Engine Nozzle Research Articles

Emissions of Volatile Particulate Components from Turboshaft Engines Operated with JP-8 and Fischer-Tropsch Fuels

Particulate emissions from two types of helicopter turboshaft engines operated with military JP-8 and paraffinic Fischer-Tropsch (FT) fuels were characterized as an objective of the field campaign held at the Hunter Army Airfield in Savannah, GA in June 2007. In general helicopter engines exhaust particles size distributions observed at the engine nozzle and 4.14 m downstream locations showing the geometric mean diameters smaller than 50 nm for all engine power settings investigated in this study. For both locations, the geometric mean diameter increased as the engine power setting increased; this trend also holds true for the emitted particle number concentration. The growth of particle geometric mean diameter was found significant, 7 nm, only in the case of the idle power setting. Sulfur-to-sulfate conversion was found to be independent of the engine power setting. Emissions of both sulfur and sulfate increased as the engine power increased. When JP-8 fuel was used, particles smaller than 7 nm were found to increase in samples taken at the downstream location. The number concentration in this tail increased as the power setting increased. No such observation was found when FT fuel was used implying that the increased formation of nuclei particles in the plume downstream was likely to be caused by the sulfur and aromatic compounds in the JP-8 fuel. Total particulate carbon emissions increased as the engine power setting increased. Use of FT fuel reduced the elemental carbon emissions as it compared to the JP-8 fuel, and organic carbon emission at idle power but not at the higher powers. The reduction of elemental carbon by the FT fuel was attributed to the absence of aromatics (soot precursors) in the fuel. The OC/EC ratio was found to be in the range of 3-50 depending on the engine power setting. The aircraft emitted OC/EC was found to decrease as the engine power increased.

High-Aspect-Ratio Microdrilling of Cobalt-Based Superalloy

It is necessary to develop a high-aspect-ratio microdrill method with a diameter of 0.2mm and a depth of 4mm (aspect ratio 20) that can be applied to the fuel injection nozzle of a marine diesel engine. However, the injection nozzle is made of cobalt-based superalloy, which is a difficult-to-cut material. In this study, the drilling conditions from viewpoints of thrust force and torque for the cobalt-based superalloy are determined. In addition, a thinning machine is developed for the convenient precise thinning of the microdrill. The effects of the thinning of the microdrill are verified to measure thrust force and torque during drilling. The following results are obtained. The thinning of the microdrill with a diameter of 0.2mm results in a reduction in thrust force by 20% and that in chip adherence to the drill by 25% during drilling.

LNGロケットエンジンにおけるサルファアタック及びコーキングに関する基礎研究

Liquified Natural Gas (LNG) is one of the most promising propellant for near future space transportation rocket engine because of its low cost and fewer handling concerns. However, for LNG propellant, erosion of engine material by sulfur (sulfur attack) and coking by LNG pyrolysis are significant problems in a regenerative cooling passage. In this study, the effects of sulfur attack and coking are experimentally evaluated for material candidates such as Inconel600, SUS316, Hastelloy-X, and some copper alloys. In the sulfur attack tests, EPMA and Raman analysis indicate that metallic sulfide can be observed only on the surface and XRD analysis indicates that sulfur attack are hardly recognized for all of material in the test conditions. In coking tests, it is clear that coking of methane with 5% propane can proceed more than those of pure methane. The thermal decomposition temperature is significantly decreased by catalytic effects of Ni in engine material. The results of coking tests will be included in the design criteria of combustion chamber, nozzle of the LNG rocket engines.

Shock structure in separated nozzle flows

In the case of high overexpansion, the exhaust jet of the supersonic nozzle of rocket engines separates from nozzle wall because of the large adverse pressure gradient. Correspondingly, to match the pressure of the separated flow region, an oblique shock is generated which evolves through the supersonic jet starting approximately at the separation point. This shock reflects on the nozzle axis with a Mach reflection. Thus, a peculiar Mach reflection takes place whose features depend on the upstream flow conditions, which are usually not uniform. The expected features of Mach reflection may become much difficult to predict, depending on the nozzle shape and the position of the separation point along the divergent section of the nozzle.

Methodology of studying the parameters of contaminant emissions from the orientation engines of orbital stations during and after the flight

The methodology of space experiments aimed at studying the dynamics of the emission of contaminants from the nozzles of the orientation engines of orbital stations is described. It was demonstrated that the use of passive diagnostic means, such as plates with special coatings and porous absorbents exposed for a long time near the engines, makes it possible to determine the quantitative characteristics and spatial distribution of incomplete combustion products.

A concept of a spacecraft with small initial mass placed in the near-earth orbit by a laser rocket engine

A method and results of calculating the laser radiation power values necessary to place an artificial earth satellite in orbit are presented; the values depend on the initial vehicle mass, velocity of the working fluid efflux from the laser rocket engine nozzle, velocity of vehicle motion, optimal values of thrust-to-weight ratio taking into account irreversible energy losses in the rocket engine jet. The possibility of creating a spacecraft with small initial mass is substantiated. A layout scheme of the propulsive system is proposed that makes it possible to divide total laser radiation power and to use atmospheric air as a working fluid.

Effects of chemical and physical models on a one-dimensional flow in a rocket nozzle

a one-dimensional mathematical and numerical model for the flow in a LOX/LH2-rocket engine nozzle is presented. Temperature is used as unknown at energy equation and velocity is obtained for all speeds regimes. For all analyses, tiny tolerances and a large number of iterations were used, in order to achieve the round-off error and estimate the discretization error. For each physical model, different chemical schemes are compared (among them and to reference ones, with good accuracy), indicating the influence of the choice of such schemes on numerical results. Six-species models and 80 control volumes are recommended, at least, for preliminary tests. 1 Nomenclature

Axisymmetric thermoviscoelastoplastic state of thin laminated shells made of a damageable material

A technique for the determination of the axisymmetric thermoviscoelastoplastic state of laminated thin shells made of a damageable material is developed. The technique is based on the kinematic equations of the theory of thin shells that account for transverse shear strains. The thermoviscoplastic equations, which describe the deformation of a shell element along paths of small curvature, are used as the constitutive equations. The equivalent stress that appears in the kinetic equations of damage and creep is determined from a failure criterion that accounts for the stress mode. The thermoviscoplastic deformation of a two-layer shell that models an element of a rocket engine nozzle is considered as an example

Pit clustering in cavitation erosion

An investigation of the erosion effects of cavitation on a thin aluminium foil was made. Cavitation was generated in a small tank with capacity of about 500 ml of clean water. The growth and collapse of bubbles was triggered by means of ultrasound. The sustained damage was measured by evaluating the area of the damaged surface in time intervals of 4 s. Also the length of the boundary between the damaged and the undamaged surface and the characteristic pit/hole size were measured. The goal of the study was to investigate the phenomenon of pit clustering within the incubation period and the influence of the already eroded surface on appearance of new pits. Additionally, the possibility of self-amplification of the erosion due to the presence of small deformations (pits) was studied. The results evidently show that pits tend to appear in clusters and near already damaged surface and this can be explained by the fact that the already present deformations on otherwise polished alloy surface act as the “cavitation generators” and cause more bubbles to appear and collapse in that region. Determining the physics of these phenomena is of great importance for engineering applications (preventing erosion in water turbines, pumps, diesel engine nozzles, etc.), also because most studies, that deal with predicting the actual mass loss, investigate the erosion in the incubation period and then extrapolate the results to the time scale of a real machine operation (B. Bachert, G. Ludwig, B. Stoffel, S. Baumgarten, Comparison of different methods for the evaluation of cavitation damaged surfaces, ASME Fluid Engineering Division Summer Meeting and Exhibition, Houston, 2005; J.P. Franc, J.M. Michel, Fundamentals of Cavitation, Kluwer Academic Publishers, 2004).

액체로켓 연소기 노즐의 벌징 공정

A study has been conducted on the bulging process of liquid rocket engine nozzle which is essential to the manufacturing regenerative cooling combustion chamber. Mechanical properties of the material used for the bulging were experimentally obtained by tension tests. Deformation of the bulged nozzle was confirmed by a structural analysis. The developed bulging process and the deformation analysis result were confirmed by manufacturing of the bulged nozzle specimens and the bulging test. There has been a bulging failure among 7 bulged specimens due to the necking of the material. The cause of necking was investigated by comparing microstructure of the material. The investigation has revealed grain size of the material has considerable effect on the occurrence of the neckingﾖ⨀ጊ缀Ѐ㘰〻Ԁ䭃䑎䷙3㠵㬅K䍄乍쐗ጊ谀Ѐ㌸㠻Ԁ䭃䑎䶯᜜፭

Postcombustion Evolution of Soot Properties in an Aircraft Engine

Recent measurements have suggested that soot properties can evolve downstream of the combustor, changing the characteristics of aviation particulate matter emissions and possibly altering the subsequent atmospheric impacts. This paper addresses the potential for the postcombustion thermodynamic environment to influence aircraft nonvolatile particulate matter emissions. Microphysical processes and interactions with gas phase species have been modeled for temperatures and pressures representative of in-service engines. Time-scale arguments are used to evaluate the relative contributions that various phenomena may make to the evolution of soot, including coagulation growth, ion-soot attachment, and vapor condensation. Then a higher-fidelity microphysics kinetic is employed to estimate the extent to which soot properties evolve as a result of these processes. Results suggest that limited opportunities exist for the modification of the size distribution of the soot, its charge distribution, or its volatile content, leading to the conclusion that the characteristics of the turbine and nozzle of an aircraft engine have little or no influence on aircraft nonvolatile emissions. Combustor processing determines the properties of soot particulate matter emissions from aircraft engines, setting the stage for interactions with gaseous emissions and development as cloud condensation nuclei in the exhaust plume.

HIP Powder Metal Near-Net Shapes for Demanding Environment and Applications

Abstract Sandvik Powdermet AB in Surahammar, Sweden has been the leading supplier of near net shape powder metal (PM) hot isostatically pressed (HIP) components since 1985. All together several thousands of tonnes of fittings, valve components, manifolds, swivel parts, diesel engine nozzles, turbine parts, centrifugal separators and components for medical purposes have been successfully produced. This paper will review a number of applications of interest for demanding industries as the Oil and Gas and other energy related communities. The production and engineering facilities in Sweden and the US involve inert gas atomisation of powder, 3D CAD capsule design, sheet metal capsule fabrication and large HIP systems capable of producing individual parts as large as about 14 tonnes followed by heat treatment, pickling, machining and final inspection. The major applications are for the Oil and Gas Industry especially in offshore and sub sea applications. Other applications are for the Industrial Power Generation, the Pulp and Paper, the Pharmaceutical and Traditional Engineering Industries. Typically the components replace castings, forgings and fabricated parts and are produced in grades such as Martensitic steels, Austenitic and Duplex (Ferritic/Austenitic) stainless steels and Ni - base super alloys. The need for machining of the components is reduced to a minimum and welding during final assembly is reduced substantially compared to conventional practice. A HIP PM valve body design offers better performance, improved service life as well as delivery time and cost advantages versus conventional manufacturing methods. Typically, Manifolds made by the HIP PM route reduce the necessary welding by 70—80 %. The driving force in the substitution from conventional forging and fabrication to HIP PM components rely on reduced manufacturing lead-time, design flexibility, improved quality and isotropic properties and an advantageous cost for the final component. The HIP PM near net shape route has received approval from ASTM, API, NORSOK and NACE. This paper will review the manufacturing sequence for PM near net shapes and will discuss details of several manifold components.

The effect of aberrations on the focusing of laser radiation in a composite optical concentrator

This paper discusses an original structure of an optical laser-beam concentrator for the formation of laser thrust. The concentrator consists of optical elements of conical shape and makes it possible to introduce radiation into the nozzle of a laser engine through a slit in the wall of the nozzle. Results are presented of a theoretical and experimental study of how the phase distortions of the laser beam and the optical aberrations of the concentrator affect the radiation-focusing conditions in the nozzle of the laser engine.

Spectroscopic detection of aircraft wake gases

Using the technique of limiting information-metric scales, the potential of laser IR absorption spectroscopy for detecting small gas components of aircraft wake was quantitatively analyzed. Formulas for minimum distinguishable and minimum detectable gas concentrations were derived. Calculation was carried out for SO2, NO, and NO2 under typical conditions near the Boeing 707 aircraft engine nozzle at altitude H = 12.2 km. Alternative IR laser spectroscopy methods for detecting various gas components in the near wake were considered. Two possibilities to improve the concentration measurement sensitivity were analyzed: (i) a decrease in the background absorption of CO2 and H2O and (ii) an increase in the absorption cross section of detected gas.

4105 衝撃風洞を用いたラバルノズルスロート部における伝熱特性に関する研究(G19 宇宙工学に関する基盤研究,G19 宇宙工学)

The adequate cooling of nozzles of rocket engines requires design information for predicting a local heat flux. The heat flux has highest value at a nozzle throat area. The purpose of this study is to reveal experimental heat transfer data in the nozzle throat by using a shock tunnel. The shock tunnel was built with a shock tube and instrumented nozzle at the end of the shock tube. In the case of shock tunnel, duration time of supersonic flow is so short that high response instrumentation or methods are necessary for measuring the transient heat flux and temperature. We applied platinum thin film heat flux gauge. Open literatures suggest several experimental equations that may be applicable for predicting the heat transfer coefficients in the nozzle. Bartz's equation is one of them and is a well-known equation. This paper will present comparison between experimental measurement data by using the developed gauges and estimation by Bartz's equation.

Experimental and Theoretical Investigation of Base-Flow Buffeting on Ariane5 Launch Vehicles

A summary of some of the theoretical and experimental investigations of transonic base-flow buffeting on Ariane5 is described in this paper. The source and the mechanism of buffeting in the base flow, including its instability coupling with the local acoustic resonance, are identified and explained. A model for the ArianeS base-flow buffeting is presented. Detailed comparisons between available experimental data and semiempirical predictions on the ArianeS side-load resonant frequencies and amplitudes are highlighted. The main objective is to design a configuration for the ArianeS base to have the base-flow buffeting on the Vulcain engine nozzle at least reduced, if not avoided.

LE-7Aエンジンノズル内段差による剥離の停滞とジャンプの現象

At an early stage of development, LE-7A engine suffered from high side loads. One of them was caused by the transition between Free Shock Separation (FSS) and Restricted Shock Separation (RSS), and the other was caused by the stagnation and sudden movement (‘jump’) of the separation point at a small step inside the nozzle extension. This paper focuses on this stagnation and jump phenomenon of separation point caused by the step inside LE-7A engine nozzle during the startup and shutdown transients.

Optimization of the design of recuperative heat exchangers in the exhaust nozzle of an aero engine

Today the needs for safer, cleaner and more affordable civil aero engines are found to be of great importance. Five years ago, the EU initiated an action for the design and the construction of efficient and environmentally friendly aero engines (EEFAE). One of the major European gas turbine industries, MTU, has presented a new technology for an advanced aero engine design, which uses an alternative thermodynamic cycle. The basis of this cycle is the adoption of a recuperation part with the use of a system of heat exchangers, installed in the exhaust nozzle of the aircraft engine. Thermal energy in the turbine exhaust is used in the recuperator to pre-heat the compressor outlet air before combustion. The benefits of this technique are focused on reduced pollutants and decreased fuel consumption. In this work, the procedure of the optimization of this installation, by means of the imposed pressure drop downstream the aircraft engine and the balanced mass inflow to the heat exchangers is presented. The optimization is based on experimental measurements in laboratory conditions and preliminary 2D CFD modeling for the flow inside the exhaust duct and through the heat exchangers. It is shown that with a careful approach, a better arrangement of the heat exchangers can be achieved in order to have a minimum pressure drop in the exhaust nozzle which can positively affect the engine’s performance.

A STUDY ON THE THERMAL VIBRATION ANALYSIS OF THE GRAPHITE DISK UNDER THERMAL SHOCK

Graphite is applied to structural material of the high temperature reactor and nozzle of high energy rocket engine. The excessive vibration and stress field can be occurred for this material due to the severe thermal condition. In this study, the thermal stress and vibration characteristics of ATJ graphite under high temperature condition are investigated by finite element analysis (FEA). The specimen is designed as a disk shape in order to simulate the rocket nozzle combustion condition. The experiment of thermal heat is also conducted using by CO 2 laser.

Performance prediction and optimization for liquid rocket engine nozzle

An optimization approach, based on computational fluid dynamics methodology, is investigated for the performance prediction and optimization of liquid rocket engine nozzle. The CFD code employs implicit Lower-Upper decomposition (LU) scheme for solving the two-dimensional axisymmetric Navier–Stokes (NS) equations and species transport equations in an efficient manner. The validity of the code is demonstrated by comparing the numerical calculations with both the experimental data and previous calculations. Then the code, called by three optimization algorithms (i.e. successive quadratic programming method, genetic algorithm and interdigitation strategy) respectively, is used to design axisymmetric optimum-thrust nozzle. Results show that improvement on nozzle thrust can be obtained over that of the baseline case.