Browse Topic: Aircraft propulsion systems

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This SAE Aerospace Standard (AS) specifies the characteristics of screw threads - UNJ profile, inch, series, including a mandatory controlled radius as specified in Table 1 at the root of the external thread. The minor diameter of both external and internal threads provides a basic thread height of .5625H to accommodate the external thread maximum root radius. The following detailed design requirements are included: Screw threads - UNJ basic profile and design profiles. Standard series of diameter-pitch combinations for nominal thread diameters from 0.060 to 6.000 inches. Standard thread classes and form tolerances. Formulae for thread dimensions and tolerances. Method of designating UNJ threads. Tables for selected diameter-pitch combinations for close tolerance mechanical thread applications. Tables for screw thread - UNJ profile thread limit dimensions.
E-25 General Standards for Aerospace and Propulsion Systems
This SAE Aerospace Recommended Practice (ARP) addresses aeronautical Propulsion System Health Management. Aircraft propulsion systems are broader than gas turbine engines and include electric and hybrid propulsion systems. Furthermore, health management of auxiliary systems such as for thermal management of electric propulsion modules is also included in the scope. This document uses the term Engine Health Management (EHM) to include health management of propulsion systems and related equipment such as electric motors and heat exchangers for thermal management in an integrated power and propulsion system (IPPS). This keystone document gives a top-level view and addresses EHM description, benefits, and capabilities, and provides examples. This ARP purposely addresses a wide range of EHM architectures to demonstrate possible EHM design options. This ARP is not intended as a legal document and does not provide detailed implementation steps but does address potential benefits and general implementation issues. Other SAE documents (aerospace standards, aerospace recommended practices, and aerospace information reports) address specific component specifications, procedures, and “lessons learned.”
E-32 Aerospace Propulsion Systems Health Management
E-25 General Standards for Aerospace and Propulsion Systems
As the operating conditions of aircraft engines become more complex, the traditional maintenance strategies based on experience or fixed cycles are difficult to balance economic efficiency and reliability. This paper tentatively proposes a maintenance decision-making method driven by life prediction for aircraft engines. In the life prediction stage, considering the complex spatio-temporal coupling relationships contained in the degradation signals of multiple sensors, a spatio-temporal feature fusion transformation network is designed to jointly model the spatial dependence and temporal dynamics. At the same time, a probabilistic deep learning model is introduced to model the mean and uncertainty of the remaining life, providing risk warnings beyond point estimation. In the maintenance decision-making stage, the predicted distribution parameters are introduced into the Markov decision process state space. Based on the deep Q-network, a reward function is designed, and cost constraints are considered, thereby achieving a balance between safety and economy. Experimental results based on the C-MAPSS dataset show that this method achieves reasonable performance in common prediction indicators and demonstrates certain advantages over traditional maintenance strategies in the comparison experiments of maintenance decisions. The effectiveness of the method has been verified.
Yu, Sijia
The determination of flight thrust for aircraft engines is an important means of evaluating engine and aircraft performance. The characteristics of the tail nozzle of the tested engine are an important data support for calculating flight thrust. In order to accurately evaluate the flight thrust of a certain type of engine, an “engine nozzle characteristic determination test system” is developed to obtain the thrust characteristic curve and flow characteristic curve of the nozzle. A calibration device and calibration process were designed for the experimental system to achieve in-situ calibration of the system.
Ren, Boyang, Jia, Wenjie, Song, Jiangtao
As critical components of aircraft, hypersonic inlets utilize shock wave compression effects to pressurize incoming flow. The interaction between shock waves and the boundary layer tends to generate separation zones, and it adversely affects inlet performance. As a method to significantly enhance inlet performance, suction technology can substantially reduce the size of separation zones when they form in the inlet. However, when the inlet is started and operating normally, suction configurations may cause mainstream leakage and make it difficult to meet the requirements of inlets with wider speed ranges. This paper designs an adaptive scaliform suction structure that utilizes a lift-generating design to induce a slight upward deflection of high-speed near-wall flow. It can reduce high-speed mainstream leakage without compromising the effectiveness in low-speed separation zones. Numerical simulations are employed to evaluate its suction performance in both inlet separation zone flow fields and supersonic mainstream flow fields. The internal flow mechanisms of the scaliform suction structure are investigated, and differences in its behavior across various suction flow fields, as well as its interference with the mainstream, are discussed. The study reveals that when the height of the scaliform suction structure is approximately 1/8 of the incoming flow’s velocity boundary layer height, the suction flow coefficient in the separation zone is twice that in the hypersonic mainstream. Furthermore, the loss in Mach number and total pressure recovery coefficient of the near-wall supersonic mainstream is controlled within 5%. This structure exhibits an adaptive suction capability for separation zones, thereby extending the starting speed range of the inlet.
Zhao, Xuening, Zhao, Yilong
The pose-solving method for aero-engine component docking assembly often faces challenges such as slow convergence and susceptibility to local optima when dealing with complex optimization problems involving multiple features and constraints. This paper proposes an optimized assembly pose solution method for engine sections based on an improved multi-objective optimization algorithm. The method first preprocesses the high-density point clouds obtained from 3D scanning to extract geometry such as feature points, lines, and surfaces. It builds an assembly constraint model with geometric relations and process needs. It focuses on the pose solution phase: we transform the assembly problem into a nonlinear optimization problem to minimize parallelism error, gap error, and step error. In order to solve this multi-objective problem efficiently, we propose an iterative multi- objective optimization algorithm as the optimization engine and propose a dynamic weight allocation strategy. During iteration, the strategy adaptively adjusts the weight coefficients of three error terms in the overall fitness function due to the evolution of the population and convergence of each error term, guiding the search direction and balancing the algorithm's global exploration and local exploitation ability. Our results show that instead of adopting an optimization algorithm with fixed weights and a multi-Objective optimization system with fixed weight, the proposed pose solution method based on dynamic weight multi- objective optimization algorithm achieves a high accuracy and stability of the solution and can easily and accurately produce a good pose matrix which meets challenging assembly constraints, providing a practical theoretical framework and technical support for achieving high-quality automated engine assembly.
Huang, Mi, Wu, Guanghui, Su, Xun, Xu, Yongqian, Ding, Han, Liu, Xiaopeng
For the mixing of hydroxy-terminated polybutadiene (HTPB) with silicon dioxide particles, this study adopts the Computational Fluid Dynamics (CFD) method to conduct a visual analysis on the fluid flow field characteristics generated by the umbrella-frame impeller (UF impeller) and umbrella-frame combined impeller (UFC impeller). Comparative studies are carried out from the dimensions of particle concentration distribution, fluid flow trend, vorticity, and path line. The results show that compared with the UF impeller, the UFC impeller, equipped with an upper blade structure, enables its generated flow field to cover the entire stirred tank more effectively, significantly improving the solid-liquid mixing efficiency. In addition, the fluid-structure coupled numerical method is used to analyze the structural deformation characteristics and stress distribution law of the impellers. The research findings can provide a reference for the optimization of dispersion and mixing processes of solid particles in high-viscosity fluids.
Li, Ruizheng, Sun, Zhenxing, Zhang, Yan, Wu, Qiong
Aircraft engine parts are extremely precise, and for deep, small-hole machining of the stainless steel 05Cr17Ni4Cu4Nb valve seat, the quality and sealing of the parts machined with current machining parameters are poor. This greatly affects production efficiency and quality. This article takes the optimization of the three elements of cutting as the starting point, uses the orthogonal experimental method to study which force most affects machining quality in the three directions of boring force, and selects the appropriate three elements of cutting to reduce cutting force. And analyzed the simulated chip shapes before and after optimization, and finally verified the optimization effect through the instrument equipment. A micro three- axis accelerometer was used to conduct machining experiments on deep small holes with cutting parameters before and after optimization. After optimization of cutting parameters, the tool's maximum axial deformation showed a reduction of about 51.60%, a reduction of approximately 58.75% was achieved in the maximum radial deformation, the maximum tangential deformation exhibited a decline of about 45.17%, and the peak overall deformation was reduced by approximately 50.66%. Compared with the pre-optimized state, using optimized cutting parameters to machine deep small holes resulted in a 72.31% reduction in the tool's axial acceleration, the radial acceleration by 63.36%, and the tangential acceleration by 71.68%, the tangential force by 65.29%, the axial force by 27.93%, and the radial force by 31.16%. Effectively reducing tool chatter and lowering chatter amplitude led to the disappearance of surface vibration patterns on the machined parts.
Liu, Xinwei, Shi, Guangfeng, Zhou, Yuning, Gao, Jinglong
Inertial Friction Welding (IFW) equipment is essential for the welding process of aircraft engine shaft components. However, the absence of comprehensive fault-handling standards for domestically produced inertial friction welding equipment has hindered its further development. This study focuses on the connecting rod and motor of the 30T-IFW equipment, employing a model-based fault detection method. Through simulation, the deformation of the connecting rod and the frequency response of motor vibration acceleration under different working conditions are obtained. Additionally, a monitoring platform is proposed to collect real-time data on connecting rod deformation and motor vibration from actual welding equipment. By establishing a quantitative correlation model of connecting rod deformation-force and revealing the coupling mechanism between motor eccentricity faults and modal frequency vibrations, a hybrid diagnostic framework that combines simulation of primitive warning and measurement of calibration is proposed. At last, the simulation and experimental results verify the effectiveness of the fault diagnosis method proposed in this paper.
Yang, Haifeng, Yuan, Mingqiang, Sun, Tao, Liang, Wu, Gong, Maolin, An, Xingyi, Wang, Qisong, Liu, Dan
E-25 General Standards for Aerospace and Propulsion Systems
In this work, three-dimensional models of axial hole labyrinth-honeycomb seals (AHLHS) and circumferential hole labyrinth-honeycomb seals (CHLHS) were established by CFD to investigate the influence of different arrangement patterns on the static stability and leakage characteristics of two seals under choked and unchoked flow conditions and various eccentricities with different values. The results show that the two configurations have different advantageous ranges, and the hole arrangement pattern will not significantly change the pressure difference distribution between the two seals. Under most studied conditions, AHLHS maintains lower absolute values of stiffness coefficients, pressure difference groove, and negative cross-coupled stiffness coefficients, resulting in higher stability.
Li, Qing’an, Gao, Tongxin, Li, Zeze, Pang, Shuai, Lü, Yanjun, Zhang, Yongfang
Fleet heterogeneity, from manufacturing variations and diverse operating conditions, complicates reliability analysis by obscuring true failure patterns in aero-engines. This is a critical challenge in an industry as inaccurate Mean Time Between Failures (MTBF) estimates threaten safety and inflate operational costs, by forcing a choice between inefficiently conservative maintenance or the risk of in-service failures. Conventional analysis often fails by pooling all fleet data. To address this, our paper presents an analytical framework that improves predictive accuracy by filtering, rather than aggregating statistical noise. The methodology uses a Randomized Block Design (RBD) and ANOVA hypothesis test to screen a diverse dataset and isolate statistically homogeneous subgroups. This filtration identifies a core fleet with a consistent failure signature, providing a purified dataset for modeling. This refined data is then modeled using both Weibull and the Exponentiated Inverse Weibull distributions to ensure the results are robust and not model-dependent. Applying this framework to a 25-engine dataset that experienced 66 failures, we isolated a stable failure pattern, yielding a primary MTBF of 171.16 hours and a cross-validated MTBF of 176.35 hours. The close 3% convergence between these models validates our approach. By providing a dependable MTBF, this work establishes a stronger foundation for data-driven Reliability Centered Maintenance (RCM). It empowers maintenance planners to move toward evidence-based intervals, safely extending engine time-on-wing, optimizing spare parts inventory, and significantly reducing direct operational costs for airlines.
Jubaid, Mayin Uddin, Bebe, Gibson, Bigyen, Musa Pethuel, Anik, S M Kullul Mehedee, Yasmin, Ashrafi, Sahran, Mohamed Sideek Mohamed
This method is intended to evaluate the thermal and oxidative stability of synthetic, ester-based aviation lubricants under defined conditions of time and temperature. This method is applicable to lubricants meeting the compositional and performance requirements of AS5780.
E-34 Propulsion Lubricants Committee
In modern warfare, military control of the airspace determines aircraft survivability against the most widespread missile threats. The aero-engine exhaust system is an important source of infrared (IR) signatures from the rear aspect, particularly in the 2–3 μm and 3–5 μm IR bands. Two-dimensional (2D; non-axisymmetric) nozzle exits with high aspect ratio (AR > 5) are widely used in stealth aircraft engines due to their low IR signature, ease in thrust vectoring, and high maneuverability and agility. This analytical study compares the specific thrust (for choked and unchoked flow regimes) and the visible planar areas of a 2D nozzle exit with different ARs with those of a circular nozzle, as seen from the direct rear view. The nozzle’s isentropic efficiency (ηis,noz) is obtained in terms of the total pressure ratio, and the effect of AR on ηis,noz is examined for 1 ≤ AR ≤ 15. It is found that ηis,noz decreases with increasing AR, but this decrease is more rapid in unchoked flow than in choked flow. For the same value of nozzle exit cross-sectional area, the corresponding visible planar areas of aero-engine hot parts are compared for a 2D nozzle exit with different AR with that of the baseline case (circular nozzle), from bore-sight. This study shows that the optical blocking of aero-engine hot parts by a round-to-rectangular nozzle of AR ≤ 4 is almost the same as that of a circular nozzle, from bore-sight.
Baranwal, Nidhi
This SAE Aerospace Recommended Practice (ARP) recommends a methodology to be used for the design, analysis and test evaluation of modern helicopter gas turbine propulsion system stability and transient response characteristics. This methodology utilizes the computational power of modern digital computers to more thoroughly analyze, simulate and bench-test the helicopter engine/rotor system speed control loop over the flight envelope. This up-front work results in significantly less effort expended during flight test and delivers a more effective system into service. The methodology presented herein is recommended for modern digital electronic propulsion control systems and also for traditional analog and hydromechanical systems.
S-12 Powered Lift Propulsion Committee
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