JP2023162135A - Large turbocharged type two-stroke internal combustion engine with turbo supercharger and method for operating the same - Google Patents

Abstract

To provide a uniflow type of a large turbocharged type two-stroke internal combustion engine which allows operation/stop of a turbo supercharger with relatively high engine load while suppressing risks of surge/stall of the turbo supercharger to the minimum.SOLUTION: A uniflow type large turbocharged type two-stroke internal combustion engine (100) includes a plurality of turbo superchargers to be turbo superchargers (5) at least one of which is selectively operable/stoppable. The engine is provided with a controller (50) configured so that the turbo supercharger (5) selectively operable/stoppable starts/stops the turbo supercharger (5) by relatively high engine load while decreasing risks of surge/stall. A method for operating the engine (100) is disclosed.SELECTED DRAWING: Figure 7

Description

The present disclosure relates to large two-stroke internal combustion engines with multiple exhaust-driven turbochargers for providing scavenging air, and methods of operating such engines.

background

Large turbocharged two-stroke internal combustion engines are often used in propulsion systems for large ships and as prime movers in power plants. Its size, weight, and power set this type of compression internal combustion engine apart from other combustion engines, placing it in a unique category. These engines are constructed using crossheads so that no side pressure is applied to the pistons, since the increased height is not a big problem. Typically, such engines run on natural gas, petroleum gas, methanol, ethane, or (heavy) fuel oil.

Large turbocharged two-stroke internal combustion engines operate on the compression ignition, i.e. diesel principle, and when the scavenging gas is mixed with fuel during the piston stroke from bottom dead center (BDC) to top dead center (TDC). In some cases, it is operated by a premixing engine, that is, by the Otto principle.

In such engines, optimizing turbocharger performance for a single engine load is relatively straightforward. However, large turbocharged two-stroke internal combustion engines need to operate over a wide range of engine loads and operating conditions, and when equipped with only a single (non-variable geometry) turbocharger, the optimal turbocharger Achieving supercharging efficiency is difficult. Variable geometry turbochargers can alleviate some of the problems, but have disadvantages such as increased cost, maintenance and complexity. For example, when optimizing engine efficiency at part load, it has been found that being able to increase the scavenging pressure at part load is effective. Therefore, it has become common to use exhaust bypass to influence scavenging pressure. The effect is obtained by adapting the turbocharger to a specific pressure at 100% load with the bypass open. However, some of the exhaust gas bypasses the turbocharger turbine, reducing the turbocharger's performance. From the cylinder's perspective, this means using an inefficient turbocharger, which has a negative effect on scavenging air. When the bypass is closed at part load, the turbocharger turbine receives all of the available exhaust gas mass flow and converts it into a higher air mass flow, resulting in a higher scavenging pressure at part load. However, a reduction in scavenging air at high loads is of course not desirable. One way to avoid this problem is to install multiple turbochargers and selectively use one or more of the turbochargers to provide the best performance depending on the engine load. The method is to use a selected proportion of the total turbocharging power. By selectively starting and stopping the turbochargers, the turbocharger or turbochargers in operation always get all the exhaust gas power, avoiding deterioration of the scavenging air quality at high loads. . The turbocharger that is activated or deactivated may not have the same size (capacity) as the remaining turbocharger (remaining turbocharger here refers to the turbocharger that is always activated). means). The relative size/capacity of the selectively started and stopped turbochargers is selected according to the desired magnitude of effect on scavenging air pressure.

Therefore, by installing multiple turbochargers and controlling their operating number, high turbocharger efficiency can be achieved over a wide engine load range, compared to a single (non-variable geometry) turbocharger. This improves fuel efficiency and reduces engine operating costs and environmental impact.

When the turbocharger is stopped, 100% engine load is not always possible. The remaining turbochargers do not have enough capacity to handle the entire amount of exhaust gas. This means that the turbocharger must be operated at relatively high loads, typically as the engine load approaches maximum engine load (maximum continuous rating). Operate between 50% and 75% of the rating. The same applies to the reverse process of deactivating the turbocharger, which also typically has to be carried out at similar or the same relatively high engine loads.

However, in practice, it is important to maintain the operating point of the turbocharger compressor within the compressor diagram during cut-in and cut-out, so that the turbocharger can be activated or deactivated at such high engine loads. It is known that it is difficult to do so. If the turbocharger speed becomes too low for the current pressure ratio, the compressor will be forced into surge/stall. A surge is a disruption of steady flow within a compressor. This typically occurs at low flow rates when the compressor operates out of design, and affects the entire turbocharger, making it undesirable both aerodynamically and mechanically. There is also the possibility of damaging the turbocharger. Surges not only result in high temperatures and vibrations, but can also cause flow reversals. In other words, the flow may be reversed and flow out of the compressor silencer. As a result, high loads are placed on the mechanical components of the turbocharger. Although a single surge/stall will not be fatal to the turbocharger, many surges/stalls over a long period of time will impair the reliability of the turbocharger.

This problem has not been solved in the technical field of the present application. That is, the compressor operating point cannot be maintained at a desired location or region on the compressor diagram. Therefore, the art has avoided this problem by starting and stopping turbochargers at relatively low engine loads, typically approximately 10% of maximum continuous rating. However, this means that each time the turbocharger is started or stopped, the engine has to be slowed down to 10% engine load, which is highly undesirable and often impossible in practice. be. For example, if the engine is used as the main propulsion engine on an ocean-going vessel, it may be undesirable to have to slow the engine down to 10% engine load before being able to operate at, say, 65% engine load or higher. .

US2010/0281862 discloses a marine engine with multiple turbochargers. In this engine, it is stated that the turbochargers are switched from single operation to parallel operation or from parallel operation to single operation to prevent surges of the turbochargers being started or stopped. This marine diesel engine has an exhaust manifold mounted on the engine body connected to an exhaust pipe that connects to the turbine section, a turbine inlet valve connected somewhere in the exhaust pipe, and a compressor section connected to the supply manifold mounted on the engine body. A connecting supply pipe, a check valve connected somewhere in the supply pipe that opens when the pressure exceeds the outlet pressure of the compressor section, and one end connected somewhere in the supply pipe between the compressor section and the check valve. It includes a connected air bleed pipe and an air bleed valve connected somewhere on the air bleed pipe. The air bleed valve is closed when the turbine inlet valve reaches an almost open position when the turbocharger is started, and is opened just before the turbine inlet valve starts to close when the turbocharger is stopped. However, tests conducted by the inventors of the present application have shown that turbocharger surges are not reliably prevented even if the teachings of US 2010/0281862 are followed.

The engine disclosed in Japanese Unexamined Patent Publication No. 2015162840A1 starts from a state in which the main supercharger and the auxiliary supercharger are operating, and then closes the auxiliary turbine inlet valve and the auxiliary compressor outlet valve while the main supercharger is operating. Close and stop the auxiliary turbocharger. In addition, when reducing the number of operating turbochargers, a reference pressure at stop with a predetermined surge margin is determined based on the rotation speed of the auxiliary turbocharger, and when the outlet pressure of the auxiliary compressor is higher than the reference pressure at stop. The blow-off valve is opened when the auxiliary compressor outlet pressure is lower than the reference pressure at the time of shutdown, and the blow-off valve is closed.

Abstract

The purpose of the present invention is to provide a large uniflow type turbocharger that enables the turbocharger to be activated/deactivated at relatively high engine loads while minimizing the risk of turbocharger surge/stall. An object of the present invention is to provide a two-stroke internal combustion engine.

This and other objectives are achieved by features of the present disclosure. Various possible implementations will become apparent from the description and drawings.

According to the first approach, the following uniflow large turbocharged two-stroke internal combustion engine is provided. This institution is
a plurality of cylinders each having a scavenging port at a lower end and an exhaust valve at an upper end;
an intake system having a scavenging air receiver connected to the cylinder through the scavenging port, through which scavenging gas is introduced into the cylinder;
an exhaust system having an exhaust receiver connected to the cylinder through the exhaust valve, through which exhaust gas generated in the cylinder is exhausted;
an exhaust-driven turbine coupled to the compressor to operate the compressor; an inlet of the turbine connected to the exhaust system; and an outlet of the compressor for pressurizing the scavenging air receiver. a plurality of turbochargers each having an outlet connected to the intake system for delivering a scavenging air flow;
Equipped with
At least one of the plurality of turbochargers is a turbocharger that can be selectively activated and stopped, and the turbocharger that can be selectively activated and stopped is
a turbine that is selectively connected to the exhaust receiver by an electronically controlled turbine control valve and that can be activated and deactivated;
A compressor that can be started and stopped,
has
The outlet of the actuatable compressor is selectively connected to the intake system by an electronically controlled compressor control valve and connected to the outlet of the actuatable compressor upstream of the compressor control valve. connected to outside air through an electronically controlled air bleed valve.
the air bleed valve is a variable valve that forms a controllable variable restriction on the flow of gas through the air bleed valve;
The engine further includes a controller, the controller being combined with the turbine control valve, the compressor control valve, and the air bleed valve,
The controller further includes, when starting the selectively actuable/deactivable turbocharger,
transitioning the turbine control valve from a closed state to an open state;
transitioning the compressor control valve from a closed state to an open state;
The air bleed valve is connected to the measured or estimated pressure at the outlet of the actuatable/stoppable compressor and the measured or estimated rotational speed of the selectively actuable/stoppable turbo supercharger. continuously transitioning into a closed state as at least one function;
It is configured as follows.

By continuously shifting the air bleed valve from the open state to the closed state according to the function, it becomes possible to control the pressure at the outlet of the actuatable/stoppable compressor, and thus the actuator/stoppable compressor. This makes it possible to control the pressure ratio (upstream and downstream) of the compressor to a certain level. This level is the level at which the compressor operating point, defined by the combination of compressor pressure ratio and turbocharger or compressor speed, is a certain distance away from the operating point at which the compressor surges/stalls. In other words, it is a level with a margin up to surge/stall. Therefore, it is possible to significantly reduce the risk of a surge/stall occurring in the compressor that can be activated and stopped when the compressor is started.

In one example of an implementation of the first perspective, the function is derived from an operating point of the actuator/stoppable compressor that is known to be at a safe distance from surges or stalls. .

In one example of an implementation of the first perspective, the function is derived from compressor characteristics, for example compressor characteristics defined in a compressor diagram associated with a deactivable compressor.

By controlling the pressure at the outlet of the actuated and deactivated compressor as a function obtained from the compressor diagram, it is possible to control the starting of the turbocharger in such a way that stalls and surges are prevented or at least reduced. become.

In an example of an implementation of the first approach, when the controller stops the selectively actuable/stoppable turbocharger,
Shifting the compressor control valve from an open state to a closed state,
transitioning the turbine control valve from an open state to a closed state, preferably after the compressor control valve has closed;
The air bleed valve is connected to the measured and/or estimated pressure at the outlet of the actuatable/stoppable compressor and the measured and/or estimated rotational speed of the selectively actuable/stoppable turbocharger. transitioning the air bleed valve to an open state as a function of at least one of;
It is configured as follows.

By continuously shifting the air bleed valve from the closed state to the open state according to the function, it becomes possible to control the pressure at the outlet of the actuatable/stoppable compressor, and thus the actuator/stoppable compressor. This makes it possible to control the pressure ratio (upstream and downstream) of the compressor to a certain level. This level is the level at which the compressor operating point, defined by the combination of pressure ratio and turbocharger rotational speed, is a certain distance away from the operating point at which the compressor surges/stalls, i.e. This is a level with a margin up to a surge/stall. Therefore, it is possible to significantly reduce the risk of a surge or stall occurring in the compressor when the compressor that can be activated and stopped is stopped.

In an example of the embodiment of the first approach, the controller controls the selectively actuable/stoppable turbocharger in a certain rotational speed range of the selectively actuate/stoppable turbocharger. is informed of the target pressure at the outlet of the startable/stoppable compressor for a given rotational speed of the compressor.

In an example of an implementation of the first approach, the controller is configured such that the actual pressure at the outlet of the actuatable/stoppable compressor is based on the actual rotational speed of the selectively actuable/stoppable turbocharger. The air bleed valve is moved to a position that corresponds to the target pressure. By ensuring that the actual pressure at the outlet of the actuator-stoppable compressor corresponds to the target pressure, it is possible to maintain the operating point in an optimal position, for example in a position corresponding to maximum efficiency of the compressor. . Also, by maintaining the operating point of the actuator-stoppable compressor at or near its optimum operating position, the risk of stalling is also significantly reduced.

In an example of an implementation of the first approach, the target pressure for a given rotational speed of the selectively actuable/stoppable turbocharger is the At the same given rotational speed of the machine, the switchable compressor is separated from the surge pressure by a surge margin.

In one example of an implementation of the first perspective, the target pressure at a given rotational speed of the selectively actuatable turbocharger is at the same point in the selectively actuatable turbocharger. At a given rotational speed, the deactivable compressor corresponds to the pressure at which it has the highest efficiency.

In an example of an implementation of the first perspective, the engine includes a pressure sensor that provides a signal representative of the pressure at the outlet of the actuable/deactivable compressor, and the selectively actuable/deactivable turbocharger. and a speed sensor configured to provide a signal representative of the rotational speed of the machine.

In an example implementation of the first perspective, the controller is configured to determine the target pressure based on a signal from the speed sensor.

In an example of an implementation of the first perspective, the controller is configured to determine a difference between the target pressure and a signal from the pressure sensor, and to determine a set point for the air bleed valve as a function of the difference. It is composed of

In an example of an implementation of the first perspective, the controller is configured to determine a set point for the turbine control valve and/or the compressor control valve as a function of the determined difference from the set point. It is composed of

In an example of an implementation of the first perspective, the turbine control valve is disposed upstream of the actuatable turbine, and/or the compressor control valve is located upstream of the actuatable compressor. The air bleed valve is located downstream and/or the air bleed valve is located in an air bleed pipe downstream of the selectively actuatable turbocharger compressor and upstream of the compressor control valve.

In an example of an implementation of the first approach, the estimated pressure and/or estimated rotational speed of the selectively actuable/stoppable turbocharger is determined by one or more tests and/or simulations, or by experience. This is a pre-stored value obtained from .

In one example of an implementation of the first perspective, the engine includes a fuel system for supplying fuel to the cylinders.

In one example of an implementation of the first perspective, the turbine control valve is configured to control the flow of exhaust gas to a deactivatable turbine.

In one example of an implementation of the first perspective, the compressor control valve is configured to control the flow of scavenging gas from the actuatable compressor to the scavenging air receiver.

In an example of the implementation of the first approach, the engine includes a pressure sensor for detecting the scavenging gas pressure in the scavenging air receiver and/or an observation device for estimating the scavenging pressure in the scavenging air receiver. Be prepared.

In one example of an implementation of the first perspective, the controller is configured to selectively activate and deactivate the turbo as a function of engine operating conditions, preferably as a function of engine load, scavenging pressure or load set point. It is configured to activate and deactivate the supercharger.

In one example of an implementation of the first perspective, the controller adjusts actual engine turbocharging as a function of sensed or observed scavenging pressure and/or sensed or observed exhaust temperature. configured to determine efficiency. Here, the term "engine turbocharging efficiency" refers to the turbocharging efficiency experienced or felt by the engine, regardless of ambient conditions.

In one example of an implementation of the first perspective, the compressor control valve is a variable valve that forms a controllable variable restriction on the flow of gas through the compressor control valve, and the controller is configured to control the flow of gas through the compressor control valve. the measured or estimated pressure at the outlet of the selectively actuable/stoppable compressor and the selectively actuable/stoppable turbocharger when starting the selectively actuable/stoppable turbocharger; The compressor control valve is configured to move in the opening direction as a function of the measured or estimated rotational speed of the compressor control valve.

According to a second perspective, a method is provided for operating a large uniflow turbocharged two-stroke internal combustion engine. Here, the institution is
a plurality of cylinders each having a scavenging port at a lower end and an exhaust valve at an upper end;
an intake system having a scavenging air receiver connected to the cylinder through the scavenging port, through which scavenging air is introduced into the cylinder;
an exhaust system having an exhaust receiver connected to the cylinder through the exhaust valve, through which exhaust gas generated in the cylinder is exhausted;
an exhaust-driven turbine coupled to the compressor to operate the compressor; an inlet of the turbine connected to the exhaust system; and an outlet of the compressor for pressurizing the scavenging air receiver. a plurality of turbochargers each having an outlet connected to the intake system for delivering a scavenging air flow;
Equipped with
At least one of the plurality of turbochargers is a turbocharger that can be selectively activated and stopped, and the turbocharger that can be selectively activated and stopped is
a turbine that is selectively connected to the exhaust receiver via an electronically controlled turbine control valve and that can be activated and deactivated;
A compressor that can be started and stopped,
has
The outlet of the actuatable compressor is selectively connected to the intake system by an electronically controlled compressor control valve and connected to the outlet of the actuatable compressor upstream of the compressor control valve. connected to outside air through an electronically controlled air bleed valve.
the air bleed valve is a variable valve that forms a controllable variable restriction on the flow of gas through the air bleed valve;
And the method is
measuring or estimating at least one of the pressure at the outlet of the actuable/stoppable compressor and the rotational speed of the selectively actuable/stoppable turbocharger;
starting the at least one selectively actuable/deactivable turbocharger;
- Shifting the turbine control valve from a closed state to an open state,
- transitioning the compressor control valve from a closed state to an open state, preferably after the turbine control valve has opened;
- The air bleed valve is set to one of the measured or estimated pressure at the outlet of the actuatable/stoppable compressor and the measured or estimated rotational speed of the selectively actuable/stoppable turbo supercharger. continuously transitioning from a closed state to an open state as a function of at least one of
to start by;
including.

In an example of an implementation of the second perspective, the method includes deactivating the at least one selectively actuatable turbocharger,
Shifting the compressor control valve from an open state to a closed state,
transitioning the turbine control valve from an open state to a closed state, preferably after the compressor control valve has closed;
The air bleed valve is connected to the measured or estimated pressure at the outlet of the actuatable/stoppable compressor and the measured or estimated rotational speed of the selectively actuable/stoppable turbo supercharger. continuously transitioning from an open state to a closed state as at least one function;
Including stopping by.

The above aspects and other aspects of the invention will become more apparent from the embodiments described below.

Various aspects, embodiments, and implementations will now be described in detail with reference to exemplary embodiments illustrated in the drawings.
1 is a frontal, overhead view of a large two-stroke internal combustion engine with multiple turbochargers, in accordance with an exemplary embodiment; FIG. FIG. 2 is an overhead view of the large two-stroke internal combustion engine of FIG. 1 from the rear. 2 is a diagrammatic representation of the large two-stroke internal combustion engine according to FIG. 1; In this figure, only one of the plurality of turbochargers is shown to keep the diagram as simple as possible. It is a graph showing the scavenging pressure during the test. 3 is a graph showing valve movement and stall margin during testing. 2 is a control diagram of the engine of FIG. 1, 2 is a diagrammatic representation of an embodiment of the large two-stroke internal combustion engine of FIG. 1 with two turbochargers; FIG. 2 is a graph showing an example of valve movement of the engine according to FIG. 1; 2 is a graph showing an example of the scavenging pressure, work line setting value, and actual work line of the engine shown in FIG. 1. FIG. 2 is a graph showing an example of a surge margin of the engine according to FIG. 1; 1 is a diagrammatic representation of another embodiment of a large two-stroke internal combustion engine; This embodiment includes three turbochargers.

Detailed explanation

1-3 depict a large, low-speed, turbocharged, two-stroke diesel engine 100. This engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a large, turbocharged, low-speed, two-stroke diesel engine with its intake and exhaust systems. In this embodiment 100, the engine has six cylinders 1 in series. Large, turbocharged, low-speed, two-stroke diesel engines typically have four to fourteen cylinders arranged in series. These cylinders are carried by a cylinder frame 23. The cylinder frame 23 is carried by the engine frame 11. The engine 100 can be used, for example, as a main engine of a ship or a fixed engine for operating a generator in a power plant. The total power of the engine 100 may be, for example, from 1000 kW to 110000 kW.

The engine 100 in this embodiment is a two-stroke uniflow compression ignition engine, and each cylinder liner 1 is provided with a scavenging port 18 in its lower region, and an exhaust valve is arranged in the center of the top. However, the engine 100 does not necessarily have to be a compression ignition type (diesel principle), and may be a premix engine (Otto principle) depending on the embodiment. In the embodiment presented here, the compression pressure of engine 100 is high enough to provide compression ignition. However, engine 100 may also be a premix engine operating at lower compression pressures and ignited by a spark or similar means.

Scavenging air is introduced into the cylinder 1 through the intake system. The intake system includes a scavenging receiver 2 connected to the cylinder 1 via a scavenging port 18 .

The exhaust gas generated in the cylinder is exhausted through the exhaust system. The exhaust system includes an exhaust receiver 3 connected to the cylinder 1 via an exhaust valve 4.

The intake system of the engine 100 includes a receiver 2 for scavenging gas or scavenging air. When EGR is not used, receiver 2 receives only air; when EGR is used, receiver 2 receives a mixture of exhaust gas and scavenging air. Receiver 2 is therefore called a "scavenging air receiver". Scavenging air is guided through the scavenging air receiver 2 to the scavenging air port 18 of each cylinder 1. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1 and compresses scavenging air. Fuel is injected from a fuel valve 55 disposed on the cylinder cover 22. Combustion then follows and exhaust gas is produced. Alternatively, the fuel valve 55 is located in the cylinder liner and fuel is introduced during the piston stroke from BDC to TDC. The scavenging air and fuel mixture is compressed and ignition is triggered when the piston is at or near TDC, combustion continues and exhaust gas is produced.

A central exhaust valve 4 is arranged in the central opening of the cylinder cover 22 . In addition, a plurality (preferably three or four) of fuel valves 55 are arranged in the cylinder cover 22 at the central opening or around the central exhaust valve 4 . The exhaust valve 4 is actuated by an electro-hydraulic exhaust valve actuation system 29 which is controlled by a controller (electronic control unit) 50. Fuel is supplied to the fuel valve 55 by the fuel supply system 30. Controller 50 is also configured to control the operation of fuel valve 55.

When the exhaust valve 4 is opened, the exhaust gas flows from the central opening of the cylinder cover 22 through the exhaust system having an exhaust duct (provided in each cylinder 1) into the exhaust receiver 3 and into the first exhaust pipe line. 19 to the turbine 8 of the turbocharger 5. From there, the exhaust gases pass through a second exhaust line, via an economizer 20, to an outlet 21 and are discharged into the atmosphere. Note that although the engine 100 includes a plurality of turbochargers 5, all the turbochargers do not necessarily operate at the same time.

The turbine 8 of the turbocharger 5 in operation drives the compressor-7 through the shaft of the turbocharger 5. The compressor-7 is supplied with outside air through an air intake port 12. The compressor 7 sends compressed scavenging air to the scavenging pipe 13 connected to the scavenging air receiver 2. Typically, each compressor 7 is provided with a scavenging pipe 13. The scavenging air from the scavenging pipe 13 passes through an intercooler 14 and a water mist catcher 63 for cooling the scavenging air.

Engine 100 includes two or more turbochargers 5 and a controller 50. At least one of the turbochargers 5 is a turbocharger 5 that can be selectively activated and stopped. The controller 50 controls at least one selectively actuable/stoppable turbocharger 5 when the engine load is below a shutdown engine load threshold such that only one turbocharger 5 with an appropriate flow path area is activated at low engine loads. The supercharger 5 is configured to be stopped. The controller 50 is also configured to start at least one selectively actuatable turbocharger 5 when the engine load exceeds a starting engine load threshold. The starting engine load and the stopping engine load may be the same or different, and the flow passage area of the operating turbocharger 5 is selected to match the engine load.

FIG. 7 shows an embodiment of an engine 100 with two turbochargers 5, each in a separate scavenging path. The turbocharger 5 on the left side of FIG. 7 is a turbocharger that can be selectively activated and stopped, and the turbocharger 5 on the right side of FIG. 7 is always activated. The turbocharger 5 that can be selectively activated and stopped and the turbocharger 5 that is constantly activated may have the same capacity or different capacities. In particular, the turbocharger 5 that can be selectively activated and deactivated can have a smaller capacity than the turbocharger 5 that is constantly activated. The controller 50 operates the turbocharger 5, which can be selectively activated and deactivated, according to the actual operating conditions of the engine, in particular the actual engine load, with the aim of achieving optimal turbocharging efficiency of the engine 100. and configured to stop.

An electronically controlled turbine control valve 35 is disposed in a conduit connecting the exhaust receiver 3 and the inlet of a turbine 8 that can be selectively activated and deactivated in a turbocharger 5 that can be activated and deactivated selectively. Turbine control valve 35 is connected to controller 50 , and the position of turbine control valve 35 is controlled by controller 50 through a signal to turbine control valve 35 . The controller 50 uses the turbine control valve 35 to open and shut off the flow of exhaust gas from the exhaust receiver 3 to the inlet of the turbine 8, which can be activated and stopped.

An electronically controlled conduit connects the outlet of the compressor 7, which can be selectively activated and deactivated, of the turbocharger 5, which can be activated and deactivated, to the scavenging air receiver 2 through the scavenging air cooler 14 and the water mist catcher 63. A compressor control valve 36 is arranged. Compressor control valve 36 is connected to controller 50 , and the position of compressor control valve 36 is controlled by controller 50 through a signal to compressor control valve 36 . The controller 50 can open or shut off the flow of scavenging air from the outlet of the compressor 7, which can be activated and stopped, to the scavenging air receiver 2 through the compressor control valve 36.

At least the turbocharger 5 that can be selectively activated and stopped is provided with a rotational speed sensor that generates a signal representing the rotational speed of the turbocharger 5 that can be selectively activated and stopped, and this signal is transmitted to the controller. 50. The pressure sensor 33 is arranged to measure the pressure at the outlet of the compressor 7, which can be activated and deactivated. Pressure sensor 33 is located upstream of compressor control valve 36. The signal from pressure sensor 33 is transmitted to controller 50 .

An electronically controlled air bleed valve 37 connects the outlet of the compressor 7, which can be activated and deactivated, to another environment, e.g. having a pressure at or substantially equal to atmospheric pressure, e.g. downstream of the turbocharger 5. The air bleed valve 37 is disposed between the exhaust system or the inlet side of the compressor 7 that can be activated and stopped selectively, and the air bleed valve 37 is disposed between the exhaust system and the inlet side of the compressor 7 that can be activated and stopped selectively. is connected to. Preferably, the air bleed valve 37 is arranged in an air bleed line 39 that branches off from the conduit connecting the outlet of the actuatable compressor 7 to the compressor control valve 36 . The air bleed valve 37 is a variable valve that provides a controllable variable restriction to the flow of gas through the air bleed valve 37. Thus, controller 50 controls the restriction on air flow through bleed valve 37 by adjusting the position of bleed valve 37.

4 and 5 show the results of attempts to activate and deactivate the turbocharger 5, which can be selectively activated and deactivated using only the turbine control valve 35 (TCV) and compressor control valve 36 (CCV). It is a diagram. FIG. 4 is a plot showing the scavenging air pressure (bar) in the scavenging air receiver 2 versus time, and FIG. 5 shows the opening and closing of the turbine control valve 35 and compressor control valve 36 versus time, with 0 on the vertical axis indicating a fully closed valve; This is a plot where 1 on the vertical axis corresponds to a fully open valve. In addition, stall margins are also plotted in FIG. Stall margin is a measure of how close the compressor is to stall. In FIG. 5, the stall margin becomes negative within about 4 seconds to 13 seconds after the compressor control valve 36 and turbine control valve 35 are opened, clearly indicating that the compressor is stalled. We tried changing the opening profile and timing of the turbine control valve 35 and the compressor control valve 36, but it was not possible to increase the surge/stall margin to more than zero during the operation and stop of the turbocharger 5, which can be selectively activated and stopped. The results were not sustainable.

The efficiency of a compressor can be described by a constant efficiency line in a diagram (compressor diagram) in which the pressure ratio applied to the compressor 7 is plotted against the air flow rate passing through the compressor 7. The constant efficiency line is an elliptical curve in which the efficiency of the compressor 7 is constant in this compressor diagram. The pressure ratio is the ratio of the pressure at the outlet of the compressor 7 divided by the pressure at the inlet of the compressor 7. Since the pressure at the inlet of compressor 7 is substantially equal to atmospheric pressure, which can be assumed to be substantially constant, controller 50 requires only the pressure at the outlet of compressor 7 to determine the pressure ratio on compressor 7. , by measurement (e.g. using a pressure sensor) or estimation (e.g. using an observation device). Although it is difficult to directly measure the airflow through the compressor 7, in some embodiments it is determined (calculated) by the controller 50 as a function of the rotational speed of the compressor 7, i.e. the rotational speed of the turbocharger 5. .

In some embodiments, for a certain turbocharger speed range, the optimum pressure ratio of the actuable/stoppable compressor 7 provides the highest compression efficiency for the rotational speed of the selectively turnable/stoppable turbocharger 5. is stored in the controller 50 as a work line that can be represented, for example, in a diagram where the optimum pressure ratio is plotted against turbocharger speed.

In another embodiment, the (atmospheric) pressure at the inlet of the actuable compressor 7 is known and constant, so that the turbocharger 5 can be selectively activated and deactivated for a certain turbocharger speed range. The optimum pressure at the outlet of the deactivable compressor 7 is stored in the controller 50, resulting in the highest compression efficiency for the rotational speed of .

FIG. 6 is a control diagram for controlling the positions of the turbine control valve 35 (TCV), compressor control valve 36 (CCV), and air bleed valve 37 (ARV). The measured or estimated rotational speed of the turbocharger 5 is provided to a target pressure estimator. The target pressure estimator may be part of controller 50 or may be a separate control unit. The target pressure estimator calculates the optimal pressure at the outlet of the compressor 7, which can be activated and deactivated, for the actual rotational speed of the turbocharger, using, for example, the above-mentioned stored work line. The target pressure is compared with the measured or determined actual pressure at the outlet of the deactivatable compressor 7 and the difference between the two signals is determined. This difference is sent to the valve controller. The valve controller may be part of controller 50 or may be a separate controller. The valve controller adjusts the position of the air bleed valve 37 according to the above difference. For controlling the air bleed valve 37, the valve controller increases the restriction on the flow provided by the air bleed valve 37 when the pressure at the outlet of the actuatable compressor 7 is lower than the target pressure, Proportional (P) control, or Proportional and Integral (PI) control, or Proportional-Integral and Differential control to reduce the restriction on flow posed by the bleed valve 37 when the pressure at the outlet of the compressor is higher than the target pressure. control (PID). Thus, the turbocharger rotational speed is used in the first feedback control loop and the compressor outlet pressure is used in the second feedback control loop. Therefore, in this embodiment, the control diagram forms a dual feedback loop control.

In some embodiments, the valve controller controls the opening and closing of turbine control valve 35 and compressor control valve 36 according to a predetermined profile and sequence. The profile or work line for starting the turbocharger 5 that can be selectively activated and stopped, and the profile or workline for stopping the turbocharger 5 that can be selectively activated and stopped are used for testing or These predefined profiles and sequences, which can be determined by simulation, are stored in controller 50.

FIG. 8 shows a valve over time for selectively activating and deactivating the turbocharger 5 when the engine is operating at 50% engine load (50% of maximum continuous rating). An example of the result of the operation is shown. The turbocharger 5, which can be selectively activated and deactivated, is activated, for example, when the engine load rises above an engine load threshold. In this example, controller 50 is configured to start turbocharger 5, which can be selectively activated and deactivated, by moving turbine control valve 35 from fully closed to fully open. Controller 50 is configured to transition compressor control valve 36 from a fully closed position to a fully open position after a period of time after turbine control valve 35 is opened. This is not a fixed, predetermined period of time. Compressor control valve 36 is opened when the pressure setpoint is no longer increasing. The time at which this occurs depends on the acceleration of the turbocharger 5. Starting from the open position, the air bleed valve 37 is controlled according to the control method described above, i.e. as a function of the rotational speed of the selectively actuatable/deactivatable turbocharger 5 and the pressure at the outlet of the activatable/deactivatable compressor 7. As, close. This function is determined by compressor characteristics. This compressor characteristic can be described, for example, using a compressor diagram, as explained above. The compressor diagram combines the speed and outlet pressure of the compressor 7, which can be activated and deactivated, to determine the operating point at which the compressor functions optimally (with high efficiency), or at least without risk of stall/surge. possible.

In this example, compressor control valve 36 opens after turbine control valve 35 . However, this is not always the case and depends on the circumstances, in particular on the acceleration of the turbocharger 5.

The turbocharger 5, which can be selectively activated and deactivated, is deactivated, for example, when the engine load falls below an engine load threshold. Note that this threshold value may be different from the engine load threshold value for starting the turbocharger 5, which can be selectively activated and deactivated. In this example, controller 50 is configured to initiate the process of shutting down selectively actuatable turbocharger 5 by moving compressor control valve 36 from fully open to fully closed. Controller 50 is configured to transition turbine control valve 35 from a fully open position to a fully closed position a period of time after turbine compressor control valve 36 is closed. Starting from the closed position, the air bleed valve 37 is controlled according to the control method described above, i.e. as a function of the rotational speed of the selectively actuatable/deactivatable turbocharger 5 and the pressure at the outlet of the activatable/deactivatable compressor 7. As, open.

FIG. 9 shows the scavenging pressure in the scavenging air receiver 2 as a result of control, the work line set value of the air bleed valve 37, and the actual work line of the air bleed valve 37 versus time. FIG. 10 is a diagram showing the surge margin against time, and the surge margin is positive both when the turbocharger 5, which can be selectively activated and stopped, is activated and stopped, reducing the risk of surge. It can be seen that this has been significantly reduced. The surge margin is an index indicating how close the compressor 7 is to a surge.

In this way, the controller can adjust the position of the air bleed valve so that the actual pressure at the outlet of the actuable and deactivable compressor 7 remains close to the target pressure.

Here, the target pressure is in accordance with the peak efficiency of the compressor 7, which can be activated and deactivated.

The behavior of the turbocharger 5, which can be selectively activated and deactivated, can be predicted on the basis of engine tests in test beds and/or computer simulations. The appropriate opening curve of the air bleed valve 37 can therefore be based on stored data, measuring the turbocharger speed and/or the outlet pressure of the actuable compressor 7 in real time or There is no need to decide. Controller 50 may be provided with one or more work lines for opening pressure relief valve 37. Preferably, each of these curves (work lines) is suitable for a particular engine load.

In some embodiments, compressor control valve 36 is a variable valve that provides a controllable variable restriction to the flow of gas through compressor control valve 36. In this embodiment, the controller 50 includes a selectively deactivable turbocharger to assist the air bleed valve 37 in its task of controlling the pressure at the outlet of the selectively deactivable compressor 7. When starting the machine 5, as a function of both the measured or estimated pressure at the outlet of the actuatable/deactivable compressor 7 and the measured or estimated rotational speed of the selectively activatable/deactivable turbocharger 5, The compressor control valve 36 is configured to transition from closed to open.

FIG. 11 is a diagrammatic representation of an engine 100 according to another embodiment. This engine 100 includes two constantly operating turbochargers 5 and one turbocharger 5 that can be selectively activated and stopped. In this embodiment, structures and features similar to those already described or illustrated are given the same reference numerals as previously used. Apart from the additional permanently active turbocharger 5, the engine 100 according to this embodiment is essentially the same as the previously introduced engine. However, because of the additional constantly operating turbocharger, the engine load at which the turbocharger 5, which can be selectively activated and stopped, operates and the engine load at which it stops differs from the previously introduced engine. The engine load at which the selectively actuable/stoppable turbocharger 5 is started and stopped is determined by the capacity and characteristics of the respective turbocharger 5 .

Methods and institutions have been described in conjunction with several embodiments. However, upon studying the specification, drawings, and claims of this application, those skilled in the art will realize that there are many variations in addition to the described embodiments in carrying out the invention described in the claims. You will be able to understand this and embody it. The use of the words "comprising," "having," and "including" in the claims does not exclude the presence of unstated elements or steps. Even if it is not explicitly stated that there is a plurality of elements recited in the claims, this does not exclude the existence of a plurality of the elements. The functions of several elements recited in the claims may be performed by a single controller or other unit. Even if several matters are recited in separate dependent claims, this does not preclude their implementation in combination, which can be implemented to advantage.

Any reference signs used in the claims shall not be construed as limiting the scope of the invention. Unless otherwise noted, the drawings are intended to be read in conjunction with the specification and are a part of the entire disclosure herein. In the specification, the terms "horizontal," "vertical," "left," "right," "above," and "bottom" merely refer to the orientation of the illustrated structure as viewed by the reader.

Claims (16)

It is a uniflow type large turbocharged two-stroke internal combustion engine,
a plurality of cylinders each having a scavenging port at a lower end and an exhaust valve at an upper end;
an intake system having a scavenging air receiver connected to the cylinder through the scavenging port, through which scavenging air is introduced into the cylinder;
an exhaust system having an exhaust receiver connected to the cylinder through the exhaust valve, through which exhaust gas generated in the cylinder is exhausted;
an exhaust-driven turbine coupled to the compressor to operate the compressor; an inlet of the turbine connected to the exhaust system; and an outlet of the compressor for pressurizing the scavenging air receiver. a plurality of turbochargers each having an outlet connected to the intake system for delivering a scavenging air flow;
Equipped with
At least one of the plurality of turbochargers is a turbocharger that can be selectively activated and stopped, and the turbocharger that can be selectively activated and stopped is
a turbine that is selectively connected to the exhaust receiver via an electronically controlled turbine control valve and that can be activated and deactivated;
A compressor that can be started and stopped,
has
The outlet of the actuatable compressor is selectively connected to the intake system by an electronically controlled compressor control valve and connected to the outlet of the actuatable compressor upstream of the compressor control valve. connected to outside air through an electronically controlled air bleed valve.
the air bleed valve is a variable valve that forms a controllable variable restriction on the flow of gas through the air bleed valve;
The engine further includes a controller, the controller being combined with the turbine control valve, the compressor control valve, and the air bleed valve;
The controller further includes, when starting the selectively actuable/deactivable turbocharger,
- Shifting the turbine control valve from a closed state to an open state,
- Shifting the compressor control valve from a closed state to an open state,
・The air bleed valve is
- the measured or estimated pressure at the outlet of the actuatable compressor;
- the measured or estimated rotational speed of the turbocharger that can be selectively activated and deactivated;
Continuously transition from the open state to the closed state as two functions of
configured as,
institution. When the controller stops the selectively actuable/stoppable turbocharger,
- Shifting the compressor control valve from an open state to a closed state,
- Shifting the turbine control valve from an open state to a closed state,
・The air bleed valve is
- the measured or estimated pressure at the outlet of the actuatable compressor;
- the measured or estimated rotational speed of the turbocharger that can be selectively activated and deactivated;
successively transitioning into an open state as a function of at least one of
An institution according to claim 1, configured to. The controller is configured to control the starting/stopping speed of the selectively starting/stopping turbocharger for a predetermined rotational speed of the selectively starting/stopping turbocharger within a certain rotational speed range of the selectively starting/stopping turbosupercharger. 2. The engine according to claim 1, wherein the engine is informed of a target pressure at the outlet of the compressor. the controller is in a position such that the actual pressure at the outlet of the actuatable compressor corresponds to the target pressure for the actual rotational speed of the selectively actuatable turbocharger; 4. The engine according to claim 3, wherein said air bleed valve is actuated. The target pressure for a given rotational speed of the selectively actuable/stoppable turbo supercharger is the target pressure for a given rotation speed of the selectively actuable/stoppable turbocharger. 4. An engine as claimed in claim 3, in which the compressor is separated by a surge margin from the pressure at which it surges. The target pressure at a given rotational speed of the selectively actuatable turbocharger is equal to the target pressure of the actuatable compressor at the same given rotational speed of the selectively actuatable turbocharger. 4. The engine according to claim 3, wherein the pressure corresponds to the pressure at which the engine has the highest efficiency. a pressure sensor configured to provide a signal representative of a pressure at the outlet of the selectively actuatable compressor; and a pressure sensor configured to provide a signal representative of a rotational speed of the selectively actuatable turbocharger. 4. The engine of claim 3, comprising at least one speed sensor configured. 8. The engine of claim 7, wherein the controller is configured to determine the target pressure based on a signal from the speed sensor. 9. The engine of claim 8, wherein the controller is configured to determine a difference between the target pressure and a signal from the pressure sensor and determine a set point for the bleed valve as a function of the difference. 10. The engine of claim 9, wherein the controller is configured to determine a setpoint of the turbine control valve and/or the compressor control valve as a function of the difference. The turbine control valve is disposed upstream of the actuatable turbine, and/or the compressor control valve is disposed downstream of the actuatable compressor, and/or the air bleed valve is disposed downstream of the actuatable compressor. 2. The engine of claim 1, wherein: is located in an air bleed pipe downstream of a compressor of the selectively actuable/deactivable turbocharger and upstream of the compressor control valve. The engine according to claim 1, further comprising a pressure sensor for detecting the scavenging gas pressure in the scavenging air receiver and/or an observation device for estimating the scavenging pressure in the scavenging air receiver. The engine of claim 1, wherein the controller is configured to activate and deactivate the selectively deactivable turbocharger as a function of operating conditions of the engine. the compressor control valve is a variable valve that forms a controllable variable restriction on the flow of gas through the compressor control valve;
When the controller starts the selectively actuable/stoppable turbocharger,
- the measured or estimated pressure at the outlet of the actuatable compressor;
- the measured or estimated rotational speed of the turbocharger that can be selectively activated and deactivated;
2. The engine of claim 1, wherein the compressor control valve is configured to move from a closed condition to an open direction as a function of two functions. A method for operating a uniflow large turbocharged two-stroke internal combustion engine, the engine comprising:
a plurality of cylinders each having a scavenging port at a lower end and an exhaust valve at an upper end;
an intake system having a scavenging air receiver connected to the cylinder through the scavenging port, through which scavenging air is introduced into the cylinder;
an exhaust system having an exhaust receiver connected to the cylinder through the exhaust valve, through which exhaust gas generated in the cylinder is exhausted;
an exhaust-driven turbine coupled to the compressor to operate the compressor; an inlet of the turbine connected to the exhaust system; and an outlet of the compressor for pressurizing the scavenging air receiver. a plurality of turbochargers each having an outlet connected to the intake system for delivering a scavenging air flow;
Equipped with
At least one of the plurality of turbochargers is a turbocharger that can be selectively activated and stopped, and the turbocharger that can be selectively activated and stopped is
a turbine that is selectively connected to the exhaust receiver by an electronically controlled turbine control valve and that can be activated and deactivated;
A compressor that can be started and stopped,
has
The outlet of the actuatable compressor is selectively connected to the intake system by an electronically controlled compressor control valve and connected to the outlet of the actuatable compressor upstream of the compressor control valve. connected to outside air through an electronically controlled air bleed valve.
the air bleed valve is a variable valve that forms a controllable variable restriction on the flow of gas through the air bleed valve;
The method includes:
measuring or estimating at least one of the pressure at the outlet of the actuable/stoppable compressor and the rotational speed of the selectively actuable/stoppable turbocharger;
starting the at least one selectively actuable/deactivable turbocharger,
- Shifting the turbine control valve from a closed state to an open state,
- Shifting the compressor control valve from a closed state to an open state,
- the air bleed valve is activated while starting the at least one selectively actuatable/deactivable turbocharger;
- the measured or estimated pressure at the outlet of the actuatable compressor;
- the measured or estimated rotational speed of the turbocharger that can be selectively activated and deactivated;
continuously transitioning from an open state to a closed state as a function of at least one of
to start by;
including methods. stopping the at least one selectively actuable/stoppable turbocharger,
- Shifting the compressor control valve from an open state to a closed state,
- Shifting the turbine control valve from an open state to a closed state,
・The air bleed valve is
- the measured and/or estimated pressure at the outlet of the actuatable compressor;
- the measured and/or estimated rotational speed of the selectively actuable/stoppable turbocharger;
continuously transitioning from a closed state to an open state as a function of at least one of
16. The method of claim 15, comprising stopping by.

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