KR102656099B1 - A large two-stroke uniflow scavenged engine and method for operating cylinders selectively according to the pre-mix process or the compression-ignition process - Google Patents

Abstract

In the dual fuel large two-stroke turbocharger Uniflow scavenge internal combustion engine and method of operating the engine, the engine includes a plurality of cylinders (1) and a piston (1) reciprocating between BDC and TDC in each cylinder (1). 10) and at least one fuel inlet valve 30 associated with the cylinder 1 for introducing first fuel during the stroke of the piston 10 from BDC to TDC, when the piston 10 is at or near TDC. At least one fuel injection valve (50) associated with at least one of the cylinders (1) for injecting the second fuel and a controller (60) configured to basically operate all of the plurality of cylinders (1) according to the premix and the controller 60 is configured to determine that the actual combustion conditions of the cylinder 1 operating according to the pre-mix process are such that there is an unacceptable risk of a pre-ignition event or misfire, and the controller 60 is configured to determine the pre-ignition event or misfire. If it is determined that there is an unacceptable risk for an ignition event or malfunction, at least one of the plurality of cylinders (1) is changed from operating according to the premix process to operating according to the compression ignition process.

Description

A LARGE TWO-STROKE UNIFLOW SCAVENGED ENGINE AND METHOD FOR OPERATING CYLINDERS SELECTIVELY ACCORDING TO THE PRE-MIX PROCESS OR THE COMPRESSION-IGNITION PROCESS}

The present disclosure relates to a dual fuel large two stroke Uniflow scavenge internal combustion engine, particularly a large two stroke Uniflow engine having a crosshead operating in an operating mode on primary fuel flowing from a fuel valve during the stroke of the piston from BDC to TDC. It concerns cabin internal combustion engines.

Large two-stroke turbocharged Uniflo scavenge internal combustion engines with crossheads are used, for example, to propulsion large oceangoing vessels or as the main power unit in power plants. This two-stroke diesel engine is not only larger but also constructed differently from other internal combustion engines. The exhaust valve weighs up to 400 kg, the piston diameter is up to 100 cm, and the maximum operating pressure in the combustion chamber is typically several hundred bar. The forces associated with these high pressure levels and piston sizes are enormous.

A large two-stroke turbocharged internal combustion engine, usually operated on gaseous fuel, fed by a fuel valve placed centrally along the length of the cylinder liner or placed in the cylinder cover, i.e. an engine that supplies gaseous fuel during the upstroke. Starting long before the exhaust valve closes, the piston starts from bottom dead center (BDC) to top dead center (TDC) and compresses the mixture of gaseous fuel and scavenge air in the combustion chamber (and thus operates according to the premixing process), and e.g. , igniting the compressed mixture at or near top dead center (TDC) by timed ignition means, such as pilot liquid or pilot gas injection.

This type of gas intake, using a fuel valve (gas intake valve) placed in the cylinder liner or cylinder cover, requires much lower fuel intake pressures (typically around 10 to 25 bar) because the gaseous fuel is injected when the compression pressure is relatively low. ) has the advantage of being able to use. When the piston is close to top dead center (TDC), that is, when the compression pressure in the combustion chamber is at or near maximum, it is low compared to large two-stroke turbocharged internal combustion engines that inject gaseous fuel. The latter type of engine requires fuel injection pressures that are much higher (typically over 300 bar) than the already high maximum combustion pressure. Fuel systems capable of handling gaseous fuels at these extremely high pressures are expensive and complex due to the volatile nature of the gaseous fuels and their behavior at high pressures, including diffusion into and through steel components of the fuel system.

Therefore, a fuel supply system for an engine that injects gaseous fuel during the compression stroke is significantly cheaper compared to an engine that injects gaseous fuel at high pressure when the piston is at or near TDC.

However, when injecting gaseous fuel during the compression stroke, the piston compresses the mixture of gaseous fuel and scavenge air, resulting in the risk of pre-ignition. The risk of pre-ignition can be reduced by operating with very lean mixtures, but lean mixtures increase the risk of misfire or partial misfire/delayed ignition, resulting in undesirable fuel slip.

The performance layout of the engine generally prevents pre-ignition while the engine is operating in steady state. This is achieved through careful selection of combustion chamber design, fuel injection timing and exhaust valve timing. When running according to the premix process, there is a narrow window between the risk of pre-ignition and misfire. Up to a certain average indicated pressure (lower than the level/maximum of a compression-ignition engine) the condition of the cylinder can be controlled accurately enough to avoid pre-ignition events and misfires. However, under transient load conditions the air-fuel ratio can change rapidly and lead to the risk of a pre-ignition event if the transient load condition is caused by an increase in engine load, and a risk of misfire if the transient condition is caused by a decrease in engine load. This can cause a cylinder condition. Additionally, external influences such as ambient temperature and pressure can also cause changes in air-fuel ratio and bulk compression temperature, altering combustion behavior. Tropical conditions, for example high engine loads, pose a risk of pre-ignition.

Pre-ignition can cause engine damage and misfire causes unburned fuel to slip into the atmosphere and should therefore be avoided.

Therefore, measures are needed to ensure that pre-ignition events and misfires can be prevented in engines operating according to the pre-mixing process.

DK201970370 discloses a large two-stroke turbocharged Uniflow scavenge gas operated internal combustion engine with a plurality of combustion chambers, at least one controller associated with the engine, and a controller configured to determine the average compressed air-fuel ratio and bulk compression temperature. At the start of combustion, the combustion chamber and controller are configured as follows:

- perform at least one compressed air-fuel ratio increase measurement if the determined or measured average compressed air-fuel ratio is below a lower compressed air-fuel ratio threshold, and

- perform at least one compressed air-fuel ratio reduction measurement when the determined or measured average compressed air-fuel ratio exceeds the upper compressed air-fuel ratio threshold,

- perform at least one bulk compression temperature increase measurement when the determined or measured bulk compression temperature is below a low bulk compression temperature threshold,

- Perform at least one bulk compression temperature reduction measurement when the determined or measured bulk compression temperature is higher than the upper bulk compression temperature threshold.

Patent Document 1: DK201970370

The goal is to provide an engine that overcomes or at least reduces the problems described above.

The above and other objects are achieved by the features of the independent claims. Additional embodiment forms are apparent from the dependent claims, description and drawings.

According to a first aspect, a dual fuel large two-stroke turbocharged Uniflo scavenge internal combustion engine is provided, the engine being in at least one operating mode configured to operate using a first fuel as a primary fuel, the engine Silver: A plurality of cylinders, a piston reciprocating between BDC (bottom dead center) and TDC (top dead center) in each cylinder, at least one fuel connected to the cylinder for receiving the first fuel during the piston's stroke from BDC to TDC. an inlet valve, at least one fuel injection valve associated with at least one of the cylinders for injecting secondary fuel when the piston is at or near TDC, and when operating in said at least one operating mode, configured to: A controller comprising:

- operating both said plurality of cylinders essentially according to a pre-mixing process and receiving said first fuel during the stroke of the piston from BDC to TDC;

- the controller is configured to determine that the actual combustion conditions in the cylinder operating according to the pre-mix process are such that there is an unacceptable risk of a pre-ignition event or misfire, and the controller is configured to determine the tolerance for a pre-ignition event or misfire for: If you decide there is a risk that you cannot:

changing at least one of the plurality of cylinders from operating according to a premix process to operating according to a compression ignition process by terminating the flow of said first fuel during the stroke of the piston from BDC to TDC; , and injecting said amount of second fuel into at least one of the associated cylinders when the piston is at or near TDC.

For cylinders operating according to the compression ignition process, the air-fuel ratio is much less important compared to cylinders operating according to the premix process, so by having one or more cylinders operating according to the compression ignition process, the operating conditions of the remaining cylinders operating according to the premix process Pre-ignition and/or misfire events can be prevented by adjusting .

The indicated mean effective pressure (MIP) is an imaginary pressure that, when acting on a piston, does the same work as the actual pressure in the operating cycle.

In a possible implementation form of the first aspect, the controller is configured to select the amount of second fuel to be injected into the at least one cylinder involved as follows:

The average indicated pressure of the remaining cylinders among the plurality of cylinders operating according to the pre-mix process is reduced if it is determined that there is a risk of towing, and the average indicated pressure of the remaining cylinders among the plurality of cylinders operating according to the pre-mix process is reduced to indicate the risk of misfire. If it is determined that there is, it increases.

Accordingly, the risk of pre-ignition events and/or misfire events can be effectively mitigated by adjusting the torque transmitted (MIP) by the cylinder or cylinders operating according to the compression ignition process in a manner that changes the operating conditions. With the remaining cylinders operating during the premix process, these conditions no longer pose an unacceptable risk for pre-ignition events or misfires. The inventors had the insight that this would be possible because cylinders operating according to the compression ignition process are insensitive to air-fuel ratio and are less sensitive to bulk compression temperature.

In a possible implementation form of the first aspect, the controller is configured to return from operating according to the post-compression ignition process to operating according to the pre-mixing process after a predetermined time range or engine speed. The operation of the cylinder is changed from operation according to the pre-mixing process to a compression ignition process.

In a possible implementation form of the first aspect, the controller is configured to monitor the air-fuel ratio and bulk compression temperature of the cylinder operating according to the pre-mixing process, and when these values are in an acceptable range, preferably in a given time range, compression ignition The operation of one or more cylinders operating according to the process is changed to a pre-mixing process.

In a possible implementation form of the first aspect, no or only a small amount of second fuel is injected as pilot fuel into the cylinder operated according to the premixing process.

In a possible implementation form of the first aspect, each cylinder is provided with a variable timing exhaust valve actuating system for actuating an exhaust valve centrally disposed on the cylinder cover, wherein the controller is configured to determine and control the opening and closing timing of the exhaust valve. It consists of:

timing the opening and closing of exhaust valves adapted to the pre-mix process for cylinders (1) of the plurality of cylinders operating according to the pre-mix process, and

and timing the opening and closing of exhaust valves adapted to the compression ignition process for cylinders of the plurality of cylinders operating according to the compression ignition process.

In a possible implementation of the first aspect, the controller is configured to determine and control the amount of first fuel entering the cylinder.

In a possible implementation of the first aspect, the controller is configured to determine or measure an air-fuel ratio for the cylinder, and is configured to determine an unacceptable risk of a misfire event when the air-fuel ratio exceeds a maximum air-fuel ratio threshold, and and configured to determine an unacceptable risk of a pre-ignition event when the ratio is below a minimum air-fuel ratio threshold.

In a possible implementation of the first aspect, the controller is configured to determine or measure the bulk compression temperature of the cylinder at the start of combustion, wherein the unacceptable risk of a misfire event is determined when the bulk compression temperature is below a minimum bulk compression temperature threshold. and configured to determine an unacceptable risk of a pre-ignition event when the bulk compression temperature is above the maximum bulk compression temperature threshold.

In a possible implementation of the first aspect, the controller includes or is connected to an air-fuel ratio observer for determining the instantaneous average air-fuel ratio of the cylinder.

In a possible implementation of the first aspect, the controller includes or is connected to a bulk compression temperature observer for determining an average instantaneous bulk compression temperature of the cylinder.

According to a second aspect, a method of operating a dual fuel large two-stroke turbocharged Uniflo scavenge internal combustion engine is provided, wherein the engine is configured to operate using a first fuel as the primary fuel in at least one operating mode. wherein the engine has a plurality of cylinders, a piston reciprocating between BBC and TDC in each cylinder, at least one fuel inlet valve associated with the cylinder for introducing first fuel during the stroke of the piston from BDC to TDC, and a piston at TDC. At least one fuel injection valve connected to at least one of the cylinders for injecting the second fuel when at or near TDC;

The above method is:

- operating both said plurality of cylinders essentially according to a pre-mixing process and receiving said first fuel during the stroke of the piston from BDC to TDC;

- determine whether the actual combustion conditions in the cylinder operating according to the premix process are such that there is an unacceptable risk for a pre-ignition event or misfire, and whether the unacceptable risk for a pre-ignition event or misfire is: When decided:

changing at least one of the plurality of cylinders from operating according to a premix process to operating according to a compression ignition process by terminating at least one of the plurality of cylinders during the stroke of the piston from BDC to TDC, and when the piston is at or near TDC; and injecting said amount of second fuel into at least one of the relevant cylinders when present.

In a possible implementation form of the second aspect, the method includes selecting the amount of second fuel to be injected into the at least one associated cylinder as follows:

The average indicated pressure of the remaining cylinders among the plurality of cylinders operating according to the premix process is reduced when the risk of preignition is determined,

The average indicated pressure of the remaining cylinders of the plurality of cylinders operating according to the premix process is increased when the risk of misfire is determined.

In a possible implementation form of the second aspect, the method comprises at least one cylinder operating according to the compression ignition process when a predetermined time range or engine speed has elapsed since the change from operation according to the pre-mixing process to operation of the corresponding cylinder in the compression ignition process. and returning it to operating condition according to the pre-mixing process.

In a possible implementation form of the second aspect, the method comprises monitoring the air-fuel ratio and bulk compression temperature of a cylinder operating according to a premix process, when these values are preferably in an acceptable range for a given time span. and changing the operation of one or more cylinders operating according to a compression ignition process to a premix process.

In a possible implementation form of the second aspect, the method comprises not injecting the second fuel as pilot fuel or injecting only a small amount of the second fuel into the cylinder operated according to the pre-mixing process.

In a possible implementation of the second aspect, each cylinder is provided with a variable timing exhaust valve disposed at the center of the cylinder cover, the method comprising:

timing the opening and closing of exhaust valves suitable for the premix process for cylinders of the plurality of cylinders operated according to the premix process, and

It includes timing the opening and closing of an exhaust valve suitable for the compression ignition process for cylinder 1 among the plurality of cylinders operating according to the compression ignition process.

These and other aspects will become apparent from the example(s) described below.

In the following detailed portions of the present disclosure, aspects, embodiments and implementations will be described in more detail with reference to example embodiments shown in the drawings, wherein:
1 is a front view of a large two-stroke diesel engine according to an embodiment of the present invention,
Figure 2 is a side view of the large two-stroke engine of Figure 1;
Figure 3 is a first schematic diagram of the large two-stroke engine according to Figure 1;
Figure 4 is a cross-sectional view of the cylinder frame and cylinder liner of the engine of Figure 1, fitted with cylinder covers and exhaust valves, with the pistons shown using interrupted lines at both TDC and BDC;
Figure 5 is a second schematic diagram of the engine of Figure 1;
Figure 6 is a schematic diagram of a compression temperature observer and a compression air-fuel ratio observer;
Figure 7 is a diagram showing compressed air-fuel ratio on the ordinate and bulk cylinder temperature on the abscissa, with the region showing optimal combustion conditions surrounded by a less optimal action region where action must be taken to return to the safe region, surrounded by critical regions to be avoided. It is an area,
Figure 8 is a graph showing cylinder pressure versus crank angle for various combustion conditions including misfire, normal combustion, and pre-ignition (knocking);
Figure 9 is a flowchart showing a process for controlling combustion conditions in the large two-stroke engine of Figure 1;
10 to 15 are diagrams for explaining the operation of individual cylinders in various situations.

In the following detailed description, the internal combustion engine will be described with reference to a large two-stroke, low-speed turbocharged, uniflow scavenge internal combustion crosshead engine in an exemplary embodiment. 1, 2 and 3 show an embodiment of a large, low-speed turbocharged two-stroke diesel engine with a crankshaft (8) and a crosshead (9). 1 and 2 are front and side views, respectively. Figure 3 is a schematic diagram of the large, low-speed turbocharged two-stroke internal combustion engine of Figures 1 and 2; 1 and 2 with intake and exhaust systems. In this exemplary embodiment, the engine has five cylinders in a row. Large, low-speed turbocharged two-stroke Uniflow scavenge internal combustion engines typically have between four and fourteen cylinders in a row, carried by an engine frame (11). The engine operates, for example, as the main engine of a marine vessel or as a generator in a power plant. The total power output of the engine may range from 1,000 to 110,000 kW, for example.

In this exemplary embodiment the engine is a two-stroke uniflow scavenge having a scavenging port 18 in the lower region of the cylinder liner 1 and a central exhaust valve 4 in the cylinder cover 22 on top of the cylinder liner 1. It's a G engine. Scavenging air passes from the scavenging air receiver (2) through the scavenging port (18) of the individual cylinder liner (1) when the piston (10) is below the scavenging port (18). During basic operation on a first fuel (usually a gaseous fuel, e.g. natural gas, petroleum gas or ammonia), the first fuel causes the piston to move upward and the piston to pass through the intake valve 30 (gas intake valve). It is previously sucked in from the gaseous fuel injection valve 30 under the control of the electronic controller 60. The first fuel is introduced at a relatively low pressure, less than 30 bar, preferably less than 25 bar, more preferably less than 20 bar. The fuel valves 30 are preferably evenly distributed around the circumference of the cylinder liner and are placed somewhere in the central region of the length of the cylinder liner 1. Accordingly, the introduction of the first fuel occurs when the compression pressure is relatively low, i.e. much lower than the compression pressure when the piston 10 reaches TDC, thus allowing introduction at a relatively low pressure. The first fuel is generally a gaseous fuel that is supplied to the fuel inlet valve and enters the cylinder in gaseous form (gas phase), for example natural gas or petroleum gas. However, the first fuel may also be a liquid fuel such as ammonia.

The piston 10 of the cylinder liner 1 compresses the mixture of first fuel and scavenge air, compression taking place at or near TDC and ignition via, for example, a dedicated pilot liquid valve (not shown) or preferably Upon injection of pilot liquid (or any other suitable ignition liquid) from the fuel injection valve 50 arranged on the cylinder cover 22, combustion follows and exhaust gas is produced. Ignition may also be initiated using an alternative form of ignition system, such as a prechamber (not shown), laser ignition (not shown), or glow plug (not shown), instead of or in addition to the pilot liquid valve.

When the exhaust valve (4) opens, the exhaust gas flows through the exhaust duct connected to the cylinder (1) to the exhaust gas receiver (3) and then through the first exhaust conduit (19) to the turbine (6) of the turbocharger (5). It flows. through the economizer 20 to the outlet 21 and remotely through a second exhaust conduit to the atmosphere. Via the shaft the turbine (6) drives the compressor (7), from which fresh air is supplied through the air inlet (12). The compressor (7) delivers compressed scavenge air to the scavenge air conduit (13) leading to the scavenge air receiver (2). The scavenge air in the conduit 13 passes through an intercooler 14 to cool the scavenge air.

The cooled scavenge air is supplied by an electric motor ( It passes through the auxiliary blower (16) driven by 17). At higher engine loads the turbocharger compressor (7) delivers sufficient compressed scavenge air and the auxiliary blower (16) is bypassed via the check valve (15).

Figure 4 shows a cylinder liner 1 generally designated for large two-stroke crosshead engines. Depending on the engine size, cylinder liners 1 can be manufactured in various sizes, with cylinder bores typically ranging from 250 mm to 1000 mm and typical lengths ranging from 1000 mm to 4500 mm.

In Figure 4 the cylinder liner 1 is shown mounted on the cylinder frame 23 and the cylinder cover 22 is disposed on top of the cylinder liner 1 with an airtight interface therebetween. In Figure 4 the piston 10 is shown schematically as a line interrupted at both bottom dead center (BDC) and top dead center (TDC), but of course these two positions do not occur simultaneously and occur in 180 degrees of rotation of the crankshaft 8. It is clear that they are separated by The cylinder liner (1) is provided with a cylinder lubrication hole (25) and a cylinder lubrication line (24) which provide a supply of cylinder lubricant when the piston (10) passes through the lubrication line (24), which is then connected to the piston ring (not shown). ) distributes the cylinder lubricant onto the operating surfaces of cylinder liner 1.

A pilot valve (typically more than one per cylinder) or pre-chamber with a pilot valve is mounted on the cylinder cover 22 and connected to a source of pilot liquid or gas (not shown). The timing of pilot liquid injection is controlled by the electronic control unit 60.

The fuel inlet valve 30 is installed in the cylinder liner 1 (or cylinder cover 22), and its nozzle is maintained substantially flush with the inner surface of the cylinder liner 1 and is positioned at the rear end of the fuel valve 30. It protrudes from the outer wall. Typically, one or two, possibly three or four fuel valves 30 distributed circumferentially (preferably evenly distributed circumferentially) around the cylinder liner 1 are provided in each cylinder. Provided in liner (1). The fuel valve 30 is located substantially centrally along the length of the cylinder liner 1 in one embodiment. The fuel injection valve 50 for injecting the second fuel at high pressure is installed on the cylinder cover 22, and generally two or three fuel injection valves 50 per cylinder 1 are installed on the cylinder cover 22. arranged so that the nozzle of the fuel valve 50 protrudes slightly into the combustion chamber. The second fuel may be a liquid fuel. The second fuel may be one or more of fuel oil, heavy oil, and marine diesel.

4 also shows a source of pressurized first fuel 44 connected to the inlet of each fuel inlet valve 30 and a source of pressurized second fuel 41 connected to the inlet of each fuel injection valve 50. A first fuel supply system including a second fuel supply system is schematically shown.

Figure 5 shows a schematic diagram of an engine similar to Figure 2, but describes the gas exchange infrastructure of the engine in more detail. Ambient air is sucked in at ambient pressure and temperature and delivered to the compressor (7) of the turbocharger (5) through the air inlet (12). Compressed scavenging air from compressor 7 is conveyed through air conduit 32 to distribution point 28.

The distribution point 28 allows scavenge air to branch off via the hot cylinder bypass conduit 29 to the turbine connection 32 of the first exhaust conduit 19. Flow through the hot cylinder bypass conduit (29) is regulated by the hot cylinder bypass control valve (31). The hot cylinder bypass control valve 31 is electronically controlled by a controller 60. The effect of opening the hot cylinder bypass conduit 29 or reducing the throttling of the control valve 31 in the hot cylinder bypass is an increase in the air-fuel ratio and an increase in the bulk compression temperature and vice versa.

The air conduit 13 further includes a first scavenge air control valve 33 upstream of the intercooler 14. The second scavenging control valve 34 is arranged downstream of the intercooler 14. The air conduit (13) continues into the scavenge air receiver (2). The auxiliary blower 16 branches off from the intercooler 14.

A cold cylinder bypass conduit (35) connects the scavenge air receiver (2) to the turbine connection (32) of the first exhaust conduit (19). Flow through cylinder bypass (35) is regulated by a cold cylinder bypass control valve (36). The effect of the cold cylinder bypass control valve 36 opening the cold cylinder bypass 35 or reducing the throttling of the cold cylinder bypass valve 36 is an increase in the bulk compression temperature.

A cold scavenge bypass conduit 37 allows scavenge air to escape from the scavenge air receiver 26 from the environment. Flow through the cold scavenge bypass conduit (37) is controlled by a cold scavenge bypass control valve (38). The cold scavenge bypass control valve 38 is electronically controlled by a controller 60. The cold scavenge bypass control valve 38 reduces the scavenge air pressure and reduces the air-fuel ratio, and vice versa. The cooled scavenge bypass conduit 37 need not branch from the scavenge air receiver 2, but may branch from the air conduit 13 at any location downstream of the intercooler 14.

The exhaust gas recirculation conduit 42 connects the exhaust gas receiver 3 to the scavenge receiver 2 and connects the exhaust gas recirculation control valve 45, the exhaust gas recirculation cooler 44 and the exhaust gas recirculation blower 43. Includes. The exhaust gas recirculation blower 43 and the exhaust gas recirculation control valve 45 are both used to regulate the flow through the exhaust gas recirculation conduit 42 under the electronic control of the controller 60. Under normal operating conditions, the exhaust gas recirculation blower 43 is activated because the pressure in the exhaust gas receiver 42 is generally lower than the pressure in the scavenge receiver 2 (therefore, when the exhaust gas recirculation blower 43 is not operating Exhaust gas recirculation control valve (45) must be closed). The exhaust gas recirculation conduit 42 does not need to be connected from the exhaust gas receiver 3 but may be connected at any point to the first exhaust conduit 19 and does not need to be connected to the scavenge air receiver 2 and can be connected downstream of the intercooler 14. It is well connected to any location in the air conduit 13.

Activating or increasing the speed of the exhaust gas recirculation blower 43 in the exhaust gas recirculation conduit 42 reduces the compressed air-fuel ratio and slightly reduces the bulk compression temperature, and vice versa.

The exhaust gas bypass 39 branches off from the exhaust gas receiver 3 or the first exhaust conduit 19 and connects to the atmosphere 27 at a given back pressure 27 . Exhaust gas bypass control valve 40 regulates flow through electronic control of exhaust gas bypass conduit 39 and controller 60.

Opening the exhaust gas bypass control valve 40 or reducing the throttling of the exhaust gas bypass control valve 40 reduces the compressed air-fuel ratio of the cylinder and vice versa.

In engines provided with a selective catalytic receiver (SVR) reactor and a reactor bypass valve (RVB), the turbine (6) of the turbocharger (5) from the scavenge air receiver (3) passes through the SCR reactor through electronic control of the controller (60). Adjust the fraction of flow to.

All the above-mentioned components controlled by the controller 60 are connected to these components by signal lines indicated as interrupted lines in FIG. 5 .

Figure 6 shows the air-fuel ratio observer 46 and the bulk compression temperature observer 47.

The air-fuel ratio observer 46 is a computer-implemented algorithm that holds information about scavenge air pressure, exhaust valve closing timing, cylinder geometry, stoichiometric air-fuel ratio, and injected gas volume. Compressed air-fuel ratio observer 46 may be part of controller 60 or may be a separate computer or controller. The compressed air-fuel ratio observer 46 provides an output that is an estimate of the compressed air-fuel ratio of the (complete) compressed air-fuel ratio mixture (when the piston 10 is at TDC) and sends this to the controller 60. The estimate is based on the ratio of the fresh air mass captured in the combustion chamber when the exhaust valve 4 lands on its seat divided by the fresh air mass required for stoichiometric combustion of the total injected gas mass.

Bulk compression temperature observer 47 is a computer implemented algorithm that holds information about scavenge pressure, scavenge air temperature, exhaust valve closing timing and crankshaft speed. Bulk compression temperature observer 47 may be part of controller 60 or may be a separate computer or controller. The bulk compression temperature observer 47 provides an output that is an estimate of the bulk compression temperature of the combustion chamber, Tcomp(Tc), in the time window from the start of gas injection to the pilot injection, and the compression air-fuel ratio observer 47 provides an estimate to the controller 60. send to In one embodiment, the Tcomp estimate refers to piston 10 at TDC.

7 is a graph showing bulk compression temperature (Tcomp) versus air-fuel ratio (λ). The steady-state basic zone 51 has a lower air-fuel ratio threshold (λ-lower), an upper air-fuel ratio threshold (λ-upper), a lower bulk compression temperature threshold (Tc-lower), and an upper bulk compression temperature threshold (Tc-upper). ) is within the boundary defined by . In this steady-state basic zone 51, the controller 60 provides each cylinder 1 individually with the amount of first fuel required for the current engine load and the controller 60 takes no action to change the bulk compression temperature. Control for each cylinder. For each cylinder, the air-fuel ratio is at a level that is a function of engine operating conditions with a safe distance in the form of a margin from known undesirable combustion conditions at which partial misfire, misfire, and/or pre-ignition are likely to occur. Occurs when it exceeds

If the combustion conditions in cylinder 1 threaten to leave the normal running zone 51 and enter the operating zone 52, the controller 60 will take action to prevent this from happening.

Here, the controller 60 is configured individually for each cylinder as follows.

- perform at least one compressed air-fuel ratio increase measurement (CAERIM) when the determined or measured average compressed air-fuel ratio is below a lower compressed air-fuel ratio threshold,

- perform at least one compressed air-fuel ratio reduction measurement (AERDM) when the determined or measured average compressed air-fuel ratio exceeds the upper compressed air-fuel ratio threshold, and

- perform at least one bulk compression temperature increase measurement (BCTIM) when the determined or measured bulk compression temperature is below the low bulk compression temperature threshold,

- Perform at least one bulk compression temperature reduction measurement (BCTDM) when the determined or measured bulk compression temperature is higher than the upper bulk compression temperature threshold.

By performing these actions, the controller 60 maintains the condition of each cylinder liner 1 inside the normal running area 51 and, at least temporarily, moves the condition outside the normal running area 51 to the operating area. Allow entry into (52). The action zone 52 is surrounded by a critical zone 53 where pre-ignition and/or misfire events are highly likely to occur.

The boundaries for zones 51, 52, and 53 may be defined by upper and lower thresholds for the bulk compression temperature and upper and lower limits for the compression air-fuel ratio. These thresholds can be determined for a particular engine empirically through trial and error or computer simulation of the engine cycle.

If the observer indicates that both the compressed air-fuel ratio and the bulk compression temperature are outside the normal operating region 51, the controller 60 controls the compression ratio for each cylinder to move the condition of the cylinder liner 1 back to the normal operating region 51. Two steps are taken to individually adjust the air-fuel ratio and bulk compression temperature.

Adjust the exhaust gas bypass control valve (40) (move the exhaust gas bypass control valve (40) to a more open position) to open the exhaust gas bypass (EGB) conduit (39) (from the TC turbine inlet to the turbine outlet or surrounding opening the air pressure and removing trapped air masses from the combustion chamber. As a result, this measure is suitable for reducing the compressed air-fuel ratio with only a minor effect on the compressed bulk temperature. If the engine has more turbochargers, a single EGB can still be used in the exhaust gas receiver as long as the location is chosen according to the different potential mixing points in the different flows to the exhaust gas receiver.

Opening the hot cylinder bypass control valve 31 (flow from TC compressor outlet to TC turbine inlet) increases the compressed air-fuel ratio and bulk compression temperature in the combustion chamber.

Opening the scavenge bypass control valve (38) creates flow from the scavenge air receiver (2) to or around the compressor inlet and its opening has a qualitative effect similar to that of an exhaust gas bypass on the compressed air-fuel ratio, but the scavenging process (and therefore the combustion chamber effect on the bulk compression temperature) has other effects. The effect of opening the scavenge bypass control valve 38 on combustion chamber conditions is faster compared to exhaust gas bypass.

Opening the cold cylinder bypass valve 36 increases the flow from the scavenge air receiver to the TC turbine inlet and increases the bulk compression temperature, but has very little effect on the compressed air-fuel ratio.

Exhaust valve closing timing determines the ratio between compression and scavenge pressures in the combustion chamber. Varying timing has a significant impact on both the combustion chamber's compressed air-fuel ratio and bulk compression temperature.

Exhaust valve opening timing affects the first stage of the combustion chamber scavenge process. Changing timing affects engine efficiency and scavenge processes. As the scavenging process changes, the resulting bulk temperature also changes. If the exhaust valve (4) is opened very early, there is no flow to the scavenge air receiver (2) when the piston (10) subsequently opens the scavenge port (18). If the exhaust valve (4) opens very late, then there is a large flow into the scavenging receiver (2). The piston 10 then opens the scavenge port 18. This action changes the scavenging process and therefore the fraction of 'dirty hot' gases from the previous combustion joining the next compression stroke.

Therefore, if the exhaust valve (4) is opened later, more “dirty hot” gases are generated from the previous combustion, which reduces the compressed air-fuel ratio and increases the bulk compression temperature. Opening the exhaust valve 4 very early will reduce the "dirty hot" gases from previous combustion and thus increase the compressed air-fuel ratio at the bulk compression temperature. Increasing compression by closing the exhaust valve (4) earlier means less gas escapes through the exhaust valve (4) and thus more gas is trapped in the combustion chamber. This increases the air-fuel ratio. Additionally, increasing compression leads to more compression work performed by the piston 10 on the gases in the combustion chamber. This leads to higher gas temperatures in the combustion chamber.

Increasing the exhaust gas recirculation flow by activating the exhaust gas recirculation blower (43) or increasing the speed of the exhaust gas recirculation blower (43) causes more exhaust gas recirculation flow from the exhaust gas receiver (3) to the turbocharger compressor outlet or scavenge air receiver (2). A lot of exhaust gases flow. This will reduce the compressed air-fuel ratio.

Increasing the speed of the auxiliary blower 16 will slightly increase the compressed air-fuel ratio.

In the case of water injection engines, injecting water into the combustion chamber during compression lowers the bulk compression temperature.

Scavenge Air Cooler Bypass (not shown): Bypassing the intercooler (14) significantly increases the bulk compression temperature of the combustion chamber with a negligible effect on the compressed air-fuel ratio.

In the case of engines provided with a variable geometry turbine 6, the effect of reducing the turbine flow area is an increase in scavenge pressure and therefore an increase in the mass of air trapped in the combustion chamber. As a result, this measure is suitable for reducing the compressed air-fuel ratio with only a minor effect on the compressed bulk temperature.

In the case of engines with turbocharger auxiliary devices, increasing the speed of the turbocharger (5) by increasing the auxiliary device increases the compression air-fuel ratio and has a slight effect on the compression temperature.

Another method is to change the ratio between gaseous fuel and liquid fuel (e.g. diesel oil or marine diesel). Reducing the gas-fuel ratio of the total injected fuel energy increases the compressed air-fuel ratio during compression. The liquid fuel ratio is thereby increased to maintain crankshaft torque.

In the case of engines in which a heat exchanger is installed in the exhaust gas receiver (or if there is a heat exchanger that receives part of the exhaust gases), increasing the proportion of exhaust gases passing through the heat exchanger, i.e. extracting more heat from the exhaust gases, increases the scavenging air pressure. reduction, and therefore reduction of the trapped air mass in the combustion chamber. As a result, this measure is suitable for reducing the compressed air-fuel ratio with only a minor effect on the compressed bulk temperature. Heat exchangers can be used for steam production.

For engines with hot scavenge bypass, opening the hot scavenge bypass control valve establishes or increases flow from the compressor outlet to the ambient or compressor inlet, significantly reducing the scavenge air pressure and thus trapping the combustion chamber. The accumulated air mass decreases. As a result, this measure is suitable for reducing the compressed air-fuel ratio.

In one embodiment, the lower compressed air-fuel ratio threshold, upper compressed air-fuel ratio threshold, lower bulk compression temperature threshold, and upper bulk compression temperature threshold are engine operating condition dependent parameters. Engine operating conditions are determined by parameters such as engine load, ambient temperature, ambient humidity, engine speed, etc. Values for these operating condition dependent parameters are available to the controller 60, for example via lookup tables or algorithms or a combination thereof.

If the above measures are not sufficient to maintain the combustion process in the operating zone (52), additional measures are taken by the controller (60) to prevent the process from moving to the critical zone (53). These additional measures are taken before or when conditions in the combustion chamber move from the operating zone 52 to the critical zone 53 surrounding the operating zone 52 . Accordingly, the controller 60 is configured to change at least one of the cylinders 1 from a premix operation to a compression ignition operation, the amount of second fuel being injected at or near TDC in the cylinder 1 operated with compression ignition. By selecting , the remaining cylinders (1) still operating with the pre-mixing process are configured to help move away from the critical area (53). The secondary fuel is a fuel that can be injected relatively easily, for example at TDC (a pressure of at least 300 bar is usually required), i.e. at the very high pressures required for injecting in liquid fuels. Examples of such liquid fuels are fuel oil, heavy oil, methanol, ethanol, dimethyl ether (DME), and ammonia (water may be added to these fuels). In addition, the controller 60 changes the cylinder or plurality of cylinders 1 according to the compression ignition process, so that the torque (MIP) to be transmitted by the remaining cylinders operating according to the pre-mixing process is reduced. By adjusting the second fuel injection amount to the operating cylinder 1 according to , it decreases when the risk of a pre-ignition event is detected and increases when the risk of a misfire event is detected. By operating the cylinders operating according to the compression ignition process with a relatively small amount of secondary fuel, the torque (MIP) of the remaining cylinders operating according to the pre-mixing process is increased, so that these cylinders produce a relatively small amount of torque (MIP). be provided. By operating the cylinders operating according to the compression ignition process with a relatively high amount of secondary fuel, the torque (MIP) of the remaining cylinders operating according to the pre-mixing process is reduced, so that these cylinders produce a relatively high amount of torque (MIP). be provided.

The controller 60 is configured to minimize the constraints, i.e. the measures mentioned above in order to move the engine back to operating conditions within the normal zone 51 and minimize the operation of the cylinder 1 according to the compression ignition process. Accordingly, the controller is configured to terminate all the above-mentioned actions when the state of the combustion chamber returns to the normal operating region.

Figure 8 is a flowchart showing the operation process of the engine according to the configuration of the controller 60 described above.

After the start of the process, the controller 60 essentially starts all cylinders 1 into operation in the premix process, a situation illustrated in Figure 10 where all cylinders are operating in the premix process. Assuming conditions are optimal, the air-fuel ratio for all cylinders (1) in the allowable range between λ-min and λ-max is such that the torque (MIP) delivered by each cylinder (1) is is substantially equal to the average torque (this is the situation shown in Figure 10). Note that in one embodiment, each cylinder (1) is individually controlled to optimize the operation of the associated cylinder (1), which may result in slight variations in the torque delivered by each individual cylinder (1). do.

Next, the controller 60 checks whether the compressed air-fuel ratio λ is below the lower threshold λ-lower, preferably individually for each cylinder. If the response is no, the controller 60 checks whether the compressed air-fuel ratio upper limit threshold (λ-upper) is exceeded, and if the response is yes, the controller 60 takes action to increase the compressed air-fuel ratio from one of the aforementioned actions. Next, the controller 60 determines whether the compressed air-fuel ratio exceeds the maximum (λ-max) threshold. If the answer is no, the controller moves to check if the compression ratio upper threshold (λ-upper) has been exceeded, and if the answer is yes (a situation where there is a risk of pre-ignition as shown in Figure 11), the controller 60 moves to check if the compression ratio upper limit threshold (λ-upper) has been exceeded. (1) from running in a premix process to a compression ignition process, and also of a second fuel injected at or near TDC to increase the MIP in one or more cylinders (1) operating in conjunction with the compression ignition process. adjust the amount, thereby reducing the MIP of the remaining cylinders (1) operating according to the premixing process, thereby increasing the air-fuel ratio of the cylinders (1) operating according to the premixing process, and thus no longer In (1), there is no risk of pre-ignition. This is the situation shown in Figure 12. Next, controller 60 determines whether the air-fuel ratio is between the lower and upper thresholds and the bulk combustion temperature is between the upper and lower thresholds for cylinder 1 operating in the premix process. If the answer is no, the process returns to the beginning, and if the answer is yes, one or more of the other cylinders (1) change from operating in the compression ignition process to the premix process, further reducing the torque (MIP). The cylinder operates in a pre-mixing process and then the process returns to the beginning.

If the air-fuel ratio is determined to be higher than the lower threshold (λ-lower), the controller 60 checks whether the compressed air-fuel ratio is higher than the upper threshold (λ-upper). If the answer is no, the controller moves to check if the lower bulk compression temperature threshold (Tc-lower) has been exceeded, and if the answer is yes, then the controller 60 takes action to reduce the compressed air-fuel ratio in one of the aforementioned actions. Next, the controller 60 checks whether the compressed air-fuel ratio is greater than the maximum threshold (λ-max). If the answer is no the controller moves to check if the lower bulk compression temperature threshold (Tc-lower) has been exceeded, if the answer is yes (this is the situation illustrated in Figure 13) the controller 60 moves to change one or pre-mix. Reduce the MIP of one or more cylinders (1) in operation by using more cylinders (1) from operating in the process to the compression ignition process and adjusting the amount of secondary fuel injected at or near TDC. The compression ignition process increases the MIP of the remaining cylinders (1) operating according to the premixing process and thus reduces the air-fuel ratio of the cylinder (1) operating according to the premixing process, thereby reducing the risk of misfire. This is the situation shown in Figure 14. Next, controller 60 determines whether the air-fuel ratio is between the lower and upper thresholds and the bulk combustion temperature is between the upper and lower thresholds for cylinder 1 operating in the premix process. If the answer is no, the process returns to the start, if the answer is yes, one or more cylinders (1) are changed from the compression ignition process to the premix process and then the process returns to the start.

If the air-fuel ratio is not determined to be above the upper threshold (λ-upper), the controller 60 checks whether the bulk compression temperature is below the lower threshold (Tc-lower). If the answer is no, the controller 60 moves to the next step to check whether the bulk compression temperature is above the upper limit (Tc-upper), and if yes, the controller 60 takes action to increase the bulk compression temperature. Afterwards, the controller 60 checks whether the bulk compression temperature is below the minimum threshold value (Tc-min), and if the response is no, the process 60 checks whether the bulk compression temperature is above the maximum threshold value (Tc-max). Go to the next step. And if the answer is yes, controller 60 changes one or more cylinders 1 from running in the premix process to compression ignition process and adjusts the amount of secondary fuel injected at or near TDC. It operates according to a pre-mixing process to increase the bulk combustion temperature of the cylinders by reducing the MIP of one or more cylinders (1) operating according to the compression ignition process and thereby increasing the MIP of the remaining cylinders (1) operating according to the pre-mixing process. . Next, controller 60 determines whether the air-fuel ratio is between the lower and upper thresholds and the bulk combustion temperature is between the upper and lower thresholds for cylinder 1 operating in the premix process. If the answer is no, the process returns to the start, if the answer is yes, one or more cylinders (1) are changed from the compression ignition process to the premix process and then the process returns to the start.

If the bulk compression temperature is not determined to be below the lower threshold (Tc-lower), the controller 60 checks whether the upper bulk compression temperature threshold (Tc-upper) is exceeded and if the answer is no, the controller 60 determines whether the Go back to checking if the air-fuel ratio is below the lower threshold, and if the answer is yes, the controller 60 takes bulk temperature reduction action from the actions mentioned above. Next, the controller 60 checks if the bulk compression temperature is above the maximum threshold (Tc-max), and if the answer is "no", the controller 60 moves back to checking if the compressed air-fuel ratio is below the lower limit, and , and if the answer is yes, then the controller 60 changes one or more cylinders 1 from the premix process to the compression ignition process, at TDC or Adjusting the amount of secondary fuel injected near TDC thereby reducing the MIP in the remaining cylinders operating according to the premix process (1) and reducing the risk of pre-ignition events in the cylinders operating according to the premix process (1) ) to reduce the bulk compression temperature.

In one embodiment, controller 60 is provided with an algorithm, lookup table, or other information to determine which of the available actions to increase or decrease the air-fuel ratio is the most appropriate action under the current operating conditions of the engine.

In one embodiment, the values for the upper and lower air-fuel ratio thresholds and the minimum and maximum air-fuel ratio thresholds are determined from test runs of the engine in a test or computer simulation. The values for the upper and lower thresholds for the air-fuel ratio and the minimum and maximum thresholds for the fuel-to-fuel ratio are not necessarily constant values and generally depend on other parameters such as engine load and speed, ambient conditions, etc. The controller 60 stores these values in a lookup table, etc. or uses an algorithm to determine accurate values for actual conditions.

In one embodiment, the values for the upper and lower thresholds for bulk compression temperature and the minimum and maximum thresholds for bulk compression temperature are determined from test runs of the engine in a test or computer simulation. The upper and lower thresholds of the bulk compression temperature and the minimum and maximum thresholds of the bulk compression temperature are not necessarily constant values and generally depend on other parameters such as engine load and speed, ambient conditions, etc. The controller 60 stores these values in a lookup table, etc. or uses an algorithm to determine the correct value for the actual condition.

The safe area 51, the operating area 52 and the critical area 53 are schematically shown in Figure 7, and these areas do not necessarily have a rounded rectangular shape, and Figure 7 is only an example. In practice, the working area 52 is always located inside the critical area 53 and the safe area 51 is always located inside the working area 52, but the outline shape of these areas 51,52 is an arbitrary shape of a closed line. This may vary depending on the design and characteristics of the engine.

In another embodiment, the controller determines the need to change one or more of the plurality of cylinders (1) from operating in premix operation to compression ignition operation based on the cylinder pressure curve. Figure 8 is a graph showing examples of pressure curves (lowest peak curve) when delayed ignition/misfire occurs, normal combustion curves (middle peak curve), and curves where pre-ignition/knocking occurs. These curves are examples and in particular the delayed ignition/misfire curves and the pre-ignition/knocking curves (the curves with the highest peaks) may differ significantly from the examples shown.

In this embodiment, controller 60 detects the occurrence of undesirable combustion events, such as misfires and/or pre-ignition events, by analyzing the cylinder pressure curve and uses this to determine whether a pre-ignition or misfire event has occurred. It is constructed based on information.

When the controller 60 detects a pre-ignition event, the controller 60 changes one or more cylinders 1 from operation according to the pre-mix process to the compression ignition process and reconnects the cylinders 1 still operating in the pre-mix process. adjusting the amount of secondary fuel injected into the cylinder (1) operating according to the compression ignition process in order to reduce the torque (MIP) that must be transmitted by Prevent ignition events.

When the controller 60 detects a misfire or delayed ignition event, the controller 60 changes one or more cylinders 1 from operation according to the premix process to the compression ignition process and cylinders 1 operated according to the compression ignition process. By adjusting the amount of secondary fuel injected to increase the torque (MIP) that must be transmitted by the cylinder (1) still operating in the premix process, and thereby delay in the cylinder (1) operating according to the premix process Prevents ignition/misfire events.

In one embodiment, the controller 60 switches the operation of the cylinder 1 operating according to the compression ignition process to a premix process after a predetermined time range (or engine speed) for operating the cylinder 1 in the compression ignition process. It is configured to be reversed.

In another embodiment, the controller 60 is configured to monitor the air-fuel ratio and bulk compression temperature of the cylinder 1 operating according to the pre-mix process, such that these values are for example TC-lower limit and TC-upper limit, preferably During a given period of time between the λ-lower limit and the λ-upper limit, the operation of one or more cylinders (1) operating according to the compression ignition process is changed back to the pre-mixing process.

In one embodiment, in order to significantly influence the operating conditions (as air-fuel ratio and/or bulk compression temperature) of the remaining cylinders 1 operating according to the premix process, the controller 60 controls, for example, seven or more cylinders. It is configured to change the operation of at least two cylinders (1) from premix operation to compression ignition operation or vice versa for an engine with a plurality of cylinders (1) in an engine having a plurality of cylinders (1).

Generally, the controller 60 is configured to minimize operation of the cylinder during the compression ignition process to minimize use of the secondary fuel since minimizing the use of the secondary fuel will generally minimize emissions.

Generally, the controller 60 is configured to minimize operation of the cylinder during the compression ignition process to minimize use of the secondary fuel since minimizing the use of the secondary fuel will generally minimize emissions.

Various aspects and implementations have been described in connection with the various embodiments herein. However, other modifications to the disclosed embodiments will be understood by those skilled in the art in practicing the claimed subject matter from a study of the drawings, disclosure, and appended claims. may be affected. In a claim, the word "comprising" does not exclude another element or step, and the indefinite article "a" or "an" does not exclude plurality. A single processor, controller, or other device may perform the functions of several items recited in the claims. The fact that certain measures are recited in different dependent claims does not indicate that a combination of them cannot be used to advantage. Reference signs used in the claims should not be construed as limiting the scope.

Claims (16)

A dual fuel large two stroke turbocharged Uniflow scavenge internal combustion engine, wherein the engine is in at least one operating mode configured to operate using a primary fuel as a primary fuel, wherein the engine:
- plural cylinders (1),
- a piston (10) reciprocating between BDC and TDC in each cylinder (1),
- at least one fuel inlet valve (30) associated with at least one of said plurality of cylinders (1) for introducing first fuel during the stroke of the piston (10) from BDC to TDC,
- at least one fuel injection valve (50) associated with at least one of said plurality of cylinders (1) for injecting secondary fuel when the piston (10) is at or near TDC, and
- when running in said at least one operating mode, comprising a controller (60) configured to:
- basically operating all of said plurality of cylinders (1) according to a pre-mixing process and receiving said first fuel during the piston (10) stroke from BDC to TDC,
- the controller (60) is configured to determine whether the actual combustion conditions of the cylinder (1) operating according to the pre-mixing process present an unacceptable risk of a pre-ignition event or misfire,
The controller 60:
If the controller 60 determines that there is an unacceptable risk for a pre-ignition event or misfire,
In operating at least one of the plurality of cylinders (1) according to a pre-mixing process by terminating the inflow of said first fuel during the stroke of the piston (10) from BDC to TDC for at least one of the cylinders (1) involved. configured to change to operate according to a compression ignition process,
configured to inject said amount of second fuel into at least one of the associated cylinders (1) when the piston (10) is at or near TDC,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
Controller 60 is configured to select the amount of second fuel injected into at least one associated cylinder 1 as follows:
The average indicated pressure of the remaining cylinders (1) among the plurality of cylinders (1) operating according to the premixing process is reduced when the risk of pre-ignition is determined,
The average indicated pressure of the remaining cylinder (1) of the plurality of cylinders (1) operating according to the premix process is increased when the risk of misfire is determined,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to any one of paragraphs 1 and 2,
When a certain time or engine speed has elapsed, the controller 60 changes the operation of the corresponding cylinder 1 from the operation according to the pre-mixing process to the compression ignition process, thereby switching one or more cylinders 1 to the compression ignition process. configured to return from operation according to to operation according to the pre-mixing process,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
The controller 60 is configured to monitor the air-fuel ratio and bulk compression temperature of the cylinder 1 operating according to the premix process, provided that these values are within an acceptable range, and for a given time range, one or more of the cylinders 1 operating according to the compression ignition process. Changing the operation of cylinder (1) to a pre-mixing process,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
No second fuel is injected at all or only a small amount of second fuel is injected as pilot fuel into the cylinder 1 operated according to the premixing process.
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
Each cylinder (1) is provided with a variable timing exhaust valve actuation system for operating an exhaust valve (4) centrally disposed on the cylinder cover (22), wherein the controller (60) opens and closes the exhaust valve (4). It is configured to determine and control timing, and consists of:
The opening and closing time of the exhaust valve 4 suitable for the pre-mixing process for the cylinder 1 of the plurality of cylinders 1 operating according to the pre-mixing process, and
The opening and closing time of the exhaust valve 4 suitable for the compression ignition process for the cylinder 1 of the plurality of cylinders 1 operating according to the compression ignition process,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
The controller (60) is configured to determine or measure the air-to-air ratio for the cylinder (1), wherein the air-fuel ratio is above the maximum air-fuel ratio threshold and the air-fuel ratio is below the minimum air-fuel ratio threshold, thereby creating an unacceptable risk of a pre-ignition event. configured to determine,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
The controller (60) is configured to determine or measure the bulk compression temperature of the cylinder (1) at the start of combustion and to determine an unacceptable risk of a misfire event when the bulk compression temperature is below the minimum bulk compression temperature. , configured to determine the unacceptable risk of a pre-ignition event when the threshold and bulk compression temperature are above the maximum bulk compression temperature threshold,
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
The controller (60) includes or is connected to an air-fuel ratio observer (46) for determining the instantaneous average air-fuel ratio of the cylinder (1).
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
According to paragraph 1,
The controller (60) comprises or is connected to a bulk compression temperature observer (47) for determining the average instantaneous bulk compression temperature of the cylinder (1).
Dual-fuel heavy-duty two-stroke turbocharged Uniflo Scavenger internal combustion engine.
1. A method of operating a dual-fuel, large, two-stroke, turbocharged, Uniflow scavenge internal combustion engine, wherein the engine is in at least one operating mode configured to operate using a primary fuel as a primary fuel, the engine comprising:
- plural cylinders (1),
- a piston (10) reciprocating between BDC and TDC in each cylinder (1),
- at least one fuel inlet valve (30) associated with the cylinder (1) for introducing first fuel during the stroke of the piston (10) from BDC to TDC,
- at least one fuel injection valve (50) associated with at least one of the cylinders (1) for injecting the second fuel when the piston (10) is at or near TDC,
- The above method is:
- Operating all of the plurality of cylinders (1) by receiving the first fuel while the piston (10) is stroked from BDC to TDC basically according to a pre-mixing process,
- determining that the actual combustion conditions in the cylinder (1) operating according to the pre-mix process are such that there is an unacceptable risk of a pre-ignition event or misfire,
The above method is:
If it is determined that there is an unacceptable risk of a pre-ignition event or misfire:
Compression ignition in operating according to a pre-mixing process by terminating the inflow of the first fuel during the stroke of the piston 10 from BDC to TDC, for at least one of the cylinders 1 involved, at least one of the plurality of cylinders 1 making changes to operate according to the process, and
Characterized by injecting an amount of said second fuel into at least one of the associated cylinders (1) when the piston (10) is at or near TDC.
How to run a dual-fuel, large, two-stroke, turbocharged Uniflo Scavenger internal combustion engine.
According to clause 11,
The method comprises selecting an amount of second fuel to be injected into the at least one associated cylinder (1) as follows, the method comprising:
The average indicated pressure of the remaining cylinders (1) among the plurality of cylinders (1) operating according to the premixing process is reduced when the risk of pre-ignition is determined,
The average indicated pressure of the remaining cylinder (1) of the plurality of cylinders (1) operating according to the premix process is increased when the risk of misfire is determined.
How to run a dual-fuel, large, two-stroke, turbocharged Uniflo Scavenger internal combustion engine.
According to any one of claims 11 or 12,
Since the operation of the corresponding cylinder (1) has been changed from operation according to the pre-mixing process to the compression ignition process, when a certain time or engine speed has elapsed, one or more cylinders (1) have been changed from operating according to the compression ignition process to the pre-mixing process. comprising returning it to an operating state according to,
How to run a dual-fuel, large, two-stroke, turbocharged Uniflo Scavenger internal combustion engine.
According to clause 11,
Monitoring the air-fuel ratio and bulk compression temperature of the cylinder (1) operating according to the premix process, and when these values are in an acceptable range, during a given time range, of one or more cylinders (1) operating according to the compression ignition process. changing the operation to a premix process,
How to run a dual-fuel, large, two-stroke, turbocharged Uniflo Scavenger internal combustion engine.
According to clause 11,
Comprising the step of not injecting the second fuel as pilot fuel or injecting only a small amount of the second fuel into the cylinder (1) operated according to the pre-mixing process,
How to run a dual-fuel, large, two-stroke, turbocharged Uniflo Scavenger internal combustion engine.
According to clause 11,
Each cylinder is provided with a variable timing exhaust valve (4) centrally disposed in the cylinder cover (22), the method being:
Opening and closing timing stages of the exhaust valve (4) suitable for the pre-mixing process for the cylinder (1) of the plurality of cylinders (1) operating according to the pre-mixing process, and
Comprising an opening and closing timing step of the exhaust valve (4) suitable for the compression ignition process for the cylinder (1) among the plurality of cylinders (1) operating according to the compression ignition process,
How to run a dual-fuel, large, two-stroke, turbocharged Uniflo Scavenger internal combustion engine.