Jet Engine Operation Research Articles

Development of Mathematical Support and Software for Ballistic Analysis and Optimization of Active-Missile Projectile Parameters

The paper presents the results of developing mathematical and software support for internal and external ballisticsmodelling, as well as optimizing the parameters of an active-reactive projectile. A complex mathematical model of active-reactive projectile ballistic analysis includes the problem of external ballistics, the problem of internal ballistics inside the gun barrel and the problem of internal ballistics of a solid-fuel jet engine. The problem of active-reactive projectile parameteroptimization is to increase the flight range with respecttomotion stabilitycondition along the entire trajectory. Based on the mathematical model of ballistic analysis, the algorithms for solving a multi-criteria problem of active-reactive projectileparameteroptimization have been developed. The developed software package includes a block of calculation modules implementing mathematical models and computational algorithms, a database of projectile parameters and simulation results, a block for visualization the computational experiment results in the form of diagrams and tables. The software package can be used in the design and optimization of the projectileparameters of artillery systems implementing the active-reactive throwingprinciple. The results of mathematical modeling and optimization of parameters are considered using the example of the designed active-reactive projectile for the 152 mm artillery system. To improve the projectilestability on the trajectory during jet engineoperation, it is proposed to install ribs at an angle to the projectile axis on the inner surface of the nozzle so as to create extra torque. Based on the developed model, the optimal characteristics of firing an active-reactive projectile of caliber 152 mm are determined. The results of internal and external ballisticsproblem solutionfor an active-reactive projectile obtained by means ofthe software package for ballistic process modeling are presented. The main problem of internal ballistics inside the gun barrel, the problem of internal ballistics of a solid-fuel jet engine, the direct problem of external ballistics of an active-reactive projectile and the study of the projectile motion stability along the trajectory are solved. Optimal parameters of internal and external ballistics, providing the maximum firing range of an active-reactive projectile with respect toitsmotionstability along the entire trajectory, are found.

Jet Engine Turbine Mechanical Properties Prediction by Using Progressive Numerical Methods

The propulsion system for an aircraft is one of its most crucial systems; therefore, its reliable work must be ensured during all operational conditions and regimes. Modern materials, techniques and methods are used to ensure this goal; however, there is still room for improvement of this complex system. The proposed manuscript describes a progressive approach for the mechanical properties prediction of the turbine section during jet engine operation using an artificial neural network, and it illustrates its application on a small experimental jet engine. The mechanical properties are predicted based on the measured temperature, pressure and rpm during the jet engine operation, and targets for the artificial neural network are finite element analyses results. The artificial neural network (ANN) is trained using training data from the experimental measurements (temperatures, pressure and rpm) and the results from finite element analyses of the small experimental engine turbine section proposed in the paper. The predicted mechanical stress by ANN achieved high accuracy in comparison to the finite element analyses results, with an error of 1.38% for predicted mechanical stress and correlation coefficients higher than 0.99. Mechanical stress and deformation prediction of the turbine section is a time-consuming process when the finite element method is employed; however, the method with artificial neural network application presented in this paper decreased the solving time significantly. Mechanical structural analyses performed in ANSYS software using finite element modeling take around 30–40 min for one load step. In contrast, the artificial neural network presented in this paper predicts the stress and deformation for one load step in less than 0.00000044 s.

Case study‐based learning using a computational tool to improve the understanding of the jet engine cycle for aerospace engineering degree students

AbstractIn the current paper, a methodology combining a case study with a computational tool for aerospace engineering students is presented and discussed. The aim of this methodology is to improve the understanding of jet engine's operation through their thermodynamic cycle analysis, particularly focused on the effects of the main boundary conditions for an aircraft engine: altitude and flight velocity (or Mach). Additionally, the organization of the methodology as a case study performed in groups helps to facilitate student engagement, as well as the development of soft skills, such as teamwork ability. The experience of this methodology over the last 5 years shows that the activity is generally well perceived by the students, and also that there is a correlation between the engagement in this activity and the overall results achieved in the subject, confirming that the methodology helps to improve students' comprehension of the concepts behind engine performance. However, a few points of improvement for the near future are identified.

Mobile engine test station for preparation and operation of miniature turbine jet engines for flying aerial targets

The work presents description and operation of the mobile engine test station, designed for the miniature turbine jet engines with a maximum trust below 200 N. The engine test bed allows us to monitor the condition of the engine used to drive remotely controlled flying aerial targets or military unmanned aircraft. According to military (Department of Defence) requirements, the designed engine test station is mobile, it can be used in military battlefield conditions and it meets safety precautions and military transport requirements. The reason of the engine investigations was the shortage and lack of information on the engine capability and suitability to work in the field conditions, and first of all on its limitations. The designed engine test station successfully completed tests in laboratory as well as in military field conditions and nowadays it is an integrated part of the Aerial Flying Target System called the ZOCP-JE2 that is designated for the engine’s monitoring and checking before the flight. Keywords: life cycle monitoring, miniature turbine jet engines, diagnostic procedures

Аналіз роботи керуючих реактивних двигунів верхнього ступеня РН «Циклон-4М» при запусках та зупинках маршового двигуна

Аналіз роботи керуючих реактивних двигунів верхнього ступеня РН «Циклон-4М» при запусках та зупинках маршового двигуна

Modelling Fuel Injector Spray Characteristics in Jet Engines by Using Vine Copulas

SummaryThe emission requirements for jet engines are becoming more stringent and the combustion process determines pollutant emissions. Therefore, we model the distribution of fuel drops generated by a fuel injector in a jet engine, which can be assumed to be a five-dimensional problem in terms of drop size, x-position, y-position, x-velocity and y-velocity. The data are generated by numerical simulations of the fuel atomization process for several jet engine operating conditions. In combustion simulations, the variables are usually assumed to be independent at the start of the simulation, which is clearly not so as our data show. The dependence between some of the variables is non-monotone and asymmetric, which makes the modelling task difficult. Our aim is to provide a realistic parametric model for the dependence structure. For this, we employ vine copulas which provide a flexible way to construct a multivariate distribution function. However, we need to use non-standard bivariate copulas as building blocks. Using this copula representation enables us to create realistic samples of fuel spray droplets which improve the prediction of the combustion process and the pollutant emissions. Moreover, this approach is significantly faster than solving the set of differential equations describing fuel disintegration.

The physics of twin-fluid jet-in-crossflow at atmospheric and jet-engine operating conditions

Efforts to mitigate jet engine emissions produced a class of swirl-stabilized combustors in which a rich pilot-flame in the center of the swirl-cup anchors an outer-annulus of lean-premixed main-flame. Fuel distribution within the annulus must be carefully controlled to allow stable combustion while avoiding excessive swirl-cup heating and flashbacks. This was traditionally achieved by placing plain jet-in-crossflow (JICF) fuel injectors around the swirl-cup; however, a recent increase in engine operating pressure and temperature along with demand for leaner fuel-air mixtures made the traditional approach untenable. Hence, modern swirl-cup designs begin to adopt a new fuel-injection technique called the “twin-fluid JICF (TF-JICF)” where a sleeve of air is co-injected with the liquid jet to modify its spray-pattern. TF-JICF is a nascent variation of the JICF that is not well understood, especially at elevated pressures. Hence, an experimental investigation of TF-JICF spray behaviors was performed by our group, covering the operating conditions of 1.5–9.5 atm in crossflow pressure, 175–1050 in crossflow Weber number, 5–40 in momentum flux-ratio, and 0%–150% in air-nozzle pressure-drop, at the crossflow temperature of 150 °C and velocity of 75 m/s. Part 1 of the investigation’s results, which identified four distinct flow regimes and nonmonotonic penetration trends in TF-JICF, was published in the work of Tan et al., “The regimes of twin-fluid jet-in-crossflow at atmospheric and jet-engine operating conditions,” Phy. Fluids 30, 025101 (2018). The current paper expands upon the previous report by elucidating key spray features and potential mechanisms (e.g., transitions between crossflow-driven atomization, air-driven shear-atomization, and air-driven prompt-atomization) within each TF-JICF regime, thereby providing a conceptual framework of TF-JICF for future studies.

Evaluation of jet engine operation parameters using conventional and alternative jet fuels

Jet engine operation parameters using conventional and alternative jet fuels, obtained by blending with plant oil bio-additives, during bench tests were evaluated. Jet fuels were tested and compared in conditions of engine operation. It was determined that using alternative jet fuels improves jet engine thrust characteristics and reduces fuel flow. These provide more energy efficient operation of jet engine. Using alternative jet fuels results in reduction of gas temperature in the jet pipe. This contributes to durability of materials and structure of the engine against high temperature, as well as reducing of NOx emissions. The results of the study show that operational parameters of the jet engine powered with new alternative jet fuels completely satisfy exploitation norms set in specification for tested engine. Alternative jet fuels, proposed in the study, may be used as a working body of the jet engine without a need of making changes in its design.

Evaluation of jet engine operation parameters using conventional and alternative jet fuels

Jet engine operation parameters using conventional and alternative jet fuels, obtained by blending with plant oil bio-additives, during bench tests were evaluated. Jet fuels were tested and compared in conditions of engine operation. It was determined that using alternative jet fuels improves jet engine thrust characteristics and reduces fuel flow. These provide more energy efficient operation of jet engine. Using alternative jet fuels results in reduction of gas temperature in the jet pipe. This contributes to durability of materials and structure of the engine against high temperature, as well as reducing of NOx emissions. The results of the study show that operational parameters of the jet engine powered with new alternative jet fuels completely satisfy exploitation norms set in specification for tested engine. Alternative jet fuels, proposed in the study, may be used as a working body of the jet engine without a need of making changes in its design.

The regimes of twin-fluid jet-in-crossflow at atmospheric and jet-engine operating conditions

The “Twin-Fluid Jet-in-Crossflow (TF-JICF)” is a nascent variation of the classical JICF, in which a liquid jet is co-injected with an annular sleeve of gas into a gaseous crossflow. Jet-engine designers are interested in using TF-JICF for liquid-fuel injection and atomization in the next-generation combustors because it is expected to minimize combustor-damaging auto-ignition and fuel-coking tendencies. However, experimental data of TF-JICF are sparse. Furthermore, a widely accepted TF-JICF model that correlates the spray’s penetration to the combined liquid-gas momentum-flux ratio (Jeff) is increasingly showing discrepancy with emerging results, suggesting a gap in the current understanding of TF-JICF. This paper describes an investigation that addressed the gap by experimentally characterizing the TF-JICF produced by a single injector across wide ranges of operating conditions (i.e., jet-A injectant, crossflow of air, crossflow Weber number = 175-1050, crossflow pressure Pcf = 1.8-9.5 atm, momentum-flux ratio J = 5-40, and air-nozzle dP = 0%-150% of Pcf). These covered the conditions previously used to develop the Jeff model, recently reported conditions that produced Jeff discrepancies, and high-pressure conditions found in jet-engines. Dye-based shadowgraph was used to acquire high-resolution (13.52 μm/pixel) images of the TF-JICF, which revealed wide-ranging characteristics such as the disrupted Rayleigh-Taylor jet instabilities, air-induced jet corrugations, spray-bifurcations, and prompt-atomization. Analyses of the data showed that contrary to the literature, the TF-JICF’s penetration is not monotonically related to Jeff. A new conceptual framework for TF-JICF is proposed, where the flow configuration is composed of four regimes, each having different penetration trends, spray structures, and underlying mechanisms.

Characterizing the Effects of Hot Isostatic Pressing on IN713C Superalloy Blade Microstructure by Electron Backscatter Diffraction

The integrity of turbine blades is essential for the safe operation of jet engines. Thus, the mechanical properties, especially creep resistance and fatigue strength at high temperatures, must be thoroughly optimized. In particular, it has previously been observed that the mechanical properties of blades depend on the microstructure and porosity resulting from the casting process. To decrease the internal porosity generated by investment casting, hot isostatic pressing can be applied. This paper aims to evaluate the effects of hot isostatic pressing on the microstructure of IN713C alloy blades. Two variants of hot isostatic pressing treatment, differing in pressure, were carried out, and each resulted in lowered porosity. Microstructural investigations, performed using scanning electron microscopy and electron backscatter diffraction revealed significant changes of γ′ particles and high strain intensity in the surface layer of the blades after hot isostatic pressing treatment.

Numerical simulation of ice accretion under mixed-phase conditions

Ice crystal ingestion at high altitude is a menace to the safe operation of jet engines. Because the core airflow in jet engine has higher temperature, ice crystals may partially melt into droplets when they enter the core airflow. A mixed-phase condition is seen consisting of both water droplets and ice crystals, which will cause ice accretion on both the static surfaces and rotating components in a compressor. This ice accretion may give rise to compressor surge or even mechanical damage of jet engine. In order to analyze this in depth, a numerical method of mixed-phase icing was developed. The Reynolds-averaged Navier–Stokes equations were used for the airflow solution. The Lagrangian method was employed for determining the trajectories of ice crystals and droplets. An ice crystal impingement model was created, in which the breakup and rebounding of ice crystals and splashing of film were considered. A thermodynamic model was proposed for ice crystals and droplets on the basis of the first law of thermodynamics. An icing simulation was developed under mixed-phase conditions with different liquid water contents and ice water contents, and the results were compared with experimental data from the literature. The comparison showed a fairly good correlation, which supports the validity and rationality of the method of mixed-phase icing.

Fusion characteristics of volcanic ash relevant to aviation hazards

The fusion dynamics of volcanic ash strongly impacts deposition in hot parts of jet engines. In this study, we investigate the sintering behavior of volcanic ash using natural ash of intermediate composition, erupted in 2012 at Santiaguito Volcano, Guatemala. A material science procedure was followed in which we monitored the geometrical evolution of cylindrical-shaped volcanic ash compact upon heating from 50 to 1400°C in a heating microscope. Combined morphological, mineralogical, and rheological analyses helped define the evolution of volcanic ash during fusion and sintering and constrain their sticking potential as well as their ability to flow at characteristic temperatures. For the ash investigated, 1240°C marks the onset of adhesion and flowability. The much higher fusibility of ash compared to that of typical test sands demonstrates for the need of a more extensive fusion characterization of volcanic ash in order to mitigate the risk posed on jet engine operation.

Thermostressed state in turbine rotor blades with thermal barrier coating at transient conditions of air breathing jet engine operation

The finite-difference method acceptable for on-board computers is applied to analyze the thermo-stressed state for the thermal-barrier coating of a perforated turbine blade and its wall at transient and stationary conditions of air-breathing jet engine operation during a flight.

Contribution to Quality of Air Traffic Due to Reduction of Gaseous Emissions

There are described basic principles of jet engine construction and operation in the presented paper, taking into consideration question of gaseous emissions produced in exhaust gases of turbojet engines. The innovative aircraft jet engines are the most important power units of modern planes nowadays and therefore it is necessary to analyse their environmental impacts, with regard to quality of living environment. This paper integrates technical and environmental factors of up-to-date jet engines. It demonstrates an important fact that modern airplanes equipped by sophisticated turbo-jet engines are environment friendly with regard to reduced amount of pollutants in their exhaust gases.

Distortion of Radio Reflections from Spacecraft Construction Elements by Plasma Jets and Structures: Physical Modeling

The methodology of physical modeling of scattering of electromagnetic waves by plasma jets and structures near a spacecraft's surface is developed. The effects of attenuation and distortion of radio signals reflected from spacecraft construction elements by plasma jets and artificial plasma structures, which arise during the operation of electric jet engines, injection of electron beams, and in the course of active and passive experiments in orbit, are experimentally investigated.

Non-self-sustained microwave discharge and the concept of a microwave air jet engine

A new type of microwave discharge—near-surface non-self-sustained discharge (NSND)—has been realized and investigated. A physical model of this discharge is presented.For the first time NSND application for microwave air jet engines has been proposed. Measurements under laboratory conditions modelling the microwave air jet engine operation shows the qualitative agreement between the model of NSND and actual processes near the target irradiated by a powerful microwave beam. Characteristic dependences of recoil momentum of target on the background pressure and microwave pulse duration obtained in experiments are presented. Measured cost of thrust produced by the NSND is no more than 3.0 kW N−1, which is close to the predicted values.

Theory of Disappearance of the Electric Signal Induced by an Aircraft Jet Engine in the Afterburner Regime

Electrical aspects of aircraft jet engine operation are considered. A phenomenon previously observed experimentally, namely, the disappearance of the engine current and alternating electric signal induced by the engine jet in the afterburner regime, is explained. It is shown that this phenomenon results from the “detachment” of electrons from negative ions when the gas temperature in the afterburner increases. This leads to an increase in the effective conductivity of the gas. As a result, the engine current circuit is closed on the internal duct walls and engine charging becomes insignificant.

Noise-suppressed exhaust nozzles for jet engines

An array of chutes (30) is permanently mounted within the flowpath of an exhaust nozzle (10,12) of an aircraft jet engine for entraining and mixing ambient air (74) with the exhaust gas (72) so as to reduce the noise level of aircraft, particularly during take-off. In order to provide good engine performance during all modes of jet engine operation, a convergent- (62) divergent (66) flap assembly is arranged downstream from the chutes (30) for controlling the nozzle throat and exit areas when the chutes are closed.

Sound attenuation system for jet aircraft engines

The present invention relates to a novel sound attenuating system. More particularly, the invention relates to a simpler, lighter, and more effective noise attenuating laminate which is made up of five specific layers of material. The laminate includes a duct liner, a moisture barrier, a fire barrier, acoustic attenuating material, and a solid backing sheet. The laminate is readily inserted into various sections of a jet engine compartment in order to attenuate the sound produced by the jet engine. Hollow rivets are used to conduct acoustical energy to the noise attenuating laminate. This novel means for conducting the acoustical energy to the laminate of the jet engine compartment allows for an improved anti-icing system, for more efficient jet engine operation, and for more efficient dissipation of acoustic energy.