Aero-engine Test Research Articles

Health estimation of fan based on belief-rule-base expert system in turbofan engine gas-path

Fan is an important rotating part in turbofan engine gas-path. The health condition of fan has a great impact on the health status of the whole aero-engine. Based on belief-rule-base, a novel health estimation model is proposed for fan in turbofan engine gas-path. In this model, the health condition of fan is reflected by the observable information which can represent the system health. In the process of health estimation, the expert knowledge is used fully to improve the precision and speed of the estimation. In the initial health estimation model, some parameters given by expert may not be accurate. To obtain the accurate estimation result, an algorithm for updating the parameters is proposed based on differential evolution algorithm. In order to verify the feasibility and accuracy of the proposed model, back-propagation neural network is applied to comparison. The newly proposed model is applied to an actual test in the aero-engine test bed, which is used to testify the validity of the health estimation model. This model can also provide a reference for the health estimation of turbofan engine gas-path.

An Approach for Estimating the Effect of Transient Sweep Through a Resonance

The difference of a stationary forced response situation of a turbine or compressor blade relative to a transient resonance sweep is well known and documented in the literature. Different approaches have been used to understand the effect on transient amplitude in comparison with forced response. The dependencies on damping levels and resonance passage speed have been noted. Estimates for a critical or/and maximum sweep velocity have been given. The understanding of transient response during resonance sweep is of practical importance for instance when running a certification stress test for an aircraft engine, where it needs to be decided upfront which acceleration rate (increase in rpm per second) to use to ensure that the maximum airfoil response that could be attained under stationary condition is being measured with sufficient precision. A second reason for understanding of transient response is the verification of correct, if relevant lower, component life usage during transient regimes in operation. This paper gives a proposal for a simple 1D method based on one degree-of-freedom (1DOF) system considerations for estimating the transient response dependency on the sweep velocity, damping levels, and resonance frequency. The method is verified with 3D analyses of more complex blade–disk structures, which have been validated with air jet excitation rig and aero-engine tests. Using the results of the 1DOF analysis, an estimate of the expected stationary resonance response increase can be formulated even in cases where the measured data are based on a significant deviation from the desired sweep velocity, where transient effects would be significant.

Icing test capabilities at DGA Aero-engine Testing

Since the 1960s, DGA Aero-engine Testing has built facilities to test and certify parts and equipment of aircraft and rotorcraft in icing conditions. For aerofoil or blade testing, a 2D test set-up has been developed. For engine tests, a free jet configuration is used. Until recently, the standard conditions for icing were associated with the presence of clouds composed of supercooled small droplets. Nevertheless, recent accidents and incidents have highlighted the danger of other icing conditions such as supercooled large drops (SLD), ice crystals and mixed phase which is composed of ice crystals and small droplets. So, current and future challenges include the ability to simulate these conditions. To generate droplets larger than 100 micrometres, a new atomiser has been developed and calibration methods have been modified in consequence. The next planned step is the generation of ice crystals and mixed phase.

Improvement of an Altitude Test Facility Capability in Glaciated Icing Conditions at DGA Aero-engine Testing

Improvement of an Altitude Test Facility Capability in Glaciated Icing Conditions at DGA Aero-engine Testing

The Research of Temperature Indicating Paints and its Application in Aero-engine Temperature Measurement

Temperature indicating paints (TIP) is a kind of special functional coating which measures the temperature distribution by judging the color changes of the paint film. It is widely applied in aero-engine testing to solve the problem of measuring the temperature profile of hot end components. In this paper, the methods of temperature indicating paints formula design, preparation process and painting process are studied firstly. Then a calibration system based on isotherm identification method has been specially designed to confirm the performance and characteristics of the paints. Certain type of multi-change TIP is taken as an example to illustrate the whole development process as well as the practical application of TIP in one aero-engine turbine component. It is proved that the paints attached firmly even in severe environment with high temperature and high velocity gas flushed and recorded the temperature profile successfully

The Design of the Test Control System of Small Piston Aircraft Engine

For the engine maintenance enterprises, the test of aeroengine test can detect the performance of the product more accurately, but the engine testing work is a weak link. Conventional piston aircraft engine test system is the simulation instrument, according to the observed by human eyes, manual way to complete data collection work, this test system is inefficient. The engine bench test automatic measurement and control and monitoring system based on computer control is the inevitable trend of its development. Data acquisition module transmits the real-time data from the engine sensor installed on the different parts to the PC through CAN bus and display on the PC. The engine test bed control system and data acquisition system simplifies the system structure and obviously improves the test level and efficiency of the system.

Sensitivity Analysis and Experimental Research on Ball Bearing Early Fault Diagnosis Based on Testing Signal From Casing

The ball bearings of an aero-engine are key parts that frequently fail, and it is very important to effectively carry out fault diagnosis of the ball bearings. However, in the present research work, the ball bearing faults characteristics are extracted mainly from the bearing house signals, it is well known that usually only the casing signals can be measured in practical aero-engine test, and the ball bearing faults characteristics will greatly weaken after transmitting to the casing from the bearing house, therefore, it is very important to extract the fault characteristics of ball bearings from casing vibration signals for the ball bearing fault diagnosis in the practical aero-engine. In this study, simulation experiments for ball bearing faults are conducted using two rotor experimental rigs with casings. In addition, by means of the impulse response method, the transfer characteristics from the ball bearings to casing measuring points are measured, and a sensitivity analysis is performed. Faults are created on the inner ring, outer ring, and ball of the ball bearings in the two experimental rigs. The ball bearing experiments are carried out, and the fault features are extracted by means of a wavelet envelope analysis. The experimental results indicate that, with high connection stiffness between the bearing house and the casing, there is little vibration attenuation. However, with low connection stiffness, the vibration attenuation is great. After the impulse vibrations caused by the ball bearing faults are transmitted to the casing, the casing vibration is very weak and is often submerged in other signals. However, the ball bearing fault characteristic frequencies can still be effectively extracted from the weak casing vibration signals by using a wavelet envelope analysis. The research results in this study provide an experimental basis for a ball bearing fault diagnosis based on a casing test signal from a practical aero-engine.

Evaluation of vibration stress of TA11 titanium alloy blade by quantitative fractography

Vibration fatigue is the main failure mode of compressor blade. Evaluating the vibration stress of blade that leads to cracking is very useful for analysis of vibration fatigue. In this paper, fatigue stress estimation methods by quantitative fractography were studied through experimental blade and in-service first-stage compressor blade in order to evaluate the initiation vibration stress of in-service blade. The analysis process of initiation vibration stress was established. The evaluating result of vibration stress of in-service blade subjected to centrifugal force and bending vibration stress agrees with aero engine test result. It is shown that the evaluation method can not only evaluate the equivalent fatigue stresses of different crack depths but also yield the initiation equivalent fatigue stress.

Aero-Engine Fault Diagnosis Using Improved Local Discriminant Bases and Support Vector Machine

This paper presents an effective approach for aero-engine fault diagnosis with focus on rub-impact, through combination of improved local discriminant bases (LDB) with support vector machine (SVM). The improved LDB algorithm, using both the normalized energy difference and the relative entropy as quantification measures, is applied to choose the optimal set of orthogonal subspaces for wavelet packet transform- (WPT-) based signal decomposition. Then two optimal sets of orthogonal subspaces have been obtained and the energy features extracted from those subspaces appearing in both sets will be selected as input to a SVM classifier to diagnose aero-engine faults. Experiment studies conducted on an aero-engine rub-impact test system have verified the effectiveness of the proposed approach for classifying working conditions of aero-engines.

An Experimental Study on the Interaction of Water Mist with Vertical/Horizontal Spray Flame

Spray fire is a major disaster for gas turbines and aero-engine test facilities. Previous studies demonstrated that small spray fires were difficult to extinguish with water mist. An experimental study of the process of water mist interacting with the small size spray fire was conducted in an open space. Studies on suppression of vertical spray fire and horizontal spray fire were carried out, respectively. Experiment discovered that a horizontal fame was more difficult to extinguish compared with the vertical using the same scenario, and implied that the coupling the dilution of fuel in the gas phase with the reduction of radiant feedback plays a predominant role in fire extinguishment.

Noise analysis of the turbojet and turbofan engine tests

Aerogine noise leads to environment pollution largely when aerogine is tested. In this paper, the power spectrum analysis method of the aeroengine test noise was discussed, and the noise measurement and analysis experiments of a turbojet engine and a turbofan engine tests were carried out. The noise level, main noise resource, and noise characteristics of the two turbojet and turbofan engines were analyzed. Meanwhile, the indoor noise and far-field noise of the turbojet engine were both measured, the noise spread characteristics were analyzed and the noise reduction performance of the test bench was evaluated. The noise generated by the turbojet engine test had the discrete characteristic of high frequency. The higher frequencies when peak values occurred were the blade passage frequencies and the noises with lower frequencies were the broad band noises, especially the jet noise, and the maximum of the peak values occurred at the basic frequencies or harmonic frequencies of the compressor. Meanwhile, the noises generated by the turbofan engine, focused on the high frequencies and the peak values corresponded to the rotation noise of the fan blades. The experimental results were consistent with the theory basically, which indicated that the aeroengine operating status information could be identified by the noise power spectrum analysis. In addition to the aeroengine noise reduction research, the noise power spectrum analysis could also be used to diagnose the fault of the aeroengine structure and performance. On the other hand, the indoor and far-field noise measurement experimental results implied that the noise was suppressed from 136 dB to 85 dB and could provide the reference to the noise reduction design of the aeroengine test bench.

Development and validation of a simulator for wireless data acquisition in gas turbine engine testing

Owing to its cable-free deployment, wireless sensor networks (WSNs) have drawn great attention as a new technique for industrial data acquisition. However, the harsh environment of the gas turbine engine provides a number of challenges to deployment of wireless sensors. A definitive study of the impact of harsh environments on WSNs is currently lacking, which represents an obstacle to WSN's deployment in safety-critical industrial instrumentation and automation. In this study, the authors report the test results of applying WSNs to data acquisition in gas turbine engine testing and the development of a realistic software simulator with the purpose of de-risking the wireless data transmission technology in a project called WIDAGATE (wireless data acquisition in gas turbine engine testing). This study provides an overview of the simulation platform developed and investigates how small-scale tests of a WSN deployed on a real engine were used to validate and improve the simulator platform. This work proposes realistic modelling of the physical layer (radio channel) when subject to interference in harsh industry environment during aero-engine testing. Based on the validated, realistic physical layer model, different medium access control protocols are simulated to demonstrate how this improved simulator can be used to select an appropriate protocol.

Sensor Fault Detection and Identification Method with KPCA in the Process of Aero-Engine Ground Testing

This paper focuses on Kernel Principal Component Analysis (KPCA) in order to solve the problem of sensor fault detection and identification without linear relationship between sensors. After samples are projected into high-dimensional space, new Principal Component Analysis (PCA) model is established in the kernel principal component eigenvector space. By the contrast with SPE, Hotelling T2 is an appropriate parameter to detect sensor fault because it is more sensitive to sensor failure. The contribution of different sensor to Hotelling T2 is utilized to identify sensor fault for the faulty sensor’s contribution is large than others significantly. Finally, the proposed method is illustrated by the sensors of oil-providing system in the process of aero-engine ground testing. Experiment results show the applicability and effectiveness of the proposed method.

Photoluminescence for quantitative non-destructive evaluation of thermal barrier coating erosion

The need to increase the operating temperature of gas turbines to provide improved efficiency has led to the use of thermal barrier coatings on components in the hot section of the engine. In certain operating regimes, particularly in environments with contaminated intake air, degradation of the coating can occur by gradual thinning from the surface ultimately leading to complete failure. Current inspection routines cannot identify these gradual degradation mechanisms. The introduction of rare-earth oxides doped phosphorescent layers into standard thermal barrier coatings enables a non-destructive evaluation method to quantify the extent of the damage. The first detailed characterisation of this technique has been conducted using YSZ:Eu and YSZ:Dy. It has been shown that a rapid, quantitative assessment of the erosion damage can be attained by imaging of the phosphorescence. After image processing the thickness profile of such a sensor coating was reconstructed and the depth of an erosion crater was measured with a precision equivalent to the thickness of the doped layers (approximately 30μm in the present case). The overall depth of the crater was found to be 60μm a value that was corroborated by two independent measurements. Testing on a thermal gradient rig and on an aeroengine test bed has demonstrated that erosion sensors can be constructed whilst retaining the functional properties of the coating.

The Design of Embedded AeroEngine Measurement and Test System Based on ARM and FPGA

Present Measurement and test system for aeroengine rig testing is primarily based on DSP and PC104 industrial computer, which have the disadvantages of large volume, high power consumption, single function and less-generic. So it is a valuable job to promote the performance of the system employing the latest methods of collaborative design and embedded hardware and software technology. For designing of the new type improved aeroengine test system, a hardware and software co-design strategy is employed. After a thorough trade-off analysis and comparison among different hardware and software systems, an embedded aeroengine test system based on ARM and FPGA is designed, by using S3C2440A CPU with ARM920T core and FPGA from Xilinx as fundamental hardware data acquisition and process platform, using Linux as real time operating system. The data transmission between ARM and FPGA take the path of dual-port RAM, during which the read-write operation is coordinated by means of interruption. The system uses U-Boot to initialize hardware and load operating system. FPGA is used as foreside of data acquisition system, which sampling parameter setting is loaded by reading configuration file during start-up and read into inner register by SPI bus. Data is exported from flash-chip of test system by means of U-disk or network, and analyzed in PC equipped with specialized software. Strong post-proceeding capacity for multi parameters of aeroengine rig testing can be realized, especially for dynamic signal analysis in time domain, frequency domain. Because of the use of the new platform, a big promotion has been achieved. I) the capacity of data processing increases by 15%. II) The new system allows numbers of the sampling channels to double. III) Abundant functions of software can realize more professional, intelligent and generic tests. IV) Sampling frequencies increases by 20%, meeting the demand of monitoring dynamic random signals such as noise and vibration, on fluctuating pressure with wide frequency band. The embedded aeroengine test system based on ARM and FPGA is successful and the prototype is manufactured and tested. It is found that the performance of the new system is promoted significantly, which shows the effectiveness and reliability of the method employed.

Research on Aeroengine Rub-Impact Fault Analysis Based on Wavelet Scalogram Statistical Feature

The characteristics of the continuous wavelet transform scalogram of the aeroengine vibration signal could show the fault symptomatic in the 2-dimensional space and identify the rub-impact fault of the aeroengine. In order to get the precise feature for fault analysis, the statistical features of the scalogram which incorporated the Tamura vision features were proposed to diagnose the aeroengine rub-impact faults quantitatively. The experiments on the aeroengine test data demonstrate these statistic characteristics of the scalogram effectively diagnose the rub-impact faults.

The Order Tracking Study of Variant Speed Process of Aeroengine Vibration Signal

Order tracking is an important method to analyze the response characteristics of rotating machinery for fault diagnosis and condition monitoring in rotating machinery. Order tracking method overcomes the shortcomings of traditional resampling and FFT method. A new use based on the order tracking analysis is proposed in this paper, the computed order tracking method is applied to analyse the dynamic vibration signals during aeroengine start-stop process.In the aeroengine test, the fault characteristic of rotating shafts is related to the rotating speed,vibration will be more complicated and diversified with the increasing speed during run-up process, and has characteristics of periodicity and multiple frequency. It is of vital critical to extract characteristic information from exterior measurement vibration signal and get interior fault information. Applying the order tracking in the analysis of aeroengine signals shows that it can extract the fault characteristics and realize the state monitoring.

Aero-engine test facility information instantly accessible

Aero-engine test facility information instantly accessible

A three-dimensional finite element investigation of the bolt stresses in an aero-engine Curvic coupling under a blade release condition

Curvic couplings transmit torque between parallel in-line shafts or turbine/compressor discs. They are used extensively within the aero-engine industry but can also be found in industrial gas turbines. The manufacture of Curvic couplings involves the precision cutting and grinding of mating teeth on the adjacent ends of the components; the assembly is then clamped together with bolts. The use of Curvic couplings in engineering transmission components is relatively widespread, although the publication of work in the open literature is currently limited. An attempt has been made to investigate the factors influencing the load imparted to a fan Curvic coupling in a large aerospace gas turbine. Owing to the very complicated nature of the current problem, some geometric and especially loading simplifications have been necessary. The results presented provide an initial solution to the problem of the three-dimensional numerical modelling of a fan Curvic coupling during a blade release event. This work is intended to provide data to help make decisions at the design stage and, together with aero-engine fan blade-off tests, will contribute to an improved design of Curvic couplings. The current work has been carried out using the three-dimensional finite element elastic-plastic contact method in an attempt to achieve realistic displacements of the fan Curvic teeth and bolts.

Reducing cost, time and risk in aero-engine compressor testing

There is constant pressure to reduce engine development cycles to minimize costs and bring forward the revenue earning part of the engine's life. As cost and time are designed out, the risk of performance shortfall must be minimized by bidding efficiencies from demonstrated technology. This requires a large-scale ongoing advanced development program. In compressor development, high-speed tests are unavoidable but are expensive; low-speed rigs are easier to instrument and provide a cost-effective filter for the high-speed designs. The large-scale, low- speed compressor at Cranfield is one of only four worldwide. Recent investment in data reduction software has greatly reduced the test/analysis cycle time.