The transient response of a turbocharger has an important influence on the performance of engine variable conditions. An accurate estimation of the transient response process time is necessary for variable condition control to improve the engine response characteristics. In this study, the effect of the key factors on the turbocharger response speed, such as the turbine inlet flow rate, temperature and rotor inertia is investigated. In addition, the relationships between the turbocharger response time with respect to the response process of the turbine inlet initial state flow rate, turbine inlet end state flow rate, turbine inlet temperature and rotor inertia show correlations. The predicted response time values obtained using the relationships in comparison to the simulated values within the calculation range of this study are within a 10% error.

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The characteristics of flow resistance in a pulsating turbulent flow through a 90° bend with a circular cross-section were investigated. Water was used as the working fluid to investigate a wide range of governing parameters experimentally. The Womersley number α varied from 10 to 50, the mean Reynolds number Re_ta from 7000 to 22000, the oscillatory Reynolds number Re_os from 6000 to 14000 (the flow rate ratio η was 0.3-0.8), and the curvature radius ratios R_c were 2, 4, and 6. The pressure drop between 2d (d: inside diameter) upstream and 4d downstream of the bend was measured and analyzed, assuming a quasi-steady flow. The effects of the non-dimensional flow parameters and curvature radius ratio on the flow resistance characteristics were investigated. The approximate expressions for the time-mean value, amplitude, phase difference from the flow rate variation, and power losses were consistent with the experimental results, and were thus practically useful.

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The bionic sawtooth structure has a good noise reduction effect on the middle and low frequency flow noise, but the current researches mostly focus on the airfoil noise reduction with limited sawtooth number, ignoring the search for the noise reduction law of the sawtooth structure parameters. In this paper, four structural parameters, including tooth number, height to width ratio, passivation ratio and angle of flow cut, are selected to study the optimization design of bionic sawtooth airfoil by numerical calculation method. A noise reduction method for bionic sawtooth airfoil optimization is proposed, and the sawtooth parameters with the optimal noise reduction effect are found. In this paper, the total sound pressure level is taken as the optimization objective, and the neural network algorithm fitting and adaptive simulated annealing algorithm are employed to optimize, and the rationality of the prediction results is evaluated by the method of manual supervision. The results show that the sawtooth number has the most obvious effect on the airfoil noise reduction effect, and the total sound pressure level after optimization is reduced by 0.55dB compared with that before optimization, and the noise reduction effect is mainly concentrated near the trailing edge of the airfoil.

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The paper presents a method for predicting the circumferential relative sliding between the seal ring and the outer rotor in the dual-rotor aero-engine intershaft seal under high temperature and high-speed conditions. A criterion is proposed for determining the circumferential sliding of the intershaft end-face gas film seal, taking into account the effects of centrifugal expansion and thermal expansion. The mechanical mechanism of the circumferential sliding between the seal ring and the outer rotor is investigated. The expansion of the seal ring and the outer rotor is simplified to a plane thermo-elastic mechanical problem, and the expansion and deformation of the two parts are calculated. The influence of material characteristics, temperature difference, and initial interference on the expansion deformation and connection relationship of the seal ring and outer rotor is analyzed. Moreover, the critical sliding speed region between the seal ring and the outer rotor is determined. The analysis method provides theoretical guidance for predicting the circumferential sliding of the seal ring in practical engineering applications.

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