![]() ![]() ![]() It is widely used in academia due to the considerable resources and time required to develop an efficient approach to better solve a problem. GA typically has a better chance of finding global optimum solutions despite the presence of multiple local minima. The advancements in computational power enabled GA to evolve as a popular optimization approach among researchers. Sibendu Som, in Artificial Intelligence and Data Driven Optimization of Internal Combustion Engines, 2022 4.1.2 Genetic algorithm For the case of radial inflow, the fluid in the interior core between the two Ekman-type layers rotates at an angular speed that is greater than that of the disc. If u φ,∞r Ωr the flow in the boundary layers for this region will be radially inward. If angular momentum is conserved, then u φ,∞r = constant, where u φ,∞ is the tangential velocity of the rotating core. If the swirl ratio is less than unity, then the fluid rotates slower than the disc at the outer radii and faster than the disc at the inner radii. The tangential component of velocity within the source region can be modeled as a free vortex (see Equation 3.35), with the tangential velocity increasing as the radius decreases. In total, 128 design candidates were generated and numerically evaluated at three engine operating conditions.įor the case of an effective swirl ratio of unity, c eff = 1, the flow structure in the cavity can be approximately modeled by a source region, Ekman-type layers, and a sink layer as illustrated in Figure 7.11, in a fashion similar to the case of radial outflow in Section 7.1.2.įor an effective swirl ratio of c eff r > r 1, where u φ Ωr, corresponding to the entrainment layer for the case of radial outflow (Section 7.1.2). Dependent variables were used by a local optimizer to finalize the geometry for each design candidate to meet the CR and other geometrical constraints. The Sobol sequence was used to fill the design space. Combining these with the three independent component-level variables, a total of eight design variables were selected as input variables in the optimization process. A total of five independent and six dependent parameters were derived from the geometry. The parameters shown in red are dependent variables and were typically used to conserve the bowl volume (and thus compression ratio) and preserve a reasonable distance between the surface and critical internal structures. The parameters shown in green are independent parameters that were considered to be the primary design variables in the optimization stage. Fig. 5.4 shows an example of the parameterized bowl profile in CAESES and the definition of each geometric parameter. The spray inclusion angle was defined relative to the piston axis and the lip location. The total nozzle area was conserved to keep the nozzle hydraulic flow rate constant. The design variables included several key piston bowl geometric parameters paired with three independent component-level variables: the number of injector nozzles, the spray inclusion angle, and the swirl ratio. The ratio of cylinder head bottom wall thickness to bore diameter which is used for the evaluation of the trade-off between mechanical load and thermal load. The number of cylinder head bolts and the head height, which are used for stiffness and sealing evaluation port flow coefficient, which is used for the evaluation of the trade-off between in-cylinder turbulence and volumetric efficiency The characteristic curve of swirl ratio vs. The ratio of port length to cylinder bore The ratio of port diameter to port length The basic competitive benchmarking parameters for cylinder head design include: The subjects of cylinder head design usually include the following: number of valves valve diameter and seat angle port flow discharge coefficient and swirl ratio intake and exhaust port orientation (to avoid intake port heating by exhaust gas) wall thickness exhaust port length and heat rejection losses cooling fire deck temperature control in the area between the valves in the cylinder head (to prevent thermo-mechanical fatigue) cylinder head gasket design, etc.
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