Engine Ground Test Research Articles

Analysis of factors affecting the stability of aircraft engine test

Abstract Although the aircraft is in a braking and shutdown state during engine testing, there may still be situations where the aircraft slides or deviates during the development process, which affects the safety of the aircraft. This article establishes a force analysis model for an aircraft engine test and proposes a single-engine testing force analysis method based on dual-engine testing force analysis. Factors such as the friction coefficient of pavement, wind speed, and aircraft parking slope are taken into account in the calculation. The relationship between different influencing factors and ground stability is studied in the article. The article provides a reference for the weight center of gravity limitation of aircraft under engine ground testing conditions.

Estimation Method of Charged Particle Concentration in Aircraft Engine Exhaust Based on Electric Field Detection

Aircraft engines, serving as the power core of aircraft, also constitute a significant source of potential malfunctions. The charge level of exhaust particles from aircraft engines serves as a crucial indicator of engine malfunction severity. This paper introduces a method for estimating the charge of exhaust particles based on electric field detection to monitor charged particles in the exhaust of aircraft engines. Initially, a mathematical model for estimating the charge of exhaust particles based on Gauss’s theorem is presented. Subsequently, an exhaust electric field induction device is designed, and the distribution of electric field sensors is studied, providing an overall design for the exhaust particle charge measurement system. Finally, the proposed method for estimating the charge of exhaust particles is analyzed through finite element simulation. The results indicate that the introduced aircraft engine exhaust particle charge estimation method based on electric field detection exhibits high accuracy and effectiveness. It offers a novel means for monitoring engine operation faults in aviation, with the potential for application in engine ground testing to further investigate engine state characterization technologies based on exhaust particle monitoring.

A scheduling model of civil aircraft maintenance stand based on spatiotemporal constraints

PurposeMaintenance stands are the most valuable maintenance resources and provide the necessary maintenance space and maintenance facilities for aircraft maintenance. To expand the maintenance market, maintenance, repair and overhaul (MRO) urgently need to achieve a reasonable schedule between aircraft maintenance requirements and maintenance stand capability to improve aircraft maintenance continuity and reduce the risk of scratching due to aircraft movement. This study aims to design a maintenance stand scheduling (MSS) model based on spatiotemporal constraints to solve the problem of maintenance stand schedules.Design/methodology/approachTo address the problem of maintenance stand schedules, this study introduces mixed-integer programming algorithm to design the MSS model on the basis of classical hybrid flow shop structure. When designing the optimization objective function of MSS modeling, the spatiotemporal constraints are mainly considered. Specifically, first, the spatial constraints between maintenance stands are fully considered so that more aircraft can be parked in the workshop. Second, the optimization objective is designed to minimize the number of aircraft movements by defining multiple maintenance capabilities of the stand. Finally, a solution based on spatiotemporal constraints is proposed in the solving process.FindingsA set of MRO production data from Guangzhou is used as a test data set to demonstrate the effectiveness of the proposed MSS model.Originality/valueThe types of maintenance stands are defined and divided into four categories: fixed stand, temporary stand, half-body stand and engine ground test stand, which facilitates optimal modeling; a new scheduling model is designed considering both temporal constraints and spatial constraints, which can improve both the utilization of maintenance stand and safety (reduce the risk of scratching between aircraft).

Unsupervised Fault Detection Driven by Multivariate Time Series for Aeroengines

Aeroengine fault detection is extremely significant to ensure flight safety. However, it still poses a vast challenge due to the complexity of aeroengine systems. In this paper, an unsupervised deep autoencoder (DAE) with dimension fusion function (DFF) method (DFF-DAE) was proposed to effectively detect aeroengine faults based on multivariate time-series data. The proposed method does not rely on mathematical models and expert experience to automatically extract the hierarchical representation features of raw data. The DFF-DAE has a three-layer autoencoder with its first encoding layer incorporating a DFF, which is developed for multivariate time-series fusion before encoding. A case study of aeroengine rolling bearing locking fault was conducted on the turbofan engine ground test data composed of vibration and rotational speed time-series data in variable working states. The results indicated that DFF-DAE succeeds in efficiently employing multivariate time-series data to perform accurate fault detection. Compared with other state-of-the-art methods, DFF-DAE yields superior predictive ability and detection accuracy. Furthermore, DFF-DAE provides application potential for online fault detection because it is effective in variable working states of the aeroengine.

Machine learning augmented multi-sensor data fusion to detect aero engine fan rotor blade flutter

Abstract Flutter-induced fatigue failure investigation of the fan blades of aero-engines necessitates extensive testing. During engine ground testing, strain gauges on rotor fan blades and casing vibration sensors were employed to investigate structural dynamic aspects. The correlation between strain sensor signals and fan casing vibration signals allowed the diagnosis of fluttering fan blades. For automated flutter detection during engine development testing, a machine learning-augmented information fusion methodology was developed. The method analyses casing vibration signals by extracting time-domain statistical features, intrinsic mode function characteristics through empirical mode decomposition, and recurrence quantification features. Feature vectors obtained from a relatively large set of engine tests were subjected to dimension reduction by applying machine learning techniques to rank them. Reduced feature vector space was labelled as “flutter” or “normal” based on the correlation of rotor strain gauge signals. In addition, the labelled feature vectors were employed to train classifier models using supervised learning-based algorithms such as Support Vector Machines, Linear Discriminant Analysis, K-means Clustering, and Artificial Neural Networks. Using only vibration signals from the casing, the trained and validated classifiers were able to detect flutter in fan baldes with a 99% probability during subsequent testing.

Aerodynamic design optimization of a bellmouth shaped air intake for jet engine testing purposes and its experiment based validation

Jet engine ground tests are carried out with bellmouth shaped air intakes in order to measure the mass flow rate and the inlet flow quantities while supplying the engine an undisturbed flow. Although there are a variety of design standards and academic guidelines for the design of bellmouths, they can be designed to reach a lower total pressure loss coefficient, a less disturbed radial velocity profiles for the engine and a less thickened boundary layer at the engine inlet. This enhanced design can be achieved with the help of optimization algorithms and computational fluid dynamics (CFD) computations thanks to the increasing average computational power and simplicity of the flow problem. In this study, a genetic algorithm based optimization method and a RANS solver under a commercial software platform are applied to find a bellmouth design with less loss and less disturbed flow. An elliptical bellmouth lip profile with a linear extension part is defined with parametrization and a wide range of parameter space is investigated during the design work. Optimum design candidates are presented comparatively regarding the design purpose. The selected design candidate is produced and tested for CFD validation.

Real-time communication for ground testing of cryogenic engines and stages of Indian space missions

Real-time communication for ground testing of cryogenic engines and stages of Indian space missions

Instrumentation design considerations for automatic ground testing of rocket engines

Instrumentation design considerations for automatic ground testing of rocket engines

Quasi-0D-Model Mapping of Reflected Shock Tunnel Operating Conditions

Reflected shock tunnels have been widely used for ground testing of hypersonic airbreathing engines. These facilities are able to replicate the total enthalpy and pressures experienced along hypersonic flight trajectories. Designing the relevant operating conditions is complex, and extensive guidance about operation condition design in reflected shock tunnels is scarce. To facilitate the operation of a reflected shock tunnel, it may be advantageous to develop a database of attainable conditions and the operation parameters required to achieve them. For this, a model to calculate global thermodynamic states and shock speeds also accounting for piston location and tube length (quasi-0D-model) is proposed. This model uses the NASA Chemical Equilibrium with Applications code to solve real gas and high-temperature effects. A number of conditions are calculated to produce maps of operating conditions. As test cases, the reflected shock tunnel under development at Tokai University, and T4 at the University of Queensland are used. Maps obtained sweeping rupture pressure or compression ratio, and initial test gas pressure for different driver compositions are presented. This methodology can be adapted to similar facilities. Moreover, observation of the presented maps provides a quick reference of the influence of each parameter when modifying existing conditions or fine-tuning tunnel operation.

Development of an automated hydraulic brake control system for testing aircraft turboshaft gas turbine engines

To absorb the power generated by a free turbine, hydraulic brake systems of various designs are used in ground tests of aircraft turboshaft gas turbine engines. Ground tests of aircraft turboshaft gas turbine engines with the use of such hydraulic brakes can result in emergency modes of automated engine control in the area of operation of a free turbine speed regulator. Mismatch between the hydraulic brake loading characteristics and the loading characteristics of the rotor driven by a free turbine of the engine is the main cause of emergency operation of automated control systems.The presented experimental loading characteristics of the hydraulic brake and the helicopter rotor show their significant difference in terms of gain. To eliminate this difference, a possibility of modeling dynamic parameters of rotors by simple automation means was considered. To solve this problem, a linear dynamic model and a block diagram of an automated hydraulic brake control system for ground testing of turboshaft gas turbine engines were elaborated. The law of regulation of the hydraulic brake loading was substantiated. A structurally dynamic diagram of the developed automated control system was presented and calculation formulas for determining the regulator parameters were given. Transient characteristics of the hydraulic brake unit without automation means and with the use of an automated loading control system were calculated. The presented calculation results have shown that the use of automation make it possible to fully emulate characteristics of the helicopter rotors

The influence of the applied window function and sampling frequency on the assessment accuracy of the turbine engine in flight control condition based on its ground tests

The article presents the basis of the method allowing to assess the state of control condition of a turbine jet engine during the plane flight when the input signal to the engine is unpredictable interference signal „z". Method is based only on signals acquired during engine ground test when the input signal is „w" delivered by technical support using the engine control lever (DSS). The control state of the engine both from the set value „w" and „z" is expressed by the quotient of its cross power spectral densities (in frequency domain). The way of transition from the frequency domain to the time domain was presented, it allows to obtain step responses of engine from „z" and „w", greatly facilitating the interpretation of the obtained results.. The analysis of the influence of choosing types of the window function and signals sampling frequency on the accuracy of the proposed model has been carried out.

Review of engineering solutions applicable in tests of liquid rocket engines and propulsion systems employing hydrogen as a fuel and relevant safety assurance aspects

The review presents the author's papers on specific features of experimental development of oxygen-hydrogen liquid rocket engines (LRE), namely the 11D56, 11D57, RD0120, KVD1, and a number of propulsion units and power plants, as well as compares some data on propulsion development activities with relevant data obtained abroad. Also has been shown a role of model studies, component-level tests of engine units and systems, including those performed at simulated flight conditions, and integrated tests in support of experimental development of advanced engines and propulsion systems designed for rocket upper stages. There have been considered techniques and equipment intended to ensure safety of ground testing of rocket engines and power plants involving the use of effective diagnostic systems and emergency protection systems.

Application of thermodynamic laws on a military helicopter engine

Abstract By definition, a turboshaft engine is simply a gas turbine used to deliver shaft power such as to a helicopter rotor. This paper presents the energetic and exergetic analyses of a turboshaft engine which is used for military helicopter at various load values. The main objectives of this study are to assess the performance of the engine and to calculate the amount of exergy destructions in the components of the engine. The calculations were performed at four different load values (284 N·m for test #1, 436 N·m for test #2, 547 N·m for test #3 and 579 N·m for test #4) and all analyses were performed and presented on the basis of the experimental engine ground test data together with a theoretical thermodynamic performance evaluation. The exergetic performance parameters, such as the relative exergy destruction, the fuel depletion ratio, the productivity lack, the improvement potential were also investigated. The exergy destruction values for the combustion chamber, which has the highest exergy destruction among all the components, were calculated as 1170.30 kW, 1474.50 kW, 1650.12 kW, and 1702.50 kW for tests #1, #2, #3 and #4, respectively. In addition, the ratio of the exergy destruction to the total exergy destruction was obtained to be the highest in the combustion chamber (88.81%) at test #2; whereas this ratio was found to be the lowest in the high-pressure turbine (0.75%) at test #2.

Hydrogen Containment Process for Nuclear Thermal Engine Ground Testing

Nuclear thermal propulsion is an enabling technology for delivering large payloads to Mars, and ground testing of a nuclear thermal engine is an important part of the development. A critical issue in nuclear thermal engine ground testing is the presence of a large amount of hot hydrogen exhausted during the tests, which needs to be totally contained. A hydrogen containment process is proposed in this study in which an oxygen-rich burner and a tubular heat exchanger are employed for hydrogen containment. The objective of this effort is therefore to demonstrate that this new process could achieve the goal of total hydrogen containment for nuclear thermal engine ground testing. A multidimensional pressure-based multiphase computational fluid dynamics methodology was used to conceptually size the oxygen-rich burner, whereas a one-dimensional thermal analysis methodology was used to conceptually size the heat exchanger. Subsequently, a steady-state operation of the entire hydrogen containment process (from the pressure vessel through the nozzle, diffuser, burner, and heat exchanger) was simulated numerically, with the aforementioned computational fluid dynamics methodology. The computed results show that the exhaust hydrogen is reduced to meet the design goal at the end of the heat exchanger, demonstrating the hydrogen containment capability of the proposed process.

Development of intelligent peripheral devices of control and emergency protection systems for ground testing of liquid-propellant rocket engines

One of the promising trends in the improvement of stand test data management and control systems and emergency protection systems involves the development of intellectual peripheral devices that provide communication with test articles. Due to the incorporation of their own processors in such devices they can solve problems of receiving data from sensors and initiating lower level control actions (independently from the master controller) on the actuators of controlled objects, which enhances the reliability and quality of control. The paper presents the latest developments directly related to the control of liquid-propellant rocket engine (LRE) parameters during stand tests, i.e. control of electro-hydraulic tilt actuators of LRE combustion chambers; control of stepping motors for the regulation of mixture ratio and control of vernier engines; receiving, processing and recording of signals from turbine flow meters and turbopump RPM sensors.

Strip distortion generator for simulating inlet flow distortion in gas turbine engine ground test facilities

A methodology has been developed to generate a non-uniform/distorted inlet flow field to test a gas turbine engine in ground test facilities. The distorted flow field is generated by positioning radial and circumferential strips of varying widths upstream of the Aerodynamic Interface Plane. The interacting wakes from these strips are used to generate a given target flow field. The approximate superposition of these wakes is investigated and used to construct the strip arrangement which is subsequently validated by computing the flow field by solving the Navier–Stokes equations. The strip geometry designed using the present methodology is able to produce the target Mach number distribution with a root-mean-square error of 5.06%.

Liquid-propellant rocket engine online health condition monitoring base on multi-algorithm parallel integrated decision-making

This study reports multi-algorithm parallel integrated decision-making for liquid-propellant rocket engine online health condition monitoring to improve reliability and safety, especially for next-generation reusable engines. Fusing multi-algorithm detection information to judge liquid-propellant rocket engine condition is multi-algorithm parallel integrated decision-making main task, and multi-algorithm judgment problem is its central issue; i.e. how to make a global judgment from judgment results of different fault detection methods. Considering opportune fault detection, adequate rocket engine information exploitation, and reliable condition judging, the multi-algorithm parallel integrated decision-making framework for problem definition is presented along with a multi-algorithm parallel integrated decision-making judgment model. For more reliable, efficient global judgment, a method based on the Bayes’ risk function integrating multi-algorithm prior information is adopted. The proposed approach is validated with liquid-propellant rocket engine ground testing data. The results show that the multi-algorithm parallel integrated decision-making judgment model gives very effective and reliable performance relative to the voting method, successfully solving multi-algorithm judgment problems and meeting practical engineering needs.

Concept study of a hydrogen containment process during nuclear thermal engine ground testing

A new hydrogen containment process was proposed for ground testing of a nuclear thermal engine. It utilizes two thermophysical steps to contain the hydrogen exhaust. First, the decomposition of hydrogen through oxygen-rich combustion at higher temperature; second, the recombination of remaining hydrogen with radicals at low temperature. This is achieved with two unit operations: an oxygen-rich burner and a tubular heat exchanger. A computational fluid dynamics methodology was used to analyze the entire process on a three-dimensional domain. The computed flammability at the exit of the heat exchanger was less than the lower flammability limit, confirming the hydrogen containment capability of the proposed process.

극초음속 공기흡입식 추진기관 지상 시험설비의 구성 및 특성에 관한 연구

극초음속 공기흡입식 추진기관 지상 시험설비의 구성 및 특성에 관한 연구

Failure Analysis of Ball-Bearing of Turbo-Pump Used in Liquid Rocket Engine

Rolling contact bearings often referred as antifriction bearings are found in many applications where rotating components are involved. Extreme operating conditions, counterfeit or inferior quality bearings, inadequate lubrication, etc often lead to bearing failures. Each rolling contact bearing failure leaves traces of evidences on what caused its failure. Failure analysis of one such bearing is the subject of this paper.One of the engine ground tests was aborted due to the failure of a self-aligning deep groove ball bearing used in turbo-pump of a liquid rocket engine. Series of engine ground tests are conducted as a part of injector acceptance for a liquid rocket engine. The bearing failure occurred in the seventh engine test of one of such series of ground tests. The bearing mentioned here is made of SAE 52100 steel. Post-test hardware inspection revealed that the bearing and the dynamic seals on either side of the bearing are in failed condition. Inner race of bearing was found blackish in appearance with indentation and corrosion marks. Localized black spots were observed in outer race. Bearing balls were found in deformed condition. The paper highlights the failure analysis of the bearing, root cause of the bearing failure and recommendations to avoid such failures.