US3817690A - Combustion devices - Google Patents

Combustion devices Download PDF

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Publication number
US3817690A
US3817690A US00302395A US30239572A US3817690A US 3817690 A US3817690 A US 3817690A US 00302395 A US00302395 A US 00302395A US 30239572 A US30239572 A US 30239572A US 3817690 A US3817690 A US 3817690A
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United States
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downstream
facing surface
step change
flow
combustion device
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US00302395A
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W Bryce
P Street
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UK Secretary of State for Defence
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UK Secretary of State for Defence
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23RGENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
    • F23R3/00Continuous combustion chambers using liquid or gaseous fuel
    • F23R3/02Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration
    • F23R3/16Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration with devices inside the flame tube or the combustion chamber to influence the air or gas flow
    • F23R3/18Flame stabilising means, e.g. flame holders for after-burners of jet-propulsion plants

Definitions

  • ABSTRACT Primary Examiner-Meyer Perlin Assistant Examiner-Larry I. Schwartz Attorney, Agent, or FirmCameron, Kerkam, Sutton, Stowell & Stowell [57] ABSTRACT
  • the invention relates to combustion devices wherein a flame stabilisation zone is formed in the wake of a body disposed in a swiftly moving gas stream.
  • the invention provides a combustion device comprising a bluff-body disposed in a gas stream, the body having an aerodynamically smooth upstream-facing portion terminating downstream through a step change of section in a substantially flat downstream-facing surface extending transversely to the direction of flow of the stream, and means for influencing flow over the body to induce stable vortex formation adjacent said downstream facing surface.
  • Such means comprise suction means, suction being applied from the interior of the body in each region of the step change of section.
  • Combustion devices may include a flow divider extending downstream of the downstream facing surface to separate vortices originating at the step change of section.
  • the present invention relates to combustion devices wherein a flame stabilisation zone is formed in the wake of a body disposed in a swiftly moving gas stream.
  • baffles In aircraft gas turbine jet propulsion engines, extra power can be developed by burning additional fuel in an afterburner. It has long been the practice in such installations to use fixed baffles to produce stable turbulent (or recirculation) zones in their wakes wherein flames will maintain themselves. Such baffles offer undesirable resistance to flow during such time as afterbuming is not in operation.
  • One of the more common forms of fixed baffle is a V-shaped gutter having its apex pointing upstream of the flow, the extreme simplicity of the arrangement tending to outweigh adverse considerations. By setting the arms to an included angle of the order of 45, or slightly less according to flow velocity, a reasonable optimum between resistance and the provision of an adequate recirculation zone can be obtained.
  • baffle resistance can be critical in de- 7 termining the total amount of afterbuming which can be employed, and an after-bumer system having a lower pressure loss when in the non-operating condition is desirable, provided that the penalties arising out of other considerations are not too severe.
  • the present invention is concerned with means directed towards this end.
  • One of the more common forms of device comprises a body having a profile which normally gives rise to low drag and from which flow is caused to separate when afterbuming is required by discharging air or other gas from the body across the direction of main flow. It has also been proposed, for example in prior Brit. Pat. No. 1,2 l 8, l 22, to utilise a body normally giving rise to high drag with resultant turbulent wake and, when after-burning is not required, to influence the boundary layer of flow over the body so as to reduce the wake.
  • the present invention is on similar lines but wake reduction is achieved in somewhat different manner.
  • a combustion device comprises a member disposed within a gas flow duct so as to produce a flame stabilisation zone in a swiftly moving gas stream and having a bluff-body configuration including a smooth upstream-facing portion with step change of section to a substantially flat downstream-facin g surface extending transversely relative to the direction of flow through the duct, and means for influencing flow over the member to induce stable vortex formation adjacent said downstream-facing surface.
  • suction is applied from the interior of the member in the region of the step change of section.
  • FIGURE is an axial section through an afterburner duct including a flame stabiliser.
  • the afterburner duct shown in the FIGURE comprises a cylindrical casing 1 extending between a turbine outlet and a jet propulsion nozzle (neither of which is shown), the direction of gas flow being from left to right as indicated by the arrows at the left.
  • An annular tubular member 2 mounted coaxially within the duct has an aerofoil leading-edge surface 3 directed upstream relative to flow through the duct and terminates downstream in a flat surface 4 normal to the streamwise axis of the member, a step change of section occurring between the two surfaces.
  • Annular ori fices 5, 6 extend through the peripheral boundary of the member 2 in the region of change of section between the surfaces 3, 4.
  • Gases passing along the duct will flow around the curved surface 3 of the member 2 as far as the change of section. In the absence of any external influence, flow will separate from the member 2 at the change of section to form turbulent recirculation zones in its wake as shown in the upper part of the drawing. Liquid or gaseous hydrocarbon fuel introduced into the duct and ignited will burn in the recirculation zone where the turbulence will act to maintain a flame pattern.
  • the fuel supply is discontinued and suction is applied to the interior of the member 2.
  • the suction acts by way of the orifices 5, 6, as indicated by the arrows S in the lower part of the drawing, on flow passing over the member 2 to form vortices V adjacent to the downstream facing surface 4.
  • the amount of suction applied is sufficient to maintain rotation of the vortices at a velocity similar to that of the normal flow through the duct, entrainment of the latter will occur causing it to be changed to a streamline stable flow pattern within a very short distance, with consequent drag reduction.
  • the orifices 5, 6 may be in the form of substantially continuous slots extending around the member 2, or in the form of a series of shorter slots or they may be de fined by a row of holes.
  • a flow divider extending along the duct from the downstream-facing surface 4, as indicated in dotted lines at 7 in the drawing, in order to keep the vortices separate and of the same order of magnitude since there may be a possibility of one entraining the other.
  • a combustion device for installation in a gas flow duct to form therein a flame stabilisation zone, said combustion device comprising a member having a bluff-body configuration including an aerodynamically smooth upstream-facing portion, said portion terminating downstream through a step change of section of the member in a substantially flat downstream facing surface extending transversely relative to the direction of said flow, and suction means establishing low pressure in the interior of the member to influence said gas flow over said member, a stable vortex formation adjacent said downstream-facing surface being induced thereby, said member having at least one opening in each region of step change at opposite edge portions of said downstream-facing surface wherethrough suction is applied.
  • a combustion device as claimed in claim 1 including a flow divider extending downstream of said downstream-facing surface whereby vortices originating at said step change of section at opposite edge portions of said downstream-facing surface are separated.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combustion Of Fluid Fuel (AREA)
  • Pre-Mixing And Non-Premixing Gas Burner (AREA)

Abstract

The invention relates to combustion devices wherein a flame stabilisation zone is formed in the wake of a body disposed in a swiftly moving gas stream. The invention provides a combustion device comprising a bluffbody disposed in a gas stream, the body having an aerodynamically smooth upstream-facing portion terminating downstream through a step change of section in a substantially flat downstream-facing surface extending transversely to the direction of flow of the stream, and means for influencing flow over the body to induce stable vortex formation adjacent said downstream facing surface. Preferably such means comprise suction means, suction being applied from the interior of the body in each region of the step change of section. Combustion devices according to the invention may include a flow divider extending downstream of the downstream facing surface to separate vortices originating at the step change of section.

Description

United States Patent [191 Bryce et al.
[ June 18, 1974 COMBUSTION DEVICES [75] Inventors: William Dean Bryce, Farnham;
Peter George Street, Fleet, both of England [73] Assignee: The Secretary of State for Defence in Her Britannic Majesty s Government of the United Kingdom of Great Britain and Northern Ireland, London, England [22] Filed: Oct. 31, 1972 [21] Appl. No.: 302,395
[30] Foreign Application Priority Data Nov. 1, 1971 Great Britain 50635/71 [52] US. Cl. 431/350, 60/39.72 R
[51] Int. Cl. F02g 1/00 [58] Field of Search 60/39.72 R, 261; 431/350 [56] References Cited UNITED STATES PATENTS 2,771,743 11/1956 Lovesey 60/39.72 R
3,600,892 8/1971 Bryce 60/39.72 R
3,618,318 11/197] Bryce 60/39.72 R
Primary Examiner-Meyer Perlin Assistant Examiner-Larry I. Schwartz Attorney, Agent, or FirmCameron, Kerkam, Sutton, Stowell & Stowell [57] ABSTRACT The invention relates to combustion devices wherein a flame stabilisation zone is formed in the wake of a body disposed in a swiftly moving gas stream.
The invention provides a combustion device comprising a bluff-body disposed in a gas stream, the body having an aerodynamically smooth upstream-facing portion terminating downstream through a step change of section in a substantially flat downstream-facing surface extending transversely to the direction of flow of the stream, and means for influencing flow over the body to induce stable vortex formation adjacent said downstream facing surface.
Preferably such means comprise suction means, suction being applied from the interior of the body in each region of the step change of section.
Combustion devices according to the invention may include a flow divider extending downstream of the downstream facing surface to separate vortices originating at the step change of section.
4 Claims, 1 Drawing Figure PATENTEDJun 18 I974 COMBUSTION DEVICES The present invention relates to combustion devices wherein a flame stabilisation zone is formed in the wake of a body disposed in a swiftly moving gas stream.
In aircraft gas turbine jet propulsion engines, extra power can be developed by burning additional fuel in an afterburner. It has long been the practice in such installations to use fixed baffles to produce stable turbulent (or recirculation) zones in their wakes wherein flames will maintain themselves. Such baffles offer undesirable resistance to flow during such time as afterbuming is not in operation. One of the more common forms of fixed baffle is a V-shaped gutter having its apex pointing upstream of the flow, the extreme simplicity of the arrangement tending to outweigh adverse considerations. By setting the arms to an included angle of the order of 45, or slightly less according to flow velocity, a reasonable optimum between resistance and the provision of an adequate recirculation zone can be obtained.
Nevertheless, baffle resistance can be critical in de- 7 termining the total amount of afterbuming which can be employed, and an after-bumer system having a lower pressure loss when in the non-operating condition is desirable, provided that the penalties arising out of other considerations are not too severe. The present inventionis concerned with means directed towards this end.
Various schemes have already been proposed with this end in view and many of them employ aerodynamic means. One of the more common forms of device comprises a body having a profile which normally gives rise to low drag and from which flow is caused to separate when afterbuming is required by discharging air or other gas from the body across the direction of main flow. It has also been proposed, for example in prior Brit. Pat. No. 1,2 l 8, l 22, to utilise a body normally giving rise to high drag with resultant turbulent wake and, when after-burning is not required, to influence the boundary layer of flow over the body so as to reduce the wake. The present invention is on similar lines but wake reduction is achieved in somewhat different manner.
A combustion device according to the invention comprises a member disposed within a gas flow duct so as to produce a flame stabilisation zone in a swiftly moving gas stream and having a bluff-body configuration including a smooth upstream-facing portion with step change of section to a substantially flat downstream-facin g surface extending transversely relative to the direction of flow through the duct, and means for influencing flow over the member to induce stable vortex formation adjacent said downstream-facing surface.
In a preferred form of the invention, suction is applied from the interior of the member in the region of the step change of section.
An embodiment of the invention will now be de scribed by way of example with reference to the accompanying diagrammatic sole FIGURE which is an axial section through an afterburner duct including a flame stabiliser.
The afterburner duct shown in the FIGURE comprises a cylindrical casing 1 extending between a turbine outlet and a jet propulsion nozzle (neither of which is shown), the direction of gas flow being from left to right as indicated by the arrows at the left. An annular tubular member 2 mounted coaxially within the duct has an aerofoil leading-edge surface 3 directed upstream relative to flow through the duct and terminates downstream in a flat surface 4 normal to the streamwise axis of the member, a step change of section occurring between the two surfaces. Annular ori fices 5, 6 extend through the peripheral boundary of the member 2 in the region of change of section between the surfaces 3, 4.
Gases passing along the duct will flow around the curved surface 3 of the member 2 as far as the change of section. In the absence of any external influence, flow will separate from the member 2 at the change of section to form turbulent recirculation zones in its wake as shown in the upper part of the drawing. Liquid or gaseous hydrocarbon fuel introduced into the duct and ignited will burn in the recirculation zone where the turbulence will act to maintain a flame pattern.
When afterbuming is not required, the fuel supply is discontinued and suction is applied to the interior of the member 2. The suction acts by way of the orifices 5, 6, as indicated by the arrows S in the lower part of the drawing, on flow passing over the member 2 to form vortices V adjacent to the downstream facing surface 4. Where the amount of suction applied is sufficient to maintain rotation of the vortices at a velocity similar to that of the normal flow through the duct, entrainment of the latter will occur causing it to be changed to a streamline stable flow pattern within a very short distance, with consequent drag reduction.
The precise mechanism whereby this effect is achieved is not yet fully understood but it is believed that the initial application of suction causes diversion of flow boundary layer whereby a vortex is initiated, some of the vortex flow in turn being drawn off by the suction until a stage is reached when the main flow suddenly changes direction, somewhat after the manner of a bi-stable fluidic switch. The boundary layer of flow over the curved surface, instead of breaking away as previously is transferred mainly to the vortex flow and the vortex becomes stabilised during such time as suction is maintained, part of the boundary layer being drawn into the orifices 5, 6.
The orifices 5, 6 may be in the form of substantially continuous slots extending around the member 2, or in the form of a series of shorter slots or they may be de fined by a row of holes.
In an embodiment of the invention there is provided a flow divider extending along the duct from the downstream-facing surface 4, as indicated in dotted lines at 7 in the drawing, in order to keep the vortices separate and of the same order of magnitude since there may be a possibility of one entraining the other.
What we claim is:
l. A combustion device for installation in a gas flow duct to form therein a flame stabilisation zone, said combustion device comprising a member having a bluff-body configuration including an aerodynamically smooth upstream-facing portion, said portion terminating downstream through a step change of section of the member in a substantially flat downstream facing surface extending transversely relative to the direction of said flow, and suction means establishing low pressure in the interior of the member to influence said gas flow over said member, a stable vortex formation adjacent said downstream-facing surface being induced thereby, said member having at least one opening in each region of step change at opposite edge portions of said downstream-facing surface wherethrough suction is applied.
2. A combustion device as claimed in claim 1 including a flow divider extending downstream of said downstream-facing surface whereby vortices originating at said step change of section at opposite edge portions of said downstream-facing surface are separated.
occupying a plane normal to the direction of gas flow.

Claims (4)

1. A combustion device for installation in a gas flow duct to form therein a flame stabilisation zone, said combustion device comprising a member having a bluff-body configuration including an aerodynamically smooth upstream-facing portion, said portion terminating downstrEam through a step change of section of the member in a substantially flat downstream facing surface extending transversely relative to the direction of said flow, and suction means establishing low pressure in the interior of the member to influence said gas flow over said member, a stable vortex formation adjacent said downstream-facing surface being induced thereby, said member having at least one opening in each region of step change at opposite edge portions of said downstream-facing surface wherethrough suction is applied.
2. A combustion device as claimed in claim 1 including a flow divider extending downstream of said downstream-facing surface whereby vortices originating at said step change of section at opposite edge portions of said downstream-facing surface are separated.
3. A combustion device as claimed in claim 1, said member having two openings therein, each said opening comprising a slot, said slots extending along opposite edges of said downstream-facing surface wherethrough suction is applied.
4. A combustion device as claimed in claim 1 wherein said member is of annular form, said member occupying a plane normal to the direction of gas flow.
US00302395A 1971-11-01 1972-10-31 Combustion devices Expired - Lifetime US3817690A (en)

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GB5063571A GB1376319A (en) 1971-11-01 1971-11-01 Combustion devices

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GB (1) GB1376319A (en)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4048797A (en) * 1974-12-06 1977-09-20 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Combustion apparatus
US4051670A (en) * 1975-05-30 1977-10-04 United Technologies Corporation Suction vent at recirculation zone of combustor
US4336789A (en) * 1978-10-05 1982-06-29 Rinnai Kabushiki Kaisha Cooking gas oven
US4790744A (en) * 1986-03-14 1988-12-13 Centre National De La Recherche Scientifique Burner with low emission of polluting gases
US5236327A (en) * 1990-11-16 1993-08-17 American Gas Association Low NOx burner
US5323614A (en) * 1992-01-13 1994-06-28 Hitachi, Ltd. Combustor for gas turbine
US5588825A (en) * 1995-12-13 1996-12-31 Governers Of The University Of Alberta Lean premixed fuel burner
US6575733B1 (en) * 1997-11-10 2003-06-10 Gourmeli International N.V. Fuel combustion method and reactor
US20050026096A1 (en) * 2001-11-23 2005-02-03 Staffler Franz Josef Streamlined body and combustion apparatus having such a streamlined body
US20090151360A1 (en) * 2007-12-18 2009-06-18 United Technologies Corporation Combustor
US20130133329A1 (en) * 2011-11-25 2013-05-30 Institute Of Engineering Thermophysics, Chinese Academy Of Sciences Air fuel premixer having arrayed mixing vanes for gas turbine combustor
US20130327046A1 (en) * 2012-06-06 2013-12-12 General Electric Company Combustor assembly having a fuel pre-mixer
US8979525B2 (en) 1997-11-10 2015-03-17 Brambel Trading Internacional LDS Streamlined body and combustion apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2771743A (en) * 1951-08-10 1956-11-27 Rolls Royce Gas-turbine engine with reheat combustion equipment
US3600892A (en) * 1968-06-10 1971-08-24 Technology Uk Combustion devices
US3618318A (en) * 1968-06-10 1971-11-09 Technology Uk Combustion devices

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2941361A (en) * 1952-10-15 1960-06-21 Nat Res Dev Combustion apparatus having a flame stabilizing baffle

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2771743A (en) * 1951-08-10 1956-11-27 Rolls Royce Gas-turbine engine with reheat combustion equipment
US3600892A (en) * 1968-06-10 1971-08-24 Technology Uk Combustion devices
US3618318A (en) * 1968-06-10 1971-11-09 Technology Uk Combustion devices

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4048797A (en) * 1974-12-06 1977-09-20 The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Combustion apparatus
US4051670A (en) * 1975-05-30 1977-10-04 United Technologies Corporation Suction vent at recirculation zone of combustor
US4336789A (en) * 1978-10-05 1982-06-29 Rinnai Kabushiki Kaisha Cooking gas oven
US4790744A (en) * 1986-03-14 1988-12-13 Centre National De La Recherche Scientifique Burner with low emission of polluting gases
US5236327A (en) * 1990-11-16 1993-08-17 American Gas Association Low NOx burner
US5460513A (en) * 1990-11-16 1995-10-24 American Gas Association Low NOx burner
US5323614A (en) * 1992-01-13 1994-06-28 Hitachi, Ltd. Combustor for gas turbine
US5588825A (en) * 1995-12-13 1996-12-31 Governers Of The University Of Alberta Lean premixed fuel burner
US6575733B1 (en) * 1997-11-10 2003-06-10 Gourmeli International N.V. Fuel combustion method and reactor
US8979525B2 (en) 1997-11-10 2015-03-17 Brambel Trading Internacional LDS Streamlined body and combustion apparatus
US20050026096A1 (en) * 2001-11-23 2005-02-03 Staffler Franz Josef Streamlined body and combustion apparatus having such a streamlined body
US20090151360A1 (en) * 2007-12-18 2009-06-18 United Technologies Corporation Combustor
US8800290B2 (en) * 2007-12-18 2014-08-12 United Technologies Corporation Combustor
US20130133329A1 (en) * 2011-11-25 2013-05-30 Institute Of Engineering Thermophysics, Chinese Academy Of Sciences Air fuel premixer having arrayed mixing vanes for gas turbine combustor
US9234662B2 (en) * 2011-11-25 2016-01-12 The Institute of Engineering Thermophysics, The Chinese Academy of Sciences Air fuel premixer having arrayed mixing vanes for gas turbine combustor
US20130327046A1 (en) * 2012-06-06 2013-12-12 General Electric Company Combustor assembly having a fuel pre-mixer
CN103471136A (en) * 2012-06-06 2013-12-25 通用电气公司 Combustor assembly having a fuel pre-mixer
US9395084B2 (en) * 2012-06-06 2016-07-19 General Electric Company Fuel pre-mixer with planar and swirler vanes

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Publication number Publication date
FR2169784B1 (en) 1977-03-18
FR2169784A1 (en) 1973-09-14
DE2253390A1 (en) 1973-05-10
JPS4875915A (en) 1973-10-12
GB1376319A (en) 1974-12-04

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