CN104989549A - Method for raising air inflow yield of ramjet through laser energy injection - Google Patents

Abstract

The invention provides a method for raising the air inflow yield of a ramjet through the technology that laser energy can deposit and puncture a flow field to form quasi-state waves. The method comprises pre-estimating the position of front oblique shock waves of a ramjet, shaping a laser beam into a laser sheet, shaping quasi-state waves, and raising the air inflow yield. The method comprises S1, solving a NS equation to numerically simulating a flow field, or carrying out a wind tunnel test according to the Mach and Reynolds similar criterion to determine whether the air inflow yield of an air intake duct of the ramjet reaches up to the designed value and the position of a front oblique shock waves, S2, shaping a laser beam into a laser sheet through combination of a plurality of reflectors and lenses, S3, optimizing the value, position and frequency of laser energy to form quasi-state waves, and S4, changing the flowing direction of an upstream the lip of the air intake duct under the function of interaction of the quasi-state waves and the front oblique shock waves, to deflect and compress a coming flow which originally can be spill out into an internal compression segment of the air intake duct.

Description

Laser energy injects and improves pressed engine air inlet quantity of the catch method

Technical field

The invention belongs to Flowing Main-Control control field, is a kind of device for improving supersonic and hypersonic aircraft pressed engine air inlet quantity of the catch.

Background technique

Ultrasound velocity or hypersonic punching type intake duct rely on precursor oblique shock wave to catch and compressed air stream, and its desirable geometric configuration is shock wave sealing, and namely precursor compression oblique shock wave collects on lip, and reflected wave is incident in intake duct shoulder.Angle of Shock Waves is determined by Mach number, and therefore when flight Mach number is lower than design Mach number, spilling will occur, and air quantity of the catch reduces.For avoiding the engine performance caused thus to reduce, can adopt and become geometry intake duct, but changing the mechanical system more complicated of geometric configuration.Another feasible method is exactly inject or extracting energy, i.e. active Flow Control technology in flow field.

People (the M.N.Shneider such as the M.N.Shneider of Princeton university, S.O.Macheret, S.H.Zaidi, et al.Steady and Unsteady Supersonic Flow Control with EnergyAddition [R] .34th AIAA Plasmadynamics and Lasers Conference, Orlando, Florida.AIAA 2003-3862.Shneider M N, Macheret S O, et al.Modeling ofPlasma Virtual Shape Control of Ram/Scramjet Inlet and Isolator [R] .PortlandOregon.Plasma dynamics and Lasers Conference in Portland, the imagination of " virtual lip " Oregon.AIAA2004-2940.) is proposed, microwave is injected at flow field special position, the directional energy such as laser or electron beam, form heating region, utilize the raising of this regional temperature or pressure that incoming flow is deflected, make the increase entering inlet flow quality.They have carried out comparatively detailed numerically modeling to " virtual lip ", and result shows that the method fully can improve air inlet and catch quality and kinetic energy efficiency.The people such as R.B.Miles (Sergey O.Macheret, Mikhail N.Shneider, Richard B.Miles.Optimum Performance of Electron Beam Driven MHD Generators for ScramjetInlet Control [R] .34th AIAA Plasadynamics and Lasers Conference, Orlando, Florida.AIAA 2003-3763.Macheret S O, Shneider M N, Miles R B, et al.Scramjet Inlet Control by Off-Body Energy Addition and MHD Deceleration [R] .Moscow.5th Int.Workshop on Magneto-Plasma Aerodynamics for AerospaceApplications, magnetohydrodynamics (i.e. MHD) flow control method 2003-32.) is utilized to improve air inlet performance, the volumetric force that its principle is subject to when being and utilizing charged air to move in magnetic field, control incident shock position, extend the operation Mach number of intake duct.

The employee's card of the energy injection control pressed engine air inlet quantity of the catch carried out both at home and abroad understands the feasibility of the method, but at present for the mode that laser energy injects, not yet proposes the laser energy deposition guidance program that a kind of engineering adaptability is stronger.

Summary of the invention

The object of this invention is to provide a kind of method of the raising pressed engine incoming flow quantity of the catch based on laser energy deposition.The present invention proposes Gao Zhongying laser energy to puncture quasistatic ripple that incoming flow formed first and pressed engine precursor oblique shock wave interacts, give the optimum choice scheme of laser parameter and injection phase, make the incoming flow deflection originally may overflowed enter compressing section in intake duct, improve air inlet quantity of the catch.The shaped laser bundle that the present invention proposes is sheet light and the method focused on, and provides possible technique approach for controlling two dimensional surface punching type intake duct.The present invention can be applicable to supersonic and hypersonic aircraft air inlet quantity of the catch and controls.

The present invention describes and estimates pressed engine air inlet quantity of the catch and the distribution of precursor oblique shock wave, and implementation is as follows:

(1) flow field state around numerical simulation aircraft.Solving NS equation, is perfect gas or non-equilibrium gas according to incoming flow stagnation temperature determination gas model, is with reference to building and dividing computing grid, with true incoming flow conditions for foundation is determined to calculate initial conditions and incoming flow parameter with aircraft configurations.According to calculating intake duct flow, determine whether overflow occurs, precursor oblique shock wave position and intensity.

(2) in laboratory conditions, according to Mach and reynolds analogue criterion, design aircraft scale model carries out wind tunnel test, judges whether overflow occurs and precursor oblique shock wave position and intensity according to schlieren or shadowgraph.

It is sheet light that the present invention describes shaped laser bundle, and implementation is as follows:

(1) utilize high reflective mirror reflected beam, make beam center by predetermined laser energy deposition position;

(2) utilize recessed cylindrical mirror to be expanded by laser beam, make circular laser beam become elongated oval shape;

(3) utilize rectangular slot to limit oval-shaped laser bundle, slit length is set to inlet lip width, after determining slit length, determine slit width, and its index is ensure that as far as possible many laser energies pass through slit;

(4) utilize convex cylindrical mirror to converge sheet light, focus at flow field special position and puncture incoming flow.

The present invention establishes laser sheet optical and focuses on the method puncturing ultrasound velocity or Hypersonic Flow Field formation quasistatic ripple, and gives the optimum choice of laser parameter, and implementation is as follows:

(1) puncture place system of selection: pressed engine lip upstream elongation line and first precursor oblique shock wave point of intersection;

(2) laser output power size system of selection: the incoming flow enthalpy H of about 0.02 times, H=ρ _∞c _pt _∞v _∞l ², wherein c _pfor specific heat at constant pressure, L is lip width, ρ _∞, T _∞and V _∞be respectively free flow density, temperature and speed;

(3) laser frequency system of selection: select laser frequency according to speed of incoming flow, the point-source explosion ripple that single-pulse laser is caused merges formation quasistatic ripple.

The present invention gives quasistatic ripple that laser causes for improving the method for intake duct air inlet quantity of the catch, implementation is as follows:

(1) quasistatic ripple and precursor oblique shock wave interact after the wall of directive intake duct external compression section, enter compressing section in intake duct at the reflected wave of wall;

(2) after quasistatic ripple be high temperature, low pressure, density regions, incoming flow is entered this region by after the contracting of quasistatic wave pressure, carrys out flow path direction and deflects;

(3) the incoming flow deflection originally may overflowed enters compressing section in intake duct, and air inlet quantity of the catch is improved.

Advantage of the present invention is

1) two-dimensional laser energy injection mode, is convenient to control two-dimensional flow field.Ramjet engine air inlet two dimension often, adopts sheet light shaping light path to be planar configuration by focusing laser energy, focuses on the quasistatic ripple producing approximate two dimension after puncturing, be convenient to flowing and control.

2) energy injection size, position and frequency controllability are strong.Laser response is fast, and controllability is strong.By regulating laser to export energy model, can for different incoming flow conditions, the optimization of the control device of realization.

3) engineer applied is strong.Stronger applicability is all possessed to the inlet flow conditions of multiple off-design Mach number.

Accompanying drawing explanation

Fig. 1 improves air inlet quantity of the catch concept map for illustrating that laser energy of the present invention injects;

Fig. 2 is for realizing of the present invention light shaping index path;

Fig. 3 is that the point-source explosion ripple that laser of the present invention causes merges formation quasistatic ripple figure;

Fig. 4 is quasistatic ripple of the present invention and precursor oblique shock wave interaction diagram;

Fig. 5 is for realizing experimental setup layout chart of the present invention.

Embodiment

Now in conjunction with the accompanying drawings and embodiments the method that laser energy is used for improving pressed engine air inlet quantity of the catch by the present invention is described in further detail.Fig. 1 gives principle of the invention figure.

Implementation of the present invention is as follows: having analysed in depth on the basis of free stream Mach number lower than air inlet quantity of the catch reduction reason during design load, propose a kind of raising air inlet quantity of the catch method injected based on laser energy.The present invention is divided into four steps, namely determines that air inlet quantity of the catch and precursor oblique shock wave position and intensity step, laser beam reshaping are sheet light step, quasistatic ripple forming step and step.Specific embodiments is as follows:

Step one, determine air inlet quantity of the catch and precursor oblique shock wave position and intensity

This step is completed by numerical calculation and wind tunnel test two kinds of methods.Governing equation is the compressible Navier-Stokes equation of conservation form unsteady flo w:

$\frac{\∂Q}{\∂t}+\frac{\∂F}{\∂x}+\frac{\∂G}{\∂y}+\frac{\∂H}{\∂z}=\frac{{\∂F}_v}{\∂x}+\frac{{\∂G}_v}{\∂y}+\frac{{\∂H}_v}{\∂z}+S$

Wherein Q is conserved quantity, and F, G, H are without sticky (convection current) flux term, F _v, G _v, H _vfor viscosity (dissipation) flux term, every expression is as follows:

$Q=\left[\begin{array}{c}\mathrm{\ρ}\\ \mathrm{\ρu}\\ \mathrm{\ρv}\\ \mathrm{\ρw}\\ \mathrm{\ρE}\end{array}\right]F=\left[\begin{array}{c}\mathrm{\ρu}\\ \mathrm{\ρuu}+p\\ \mathrm{\ρvu}\\ \mathrm{\ρwu}\\ \mathrm{\ρEu}+\mathrm{pu}\end{array}\right]G=\left[\begin{array}{c}\mathrm{\ρv}\\ \mathrm{\ρuv}\\ \mathrm{\ρvv}+p\\ \mathrm{\ρwv}\\ \mathrm{\ρEv}+\mathrm{pv}\end{array}\right]H=\left[\begin{array}{c}\mathrm{\ρw}\\ \mathrm{\ρuw}\\ \mathrm{\ρvw}\\ \mathrm{\ρww}+p\\ \mathrm{\ρEw}+\mathrm{pw}\end{array}\right]$

$S=\left[\begin{array}{c}0\\ 0\\ \mathrm{\ρ\Ωw}\\ -\mathrm{\ρ\Ωv}\\ 0\end{array}\right]F_v=\left[\begin{array}{c}0\\ {\mathrm{\τ}}_{\mathrm{xx}}\\ {\mathrm{\τ}}_{\mathrm{yx}}\\ {\mathrm{\τ}}_{\mathrm{zx}}\\ {\mathrm{\β}}_x\end{array}\right]G_v=\left[\begin{array}{c}0\\ {\mathrm{\τ}}_{\mathrm{xy}}\\ {\mathrm{\τ}}_{\mathrm{yy}}\\ {\mathrm{\τ}}_{\mathrm{zy}}\\ {\mathrm{\β}}_y\end{array}\right]H_v=\left[\begin{array}{c}0\\ {\mathrm{\τ}}_{\mathrm{xz}}\\ {\mathrm{\τ}}_{\mathrm{yz}}\\ {\mathrm{\τ}}_{\mathrm{zz}}\\ {\mathrm{\β}}_z\end{array}\right]$

Wherein

$\left\{\begin{array}{c}{\mathrm{\τ}}_{\mathrm{xx}}=2{\mathrm{\μu}}_x+\mathrm{\λ}(u_x+v_y+w_z)\\ {\mathrm{\τ}}_{\mathrm{yy}}=2{\mathrm{\μv}}_y+\mathrm{\λ}(u_x+v_y+w_z)\\ {\mathrm{\τ}}_{\mathrm{zz}}=2{\mathrm{\μw}}_z+\mathrm{\λ}(u_x+v_y+w_z)\\ {\mathrm{\τ}}_{\mathrm{xy}}={\mathrm{\τ}}_{\mathrm{yx}}=\mathrm{\μ}(u_y+v_x)\\ {\mathrm{\τ}}_{\mathrm{yz}}={\mathrm{\τ}}_{\mathrm{zy}}=\mathrm{\μ}(v_z+w_y)\\ {\mathrm{\τ}}_{\mathrm{zx}}={\mathrm{\τ}}_{\mathrm{xz}}=\mathrm{\μ}(u_z+w_x)\end{array}\right.$

β _x＝uτ _xx+vτ _yx+wτ _zx-q _x

β _y＝uτ _xy+vτ _yy+wτ _zy-q _y

β _z＝uτ _xz+vτ _yz+wτ _zz-q _z

Under perfect gas supposition, gas meets following equation of state

p＝ρRT

$\mathrm{\ρe}=\frac{p}{\mathrm{\γ}-1}$

E is specific internal energy, than being:

$E=e+\frac{1}{2}(u^2+v^2+w^2)=\frac{p}{(\mathrm{\γ}-1)\mathrm{\ρ}}+\frac{1}{2}(u^2+v^2+w^2)$

In above representation, ρ, (u, v, w), p, T, e represent the interior energy of three velocity components, pressure, temperature and unit masses of density, rectangular coordinate system (x, y, z) respectively; E, E, γ, μ are expressed as the interior energy of unit mass, total energy, specific heats of gases ratio and coefficient of viscosity.If incoming flow stagnation temperature is higher than 1000K, then stationary point gas may exist and dissociates, then select non-equilibrium gas equation.

For wind tunnel test, then design processing aircraft scale model and wind-tunnel incoming flow parameter, design considerations is Mach and reynolds analogue criterion, and this work is mature technology, repeats no more.

Step 2, be sheet light by laser beam reshaping

Fig. 2 gives laser beam reshaping and the concrete grammar focused on.First utilize high reflective mirror (2) reflected beam (1), make beam center by predetermined laser energy deposition position; Recycle recessed cylindrical mirror (3) laser beam is expanded, make circular laser beam become elongated oval shape; Then utilize rectangular slot (4) to limit oval-shaped laser bundle, slit length is set to ram air duct lip width, after determining slit length, determine slit width, and its index is ensure that as far as possible many laser energies pass through slit; Finally utilize convex cylindrical mirror (5) to converge sheet light, focus at flow field special position and form high laser power density deposition region (6), puncture incoming flow.

Step 3, sheet light focused on puncture incoming flow, form quasistatic ripple

Fig. 3 gives multiple point-source explosion ripple and merges the process forming quasistatic ripple, and concrete steps are:

(1) according to numerical calculation and results of wind tunnel, judge precursor oblique shock wave position, lip upstream elongation line and first precursor oblique shock wave intersection point are decided to be laser energy decanting point;

(2) defining incoming flow enthalpy is: H=ρ _∞c _pt _∞v _∞l ², wherein c _pfor freely flowing specific heat at constant pressure, ρ _∞, T _∞and V _∞be respectively free flow density, temperature and speed, L is inlet lip width; Laser power definition is: W=Qf, wherein Q is single-pulse laser energy, and f is laser frequency, and the system of selection of laser output power size is about W=0.02H.

(3) selection of laser frequency f is the key factor that quasistatic ripple is formed.N-th pulsed laser energy punctures incoming flow and forms a point-source explosion ripple, and point-source explosion ripple moves with freely flowing to downstream while expansion; Meanwhile, (n+1)th pulsed laser energy punctures freely to flow and also produces point-source explosion ripple, the travelling speed of part for the downstream of this point-source explosion ripple is higher than the speed of the n-th point-source explosion corrugated upstream part, therefore, according to free stream velocity and point-source explosion ripple speed of expansion, adjustment laser frequency f, just can realize catching up with merging between point-source explosion ripple, and final formation is similar to the quasistatic wave structure of oblique shock wave.

Step 4, quasistatic wave pressure contracting incoming flow change its direction, improve air inlet quantity of the catch

Fig. 4 gives the numerical simulation typical consequence figure that quasistatic ripple improves ramjet engine air inlet air inlet quantity of the catch, laser beam (1) focuses in lip upstream elongation line (7) and first precursor oblique shock wave (8) point of intersection and punctures incoming flow and form quasistatic ripple (9), incoming flow (10) is contractd by quasistatic wave pressure and changes direction, compressing section (11) in flowing into.Fig. 5 gives the testing program for shock tunnel, and concrete steps are:

(1) when incidence arrives shock tube (12) low pressure end face, trigger signal is inputted digital delay signal generator (14) as 0 moment by pressure transducer (13).When flow field is stablized, digital delay signal generator (14) trigger laser (15) Output of laser, by wind-tunnel window (16) and sheet light shaping light path (17), in flow field, specified position punctures incoming flow.

(2) ultrasound velocity or hypersonic inlet flow conditions are determined by Rafael nozzle (18), and intake duct model is arranged in vacuum cabin (19), so that wind-tunnel starts.

(3) assessment of control effects adopts schlieren measure system and Flow Measuring System to realize.Flash of light source (20) and high speed camera (21) are the building blocks of schlieren system, and the two controls by digital delay signal generator (14), the represented by dotted arrows schlieren light path in figure.Signal input computer (23) Storage and Processing that Flow Measuring System (22) will collect.

Claims (1)

1. laser energy injects and improves pressed engine air inlet quantity of the catch method, comprises following steps:

Step one, estimate pressed engine air inlet quantity of the catch and precursor oblique shock wave distribution

In ultrasound velocity or Hypersonic Flow Field, for specific ramjet engine air inlet and precursor configuration, the method such as schlieren or shade experiment, numerical simulation is utilized to obtain the aircraft flow field state under specific inlet flow conditions; Judge whether air inlet quantity of the catch reaches design load according to compressing section mass flow rate in intake duct, obtain precursor oblique shock wave position and intensity simultaneously;

Step 2, be sheet light by laser beam reshaping

Utilize beam Propagation and transformation system, lasing light emitter is shaped as sheet light, be incident to flow field specified position; This system mainly comprises the assemblies such as high reflective mirror, recessed cylindrical mirror, rectangular slot and convex cylindrical mirror, and after laser is exported by laser, expand first through high reflective mirror reflection, recessed cylindrical mirror, rectangular slot shaping and convex cylindrical mirror assemble, formation sheet light enters flow field to be measured;

Step 3, sheet light focused on puncture incoming flow, form quasistatic ripple

Utilize post convex lens focus laser sheet optical, puncture incoming flow at lip upstream elongation line and first precursor oblique shock wave point of intersection and form point-source explosion wave structure; Laser output power size is about 2%, the H=ρ of intake duct windward side incoming flow enthalpy H _∞c _pt _∞v _∞l ², wherein c _pfor specific heat at constant pressure, L is inlet lip width, ρ _∞, T _∞and V _∞be respectively free flow density, temperature and speed; For pulsed laser, select laser frequency according to speed of incoming flow, the point-source explosion ripple that single-pulse laser is caused merges formation quasistatic ripple;

Step 4, quasistatic ripple and precursor oblique shock wave interact, and improve air inlet quantity of the catch

Quasistatic ripple and intake duct precursor oblique shock wave interact, and after quasistatic ripple, grain direction changes, and make the incoming flow deflection originally may overflowed enter interior compressing section, while air inlet quantity of the catch improves, air-flow stagnation pressure also obtains raising.