Patent GB-1327491-A (GB)
Title: Internal combustion engines
IPC: F04B47/10
Filed: 1970-04-01
Abstract: 1327491 Regulating and controlling engines NATIONAL RESEARCH DEVELOPMENT CORP 19 April 1971 [1 April 1970 (3)] 15517/70 15520/70 and 15522/70 Heading F1B I.C. engine power plant suitable for operation in a submersible hull comprises an I.C. engine, a compressed air supply for starting the engine and a supply of pure oxygen which is mixed with re-cycled exhaust gas to operate the engine in a re-cycle mode, the engine also being operable with conventional aspiration of atmospheric air, and control valves being provided for the different modes of operation, the valves being operated automatically in response to demand signals selecting a given mode of operation or changing from one mode to another. The plant includes a compression-ignition engine 10 coupled by a shaft 11 to an hydraulic pump 12 which provides pressure fluid to drive a motor 16 connected to an exhaust gas compressor 17. There is a by-pass around the pump 17, controlled by a valve A. The intake manifold 18 of the engine is connected to an atmospheric air intake 20 which includes a valve B and to a compressed air supply 22 through a valve C, a reducing valve 23 and a manual valve M. Alternatively, the manifold can receive a mixture of pure oxygen from a supply 24 controlled by a manual valve N, a reducing valve 26, a valve F, a second reducing valve 27, a throttling orifice 28 and a second valve G, and re-cycled exhaust gas supplied through a conduit 23 containing two valves D and E. The exhaust manifold 30 leads into a duct 31 into which sea-water is sprayed to cool the gas. The water is removed in a separator 34 and the gas then divides into two streams, one stream being re-cycled through conduit 36 and the other going to the exhaust pump through conduit 37. The pump increases the pressure of the gas to expel it through the pipe 38 against the surrounding water pressure. The temperature of the re-cycled gas is controlled by bleeding off gas into a duct 42 upstream of the cooling spray, and passing this gas through a throttle valve L before it enters the re-cycling duct. The intake manifold is also connected to a small pump 43 which reduces the pressure in the crank-case. The engine is water-cooled, the system including a pump 47. Hydrocarbon engine fuel is stored under pressure in a bottle 49. The operation of the engine in the various modes is therefore controlled by the five valves or groups of valves i.e. A, B, C, D-E and G-F, all these valves being spring-biased to their closed position, and opened pneumatically. The control system for the valves, Fig.2, consists of four first stage valves, 50, 51, 52A and 52B, all solenoid-operated and each having an inlet connected to the main compressed air supply 49. When de-energized  each of the valves is spring-returned to the lefthand position in Fig.2. The valves 50 and 51, when energized, supply a pilot air signal to second stage valves 53, 54. The engine is governed to run at constant speed in the re-cycle mode, and at constant speed or idling speed in the normally aspirated mode. A pneumatic cylinder 59 acts on the fuel pump governor control and a second pneumatic cylinder 58 actuates the start/stop control on the engine fuel pump. Operation. For a surface start, when the engine starter is operated a relay closes and energizes the first-stage valves. Valve 51, supplies a pilot signal which reverses valve 53 and compressed air then opens the exhaust bypass valve A and the manifold compressed air inlet valve B. At the same time valve 52B actuates cylinder 58 to the "RUN" position. The valves remain in this position during surface running, the cylinder 59 being moved between "IDLE" and "RUN" positions by energizing the solenoid of valve 61. To change to re-cycle operation, valve 51 is de-energized, so that valve 53 returns to its rest position and the valves A and B then close. Compressed air now passes to valves D-E and F-G (since valve 50 is already energized and is supplying a pilot air signal to valve 54) which open, so that the engine receives a mixture of pure oxygen and re-cycled exhaust gas, and runs at rated speed only, valve 61 being de-energized. For a submerged start, valve 50, is energized and in turn reverses valve 54 from its rest position. As the engine turns, the valves 52A and 52B are energized so that valve C is opened and the cylinder 58 is moved to the "RUN" position. When the starter switch is released, valve 50 is de-energized and the pilot air line slowly exhausts through the throttle valve 57, so that the valve 54 returns to its rest position and the valves D-E and F-G are opened. When the engine is shut-down, the cylinder 58 is exhausted rapidly through valve 52B, so that the fuel pump stop control returns to the stop position before the valves A and B or D to G close. Fuel/oxygen proportioning. Engine speed is controlled by a governor 69 mechanically connected to the rack of an injection pump 70. A lever 72 is also pivotally connected at one end to the rack, intermediate its ends to the shuttle of a servovalve 75, and at its other end to the centre rod 76 of a bellows unit. Oxygen at high pressure from a pipe 25 enters a cylinder 84, flows through a reducing valve 27, leaves by a port 92 and passes through a critical flow orifice 28. The pressure upstream of orifice 28 is transmitted to casing 77 around the bellows and if the actual pressure does not correspond with the desired pressure then the shuttle valve 75 moves to allow pressure oil from an inlet 81 to flow to one side or the other of a piston 85, which through the spring 93 controls the position of the valve member 90 and adjusts it to correct the oxygen pressure. In a modification, Fig.6 (not shown), the fuel pump control rod is connected to the same end of the lever 72 as is the bellows. To obtain satisfactory operation in the recycle mode, the gas pressure at the intake is sensed by an aneroid capsule, Fig.7 (not shown), which moves the shuttle of a servo-valve which in turn controls the flow valve of the motor driving the exhaust gas compressor. The pressure at  the intake is maintained at about 20 p.s.i.