Internal combustion engine, method for operating an internal combustion engine, cylinder, cylinder liner and closing plate for an internal combustion engine

Abstract

 An internal combustion engine (1) and corresponding method, cylinder, closing plate, cylinder and kit of parts, in particular a two-stroke engine, preferably a diesel two stroke engine, which comprises at least one piston (10) arranged in a cylinder (11). Said piston (10) and said cylinder (11) define a variable combustion chamber (101) and a variable second chamber (102). The variable combustion chamber (101) is fluidly connectable to the compressor side of a turbocharger (2,2') via at least one inlet opening (111) and to the turbine side of the turbo charger (2,2') via an exhaust opening (112). The second chamber (102) is fluidly connectable to the compressor side of the turbocharger (2,2') to introduce a compressed air flow into the second chamber (102). The compressed air flow is interruptible such that the second chamber (102) is disconnected from the turbocharger (2, 2') and the second chamber (102) comprises an outlet opening (113) for reducing a pressure of the second chamber (102). The outlet opening (113) preferably comprises a controllable chamber valve.

Description

[0001] The invention is directed to an internal combustion engine and a method for operating an internal combustion engine. The invention is further directed to a cylinder, a cylinder liner and a chamber closing plate according to the generic part of the independent claims.

[0002] Several attempts have been made to improve the efficiency of internal combustion engines. The improvement of efficiency has higher impact on the consumption of fuel as bigger the engine is. In particular, in huge combustion engines, such as two stroke diesel engines in ships, improvement of efficiency is advantageous.

[0003] For example, CH 414 265 proposes, to add a generator to a two stage turbocharger to recuperate energy which is generated by the turbochargers. Such system is complex. Retrofitting of existing engines requires a lot of parts. Furthermore, the generator needs additional parts for aligning its voltage, current and frequency for example to the existing board net.

[0004] JPH 079 79 26 discloses an internal combustion engine, wherein the scavenging chamber is divided into an upper and a lower chamber for supplying two different air streams to the cylinder to reduce the overall temperature of the intaken air. Such a system requires a second turbocharger with an intercooler. Such systems are complex and cost intensive.

[0005] The aim of the invention is to overcome the drawbacks of the prior art according to the characterizing part of the independent claims. In particular and among other aspects, the invention provides an internal combustion engine and a method for operating an internal combustion engine which provides optimized brake specific fuel consumption (BSFC) and enables retrofitting of existing engines.

[0006] An internal combustion engine according to the invention comprises at least one piston which is arranged in a cylinder. The piston and the cylinder define a variable combustion chamber and a variable second chamber. Typically, the piston moves upwards and downwards inside the cylinder and thus divides the cylinder in an upper and a lower space. Said upper space defines the combustion chamber and said lower space defines the second chamber. The size of said chamber is dependent on the actual position of the piston. The internal combustion engine might be a two-stroke engine and preferably a diesel two stroke engine.

[0007] The variable combustion chamber is fluidly connectable and in particular connected to the compressor side of a turbocharger via at least one inlet opening. Further, the combustion chamber is connectable and in particular connected to the turbine side of the turbo charger via an exhaust opening. The variable second chamber is fluidly connectable and in particular connected to the compressor side of the turbocharger to introduce a compressed air flow into the second chamber.

[0008] As herein described and used for, the expression opening does not refer only to one single opening. One or an opening, as used herein, may comprise one or more openings.

[0009] The compressed air flow is interruptible such that the second chamber is disconnected from the turbocharger. The second chamber comprises an outlet opening for reducing a pressure of the second chamber. The outlet opening may comprise a controllable chamber valve.

[0010] Turbochargers provide air at a specific pressure, typically up to 5 bar in ship diesel engines. This pressure is existent in the second chamber below the piston. The interruption of the compressed air flow and the outlet opening of the second chamber enables to reduce the pressure within the second chamber and thus reduces the resistance against the piston movement and thus enhances the efficiency of the engine.

[0011] It may be advantageous, if said second chamber valve is controlled according to specific engine values. Specific engine values may be for example values of the pressure of the compressed air, of the pressure inside the second chamber, of the position of the piston or valves, of the engine load, of engine speed, of break mean effective pressure and combinations thereof.

[0012] Such a control allows operating the engine in a manner according to specific requirements, such as low BSFC, while granting the reliability of the operations.

[0013] Furthermore, such a control allows the regulation of the air flowing into the second chamber. It should be set to maximize the efficiency improvement while ensuring the correct operations of the engine, like a sufficient scavenging flow in a 2-stroke engine.

[0014] Preferably, the at least one inlet opening comprises a controllable inlet valve.

[0015] In a preferred embodiment, the inlet valve and the second chamber valve might be made from a single component, such as a 3-way valve.

[0016] Preferably, said inlet valve is controlled according to specific engine values as described herein.

[0017] Such a control allows operating the engine in a manner according to specific requirements, such as low BSFC, while granting the reliability of operations.

[0018] The exhaust opening of the internal combustion engine may comprise an exhaust valve which is preferably controllable. The exhaust valve may be controlled according to specific engine values as described herein and thus in such a manner to take into account specific requirements such as low BSFC or low emissions.

[0019] The internal combustion engine may comprise a turbo charger. In a preferred embodiment it is a multistage turbo-charger, preferably a two-stage turbo charger.

[0020] A multistage turbo-charger offers to extract a higher amount of energy from the exhaust gases. This surplus of energy allows delivering more pressurized air that can be expanded in the second chamber. Consequently the possible improvement of efficiency is higher than with a single stage turbocharger..

[0021] The internal combustion engine may be a crosshead engine.

[0022] This allows the arrangement of the openings in a replaceable manner and without complicated arrangements.

[0023] Advantageously, the outlet opening may be arranged in a second chamber closing plate. A second chamber closing plate is an element, which enables to offer a closed room below the piston. In a preferred manner, the second chamber closing plate is arranged on the bottom of a cylinder liner of the cylinder, in which the piston moves upwards and downwards.

[0024] The arrangement of the outlet opening in a pressure closing plate enables easy maintenance and allows refitting or upgrading existing engines.

[0025] The outlet opening may also be arranged in the cylinder liner.

[0026] Typically, the cylinder liner comprises an inlet opening. By arranging the outlet opening in the cylinder liner, inlet opening and outlet opening may be combined. Furthermore, a combination of the associated valves is possible. This reduces material costs and facilitates production.

[0027] The outlet opening may be connected the external environment. Alternatively, the outlet opening may be connected to a pressure vessel.

[0028] Thus, it might be possible, to collect the pressurized air from the second chamber. This air could be used for an on board air supply or for storage and reintroduction into the combustion cycle. Thus, the internal combustion engine may work like a piston compressor and pump or pressurize air which has blown into the second chamber.

[0029] Alternatively or additionally, the outlet opening might be connected to the compressor side of the turbocharger for recirculating or reintroduction of the discharged air.

[0030] Such an arrangement improves BSFC.

[0031] Alternatively or additionally, the outlet opening might be connected to a charge air cooler. Thus, the discharged air might be used as a cooling medium to cool down the charge air.

[0032] Another aspect of the invention is directed to a method for operating an internal combustion engine which comprises at least one piston arranged in a cylinder. Said piston and said cylinder define a variable combustion chamber and a variable second chamber which is in fluid connection to the compressor side of a turbocharger to introduce a compressed air flow into the second chamber.

[0033] The internal combustion engine might be a two-stroke engine and in particular a diesel two-stroke engine. Preferably the internal combustion engine is an internal combustion engine as herein described. The engine comprises a combustion stroke from the upper dead ceanter to the lower dead center and a compression stroke from the lower dead center to the upper dead center.

[0034] During at least a part of the combustion stroke, the compressed air flow to the second chamber is interrupted and an outlet opening is opened to reduce a pressure of the second chamber.

[0035] The air of the second chamber might be led to the atmosphere or to a pressure vessel or alternatively to the compressor side of a turbo charger or to a charge air cooler.

[0036] The interruption of the compressed air flow and the outlet opening of the second chamber enable to reduce the pressure within the chamber and thus reduces the resistance against the piston movement.

[0037] During at least a part of the compression stroke, an upward movement of the piston may be supported by compressed air. Said compressed air is preferably delivered by a turbo charger.

[0038] Such support reduces the energy needed to move the piston upwards.

[0039] Preferably, the compressed air is led to the second chamber via a preferably controllable inlet valve. Such an inlet valve may be controlled according to specific engine values and/or according fixed values and/or in a manner according to specific requirements, such as low BSFC.

[0040] The controllable inlet valve might be opened 40° to 60° preferably 50°+- 5° and most preferably 50° +-2° before a lower dead center position of the piston and preferably closed 140° to 70° preferably 125° to 80° more preferably 100° °+- 5° and in particular 100°+-2°, before an upper dead center position of the piston.

[0041] The controllable chamber valve might be opened 130° to 0° preferably 110° to 30°, more preferably 70° °+- 5° and in particular 70° +-2°, before an upper dead center position of the piston and preferably closed 40° to 60° preferably 50°+- 5° and in particular 50°+-2° before a lower dead center position of the piston.

[0042] An exhaust valve might be opened 100° to 120° preferably 110°+-5° and in particular 100° +-2° after an upper dead center position of the piston and preferably closed 60° to 140° preferably 100°+- 5° and in particular 100° +-2° before a lower dead center position of the piston.

[0043] These values enable the operation of the engine in a reliable state in a wide range of modes.

[0044] Furthermore, the timing values and angles might change from cycle to cycle, preferably as a function of load and of the specific installation of the engine.

[0045] Further, it might be advantageous, if the inlet valve is closed before the upper dead center while the outlet opening is not opened. This leads to an expansion of the pressurized air in the second chamber and thus to lower temperatures. Therefore, cylinder and piston are cooled down.

[0046] The air, which is discharged from the second chamber during the combustion stroke, might be led to the atmosphere or led back to the compressor side of the turbocharger for recirculating or reintroduction of the discharged air or might be used for an on board air supply or for storage and reintroduction into the combustion cycle by charging a pressure vessel.

[0047] The control of the respective valves and in particular the control of the inlet valve in the second chamber enables to regulate the amount of air which enters into the second chamber and which can be expanded. The higher is the amount of air which enters, the higher the work done on the piston.

[0048] To allow correct operation of a 2-stroke engine, a pressure difference must be granted between the intake receiver and the exhaust environment.

[0049] This pressure difference allows the air to flow from the intake to the exhaust and clean the cylinder from the exhaust gases from the previous cycle (scavenging process).

[0050] The pressure difference will be reduced, if part of the intaken air is used for the second chamber. Thus, depending on load or other specific values, the reduction of pressure has to be limited in order to still keep a certain air mass-flow through the cylinder and consequently grant a sufficient scavenging. This minimal air mass-flow is depending on the engines actual state and is known to the person skilled in the art.

[0051] The use of a two-stage turbocharger provides a higher pressure difference between intake and exhaust than a single stage turbo-charger. Thus, this enables a wider range of regulation and typically more air could be used in the second chamber.

[0052] A further aspect of the invention is directed to a cylinder liner for an internal combustion engine, in particular an internal combustion engine as described herein, said cylinder liner is adapted to accommodate a piston which divides the cylinder liner in a combustion chamber and a second chamber. The cylinder liner comprises an inlet opening for connection to a compressor side of a turbocharger and an exhaust opening for connection to the turbine side of the turbo charger. The cylinder liner comprises an outlet opening for regulating the pressure in the second chamber, preferably by a controllable chamber valve.

[0053] Such a cylinder liner enables the replacement of a cylinder liner whilst upgrading or refitting an existing internal combustion engine.

[0054] A further aspect of the invention is directed to a cylinder or a cylinder bank comprising a cylinder liner as herein described.

[0055] Typically, more than one cylinder is arranged in a cylinder bank which is adapted to accommodate more than one piston. Thus, it may be advantageous to prepare a cylinder bank with one or more cylinder liners. This allows upgrading an existing engine fast and with minimal effort. Different settings might be preadjusted.

[0056] The cylinder may comprise a chamber closing plate in which the outlet opening is arranged.

[0057] In a preferred manner, the second chamber closing plate is arranged on the bottom of a cylinder liner of the cylinder, in which the piston moves upwards and downwards.

[0058] This enables to provide a spare part or a replacement part and enables fast upgrading of a cylinder.

[0059] A cylinder as described herein may be manufactured such that the inlet opening and the outlet opening are arranged in a three-way-valve.

[0060] Such an arrangement enables to use the same openings in the cylinder as an inlet and as an outlet.

[0061] A further aspect of the invention is directed to a second chamber closing plate for an internal combustion engine, in particular an internal combustion engine as described herein. Said second chamber closing plate is connectable to a cylinder such that it closes the cylinder to form a second chamber.

[0062] A second chamber closing plate enables to provide an additional part which is easy to install and enables to refit or upgrade an existing internal combustion engine.

[0063] Advantageously, an outlet opening is arranged in the second chamber closing plate. The outlet opening may have a controllable chamber valve.

[0064] A second chamber closing plate in which an outlet opening is arranged enables to upgrade an existing internal combustion engine easily and without major changes. Maintenance and replacement is simplified. Furthermore, a second closing plate including the controllable chamber valve enables replacement in a fast way of a full assembly which might be preassembled in one step.

[0065] A further aspect of the invention is directed to a kit of parts for retrofitting an internal combustion engine. Said kit comprises at least a second chamber closing plate as herein described. Further, the kit comprises a controllable inlet valve.

[0066] The kit may comprise a cylinder liner and preferably a cylinder liner as herein described.

[0067] Such kits enable to provide a set of parts which are aligned to each other.

[0068] With reference to the following drawings, several aspects of the invention are described in a non-limiting way, wherein the figures show

Figure 1:

a schematic view of an internal combustion engine,

Figure 2:

a schematic view of a working cycle.

[0069] Figure 1 shows a schematic view of an internal combustion engine 1. The internal combustion engine 1 is connected to two serial arranged turbo-charger 2 and 2'. Each of the turbo-chargers comprise a compressor 20, 20' and a turbine 21,21'. A separate air cooler 16,16' is assigned to each turbo-charger 2,2'. The compressor 20,20' of each turbo-charger 2,2' could be by-passed with a compressor by-pass valve 14,14'. Furthermore, each turbine may be by-passed with a turbine by-pass valve 15,15'. Thus, it is possible to by-pass one of the turbo-chargers 2,2', e.g. the second turbo-charger 2' and to run the internal combustion engine 1 solely with the first turbo-charger 2. This could be useful, if one of the turbochargers has a malfunction. The by-pass valves 14,15,14',15' might also be partially opened or closed according to desired operating modes.

[0070] Figure 2 shows schematically several phases of a working cycle of an internal combustion engine. In figure 2a, a cylinder 11 is shown in which a piston 10 is accommodated. The piston 10 is on its lower position, the lower dead center. On the cylinder 11, an inlet opening 111, an exhaust opening 112 and an outlet opening 113 is arranged. The piston 10 divides the volume of the cylinder in a combustion chamber 101 and a second chamber 102 (see Figure 2b). For clarity reasons, some of the parts are depicted with reference numbers in the first two phases only.

[0071] As mentioned above (figure 2a), piston 10 is on its lower dead center. The intake opening 111 and the exhaust opening 112 are open. Air from a turbo-charger is blown into the combustion chamber 101 and scavenges the exhaust gases through the exhaust opening 112. The outlet opening 113 is closed. This is the typical configuration when the compression stroke begins, as described with the following steps. The piston 10 moves now upwards (see figure 2b) and begins to compress the air which has been blown into the combustion chamber 101. The exhaust opening is now closed according to specific engine values. The inlet opening stays open and is now connected to the second chamber 102. It might be also possible to replace the inlet opening 111 with to independent inlet openings to control the inlet of compressed air to the combustion chamber and to the second chamber independently. The volume below the piston, i.e. the second chamber, is filled with compressed air from the turbo-charger. The piston 10 is supported from the pressure of the air during its upstroke. Figure 2c shows the position of the piston 10 before it reaches its upper dead center. The intake opening 111 is now closed. Based on the further upward movement of the piston 10, the volume of the second chamber 102 gets bigger and thus, the pressurized air inside the second chamber 102 expands and thus cools down. This enables to take out energy of the hot parts of the engine and to cool them down.

[0072] In the next step (see figure 2d), the combustion has begun and the combustion stroke is described as follows. The piston 10 is near its upper dead center. The outlet opening 113 of the second chamber 102 is now opened. The pressurized air in the second chamber 102 can expand to atmospheric pressure. The resistance inside the engine is minimized.

[0073] The piston 10 now moves downwards (see figure 2e) and discharges the expanded air from the second chamber 102. The discharged air might be led to atmosphere or to a pressure vessel or back to the working cycle for example. During the downstroke movement, the exhaust valve 112 is opened according to specific engine values. The intake valve is opened on a later stage and allows blowing pressurized air into the combustion chamber 101 to scavenge the exhaust gases. The outlet valve 113 is now closed (figure 2f).

[0074] Figure 2g shows the beginning of the cycle on a state between the states of figures 2a and 2c.

Claims

1. An internal combustion engine (1), in particular a two-stroke engine, preferably a diesel two stroke engine, comprising at least one piston (10), arranged in a cylinder (11), wherein said piston (10) and said cylinder (11) define a variable combustion chamber (101) and a variable second chamber (102),
wherein the variable combustion chamber (101) is fluidly connectable to the compressor side of a turbocharger (2,2') via at least one inlet opening (111) and to the turbine side of the turbo charger (2,2') via an exhaust opening (112), said second chamber (102) is fluidly connectable to the compressor side of the turbocharger (2,2') to introduce a compressed air flow into the second chamber (102),
characterized in that
the compressed air flow is interruptible such that the second chamber (102) is disconnected from the turbocharger (2, 2') and in that the second chamber (102) comprises an outlet opening (113) for reducing a pressure of the second chamber (102), said outlet opening (113) preferably comprising a controllable chamber valve.

2. The internal combustion engine (1) of claim 1, characterized in that the at least one inlet opening (111) comprises a controllable inlet valve.

3. The internal combustion engine (1) of any of claims 1 or 2, wherein said outlet opening (113) is arranged in a second chamber closing plate or wherein said outlet opening is arranged in a cylinder liner.

4. Method for operating an internal combustion engine (1), preferably a two-stroke engine and in particular a two-stroke diesel engine, comprising at least one piston (10), arranged in a cylinder (11), wherein said piston (10) and said cylinder (11) define a variable combustion chamber (101) and a variable second chamber (102) which is in fluid connection to the compressor side of a turbocharger (2,2') to introduce a compressed air flow into the second chamber (102), preferably an internal combustion engine according to one of claims 1 to 3, having at least a combustion stroke and a compression stroke
characterized in that, during at least a part of the combustion stroke, the compressed air flow to the second chamber (102) is interrupted and an outlet opening (113) is opened to reduce a pressure of the second chamber (102).

5. The method according to claim 4, characterized in that during at least a part of the compression stroke, an upward movement of the piston (10) is supported by compressed air preferably of a turbo charger (2,2').

6. The method according to claim 5, wherein the compressed air is led to the second chamber (102), via a preferably controllable inlet valve, said controllable inlet valve is preferably opened 40° to 60° before a lower dead center position of the piston and preferably closed 140° to 70° before an upper dead center position of the piston (10).

7. The method according to one of claims 4 to 6, wherein the controllable chamber valve is opened 130° to 0° before an upper dead center position of the piston and preferably closed 40° to 60° before a lower dead center position of the piston (10).

8. Cylinder liner for an internal combustion engine (1), preferably according to one of claims 1 to 3, said cylinder liner being adapted to accommodate a piston (10) which divides the cylinder (11) in a combustion chamber (101) and a second chamber (102), wherein said cylinder liner comprises an inlet opening (111) for connection to a compressor side of a turbocharger (2,2') and an exhaust opening (112) for connection to the turbine side of the turbo charger (2,2'), characterized in that the cylinder liner comprises an outlet opening (113) for regulating the pressure in the second chamber (102(, preferably by a controllable chamber valve.

9. Cylinder (11) comprising a cylinder liner according to claim 8.

10. The cylinder (11) of claim 9, wherein said outlet opening is arranged in a second chamber closing plate.

11. The cylinder according to claim 10 characterized in that the inlet opening and the outlet opening are arranged in a three-way-valve.

12. A second chamber closing plate for an internal combustion engine (1), preferably according to one of claims 1 to 3, characterized in that the second chamber closing plate is connectable to a cylinder (11) such that it closes the cylinder (11) to form a second chamber (102).

13. A second chamber closing plate according to claim 12 characterized in that an outlet opening (113) is arranged in the second chamber closing plate, preferably an outlet opening (113) with a controllable chamber valve.

14. Kit of parts for retrofitting an internal combustion engine (1), comprising at least a second chamber closing plate according to any one of claims 12 to 13 and a controllable inlet valve.

15. The kit of claim 14 comprising a cylinder liner, preferably according to claim 8.

Drawing