Abstract: The disclosure relates to a combustor including a heat exchange structure and a rocket including the combustor. The combustor according to an embodiment of the disclosure includes: an inner wall; an outer jacket arranged to cover an outer surface of the inner wall; a plurality of first heat exchange channels arranged between the inner wall and the outer jacket and through which a fuel introduced from a fuel tank flows; and a second heat exchange channel arranged between the inner wall and the outer jacket and through which a pressurized gas introduced from a pressurized gas tank flows.

Abstract: A liquid rocket engine assembly comprising a thrust chamber, a nozzle, and a joint structure. The joint structure attaches the thrust chamber and the nozzle and comprises at least one seal element and an attachment ring interposed between the thrust chamber and the nozzle. Fasteners extend between the nozzle and the thrust chamber through the at least one seal element and the attachment ring. Materials of the thrust chamber and of the nozzle comprise different coefficients of thermal expansion. A method of forming a liquid rocket engine assembly is also disclosed.

Abstract: There is disclosed an exhaust nozzle for a gas turbine engine. The exhaust nozzle comprises a frame extending along a longitudinal axis, and a convergent petal pivotably attached at a convergent pivot point to the frame and extending axially downstream and radially inward from the frame. The exhaust nozzle comprises a follower roller fixed to the convergent petal on a radially outer side of the convergent petal, and a cam defining a working surface configured to engage the follower roller to react a force from the convergent petal. The cam is movable along a travel in an axial direction to actuate radial movement of the follower roller to pivot the convergent petal. The cam defines a convex working surface such that a contact angle between the follower roller and the cam varies along the travel to thereby vary an axial component of the force reacted by the cam.

Abstract: A liquid rocket engine assembly comprising a thrust chamber, a nozzle, and a joint structure. The joint structure attaches the thrust chamber and the nozzle and comprises at least one seal element and an attachment ring interposed between the thrust chamber and the nozzle. Fasteners extend between the nozzle and the thrust chamber through the at least one seal element and the attachment ring. Materials of the thrust chamber and of the nozzle comprise different coefficients of thermal expansion. A method of forming a liquid rocket engine assembly is also disclosed.

Abstract: A rocket throat insert including an annular body having a radially inner annular wall portion and a radially outer annular portion. The inner wall portion has a contoured radially inner surface defining a nozzle throat. The outer portion includes an annular buttressing structure supporting the inner wall portion and defining one or more insulation gaps arranged annularly around the inner wall portion. The insulation gaps restrict the radial flow of heat through the annular body.

Abstract: A thrust reverser for reversing a thrust of a turbofan engine of an aircraft. The reverser includes a pivot door, a cascade component, and an actuation system. The door is moveable between lowered and raised positions in which a side outlet is, respectively, covered and uncovered. The cascade includes turning vanes, and is moveable between forward and rearward positions in which the cascade is positioned, respectively, not over and over the side outlet. The actuation system deploys the reverser by simultaneously moving the door to the raised position and moving the cascade to the rearward position over the side outlet, and stows the reverser by simultaneously moving the cascade to the forward position and moving the door to the lowered position. When the door is raised and the cascade is over the side outlet, airflow through the side outlet is directed at least partially forward to provide reverse thrust.

Abstract: A propulsion system according to an example of the present disclosure includes, among other things, a geared architecture configured to drive a fan section including a fan, and a turbine section configured to drive the geared architecture. The turbine section has an exit point, and a diameter (Dt) defined as the outer diameter of a last blade airfoil stage in the turbine section at the exit point. A nacelle surrounds a core engine housing. The fan is configured to deliver air into a bypass duct defined between the nacelle and the core engine housing. A core engine exhaust nozzle is downstream of the exit point. A downstream most point of the core engine exhaust nozzle is defined at a distance (Lc or Ln) from the exit point.

Abstract: The present disclosure relates generally to a sliding seal between two components. The sliding seal includes a carrier having one or more cavities formed therein. The one or more carriers may contain wave springs and/or compliant seals therein. Various embodiments provide loading of the seal in both the axial and radial directions, regardless of whether a pressure differential exists across the seal, by means of springs and/or ramped surfaces. Other combinations of carrier, wave springs, and compliant seals are also disclosed.

Abstract: A turbine engine convergent-divergent nozzle including an annular central element and an annular cap arranged coaxially around the central element to co-operate with the central element to define an annular flow channel for a gas stream from the engine. Between a throat section and an ejection section of the nozzle, the central element and the cap present respective internal profiles in longitudinal section that are modeled by curves having respective radii of curvature that are identical in absolute value.

Abstract: A turbojet engine nacelle includes a rear section having an internal structure. The internal structure surrounds a rear part of an engine compartment and delimits, with an ejection jet pipe, an outlet cross section for the ventilation of the engine compartment. The engine nacelle includes a moving element associated with a corresponding controller. The moving element is able to move between a withdrawn position in which the outlet cross section for ventilation is at a maximum and an engaged position in which the moving element partially reduces the outlet cross section for ventilation by comparison with the retracted position. The controller is capable of moving the moving element between the retracted and engaged positions.

Abstract: A thrust vectoring system is created with a convergent-divergent nozzle having a total angle no greater than 150 degrees. A divergent portion of the nozzle has a wall at a predetermined angle of at least 12° from the freestream direction. A disturbance generator is located on the wall to induce flow separation from the wall with the predetermined wall angle sufficient for the induced flow separation to extend upstream from disturbance generator substantially to a throat of the nozzle pressurizing the wall and creating a net vector angle in jet flow through the nozzle.

Abstract: A system and method of cooling a rocket motor component includes injecting a high pressure liquid coolant through an injector nozzle into a cooling chamber. The cooling chamber having a pressure lower than the high pressure liquid coolant. The liquid coolant flashes into a saturated liquid-vapor coolant mixture in the cooling chamber. The saturated liquid-vapor coolant mixture is at equilibrium at the lower pressure of the cooling chamber. Heat from the rocket motor component to be cooled is absorbed by the coolant. A portion of the liquid portion of the saturated liquid-vapor coolant mixture is converted into gas phase, the converted portion being less than 100% of the coolant. A portion of the coolant is released from the cooling chamber and the coolant in the cooling chamber is dynamically maintained at less than 100% gas phase of the coolant as the thrust and heat generated by the rocket motor varies.

Abstract: A gas turbine nozzle section of a gas turbine may include an inner endwall with a leading edge. A serpentine passage may be configured substantially within the leading edge. The serpentine passage may have an inlet and an outlet. Air may be received at the inlet and exhausted at the outlet, cooling the leading edge.

Abstract: A rocket propulsion system having a liquid fuel tank and a liquid oxidizer tank, where a liquid inert gas tank supplies liquid inert gas to a liquid inert gas pump driven by a turbine of the engine to pressurize the liquid inert gas, which is passed through a heat exchanger around the nozzle to vaporize the inert gas, that is then used to pressurize the liquid oxidizer tank so that a liquid oxidizer pump is not needed, or to pressurize both the liquid oxidizer tank and the liquid fuel tank so that a liquid oxidizer pump and a liquid fuel pump are not needed in the rocket engine.

Abstract: An exit manifold is disclosed which includes a manifold body that includes a plurality of inlets. The manifold body provides communication between the inlets and a discharge port. At least one of the inlets directs flow in a first direction and at least one of the inlets directs flow in a second direction. The first and second directions are opposite and the material flowing in these opposite directions collides in front of the discharge outlet. The collision of these two oppositely-directed flows creates a high pressure stagnation region that may block or impede flow from one or more inlets that may be in alignment with the discharge port.

Abstract: A system comprises a bypass duct, a turbine case, a turbine exhaust ring and a splash plate. The turbine case is formed along a radially inner margin of the bypass duct, and the turbine exhaust ring is coaxially disposed within the turbine case. The splash plate extends axially along the turbine exhaust ring, radially spaced between the turbine exhaust ring and the turbine case. There are cooling fluid apertures in the turbine case to provide cooling fluid flow from the bypass duct onto the splash plate, and impingement holes in the splash plate to provide impingement flow onto the turbine exhaust ring.

Abstract: Air bleed device for cooling components in a turbine engine, including an annular conduit (18) having a radially internal portion swept by an airflow (22) and which comprises at least one air inlet orifice (20) formed in an upstream radial wall (38) of the conduit (18), a flap valve (40) for controlling the airflow entering through the orifice (20) and of which the flapper (41) includes a plate (42) applied against the wall (38) and capable of being moved by sliding on said wall (38) by a maneuvering member (50) mobile in translation parallel to the wall (38) between a position in which the plate (42) closes off the orifice (20) and a position in which the plate (42) opens said orifice.

Abstract: A secondary-air nozzle of a two-flow jet engine having separated flows including an annular cowl element translatably mobile in an axial direction between an upstream retracted position allowing the engine to operate under direct thrust and a downstream extended position, and a grid thrust reverser including cylindrical ring sectors coaxial with the cowl element, including blades with a radial setting, and axially separated to provide radial guide passages therebetween, the cowl element opening the radial guide passages in the downstream extended position through the thrust reverser grids. The radius of the ring sectors forming the grids is not constant around the circumference of the cowl element, the radius of transverse cuts of at least one of the walls not being constant, when moving around the circumference of the cowl element, the cuts being made between the upstream edge of the cowl element and the downstream edge thereof.

Abstract: A nozzle liner for a rotatable nozzle includes a seal land and a rotatable seal for moving with the nozzle. The seal has a first diffusion hole for distributing cooling air if the rotatable seal is in a first position and a second diffusion hole for distributing cooling air if the rotatable seal is in a first position and if in a second position.

Abstract: A nozzle includes a center body. A shroud circumferentially surrounds at least a portion of the center body to define an annular passage between the center body and the shroud. A closed loop cooling circuit extends inside the center body. A method for cooling a nozzle includes flowing a cooling medium through a closed loop cooling circuit inside the nozzle.

Abstract: A method of assembling an injection device for use in a reactor injector feed assembly includes extending the injection device at least partially into a cavity. The injection device includes a plurality of substantially concentric conduits coupled to a modular tip that includes a plurality of cooling channels and a plurality of substantially annular nozzles defined therein. The method also includes coupling at least one coolant distribution device in flow communication with the plurality of cooling channels to facilitate removing heat from an outer surface of the injection device.

Abstract: In some embodiments a propulsion system includes a thrust chamber having an inside wall, an expansion nozzle mounted to the thrust chamber and having an interior and having an exterior, a main propellant injector mounted to the thrust chamber to inject a fluid in the interior of the thrust chamber, the fluid comprising oxidizer, fuel and internal film coolant, the internal film coolant ranging from about 1% to about 5% of the fluid, limited coolant tubing circumscribing the exterior of the expansion nozzle to circulate an external coolant, and an injector mounted to the expansion nozzle to inject the external coolant in the interior of the expansion nozzle, the external convective coolant about 2.5% of the fluid. The system operates at lower temperatures while having conventional amounts of thrust, in which the thrust chamber can be made of thin walls of lower cost conventional metals with simple coolant tube construction.

Abstract: A secondary fuel nozzle is formed by brazing and welding a central core, a cylindrical body, and a unitary secondary fuel nozzle portion. The central core has a central bore for receiving a liquid fuel cartridge, and at least two passages concentric with the central bore. The secondary fuel nozzle portion includes a base flange and a main shaft having a central bore for aligning with the central bore of the core and for receiving the liquid fuel cartridge, and a plurality of peripheral bores disposed at spaced locations about the central bore for flow communication with the concentric passages of the core. The core is brazed to the base flange and the cylindrical body is disposed around the core and welded to the base flange to define a one-piece secondary fuel nozzle assembly.

Abstract: One embodiment of the present invention includes a nozzle defining a passage to receive and discharge working fluid to produce thrust. The nozzle includes the first wall structure opposite a second wall structure. The first wall structure includes a first convergent flap pivotally connected to a first divergent flap. The second wall structure includes a second convergent flap pivotally connected to a second divergent flap. The first wall structure and the second wall structure define the throat along the passage and are reconfigurable to adjust dimensional area of the throat. One or more control valves modulate flow of the pressurized fluid into the passage through a first opening in the first wall structure and a second opening in the second wall structure approximate to the throat to change effective area of the throat by fluidic control.

Abstract: The present invention relates to rocket engine combustion chambers, and more particularly to an improved rocket engine combustion chamber having a jacket. In some embodiments, a combustion system for a rocket engine includes an injector, a cylindrical combustion chamber, and a jacket coupled to the combustion chamber and to the injector. The combustion chamber can expand axially and/or radially with respect to the jacket. The outer surface of the combustion chamber includes a plurality of flow channels. One or more piston seals and/or bellows can be included to allow axial expansion of the combustion chamber with respect to the jacket. A gap formed between the inner surface of the jacket and the outer surface of the combustion chamber allows for radial expansion of the combustion chamber with respect to the jacket.

Abstract: An apparatus and method fabricating a deflector-flare cone for a combustor is provided. The combustor includes an air swirler annular about a centerline axis of the combustor wherein the swirler includes an annular exit downstream of the swirler. The deflector-flare cone includes a single annular body including an engagement end configured to support the deflector-flare cone, an annular divergent portion extending downstream from the engagement end. The annular divergent portion includes a radially outer annular deflector portion and a radially inner annular flare cone portion that are separated by an annular gap extending between the deflector portion and the flare cone portion. The deflector-flare cone includes a plurality of cooling passages extending through the single annular body of the deflector-flare cone. The plurality of cooling passages are spaced circumferentially about the centerline axis and are configured to be coupled in flow communication with a cooling fluid source.

Abstract: A rotor of a supersonic rotary heat engine comprises a rotor axis about which the rotor is adapted and configured to rotate, a plurality of thrust matter passageways, and a plurality of cooling passageways. Each of the thrust matter passageways is at least partially bound by a gas permeable wall. The outlet port of each thrust matter passageway is adapted and configured to discharge gaseous fluid into an exhaust environment external to the rotor in a manner creating a torque on the rotor about the rotor axis. Each of the cooling passageways is in fluid communication with a respective one of the thrust matter passageways via the gas permeable wall that at least partially bounds the respective thrust matter passageway.

Abstract: A secondary fuel nozzle is formed by brazing and welding a central core, a cylindrical body, and a unitary secondary fuel nozzle portion. The central core has a central bore for receiving a liquid fuel cartridge, and at least two passages concentric with the central bore. The secondary fuel nozzle portion includes a base flange and a main shaft having a central bore for aligning with the central bore of the core and for receiving the liquid fuel cartridge, and a plurality of peripheral bores disposed at spaced locations about the central bore for flow communication with the concentric passages of the core. The core is brazed to the base flange and the cylindrical body is disposed around the core and welded to the base flange to define a one-piece secondary fuel nozzle assembly.

Abstract: A component configured for being subjected to a high thermal load during operation includes a wall structure with cooling channels adapted for handling a coolant flow. At least one first cooling channel is adapted to convey the coolant from a first portion of the component to a second portion of the component. At least one second cooling channel in the second portion is closed so that the coolant is at least substantially-prevented from entering the closed second cooling channel from a cooling channel in the first portion.

Abstract: A combustion chamber for expelling a hot gas stream from a rocket engine includes a combustion chamber wall and a plurality of cooling channels arranged inside the combustion chamber wall and configured to receive a flow of a cooling medium. Each cooling channel defines a longitudinal axis, a depth direction, and a substantially rectangular cross section. At least one cooling channel includes a plurality of depressions configured to prevent a stratification of the cooling medium in the at least one cooling channel. The plurality of depressions are arrange transverse to a direction of the flow direction and transverse to the longitudinal axis in the depth direction.

Abstract: A nozzle system includes a multitude of circumferentially distributed convergent flaps and seals that circumscribe an engine centerline. A cooling liner body cooperates with a cooling liner panel attached to respective convergent flaps and convergent seals to define an annular cooling airflow passageway which is movable therewith. Each cooling liner panels includes an arcuate cooling liner leading edge with a multiple of openings to distribute cooling airflow over both the inner “cold-side” and outer “hot-side” surfaces thereof. Through this backside cooling, thermal gradients are controlled at the attachment interface between the arcuate cooling liner leading edge and the main cooling liner body.

Abstract: A heat shield comprises a flexible inner jacket configured and disposed to be fitted around at least a portion of a component, and a flexible outer jacket configured and disposed to be fitted around the inner jacket.

Abstract: An engine wall structure includes an inner wall to which hot gas is admitted during engine operation, an outer wall, which is colder than the inner wall during engine operation, and at least two webs that connect the inner wall with the outer wall and delimit a cooling duct between the walls. The webs are mainly formed by a first material and the inner wall is mainly formed by a second material of other composition and other heat conductivity than the first material.

Abstract: In a fuel lance by means of which fuels can be injected, via at least two separate passages, into a combustion chamber alternately or simultaneously at an injection location arranged substantially at the lance tip, reliable operation is achieved, without the risk of flashbacks and also without coking, by virtue of the fact that the fuel lance, in addition to fuel, also passes purge air to the injection location, and that the purge air, at the injection location, is routed between the two fuel systems, in such a manner that these systems are shielded from one another by the purge air.

Abstract: An improved engine construction, such as a rocket engine construction is provided. The engine construction comprises a combustion chamber, a smooth wall nozzle, and a transition zone between the chamber and the smooth wall nozzle. The transition zone has a coolant system which includes a manifold formed from a non-copper material through which a coolant flows. In a high heat transfer embodiment, the transition zone includes an additional manifold formed from a copper based material.

Abstract: A combustion chamber/supersonic nozzle assembly is cooled by an array of coolant channels in the wall of the assembly with coolant being fed to the assembly at the throat plane between the subsonic (convergent) and supersonic (divergent) sections. A minor portion of the coolant entering at the throat plane is directed to coolant channels in the supersonic section wall, while the remainder is directed to a complex arrangement of channels in the subsonic section wall. The latter arrangement includes an outer layer of wide axially oriented channels for delivery of coolant to, and removal from, an inner layer of smaller, circumferentially oriented channels that are adjacent to the hot gas and carry the bulk of the coolant load. The path of coolant travel through each inner channel is relatively short, lessening the pressure drop through those channels relative to coolant channel arrangements of the prior art.

Abstract: Method and arrangement for providing a liquid fuel rocket engine member having a load bearing wall structure (11,14) including a plurality of cooling channels (11) for handling a coolant flow. Each cooling channel (11) is provided with a flow guiding surface (15) extending at an angle to the cooling channel axis, for providing the axial coolant flow with an added flow component in the radial direction.

Abstract: Method and arrangement for providing an outlet nozzle (10) for use in a liquid fuel rocket engine. The nozzle forms a body of revolution having an axis (11) of revolution and a cross section that varies in diameter along said axis. The nozzle has a wall structure having a plurality of mutually adjacent cooling channels, helically extending substantially in parallel from the inlet end (13) of the nozzle to its outlet end (14). The nozzle includes at least two longitudinally arranged sections (10a, 10b, 10c). A shift between a positive and a negative channel angle in the transition from one section to an adjacent section balances any roll momentum generated by friction of rocket exhausts against the nozzle wall.

Abstract: An improved engine construction, such as a rocket engine construction is provided. The engine construction comprises a combustion chamber, a smooth wall nozzle, and a transition zone between the chamber and the smooth wall nozzle. The transition zone has a coolant system which includes a manifold formed from a non-copper material through which a coolant flows. In a high heat transfer embodiment, the transition zone includes an additional manifold formed from a copper based material.

Abstract: A fluid flow nozzle is formed by a plurality of adjacent L-shaped channels forming successive channel pairs. Each channel has a linking member joined to a radial member. Each linking member is welded to an adjacent linking member forming a contiguous surface of linking members. Each radial member is oriented approximately perpendicular to a first side of the contiguous surface. A circumferentially enclosed chamber is formed on a second side of the contiguous surface. Each radial member is laser welded to a jacket at a distal end of each radial member. The jacket is oriented approximately parallel with the contiguous surface and separably spaced from the contiguous surface by the radial members. Each radial member forms one of a plurality of flow chambers between its adjacent radial member, the jacket and the contiguous surface. The flow chambers advantageously contain fluid in the event of a radial member rupture.

Abstract: A wall structure (2) configured to be exposed to a thermal load. The wall structure having at least two layers including a first layer (5) and a second layer (6). The second layer (6) is located closer to a source of the thermal load than the first layer (5), and the layers (5, 6) are arranged so that heat is allowed to be conducted from the second layer (6) to the first layer (5). Each of the first and second layers (5, 6) are adapted to carry a significant portion of a structural load, and the second layer (6) exhibits a higher thermal conductivity and/or a lower thermal expansion than the first layer (5). The invention reduces the thermal strain in the wall structure (2).

Abstract: The invention relates to a device for exhausting hot gases with a reduced signature, for instance exhaust gases from an exhaust (7, 8) of a tank. The device is of the type comprising a means for mixing (9, 33) of the hot gases with fresh air from the exterior of the tank. To prevent the exhaust from, for instance, reflecting radar radiation and emit IR radiation, the device is provided with a protecting means (10, 34) which is positioned outside at least parts of said means. The device may comprise a space (12, 32) which accommodates preferably the entire means for mixing. The space is defined on the one hand by a shell (11, 31) towards the other spaces of the tank and, on the other hand, by the protecting means towards the exterior. The protecting means has openings (23, 25) for passing preferably a gas mixture from the means to the exterior and fresh air from the exterior to said means.

Abstract: Method and arrangement for providing liquid fuel rocket engine member (10). The member forms a body of revolution having an axis of revolution and a cross section that varies in diameter along said axis. The wall structure includes a plurality of cooling channels (11). The outside of the wall structure includes a continuous sheet metal wall (14). The cooling channels (11) are longitudinally attached to the inside of the sheet metal wall. The method for manufacturing the rocket engine member (10) includes the steps of forming a sheet metal wall (14) having a wall section corresponding to the desired nozzle section, providing a plurality of channel members (15), and attaching the channel members (15) to the inside of the sheet metal wall (14).

Abstract: A method for forming an article having a wall that is at least partially fabricated from tubing. The methodology employs a pressurized fluid to deform the tubing such that an outer surface of the tubing substantially conforms to a predetermined first wall configuration, an inner surface of the tubing substantially conforms to a predetermined second wall configuration and each of segment or loop of the tubing is substantially contiguous with at least one other segment or loop between the first and second surfaces.

Abstract: In a first assembly step a coolant liner is formed having an outside surface. A plurality of coolant channels are formed on the outside surface. At least two inner conformal throat support sections and at least two outer conformal throat support sections are formed. The two inner conformal throat support sections are formed around the outside surface of the coolant liner to form a closed inner conformal throat outside surface. The inner conformal throat support sections are joined at inner throat seam lines. At least two outer conformal throat support sections are assembled around the closed inner conformal throat outside surface so as to cover the inner throat seam lines, to form a liner throat support assembly. An inlet manifold and an outlet manifold are assembled around the liner throat support assembly to form a hot isostatic press (HIP) assembly. A HIP'ed assembly is formed by HIP'ing the HIP assembly.

Abstract: A convergent-divergent rocket nozzle is formed by joining two coaxially aligned conical sections at a throat plane, each diverging outward from the throat plane. Coolant channels formed in the wall of the nozzle are arranged in spirals around the nozzle axis. Preferably, the conical sections are formed from platelet laminates rolled into conical form with a single spiral seam, and at least one of the conical sections is a composite of two or more component conical sections separately formed and then joined in a nested arrangement with the seams not superimposed. A further preferred construction is one in which the convergent end of one conical section is split radially into strips that are then spread apart to serve as bonding surfaces to bond to the other conical section.

Abstract: Method and arrangement for providing a liquid fuel rocket engine member (10). The member has a load bearing wall structure (14) having a plurality of cooling channels (11). For improving the heat transfer, a material with a higher thermal conductivity than the load bearing wall structure (14) is applied to the wall structure.

Abstract: Heat is extracted from the combustion gas in a rocket engine combustion chamber by diverting portions of the gas through channels in the nozzle wall. The channels are layered between channels of coolant, which in expander cycle rocket engines is uncombusted fuel, to achieve intimate heat exchange between the combustion gas and the fuel. The combustion gas channels are relatively short, returning combustion gas thus cooled to the chamber interior. By drawing combustion gas from the chamber interior into the chamber wall, the cooling process no longer relies on the combustion gas boundary layer for heat transfer as in the prior art.

Abstract: The invention concerns a cooling system for a post combustion jet nozzle, The jet nozzle includes a primary gas duct allowing a primary flow of gas, and a secondary air duct allowing a secondary flow of air. The secondary air duct surrounds the primary gas duct and is separated from it by a protective thermal shroud. The secondary air duct has a downstream end, and dampers surrounding an output section of the primary gas duct. The system includes a protective thermal shell in the secondary air duct, at the downstream end of said duct. The protective thermal shell bears an annular diaphragm extending out in front of the dampers and being provided with support sectors and inter-sector zones equipped with slots. The inter-sector zones define spaces between the diaphragm and the protective thermal shroud.

Abstract: The invention relates to an apparatus for increasing the heat transfer to the coolant at the inside of a nozzle wall provided with coolant channels of expander cycle rocket engines. To achieve this the invention proposes that, to disturb the boundary layer at the nozzle wall and thereby increasing the heat transfer, the inside of the nozzle wall facing the flame has a particularly chosen increased surface roughness of such a magnitude that it penetrates the viscous sub-layer of the boundary layer at the nozzle wall.