Influence of Pulse Energy Influence of Pulse Energy Deposition on Burning Deposition on Burning

Development in the ChannelDevelopment in the Channel

Khristianovich Institute of Theoretical and Applied Mechanics SB RAS

V.A. Zabaykin, P.K. Tretyakov

7th International Seminar on Flame Structure, July 11-15 2011, Novosibirsk

ВЛИЯНИЕ ИМПУЛЬСНОГО ЭНЕРГЕТИЧЕСКОГО ВОЗДЕЙСТВИЯ НА РАЗВИТИЕ ГОРЕНИЯ В КАНАЛЕ

In channels at flow Mach numbers above 1.5 the transition from a supersonic current to the subsonic one occurs in system of (direct, oblique, λ-shaped) shock waves. The arising complex wave structure is called a pseudo-shock.Such type of a current exists in gasdynamic lasers, supersonic wind tunnels and combustion chambers of scramjets. In the latter case the organization of burning in pseudo-shock leads to an intensification of mixing processes and raises intensity of burning.However, a control of pseudo-shock seems to involve considerable difficulties. In the report the new approach based on non-stationary influence on pseudo-shock is shown.

Problems of Burning in Channels at Supersonic Problems of Burning in Channels at Supersonic Flow Speed Flow Speed

Experimental Facility(Supersonic Combustion Wind Tunnel with Arc Heater)

M = 1 – 3

T0 = 1200-2700 K

W = 2 000 KWt

τ = 10 ÷ 100 s

Pseudoshock StructurePseudoshock Structure

Shlieren images, P - var

Shlieren images of stationary positions of pseudoshock

Р=0.18MPa

Р=0.20MPa

Р=0.22MPa

Р=0.24MPa

Р=0.26MPa1 – поток (air flow)2 – система скачков (shock train) 3 – область смешения (mixing region)4 – область псевдоскачка (pseudoshock)5 – распределение статического давления по оси (pressure on axis)6 – распределение статического давления по стенке канала (wall pressure)

Constant Area ChannelКанал постоянного сечения

Scheme of Flat Channel of Constant Cross-Section Схема плоского канала постоянного сечения

( 20×40×565 mm )

Foto

1 – nozzle М=2; 2 – quartz windows 20 × 150 mm

The Applied Ways of Periodic Influence

Mechanical Thermogasdynamic

Overlapped area of duct outlet The oscillogram of work of pulse-periodic plasmatron

Pseudo-shock Movement at External Periodic Influence

Videorecording: slow motion playback.

Without influence Maximum displacement Maximum re-entry

Frequency of influence f = 25 Hz

The experiment scheme : 1 – nozzle М=2;2 – channel with registration area; 3 – locations of pulse-periodic plasma input.

Flat channel 40×20×565 mm, throttling – mechanical or by a pulsed plasmatron

Experiments in the Axisymmetric Channel of Constant and Variable Section, an

Isothermal Stream

The scheme of the axisymmetric channel of constant section( d = 50 mm, L = 550 mm)

1 – Tepler instrument IAB-451; 2 – mechanical choke; 3 – CCD-camera.

Speed of movement of pseudo-shock upwards (a) and downwards (b) on the axisymmetric channel at throttling frequency 12.2 Hz.

а b

Speed of moving of pseudo-shock isn't a constant, and has a maximum in a middle part of a cycle

Refinement on dynamics of movement of pseudo-shock and possibility of its registration in the axisymmetric channel

Look of the central part of pseudo-jump in the cylindrical channel

Possibility of exact registration of pseudo-jump movement speed in axisymmetric channel by optical methods with the limited possibilities of registration is shown

It is found out that at periodic disturbances the movement rate of gasdynamic structures isn't a constant and has a maximum at 3-4 ms after a start of motion

Experiments in the Axisymmetric Channel of Constant and Variable Section, a High-Temperature Stream, Hydrogen Burning

The axisymmetric channel of constant section d = 50 mm

Cooled nozzle М=2 with a hydrogen injector

The channel of variable section: 1 – nozzle, 2 – channel D=50mm, 3 – expanding section, 4 – channel D=90mm, 5 – exhaust system.

Flame look in channel windows at hydrogen burning

Diffusive and pseudo-shock burning modes in the combined channel

The channel with сonstant and expansion sections

The power impulse shifts a diffusive mode of burning into pseudo-shock one

Diffusive mode

Pseudo-shock mode

Distribution of pressure and OH radiation for two modes of burning

Power delivery point

- Periodic power influence on an isothermal air stream in the channel leads to pseudo-shock moving up and down the stream; - Speed of moving of pseudo-shock in an isothermal stream in axisymmetric and rectangular channels at input of periodic disturbances is determined; its value falls within the limits of 5-25 m/s. At the organization of burning the speed of pseudo-shock decreases down to 1-2 m/s; - At periodic input of disturbances the speed of movement of gasdynamic structures isn't constant, and has a maximum at 3-4 ms after a start of motion; - It is experimentally established that for a mode with diffusive H2 burning a short-term power impulse supply into a stream leads to a pseudo-shock burning mode.

CConclusiononclusionss