Band 42, Heft 4

A novel degradation estimation method is proposed to draw out the engine performance deterioration rules of multiple rotational-component parameters simultaneous variations from available sensors. The proposed methodology consists of the extended Kalman filtering (EKF) and an enhanced optimization strategy. Gas-path parameter analysis on the impact of components performance is implemented to determine the key degradation feature. The unmeasured feature is randomly generated to estimate performance drifts of rotational components by the EKF group and steady model. The achieved performance parameters stream to the engine dynamic model to yield measurements’ estimated series, which are utilized to construct the fitness function. Thus, the optimization gains the unmeasured feature and the deteriorations of engine performance. This paper reaches simultaneous performance drifts of all components under the limited sensors. Simulation results show the suggested approach provides the precise unmeasured feature, and quantify variations in the simultaneous drift of engine performance during its usage.

To reduce specific fuel consumption (SFC) of aero-engine, increase the combat radius of fighter jets, improve economic performance, and contribute to energy conservation and emission reduction, this paper proposes a hybrid optimization algorithm combining the chimp optimization algorithm (ChOA) and sequential quadratic programming (SQP). The algorithm ensures effective optimization while significantly reducing solving time. Focusing on a double bypass variable cycle engine, a sensitivity analysis is conducted to select optimal control variables. An intelligent optimization control system integrates ChOA-SQP with active disturbance rejection control (ADRC) for minimum SFC optimization. Results indicate that ChOA achieves a 7.28 % average SFC reduction, SQP achieves 6.71 %, and ChOA-SQP achieves 7.47 %, with ChOA-SQP reducing SFC an additional 0.57 % compared to SQP and 0.19 % compared to ChOA. Convergence time is only 24.25 % of ChOA and 109.75 % of SQP, with a convergence speed faster than ChOA and similar to SQP. The system transitions seamlessly to the minimum SFC point while ensuring safe engine operation, reducing SFC by 7.58 % at the subsonic cruise design point and 5.69 % at the supersonic cruise design point, with maximum thrust fluctuations of 0.87 % and 0.95 %, respectively.

The transient characteristic of the disturbance from impeller, which is largely influenced by the stagger angle of IGV (inlet guide vane), significantly determines the performance of the vaned-diffuser downstream. Thus, the understanding of these phenomena is critical to avoid the degradation of diffuser performance including the dreadful rotating stall. The paper adopts both the experimental and numerical methods to investigate the significant change of the diffuser transient characteristics under large pre-swirl effects. The whole process of diffuser rotating stall, which origins from the vortex at rear of diffuser, is comprehensively studied. It is noticed that the variation of pre-stall behavior within vaned-diffuser closely relates to the pre-swirl angle, which is mainly reflected by the characteristic change of separated vortex from diffuser blade surface. Under large negative pre-swirl condition, the flow non-uniformity between main and splitter blades of impeller significantly grows. It applies more influences on the transformation of vortex from rear to semi-vaneless region of diffuser and triggers the final stall precursor much earlier. Besides, a novel stall warning method based on the non-uniformity coefficient C has been developed and the prediction errors are controlled lower than 2 % in most cases.

Based on the sparse PC-Kriging method, a high-fidelity surrogate model was constructed to map the geometry of a stepped labyrinth seal to its leakage characteristics. Based on this surrogate model, Monte Carlo sampling was employed to analyze the impact of geometric errors on the uncertainty of the seal’s leakage characteristics and conduct sensitivity analysis. The results indicate that within a 99.7 % confidence interval, the maximum discharge coefficient can reach 0.584; compared to the baseline value of 0.52118, the worst-case scenario could lead to an approximate 12.1 % increase in the discharge coefficient, significantly increasing leakage. Sensitivity analysis reveals that the tip clearance of the fifth tooth exhibits the highest sensitivity to the discharge coefficient, approaching 80 % and dominating the response, while the remaining parameters show lower sensitivity, with 47 of them having sensitivities close to zero.

The uncertainty propagation and transient heat transfer from an extended surface are studied. The stochastic Biot number, the fin number and initial and convection boundary conditions define the uncertainty propagation for the temperature distribution in the extended surface. The amplitude of the propagated uncertainty was observed to have a transient evolution. The uncertainty may increase or decrease depending on the stochastic input parameters. Results are presented for the variation of temperature and heat flux due to uncertainties in the initial condition and conditions at the boundaries where heat is rejected.

Film cooling is critical in protecting gas turbine nozzle guide vanes from extreme thermal loads, enhancing their durability and efficiency. Understanding the interaction between aerodynamic performances and cooling effectiveness is essential for optimizing vane design. This study investigates the aero-thermal characteristics of a film-cooled gas turbine nozzle guide vane under subsonic conditions. ANSYS simulation software was used for the computational study, and the results were experimentally validated using a low-speed cascade wind tunnel setup with a coolant flow unit. The study explored how film cooling in different regions of the vane (Suction surface, pressure surface, leading edge) influences total pressure losses. Findings indicated that both effectiveness and loss coefficient increased with rising MFR. Specifically, an increase in MFR from 0.004 to 0.005 led to a 1.3 % improvement in cooling effectiveness and a 2.57 % rise in pressure loss coefficient. Similarly, when the MFR increased from 0.005 to 0.006, effectiveness improved by 10.86 %, and the total pressure loss coefficient increased by 3.25 %.

The uncertainty propagation and transient heat transfer from a flux-base extended surface are studied. The stochastic Biot number, the fin number and initial and convection boundary conditions define the uncertainty propagation for the temperature distribution in the extended surface. The amplitude of the propagated uncertainty was observed to have a transient evolution. The uncertainty may increase or decrease depending on the stochastic input parameters. Results are presented for the variation of temperature due to uncertainties in the initial condition and conditions at the boundaries where heat is rejected.

This investigation examines the performance of Hydrogen- and Kerosene-fuelled Scramjet combustors, emphasizing fuel injection strategies and combustion efficiency. Experimental findings and simulation results showed that hydrogen fuel achieved a combustion efficiency of 96 % when running in struts shortened by 45 % with proper modifications. Dual-strut fuel injection systems deliver better performance levels because their efficiency reaches 92 % compared to setups at 65 %. When injecting across the flow or creating cavities, the mixing becomes more efficient because this technique generates powerful vorticity along the streamwise direction and creates recirculation zones that strengthen flame stability and decrease flow pressure. Combustion in recirculation areas reached maximum temperatures exceeding 2950 K, which ensured stable burner operation. Hydrogen combustion during Mach 4.5 operations led to the minimum pressure loss rate and maximum thermal efficiency outcome. The study confirms that hydrogen functions as the best renewable fuel for Scramjet propulsion, which leads to the development of aircraft systems that are both reusable and environmentally beneficial.

This study employs the fluid-structure interaction (FSI) method to quantitatively evaluate the impact of different tip clearances on compressor blade performance, focusing on the influence of flow fields on structural behavior. The computational fluid dynamics (CFD) models utilized herein have been corroborated with experimental data. The vibration characteristics of blades were obtained based on the Campbell diagram, and fatigue life prediction was finally carried out. The results indicate that as the blade tip clearance increases from 0 times the design clearance to 2 times the design clearance, the tip vortex in blade tip flow field gradually strengthens, leading to a decrease in pressure ratio and efficiency, while the stable operating range of blade is shortened. Blade vibration modes are predominantly influenced by centrifugal loads, with tip clearance exerting a minor effect on these characteristics. The Campbell diagram indicates that the blade has low resonance margins at the design speed ranges of 54–59 % and 78–83 %, which are prone to resonance. After FSI calculations, it was found that the increase in blade tip clearance enhances the wing tip leakage vortex, reduces the aerodynamic load on blade, gradually reduces the maximum deformation of blade, and increases the fatigue life of blade.

Power generation using Wind energy does not contaminate and reduces the use of Fossil fuels contributing to sustainable development. The Savonius vertical axis wind turbines are omnidirectional and can operate in low-wind-speed regions, such as urban settings. Using 2D Computational Fluid Dynamics simulations at a low wind speed of 4.5 m/s, the effect of attachment on the convex side of standard Savonius blades with a fixed overlap ratio of 0.2 is examined in the current work. The findings indicate that, compared to all other rotor configurations with attachments, the rotor with an attachment measuring 187 mm in length and oriented 45° towards the incoming wind performs better. However, the configuration’s maximum power coefficient is lower than that of a traditional Savonius rotor. Thus, it is stated that attachments to the convex side negatively impact the rotor’s performance at a low wind speed of 4.5 m/s.

Ring dampers are widely installed in labyrinth seal structures of aero-engines to reduce vibration. In order to study the damping effect of ring dampers, an analysis method and design process of dry friction damping under radial component of vibration of labyrinth seal structure are established. Based on the friction energy dissipation, the equivalent damping ratio provided by the ring damper is calculated for the given vibration stress at the critical location, and the damping characteristic curve that is the equivalent damping ratio varying with the vibration stress is obtained. This method can avoid the calculation of nonlinear forced response and is suitable for the design stage. In the case study, the vibration reduction analysis is conducted on one ring damper for a certain labyrinth seal structure, and the influence of rotating speed, friction coefficient, radial thickness and density of ring on the damping characteristics is investigated.

A Stirling engine thermodynamic cycle was computationally simulated and probabilistically evaluated in view of the several uncertainties in the performance parameters. Cumulative distribution functions and sensitivity factors were computed for the overall thermal efficiency and net specific power output due to the thermodynamic random variables. These results can be used to quickly identify the most critical design variables in order to optimize the design, enhance performance, increase system availability and make it cost effective. The analysis leads to the selection of the appropriate measurements to be used in the Stirling engine health determination and to the identification of both the most critical measurements and parameters. Probabilistic analysis aims at unifying and improving the control and health monitoring of Stirling engine by increasing the quality and quantity of information available about the engine’s health and performance.

The need for Full engine Simulations is gaining traction in multidisciplinary fields due to the complexity and comprehensiveness of this high fidelity computational analysis whereas Gas turbines, as key power producing devices, have wide ranging applications in aerospace, power generation, and marine engineering. As industries strive for enhanced engine performance and sustainability, understanding the complex behavior of gas turbines through simulation is essential for optimizing design, efficiency and is crucial in determining the design and off design behaviour and characteristics across flight envelope. This paper presents a comprehensive approach to full engine simulation, incorporating both standalone and integrated analysis methods. By understanding both the approaches, the study offers a holistic understanding of the engine’s performance, facilitating the identification of potential design improvements and operational optimizations. This analysis focuses on primary flow incorporating turbulence within the fluid domain. The results shown using contour plots represent critical performance parameters, such as Mach number and static pressure variations across the engine’s operating range. These contours allow for easy identification of better operating points and highlight performance trends across different subsystems and overall engine configurations.

The research includes computational evaluation of the aerodynamic and combustion performance of a Double Cavity with Multiple Struts (DCMS) Scramjet propulsion installed inside the scramjet combustor. The Scramjet engine serves as the primary hypersonic propulsion system, optimizing high-speed travel by consuming atmospheric oxygen. Optimized injector geometries enable adequate fuel mixing and combustion processes during extremely condensed residence durations. Their contribution towards improving shock interactions and fuel-air mixing between each other makes both wedge and diamond strut injectors the preferred choice, according to established research. This research builds upon previous work to investigate how DCMS scramjet propulsion affects flow stability, mixing efficiency, and thermal characteristics during Mach 4.5 operations. Using ANSYS 2025R1, computational fluid dynamics (CFD) simulations were conducted to study the flow characteristics in the scramjet by analyzing various parameters, including static pressure, total pressure, static temperature, and Mach number. The DCMS Scramjet enhances turbulence production, resulting in steady shock structures and more efficient combustion. The computational model reached accurate validation through experimental shadowgraph image comparison with simulation predictions for density contours. Strut geometry evaluation, as presented in this research, yields crucial knowledge for hypersonic propulsion injector design.

Contra-rotating propfan (CRP) produce significant aerodynamic interference between the front and rear blades. The interaction effect of the front blade on the rear blade consists of two parts: the impact of the wake of the front blade and the tip vortex on the leading edge of the rear blade. The cutting effect of the rear blade on the wake section and tip vortex structure of the front blade. The combined action causes the pressure fluctuation of the rear blade, especially in the tip, the pressure fluctuation on the suction surface is more significant. The effect of the rear blade on the front blade is mainly reflected in that the potential flow effect of the rear blade leads to a relatively obvious pressure fluctuation on the pressure surface of the front blade. Under the potential flow effect, the pressure disturbance of the suction surface of the rear blade propagates upstream, which affects the pressure of the front blade pressure surface and makes its pressure distribution tends to that of the rear blade suction surface.

An investigation into high-speed rotating machinery dynamic research, the analysis of dynamic characteristics and instability mechanism in seal-rotor systems constitutes fundamental research. Current research on compliant foil gas seal (CFGS) primarily focuses on numerical simulations and experimental analyses, while limited exploration of the integrated dynamics of compliant foil gas seal-rotor system, especially in the coupled interactions among bearing, CFGS and rotor. To gain deeper understanding of the dynamic behavior of high-speed compliant foil gas seal-rotor system, this research employs the Newmark method to analyse and solve the dynamics of the seal-rotor system. The research explores the influence of rotational speed, geometric eccentricity, and mass imbalance on the rotor perturbation trajectories and amplitude responses. The results reveal that geometric eccentricity has a significantly stronger influence on the stability of seal-rotor system with mass imbalance and phase angle.

The S-shaped isolator was employed to approximate the reflection process of inlet oblique shock waves within the isolator. Numerical simulations were conducted for two S-shaped isolator-combustor configurations, and the results were compared with those of a straight isolator-combustor configuration. The influence of the S-shaped isolator on combustion characteristics and the backpressure propagation process within the isolator were analyzed, and the combustion flowfields and performance were compared. The results indicate that under cold flow conditions, the total pressure recovery coefficient of the S-shaped isolator is 0.05 lower than that of the straight isolator. Under combustion conditions, the parallel dual-cavity symmetric geometry generated an asymmetric flowfield structure. Compared to the straight isolator configuration, the combustion efficiency of the S-shaped isolator configuration decreased by 17 %, while the total pressure recovery coefficients of the two configurations were comparable. The outlet temperature distribution of the S-shaped isolator combustor was more non-uniform.

Conforming to the full three-dimensional (3D) trend of compressor aerodynamic design, a Customized Integrated Passage Design (CIPD) is proposed in this study. CIPD incorporates tip clearance into the full 3D design space and enhances the ability to control the geometric features of the 3D passage domain. Using this method, the classic transonic fan, Rotor 67, is redesigned. The deformed blade integrates geometric features of various directed control techniques. The results indicate a 1.1 % increase in peak efficiency of the blade, with a significantly performance improvement at the blade root and tip. The corner separation, shock wave/boundary layer interaction and tip leakage are all weakened. This study demonstrates that CIPD has the capability to achieve fine design of the entire passage and obtain considerable performance enhancements.

Unsteady flow loss mechanisms in compressors are critical for aerothermodynamic performance. This study proposes a method integrating entropy generation modeling and control volume analysis to evaluate unsteady losses. Using axially, spanwise, and azimuthally divided control volumes with nonlinear harmonic simulations, time-averaged and unsteady entropy generation distributions were analyzed in a transonic axial compressor. Results identified high entropy generation in rotor region, localized at the mid-to-rear chord, trailing edge, and blade tip. Key mechanisms include: 1. Shock wave/boundary layer interaction causing trailing edge boundary layer thickening and entropy generation rise. 2. Shock wave/leakage vortex interaction at the blade tip, involves mixing between the post-shock leakage flow and secondary leakage flow from adjacent passages, generating high entropy generation. 3. Rotor wake and stator leading edge interaction, inducing unsteady low-pressure zones and entropy generation fluctuations in the stator domain. The method effectively quantifies entropy generation and clarifies flow physics, aiding compressor design optimization.