Bir araç hava emiş sisteminin basınç kayıpları ve akış karakteristikleri açısından incelenmesi

In diesel engines, determination of pressure losses on air intake system is of crucial importance due to its detrimental effect on engine performance. Inefficiencies in performance present itself in elevated fuel consumption and/or high emmisions. Main effect of pressure losses in air intake system (AIS) is on compressor performance and combustion efficiency. The term AIS includes a major portion of an internal combustion engine's air path. In internal combustion engines, air path is basically a series of closed conduits that starts from grill opening that collects the fresh air to the exhaust tailpipe. AIS is the common name for system that comprises group of engine components which are responsible to deliver fresh air into the combustion chamber. Area of interest in this study is the series of components conveying air from atmosphere until compressor. Parts included in this study are the portion of AIS from atmosphere until compressor; a grill opening, dirty side ducts, air filter assembly, clean side ducts. When high pressure losses occur inside this system, AIS can accommodate less fluid flow under existing operating conditions to fulfil the demand of charged air into combustion chamber, compressor is forced to work in an inefficient operating point, resulting in extra load to turbine. Excessive load on turbine increases back pressure and hence, this phenomenon diminishes the combustion performance. To choose and calibrate the related parts of AIS, such as turbocharger, intake manifold, pressure losses from upstream should be determined correctly. However, this determination should be performed in early stages of design, leading to difficulties and complexity for test. Hence, employing a computational fluid dynamics (CFD) solver is more than a necessity to perform such evaluation. Yet again, to conduct a CFD study and to achieve reliable results in good correlation with real operating conditions, most of the cases require a validation procedure that includes testing. In this study a valid evaluation of the AIS performance is aimed. To achieve this goal, objectives that followed is; - Acquiring information about AIS system boundary conditions, - Building a CFD Model to model air filter's pressure loss characteristics, - Comparing pressure loss obtained in CFD model with ASTM (American Society for Testing and Materials) F778 Standard Air Permeability test results, - Building sector CFD models to evaluate the behavior of the filter element when installed into air filter assembly, xxii - Quantifying filter behavior with results of sector analyses and determining porous media tensor to represent filter element in complete AIS CFD model, - Building a full CFD model including all low pressure portion of the AIS and evaluating flow performance in terms of pressure loss and flow characteristics such as flow uniformity values on before and after mass flow rate sensor, filter element and at compressor inlet. - Gathering test results for the AIS subjected to CFD analyses and comparing pressure loss behavior to validate the evaluation. To perform CFD Analyses, a commercial CFD Solver called StarCCM+ (v.10.02) is used for analyses. Upon completion of the study, findings collected are as follows: - ASTM F778 test is reproduced via CFD, calculating air filter element's pressure loss with less than 7% difference in comparison with measurement. - CFD analysis of AIS is underpredicting the pressure loss by 11% when compared to tests. - CFD analysis of AIS underpredicts the pressure loss value around 15% for pleated air filter element when compared to measurement data. The results can be considered satisfactory, as the method to evaluate pressure loss is applicable for early stages of design where it is too expensive and time consuming to build and test a prototype for each design. Besides, the values of deviation for each pressure loss value are lesser than similar studies in literature, due to the increased detail level and quality.