International Journal of Turbo & Jet-Engines

Liu, Xiaodong

doi: 10.1515/tjj-2025-0054pmid: N/A

AbstractThis study investigates the aerodynamic performance of elliptical cross-section bypass double-throat nozzles (BDTNs) with varying short-to-long axis ratios (b/a = 1.0, 0.8, 0.6, 0.4), using an axisymmetric BDTN as a reference. Three-dimensional numerical simulations were conducted to analyze flow field structures and performance in both non-vectored and vectored states under fixed inlet conditions (300 K, throat area ratio 1:1.44). The research integrates shaped cross-section design into BDTNs, aiming to improve thrust efficiency and infrared stealth capability. Results show that in the non-vectored state, thrust coefficients peak at NPR = 6, with elliptical BDTNs outperforming axisymmetric ones as b/a decreases. In the vectored state, however, thrust coefficient and vector angle generally decline with smaller b/a. Notably, placing the bypass channel along the short axis markedly enhances vectoring performance: for b/a ≥ 0.6, vector angles exceed 8° and may reach above 20°, while thrust coefficients remain comparable to axisymmetric designs. Oblique secondary flow injection exhibits similar but weaker trends than axial injection. Overall, the b/a = 0.6 configuration offers the best balance between thrust enhancement and flow efficiency. These findings provide new insights into geometric optimization of BDTNs and offer practical guidance for the design of efficient, stealth-capable aero-vector nozzles.

Zheng, Qiangang; Liu, Wei; Sun, Fangze; Li, Liangliang; Xiang, Dewei; Zhang, Haibo

doi: 10.1515/tjj-2025-0090pmid: N/A

AbstractDirect thrust control can markedly enhance thrust regulation accuracy and unlock the full performance potential of aero-engines. To improve both real-time capability and precision, we propose a hybrid adaptive onboard predictive modeling framework, termed DNN-PSM-SVM. In this approach, a deep neural network captures strong nonlinearities to refine accuracy, while steady- and dynamic-deviation models based on PSM and SVM reduce computational complexity. A Kalman filter further enhances adaptability, avoiding heavy nonlinear calculations and significantly improving real-time performance. Leveraging this model within a predictive control scheme, unmeasurable parameters such as thrust and surge margin are estimated in real-time, enabling accurate thrust control even under component degradation. Simulation results show that the method outperforms conventional predictive control, achieving steady-state accuracy below 0.06 % and improving real-time performance by nearly an order of magnitude. Unlike sensor-based control, it maintains precise thrust regulation despite engine degradation.

Hu, Tingxun; Deng, Wangqun; Tang, Zhenhuan; Li, Jian; Zhang, Weifeng; Luo, Feng

doi: 10.1515/tjj-2025-0074pmid: N/A

AbstractResearch on floating ring seals of an Aero-engine, the equivalent analysis model of the dynamic characteristics was established which considering the dynamic response of the rotor, the sealing clearance, the gas buoyancy of the main sealing surface and the elasticity of the wave spring. Minimum radial distance between the graphite ring component and the rotating ring was evaluated. The results showed that the minimum radial distance of the high-pressure side of the two-stage floating ring seal was 0.027 mm, the minimum radial distance of the low-pressure side of the two-stage floating ring seal was 0.164 mm, and the minimum radial distance of the single-stage floating ring seal was 0.026 mm. The influence of friction coefficient of auxiliary sealing surface, processing error and assembly error of wave spring on the passive movement characteristics of floating ring seal was analyzed.The results showed that the risk of collision between the floating ring seal and the rotating ring was controllable when the auxiliary sealing surface of the floating ring seal has good machining accuracy and lubrication condition.

Zheng, Qiangang; Sun, Fangze

doi: 10.1515/tjj-2025-0086pmid: N/A

AbstractAdaptive variable cycle engines, capable of switching seamlessly between subsonic and supersonic modes, have become a central focus in propulsion research. Accurate and real-time onboard models are crucial for predicting performance in flight and supporting advanced functions such as control optimization, health monitoring, and fault-tolerant control. Yet, reconciling accuracy with computational efficiency remains challenging due to the engines’ inherent high dimensionality and strong nonlinearity. Here we present an NN-ΔNN-based modeling framework, where a neural network captures nonlinear dynamics, a ΔNN component represents high-dimensional features, and a Kalman filter enhances adaptability. Simulations show that this approach improves accuracy of key parameters by 0.17–1.6 times compared with NN-PSM across a wide flight envelope. It also achieves rapid thrust-tracking under single- and multi-component degradation within seconds, with low steady-state error, demonstrating strong adaptability and real-time capability.

Suresh, Sanoj P.; Choubey, Gautam; Kumar, Ajit; Rath, Jagat Jyoti

doi: 10.1515/tjj-2025-0113pmid: N/A

AbstractEnhancing airfoil performance through passive, energy free flow control is a key goal in modern aerodynamics. This study investigates a modified NACA 0012 airfoil incorporating a rectangular convergent duct at the leading edge. The internal passage accelerates lower surface airflow through the Venturi effect, creating a localized low-pressure region that enhances lift and stabilizes the boundary layer without external power input or mechanical actuation. Experiments in a subsonic open circuit wind tunnel at 10 m/s (Re ≈ 1.5 × 105) and steady state CFD simulations using the k–ω SST model were conducted under identical conditions. Both results confirm that the ducted configuration improves aerodynamic efficiency in the pre stall regime, achieving a 10 %–13 % increase in lift, 10%–15 % reduction in drag, and 30 %–35 % improvement in lift to drag ratio compared with the baseline NACA 0012. CFD and experimental findings agree within 10 %–15 % across all angles of attack. Flow field visualization shows a high momentum jet emerging from the duct outlet and a persistent low-pressure core beneath the lower surface, demonstrating Venturi driven acceleration that delays separation and sustains lift. The proposed passive internal flow control concept provides a simple, lightweight, and energy free means to enhance aerodynamic efficiency for low Reynolds number applications such as unmanned aerial vehicles and small wind energy systems.

Bose Gurusamy, Chandra; Sudalaimuthu, Ganesan

doi: 10.1515/tjj-2025-0103pmid: N/A

AbstractThe effect of Primary Nozzle Exit Diameter (PNED) on the decay characteristics and flow structure of circular underexpanded sonic coaxial jets has been studied numerically. Primary nozzles with exit diameters of 6 mm, 9 mm, and 12 mm were examined while maintaining a constant secondary nozzle width of 6 mm. The analysis was conducted at nozzle pressure ratios (NPRs) of 3, 5, and 7, with the 6 mm PNED configuration serving as the baseline for comparison. Axial Pitot pressure measurements and numerical Schlieren techniques were employed to evaluate pressure decay trends, shock-cell formation, and supersonic core behaviour. The study also focused on shear layer interactions between the primary and secondary jets and their subsequent interaction with the ambient environment. Results demonstrate that PNED has a significant influence on shock structure, jet coherence, and mixing efficiency. The 6 mm PNED exhibited both the shortest potential core and the most rapid Pitot pressure decay, highlighting its superior mixing performance across all NPRs. In contrast, jets with 9 mm and 12 mm PNEDs displayed extended supersonic cores, more persistent shock-cell structures, and reduced entrainment. Results show that the Potential Core Length (PCL) increases by about 28 % as PNED enlarges from 6 mm to 12 mm, indicating delayed mixing due to weaker shear-layer interaction. The results emphasize the importance of PNED in jet structure and mixing in coaxial configurations. The insights gained offer valuable guidance for optimizing nozzle design in propulsion, flow control, and other high-speed jet applications.

Jin, Hong-ze; Liu, Xue-guang

doi: 10.1515/tjj-2025-0096pmid: N/A

AbstractTo address the limited stable operating range of transonic centrifugal compressors, parametric analyses of negative pre-swirl recirculation casing treatment (RCT) were conducted using ANSYS CFX. The effects of the negative pre-swirl vane (NPS-vane) exit angle and slot width were examined, and a dual-RCT configuration was developed. Results indicate that adjusting the NPS-vane exit angle extends the operating mass flow rate range by up to 8.7 % and restores the peak pressure ratio to the smooth-wall compressor (SW) level, though with a slight efficiency penalty. Reducing slot width effectively alleviates passage blockage, improving the mass flow rate range by 4 % and increasing the peak pressure ratio by 1 % without efficiency loss. Compared with the single-RCT, the dual-RCT further suppresses downstream blockage and enhances both mass flow rate range and peak pressure ratio. These results demonstrate that RCT optimization and dual-RCT design provide a practical strategy to extend compressor stability with minimal impact on efficiency.

Li, Xiangyu; Meng, Qingkun; Zhou, Yi; Zhang, Zongwei

doi: 10.1515/tjj-2025-0049pmid: N/A

AbstractThis numerical study examines the flow and heat transfer in a six-stage high-pressure compressor disk cavity using Reynolds-averaged Navier–Stokes (RANS) and Shear Stress Transport (SST) k-ω models at rotational Reynolds numbers (Reφ) of 0.85 × 106 – 3.89 × 106. The results show decreasing swirl ratios influenced by cavity geometry and significant pressure losses occurring in cavities 1, 5, and 6, with low-pressure zones at fillets. Downstream disks exhibit stronge heat transfer dominated by vortices, while complex geometries reduce heat transfer due to low flow velocities. Turbulent mixing peaks between Reφ = 2.22 × 106 and 2.78 × 106, maximizing the heat transfer coefficients. At Reφ = 3.89 × 106, centrifugal effects induce flow separation and thus diminish heat transfer efficiency.