KR20230151893A - Large turbocharged two-stroke internal combustion engine with turbochargers and method of operating such engine - Google Patents

Abstract

A plurality of turbochargers (5), at least one of which is a selectively activatable turbocharger (5), a selectively activatable turbocharger (5) by activating and deactivating the selectively activatable turbocharger (5) at relatively high engine loads. A single-flow type large turbocharged two-stroke internal combustion engine (100) is provided, including a controller (50) configured to reduce the risk of surging or stalling and a method for operating such an engine.

Description

LARGE TURBOCHARGED TWO-STROKE INTERNAL COMBUSTION ENGINE WITH TURBOCHARGERS AND METHOD OF OPERATING SUCH ENGINE}

The present invention relates to a large turbocharged two-stroke internal combustion engine and a method equipped with a plurality of exhaust-driven turbochargers for supplying scavenging air, and a method of operating such an engine.

Large turbocharged two-stroke internal combustion engines are commonly used as propulsion systems for large ships or as prime movers in power plants. Their enormous size, weight and power output make these engines completely different from conventional combustion engines, putting large two-stroke turbocharged compression internal combustion engines in a class unto themselves. The height of these engines is generally not critical, so they are constructed with a crosshead to avoid side loads on the pistons. Typically, these engines run on natural gas, petroleum gas, methanol, ethane or fuel oil (heavy oil).

Large turbocharged two-stroke internal combustion engines can be operated with compression ignition, i.e. according to the diesel principle, or as premix engines, i.e. according to the Otto principle, with scavenge gases flowing from bottom dead center (BDC) to top dead center. During the piston's stroke up to (TDC), the scavenge gases are mixed with the fuel.

In these engines, optimizing turbocharger performance for a single engine load is relatively simple. However, large turbocharged two-stroke internal combustion engines must operate over a wide range of engine loads and operating conditions, and when equipped with a single (non-variable geometry) turbocharger, it is difficult to achieve optimal turbocharger efficiency over a wide range of engine loads. Variable geometry turbochargers can alleviate some problems, but have other drawbacks such as increased cost, maintenance and complexity. Being able to increase scavenging pressure at part load has proven useful, especially when optimizing engine efficiency at part load. As a result, it became common to use exhaust gas bypasses to influence scavenge pressure. This effect is achieved by matching the turbocharger to a specific pressure at 100% load using an open bypass. Because some of the exhaust gases bypass the turbocharger's turbine, power to the turbocharger is reduced as a result. From a cylinder perspective, this is equivalent to installing a low-efficiency turbocharger, which in turn has a negative impact on scavenging performance. However, when the bypass is closed at part load, the turbocharger's turbine takes all the available exhaust gas mass flow and converts it to a higher air mass flow, creating a higher scavenge pressure at part load. However, a reduction in scavenging at high engine loads is clearly undesirable. One way to avoid this problem is to equip multiple turbochargers and selectively use one or more turbochargers to use a selected portion of the total turbocharging capacity in a way that provides the best performance at the actual engine load. By selectively activating and deactivating the turbocharger, the active turbocharger always gets all the exhaust power and prevents deterioration of scavenging air quality at high loads. The turbochargers that are activated and deactivated do not necessarily have to be the same size (capacity) as the remaining turbochargers (the remaining turbochargers are always the activated turbochargers). The relative size/capacity of the turbocharger or turbochargers that are selectively activated and deactivated is selected depending on the desired magnitude of effect on scavenging pressure.

Therefore, when multiple turbochargers are fitted and the number of operating turbochargers is controlled, high turbocharger efficiencies can be achieved over a wide range of engine loads, resulting in improved fuel efficiency compared to a single (non-variable geometry) turbocharger, and thus engine operating costs. and environmental load is reduced.

When the turbocharger is disabled, 100% engine load is not necessarily possible. The remaining active turbochargers or turbochargers do not have sufficient capacity to handle the entire exhaust gas volume. This means that when increasing engine load to full engine load, the turbocharger must be activated at relatively high loads, typically between 50% and 75% of maximum engine load (maximum continuous rating). The same applies to the reverse process of deactivating the turbocharger, which generally has to be performed at similar or identical, relatively high engine loads.

However, in practice, activating or deactivating the turbocharger at high engine loads has proven difficult due to the importance of maintaining the compressor operating point within the compressor diagram of the turbocharger compressor during cut-in and cut-out. If the turbocharger speed becomes too low compared to the current pressure ratio, the compressor will be pushed into a surge/stall state. Surging is a failure of normal flow in a compressor, usually occurring at low flow rates. Surging occurs when the compressor operates outside of its design point and affects the entire turbocharger, which is aerodynamically and mechanically undesirable. The turbocharger may be damaged. As a result, high temperatures and high vibrations occur and flow reversals occur. In other words, the flow reverses and exits the compressor silencer. This places a high load on the mechanical parts of the turbocharger. A single surge/stall is not necessarily critical to a turbocharger, but over time, many surges can compromise the stability of the turbocharger.

This problem has not been solved in this field of technology. In other words, it was not possible to keep the compressor operating point at the desired location or region on the compressor diagram, so this problem in this field of technology meant activating the turbocharger at relatively low engine loads, typically around 10% or less of maximum continuous rating. and was avoided by disabling it. However, this means that the engine load must be reduced by up to 10% each time the turbocharger is activated or deactivated, which is very undesirable in practice and, for example, if the engine is used as the main propulsion in an ocean-active vessel, the engine load may be reduced by 65%. It is undesirable to have to reduce the engine load by 10% before it can operate above 10%.

No. US2010/0281862 discloses a marine engine equipped with multiple turbochargers, wherein the turbochargers are switched from single operation to parallel operation or from parallel operation to single operation, and surging in the turbochargers being started or stopped is prevented. insist. A marine diesel engine has an exhaust manifold mounted on the engine body, an exhaust pipe in communication with the turbine section, a turbine inlet valve connected somewhere in the exhaust pipe, a supply pipe in which the compressor section communicates with a supply manifold mounted on the engine body, and a compressor section connected to somewhere in the supply pipe. A check valve that opens when the outlet pressure reaches or exceeds the outlet pressure of the compressor section, an air vent pipe whose end is connected somewhere in the supply pipe between the compressor section and the check valve, and an air vent valve connected somewhere in the air vent pipe. Includes. The air vent valve closes when the turbine inlet valve almost reaches the open position when the turbocharger starts, and the air vent valve opens just before the turbine inlet valve closes when the turbocharger stops. However, tests by the inventors of the present invention have shown that turbocharger surging is not reliably prevented according to the teachings of US2010/0281862.

No. JPWO2015162840A1 discloses an engine system that starts with the main supercharger and the auxiliary supercharger in operation, closes the auxiliary turbine inlet valve and auxiliary compressor outlet valve, and stops the auxiliary supercharger while operating the main supercharger; When reducing the number of operating superchargers, a standard pressure at stop with a predetermined surge margin is determined based on the rotation speed of the auxiliary supercharger. If the outlet pressure of the auxiliary compressor is higher than the standard pressure at stop, the blow-off valve opens and the outlet pressure of the auxiliary compressor is When stopped, if the pressure is lower than the reference pressure, the blow-off valve closes.

The object of the present invention is to provide a large turbocharged two-stroke internal combustion engine of the single-flow type that allows activation and deactivation of the turbocharger while minimizing the risk of surging/stalling of the turbocharger at relatively high engine loads.

The above-described objectives and other objectives are achieved by aspects of the present disclosure. Additional possible implementation forms are apparent from the detailed description and drawings.

According to a first aspect, a single-flow type large turbocharged two-stroke internal combustion engine is provided, the internal combustion engine comprising:

A plurality of cylinders with scavenging ports at the bottom and exhaust valves at the top;

An intake system through which scavenge gas is introduced into the cylinder, the intake system comprising a scavenge gas receiver connected to the cylinder through a scavenge port;

An exhaust system through which exhaust gas generated in a cylinder is exhausted, including an exhaust gas receiver connected to the cylinder through an exhaust valve;

Each turbocharger has an exhaust gas driven turbine operably coupled to a compressor, the inlet of the turbine connected to the exhaust gas receiver and the outlet of the compressor to the intake system for delivering a flow of pressurized scavenge gas to the scavenge gas receiver. As a plurality of turbochargers connected,

At least one of the plurality of turbochargers is a turbocharger that can be selectively activated, and the turbocharger that can be selectively activated is:

an activatable turbine selectively connected to the exhaust gas receiver via an electronically controlled turbine control valve;

an activatable compressor having an outlet selectively connected to an intake system by an electronically controlled compressor control valve and an outlet selectively connected to atmosphere by an electronically controlled air discharge valve connected to an outlet of the activatable compressor upstream of the compressor control valve;

a plurality of turbochargers, the air discharge valve being a variable valve forming a variable restriction capable of controlling gas flow through the air discharge valve; and

A controller coupled to the turbine control valve, compressor control valve and air discharge valve;

The controller is configured to:

When activating a selectively activateable turbocharger,

Move the turbine control valve from closed to open,

Move the compressor control valve from closed to open,

As a function of at least one of the measured or estimated pressure at the outlet of the activatable compressor and the measured or estimated rotational speed of the selectively activatable turbocharger, the air valve continues to move in a closed state.

The outlet pressure of the activatable compressor can be controlled by continuously moving the air discharge valve from open to closed according to a function, so that the pressure ratio for the activatable compressor is at a level that ensures the compressor operating point, which is defined by the combination of the pressure ratio for the compressor. can be controlled, and the turbocharger/compressor speed is the distance to the operating point where the compressor surges/stalls. This means there is a surge/stall margin, which greatly reduces the risk of compressor surging/stalling while the energizable compressor is active.

In a possible implementation of the first aspect, the function is derived from an operating point for the activatable compressor that is known to be at a safe distance from surging or stalling.

In a possible implementation form of the first aspect the function is derived from a compressor characteristic, such as a compressor characteristic defined in a compressor diagram associated with an activatable compressor.

By controlling the pressure at the outlet of the activatable compressor as a function derived from the compressor diagram, it becomes possible to control the starting of the turbocharger in a way that prevents or at least reduces the occurrence of stalls and/or surges.

In a possible implementation form of the first aspect, the controller is configured to:

When deactivating the optionally activated turbocharger (5):

Move the compressor control valve from open to closed,

Move the turbine control valve from open to closed (preferably after the compressor control valve is closed),

The air discharge valve is moved to the open state as a function of at least one of the measured and/or estimated pressure at the outlet of the activatable compressor and the measured and/or estimated rotational speed of the optionally activatable turbocharger (5).

By continuously moving the air discharge valve from closed to open according to a function, the outlet pressure of the activatable compressor can be controlled, thereby controlling the pressure ratio for the activatable compressor at a level that ensures the compressor operating point, which is defined by the combination of pressure ratios. The turbocharger speed is a function of the distance to the operating point where the compressor surges/stalls. This means there is surge/stall margin, which greatly reduces the risk of compressor surging/stalling while an activatable compressor is deactivated.

In a possible implementation form of the first aspect, the controller receives information of a target pressure for a given rotational speed of the activatable turbocharger at the outlet of the selectively activatable compressor for a range of rotational speeds of the selectively activatable turbocharger.

In a possible implementation form of the first aspect, the controller selectively moves the air discharge valve to a position that generates an actual pressure at the outlet of the activatable compressor corresponding to a target pressure for the actual rotational speed of the activatable turbocharger. By ensuring that the actual pressure at the activatable compressor outlet matches the target pressure, the operating point can be maintained in the optimal position (corresponding to the highest compressor efficiency). Additionally, by maintaining the operating point of the activatable compressor at or near the optimal operating position, the risk of stalling is greatly reduced.

In a possible implementation form of the first aspect, the target pressure for a given rotational speed of the selectively activatable turbocharger is separated by a surge margin from the pressure at which the activatable compressor surges at the same given rotational speed of the selectively activatable turbocharger. .

In a possible implementation form of the first aspect, the target pressure at a given rotational speed of the selectively activatable turbocharger corresponds to the pressure at which the activatable compressor has the highest efficiency at the same given rotational speed of the selectively activatable turbocharger.

In a possible implementation of the first aspect, the engine may include a pressure sensor configured to provide a signal indicative of the pressure at the outlet of the activatable compressor and/or a speed sensor configured to provide a signal indicative of the rotational speed of the selectively activatable turbocharger. Includes.

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

In a possible implementation of the first aspect, the controller is configured to determine a difference between the target pressure and the signal of the pressure sensor and determine a set point for the air exhaust valve as a function of the difference.

In a possible implementation of the first aspect, 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.

In a possible implementation form of the first aspect, the turbine control valve is disposed upstream of the activatable turbine and/or the compressor control valve is disposed downstream of the activatable compressor and/or the air discharge valve is selectively activated. is placed in the air discharge conduit downstream of the compressor and upstream of the compressor control valve.

In a possible implementation form of the first aspect, the estimated pressure and/or the estimated rotational speed of the selectively activatable turbocharger are pre-stored values derived from one or more tests and/or simulations or experience.

In a possible implementation of the first aspect, the engine includes a fuel system for delivering fuel to the cylinders.

In a possible implementation of the first aspect, the turbine control valve is configured to control exhaust gas flow to the activatable turbine.

In a possible implementation of the first aspect, the compressor control valve is configured to control the flow of scavenge gas from the activatable compressor to the scavenge gas receiver.

In a possible implementation of the first aspect, a pressure sensor for detecting the scavenging gas pressure in the scavenging gas receiver and/or an observer for estimating the scavenging gas pressure in the scavenging gas receiver.

In a possible implementation form of the first aspect, the controller is configured to selectively activate and deactivate the activatable turbocharger as a function of engine operating conditions, preferably as a function of engine load, scavenging pressure or load set point.

In a possible implementation of the first aspect, the controller is configured to determine the actual engine turbocharging effect as a function of the sensed or observed scavenge gas pressure and/or the sensed or observed exhaust gas temperature. The term "engine turbocharging effect" refers to the effect experienced or felt by the engine independent of ambient conditions.

In a possible implementation form of the first aspect, the compressor control valve is a variable valve that forms a controllable variable restriction to the flow of gas through the compressor control valve, the controller being activated upon activating the selectively activatable turbocharger (5). It is configured to move the compressor control valve 36 into the open state as a function of both a measured or estimated pressure at the outlet of the compressor and a measured or estimated rotational speed of the selectively activatable turbocharger.

According to a second aspect, a method of operating a large turbocharged two-stroke internal combustion engine of a single flow type is provided,

The internal combustion engine is,

A plurality of cylinders with scavenging ports at the bottom and exhaust valves at the top;

An intake system through which scavenge gas is introduced into the cylinder, the intake system comprising a scavenge gas receiver connected to the cylinder through a scavenge port;

An exhaust system through which exhaust gas generated in a cylinder is exhausted, including an exhaust gas receiver connected to the cylinder through an exhaust valve; and

Each turbocharger having an exhaust gas driven turbine operably coupled to a compressor, the inlet of the turbine connected to the exhaust gas receiver and the outlet of the compressor connected to the intake system for delivering a flow of pressurized scavenge gas to the scavenge gas receiver. As a plurality of turbochargers ,

At least one of the plurality of turbochargers is a turbocharger that can be selectively activated, and the turbocharger that can be selectively activated is:

an activatable turbine selectively connected to the exhaust gas receiver via an electronically controlled turbine control valve;

an activatable compressor having an outlet selectively connected to an intake system by an electronically controlled compressor control valve and an outlet selectively connected to atmosphere by an electronically controlled air discharge valve connected to an outlet of the activatable compressor upstream of the compressor control valve;

The air exhaust valve includes a plurality of turbochargers, the variable valves forming variable restrictions capable of controlling gas flow through the air exhaust valve,

The above method is,

measuring or estimating at least one of a pressure at the activatable compressor outlet and a rotational speed of the selectively activatable turbocharger; and

Activating the turbine control valve from closed to open,

Activating the compressor control valve from closed to open (preferably after the turbine control valve is closed),

at least one optionally by continuously moving the air discharge valve from a closed state to an open state as a function of at least one of the measured or estimated pressure at the outlet of the activatable compressor and the measured or estimated rotational speed of the optionally activatable turbocharger; activating an activatable turbocharger.

In a possible implementation form of the second aspect, the method includes:

Move the compressor control valve from open to closed,

Move the turbine control valve from open to closed (preferably after the compressor control valve is closed),

at least one optionally by continuously moving the air discharge valve from an open to a closed state as a function of at least one of the measured or estimated pressure at the outlet of the activatable compressor and the measured or estimated rotational speed of the optionally activatable turbocharger; and deactivating an activatable turbocharger.

DETAILED DESCRIPTION OF THE INVENTION In the detailed section below, the disclosure, aspects, embodiments and implementations of the present invention are described in more detail with reference to exemplary embodiments shown in the drawings.
1 is an elevated front view of a large two-stroke internal combustion engine equipped with multiple turbochargers according to an exemplary embodiment.
Figure 2 is an elevated side view of the large two-stroke internal combustion engine of Figure 1.
Figure 3 is a schematic diagram of the large two-stroke internal combustion engine according to Figure 1 (only one of the plurality of turbochargers is shown in Figure 3 to keep the drawing as simple as possible).
Figures 4 and 5 are graphs showing scavenging pressure, valve behavior and stall margin during testing.
Figure 6 is a control diagram of the Figure 1 engine.
7 is a schematic diagram of an embodiment of a large two-stroke internal combustion engine with two turbochargers.
Figures 8-10 are graphs showing examples of scavenge pressure, working line set point, actual working line, valve behavior and surge margin for the engine according to Figure 1;
Figure 11 is a schematic diagram of another large two-stroke internal combustion engine embodiment with three turbochargers.

1, 2 and 3 show a large, low-speed turbocharged two-stroke diesel engine 100 equipped with a crankshaft 8 and a crosshead 9. Figure 3 shows a schematic diagram of a large low-speed turbocharged two-stroke diesel engine with intake and exhaust systems. In this exemplary embodiment, the engine 100 is equipped with six cylinders 1 in a row. A large, low-speed turbocharged two-stroke diesel engine is typically supported by a cylinder frame 23, which is supported by an engine frame 11, and has 4 to 14 cylinders 1 in a row. This engine 100 can be used, for example, as a stationary engine that operates the main engine of a ship or a generator of a power plant. The total output of this engine 100 may range, for example, from 1,000 to 110,000 kW.

The engine 100 is, in this exemplary embodiment, a two-stroke single-flow type equipped with a scavenging port 18 in the lower region of each cylinder liner 1 and a central exhaust valve 4 on top of the cylinder liner 1. Compression ignition engine 100. However, it is understood that this engine 100 need not be compression-ignited (diesel principle) and could alternatively be a premixed engine (automatic principle). Accordingly, in this embodiment, the compression pressure of engine 100 will be sufficiently high for compression ignition, but it is appreciated that engine 100 may be a premix engine that operates at lower compression pressures and is ignited by a spark or similar means. You must understand.

Scavenging air is introduced into the cylinder (1) through an intake system, which includes a scavenging gas receiver (2) connected to the cylinder (1) via a scavenging port (18).

Exhaust gas generated in the cylinder is exhausted through an exhaust system, which includes an exhaust gas receiver (3) connected to the cylinder (1) through an exhaust valve (4).

The intake system of engine 100 includes a scavenge gas or air receiver 2 (if EGR is not used, receiver 2 accepts only air, and if EGR is used, receiver 2 receives exhaust gas and scavenge air). You will receive a mixture of (hence the name scavenging gas receiver). Scavenging air passes from the scavenging gas receiver (2) to the scavenging port (18) of the individual cylinder (1). The piston 10, which reciprocates between bottom dead center (BDC) and top dead center (TDC) within the cylinder liner 1, compresses the scavenging air. Fuel is injected through fuel valves 55 disposed on the cylinder cover 22, followed by combustion and exhaust gas generation. Alternatively, a fuel valve 55 is placed in the cylinder liner and fuel is introduced during the piston stroke from BDC to TDC, the mixture of scavenge and fuel is compressed, and ignition is triggered when the piston is at or near TDC, resulting in combustion. It flows and exhaust gas is generated.

The central exhaust valve 4 is disposed in the central opening of the cylinder cover 22. A plurality (preferably three or four) of fuel valves 55 are distributed on the cylinder cover 22 around the central on-off valve 4. The exhaust valve 4 is operated by an electro-hydraulic exhaust valve actuation system controlled by a controller 50 (electronic control unit). 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 opens, the exhaust gases flow from the central opening of the cylinder cover 22 to the exhaust gas receiver 3 through an exhaust system comprising an exhaust duct connected to each cylinder 1, and then to the first exhaust gas receiver 3. flows through conduit 19 to the turbine 8 of the turbocharger 5 (the engine 100 is provided with a plurality of turbochargers 5, but not all of them are necessarily activated simultaneously), where the exhaust The gases flow through the economizer 20 to the outlet 21 and through the second exhaust conduit to the atmosphere.

Via the shaft of each turbocharger 5 the turbine 8 of the active turbocharger 5 drives a compressor 7 to which fresh air is supplied through the air inlet 12. This compressor (7) delivers pressurized scavenging air to a scavenging air conduit (13) leading to the scavenging gas receiver (2). Typically a scavenging conduit (13) is provided for each compressor (7). The scavenged air in the scavenged air conduit (13) passes through the intercooler (14) and the water mist catcher (63) to cool the scavenged air.

Engine 100 includes two or more turbochargers 5 and a controller 50. At least one of the turbochargers 5 is a selectively operated turbocharger 5. The controller 50 is configured to deactivate one or more selective turbochargers 5 below a deactivation engine load threshold so that only one turbocharger 5 with an appropriate flow area operates at low engine loads. The controller 50 is further configured to activate at least one selectively activated turbocharger 5 when the engine load is higher than the activation engine load threshold. The active and inactive engine loads can be the same or different and the flow area of the active turbocharger 5 is selected to match the engine load.

Figure 7 shows an embodiment of an engine 100 with two turbochargers 5, each in a separate scavenge string. The turbocharger 5 on the left in Figure 7 is a selectively activatable turbocharger, while the turbocharger 5 on the right in Figure 7 is always active. The selectively activated turbocharger (5) and the permanently active turbocharger (5) may have the same or different capacities. In particular, the selectively activated turbocharger 5 may have a smaller capacity than the normally active turbocharger 5. The controller 50 is configured to activate and deactivate the turbocharger 5, which is selectively activated depending on the actual operating conditions of the engine, in particular the actual engine load, in order to achieve optimal turbocharging efficiency for the engine 100. .

An electronically controlled control valve (35) is arranged in the conduit connecting the inlet of the activatable turbine (8) of the selectively activated turbocharger (5) to the exhaust gas receiver (3). The control valve 35 is connected to the controller 50 and the position of the control valve 35 is controlled by the controller 50 through signals to the turbine control valve 35. Via the control valve 35 the controller 50 enables or disables the exhaust gas flow from the exhaust gas receiver 3 to the inlet of the activatable turbine 8.

An electronically controlled compressor control valve (36) connects the outlet of the activatable compressor (7) of the selectively activated turbocharger (5) to the scavenge gas receiver (2) via the scavenge cooler (14) and moisture remover (63). placed in the conduit. Compressor control valve 36 is connected to controller 50 and the position of compressor control valve 36 is controlled by controller 50 through signals to compressor control valve 36. Via the compressor control valve 36 the controller 50 can enable and disable the flow of scavenge air from the outlet of the activatable compressor 7 to the scavenge gas receiver 2 .

At least the selectively activated turbocharger 5 is provided with a rotational speed sensor that generates a signal indicative of the rotational speed of the selectively activated turbocharger 5 and this signal is transmitted to the controller 50 . A pressure sensor 33 is arranged to measure the pressure at the outlet of the activatable compressor 7 . Pressure sensor 33 is placed upstream of compressor control valve 36. The signal from the pressure sensor 33 is transmitted to the controller 50.

The electronically controlled air discharge valve 37 is provided at the outlet of the activatable compressor 7 and, for example, in an atmosphere or other environment having a pressure substantially equal to atmospheric pressure, for example downstream of the exhaust system of the turbocharger 5 or a selectively activatable compressor 7. ), the air discharge valve 37 is fluidically connected to the outlet of the compressor 7 , which is activatable upstream of the compressor control valve 36 . Preferably, the air discharge valve 37 is arranged in an air discharge conduit 39 branching from the conduit connecting the outlet of the activatable compressor 7 to the compressor control valve 36 . The air discharge valve 37 is a variable valve that forms a variable restriction that can control the flow of gas through the air discharge valve 37. Accordingly, the controller 50 controls the restriction of air flowing through the air discharge valve 37 by adjusting the position of the air discharge valve 37.

4 and 5 show the results of an attempt to activate and deactivate the selectively activated turbocharger 5 using only the control valve (TCV) and compressor control valve 36 (CCV). Figure 4 is a diagram showing the scavenge pressure (bar) in the scavenge gas receiver 2 versus time. Figure 5 is a diagram showing the opening and closing of the control valve 35 and the compressor control valve 36 with respect to time, where 0 on the vertical axis corresponds to a fully closed valve and 1 on the vertical axis corresponds to a fully open valve. The stall margin is also shown in Figure 5. Stall margin is an indicator of how close the compressor is to stall. Figure 5 clearly shows that in the time range of about 4 to 13 seconds after opening control valve 35 at compressor control valve 36, the stall margin is negative, resulting in compressor stalling. Different opening profiles for the control valve (35) and compressor control valve (36) respectively, without resulting in the surge/stall margin being maintained above zero during activation and deactivation of the selectively activatable turbocharger (5). An attempt was made with timing.

Compressor efficiency can be described by a constant efficiency line in a diagram (compressor diagram) where the pressure ratio for the compressor 7 is shown relative to the air flow through the compressor 7. The constant efficiency line is an elliptical curve in this compressor diagram where the efficiency of compressor 7 remains constant. The pressure ratio is the ratio of the outlet pressure of the compressor (7) divided by the inlet pressure of the compressor (7). Since the pressure at the inlet of the compressor 7 is substantially equal to atmospheric pressure, which can be assumed to be substantially constant, only the pressure at the outlet of the compressor 7 is measured for the controller 50 to determine the pressure ratio for the compressor 7. It should be determined by estimation (e.g. using a pressure sensor) or by estimation (e.g. using an observer). The air flow through the compressor 7 is difficult to measure directly, but in one embodiment 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 one embodiment, the optimal pressure ratio for the activatable compressor 7 resulting in the highest compressor efficiency for the rotational speed of the turbocharger 5 to be selectively activated over a range of turbocharger speeds is, for example, an optimal pressure ratio. It is stored in the controller 50 as a working line that can be displayed on a diagram plotted against turbocharger speed.

In another embodiment, the optimal pressure at the outlet of the activatable compressor 7 that results in the highest compressor efficiency for the rotational speed of the turbocharger 5 to be selectively activated over a range of turbocharger speeds is determined by the controller 50 This is because the (atmospheric) pressure at the inlet of the activatable compressor 7 is known and constant.

Figure 6 shows a control diagram for controlling the positions of control valve 35 (TCV), compressor control valve 36 (CCV) and air discharge valve 37 (ARV). The measured or estimated rotational speed of the turbocharger 5 is provided to a target pressure estimator, which may be a separate control device or part of the controller 50 . The target pressure estimator calculates the optimal pressure at the outlet of the activatable compressor 7 for the actual turbocharger speed, for example using the stored work lines mentioned above. The target pressure is compared to the actual pressure measured or determined at the outlet of the activatable compressor 7 to determine the difference between the two signals. This difference is transmitted to the valve controller. The valve controller may be a separate controller or part of controller 50. Accordingly, the valve controller adjusts the position of the air discharge valve 37. For control of the air discharge valve 37, for increasing the restriction on the flow imposed by the air discharge valve 37 when the pressure at the outlet of the activatable compressor 7 is lower than the target pressure and for the activatable compressor 7 To reduce the restriction on the flow imposed by the air discharge valve 37 when the pressure at the outlet of the ) can be. Therefore the turbocharger 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 one embodiment, the valve controller controls the opening and closing of the control valve 35 and compressor control valve 36 according to a predetermined profile and sequence. The profiles or lines of operation for activating the selectively activated turbochargers 5 and for deactivating the selectively activated turbochargers 5 may be determined by testing or simulation and these predetermined profiles and sequences are provided to the controller 50. It is saved.

Figure 8 shows an example of the resulting valve behavior versus times for activating and deactivating the turbocharger 5, which is selectively activated while the engine is operating at 50% engine load (50% of maximum continuous rating). The selectively activatable turbocharger 5 is activated, for example, when the engine load exceeds an engine load threshold. In this example the controller 50 is configured to activate the selectively activatable turbocharger 5 by moving the control valve 35 from fully closed to fully open. The controller 50 is configured to move the compressor control valve 36 from the fully closed position to the fully open position for a certain period of time after the control valve 35 is opened. This is not a fixed, predetermined time range. The compressor control valve 36 opens when the pressure set point no longer increases. The time at which this occurs depends on the acceleration of the turbocharger (5). The air outlet valve 37 starts in the open position and closes according to the control method described above, i.e. as a function of the rotational speed of the selectively activatable turbocharger 5 and the activatable outlet pressure of the compressor 7 . The function is determined by the compressor characteristics, which can be explained as described above. For example, using a compressor diagram, the operating point is determined from the speed of the energizable compressor in combination with the pressure at the outlet of the energizable compressor (7) so that the compressor can function optimally (at high efficiency) or at least without risk of stall/surge. Allow.

In this example, compressor control valve 36 opens after control valve 35. However, it is pointed out that this is not necessarily always the case and will vary depending on the environment, particularly the acceleration of the turbocharger (5).

The selectively activatable turbocharger 5 is deactivated, for example, when the engine load falls below an engine load threshold (which may be different from the engine load threshold for activating the selectively activatable turbocharger 5). In this example, the controller 50 is configured to initiate the process of deactivating the selectively activatable turbocharger 5 by moving the compressor control valve 36 from fully open to fully closed. The controller 50 is configured to move the compressor control valve 36 from the fully closed position to the fully open position for a certain period of time after the control valve 35 is opened. The air outlet valve 37 starts from the closed position and opens according to the control method described above, i.e. as a function of the rotational speed of the selectively activatable turbocharger 5 and the activatable outlet pressure of the compressor 7 .

Figure 9 shows the resulting scavenge pressure in the scavenge gas receiver 2, the working line set point for the air exhaust valve 37 and the actual working line for the air exhaust valve 37 against time. Figure 10 shows the surge margin versus time and shows that the surge margin is positive both during activation of the selectively activated turbocharger 5 and during deactivation of the optionally activated turbocharger 5, thus significantly reducing the risk of surges. It shows that it is done. Surge margin is an indicator of how close the compressor 7 is to surging.

Accordingly, the controller can adjust the position of the air discharge valve in such a way that the actual pressure at the outlet of the activatable compressor 7 is kept close to the target pressure along the peak efficiency line of the activatable compressor 7.

The behavior of the selectively activated turbocharger 5 can be predicted on the basis of tests of the engine on a test bed and/or computer simulation, so that a suitable opening curve for the air discharge valve 37 can be determined by varying the turbocharger speed and/or The pressure at the outlet of the activatable compressor 7 can be measured in real time or based on stored data without having to be determined. Here, the controller 50 may be provided with one or more working lines for opening the air discharge valve 37 . Preferably, each of these curves is suitable for a specific engine load.

In one embodiment, compressor control valve 36 is a variable valve that creates a controllable variable restriction to the flow of gas through compressor control valve 36. In this embodiment the activatable compressor (7) upon activating the selectively activatable turbocharger (5) to assist the air discharge valve (37) in the task of controlling the pressure at the outlet of the selectively activatable compressor (7). As a function of both the measured or estimated pressure at the outlet of the turbocharger 5 and the measured or estimated rotational speed of the selectively activatable turbocharger 5, the controller 50 moves the compressor control valve 36 from the closed state to the open state. It is composed of:

11 is a schematic diagram of an engine 100 according to another embodiment comprising two normally active turbochargers 5 and one selectively activated turbocharger 5 . In this embodiment, structures and features that are the same or similar to corresponding structures and features previously described or shown herein are denoted by the same reference numerals as previously used for simplicity. Apart from the additional always active turbocharger 5 the engine 100 according to the present embodiment is essentially the same as the engine described above. Due to the additional always active turbocharger, the engine load at which the selectively activatable turbocharger 5 is activated and the engine load at which the selectively activatable turbocharger 5 is deactivated are different from the above-described engine. The engine load at which the selectively activated turbochargers 5 are activated and deactivated will vary depending on the capacity and characteristics of each turbocharger 5.

Various methods and engines have been described in connection with various embodiments herein. However, other modifications to the disclosed embodiments may be understood and made by those skilled in the art when practicing the claimed subject matter upon study of the drawings, disclosure, and appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "one" or "an" do not exclude a plurality. A single controller or other unit may not exclude multiple items or steps recited in the claims. The mere fact that certain measures are recited in different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Reference signs used in the claims should not be construed as limiting the scope. Unless otherwise indicated, the drawings are intended to be read in conjunction with the specification (e.g., cross-hatching, part placement, scale, scale, etc.) and are to be considered a part of the entire written description of the present disclosure. As used in the description, the terms “horizontal,” “vertical,” “left,” “right,” “top,” and “bottom” refer to the orientation of the depicted structure as the particular shape is facing the reader.

Claims (16)

In the uniflow type large turbocharged two-stroke internal combustion engine (100),
A plurality of cylinders (1) with a scavenging port (18) at the bottom and an exhaust valve (4) at the top;
an intake system through which scavenge gas is introduced into the cylinder (1), comprising a scavenge gas receiver (2) connected to the cylinder (1) via the scavenge port (18);
An exhaust system through which exhaust gas generated in the cylinder (1) is exhausted, the exhaust system including an exhaust gas receiver (3) connected to the cylinder (1) through the exhaust valve (4);
Each turbocharger (5) has an exhaust gas driven turbine (8) operably coupled to a compressor (7), said turbine (8) for delivering a flow of pressurized scavenge gas to said scavenge gas receiver (2). A plurality of turbochargers (5), the inlet of which is connected to the exhaust gas receiver (3) and the outlet of the compressor (7) is connected to the intake system,
At least one of the plurality of turbochargers (5) is a selectively activatable turbocharger (5), and the selectively activatable turbocharger (5) is,
an activatable turbine (8) selectively connected to said exhaust gas receiver (3) via an electronically controlled turbine control valve (35) and
An electronically controlled air discharge valve (37), its outlet selectively connected to the intake system by an electronically controlled compressor control valve (36), and connected upstream of the compressor control valve (36) to the outlet of the activatable compressor (7). ) with an activatable compressor (7), the outlet of which is selectively connected to the atmosphere by
The air release valve 37 includes a plurality of turbochargers 5, which are variable valves that form variable restrictions capable of controlling the flow of gas through the air release valve 37; and
It includes a controller 50 coupled to the turbine control valve 35, the compressor control valve 36, and the air discharge valve 37,
The controller 50,
When activating the selectively activatable turbocharger (5),
Moving the turbine control valve 35 from a closed state to an open state,
Moving the compressor control valve 36 from a closed state to an open state,
With the air discharge valve (37) open, as a function of both the measured or estimated pressure at the outlet of the activatable compressor (7) and the measured or estimated rotational speed of the selectively activatable turbocharger (5). A large turbocharged two-stroke internal combustion engine that moves continuously in a closed state. According to paragraph 1,
The controller 50,
When deactivating the selectively activated turbocharger (5),
Activating the compressor control valve (36) from an open state to a closed state,
Activating the turbine control valve (35) from an open state to a closed state,
pressure measured or estimated at the outlet of said activatable compressor (7) and
As a function of at least one of the measured or estimated rotational speeds (5) of the selectively activatable turbocharger (5),
A large turbocharged two-stroke internal combustion engine (100) that continuously moves the air discharge valve (37) in an open state. According to paragraph 1,
The controller 50,
Large turbocharging, which is informed of a target pressure for a given rotational speed of the selectively activatable turbocharger (5) at the outlet of the activatable compressor (7) for a range of rotational speeds of the selectively activatable turbocharger (5). Two-stroke internal combustion engine (100). According to paragraph 3,
The controller is,
moving the air discharge valve (37) to a position where the actual pressure at the outlet of the activatable compressor (7) corresponds to the target pressure for the actual rotational speed of the selectively activatable turbocharger (5). Charging two-stroke internal combustion engine (100). According to paragraph 3,
The target pressure for a given rotational speed of the selectively activatable turbocharger 5 is:
A large turbocharged two-stroke internal combustion engine (100), wherein the activatable compressor (7) is separated by a surge margin from the pressure surge at the same given rotational speed of the selectively activatable turbocharger (5). According to paragraph 3,
The target pressure at a given rotational speed of the selectively activatable turbocharger 5 is:
A large turbocharged two-stroke internal combustion engine (100), wherein the activatable compressor (7) corresponds to a pressure at which it has highest efficiency at the same given rotational speed of the selectively activatable turbocharger (5). According to paragraph 3,
a pressure sensor (33) configured to provide a signal indicative of the pressure at the outlet of the activatable compressor (7); and
of a speed sensor configured to provide a signal indicative of the rotational speed of the selectively activatable turbocharger (5).
A large turbocharged two-stroke internal combustion engine 100, comprising at least one. In clause 7,
The controller 50,
A large turbocharged two-stroke internal combustion engine (100) configured to determine the target pressure based on a signal from the speed sensor. According to clause 8,
The controller 50,
determine the difference between the target pressure and the signal from the pressure sensor 33;
A large turbocharged two-stroke internal combustion engine (100) configured to determine a set point for the air outlet valve (37) as a function of the difference. According to clause 9,
The controller 50,
A large turbocharged two-stroke internal combustion engine (100) configured to determine a set point for the turbine control valve (35) and/or the compressor control valve (36) as a function of the difference. According to paragraph 1,
The turbine control valve 35 is,
arranged upstream of the activatable turbine (8), and/or
The compressor control valve 36 is,
arranged downstream of said activatable compressor (7);
The air discharge valve 37 is,
A large turbocharged two-stroke internal combustion engine (100) disposed in an air exhaust conduit (39) downstream of a compressor (7) and upstream of the compressor control valve (36) of the selectively activated turbocharger (5). According to paragraph 1,
A pressure sensor 34 for detecting the scavenge gas pressure in the scavenge gas receiver 2 and/or
A large turbocharged two-stroke internal combustion engine (100) comprising an observer for estimating the scavenge pressure in the scavenge gas receiver (2). According to paragraph 1,
The controller 50,
A large turbocharged two-stroke internal combustion engine (100) configured to activate and deactivate the selectively activatable turbocharger (5) as a function of the engine operating conditions. The compressor control valve 36 is,
a variable valve that creates a controllable variable restriction to the flow of gas through the compressor control valve (36),
The controller 50,
When activating the selectively activatable turbocharger (5),
pressure measured or estimated at the outlet of said activatable compressor (7) and
As two functions of the measured or estimated rotational speed of the selectively activatable turbocharger (5),
A large turbocharged two-stroke internal combustion engine (100) configured to move the compressor control valve (36) from a closed state to an open state. In the operating method of a single-flow type large turbocharged two-stroke internal combustion engine (100),
The internal combustion engine is,
A plurality of cylinders (1) with a scavenging port (18) at the bottom and an exhaust valve (4) at the top;
an intake system through which scavenge gas is introduced into the cylinder (1), comprising a scavenge gas receiver (2) connected to the cylinder (1) via the scavenge port (18);
An exhaust system through which exhaust gas generated in the cylinder (1) is exhausted, the exhaust system including an exhaust gas receiver (3) connected to the cylinder (1) through the exhaust valve (4); and
Each turbocharger (5) has an exhaust gas driven turbine (8) operably coupled to a compressor (7), said turbine (8) for delivering a flow of pressurized scavenge gas to said scavenge gas receiver (2). A plurality of turbochargers (5), the inlet of which is connected to the exhaust gas receiver (3) and the outlet of the compressor (7) are connected to the intake system, and at least one of the plurality of turbochargers (5) is optionally an activatable turbocharger (5), the selectively activatable turbocharger (5) comprising an activatable turbine (8) selectively connected to the exhaust gas receiver (3) via an electronically controlled turbine control valve (35) and an electronic The outlet is selectively connected to the intake system by a controlled compressor control valve (36) and, upstream of the compressor control valve (36), to an electronically controlled air discharge valve (37) connected to the outlet of the activatable compressor (7). an activatable compressor (7) with an outlet selectively connected to the atmosphere by means of which the air discharge valve (37) is a variable valve forming a variable restriction capable of controlling the flow of gas through the air discharge valve (37). , a plurality of turbochargers (5);
The method is:
measuring or estimating at least one of a pressure at the outlet of the activatable compressor (7) and a rotational speed of the selectively activatable turbocharger (5),
Activating said at least one selectively activatable turbocharger (5),
Activating the turbine control valve (35) from a closed state to an open state,
Activating the compressor control valve (36) from a closed state to an open state,
As a function of at least one of the measured or estimated pressure at the outlet of the activatable compressor (7) and the measured or estimated rotational speed of the selectively activatable turbocharger (5), the air discharge valve (37) A method of operating a large turbocharged two-stroke internal combustion engine (100), characterized in that it is continuously moved from an open state to a closed state. According to clause 15,
Moving the compressor control valve 36 from an open state to a closed state,
Moving the turbine control valve 35 from an open state to a closed state,
pressure measured and/or estimated at the outlet of said activatable compressor (7) and
By continuously moving the air outlet valve (37) from a closed state to an open state as a function of at least one of the measured and/or estimated rotational speed (5) of the selectively activatable turbocharger (5),
A method of operating a large turbocharged two-stroke internal combustion engine (100), comprising deactivating said at least one selectively activatable turbocharger (5).