Propagation of Gaussian Schell-Model Array Beams through a Jet Engine Exhaust

Here a Gaussian Shell Model Array (GSMA) beam is used to investigate the propagation characteristics in the jet engine exhaust region. It has great significance to improve various optical systems for wide application in trapping cold atoms, creating gratings, and atmospheric optical communication. We calculate analytical formulas for the spectral density (SD) and the propagation factors Mx2 and My2 of a GSMA beam. The influence of inner scale of turbulence in the jet engine exhaust region on its power spectrum has been also analyzed. According to these results, the influence of turbulence in a jet engine exhaust on a GSMA beam has been reduced by changing the parameters of light source and turbulence. For example, it is an excellent tool for mitigation of the jet engine exhaust-induced anisotropy of turbulence to increase the source coherence length, the root-mean-squared (rms) beam width, the wavelength or reduce the outer scale of turbulence.

Additive Design and Manufacturing of Jet Engine Parts

The additive design （AD） and additive manufacturing （AM） of jet engine parts will revolutionize the traditional aerospace industry. The unique characteristics of AM, such as gradient materials and micro-structures, have opened up a new direction in jet engine design and manufacturing. Engineers have been liberated from many constraints associated with traditional methodologies and technologies. One of the most significant features of the AM process is that it can ensure the consistency of parts because it starts from point（s）, continues to line（s） and layer（s）, and ends with the competed part. Collaboration between design and manufacturing is the key to success in fields including aerodynamics, thermodynamics, structural integration, heat transfer, material development, and machining. Engineers must change the way they design a part, as they shift from the traditional method of ＂subtracting material＂ to the new method of ＂adding material＂ in order to manufacture a part. AD is not the same as designing for AM, A new method and new tools are required to assist with this new way of designing and manufacturing. This paper discusses in detail what is required in AD and AM, and how current problems can be solved.

Off-Design Modelling of a Turbo Jet Engine with Operative Afterburner

Gas turbines are considered as one of the leading internal combustion engines in modern air transportation due to its favourable power to weight ratio and its continuous combustion process. Recent research focus has been concerned with performance improvements aimed at reduced fuel consumption and hence reduced impact on the environment. This study is aimed at using theoretical and computational methods to model the operation and performance a turbojet gas turbine engine. The commercial software GasTurb13 was used for the theoretical simulation while Microsoft Excel was used for the analytical study. GasTurb13 solved the model using pseudo-perfect gas models i.e. component maps since the specific gas ratio could not be inputted into the solver. The effect of changes in the Mach number and altitude on the engine performance was studied. Also the effect of changes in the compressor pressure ratio, the turbine inlet temperature and the afterburner exit temperature were also studied. Results obtained showed the optimum pressure ratio at maximum thrust constraint to be 16.78 for the turbojet engine operating at Mach number (Ma) = 0.8 and altitude = 10,000 m, Turbine inlet temperature (TIT) = 1200 K and Afterburner exit temperature = 1800 K.

NUMERICAL MODELING OF TURBULENTEVAPORATING GAS-DROPLET TWO-PHASE FLOWS IN AN AFTERBURNER DIFFUSOR OF TURBO-FAN JET ENGINES

The two-dimensional turbulent evaporating gas-droplet two-phase flows in an afterburner diffusor of turbo-fan jet engines are simulated by the k-ε turbulence model and the particle trajectory model. Comparison of predicted gas velocity and temperature distributions with experimental results for the cases without liquid spray shows pretty good agreement. Gas-droplet two-phase flow predictions give plausible droplet trajectories, fuel-vapor concentration distribution, gas-phase velocity and temperature field in presence of liquid droplets. One run of computation with this method is made for a particular afterburner. The results indicate that the location of the atomizers is not favorable to flame stabilization and combustion efficiency. The proposed numerical modeling can also be adopted for optimization design and performance evaluation of afterburner combustors of turbo-fan jet engines.

Li Ming Jet Engine Manaufacturing Corporation

The Shenyang Li Ming Jet Engine Manufacturing Corporation successfully carried out the trial production of a new type of turbofan engine blade for the SNECMA Corporation, based in France. When the blades were successfully produced, the French client placed an order for batch production with a contract to the year 2000.

NICKEL-BASED ALLOYS IN GE AIRCRAFT TURBINES: PAST, PRESENT & FUTURE

Improvements in materials have been critical to advances in the propulsion system. Over the past 50 years, many improvements have been made to nickel-based superalloys to satisfy design requirements; several key developments will be highlighted. Today, millions of pounds of superalloys are annually produced for use in turbine blades, vanes, disks, cases, and frames throughout the engine. Looking to the future, several themes emerge, although predicting the future is inherently risky.

HIGH TEMPERATURE COMPOSITES

The purpose of this paper is to review the current state of development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base.NiAl-base, and MoSi_2-base composites as replacements for today's Ni-base superalloys are discussed from the standpoint of key technical issues. current status, and future directions. Results describing progress in both improved understanding of the mechanisms of deformation and fracture, and improved material performance will be covered.

Medium independent jet(MI-Jet)engine

MI-Jet or medium independent jet engine is a new conceptual design which can be used in any gaseous atmosphere or in any planets with an ISP greafer than that of the existing rocket engines.MI engine's thermodynamic concept could be utilized to develop turbojet,ramjet and scramjet engines that can operate in Martian environment with higher ISP.The same concept could be extended for the development of MI-Turbojet,M-Ramjet and MI-Scramjet engine for Earth atmosphere with an ISP as high as 200% of the ISP of existing rocket engines,but less than that of the conventional scramjet or other air-breathing engine.However the operational complexity of the MI-Jet will be significantly lower than that of the existing scramjet engine.

EXPERIMENTAL STUDY ON THE EFFECTS OF AIR ENTRAINMENT ON A PLANE JET DIFFUSION IN A PLUNGE POOL

Laboratory experimental results about the effects of air entrainment on the jet diffusion in a plunge pool were presented. The results indicate that the air entrainment has little effect on the maximum mean impinging pressure generated by the jet at pool bottom. The maximum fluctuating pressure is increased with the increase of the air entrainment. Air entrainment also reduces jet spreading.

Numerical simulation of a hydrocarbon fuelled valveless pulsejet

Jet propulsion technology has been limited to being identified largely with turbojets and turbo-machinery driven jet engines.Of late there has been a renewed interest in pulsejet technology and it has once again caught the imagination of academia.The specific characteristics of the pulsejet,such as easy scalability,absence of moving parts,reduced combustion temperatures;lower NOX formation and the like make it possess varied capabilities for use in the field of jet propulsion and the most viable option for small-scale jet propulsion.In the current work,a numerical analysis encompassing feasibility and validation of a valveless pulsejet engine was attempted using CD-adapco's STAR-CCM+CFD package.Due to lack of comprehensive established mathematical laws to govern the working of a pulsejet,most experimental work being performed is done by trial and error.This necessitates in-depth computational studies in order to shed more light on the understanding of valveless pulsejets.The results have been encouraging and in agreement with observed experimental conclusions such as,i)changes in dimensions affect the working of a pulsejet,ii)presence of a flare enhances the working of a pulsejet,and the close agreement in the frequency of operation.Through continuous study,an optimum initial condition was achieved which enabled the pulsejet to begin operation even before 0.05 s,thereby greatly reducing computational costs if a higher time-scale were to be used.

A novel multi-fidelity coupled simulation method for flow systems

For the numerical simulation of flow systems with various complex components, the traditional one-dimensional （1D） network method has its comparative advantage in time consuming and the CFD method has its absolute advantage in the detailed flow capturing. The proper coupling of the advantages of different dimensional methods can strike balance well between time cost and accuracy and then significantly decrease the whole design cycle for the flow systems in modern machines. A novel multi-fidelity coupled simulation method with numerical zooming is developed for flow systems. This method focuses on the integration of one-, two-and three-dimensional codes for various components. Coupled iterative process for the different dimensional simulation cycles of sub-systems is performed until the concerned flow variables of the whole system achieve convergence. Numerical zooming is employed to update boundary data of components with different dimen-sionalities. Based on this method, a highly automatic, multi-discipline computing environment with integrated zooming is developed. The numerical results of Y-Junction and the air system of a jet engine are presented to verify the solution method. They indicate that this type of multi-fidelity simulationmethod can greatly improve the prediction capability for the flow systems.