Peng Liu

A novel tubeless vortex reducer with integrated deswirl nozzles is proposed to suppress the non-monotonic flow characteristics of the traditional vortex reducer. The flow characteristics of this vortex reducer are investigated through numerical simulations and experiments. The integrated nozzles consist of two types of nozzles: the main nozzles and the auxiliary nozzles, which have distinct geometric shapes. Utilizing the distinctions in flow characteristics between two varieties of nozzles, differing flow distribution ratios are achieved at varying flow rates. At low flow rates, the auxiliary nozzles are effectively “closed” due to the fact that virtually no fluid is passing through them. This enhances the deswirl effect, thereby reducing the pressure drop at the lower knee of the vortex reducer's flow characteristic curve. The deswirl effect at the upper knee is reduced as a result of the auxiliary nozzles being “opened” at high flow rates. Consequently, the pressure drop range of the unstable multi-solution region is significantly reduced by 57.3% from the numerical simulation and 32.5% from the experiment. Conversely, the pressure drop and flow rate at the design point can be independently altered by adjusting the flow area of the main nozzles and the auxiliary nozzles, respectively. This prevents the issue of traditional vortex reducers increasing the bleed air flow rate at the expense of increased pressure drop. The structural robustness advantage of this tubeless vortex reducer is preserved by this innovative design, which does not incorporate any additional structures or mechanisms.

The complex three-dimensional non-axisymmetric flow within the compressor cavity requires full 360 circumferential domain to capture accurately, whereas simplified two dimension (2D) axisymmetric calculations yield substantial errors. Accurate assessment of tip clearance variations during engine transient processes necessitates transient conjugate heat transfer (CHT) calculations. However, transient CHT calculations impose substantial computational time costs. Even with time-acceleration algorithms, the large spatial grid size required for full 360° circumferential coverage of the compressor disk cavity remains a limiting factor. This paper proposes a novel dimensionality reduction computational method enabling 2D calculations to achieve equivalent results to three dimension (3D) full-circumference computations, significantly reducing computational demands. By applying a spanwise averaging process to the Navier–Stokes (N–S) equations, spanwise-averaged N–S equations are obtained. Missing spatial field information is supplemented in the form of spanwise-stress residual (SSR) tensor. Various forms of SSR suitable for different conditions are explored. This method is validated in both simple square cavity natural convection cases and compressor disk cavity cases. The difference between the 2D case with added SSR and the 3D case is small. For transient process simulations, interpolation methods can be employed to obtain the SSR at each time step. The SSR is iteratively updated until convergence is achieved. Comparison of the transient iterative calculation results with existing experimental data demonstrates the reliability of this method for transient CHT calculations. This method achieves acceleration factors approaching 100 times for transient CHT calculations, providing a pathway for accurate and rapid simulation in engineering applications.

A vortex reducer is employed to reduce the pressure drop during the radially inward air bleeding process in aero-engines. The vortex reducer with deswirl nozzles (DVR) has the advantage of structural robustness; however, its complex, non-monotonic flow rate–pressure drop characteristic limits its widespread application. In an effort to resolve this issue, the current study employs both experimental and numerical methodologies to investigate the effects of nozzle geometric parameters on the flow characteristics of the DVRs, which are currently deficient. The findings indicate that, irrespective of variations in nozzle radial position or flow area, an elevation in the design point flow rate invariably results in an augmented pressure drop, and this coupling effect cannot be circumvented by modifying the geometric parameters. When the nozzle radial position is lowered to below b₁ = 130 mm or the flow area is reduced to below d₂ = 1.19 mm, the flow characteristic of the DVRs becomes monotonic; nevertheless, due to the severely limited flow capacity, such a monotonic characteristic lacks practical engineering significance. Therefore, both the nozzle radial position and the flow area should be regarded as separate independent variables in optimization calculations during the design process, necessitating the development of a rapid and accurate low-dimensional model.

This study investigates the evolution of axial loads in the secondary air system following shaft failure in aeroengines. It addresses a significant gap in the existing literature regarding the effects of inertial forces within the cavity, as well as the unclear mechanisms by which the geometric parameters of the flow path influence these forces. A combined approach of three-dimensional simulation and experimental validation is utilized to propose a method for analyzing the evolution of axial loads during the fast transient response process, based on changes in the Cavity Inertial Force Dominant Zone (CIDZ). The research examines both single cavities and cavity–tube combination flow paths to explore the impact of inertial forces on the axial load response process and, subsequently, the influence of flow path geometric parameters on this response. The results demonstrate that inertial forces within the cavity and the geometric parameters of the flow path significantly affect the axial load response process by influencing the intensity, phase, and minor oscillation amplitude of the axial load response at various end faces within the cavity. The variation in a single geometric parameter in this study resulted in a maximum impact exceeding 500% on the differences in axial loads at different end faces within the cavity. The study offers theoretical support for the load response analysis of the secondary air system in the context of shaft failure, serving as a foundation for safety design related to this failure mode.

The aero-engine pre-swirl system plays a critical role in cooling turbine rotor blades to maintain their temperature within operational limits. With advancements in propulsion efficiency and the reliable implementation of the secondary air system functions, such as blade cooling, rim sealing, and axial force control, modulated pre-swirl systems present significant potential applications for next-generation aero-engines. Adjustments to the pre-swirl system inevitably influence power consumption and cooling air temperature. This study develops an evaluation model for power consumption and temperature drop in the radial modulated pre-swirl system, incorporating all sources of power consumption and accounting for the coupled interactions between upstream and downstream flow and energy. The accuracy of the proposed model is validated through numerical simulations, and deviation sensitivity analysis is conducted to identify and assess potential sources of error. Furthermore, the proposed evaluation model is employed to analyze the effects of pre-swirl angle, rotational speed, and system pressure ratio on the flow characteristics and temperature drop of the radial modulated pre-swirl system. The results indicate that the model's predictions for system power consumption and swirl ratio distribution align closely with numerical simulations and published literatures, with maximum deviations of 7.2% and 18.9%, respectively, and a maximum temperature drop error of 2.03 K. Deviation sensitivity analysis reveals that the pre-swirl temperature drop and the outlet swirl ratio exhibit low sensitivity to errors in torque calculations, with maximum observed deviations of 1.9% and 5.3%, respectively.