Air-breathing Engines Research Articles

Study on Multi-objective Design Optimization Of Air Breathing Engine Fan for sounding rocket

Study on Multi-objective Design Optimization Of Air Breathing Engine Fan for sounding rocket

Experimental Investigation of Shape Transition Effects on Isolator Performance

AbstractIsolator is a critical component in supersonic air breathing engine and it is usually situated between the inlet and the combustor of a dual-mode ramjet/scramjet engine. In the present study, shape transition effects on isolator performance have been studied by carrying out experimental investigations on square, square to circular and square to elliptical transition ducts. The length of the isolator chosen in this study is 180 mm and the cross-sectional area of 900 mm2is maintained constant along the length for all the ducts. Experiments were carried out for isolator inlet Mach 2, using a contoured nozzle. Varying the pressure of the settling chamber varied the expansion level at the nozzle exit, which run the nozzle. The wall static pressure along the length of the isolator and the Pitot pressure at the exit plane of the isolator were measured for all the configurations. Shadowgraph technique was employed for visualizing the shock-train in the isolator. The square to circular transition isolator is found to be more efficient in achieving the static pressure rise across the isolator than the square and square to elliptical transition ducts.

Modelling a Hypersonic Single Expansion Ramp Nozzle of a Hypersonic Aircraft through Parametric Studies

This paper aims to contribute to developing a potential combined cycle air-breathing engine integrated into an aircraft design, capable of performing flight profiles on a commercial scale. This study specifically focuses on the single expansion ramp nozzle (SERN) and aircraft-engine integration with an emphasis on the combined cycle engine integration into the conceptual aircraft design. A parametric study using computational fluid dynamics (CFD) have been employed to analyze the sensitivity of the SERN’s performance parameters with changing geometry and operating conditions. The SERN adapted to the different operating conditions and was able to retain its performance throughout the altitude simulated. The expansion ramp shape, angle, exit area, and cowl shape influenced the thrust substantially. The internal nozzle expansion and expansion ramp had a significant effect on the lift and moment performance. An optimized SERN was assembled into a scramjet and was subject to various nozzle inflow conditions, to which combustion flow from twin strut injectors produced the best thrust performance. Side fence studies observed longer and diverging side fences to produce extra thrust compared to small and straight fences.

CFD Analysis of Supersonic flow performance around a scramjet engines

This paper talks about the optimal design outline and examination of a NASA X-43. The X-43 was an unmanned test hypersonic air vehicle with numerous arranged scale varieties intended to test different parts of hypersonic. Investigation is shown in relentless state 3D computational liquid components (CFD) at Mach 4.5 to Mach 9.0. In this method for examination, Lift, Drag, Lift Coefficient (Cl) and Drag Coefficient (Cd) are measured and taken a gander at isolated Mach numbers, Pressure structures and speed shapes are plotted and the Turbulence zone is foreseen from streamline sees examination were analysed in CFD. NASA and other groups are actively searching for ways to dramatically reduce the cost of lifting objects into earth orbit, currently estimated at approximately $20,000 per kilogram. One of the most promising prospects is the concept of an air breathing engine capable of propelling an aircraft in the hypersonic (Mach 5+) range. A supersonic combustion ramjet or scramjet, theoretically has the capability of reaching orbital velocities. The payload and economy benefits of such an engine become readily apparent when one considers the weight of a typical rocket-based space launch vehicle (like the Space Shuttle) is two thirds oxidizer.

A Way to Design an Adaptive Fuzzy Controller for the Dispenser Position of an Air-Breathing Engine

Fuel consumption control in a combustion chamber of an air-breathing engine is carried out by a metering device (dispenser). The metering needle of the dispenser is driven by a hydraulic cylinder. The hydraulic cylinder is controlled by a spool-valve amplifier of an electromechanical device. The idea of fuel consumption control in the combustion chamber is to position the metering needle with a given accuracy. An adaptive astatic fuzzy controller of the metering needle position is designed for controlling the dispenser. The controller consists of a fuzzificator, a unit for correcting the fuzzificator’s grade of membership, a defuzzificator, and an integrator. The fuzzificator consists of a set of linear terms (negative small, negative medium, normal, positive small, positive medium). The last ones are multiplied in addition to synapses tuned by an adapting unit with comparison element and built-in adder for correcting the fuzzificator’s grade of membership. The adaptation procedure is performed by step-by-step learning with the help of recurrent formula. The defuzzificator, consisting of a set of five unimodal membership functions, is used for transforming the fuzzy information into clear information. Defuzzification is performed by the centroid method. The loop for controlling the dispenser is an integral part of the loops for controlling parameters of the air-breathing engine.

Study of heat transfer with surface treatment in pre-coolers for aeroengine applications

The effect of surface roughness on convective heat transfer and pressure drop is assessed for a simplified pre-cooler system for application in high-speed airbreathing engines. The pre-cooler system comprises of four circular cylinders in cross-flow inside a square duct. The cylindrical wires of 1 mm diameter were textured using an economical method of surface treatment, via sand-blasting with 100 µm (diameter) particles. Experiments were conducted at Reynolds numbers ranging from 600 to 8000. The Nusselt number was observed to decrease for the rough wires, indicating decreased convective heat transfer rates. Moreover, roughness was found to have no appreciable effect on pressure drop for these conditions. This is attributed to a fully developed turbulent duct flow upstream of the wires, which was confirmed by observing the Nusselt-Reynolds number correlation for treated and untreated cases. Surface roughness strategy in pre-coolers for an ascent trajectory of a high-speed airbreathing engine is also discussed.

Diffusion Model of Combustion of Large Boron Particles

Owing to its high mass and volume heats of combustion, boron is a promising component of solid propellants for air-breathing engines. Its application is limited by difficulties of organizing high-efficiency combustion. Experimental investigations of combustion of individual boron particles demonstrate a large number of unique features, which are not typical for other materials: variable ignition temperature, two stages of combustion, and drastic reduction of the burning rate for particles with sizes of several micrometers or smaller. Models that cover the entire range of temperatures, concentrations, and particle sizes are physically non-obvious, can be hardly reproduced, and do not provide the accuracy needed for solving practical problems. In this paper, we propose a simple diffusion model of combustion, which ensures an adequate description of combustion of boron particles 34.5 and 44.2 μm in size at temperatures above 2240 K.

In Tune with Times: Recent Developments in Theoretical, Experimental and Numerical techniques of Aircraft Engines

Today the aircraft engine designing and development work is increasing drastically. Especially aircraft engines play a vital role in order to decide the aircrafts speed and its performance. Broadly turbojet, turboprop, turbo shaft and turbofan engines comes under the category of air breathing engines. Every engine has its own purpose and application. But modern aircrafts require much more advancements. Designing a new aircraft engine has been a really challenging task to the researchers. But giving a complete holistic view of aircraft engines and research gap would definitely help a lot to the new designers. Once identified the drawbacks of engine performance can be corrected in the future. For any new design of aircraft engine researchers are suggested to take Theoretical, Experimental and Numerical approaches. Therefore present paper makes an effort to review complete recent Theoretical, Experimental and Numerical approaches which are followed till date. Under all the three approaches all the air breathing engines have been clearly explained and solicited. The effort is to identify the gaps between different approaches which are hampering the process of engine development. The paper also gives the research gaps that need to be incorporated for effective performance enhancement of the aircraft engines for aeromechanical features.

第23回エアーブリージングエンジン国際会議（ISABE2017）報告

第23回エアーブリージングエンジン国際会議（ISABE2017）報告

Flow blockage in a transonic axial flow compressor: simulation analysis under distorted conditions

Today the aircraft industry is looking for faster and safer engines for both civil and military applications. The performance of all different types of air breathing engines depends on the amount of mass flow rate of air entering and hot gas ejecting out from the engine. Thrust is the key role for any engine performance. To achieve more thrust all the turbo machinery components like axial fan, axial flow compressor and axial flow turbine should function effectively. This paper is primarily dealing about one of the turbo machinery component, axial flow compressor performance where the study is more focused on flow blockage formation under distorted phenomena. The complete blade boundary layer formation and related flow numerical theory are discussed in detail, accordingly the boundary conditions were set to have better numerical simulations using ANSYS tool. To find the flow blockage formation suitable turbulence model was coded using the well know compressible equations. The flow blockage between the rotor and stator of the compressor stage was calculated and also validated with that of experimental data effectively. The flow simulation results also revealed that the performance parameters under the modern engine transonic speed from Mach 0.8 to 1.2 under the distorted conditions are better for aeromechanical features.

(Invited) Developing Environmental Barrier Coatings Resistant to Molten Calcium-Magnesium-Aluminosilicate (CMAS)

In order to improve fuel efficiency in commercial aircraft engines, ceramic matrix composites (CMC) are considered a leading material system to replace metal-based turbine engine components, due to their lower density and high-temperature capabilities compared with traditional metallic structural materials. However, silicon-based CMCs are susceptible to oxidation and corrosion in the harsh combustion environment found in air-breathing turbine engines. Environmental barrier coatings (EBCs) are being developed and applied to protect and to enhance durability and service life of CMC components for application in the hot-section of engines. The development of robust EBCs is threatened by sand, volcanic ash and other particulate debris, which are routinely ingested by aircraft engines in varying geographic regions. At temperatures >1200°C, these particulates melt, yielding molten calcium-magnesium-aluminosilicate (CMAS) deposits. These deposits can significantly reduce the durability of present and future engine component materials, particularly EBCs designed to protect silicon-based ceramic matrix composites (CMC). Near target operating temperatures (~1500°C) of future CMC-based aircraft engines, molten CMAS behaves like a viscous melt that can infiltrate and chemically interact with protective coatings, causing premature failure of the EBC system and ultimately the overall CMC engine component. Degradation of candidate EBC materials based on rare-earth silicates by molten CMAS will be presented with a focus on recent work, as well as methods of evaluating the complex high-temperature materials interactions, accomplished at NASA Glenn Research Center.

Numerical analysis and design optimization of supersonic after-burning with strut fuel injectors for scramjet engines

Scramjets are a class of hypersonic airbreathing engine that offer promise for economical, reliable and high-speed access-to-space and atmospheric transport. The expanding flow in the scramjet nozzle comprises of unburned hydrogen. An after-burning scheme can be used to effectively utilize the remaining hydrogen by supplying additional oxygen into the nozzle, aiming to augment the thrust. This paper presents the results of a single-objective design optimization for a strut fuel injection scheme considering four design variables with the objective of maximizing thrust augmentation. Thrust is found to be augmented significantly owing to a combination of contributions from aerodynamic and combustion effects. Further understanding and physical insights have been gained by performing variance-based global sensitivity analysis, scrutinizing the nozzle flowfields, analyzing the distributions and contributions of the forces acting on the nozzle wall, and examining the combustion efficiency.

Experimental investigation on enhanced thermal performance of staggered tube bundles wrapped with metallic foam

Tube bundles wrapped with metallic foam can be used in air-breathing engine as the compact heat exchanger due to its low density and high specific surface area. The enhanced thermal performance of metallic foam is crucial to design of staggered tube bundles with metallic foam fins. Previous studies have shown the effects of foam-structure on entire metallic foam, and discussed the influence of tube-bundle structure on the tube bundles qualitatively. However, the thermal and flow mechanisms on coupling of metallic foam and pure fluid which could expound enhanced heat transfer process of metallic foam fins are not yet fully explored. To address this, an experimental study was conducted to investigate the effects of structure parameters of metallic foam on thermal and flow characteristics in 2 mm outer-diameter staggered tube bundles wrapped with 2 mm thickness of metallic foam. This article reveals variation trend of heat transfer rate with change of key parameters: porosity and pore density. The results indicate that: 1, with increase of porosity, Nusselt number increases because of stronger penetrating ability, and heat convection dominates the heat transfer. 2, for variation of pore density, Nusselt number of high PPI samples is lower for thermal-insulation effect at low Reynold number. However, Nusselt number of high PPI samples is higher for greater amount of penetrating air at high Reynold number. 3, a new friction factor correlation of tube bundles is proposed to describe the pressure drop by dimensionless tube pitches, Reynolds number and Darcy number with maximum ±20% deviation. 4, a new Nusselt number correlation of tube bundles is given to reflect the heat transfer mechanism by Darcy number.

Demonstration of Ethanol-Blended Hydrogen Peroxide Gas Generator for Ramjet Combustor Flow Simulation

A gas generator using the catalytic decomposition of ethanol-blended hydrogen peroxide was investigated for application in experimental research on high-speed airbreathing engines. The gas generator should supply product gas with an oxygen concentration of 21 mol % at a given pressure of 3–12 bar and a temperature near 500°C, which are the flow conditions in a ramjet combustor flying at Mach 3. To avoid detonation of the liquid monopropellant, an appropriate mixture ratio of hydrogen peroxide, water, and ethanol was selected. In the batch reactor test, the tested catalysts were manganese oxide and platinum with gamma-alumina pellets. The temperature measurements indicated that the platinum with alumina pellets was more appropriate for decomposing propellant than manganese oxide with alumina pellets. In addition, product gas species with an oxygen concentration of 21 mol % were confirmed through the test. In the demonstration test, the system was operated with a propellant mass flow rate near 100 g/s. A catalytic reaction was sustained for the whole operation time with an adiabatic decomposition temperature efficiency of over 0.98. The measured flow temperature was near 500°C and the chamber pressure was near 5.5 bar, which satisfied the flow conditions in a ramjet combustor flying at Mach 3.

Gas-dynamic problems in off-design operation of supersonic inlets (review)

Modern concepts of operation of supersonic inlets of high-velocity air-breathing engines are analyzed. It is demonstrated that the flow in the engine duct becomes extremely complicated in off-design modes of inlet operation, which can lead to unpredictable consequences, in particular, to inlet unstart. The term “inlet unstart” is considered in the present paper as a synonym of the absence of theoretical understanding and prediction of gas-dynamic phenomena. Various approaches are proposed to ensure self-regulation of the inlet-combustor system for air-breathing engines. Possible directions of further research are indicated for the purpose of stable operation of inlets in a wide range of flight conditions.

Development of a Premixed Combustion Capability for Dual-Mode Scramjet Experiments

Hypersonic airbreathing engines rely on scramjet combustion processes, which involve high-speed, compressible, and highly turbulent reacting flows. The combustion environment and the turbulent flames at the heart of these engines are difficult to simulate and study in the laboratory under well-controlled conditions. Typically, wind-tunnel testing is performed that more closely approximates engine development rather than a careful investigation of the underlying physics that drives the combustion process. The experiments described in this paper, along with companion datasets, aim to isolate the chemical kinetic effects and turbulence–chemistry interaction from the fuel–air mixing process in a dual-mode scramjet combustion environment. A unique fuel-injection approach is adopted that produces a uniform fuel–air mixture at the entrance to the combustor and results in premixed combustion. This approach relies on the mixing enhancement of a precombustion shock train upstream of the dual-mode scramjet’s combustor. For the first time, a stable flame, anchored on a cavity flameholder, is reported for a scramjet combustor operating in premixed fuel–air mode. The new experimental capability has enabled numerous companion studies involving advanced diagnostics such as coherent anti-Stokes Raman scattering, particle image velocimetry, and planar laser-induced fluorescence.

Diagnostics of rocket and jet engines through characteristics of the intrinsic electromagnetic field of combustion products

This paper presents the feasibility of using electrophysical methods to diagnose and tune the propulsion systems of rocket and space technology items by analyzing published experimental and theoretical results on the electrophysical characteristics of combustion processes and combustor discharge of liquid- and solid-propellant rocket and air-breathing jet engines. Data on the development of emergency protection systems for propulsion engines, based on monitoring the electrophysical characteristics of the propellant, are presented.

Numerical and experimental study of fuel pre-injection in the inlet of a high-velocity air-breathing engine

The effect of preliminary injection (pre-injection) of a gas (heated air, methane, or ethylene) ahead of the entrance of a three-dimensional inlet in a supersonic flow with Mach numbers M∞ = 2–4, stagnation temperature T * = 300 K, and flow rates of the injected gas corresponding to 0–6% of the flow rate of air through the inlet is numerically studied. The gas is injected through orifices located behind the base surfaces of pylons mounted upstream of the inlet entrance. The computations are performed by the ESI-FASTRAN software package, which allows one to calculate three-dimensional viscous turbulent gas flows by a time-dependent method with the use of the Reynolds-averaged Navier–Stokes equations. Experimental investigations of pre-injection are performed with the use of small-scale and large-scale inlet models at M∞ = 3–4 and 6. A positive effect of pre-injection on stable (without stalling) deceleration of the incident flow in the case of mass supply and on initiation of ignition and stable combustion in the combustion chamber is confirmed.

Instantaneous monitoring of local fuel concentration in a liquid hydrocarbon-fueled flame using a LIBS plug

A portable device composed of photodiodes and bandpass filters was developed to measure local fuel concentration in a liquid hydrocarbon-fueled spray flame. The plasma emission spectra in and around the flame were selectively captured using such simplified device or plug instead of using a laboratory standard laser-induced breakdown spectroscopy (LIBS) system consisting of an ICCD and a spectrometer. The hydrogen (656 nm) and oxygen (777 nm) atomic lines were selected to determine the fuel concentration in atmospheric pressure. The H/O signal intensity ratio was found to be a strong function of the fuel concentration, and thus a calibration curve for the concentration measurements was established and validated using conventional LIBS. The proposed scheme to measure the local equivalence ratio of spray flames using a bundled layout of multiple LIBS plugs alongside the combustor wall may offer simple and highly robust diagnostics, especially under the harsh combustion conditions within air-breathing engines.

Key parameters effects and design on performances of hydrogen/helium heat exchanger for SABRE

Hydrogen/helium heat exchanger is a kind of heat exchanger dedicated to SABRE (Synergetic Air-breathing and Rocket Engine). Its special working environment and operating condition have brought a great challenge to its design. Hydrogen/helium heat exchanger with micro-channel/plate heat exchanger as its configuration is taken as the research object in this paper. Mathematical model of the heat exchanger is set up based on logarithmic mean temperature difference method, and the parameters that affect the heat transfer performance of heat exchanger is analyzed. The results showed that, reducing the thickness of fin or plate can help reduce the pressure loss of working fluids, the length and weight of hydrogen/helium heat exchanger. Reducing the width of micro-channel can reduce the length of heat exchanger and increase the height of heat exchanger. Reducing the height of micro-channel can reduce the length and height of heat exchanger. As a whole, the pressure loss of working fluids shows a trend of decreasing at first and then rising with the height or width of micro-channel rising. The pressure loss of helium is much greater than that of hydrogen, which means the pressure loss of helium is more sensitive to geometric parameters of heat exchanger and should be well controlled. In order to gain the best performance of the heat exchanger, the geometric parameters of heat exchanger is designed by Artificial Fish Swarm Algorithm.