel mixture. As amount of air-fuel mixture will be higher, both functional motor performance (power) and dynamic characteristics will be higher [3]. Unfortunately, the structural characteristics and design of modern internal combustion engines have a number of features that have immediate effects on the quality of the filling process. An ideal process of filling the engine cylinder with air should provide a laminar flow air intake for the entire length of the route. In practice, this is not possible, and evens more; the pattern of airflow through intake system (laminar or turbulent) is influence by the air inlet temperature. Air intake temperature influences (by specific physical processes) the parameters characterizing air (density), which further influences the degree of charging of the engine cylinder. With few exceptions (variable tracks of the air inlet pipes or design characteristics of air filter-[7]), the design of air intake system is well determined, specifically designed to each specific engine that equips it. Specific restrictions related to the design of the air intake system occurred lately due to application of modern concepts of "downsizing", concepts that make intake systems to have a design process to high achievements and engine specification implementation. Using computer simulation to design engine's components, systems and study of functional processes is a tool widely used by researchers worldwide [2,3-8,10]. The main advantages offers using computer simulation consist in lower construction costs prototypes; develop an idea into a much shorter time than traditional experimental procedures; propose, conduct and analyze a variety of scenarios related to the characteristics of studied phenomena, etc. For the simulation of fluid dynamic phenomena simulation software packages known collectively as CFD (Computer Fluid Dynamics) are used. Basic mathematical apparatus used in the study of fluid dynamic equations are based on Navier-Stokes equations. Using Einstein notation the equations are written as follows:
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