Air Turbine Starter Research Articles

Air turbine starter remaining useful life prediction for bearing based on an improved temporal convolutional network

The air turbine starter (ATS) is an equipment employed for initiating aircraft engines, in which rolling bearings play a central role. Predicting the remaining useful life (RUL) of rolling bearings constitutes a challenging task within the domain of prognostics and health management (PHM). Improving computational efficiency to predict the RUL of bearings is a core problem addressed in this paper, and thus, this paper introduces the parallel causal convolutional hierarchical dilated temporal convolutional network (HD-TCN). HD-TCN effectively captures long-term temporal dependencies and significantly enhances computational efficiency compared to serial convolutional recurrent neural networks (RNNs). In addition, the introduction of the feature data stacking (FDS) module allows features from different hierarchical levels and dimensions to participate in the prediction task, ensuring both computational efficiency and prediction accuracy. To consolidate the extracted multidimensional features, the network incorporates the matrix multiplication dimensionality reduction transformation (MMDRT) module, which reduces the dimensionality of the data and further improves the computational efficiency as well. The introduction of the MMDRT module resulted in reductions of 43.4% in root mean square error (RMSE). The proposed method achieved reductions in RMSE by 38.3% and 46.4% compared to the transformer and long short-term memory (LSTM) models, respectively. Finally, the effectiveness of the proposed method is validated using the XJTU-SY data set and civil aircraft bearing components RUL prediction test bench bearing data. The results show that the proposed approach can predict the RUL of bearings with high accuracy.

Outer casing structure design for the trisection turbine wheel burst of the air turbine starter.

The aviation regulations mandate that high-energy rotor components must possesses adequate containment capabilities. Ensuring the containment of the turbine wheel of the air turbine starter is of paramount importance. In this paper, the design thickness of the containment ring was determined and the containment ring deformation was given. Based on the design thickness and deformation of the containment ring, an outer casing structure design method was proposed by using FEM. Then, two containment tests were conducted for different distances between the containment ring and outer casing to validate the outer casing structure design method. The errors of the containment ring deformation are smaller than 7.5%, and the experimental results of the containment process are in accordance with the simulation, validating correctness of the outer casing structure design method. The containment ring deformation rate with the design thickness T = 10 mm is 115%. A safety margin of 1.05 is designed by considering the uniformity of containment ring deformation and the containment ring assembly error. The results illustrate that the deformed containment ring does not damage the outer casing, when the inner diameter of the outer casing is designed as 1.2 times the outer diameter of the containment ring.

Neck Structure Optimal Design of the Turbine Wheel for Containment Design of the Air Turbine Starter

The airworthiness standards of the transport category airplanes stipulate that the high energy rotor equipment must be of the sufficient containment capacity. It is of great importance to study the containment and weight reduction for the air turbine starter. In this paper, based on an OSF design, Kriging response surface model and MOGA algorithm, a neck structure optimal design method was proposed for the air turbine wheel. Using the optimal design method, the optimal structural parameters were suggested as the design parameters, and verified by the over-speed burst test. The maximum errors of the burst speeds between the experimental and design values are less than 2%, and the neck structure turbine wheel breaks in the neck as expected, validating the accuracy of the optimal design method. Then, the effects of turbine wheel burst modes on the containment were investigated quantitatively, and verified by the containment tests. Based on the experimental and simulation results, the containment design method was proposed for the neck structure turbine wheel. The results show that compared with the trisection wheel burst, the rim burst dramatically decrease the mass and initial kinetic energy of burst released fragments by 63.3% and 24.8%, thereby greatly reducing the thickness and the mass of the containment ring by 29.5% and 29.1%.

Study on the Optimal Design Method of the Containment Ring for an Air Turbine Starter

The airworthiness standards of transport category airplanes clearly stipulate that the equipment containing high-energy rotors must be shown by test that it can contain any failure of a high-energy rotor that occurs at the highest speed. The air turbine starter (ATS) is typical equipment containing high-energy rotors, and the manufacturers of ATS attach great importance to research on structural containment and weight reduction. In this paper, an optimal design method for a U-type containment ring is proposed. The method adopts the optimal Latin hypercube design, numerical simulation, response surface modeling, and genetic algorithm to achieve the multi-parameter optimal design of the containment ring section. By combining simulation and experiment, the influence weights of different structural parameters of the containment ring on the residual kinetic energy of debris and the containment ring volume were analyzed. The influence of different structural parameters of a U-type containment ring on containment results was studied, and a containment test was carried out to verify the containment capability of an optimized containment ring. The results show that the thickness of the containment ring has the greatest influence on the residual kinetic energy of the debris, and the weight ratio is 38%. The maximum radial deformation of the optimized containment ring can reach 22.3%, which means that the energy absorption effect of the containment ring on the disk fragments is significantly improved. With the same containment capability, the weight reduction effect of an optimized containment ring can reach 26.5%. The research results can provide weight reduction optimization methods and design theoretical guidance for U-type containment structures.

Remaining useful life prediction for bearing of an air turbine starter using a novel end-to-end network

An air turbine starter (ATS) is used to start an aircraft’s engine before the aircraft takes off, as part of which the rolling bearings are an essential but easily damaged component. Predicting the remaining useful life (RUL) of an ATS bearing is a key part of efficient engine maintenance. To improve the prediction accuracy of rolling bearings’ working in complex environments, this paper proposes a novel end-to-end network for RUL prediction based on parallel convolution and a bidirectional long and short-term memory (BiLSTM) network. The architecture is an integration of two parts: feature extraction and RUL prediction. For the feature extraction, a more tailored one-dimensional convolution neural network architecture has been adapted for multi-rate sensors in a parallel manner, and a multiscale feature stacking and mixing mechanism is further designed following the convolution operation to extract the most representative degradation feature. In the prediction part, environmental factors are added to the BiLSTM network together with the previously extracted degradation feature. Both parts of the end-to-end network can focus on valuable information without any prior knowledge due to utilization of an attention mechanism. A real data set is built to evaluate the performance of the proposed method, and the RUL predictive error percentage decreases by 1.02% compared with the existing algorithm.

A framework for modeling fault propagation paths in air turbine starter based on Bayesian network

Any minor fault may spread, accumulate and enlarge through the causal link of fault in a closed-loop complex system of civil aircraft, and eventually result in unplanned downtime. In this paper, the fault propagation path model (FPPM) is proposed for system-level decomposition and simplifying the process of fault propagation analysis by combining the improved ant colony optimization algorithm (I-ACO) with the Bayesian network (BN). In FPPM, the modeling of the fault propagation path consists of three models, namely shrinking model (SM), ant colony optimization model (ACOM), and assessment model (AM). Firstly, the state space is shrunk by the most weight supported tree algorithm (MWST) at the initial establishment stage of BN. Next, I-ACO is designed to improve the structure of BN in order to study the fault propagation path accurately. Finally, the experiment is conducted from two different perspectives for the rationality of the well-trained BN’s structure. An example of practical application for the propagation path model of typical faults on the A320 air turbine starter is given to verify the validity and feasibility of the proposed method.

Investigation on transient dynamics of rotor system in air turbine starter based on magnetic reduction gear

As an auxiliary mechanical device, Air Turbine Starter (ATS) uses compressed air as power source to start and drive the engine. It withstands the impact of high-pressure airflow during operation, which may cause collision between key components. For this reason, it is necessary to investigate the transient dynamics of ATS rotor system. However, different from the traditional dual rotor structure, ATS uses magnetic reduction gear (MRG) as a reduction unit, which involves multiple physical fields such as magnetic field and stress field, bringing challenges to transient dynamics analysis. In this paper, the magnetic interaction forces between various rotors are innovatively simplified into the form of springs, and added to the solution model to achieve the decoupling of multiple physical fields. On this basis, the transient displacement response of MRG-ATS has been analyzed using transient dynamics theory. The results indicate that the transient displacement of the rotor system has obvious characteristics of oscillation attenuation. The study reveals the feasibility of MRG-ATS application under transient shock.

Improving the start-up parameters of a gas turbine engine by adaptation the air turbine starter

The paper describes the process of optimizing the blades of a starter air turbine for a gas turbine engine launch system. This task was initiated by the necessity to use an existing turbine when starting a new engine. During the study, it was found that the turbine, although it ensures the conditions for the joint operation with the auxiliary power unit turbine and meet the strength constraints, it does not allow to start the engine within the required time. As a result of studies using mathematical optimization methods involving commercial programs, a variant was found to modernize the baseline turbine, which provides an acceptable value of torque on the shaft with an adequate start-up time at all operating modes with minimal design changes.

Remaining useful life prediction for the air turbine starter based on empirical mode decomposition and relevance vector machine

An air turbine starter (ATS) is used to start the aero-engine before an aircraft takes off, which plays a significant role in the reliable operation of the aero-engine and is critical to the flight security, so it is vital to monitor the health and predict the remaining useful life (RUL) for the ATS. This paper proposes a fusion framework based on the combination of empirical mode decomposition (EMD) and relevance vector machine (RVM). EMD is used to smooth out the non-stationary data by pattern decomposition, and the multiple intrinsic mode functions (IMF) which can effectively reflect the fault characteristics, are carefully selected from all IMFs by kurtosis index technique. RVM is used to train the selected smooth IMFs samples and establish a regression model for remaining useful life prediction. In addition, the subtraction clustering technique is introduced to reduce the samples scale and speed up the RVM’s training efficiency. The effectiveness of the proposed fusion framework is illustrated via an experiment of ATS, and the results show that the proposed method has satisfactory prediction performance.

Systems Engineering Methodology for Linking Requirements to Design Complexity and Manufacturing Trade Space Constraints

Aerospace system requirements over the last decade have continued to evolve toward higher levels of performance at lower cost, incurring a major challenge for system developers; how to balance conflicting performance and cost requirements and understand their impact on performance margins as well as the manufacturability characteristics of the design. This paper presents results of a case study performed on an aerospace air turbine starter system in which a top-level systems engineering methodology has been developed to help understand the impact that customer requirements and design decisions have on manufacturing trade space constraints. One of the major findings of this case study is that incremental increases in performance requirements can drive step change increases in manufacturing cost due to discontinuities in the material and process trade space, i.e. using titanium versus aluminum to meet temperature requirements or having to use investment versus sand castings to meet minimum thickness and tolerance requirements. Internally developed quantitative producibility analysis tools are also used to characterize the complexity and Design for Manufacturability (DFM) characteristics of the “similar to” baseline design to identify producibility improvement opportunities for the new design as part of the proposed systems engineering process to mitigate design reuse risks.

가스터빈 엔진용 공기터빈 시동기 성능에 관한 실험적 연구

Gas turbines for an aircraft have the start and restart capabilities within their flight envelop. It is an important item for engine qualification and substantiated with the test. Experimental investigations were carried out to find the relation between the corrected torque and the corrected rotating speed of an air turbine starter in this study. A dedicated air supply system for the air turbine starter and a special device to measure the torque and the rotating speed of the air turbine starter were developed and installed at the altitude engine test facility in Korea Aerospace Research Institute. Experimental results show that the relations between the corrected torque and the corrected rotating speed of the air turbine starter are linear and the inlet temperature and pressure conditions for the air turbine starter were found out to provide minimum required torque for the engine qualification test at various altitude. The start and restart tests for the currently developing engine were successfully performed using this experimental results.

Failure Analysis of an Air Turbine Starter

Air turbine starters (ATS) are used for the ground start of aircraft engines. This case history describes the failure of an ATS that occurred while starting a developmental gas turbine engine. Fractographic features indicated that few blades of the turbine rotor disc failed in a progressive mode while the remaining blades of the rotor disc indicated failure by overload. The rotor shaft also exhibited features of sudden overload. Analysis of the previous records revealed the observation of sparks developing while the starter was in operation. This indicated possibility of blade tip rubbing which resulted in fatigue crack initiation at the blade root leading to failure.

Reliability Case History of An Airborne Air Turbine Starter

Field failure data collected over a span of 7 years for airborne air turbine starters (ATS), which are used to start jet engines in aircraft, offer an opportunity for analysis and determination of reliability parameters. This paper presents; a) Changes in ATS equipment MTBF by year, b) Breakdown of removal causes by year, and c) Cdf of failure times.