Aero-engine Manufacturers Research Articles

Comparative study on machinability and surface integrity of γ-TiAl alloy in laser assisted milling

γ-TiAl alloy, as a typical difficult-to-cut material, is considered to have great potential in aero-engine manufacturing. However, it is difficult to achieve high-quality processing of γ-TiAl alloy using traditional cutting processes, due to the room temperature brittleness and high strength of theγ-TiAl alloy. This study proposes a fiber laser assisted machining (LAM) method to improve the cutting quality of γ-TiAl alloy, which attempts to address current challenges in applications of aero-engine manufacturing. The machinability and surface integrity of γ-TiAl specimens using LAM method and conventional milling are analyzed and discussed. Through cutting force testing, chip morphology research, surface hardness testing, and microstructure observation, it is found that the LAM method significantly improves the machinability and machined surface integrity of γ-TiAl specimens. Furthermore, the cooling strategies in LAM is discussed through comparative cutting experiments. During continuous LAM processing, it is found that the rapid heat accumulation effect induces tool adhesive wear, which leads to the decline of cutting quality and tool failure. The experimental results indicate that liquid cooling is an available strategy to reduce tool wear. However, it should be noted that periodic thermal shock by liquid cooling causes surface roughness to increase in continuous LAM processing. Through this work, it is proved that the LAM method can improve machinability and surface integrity of γ-TiAl specimens, which has great potential and worths further studies.

Role of Nb elements in SiCf/SiC/(CoFeNiCrMn)100-xNbx/GH536 brazed joints: Joint residual stress transfer and pinning of dislocations

Brazing is a critical method to address the challenge of connecting composite materials to metals. This study joined SiCf/SiC composites and GH536 superalloy using (CoFeNiCrMn)100-xNbx high-entropy alloy filler with varying Nb element contents successfully. The microstructural evolution and mechanical property changes of brazed joints were systematically investigated. Notably, when the Nb element content in the filler reached 12 %, a diffuse distribution of Nb(s, s) emerged in the joint, playing a vital role in effectively transferring residual stress on the SiCf/SiC side. This effect is attributed to the disparity in thermal expansion coefficients between the Nb(s, s) and face-centered cubic (FCC) phases. The resulting joint exhibited remarkable room temperature and high temperature shear strengths of 89.7 MPa and 49.7 MPa, respectively. Furthermore, the presence of Nb(s, s) in the brazing seam proved to impede the movement of dislocations during joint fracture. This work introduces a new technical paradigm for aero-engine manufacturing.

A novel assembly method of aero-engine rotors with minimized spindle inertia

Assembly is an essential part of aero-engine manufacturing, and the assembly quality will affect the engine’s stability and service life. Spindle inertia is an essential factor affecting aero-engine dynamic performance. Assembly can affect the spindle inertia of the aircraft engine, which in turn affects the dynamic performance of the engine. This paper proposes a transfer model of spindle inertia based on machining error transmission, studying the variation law of spindle inertia of multi-stage rotors under the influence of assembly, providing an optimized assembly method with minimized spindle inertia. The influence law of machining errors on spindle inertia is analyzed through the simulation and probability density method. The assembly results of the designed rotors verify the effectiveness of the inertia transfer and assembly model. The results show that the spindle inertia of multi-stage rotors is affected by machining errors, and the spindle inertia can be adjusted by changing the assembly methods. This paper provides a new idea for the transmission and adjustment of spindle inertia of assembly rotors.

A Numerical Study of Aero Engine Sub-idle Operation: From a Realistic Representation of Spray Injection to Detailed Chemistry LES-CMC

High altitude relight is a matter of increasing importance for aero engine manufacturers, in which combustion plays literally a vital role. In this paper we want to evaluate the predictive capability of a combined Smoothed Particle Hydrodynamics (SPH) and Large Eddy Simulation with Conditional Moment Closure (LES-CMC) approach for a spray combustion process at these extreme conditions. The focus is on the SPH modelling of the kerosene primary atomization, the extraction of realistic spray boundary conditions for LES-CMC and the effect of the spray on combustion. Interestingly, it will be demonstrated that the fragment size distributions resulting from the airblast atomization are characterized by bimodal behaviour during the relight process and that small and large fragments differ significantly in their dynamical behavior. This is shown to affect the combustion in the Central Recirculation Zone (CRZ). Very large fragments are even able to supersede the flame from the CRZ, such that endothermic pyrolysis becomes dominant, but simultaneously essential to sustain and stabilize the remaining flame with reactive pyrolysis species. The study proves the ability of our methodology for extreme operating conditions, in which experimental insights are hardly possible.

Probabilistic fatigue life prediction for CSS-42L bearing in jet strengthen modification grinding using an improved WTP network

Considering the high quality requirement of advanced aeroengine equipment, accurate prediction of probabilistic fatigue life (PFL) for CSS-42 L bearing in jet strengthen modification grinding, is an important issue for aeroengine manufacturing. Here an improved robust prediction algorithm of Wavelet Transform Package (WTP) Network is designed, therefore the decisive influence of jet strengthen modification grinding on the probabilistic fatigue life of aeroengine bearing, could be predicted and analyzed. A complete set of comparative experiments demonstrate that, when Pw is 23.5 MPa, Mc is 225 g, Mb is 342 g, Ma is 304 g, Fa is 0.26 kg/min, and Ts is 40.7 mm/min, and Bf is 69.442%, Cs is 70.336%, Nb is 69.002%, Sb is 54.334%, Os is 67.334%, Fp is 71.254%, At is 33.557%, W is 56.375%, Tr is 62.445%, an optimal data set of FLC is 60.5 × 105, PFLS is 0.337, FLGV is 83.74 × 102, CMFD is 8.42, FDP is 79.43, and NPFD is 4.445 (error tolerance = ±5%), could be obtained. This research is novel and merited in implementing novel PFL prediction for CSS-42 L bearing, proposing PFL indexes to evaluate the fatigue performance of bearing material in jet strengthen modification grinding, and designing an improved WTP network to achieve accurate PFL prediction as well. Eventually it could be summarized that this research realizes extraordinary predictive capability and facilitates the productive PFL management for aeroengine equipment.

PythonDAQ – A Python based measurement data acquisition and processing software

This paper introduces PythonDAQ, an open-source Python package for measurement data acquisition, visualization, storage, and post-processing. The code is capable of acquiring measurement data from any sensor with digital data output, performs online calculations, and stores the measured and computed data. A client for live data visualization and tools for postprocessing are also contained in the software package. First, the code is introduced explaining the software architecture and the currently implemented features. Then, the usability is demonstrated by an application at the low-speed compressor test rig FRANCC. As last step, comparisons between PythonDAQ and commercial DAQ solutions, as well as the data acquisition software of a major aero-engine manufacturer are made.

Influence of machining gap on both sides of blade in vibration-assisted pulsed electrochemical machining

The blades are important parts of any aeroengine, so the processing and manufacturing technology associated with blades has always been a high priority in aeroengine manufacturing. The electrochemical machining (ECM) of blades has become increasingly popular because there is no need to consider the strength, toughness, and hardness of the processing materials. Traditional ECM suffers from low dimensional accuracy and poor surface roughness. Thus, a low-frequency vibration of cathode tool is introduced to enhance bubble removal and electrolyte renewal. Due to the deformation of blade in ECM, the machining accuracy will be greatly reduced. This paper investigates the influence of gap difference which has been caused by electrolyte pressure and tool vibration on the deformation of the blade. The research results show that the deformation of blade increases with the increase of gap difference between cathode and blade. To restrain gap difference, a two-step processing test is conducted when blades were machined. It not only improves the processing efficiency, but also ensures the machining accuracy. The experimental results show that the total profile error of the blades is about 0.05 mm and the surface roughness is less than 0.13 µm when the final gap difference is 0 mm, signifying high profile accuracy and surface quality.

Sustainability Fingerprint - guiding companies in anticipating the sustainability direction in early design

During the early phases of design of new products, information necessary to guide and assess sustainability is typically incomplete. Manufacturers risk discovering the unfavorable sustainability impact too late to redirect the development. The purpose of this study is to search and review methods to anticipate the sustainability performance of new products in the early stages of the innovation process, and, together with a case company in the aeroengine manufacturing business, to develop and propose a systematic approach to anticipate sustainability performance. Following a literature review of 51 methods and research-based proposals, only five covered the social-, ecological-, and economic sustainability dimensions in the early phases of product development. Through an action research-based approach, a qualitative sustainability measurement tool, the Sustainability Fingerprint tool, was developed. This tool allows the development team in a company to systematically derive a sustainability performance from a set of criteria unique to the targeted product and/or product portfolio that is to be designed, from a set of scientifically well-established sustainability principles. The tool was applied in six different industry cases at the company, by the design teams and independent of any influence of the researchers. Semi-structured interviews were conducted to learn about the usefulness, usability, and applicability of the tool. It was concluded that the Sustainability Fingerprint tool has no equivalent in the literature and was considered useful for the case company during early phase design for two main reasons. Firstly, the tool is tailor-made with defined company-specific sustainability criteria that represent the most important sustainability aspects to assess. Secondly, the support tool can be used also in later phases, thereby supporting a continued innovation process. It allows designers to anticipate a sustainability performance of the solution in: the development of sustainable innovations; comparison and down-selection of alternative solutions; sustainability assessments of the product portfolio to identify improvement measures; and sustainability assessment of current products to identify sustainability hotspots. Further research will include companies from other industrial sectors and will focus on adding digital support, improved practical instructions, and, integration to existing processes and established support tools in companies today.

Sustainable product development in aeroengine manufacturing: challenges, opportunities and experiences from GKN Aerospace Engine System

Abstract A radical shift in technology is necessary to enable future air transport solutions. Sustainability targets for aeroengine manufacturing mean more than reducing CO2 and NOX. The future will open up possibilities and bring new challenges when introducing hybrid- and electrical propulsion technologies using new materials, technology solutions and new business models. This article reports on findings from a longitudinal study and many years of collaboration between researchers and industry experts, where a first-tier aeroengine manufacturer transforms their product development capabilities to enable sustainable product development. The article highlights some activities undertaken and identifies critical challenges and opportunities remaining for a manufacturer of next-generation aeroengine solutions. It is argued that the challenge for aeroengine manufacturers to develop new-generation propulsive technologies will require a systemic change in the undertaking of design and development. The opportunities of sustainable technologies are evident yet require: (1) means to tighter integrate business and technology development, (2) the ability to quantify and assess sustainability impacts of different concept solutions, and (3) means to utilise natural resources, alloys and materials for a circular and life-cycle optimised solution.

Laser powder bed fusion technique of hydrogen–fueled gas turbine: Role of advanced materials and its challenges

Aviation accounts for 1.9% of greenhouse gas emissions, decarbonization is not straightforward as electrification is not feasible, and biofuels only partially address the issue. Therefore, aero-engine manufacturers are looking towards hydrogen as a clean fuel source as the emissions would majorly be water with no lasting greenhouse gasses. The major challenge with hydrogen-firing engines would be high firing temperatures, corrosive exhaust gasses and adverse reactions with structural components. The design flexibility of additive manufacturing (AM) and advanced materials development, such as high entropy alloys (HEAs) can be combined to produce gas turbines with higher turbine inlet temperatures and power output. This paper discusses the advantages and issues with hydrogen as fuel, the role of AM and advanced materials suitable for hydrogen-firing engines.

Microstructure and mechanical properties of SiCf/SiC composites/ GH536 superalloy joints brazed with CoFeNiCrCu high-entropy alloy filler

Brazing is a crucial technology to achieve the connect of the stator blades of aero-engine and the inner and outer rings of casing. In this work, SiC f /SiC and GH536 were brazed by using a high entropy alloy CoFeNiCrCu filler. The interfacial microstructure, brazing mechanism and mechanical properties of the joint were investigated by SEM, TEM and shear strength test. The interfacial reaction was dominated by reactive elements in the initial stage of brazing. The phase structure of the interlayer did not change due to the high entropy mixing effect of the filler. Thus, the typical microstructure of CMCs/Cr 23 C 6 /Ni 2 Si/FeSi/MoNiSi/Cr 4 Fe 4 NiC 4 /FCC/Ni(s,s)/GH536 could be identified at welded joint. Owing to high entropy effect of CoFeCrNiCu filler, random solid solution turned out in the seam, thus the mechanical properties of the joint were greatly enhanced. This work offers a new idea and technological paradigm to develop the aero-engine manufacturing industry for engineers and researchers. • SiC f /SiC composite and GH536 were brazed by CoFeNiCrCu filler successfully. • The maximum shear strength of brazed joint was up to 86 MPa. • A physical model was proposed to describe the microstructure evolution.

Research on five axis machining method and manufacturing technology of impeller

The aviation industry is a symbol of a country's comprehensive strength. Among the aviation parts, the impeller and blade are the core components of the engine. They are widely used in aerospace, ship navigation, mineral machinery, national defense and military industry. Their material is hard, the profile is complex and distorted, the blade is thin, the spacing is small, and the surface accuracy is streamlined [1], Aeroengine manufacturing technology has become the standard of a country's scientific and technological strength. Therefore, the research on the manufacturing and processing technology of impellers and blades has important research value for all types of aircraft, military equipment, automobiles, ships and civil equipment, and has important strategic significance for economy and national defense. Based on the analysis of the functions and characteristics of five axis machining and the application of the operating principle and structural characteristics of jet engine impeller, the machining process and program of five axis machining of impeller are compiled in this paper.

Research on Development Status and Trend of Aeroengine in China

The key manufacturing technology of aero-engine is an important index for the future development of aero-engine industry in China. The traditional manufacturing process and production mode can't meet the requirements of high precision, high quality, high efficiency and high reliability of aero-engine. The following three-axis, four-axis, five-axis digital processing is an important foundation for the future development of China aero-engine manufacturing industry. Aero-engine is the most important component of aircraft power supply system, and has experienced the development process of DC engine, brush synchronous engine and three-stage brushless synchronous engine. On the basis of analyzing the performance and characteristics of various engines, this paper analyzes the development direction of new civil and military aero-engines.

How Do Interfacial Shear and Gravity Affect the Oil Film Characteristics Near an Aero-Engine Bearing?

Abstract Recent demand for reducing carbon emission and for increasing engine efficiency has led aero-engine manufacturers to strive for a better oil flow system. Aero-engine bearing chambers that house the shaft-support bearings are among the most challenging parts of the engine systems and it is imperative to have a proper understanding of the oil flow characteristics inside a bearing chamber to increase the engine efficiency. The present work is focused on experimentally investigating the oil film characteristics near a ball bearing static slot in the co- and counter- current regions at various rotational Reynolds number (Reω), loads and liquid flow rates. The experimental investigation has been carried out over a wide range of engine relevant Reω up to 1.7×106 using high-speed imaging and a long distance microscope. The results show that formation of the oil film on the static elements of the bearing is governed by both gravity and interfacial forces at low Reω but only governed by interfacial forces at high Reω. The nondimensional film thickness ranged from 0.71 to 0.18 and decreases with increasing Reω. A regime map was obtained based on the waviness of the film interface showing three different types of wave. At all conditions investigated all waves were capillary waves. Reω, oil flowrate and gravity were found to have a significant effect on the film thickness (δ) with transitions matching the wave regime map.

Variation Analysis Considering the Partial Parallel Connection in Aero-Engine Rotor Assembly

The rotation precision of rotors determines the efficiency and quality of the overall aero-engine, as well as its long-term and reliable operation ability. As the terminal link of aero-engine manufacturing, the assembly is the last guarantee of precision control. Rotor assembly relates to the accurate expression of the connection form and design optimization of the assembly scheme. The existing variation model cannot adequately handle the partial parallel chain problem, ignoring the bayonet circular connector between the rotor parts, and it is still deficient in multistage gyration error control. In this paper, the partial parallel connection and multistage revolving characteristics of rotors were discussed, and a novel modeling and optimizing method for a partial parallel dimension chain was proposed. On the one hand, the variation expression of the connection features for the revolving components considering the partial parallel structure was researched. Contact point-based torsors were represented, and a system for locating points was regarded as an assembly to describe the partial parallel chain. On the other hand, the variation propagation modeling and control for the stacking of the multistage revolving components was researched. A revolution joint was introduced in the unified Jacobian–Torsor model, and a novel assembly technique for concentricity control was proposed. Therefore, a unified variation analysis and control method for rotor assembly has been developed. Experimental results show that through this method, the final concentricity variation is 0.0539 mm, far less than the 0.1595 mm of the traditional model, and is closer to the true value range of 0.030–0.040 mm. Moreover, the optimum installed angles can be calculated as 3.153 rad, 6.025 rad, and 2.590 rad, to obtain the highest concentricity of 0.040 mm, which has strong practical guiding significance.

Effect of surface integrity generated by machining on isothermal low cycle fatigue performance of Inconel 718

Critical aero-engine components such as turbine discs must withstand severe cyclic stresses, which can eventually lead to low cycle fatigue (LCF) failures. These components are made of difficult-to-cut alloys and machining conditions that are employed in the last stage of the manufacturing chain must be correctly defined to avoid the generation of an adverse surface condition (tensile residual stresses, excessive surface roughness or microstructural defects) that will accelerate fatigue failure. The analysis presented in this paper is aimed at understanding the isothermal LCF behaviour of turned Inconel 718 workpieces and finding quantitative correlations with the surface integrity. For this purpose, two Inconel 718 forged discs were face turned at cutting conditions employed in the aero-engine manufacturing industry using two different tools (1.2 mm and 4 mm nose radius respectively). The surface integrity produced by the face turning process was characterised in both discs: surface topography, residual stresses and surface layer anomalies. Specimens extracted from both discs were tested in load control at 450 °C to obtain LCF fatigue behaviour. Importantly, interrupted isothermal LCF fatigue tests were conducted and residual stresses were measured by the X-ray diffraction technique at the surface of the tested specimens to study the role of residual stresses in the LCF fatigue behaviour. For the tested conditions, the specimens machined with 4 mm nose radius showed 1.3–1.4 times longer fatigue lives than the specimens turned with 1.2 mm nose radius. These results are in agreement with the better surface integrity generated with the 4 mm nose radius, mainly because it induced lower tensile residual stresses. A novel local approach was implemented to understand the influence of surface integrity (surface roughness, surface residual stresses and altered stress-strain properties of the surface layer) on the isothermal LCF fatigue behaviour of both machined discs. Interestingly, a satisfactory correlation was found between the maximum applied stress in the surface layer and the isothermal LCF fatigue life employing the local approach.

Discussion on the Development and Prospect of Aeroengine Manufacturing

Discussion on the Development and Prospect of Aeroengine Manufacturing

Holistic sustainability assessment of novel oscillating-heat-pipe grinding-wheel in Earth-friendly abrasive machining

The aero-engine manufacturing industry is booming in China, while sustainability is neglected. For example, the grinding superalloy part uses a high-volume low-velocity flood delivery strategy for grinding cooling, which is harmful to health and the environment, consumes more resources and energy, emits more CO2 and increases production costs. To achieve sustainability in the aero-engine manufacturing industry, it is worth considering eliminating coolant from the grinding to reduce the environmental impact and production cost. In this study, a novel oscillating heat pipe grinding wheel (OHP grinding wheel) is introduced to enhance the heat transfer in the eco-benign grinding process. The core concept is to design, fabricate particular oscillating heat pipes and position them in the grinding wheel so that the inside oscillating heat pipes transfer out the heat directly through the grinding wheel to avoid heat gathering, lower the grinding temperature, and suppress the thermal damages. Moreover, the use of harmful coolant can be diminished or even avoided, and an eco-benign grinding technology can therefore be achieved. Holistic sustainability analysis is then conducted in this paper. Compared with grinding by Non-OHP grinding wheel, the water-based coolant is avoided, the energy consumption is reduced by 26%–42%, and the carbon emission is reduced by 45%–56%. The OHP grinding wheel shows a great advantage in eco-benign grinding.

Corrosion behaviour of nickel based abradable coating used in aero engines

The corrosion potential of abradable nickel based coating used for aero engine components (for sealing and clearance control in compressor of aero engines) was explored and the effect of acid rain was observed for varied length of time. Coating plays an important role in aero engine manufacturing industry as it provides surface protection against corrosion, erosion, friction and wear when subjected to harsh conditions viz., high temperature and corrosive environment during service period. The coating deposition was done by using thermal plasma spray method. Porosity was observed to be high at critical plasma spray parameter (CPSP). Phase transformation and interlayer oxide formation were also observed during plasma spray coating. A comparative study was established between acid rain treated and untreated samples by evaluating the corrosion resistance potential, microstructural characterization, composition and phase analysis of coatings of treated samples using Scanning electron microscopy, X-ray diffraction and EDS. The weight gain of coating was also evident after acid rain treatment of up to ten weeks of immersion.

Ultrastrong and ductile transient liquid phase (TLP) bonding joints reinforced by ordered multi-precipitates

Transient liquid phase (TLP) bonding of is one of the most important welding technique to be applied to manufacture core components of aero-engine turbines . Homogeneous microstructure in a TLP joint with no defects and brittle products has always been the goal we pursued. But actually, this is far from the requirements for a superior-performance, long-life and excellent-reliability turbine as the joints need to be serviced with comprehensive properties such as high strength and toughness, outstanding creep resistance and so on. In this work, an ultrastrong and ductile TLP joint of high entropy alloy (HEA) of FeCoNiTiAl and FGH98 superalloy has been achieved by controlling ordered multi-precipitates, L1 2 -Ni 3 Al, TiB 2 and M 3 B 2 borides, produced in the welded zone. Formation and growth kinetics of the precipitates were characterized by atom probe tomography (APT), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). Furthermore, a microstructure-based finite element model (FEM) combined with the TEM analysis were applied to study plastic deformation mechanisms of TLP joint with maximum shear stress of 1156 MPa and excellent ductility (an abundance of dimples in fracture surface). As a result, the superb joint performance was due to competition and coordination of multi-precipitates. This work offers a new technological paradigm to develop the aero-engine manufacturing industry for engineers and designers.