The whole purpose of the 109-509 motor is to provide thrust, and this is derived from the disassociation of the propellants in the combustion chamber. The design of the combustion chamber and the propellant injectors was particularly important, and Walterwerke had refined this to a high degree of reliability and thrust efficiency. The operating pressure and heat of combustion required a well constructed unit, although in a production motor,the cost and ease of manufacture was equally important.

Interestingly, it is reported that the operating life of the combustion chamber was never properly determined. Most motor losses were due to failures other than those of the combustion chamber; accidents or enemy action. Walterwerke test-ran the combustion chamber continuously for twenty five minutes at full thrust without mechanical failure, well in excess of its operating parameters.

Shown here in sectioned form on the motor from the University of Minneapolis, the combustion chamber is 21.05 inches in length, comprising four main parts, the inner shell, outer shell, an intermediate filler and the burner plate. The combustion space itself is formed as a sphere 10.15 inches in diameter at its maximium. One end has a segment cut through where the burner plate is fitted, and at the opposite, an opening 3.38 inches in diameter forms the throat of the venturi.

The venturi itself is an expansion opening, six inches long, widening to a diameter of 6.7 inches at the exhaust gas exit.

The inner section is manufactured from a solid mild steel forging which has been heat treated to remove all the internal stresses before final machining to the correct size. The otherwise constant thickness is increased at the convergent section to cope with the stresses of combustion. Flanges are turned at the front and rear ends for making joints with the outer shell.

The outer shell is formed from mild steel, welded at the seam and cold pressed to the diameter of the rear cylindrical portion. The rearward section is mild steel, seam-welded into a cylinder, then butt welded to the forward section; a turned steel flange welded to the cylinder forms the rear joint. The joint between inner and outer shells is made by welding the flanges at the forward end, but at the rear, the flanges are free to slide relative to one another for differential expansion during operation. A seal is made by clamping asbestos string coated with graphite between the flanges, to ensure no loss of fluid from the cooling jacket.

Ease of manufacture requirements dictated the shape of the outer shell, so a filling piece was required to make sure that cooling fluid was moved around the outer surfaces of the inner shell at a reasonable velocity. This filler is made from two parts, bolted together around the inner shell. This fillet is shown in the illustrations above, and in the annotated diagramme below.

One thing which is shown in the sectioned unit above, is the bored hole in the burner plate (seen in cross section) which goes through the whole thickness of the burner plate. This is one of the borings into which the propellant burners are screwed. Also in the burner plate is another boring, although this does not go the full distance through the burner plate, but ends in an inner chamber. This is the C-Stoff inlet, only one of which is required to deliver C-Stoff to a group of several burners.

For further information about the propellant injectors or burners, follow this link;
Link to Injectors/Burners.

On the filling piece and the outer wall of inner chamber, are helical channels to swirl the cooling fluid around, ensuring a good heat transfer and so adequate combustion chamber cooling. This picture shows a section of the inner and outer shells (without the inner fillet) taken from a combustion chamber. The section of the inner shell clearly shows the size and orientation of the swirl vanes.

Cooling C-Stoff is delivered into the combustion chamber via a pipe welded to the outer shell, level with the venturi. The coolant fills the space behind the outer shell and is directed towards the exhaust nozzle, and is then turned back and fed into the gap between the filling piece and the inner shell. The C-Stoff flows around the surface of the inner shell guided by the swirl vanes, increasing the rate of flow around those portions of the chamber which need most heat transfer. At the forward end of the combustion chamber a second pipe, welded to the forward flange, of similar diameter to the inlet pipe, carries the C-Stoff out and back towards the motor.

A third pipe is welded at the lowest part of the combustion chamber into which is set the C-Stoff dump valve. This ensures that C-Stoff is drained away from the hot cooling jacket when the motor stops, either at the end of a power run, or when the motor shuts down accidentally.

 

The Burner Plate.

The burner plate is made from mild steel 1.8 inches thick, welded around its circumference to the inner shell. A flange machined around the burner plate, drilled with bolt holes is the means of mounting the combustion chamber to the thrust tube.

Through the burner plate are drilled twelve holes into which are screwed the propellant burners (injectors). Cut into the burner plate are four channels, each of which connects to a group of three burners.

The first stage C-Stoff delivery pipe from the propellant flow regulator supplies the group of burners at the bottom of the burner plate, the second stage the group at the top of the plate, and the third stage is divided into two, supplying the two zones at the side of the burner plate. The zoning method of bringing sets of burners into play enables the Walter motor to maintain high enough pressure to satisfactorily atomise propellant at minimal flow settings, maintaining efficient combustion at low power and low thrust.

For further information about the propellant injectors or burners, follow this link;
Link to Injectors/Burners.

Fuel Inlet Pipes.

From this picture, you can see that the propellant inlet pipes arrive down the inside of the motor thrust tube, and terminate in sets of branching connectors. Shown here, each of the large, pale coloured pipes branches into three. This is the T-Stoff inlet, and each pipe branches to serve a set of three burners. Knowing that there are twelve burners, it can be imagined that there must be "four" T-Stoff lines. Although at the burner plate end of the pipe runs this is true, leaving the propellant flow regulator there are only three T-Stoff lines, one corresponding to each stage of the motor thrust.

Therefore, you can imagine that, slightly before the view shown here, the largest (3rd-Stage) T-Stoff line divides into two;   and each of these branches then splits into the pattern of three. So you can see that when the motor is running, the first stage thrust, and second stages of thrust correspond to a set of three burners each, but when the final, 3rd stage is selected, thrust comes from adding in the final six burners to make a total of twelve burners running for full power, maximum thrust conditions. This is made clear in the following diagramme.

The first, second and third stage burner arrangement is shown in these two illustrations. The sets of three burners are arranged so that each stage produces an even spray pattern in the combustion chamber, and when the next stage of burners comes into operation, a thrust pattern is produced which is balanced across the dimensions of the combustion chamber.

T-Stoff pipes are shown in red, C-Stoff inlet pipes in green. The First Stage thrust setting (1), is the set of burners which is at the base of the burner plate. The Second Stage (2), adds to the first stage, using the set of burners towards the top of the burner plate.

Finally, the Third Stage thrust (3) is from the two sets of burners either side of the burner plate, keeping the thrust pattern even, and the thrust output in balance.

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