The eighteen pot injector head.
This is the first image blog from Alexsander Savochkin in what we hope will become an expanding resource for those wishing to find out more about the design and construction of the A4/V2 missile. The precise 3D CAD model imagery is based exclusively on original drawings produced in Germany from 1940 to 1945. When enough material has been uploaded we will create a fixed menu item called ‘Anatomy of the V2‘ where we hope to be able to offer coverage of the entire missile in detailed 3D models like the ones shown here – Robert J. Dalby, editor in chief, V2 Rocket History.com
Click the above video to see an animation of the diffuser cup inner core (the animation may take a few seconds to show at maximum resolution).
The image gallery below has all the above pictures in higher resolution, some with additional text, as well as additional pictures not included in this post.
V2 fuel injector inserts 3303D, 3304D, and 3305D for injector pot echelons D and E. Photo shows swirl inlet aperture size and position.The total number of each insert type is shown, each of the 18 pots carried a total of 44 inserts. An additional 24 feed holes were drilled into the burner cup, occupying two rows B and C having 12 holes each. V2RH image
Sample set of 3303D type fuel injector inserts that were found in Peenemünde in part of a group that were bunched together in a space about 300mm in diameter with the remains of packaging. They appear to be manufacturing samples and and some have been graded with numbers 1,2,3, as well as with red and white paint to show the burner cup echelon position (C or D). Five different manufacturers are represented in this group. V2RH collection image
Fuel injector inserts for production series 18-pot injector head. The top row shows the injector face, second row shoes the same types from the rear. The lowermost insert have been halved to reveal the cavity shape, orifice edge, inlet and cooling apertures. Note that the insert in column A, 2131E, is two piece construction, and pressed together for assembly (see additional photo). On test, the parts had to remain together under a separation force of 300kg.
V2 Fuel Injector insert: part code 2131E from injector pot echelon A (nearest to LOX spray head). The push-together two part construction of the insert is shown here. The two parts were pushed together in a specially shaped tool set that compressed the thin skirt on the female part into a recess cut into the male part. The failure test for this component required that the mated parts resist a separating force of 300kg. The two part design was dictated by the small size of the 2mm exit orifice and the funnel shaped introduction to the exit orifice. In the case of the other three standard inserts, the large 6mm exit orifice allowed a sub 6mm milling cutter, with a thin support shaft and a top chamfer, to be used in such a way that the area below the exit orifice could be undercut to create an injector cavity with a diameter larger than the 6mm entry point.
Cutaway section of fuel and liquid oxygen (LOX) injector pot. The exhibit shows the bell shaped thick inner wall of the burner with three tiers of fuel injector inserts (A,D, and E). The central copper alloy LOX spray injector is also well displayed in this image. The thin steel outer shell of the burner cup is shown and affords a good view of the head cavity that supplies fuel to the injector inserts - one A type injector is shown party cut through on the right, its rear portion showing inside the fuel cavity. V2RH image
Cutaway section of fuel and liquid oxygen (LOX) injector pot. The exhibit shows the bell shaped thick inner wall of the burner with three tiers of fuel injector inserts (A,D, and E). As well as the two rows of plain drilled apertures B and C. The central copper alloy LOX spray injector is also well displayed in this image and shows the three letter armament code of the manufacturer (elr = H.K. Rudolf, Pilsen) and the 1943 date of manufacture on one face of the hex nut. Note the close proximity of the tier A injector inserts to the LOX injector. The spary from these injectors plays directly onto the lower section of the LOX spray head. This section of the burner cap had the lowest temperature and as a result tier A insert did nor require cooling pres. See associated picture. V2RH image
Standard fuel injector inserts for production series 18-pot injector head. Insert 1 (3304D/3305D) shows four thin wires demonstrating the angles of all four 'cooling' pores. Insert 2 (3305D/2131E) has two 1.3mm twist drill showing the edge bores for the gyroscopic swirl inlets. Insert 3 (3305D) shows another view of the cooling pore angle and origin. V2RH image
The injector head fragment shown here, is from an 4B 1000 kg thrust engine that was developed at Kummersdorf in 1938/39 by Dr Walter Thiel's combustion research group. The fragment, clearly the remains of an explosion, was actually found in a scrap pile in Peenemüde but the engine was probably tested (and destroyed) at the Kummersdorf army testing station. V2RH collection image.
Relic of prototype A4 25-ton 1940/41 aluminium injector head basket (or pre-chamber) showing 68 copper alloy inserts in 5 rows. The standard configuration would later become 44 inserts in 3 rows 25 2mm diameter drilled holes in two rows situated at row 3 and 4 (counting from nearest the camera). Photo courtesy Host Beck Collection
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The injector head section of the 4B 1000kg thrust rocket engine is a precursor to the injector pot or 'pre-chamber' design used later for each of the 18-pots of the 25-ton V2 rocket engine. Most of the essential ingredients are shown in this drawing from 1940. Drawing no 1848E Deutsches Museum München online archive ref FA 014/12829
HVP drawing no 1203D showing burner cup 'diffuser system' disposition for 19-pot head (at this stage the 25 ton thrust injector head had nineteen so called 'pre-chambers' or pots as no central fuel valve was present). HVP drawing dated 1939.
Specification for fuel injector inserts showing orifice size, type, and A to E echelon position. Peenemünde document dated 30th October 1943. Of note on this document is the combination of high and low volume injector inserts (3304D and 3305D) in the echelon E position of the 12 cups comprising outer ring I. It shows that each cup or pot on this outer ring had 16 inserts at the lowermost position E with 12 of the inserts with three inlet apertures (3305D) and 6 with only two inlet apertures (3304D being lower flow volume) positioned in the segment covering 165 degrees and closest to the outside edge of the head. HAP11 (Heimat-Artillerie-Park 11, AKA armament code: mpe), drawing number 4554D, Deutsches Museum München
Drawing from the Army Experimental Station Peenemünde dated 1939. The specification describes an insert template that could be used for a range of outlet and inlet orifice sizes. The German text beginning (eingedrehte ...) translates as 'Center-line of screw used for holes to be drilled later', and the hole dimensions are not specified on this document. HVP drawing number 1113 E, Deutsches Museum München
HAP11 drawing of standard 3304D fuel injector screw insert. showing details of primary swirl cavity and orrifice and all additional apertures including the four small cooling pores. HAP11 (Heimat-Artillerie-Park 11, AKA armament code: mpe), drawing number 4554D, Deutsches Museum München
Diagram showing cut-away presentations of the settled configuration of standard four 'swirl' inserts used in the V2 rocket engine's 18-pot head from 1943 until the end of the war. The inserts are shown with their drawing code identification. All of the insert types used in the injector head are shown, however there were additional screw-in type fuel supply inserts, used to provide a fuel cooling balance function, located radially in the lower part of the combustion cavity.
Photo shows a small section of the burner cup with row A (2131E) fuel injector inserts with three row B drilled holes below. The two undamaged inserts carry the armament code 'csl'. The relic was found near a workshop in the Development works Pennemünde. Slag from the cutting flame and damage to the inserts at both ends of the relic would indicate that the section was cut from a steel burner cup using a gas cutter (fuel and oxygen) for purposes unknown. V2RH collection image
Single nozzle insert test rig used by V2 Rocket History to test spray shape and volume at supply pressures consistent with fuel pressures specified for the injector head of summer 1944. The test system features an adjustable pressure regulator and fluid pressure gauge. For test purposes the device was simply connected to a relatively high pressure mains water supply. And although water does not have the same viscosity of the 75% Ethenol to 25% water mix of the V2's fuel it was considered close enough by the German technicians, who regularly used plain water as a substitute when testing issues related to furl flow rather than combustion. A 2131E fuel injector insert is shown installed in the holder at the front of the rig, but as the thread was the same on all inserts the nozzle can be changed for other models easily with aid of a pin spanner. See video for a demonstration of this simple test system.
Single nozzle insert test rig used by V2 Rocket History to test spray shape and volume at fluid supply pressures consistent with fuel pressures specified for the injector head of summer 1944. A 2131E fuel injector insert is installed in the holder at the front of the test rig, but as the thread was the same on all inserts the nozzle can be changed for other models easily with aid of a pin spanner. See video for a demonstration of this simple test system.
Fuel injector inserts for production series 18-pot injector head showing general shape and thread position. For further details see associated image. The lowermost insert have been halved to reveal the cavity shape, orifice edge, inlet and cooling apertures. V2RH image
Industrial magazine advert for Gustav Schlick printed in 1918 and showing graphic of steam boiler jets. The company, formed in 1902, had a wide expertise in all aspects of industrial spray technology and were able to steer the direction of fuel injector development along fruitful lines after they became consulting contractors to Dr Walter Thiel's combustion research group in 1937.