Aero-engine Assembly Research Articles

Study on Probability Distributions of Processing and Assembling Promoters of Aero-Engine Critical Part

According to the characteristics of aero-engine and the study purpose of this paper, aero-engine information data were collected and screened from " Aero-engine Assembly Resume ", included: certain engine components data, assembly detection data and engine trial run data. By using the collected and screened data, correlation analysis were carried among testing parameters and among vibration parameters, correlation analysis were also carried between testing parameters or vibration parameters and components geometry parameters, assembly parameters or parameters combination which impact engine performance. From the result of correlation analysis, the key parameters strongly affecting engine performance can be found out, and then according to the value of the correlation coefficient put these parameters in queue. The optimal distribution of these parameters in queue can be determined by data analysis software, and the estimation eigenvalue of these parameter can be obtained. Purpose and significance of this paper is to improve the reliability of the components producing and assembly processing, what is more, it provides theoretical basis for the design and improvement of aero-engine.

Quantitative and Meticulous Methods to Aero-Engine Assembly Process

Manual operation and paper document based management are the bottleneck to the quality and efficiency of aero-engine assembly process. A set of optimization methods is presented about the aero-engine assembly process. From the technical point, the model of LoA (Level of Automation) was expanded with the addition of the role dimension and task dimension to construct a quantified method of level of assembly information automation, which was utilized to guide the digitalization of assembly process. From the management point, the meticulous management was utilized to improve the microcosmic operation and macro flow control of assembly. A refine and quantified assembly digital system for aero-engine has been developed to verify the effectiveness of the optimization methods.

Advanced Engineering Methods for Assessing Welding Distortion in Aero-Engine Assemblies

Welding remains an attractive fabrication method for aero-engine assemblies, offering high production rates and reduced total cost, particularly for large complex assemblies. However, distortion generated during the welding process continues to provide a major challenge in terms of the control of geometric tolerances and residual stress. The welding distortion is influenced by the sequence and position of joints, the clamping configuration and the design of the assembly. For large complex assemblies the range of these options may be large. Hence the use of numerical simulation at an early stage of the product development process is valuable to enable a wide range of these factors to be explored with the aim of minimising welding distortions before production commences, and thereby reducing the product development time. In this paper, a new technique for simulation of welding distortions based on a shrinkage analysis is evaluated for an aero-engine assembly. The shrinkage simulations were built and solved using the ESI Group software Weld Planner. The rapid simulation speed enabled a wide range of welding plans to be explored, leading to recommendations for the fabrication process. The sensitivity of the model to mesh size and material properties is reported. The results of the shrinkage analysis were found to be similar to those of a transient analysis generated using ESI Group software SysWeld. The solution times were found to be significantly lower for the shrinkage analysis than the transient analysis. Hence it has been demonstrated that shrinkage analysis is a valuable tool for exploring the fabrication process of a welded assembly at an early stage of the product development process.

Petri Nets-Based Implement Process Model for Engineering Change on Aero-Engine Assembly Field

The traditional artificial mode of engineering change implementing in aero-engine assembly field often results in difficulties of the process control. To solve this problem, this paper firstly puts forward an aero-engine assembly field configuration relationship model (AACRM) based on the configuration data structure and correlation coordination relationship between configuration items, then analyzes the structure of engineering change document and its implementation process in assembly field. Lastly, assembly field engineering change implementing process model (AEIPM) is established based on Petri nets modeling method, which constructs the implementing and confirming process of engineering change from a product level to a step level and then from a step level to a product level.

A Computational Parametric Analysis of the Vibration of a Three-Spool Aero-Engine Under Multifrequency Unbalance Excitation

The integration of squeeze-film dampers (SFDs) in aero-engine assemblies is a highly cost-effective means of introducing damping in an otherwise lightly damped structure. However, their deployment requires careful unbalance response calculations that take due account of the SFDs’ nonlinearity, particularly when they are unsupported by a centralizing spring. Until recently, such calculations were prohibitive due to the large number of assembly modes that typically need to be considered. This problem has been overcome by the authors through the novel impulsive receptance method (IRM) and the receptance harmonic balance method (RHBM), which efficiently solve the nonlinear problem in the time and frequency domains, respectively. These methods have been illustrated on a realistic twin-spool engine and have been shown to be effective for both single frequency unbalance excitation (unbalance on a single rotor) and multifrequency unbalance (MFU) excitation (unbalance on both rotors). In the present paper, the methods are applied to a realistic three-spool engine and the aims are twofold: (i) to present some preliminary results of a parametric study into a three-spool aero-engine assembly and (ii) to propose a technique that makes use of both IRM and RHBM in producing the speed responses under MFU excitation (from all three rotors) with a realistic speed relation between the rotors. The latter technique is necessary since the speed ratio will vary along a realistic speed characteristic and the authors have previously solved the twin-spool MFU problem under a constant speed ratio condition. The approach used here is to approximate the speed characteristic by one in which the speed ratios are ratios of low integers, enabling the use of RHBM to finish off (to steady-state) time-transient solutions obtained through IRM. The parameter study shows that the application of simple bump-spring supports to selected, otherwise unsupported, SFDs along with slight sealing should have a beneficial effect on the dynamic response of aero-engines with heavy rotors.

Novel Optimization Technique for Variation Propagation Control in An Aero-Engine Assembly

This paper presents a novel optimization technique in straight-build assembly to control variation propagation. The optimization technique is developed by minimizing the eccentricity stage by stage in the assembly. The straight-build assembly model is derived from connective assembly models, easily expressing the part-to-part relationships. Any measurement error or process error in the assembly can be easily incorporated in the model. This approach can be also used to predict the final assembly quality while the design is still at the conceptual stage. The straight-build assembly is validated by using statistical analysis through two case studies: a simple identical cylindrical-component assembly and a practical non-identical cylindrical-component assembly. The variation propagation can be reduced significantly for the straight-build assembly, compared to the direct-build assembly without optimization. The results show how the variation propagation control is related to process noise and measurement accuracy. The simulation results also show that minimal variation can be achieved at reduced cost by properly selecting the accuracy of measurement, according to process procedures. The information obtained provides a practical and useful approach for design engineers. The potential applications of the straight-build assembly are also illustrated.

Object-oriented models for aero-engine assembly

Computerised assembly technologies are increasingly used in product design evaluation, performance analysis and manufacturing simulations. Assembly modelling is of fundamental significance to digital assembly implementations, which captures, represents and manages connection-relevant data. On making a survey of previous product assembly modelling approaches, this paper concludes that object-oriented methods are most suitable for describing complex assemblies. Subsequently, this paper develops a meta-model of product assembly using the class diagram, where physical components are aggregated into classes of part and assembly, and their associations are specified by classes of connection, constraint, tolerance, etc. Finally, this paper converts the class-diagram based assembly model into an object model for aero-engine assembly through mappings between classes and objects. The assembly models built in this study are of high modularity and extensibility, and comprehensively specify all the information required for assembly planning, operations, simulations and evaluations.

Computational Studies of the Unbalance Response of a Whole Aero-Engine Model With Squeeze-Film Bearings

The computation of the unbalance vibration response of aero-engine assemblies fitted with nonlinear bearings requires the retention of a very large number of modes for reliable results. This renders most previously proposed nonlinear solvers unsuitable for this application. This paper presents three methods for the efficient solution of the problem. The first method is the recently developed impulsive receptance method (IRM). The second method is a reformulation of the Newmark-beta method. In addition to these two time-domain methods, a whole-engine receptance harmonic balance method (RHBM) is introduced that allows, for the first time, the frequency domain calculation of the periodic vibration response of a real engine. All three methods use modal data calculated from a one-off analysis of the linear part of the engine at zero speed. Simulations on a realistically-sized representative twin-spool engine model with squeeze-film damper bearings provide evidence that the popular Newmark-beta method can be unreliable for large-order nonlinear systems. The excellent correlation between the IRM and RHBM results demonstrates the efficacy of these two complementary tools in the computational analysis of realistic whole-engine models.

A receptance harmonic balance technique for the computation of the vibration of a whole aero-engine model with nonlinear bearings

Current frequency-domain techniques for the rapid computation of the steady-state periodic vibration of unbalanced rotordynamic systems with nonlinear bearings are not suitable for realistic engine structures like aero-engine assemblies. In this paper, a whole-engine receptance harmonic balance method (RHBM) is devised that, for the first time, allows the frequency domain analysis of such a structure. The method uses the receptance functions of the linear part of the structure under non-rotational conditions, obtained from a one-off eigenvalue analysis, to set up the equations for the rotating nonlinear assembly. The unknowns solved for are the Fourier coefficients of the relative displacements at the nonlinear bearings plus a few extra unknowns. These latter unknowns enable solution of the problem in the presence of statically indeterminate rotors that have just one linear point support or none at all. Simulation tests on a realistically sized representative twin-spool engine showed excellent correlation with time-marching results obtained from the recently developed impulsive receptance method (IRM). It is demonstrated that, when used in conjunction with a time-marching solver like the IRM, the RHBM is a very powerful tool that should greatly facilitate the hitherto highly restricted nonlinear dynamic analysis of realistic engine structures.

Mapping residual and internal stress in materials by neutron diffraction

Neutron diffraction provides one of the few means of mapping residual stresses deep within the bulk of materials and components. This article reviews the basic scientific methodology by which internal strains and stresses are inferred from recorded diffraction peaks. Both conventional angular scans and time-of-flight measurements are reviewed and compared. Their complementarity with analogous synchrotron X-ray methods is also highlighted. For measurements to be exploited in structural integrity calculations underpinning the safe operation of engineering components, measurement standards have been defined and the major findings are summarised. Examples are used to highlight the unique capabilities of the method showing how it can provide insights ranging from the basic physics of slip mechanisms in hexagonal polycrystalline materials, through the materials optimisation of stress induced transformations in smart nanomaterials, to the industrial introduction of novel friction welding processes exploiting stress residual measurements transferred from prototype sub-scale tests to the joining of full-scale aeroengine assemblies. To cite this article: P.J. Withers, C. R. Physique 8 (2007).

Experimental Investigation into the Vibration Response of an Aero-Engine Rotor-Damper Assembly

This paper presents experimental results on the non-linear vibration response of a rotating assembly comprising a rotor, flexible bearing housing and oil film damper. For the latter, due consideration is given to the effects of oil-supply pressure, film-rupture pressure and end sealing. The results are compared with predictions based on the Harmonic Balance principle described in a complementary paper (1).

The Performance of a Sealed Squeeze-Film Bearing in a Flexible Support Structure

In this paper attention is given to empirically modelling the hydrodynamics of a tightly sealed squeeze-film bearing in a flexible support structure simulating an aero-engine assembly, with a view to assessing its damping performance. It is found that predictable experimental results are obtained by employing an end-leakage factor which relates the outlet pressure around the bearing circumference to the corresponding ‘long-bearing’ pressure. The present work complements that covered in an earlier paper (1), which was concerned with the performance of an open-ended or weakly sealed squeeze-film bearing in a similar support structure.