Frequently, in the design of machines, some of parameters that directly affect the rotordynamics of the machines are not accurately known. In particular, bearing stiffness support is one such parameter. Taking a rig shafting as an example, this paper studies the lateral vibration of the rig shafting with multi-degree-of-freedom by using finite element method (FEM). The FEM model is created and the eigenvalues and eigenvectors are calculated and analyzed to find natural frequencies, critical speeds, mode shapes. Then critical speeds and mode shapes are analyzed by set bearing stiffness changes. The model permitted to identify the critical speeds and bearings that have an important influence on the vibration behavior.
In this study, an experimental investigation of a gasoline compression ignition (GCI) engine on combustion and emission fuelled gasoline-ethanol blend (E20). A diesel engine was modified and driven by an electrical motor to control the engine speed at 1500 rpm and IMEP at 4.5 bar. The aim of the given study was investigated to optimize the double-injection strategy including the injection timing of the second injection timing (SOI 2 ), and the dilution ratio as the exhaust gas recirculation (EGR). The SOI 2 was varied from −9 to −3 CA ATDC and dilution was simulated by using N 2 addition with a maximum level on 25%. It was shown that the combustion phase can be directly controlled by both SOI 2 and dilution. For the SOI 2 at −9 CAD ATDC, the combustion starts just after the beginning of the second injection and is delayed as a function of the dilution rate. Otherwise, the exhaust gas recirculation level was investigated to study the combustion and emissions characteristic with three cases of second injection timing while the first injection timing, fuel proportion and the intake pressure were kept constant: −35 CAD ATDC, 30%/70%, and 1 bar, respectively. The results have shown that NOx level decreased as a function of dilution for all SOI 2 with the smallest NOx level at-3CAD ATDC. However, CO and HC emission increased while increasing the dilution ratio. It is clear for SOI 2 is set at −3 CAD but between −6 and −9 CAD, the level of CO and HC emissions is really in the same order of magnitude.
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