In “Reciprocating Pumps” one could find a general schema and a few variants of a particular type of pumps based on it. For convenience, a few passages from “Reciprocating Pumps” are repeated here.
Here, a special variant of a pump of this type is presented, the pump, which is driven by a built-in internal combustion engine.
Following is a general schema of a Pump:
PL RL PB RR PR
AL CL B CR AR
It is a large tube divided by 4 walls into 5 compartments, from left to right:
AL, CL, B, CR and AR
It contains one movable part – a piston-rod assembly, consisting of 3 pistons
PL, PB and PR
connected with two “rods”:
RL and RR
“Rods” could be implemented as tubes to better resist bending forces on them, when they are under pressure.
Walls between chambers have tight openings for “rods”. They also help resisting bending forces, when “rods” are under compression.
A chamber B operates as a double acting pump.
Chambers AL and AR are a part of the engine. Only a part of these chambers without a “rod” in it is used to burn fuel, as it is in other internal combustion engines.
Note that when valves of the chamber B are closed, the piston-rod assembly cannot move. This is used to control working of the engine.
Chambers CL and CR have opening, trough which a “hand” connected to the “rod” is extended outside the main tube. These two “hands” reach to a Valve Control Box and this allows synchronization between opening/closing of valves and position of the movable piston-rod assembly.
In the pump driven by internal combustion, the same Valve Control Box contains controls for injection of fuel, controls allowing exit of exhaust, and controls for injection of compressed air.
Note that one joint Valve Control Box could synchronize operations of two or even more such pumps. For example, piston-rod assemblies of different pumps could move in opposite directions and this should minimize vibration caused by pumps operations.
We prevent hydraulic shocks in the system through smooth and slow opening and closing of valves controlled in the Valve Control Box.
Most likely, we would want chambers of different diameters. This could be done because pistons are confined to their respective chambers. The shape of chambers CL and CR should be defined only by demands of structural soundness of the pump during operations.
Obviously, in such case, we would not be able to use one tube to house all assembly, but would need to combine the pump from a few components of different diameters. They could be welded or joined some other way.
To minimize leaks of gasses and facilitate lubrication of “rods”, additional narrow chambers should be “carved out” from chambers CL and CR next to walls of adjacent chambers AL and AR. These chambers should be filled with lubricant.
An unusual feature of this design of the internal combustion engine is addition of a compressor. Usually, air is compressed by the pistons of the engine itself. Here, a separate air compressor is used. Compressed air is injected into the chamber of the engine twice, first to facilitate fuller evacuation of contents of the chamber after burning and after that second time to fill the chamber with compressed air for burning on the next step of operations.
Hence, three tanks need to be used together with the compressor. A large tank simply accumulates compressed air and facilitates maintaining the same level of air pressure. Two small tanks hold exact amount of compressed air needed on each cycle of the engine’s operation. They are filled from the large tank before exhaust has to be expelled; air from the first tank is used to facilitate evacuation of products of combustion and the second one to fill the chamber with fresh air for burning.
Note that a most likely use of such engine is to pump fluid of hydraulic transmission. In such case, it is natural to have a compressor driven by the same hydraulic transmission. It could be a compressor for general use, as long it provides air compressed to required level, or it could be a dedicated compressor.
We start with the state, where burning of fuel in the left chamber AL pushed piston-rod assembly right to its limit. The limit is defined by the Valve Control, which is aware of the position of piston-rod assembly via “hands” extending from the CL and CR chambers. Exhaust valve in the chamber AR is still open, as it has been during this movement from left to right, and products of the combustion in the chamber were mostly expelled.
From this point, the system goes through following steps preparing chamber AR
1. Movement of piston-rod assembly is blocked; it is held still by closed valves controlling movement in the chamber B
2. Air from the first small tank is used to expel remnants of products of combustion; after that first small tank is refilled with compressed air
3. Exhaust valve is closed and compressed air from the second small tank fills the chamber; after that second small tank is refilled with air
4. Piston-rod released and measured amount of fuel is injected in the chamber; it is ignited spontaneously or via a spark
This starts movement of piston-rod assembly from right to left, which expels exhaust from the chamber AL and pumps fluid in the chamber B. When this movement is complete, the system in the situation described above, only chambers AL and AR are flipped. The system goes through similar steps.
It is natural to use a special pump to inject fuel into the chamber. When the engine is pumping fluid of a hydraulic transmission, this pump could be driven by the same hydraulic transmission. Measures should be taken though, that amount of injected fuel is controllable.
Compressed air could be used to cool entire Engine. After that, it could be mixed with exhaust and burn in Afterburner. Gasses after Afterburner should exchange heat with going into the combustion chamber air and fuel.
Alexander Liss 7/24/2019