DK201970697A1

DK201970697A1 - A large low speed turbocharged two-stroke uniflow scavenge internal combustion engine with crossheads and method of operating of such engine

Info

Publication number: DK201970697A1
Application number: DKPA201970697A
Authority: DK
Inventors: Skafte Larsen Hans; Toft Tjell Peter
Original assignee: Man Energy Solutions Filial Af Man Energy Solutions Se Tyskland
Priority date: 2019-11-15
Filing date: 2019-11-15
Publication date: 2021-07-02
Also published as: DK180717B1

Abstract

A large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads (9) and method of operating such engine. The engine has a plurality of cylinders (1), having an exhaust valve (4), an exhaust valve actuation system (46) for actuating the exhaust valve (4), a fuel delivery system (30) for delivering a quantity of first fuel to the cylinder (1) concerned, a pressure sensor (42) for generating a cylinder-specific pressure signal representative of a pressure in the cylinder (1) concerned, an exhaust gas driven turbocharger (5) that pressurizes scavenging air for the cylinders (1). The method comprises closed loop controlling fuel quantity, timing of start of fuel admission/injection, and/or timing of exhaust valve closing, of the cylinders individually based on the cylinder-specific pressure signal, and on common setpoints for all cylinders, or on individual cylinderspecific setpoints that are individual cylinder-specific adjustments of the common setpoints.

Description

. DK 2019 70697 A1 A LARGE LOW SPEED TURBOCHARGED TWO-STROKE UNIFLOW

SCAVENGE INTERNAL COMBUSTION ENGINE WITH CROSSHEADS AND METHOD OF OPERATING OF SUCH ENGINE

FIELD The present disclosure relates to a large low speed turbocharged two-stroke uniflow scavenge internal combustion engine with crossheads and having a plurality of cylinders, as well as a method of operating of such engine.

BACKGROUND ART Large low speed turbocharged two-stroke uniflow scavenge internal combustion engine with crossheads are typically used 1n propulsion systems of large ships or as prime mover in power plants.

Modern engines of this type are fully electronically controlled, i.e. both the fuel admission/injection and the opening and closing of the exhaust valve can be adjusted by the electronic control system during engine operation, to ensure that the engine operates optimally under the given operating conditions.

From the factory the engine is calibrated, to ensure that the engine fulfills all performance requirements such as e.g. power, fuel efficiency, emissions, noise/vibration level and reliability.

Thus, when leaving the factory, the engine functions optimally and fulfills the performance requirements. However, wear and tear over time because the engine, or

, DK 2019 70697 A1 at least cylinders thereof to deviate from factory specification, i.e. recalibration is required.

Recently, there has been a demand for large turbocharged two-stroke compression-igniting engines to be able to handle alternative types of fuel, such as natural gas, petroleum gas, methanol, coal slurry, water-oil mixtures, petroleum coke and others. Several of these alternative fuels have the potential to reduce costs and emissions. Large low-speed uniflow turbocharged two-stroke internal combustion engines are typically used for the propulsion of large ocean going cargo ships and reliability is therefore of the utmost importance. Operation of these engines with alternative fuels is still a relatively recent development and redundancy of the operation with gaseous fuel is at a lower the level of reliability as when operating on conventional fuel. Uptime of Dual Fuel engines is lower when running on gaseous fuel by design to reduce costs. For example, redundancy is lower for the gaseous fuel system. If failure is detected on one cylinder gaseous fuel supply to all cylinders is stopped. In conventional fuel (fuel oil) mode only cylinders affected by failure are stopped. Operation on conventional fuel guaranties relatability. Thus, it is important to be able to switch fast from alternative fuel to conventional fuel, since operation on conventional fuel is considered safe fall back. Therefore, existing large low-speed two-stroke diesel engines are all dual fuel engines with a fuel system for operation on an alternative fuel such as e.g. gaseous

> DK 2019 70697 A1 fuel and another fuel system for operation with a conventional fuel, such as e.g. fuel oil so that the engine can be operated at full power running on the conventional fuel only.

It is essential to be able to promptly switch from operation on the alternative fuel to operation on the conventional fuel if there is a problem with operating on the alternative fuel, such as e.g. insufficient gas pressure when operating on a gaseous fuel. For cost savings and emission reductions it is also important to be able to switch back from the conventional fuel to the alternative fuel and a quick and easy way.

13 However, when the type of fuel is changed, the combustion process is no longer the same and the engine has to be recalibrated to the operation on the different fuel, e.g. the timing and the length of the fuel injection, the timing of the closing of the exhaust valve, the control of the scavenging pressure, compression pressure, cylinder maximum (peak) pressure and the mean indicated pressure will need to be adjusted to the type of fuel used. This means that a new process balance has to be achieved, especially since the properties (calorific value) of gaseous fuel large delivered by a typical gaseous fuel system can display large fluctuations.

Known engine control systems have not been able to perform this recalibration without human intervention in a satisfactory way. Known control systems either take too long or are insufficiently accurate to achieve optimum running conditions for the engine soon after a fuel switch.

2 DK 2019 70697 A1 Further, large low speed turbocharged two-stroke uniflow scavenge internal combustion engines are calibrated from factory in such a way that the combustion process in each of the cylinders of the engine performs in accordance with the design criteria over the full range of operating conditions of the engine.

From factory, the cylinders are balanced (load balanced), i.e. cylinder maximum (peak) or mean indicated pressure (load) of the individual cylinders is as even as possible.

Alternatively, instead of peak pressure, the mean indicated pressure for each cylinder is kept as even as possible to ensure the best possible load balance.

However, after leaving the factory wear and tear over time will affect the engine and each of the cylinders differently.

During use, the combustion process in the cylinders deviates from factory specifications and the cylinder balance deteriorates.

This development leads over time to reduced performance and increased emissions, and should be counteracted at some point in time by a recalibration of the control system.

Known control systems for large two-stroke internal combustion engines require human intervention for such recalibration.

However, manual intervention requires expert skills, since the change in one of the parameters, e.g. the closing angle of the exhaust valve will affect a range of other parameters.

Typically, the staff of the engine operator does not have the skills required to perform a recalibration that involves human intervention and for this reason such recalibration does not happen in reality.

Some of the consequences of this lack of recalibration are increased fuel consumption and emissions.

. DK 2019 70697 A1

DISCLOSURE On this background, it is an object of the present application to provide a Large low speed turbocharged two-stroke uniflow scavenge internal combustion engine and a method of operating such engine that overcomes or at least reduces the problems indicated above.

This object is according to a first aspect achieved by providing a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads, the engine comprising: a plurality of cylinders having: - an exhaust valve, - an exhaust valve actuation system for actuating the exhaust valve, - a fuel delivery system for delivering a quantity of first fuel to the cylinder concerned, - a pressure sensor for generating a cylinder-specific pressure signal representative of a pressure in the cylinder concerned, an exhaust gas driven turbocharger for pressurizing scavenging air for the cylinders, a controller in receipt of, or configured to determine for the actual operating conditions of the engine: a common torque signal representative of the torque to be delivered by the engine, a common peak pressure signal representative of the peak cylinder pressure to be realized in the cylinders, a common compression pressure signal representative of the compression pressure to be realized in the cylinders,

. DK 2019 70697 A1 the controller being in receipt of the cylinder-specific pressure signals, wherein:

a) the controller is configured to derive from the cylinder-specific pressure signal an actual cylinder-specific torque signal representative of the torque delivered by the specific cylinder concerned, and to adjust the common torque signal as a function of a deviation of the common torque signal from the actual cylinder-specific torque signal to obtain a cylinder-specific torque signal, and to deliver a quantity of fuel to the specific cylinder concerned as a function of the cylinder-

specific torque signal,

and/or b) the controller is configured to derive from the cylinder-specific pressure signal an actual cylinder-specific peak pressure signal representative of the peak pressure in the cylinder concerned (1), to adjust the common peak pressure signal as a function of a deviation of the common peak pressure signal from the actual cylinder- specific peak pressure signal to obtain a cylinder-

specific peak pressure signal, and to time the start of the delivery of the quantity of fuel to the specific cylinder (1) concerned as a function of the cylinder-specific peak pressure signal,

and/or c) the controller is configured to derive from the cylinder-specific pressure signal an actual cylinder-specific compression pressure signal representative of the compression pressure in the

; DK 2019 70697 A1 cylinder concerned, to adjust the common compression pressure signal as a function of a deviation of the common compression pressure signal from the actual cylinder-specific compression pressure signal to obtain a cylinder-specific compression pressure signal, and to time the closing the exhaust valve as a function of the cylinder-specific compression pressure signal.

By cylinder-specifically adjusting the respective combustion process parameter (s), i.e. creating a cylinder-specific torque signal, a cylinder-specific feed pressure signal and/or a cylinder-specific compression pressure signal in a feedback loop, it can be achieved that each cylinder operates exactly according to factory specification, even when wear and tear of the engine or other factors changes the operating conditions for the cylinder concerned. Simultaneously it is achieved that the control of the combustion process of the cylinders in the engine is performed without any consideration for cylinder or load balance of the cylinders of the engine as a whole. This way of controlling the engine ensures that each cylinder is operating optimally whilst there is no need to be concerned about cylinder balance (load balance). In a possible implementation of the first aspect the engine is a fuel-led and comprises at least element a).

In a possible implementation of the first aspect the engine is an air-led and comprises at least element c).

. DK 2019 70697 A1 In a possible implementation of the first aspect the engine is a partially fuel-led and partially air-led and comprises at least element a) and element c).

In a possible implementation of the first aspect the engine is a dual fuel engine and wherein the fuel delivery system is configured to handle at least two different fuels, and the cylinders each being provided with at least one fuel valve for delivering a first fuel and at least one fuel valve for delivering a second fuel. In a possible implementation of the first aspect the engine is fuel-led when operating on the first fuel and air-led when operating on the second fuel.

In a possible implementation of the first aspect the controller is in receipt of a desired engine speed and in receipt of a measured engine speed, and wherein the controller comprises a governor configured to determine a fuel index signal as a function of the deviation of the desired engine speed from the measured engine speed.

In a possible implementation of the first aspect, the controller is configured to covert the fuel index signal to the common torque signal by applying the fuel index signal to a first predetermined map.

In a possible implementation of the first aspect the controller comprises a power calculation module configured for calculating an engine load signal indicative of the engine load, the power calculation module preferably being in receipt of the fuel index signal and the measured engine speed.

2 DK 2019 70697 A1 In a possible implementation of the first aspect the controller is configured: - to determine the common peak pressure signal by applying the engine load signal to a second predetermined map, and/or to determine the common compression pressure by applying the engine load signal to a third predetermined map.

In a possible implementation of the first aspect the controller comprises a fuel index signal to profile duration module, the profile duration module being configured to convert the fuel index signal to a common fuel delivery duration signal.

In a possible implementation of the first aspect the controller is configured to adjust the common fuel delivery duration signal as a function of a deviation of the common fuel delivery duration signal from the cylinder-specific torque signal to obtain a cylinder- specific fuel delivery duration signal.

In a possible implementation of the first aspect the controller is configured to determine a cylinder-specific injection profile as a function of the cylinder-specific torque signal or as a function of the cylinder-specific fuel delivery duration signal, and wherein the fuel delivery system delivers the quantity of fuel to the specific cylinder concerned by opening one or more fuel valves in accordance with the cylinder-specific injection profile.

In a possible implementation of the first aspect the fuel delivery system starts the delivery of the quantity of i DK 2019 70697 A1 fuel to the specific cylinder concerned by opening of one or more fuel valves in accordance with the start of the timing of the delivery of the quantity of fuel determined by the controller.

In a possible implementation of the first aspect the controller is configured: - to limit the magnitude of the adjustment of the common torque signal to a first threshold when the adjustment for the other cylinders is in the same direction and wherein the controller is configured to limit the magnitude of the adjustment of the common torque signal to a second threshold when the adjustment for the other cylinders is in an opposite direction, the second threshold being lower than the first threshold if the engine has element a), and/or to limit the magnitude of the adjustment of the common peak pressure signal to a first threshold when the adjustment for the other cylinders (1) is in the same direction and wherein the controller (55) is configured to limit the magnitude of the adjustment of the common peak pressure signal to a second threshold when the adjustment for the other cylinders (1) is in an opposite direction if the engine has element b), and/or to limit the magnitude of the adjustment of the common compression pressure signal to a first threshold when the adjustment for the other cylinders (1) is in the same direction and wherein the controller (55) is configured to limit the magnitude of the adjustment of the common compression pressure signal to a second threshold

DK 2019 70697 A1 when the adjustment for the other cylinders (1) is in an opposite direction if the engine has element Cc).

In a possible implementation of the first aspect the first, second and/or third predetermined map are preferably predetermined at the engine factory from tests of the engine concerned or of an identical or comparable engine, the first, second and/or third predetermined map are preferably comprise an algorithm and/or table.

In a possible implementation of the first aspect the common torque signal corresponds to the mean indicated cylinder pressure for all of the cylinders and wherein the cylinder-specific torque signal corresponds to the mean indicated cylinder pressure for the specific cylinder concerned.

In a possible implementation of the first aspect the controller comprises a cylinder-specific cylinder offset module for each cylinder, the cylinder-specific offset module being configured for offsetting the common torque signal, the common peak pressure signal, and/or the common compression pressure signal for a specific cylinder concerned.

In a possible implementation of the first aspect the cylinder-specific offset module is controlled manually or automatically.

In a possible implementation of the first aspect the controller is configured to control the cylinders of the engine individually without consideration for cylinder balance.

DK 2019 70697 A1 In a possible implementation of the first aspect the controller is configured to continuously calculate an error value as the difference between the cylinder- specific torque and the actual cylinder-specific torque and to apply a correction based on proportional and integral terms, if the engine has element a), the controller is configured to continuously calculate an error value as the difference between the cylinder-specific peak pressure and the actual cylinder-specific peak pressure and to apply a correction based on proportional and integral terms, if the engine has element b), the controller is configured to continuously calculate an error value as the difference between the cylinder-specific compression pressure and the actual cylinder-specific compression pressure and to apply a correction based on proportional and integral terms, if the engine has element c).

In a possible implementation of the first aspect the fuel delivery system is configured for delivering a quantity of first fuel and/or quantity of second fuel to the cylinder concerned.

According to a second aspect there is provided a method of operating a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads, the engine comprising: a plurality of cylinders having: - an exhaust valve, - an exhaust valve actuation system for actuating the exhaust valve,

i.

DK 2019 70697 A1 - a fuel delivery system for delivering a quantity of first fuel to the cylinder concerned, - a pressure sensor for generating a cylinder-specific pressure signal representative of a pressure in the cylinder concerned, an exhaust gas driven turbocharger for pressurizing scavenging air for the cylinders, the method comprising: closed loop controlling at least one combustion process parameter of the cylinders cylinder-specifically as a function of - the cylinder-specific pressure signal, and o common setpoints for all cylinders, or o cylinder-specific setpoints that are cylinder- specific offsets of the common setpoints.

By cylinder-specifically adjusting the respective combustion process parameter (s), i.e. creating a cylinder-specific torque signal, a cylinder-specific feed pressure signal and/or a cylinder-specific compression pressure signal in a feedback loop, it can be achieved that each cylinder operates exactly according to factory specification, even when wear and tear of the engine or other factors changes the operating conditions for the cylinder concerned.

Simultaneously it is achieved that the control of the combustion process of the cylinders in the engine is performed without any consideration for cylinder or load balance of the cylinders of the engine as a whole.

This way of controlling the engine ensures that each cylinder is operating optimally whilst there is no need to be concerned about cylinder balance (load balance).

y DK 2019 70697 A1 In a possible implementation of the second aspect the at least one combustion process parameter comprises: - fuel quantity, - timing of start of fuel injection, and/or - timing of exhaust valve closing.

In a possible implementation of the second aspect the closed loop control is performed without any consideration to maintain cylinder balance.

In a possible implementation of the second aspect the closed loop controlling applies a correction based on proportional and integral terms.

In a possible implementation of the second aspect the common setpoints are: - a common torque signal representative of the torque to be delivered by the engine, and/or - a common peak pressure signal representative of the peak cylinder pressure to be realized in the cylinders, - and/or a common compression pressure signal representative of the compression pressure to be realized in the cylinders.

In a possible implementation of the second aspect the closed loop control uses a cylinder-specific measured cylinder pressure as a reference value.

In a possible implementation of the second aspect a cylinder-specific mean indicated cylinder pressure is derived from the cylinder-specific measured cylinder

. DK 2019 70697 A1 pressure, and/or wherein a cylinder-specific peak pressure is derived from the cylinder-specific measured cylinder pressure, and/or wherein a cylinder-specific compression pressure is derived from the cylinder-

specific measured pressure.

According to a third aspect there is provided a method of operating a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads, the engine comprising: a plurality of cylinders having:

- an exhaust valve,

- an exhaust valve actuation system for actuating the exhaust valve,

- a fuel delivery system for delivering a quantity of first fuel to the cylinder concerned,

- a pressure sensor for generating a cylinder-specific pressure signal representative of a pressure in the cylinder concerned,

an exhaust gas driven turbocharger for pressurizing scavenging air for the cylinders, a controller in receipt of, or configured to determine for the actual operating conditions of the engine: a common torque signal representative of the torque to be delivered by the engine, a common peak pressure signal representative of the peak cylinder pressure to be realized in the cylinders, a common compression pressure signal representative of the compression pressure to be realized in the cylinders, the controller being in receipt of the cylinder-specific pressure signals, the method comprising:

Cc DK 2019 70697 A1 deriving from the cylinder-specific pressure signal an actual cylinder-specific torque signal representative of the torque delivered by the specific cylinder concerned, and adjusting the common torque signal as a function of a deviation of the common torque signal from the actual cylinder- specific torque signal to obtain a cylinder-specific torque signal, and delivering a quantity of fuel to the specific cylinder concerned as a function of the cylinder- specific torque signal,

and/or b) deriving from the cylinder-specific pressure signal an actual cylinder-specific peak pressure signal representative of the peak pressure in the cylinder concerned, adjusting the common peak pressure signal as a function of a deviation of the common peak pressure signal from the actual cylinder-specific peak pressure signal to obtain a cylinder-specific peak pressure signal, and timing the start of the delivery of the quantity of fuel as a function of the cylinder-specific peak pressure signal,

and/or

C) deriving from the cylinder-specific pressure signal an actual cylinder-specific compression pressure signal representative of the compression pressure in the cylinder concerned, adjusting the common compression pressure signal as a function of a deviation of the common compression pressure signal from the actual cylinder-specific compression pressure signal to obtain a cylinder-specific compression pressure signal, and

- DK 2019 70697 A1 timing the closing the exhaust valve as a function of the cylinder-specific compression pressure signal.

According to a fourth aspect there is provided a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads, the engine comprising: a plurality of cylinders having: - an exhaust valve, - an exhaust valve actuation system for actuating the exhaust valve, - a fuel delivery system for delivering a quantity of first fuel to the cylinder concerned, - a pressure sensor for generating a cylinder-specific pressure signal representative of a pressure in the cylinder concerned, an exhaust gas driven turbocharger for pressurizing scavenging air for the cylinders, a controller configured for closed loop controlling one or more combustion process parameters of the cylinders cylinder-specifically as a function of - the cylinder-specific pressure signal, and o common setpoints for all cylinders, or o cylinder-specific setpoints that are cylinder- specific offsets of the common setpoints. According to a fifth aspect there is provided a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads, the engine comprising: - a plurality of cylinders having: an exhaust valve, an exhaust valve actuation system for actuating the exhaust valve,

DK 2019 70697 A1 a fuel delivery system (30) for delivering a quantity of first fuel to the cylinder concerned, - an exhaust gas driven turbocharger for pressurizing scavenging air for the cylinders, —- a controller configured for cylinder-specifically controlling at least one of combustion process parameter (s), fuel quantity, timing of start of fuel injection, and timing of exhaust valve closing, the controller (55) being configured to: control the combustion process parameter (s) of the cylinders (1) individually as a function of operating conditions of the engine by cyclically cylinder-specifically adjusting a common Or a cylinder-specific setpoint for the combustion process parameter (s), to calculate an average for the cylinders of the cylinder-specific adjustments of the combustion process parameter (s), to limit the cylinder-specific adjustment in a cycle of the combustion process parameter (s) to a maximum predetermined deviation plus or minus from the calculated average of the adjustment of combustion process parameter concerned.

By providing a limiter function, that ensures that a particular cylinder-specific adjustment does not go out of bounds, it is ensured that sufficient flexibility can be provided for accommodating large adjustments that occur under normal circumstances whilst exorbitantly large adjustments that are caused by errors are suppressed and thereby ensure that damage or interrupted operation is avoided.

i. DK 2019 70697 A1 According to a possible implementation of the fifth aspect the controller is configured to define a window as a maximum predetermined deviation plus or minus from the calculated average of the adjustment of combustion process parameter concerned, and to limit the cylinder- specific adjustment in a cycle of the combustion process parameter (s) to an adjustment within the window.

According to a possible implementation of the fifth aspect the window is a range having a first extent in positive direction and a second extent in negative direction from the calculated average of the adjustment of the combustion process parameter concerned.

According to a possible implementation of the fifth aspect the window is combustion process parameter specific.

According to a possible implementation of the fifth aspect the positive extent has a first predetermined magnitude and wherein the negative extent has a second predetermined magnitude, the first predetermined magnitude not necessary being identical to the second predetermined magnitude.

According to a possible implementation of the fifth aspect the controller is configured to calculate an average of the c¢ylinder-specific adjustments of the cylinders for the combustion process parameter (s) for a cycle or for a plurality of «cycles of the cyclic adjustment of the combustion process parameter concerned.

>0 DK 2019 70697 A1 According to a possible implementation of the fifth aspect the adjustment of the combustion process parameter (s) is an adjustment for a single cycle.

According to a possible implementation of the fifth aspect the at least one combustion process parameter comprises: - fuel quantity, - timing of start of fuel injection, and/or - timing of exhaust valve closing.

According to a possible implementation of the fifth aspect the cylinder-specific setpoint for the combustion process parameter (s) is an offset of a common set point for the combustion process parameter (s).

According to a possible implementation of the fifth aspect the operating conditions of the engine are one or more of: engine speed, engine load, cylinder peak pressure, similar combustion pressure, cylinder mean indicated pressure, scavenging pressure fuel type, immediate humility and ambient temperature.

According to a sixth aspect there is provided a method of operating a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads, the engine comprising: - a plurality of cylinders having: an exhaust valve, an exhaust valve actuation system for actuating the exhaust valve, a fuel delivery system for delivering a quantity of first fuel to the cylinder concerned,

DK 2019 70697 A1 - an exhaust gas driven turbocharger for pressurizing scavenging air for the cylinders, the method comprising: cylinder-specifically controlling at least one of combustion process parameter (s), fuel quantity, timing of start of fuel injection, and timing of exhaust valve closing, controlling the combustion process parameter(s) of the cylinders (1) individually as a function of operating conditions of the engine by cyclically cylinder-specifically adjusting a common or cylinder-specific setpoint for the combustion process parameter (s), calculating an average of the cylinder-specific adjustments for the combustion process parameter (s), determining a window around the calculated average of the combustion process parameter (s) adjustments, and limiting the cylinder-specific adjustment in a cycle of the combustion process parameter (s) to a maximum predetermined deviation plus or minus from the calculated average of the adjustment of the combustion process parameter concerned.

Further objects, features, advantages and properties of the fuel valve and engine according to the present disclosure will become apparent from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS In the following detailed portion of the present description, the invention will be explained in more

> DK 2019 70697 A1 detail with reference to the exemplary embodiments shown in the drawings, in which: Fig. 1 is a front view of a large two-stroke diesel engine according to an example embodiment, Fig. 2 is a side view of the large two-stroke engine of Fig. 1, Fig. 3 is a diagrammatic representation the large two- stroke engine according to Fig. 1, and Fig. 4 is a schematic diagram of an embodiment of a controller for the engine of Fig. 1, and Fig. 5 is a schematic diagram of another embodiment of a controller for the engine of Fig. 1, and Fig. 6 is schematic diagram of yet another embodiment of a controller for the engine of Fig. 1.

DETAILED DESCRIPTION In the following detailed description, the compression- igniting internal combustion engine will be described with reference to a large two-stroke low-speed turbocharged internal combustion (Diesel) engine in the example embodiments. Figs. 1, 2 and 3 show a large low- speed turbocharged two-stroke diesel engine with a crankshaft 8 and crossheads 9. Fig. 3 shows a diagrammatic representation of a large low-speed turbocharged two-stroke diesel engine with its intake and exhaust systems. In this example embodiment the engine has six cylinders 1 in line. Large low-speed turbocharged two-stroke diesel engines have typically between four and fourteen cylinders in line, carried by an engine frame

11. The engine may e.g. be used as the main engine in an ocean going vessel or as a stationary engine for operating a generator in a power station. The total

> DK 2019 70697 A1 output of the engine may, for example, range from 1,000 to 110,000 kW. The engine is in this example embodiment a Diesel (compression-igniting) engine or an Otto engine of the two-stroke uniflow type with scavenge ports 18 at the lower region of the cylinders 1 and a central exhaust valve 4 at the top of the cylinders 1. The scavenge air is passed from the scavenge air receiver 2 to the scavenge ports 18 of the individual cylinders 1. A piston 10 in the cylinder 1 compresses the scavenge air, fuel is injected from fuel valves 50,51 in the cylinder cover 22, combustion follows, and exhaust gas is generated. When an exhaust valve 4 is opened, the exhaust gas flows through an exhaust duct associated with the cylinder 1 into the exhaust gas receiver 3 and onwards through a first exhaust conduit 19 to a turbine 6 of the turbocharger 5, from which the exhaust gas flows away through a second exhaust conduit via an economizer 20 to an outlet 21 and into the atmosphere. Through a shaft, the turbine 6 drives a compressor 7 supplied with fresh air via an air inlet 12. The compressor 7 delivers pressurized scavenge alr to a scavenge air conduit 13 leading to the scavenge alr receiver 2.

The scavenge air in conduit 13 passes an intercooler 14 for cooling the scavenge air. In an example embodiment the scavenge air leaves the compressor at approximately 200 'C and is cooled to a temperature between 36 and 80 "C by the intercooler. The cooled scavenge air passes via an auxiliary blower 16 driven by an electric motor 17 that pressurizes the scavenge air flow when the compressor 7 of the

> DK 2019 70697 A1 turbocharger 5 does not deliver sufficient pressure for the scavenge air receiver 2, i.e. in low or partial load conditions of the engine. At higher engine loads the turbocharger compressor 7 delivers sufficient compressed scavenge air and then the auxiliary blower 16 is bypassed via a non-return valve 15.

The piston is coupled by a piston rod to a crosshead 9. The crosshead 9 is connected to a crankshaft 8 via a connecting rod. The rotational speed and position of the crankshaft 8 is measured by a sensor 40. The measured engine speed signal of the sensor 40 is send to the controller 55, e.g. via a signal line.

13 Each cylinder 1 is provided with an exhaust valve 4, with two or more fuel valves 50 and a pressure sensor 42. The cylinder-specific pressure signal of the pressure sensor 42 is send to a controller 55.

The engine is in an embodiment a dual fuel engine and in this embodiment two or more fuel valves 50 are dedicated to a first fuel and two or more fuel valves 50 are dedicated to a second fuel. Alternatively, the two or more fuel valves are shared by the two fuels.

The fuel valves 50 are controlled by the controller 55, e.g. the controller 55 determines when the fuel valves open and how long the fuel valves are open, and in an embodiment, also determines the profile of the opening of the fuel valves 50. The fuel valves 50 are part of the fuel supply system 30. The signal for opening and closing the fuel valves 50 can be a fluidic signal or a hydraulic signal. In an embodiment where the signal for opening and closing the fuel valve is a fluidic signal, such as a

J DK 2019 70697 A1 hydraulic signal, the controller 55 can be to sends an electronic signal to electronically controlled valve or pump, and the hydraulic signal is sent from this electronically controlled valve or pump to the fuel valves 55. In an embodiment the fuel supply system 30 is configured to be able to supply at least two different fuels.

In an embodiment one of the two fuels is fuel oil, such as e.g. fuel oil or heavy fuel oil or methanol.

In an embodiment one of the two fuels is a gaseous fuel such as petroleum gas or natural gas.

In an embodiment the gaseous fuel is admitted or injected into the cylinders in gaseous state.

In another embodiment the gaseous fuel is admitted or injected into the cylinders in liquid state.

In an embodiment, the engine is a fuel-led engine.

In a fuel-led or gas-led combustion process, the fuel quantity to be metered is determined as a function of the duty point of the internal combustion engine and a specifiable target value for the power and/or the speed of the internal combustion engine.

Fuel-led combustion processes are of particular application during variable speed operation of an internal combustion engine, in an internal combustion engine in isolated operation, during engine start-up or when the internal combustion engine is idling.

The engine controls deployed comprise a power controller and/or a speed controller.

An engine operating exclusively according to the Diesel process is a fuel-led engine, regardless what the fuel is a liquid fuel or a gaseous fuel.

Typically, the fuel is injected shortly after Top Dead Center (TDC), and ignites immediately upon injection.

Thus, the amount of fuel to be injected is the leading control parameter of a fuel-led engine.

Je DK 2019 70697 A1 In an embodiment, the engine is an air-led engine. In an air-led combustion process, a fuel quantity to be metered is determined, for example, as a function of the duty point of the internal combustion engine and a specifiable target value for the fuel-air ratio, in order to avoid knock problems is premature combustion) or a specific scavenging air pressure, especially a specific compression pressure. The engine controls deployed thereby usually comprise a compression pressure controller. An engine exclusively operating according to the Otto process is an air-led engine, regardless of the type of fuel. Thus, the compression air pressure is the leading control parameter of an air-led engine.

In embodiment the engine is a combination of an air inlet and a fuel led engine. An example of such an engine is engine in which a first amount of fuel is admitted to the combustion chamber before during the compression stroke, and an additional second amount of fuel is injected near Top Dead Center (TDC). The injection of the second amount of fuel starts the ignition of both the second amount of fuel and the first amount of fuel in the combustion chamber. In large two-stroke engines the injection near TDC is typically shortly after TDC. In this engine both the amount of fuel to be injected and the compression pressure are the leading control parameters, and the importance of either parameter may depend on engine load and speed.

In an embodiment, the internal combustion engine a dual fuel engine and is fuel-led when operating on a first fuel and air-led when operating on a second fuel.

>; DK 2019 70697 A1 Fach exhaust valve 4 is provided with an exhaust valve actuator 46. In an embodiment the exhaust valve actuator 46 is a hydraulic actuator that is commanded by an electronic signal from controller 55.

One more combustion process parameters of the combustion processes in the «cylinders 1 are controlled by a controller 55. The combustion process parameters are for example at least one of fuel quantity, timing of start of fuel admission/injection, and timing of the exhaust valve closing. The combustion process parameter fuel quantity is «correlated to the contribution of the cylinder 1 concerned to the torque delivered by the engine. The combustion process parameter timing of the start of the fuel injection correlates to the peak pressure in the cylinder concerned (this applies in particular to engines operating according to the diesel principle not as much to engines that operate according to the Otto principal, in which the fuel is admitted rather than injected). The combustion process parameter timing of the exhaust valve closing correlates to the combustion pressure of the cylinder 1 concerned.

Fig. 4 shows a first embodiment of the controller 55. The controller 55. In an embodiment the controller 55 comprises an engine controller and a plurality of cylinder controllers.

The controller 55 receives a speed set, i.e. a desired engine speed, for example from the bridge of a ship. The controller 55 is in receipt of the engine speed signal from the sensor 40, and the controller 55 compares the desired engine speed with the measured engine speed to

Je DK 2019 70697 A1 obtain speed deviation signal. The controller 55 comprises a governor that is fed with the speed deviation signal. The governor is configured to determine a fuel index as a function of the deviation of the desired engine speed from the measured engine speed, 1.e. the governor is configured to determine a fuel index as a function of the speed deviation signal. The fuel index signal is a signal that indicates the amount of fuel to be admitted/injected to achieve the desired engine speed.

The amount of fuel to be injected is directly correlated to the amount of torque to be delivered by the engine. The controller 55 comprises an index to common torque signal module that is configured to covert the fuel index to a common torque signal by applying the fuel index to a first predetermined map. The common indicated torque/Index can be considered to be even proportional to the common mean indicated pressure.

The expression "common” in this document means: applying to all cylinders. The first predetermined map is established from tests, for example test performed on a test that at the factory where the engine is developed and/or built. The first predetermined map comprises in an embodiment a table or algorithm that correlates fuel index to common indicated torque.

A cylinder controller is associated with each of the cylinders 1. The common torque signal is sent to each of the cylinder controllers.

>o DK 2019 70697 A1 The controller 55 comprises a power calculation module (Load calculation) configured for calculating an engine load signal indicative of the engine load. In an embodiment the engine load signal is representative of the actual engine load relative to a maximum engine load, such as the maximum continuous rating. The power calculation module is in receipt of the index signal and the measured engine speed. In an embodiment the load calculation module multiplies the engine speed with the fuel index and multiplies this result by a predetermined factor that has been established from tests or experience values in order to arrive at the (relative engine load, a percentage of the maximum continuous rating).

The controller 55 comprises an engine running mode module that 1s configured to determine a common peak pressure signal by applying the engine load signal to a second predetermined map and configured to determine a common compression pressure by applying the engine load signal to a third predetermined map.

The second and third predetermined maps are established from tests, for example tests performed on a test bed at the factory where the engine is developed and/or built.

The second predetermined map comprises in an embodiment a table or algorithm that correlates peak pressure to engine load and the third predetermined map comprises in an embodiment the table or algorithm that correlates compression pressure to engine load. The second and third maps may Take into account a number of other parameters, such as ambient pressure, ambient temperature, and engine speed and may include offsets for e.g. friction losses.

DK 2019 70697 A1 The common peak pressure signal and the common compression pressure signal are sent to all cylinder controllers.

Fach cylinder controller receives a specific measured cylinder pressure from the pressure sensor 42 of the cylinder 1 to which the cylinder controller concerned is dedicated.

The cylinder controller is configured to calculate an actual cylinder-specific maximum pressure, an actual cylinder-specific compression pressure and an actual cylinder-specific mean indicated pressure from the cylinder-specific pressure signal received from the pressure sensor 42 of the cylinder 1 concerned. The cylinder-specific mean indicated pressure is thereafter expressed as an actual cylinder-specific torque. Preferably, the cylinder-specific actual pressure values are determined from the arithmetic mean, particular preferably the median of a plurality of consecutive pressure measurements, for example over a plurality of engine cycles, such as for example between 5 and 50 engine cycles, preferably approximately 10 engine cycles.

In order to obtain a better signal quality and thus a higher control performance, the cylinder-specific pressure signal of a cylinder is the temporally filtered measured cylinder-specific first pressure signal acquired over 5 to 50 engine cycles, preferably 7 to 15 combustion cycles.

The actual cylinder-specific pressures are thus the result of a statistical evaluation of the pressure

51 DK 2019 70697 A1 measurements by the pressure sensor 42 of the cylinder 1 concerned.

The cylinder controller is configured and to adjust the common torque signal as a function of a deviation of the common torque signal from the actual cylinder-specific torque signal to obtain a cylinder-specific torque signal.

Thus, the cylinder controller continuously (or intermittently) calculates an error value as the difference between the cylinder-specific torque and the actual cylinder-specific torque and applies a correction based on proportional and integral terms (PI regulator), to arrive at the cylinder-specific torque signal and to form a closed loop control for the specific cylinder 1 concerned.

In an embodiment, controller 55 is in receipt of the adjustment of the common torque, the adjustment of the common peak pressure and/or the adjustment of the common compression pressure.

In this embodiment the controller 55 is configured to determine a mean for the adjustment of the common torque of all the cylinders, a mean or average of the adjustments for the common peak pressure of all of the cylinders and/or a mean or average of the adjustment for the compression pressure of the cylinders.

In this embodiment the controller 55 is configured to allow the individual cylinder controllers to set a limit for the maximum adjustment of the cylinder-specific torque, the cylinder-specific peak pressure and/or the cylinder-specific compression pressure within a window that is defined by the respective mean plus or minus an adjustment of a predetermined magnitude.

For example, the adjustment window is plus or minus 5 bar from the

> DK 2019 70697 A1 calculated average. When in this example the average of the adjustment of the cylinder-specific peak pressures for all of the cylinders is plus 2 bar, the individual cylinders controllers will be allowed to adjust cylinder- specific peak pressure adjustment between minus 3 and plus 7 bar. A limiter limits the maximum correction to the common torque signal. If the correction of the common torque signal points in the same direction for all of the cylinders 1, the limiter allows a maximum correction up to a first threshold. If the correction of the common torque signal does not point in the same direction for all the «cylinders 1 the limiter allows a maximum correction up to a second threshold, the second threshold being lower than the first threshold. Thus, it is avoided that an erroneous signal destabilizes the system, and larger corrections are allowed if all cylinders 1 have the same development.

Thus, the controller 55 calculates an average for all of the cylinders of the cylinder-specific adjustments of the torque signal and limits the cylinder-specific adjustment in a cycle of the torque signal to a maximum predetermined deviation plus or minus from the calculated average of the adjustment the torque signal. The controller 55 is configured to define a window as a maximum predetermined deviation plus or minus from the calculated average of the adjustment of the torque signal and configured to limit the cylinder-specific adjustment in a cycle of the torque signal to an adjustment within the window. The window is a range with a first extent in positive direction and a second extent in negative

> DK 2019 70697 A1 direction from the calculated average of the adjustment of the torque signal. Window specific for the torque signal, and for the other combustion process parameters (the pressure and combustion pressure). The positive extent has a first predetermined magnitude and wherein the negative extent has a second predetermined magnitude. These magnitudes can for example be established at the factory from test runs. The window should be large enough to accommodate the largest adjustments that will normally occur, but small enough to exclude adjustments that are likely to be caused by an error, such as for example an erroneous sensor signal. The controller 55 is configured to calculate an average 13 of the cylinder-specific adjustments of the cylinders for the torque signal for a cycle or for a plurality of cycles of the cyclic adjustment of the torque signal. In an embodiment, the adjustment of the combustion process parameter (s) is an adjustment for a single cycle.

An injection profile module translates the cylinder- specific torque signal into a cylinder-specific fuel valve profile signal. The injection profile module correlates the cylinder-specific torque signal to an injection profile by applying the specific torque signal to a fourth predetermined map. Fourth map may comprise algorithms and/or lookup tables that have been established from tests. The cylinder-specific fuel valve profile signal is sent to the fuel valves 50 of the cylinder concerned and instructs the fuel valves 50 according to which profile the fuel valves 50 should open and close, i.e. fuel valve opening duration and profile shape. The fuel valves 50 deliver the cylinder-specific quantity of fuel to the specific cylinder 1 concerned in

51 DK 2019 70697 A1 response to the fuel valve profile signal of the cylinder controller associated with the cylinder 1 concerned.

The cylinder controller is configured and to adjust the common peak pressure signal as a function of a deviation of the common peak pressure signal from the actual cylinder-specific peak pressure signal to obtain a cylinder-specific peak pressure signal. Thus, the cylinder controller continuously (or intermittently) calculates an error value as the difference between the cylinder-specific torque and the actual cylinder-specific the pressure and applies a correction based on proportional and integral terms (PI regulator), to arrive at the cylinder-specific peak pressure signal and to form a closed loop control for the specific cylinder 1 concerned. In the same way as described above for the torque signal, limiter for the peak pressure signal limits the maximum correction to the common peak pressure signal. If the correction of the common peak pression signal points in the same direction for all of the cylinders 1, the limiter allows a maximum correction up to a first threshold. If the correction of the common peak pressure signal does not point in the same direction for all the cylinders 1 the limiter allows a maximum correction up to a second threshold, the second threshold being lower than the first threshold. Thus, it is avoided that an erroneous signal destabilizes the system, and larger corrections are allowed if all cylinders 1 have the same development. A peak pressure module translates the cylinder-specific peak pressure signal into a cylinder-specific fuel

>5 DK 2019 70697 A1 injection timing signal. Hereto, the peak pressure module applies the cylinder-specific peak pressure signal to a fifth predetermined map. The fifth predetermined map may comprise algorithms and/or lookup tables that correlate the pressure to the start of the fuel admission/injection. The algorithms and/or lookup tables of the fifth predetermined map may be established by tests.

The cylinder-specific fuel injection timing signal is sent to the fuel valves 50 of the cylinder 1 concerned and instructs the fuel valves 50 when the fuel valve should start to open, i.e. the time (angle) for starting fuel admission/injection. The fuel valves 50 of the 13 cylinder 1 concerned begin the admission/injection of the cylinder-specific quantity of fuel into the specific cylinder 1 concerned in response to the injection timing signal of the cylinder controller associated with the cylinder 1 concerned.

The cylinder controller is configured and to adjust the common compression pressure signal as a function of a deviation of the common compression pressure signal from the actual cylinder-specific compression pressure signal to obtain a cylinder-specific compression pressure signal. Thus, the cylinder controller continuously (or intermittently) calculates an error value as the difference between the cylinder-specific compression signal and the actual cylinder-specific compression pressure and applies a correction based on proportional and integral terms (PI regulator), to arrive at the cylinder-specific compression pressure signal and to form a closed loop control for the specific cylinder 1 concerned.

>6 DK 2019 70697 A1 In the same way as described above for the torque signal and for the peak pressure signal, a limiter for the compression pressure signal limits the maximum correction to the common compression pressure signal.

If the correction of the common compression pression signal points in the same direction for all of the cylinders 1, the limiter allows a maximum correction up to a first threshold.

If the correction of the common compression pressure signal does not point in the same direction for all the cylinders 1 the limiter allows a maximum correction up to a second threshold, the second threshold being lower than the first threshold.

Thus, it is avoided that an erroneous signal destabilizes the system, and larger corrections are allowed if all cylinders 1 have the same development.

A compression pressure module translates the cylinder- specific compression pressure signal into a cylinder- specific exhaust valve close timing signal.

Hereto, the compression pressure module applies the cylinder-specific compression pressure signal to a sixth predetermined map.

The sixth predetermined map may comprise algorithms and/or lookup tables that correlate the compression pressure to the closing timing of the exhaust valve 4. The algorithms and/or lookup tables of the sixth predetermined map may be established by tests.

The cylinder-specific exhaust valve close timing signal is sent to the fuel valves 50 of the cylinder 1 concerned and instructs the exhaust valve actuator 46 when the exhaust valve 4 should close, i.e. the time (angle) for closing the exhaust valve 4. The exhaust valve actuator 46 of the cylinder 1 concerned exhaust valve 4 of the

> DK 2019 70697 A1 specific cylinder 1 concerned in response to the exhaust valve close timing signal of the cylinder controller associated with the cylinder 1 concerned.

In an embodiment the cylinder-specific torque signal (mean indicated pressure) adjustment, the cylinder- specific peak pressure adjustment and the cylinder- specific combustion pression adjustment are send back to the controller 55 and an average mean indicated pressure adjustment, an average peak pressure adjustment and an average combustion pressure adjustment are calculated. The adjustment is carried out cyclically, for example for every single, two, five or ten engine revolutions. The averages for the combustion process parameters of all the cylinders are also calculated cyclically, preferably with the same cycle frequency as the adjustment cycle. The controller 55 sets a limit for the cylinder-specific adjustment of the respective combustion process parameter relative to the calculated average of the combustion process parameter concerned. The limit may be in the form of a maximum predetermined deviation plus or minus from the calculated average. The predetermined plus deviation may be different from the predetermined minus deviation. Thus, a window is formed around the calculated average of the process parameter concerned. The predetermined plus and minus deviations are process parameter specific. Integrator windup will be variable so that larger adjustments are allowed when the average adjustment of torque, peak pressure and combustion pressure is large.

The cylinder controllers are configured to control the cylinders 1 of the engine individually without any consideration to maintain cylinder balance, i.e. without cylinder balancing. Thus, each cylinder 1 operates in

50 DK 2019 70697 A1 accordance with design specifications by providing a cylinder-specific feedback loop control for the cylinder- specific mean indicated pressure (torque) and/or by providing a cylinder-specific feedback loop control for the cylinder-specific peak pressure and/or by providing a cylinder-specific feedback loop control for the cylinder- specific compression pressure. Since all of the cylinders 1 will be operating in accordance with design specification there is no need for cylinder balancing. This is of particular advantage for a dual fuel engine after a change of fuel from fuel to another fuel. In conventional engines, such a fuel change requires manual recalibration for the engine to run optimal after the fuel change. With the controller according to this document, there is no need for manual recalibration after the fuel change. Especially peak pressure and torque are very important during Fuel Oil to S secondary Fuel (e.g. gas) transitions, and this will be automatically insured/adjusted with the present controller.

However, under circumstances it can be necessary to operate one or more cylinders different from the design specifications. For example, a cylinder 1 when a cylinder 1 is in a state where it is determined that there is a significant risk of cylinder liner scuffing (adhesion), which is sometimes caused by insufficient cylinder lubrication. It can be necessary to reduce the load on such a cylinder that gives signs that scuffing is taking place or will soon take place if the load is not reduced. Thus, in the embodiment of the controller shown in Fig. 5 embodiment each cylinder control and comprises a cylinder-specific cylinder offset module for each cylinder 1. In this embodiment, structures and features that are the same or similar to corresponding structures

50 DK 2019 70697 A1 and features previously described or shown herein are denoted by the same reference numeral as previously used for simplicity. This embodiment of the controller 55 is essentially identical to the embodiment of Fig. 4, except for the addition of the cylinder-specific offset modules. The cylinder-specific offset modules are configured for offsetting the common torque signal, the common peak pressure signal, and/or the common compression pressure signal for a specific cylinder 1 concerned. The offset can be induced human operator or the automatically induced, for example based on signals from a sensor that cause the cylinder controller or the controller introducing offset setting for a specific cylinder 1. For example, detection of knocking in one specific cylinder can be detected by sensors. In response to such a knocking sensor, the compression pressure of that specific cylinder is reduced by the controller 55 to reduce the temperature in the combustion chamber thereby reduce the risk of knocking. Thus, a cylinder-specific offset will be introduced for the cylinder concerned. Further, in an embodiment the controller 55 is configured to increase the air to fuel ratio by reducing the amount of fuel, through an offset of the cylinder-specific offset for the amount of fuel to be injected.

Thus, the cylinder offset module outputs a cylinder- specific torque set point, a cylinder-specific peak pressure set point and a cylinder-specific compression pressure set point. The cylinder-specific setpoints are adjusted, in the same way as shown for the embodiment of Fig. 4 above as a function with the difference between the respective actual cylinder-specific torque, cylinder- specific peak pressure and cylinder-specific compression pressure, to arrive at a cylinder-specific torque,

20 DK 2019 70697 A1 cylinder-specific peak pressure and cylinder-specific compression pressure, respectively.

Fig. 6 shows another embodiment of the controller 55. 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 numeral as previously used for simplicity. This embodiment of the controller 55 is essentially identical to the embodiment of Fig. 5, except for the addition of a fuel index to profile duration module. The fuel index the profile duration module is configured to convert the fuel index signal to a common profile duration signal.

Fach cylinder controller is in receipt of the common profile duration signal. The cylinder controllers adjust the common fuel delivery duration signal as a function of a deviation of the common fuel delivery duration signal from the cylinder-specific torque signal to obtain a cylinder-specific fuel profile duration signal. The addition of the common profile duration signal renders the engine more robust to fluctuations of the fuel quality. In particular gaseous fuels have a tendency to vary in properties, for example the gas LCV (lower caloric values) can vary up to 30-50%. In an embodiment the common torque signal corresponds to the mean indicated cylinder pressure for all of the cylinders and wherein the cylinder-specific torque signal corresponds to the mean indicated cylinder pressure for the specific cylinder concerned.

21 DK 2019 70697 A1 The various aspects and implementations have been described in conjunction with various embodiments herein.

However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.

A single processor, controller or other unit may fulfill the functions of several items recited in the claims.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

The reference signs used in the claims shall not be construed as limiting the scope.

Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this disclosure.

Claims

i DK 2019 70697 A1 CLAIMS:

1. A large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads (9), said engine comprising: a plurality of cylinders (1) having: - an exhaust valve (4), - an exhaust valve actuation system (46) for actuating said exhaust valve (4), - a fuel delivery system (30) for delivering a quantity of first fuel to the cylinder (1) concerned, - a pressure sensor (42) for generating a cylinder- specific pressure signal representative of a pressure in the cylinder (1) concerned, an exhaust gas driven turbocharger (5) for pressurizing scavenging air for the cylinders (1), a controller (55) in receipt of, or configured to determine for the actual operating conditions of the engine: a common torque signal representative of the torque to be delivered by the engine, a common peak pressure signal representative of the peak cylinder pressure to be realized in said cylinders (1), a common compression pressure signal representative of the compression pressure to be realized in said cylinders (1), sald controller (55) being in receipt of said cylinder- specific pressure signals,

12 DK 2019 70697 A1 wherein: a) sald controller (55) is configured to derive from sald cylinder-specific pressure signal an actual cylinder-specific torque signal representative of the torque delivered by the specific cylinder (1) concerned, and to adjust said common torque signal as a function of a deviation of said common torque signal from said actual cylinder-specific torque signal to obtain a cylinder-specific torque signal, and to deliver a quantity of fuel to the specific cylinder (1) concerned as a function of said cylinder-specific torque signal,

and/or b) sald controller (55) is configured to derive from sald cylinder-specific pressure signal an actual cylinder-specific peak pressure signal representative of the peak pressure in the cylinder concerned (1), to adjust said common peak pressure signal as a function of a deviation of said common peak pressure signal from said actual cylinder- specific peak pressure signal to obtain a cylinder- specific peak pressure signal, and to time the start of the delivery of said quantity of fuel to the specific cylinder (1) concerned as a function of said cylinder-specific peak pressure signal, and/or

21 DK 2019 70697 A1 C) sald controller (55) is configured to derive from said cylinder-specific pressure signal an actual cylinder-specific compression pressure signal representative of the compression pressure in the cylinder (1) concerned, to adjust said common compression pressure signal as a function of a deviation of said common compression pressure signal from said actual cylinder-specific compression pressure signal to obtain a cylinder-specific compression pressure signal, and to time the closing the exhaust valve as a function of said cylinder-specific compression pressure signal.

2. The engine according to claim 1, wherein said engine is a fuel-led and comprises at least element a).

3. The engine according to claim 1, wherein said engine is an air-led and comprises at least element c).

4. The engine according to claim 1, wherein said engine is a partially fuel-led and partially air-led and comprises at least element a) and element c).

5. The engine according to any one of claims 1 to 4, wherein said engine is a dual fuel engine and wherein sald fuel delivery system (30) is configured to handle at least two different fuels, and said cylinders (1) each being provided with at least one fuel wvalve (50) for delivering a first fuel and at least one fuel valve (50) for delivering a second fuel.

Ls DK 2019 70697 A1

6. The engine according to claim 5, wherein said engine is fuel-led when operating on said first fuel and air-led when operating on said second fuel.

7. The engine according to any one of claims 1 to 6, wherein said controller (50) is in receipt of a desired engine speed and in receipt of a measured engine speed, and wherein said controller (55) comprises a governor configured to determine a fuel index signal as a function of the deviation of the desired engine speed from the measured engine speed.

8. The engine according to claim 7, said controller (55) is configured to covert said fuel index signal to said common torque signal by applying said fuel index signal to a first predetermined map.

9. The engine according to claim 7 or 8, wherein said controller (55) comprises a power calculation module configured for calculating an engine load signal indicative of the engine load, said power calculation module preferably being in receipt of said fuel index signal and the measured engine speed.

10. The engine according to claim 9, wherein said controller (55) is configured: - to determine said common peak pressure signal by applying said engine load signal to a second predetermined map, and/or to determine said common compression pressure by applying said engine load signal to a third predetermined map.

26 DK 2019 70697 A1

11. The engine according to any one of claims 1 to 10, wherein said controller (55) comprises a fuel index signal to profile duration module, the profile duration module being configured to convert said fuel index signal to a common fuel delivery duration signal.

12. The engine according to claim 11, wherein said controller (55) is configured to adjust said common fuel delivery duration signal as a function of a deviation of said common fuel delivery duration signal from said cylinder-specific torque signal to obtain a cylinder- specific fuel delivery duration signal.

13. An engine according to any one of claims 1 to 12, wherein and said controller (55) is configured to determine a cylinder-specific injection profile as a function of said cylinder-specific torque signal or as a function of said cylinder-specific fuel delivery duration signal, and wherein said fuel delivery system (30) delivers said quantity of fuel to the specific cylinder (1) concerned by opening one or more fuel valves (50) in accordance with said cylinder-specific injection profile.

14. An engine according to any one of claims 1 to 13, wherein said fuel delivery system (30) starts the delivery of said quantity of fuel to the specific cylinder (1) concerned by opening of one or more fuel valves (50) in accordance with the start of the timing of the delivery of said quantity of fuel determined by the controller (55).

15. An engine according to any one of claims 1 to 14, wherein said controller (55) is configured:

i DK 2019 70697 A1 - to limit the magnitude of the adjustment of said common torque signal to a first threshold when the adjustment for the other cylinders (1) is in the same direction and wherein said controller (55) is configured to limit the magnitude of the adjustment of said common torque signal to a second threshold when the adjustment for the other cylinders (1) is in an opposite direction, said second threshold being lower than said first threshold if said engine has element a), and/or to limit the magnitude of the adjustment of said common peak pressure signal to a first threshold when the adjustment for the other cylinders (1) is in the same direction and wherein said controller (55) is configured to limit the magnitude of the adjustment of said common peak pressure signal to a second threshold when the adjustment for the other cylinders (1) is in an opposite direction if said engine has element b), and/or to limit the magnitude of the adjustment of said common compression pressure signal to a first threshold when the adjustment for the other cylinders (1) is in the same direction and wherein sald controller (55) is configured to limit the magnitude of the adjustment of said common compression pressure signal to a second threshold when the adjustment for the other cylinders (1) is in an opposite direction if said engine has element Cc).

16. An engine according to any one of claims 8 to 15, wherein said first, second and/or third predetermined map ie DK 2019 70697 A1 are preferably predetermined at the engine factory from tests of the engine concerned or of an identical or comparable engine, said first, second and/or third predetermined map are preferably comprise an algorithm and/or table.

17. An engine according to any one of claims 1 to 16, wherein said common torque signal corresponds to the mean indicated cylinder pressure for all of the cylinders and wherein said cylinder-specific torque signal corresponds to the mean indicated cylinder pressure for the specific cylinder concerned.

18. An engine according to any one of claims 1 to 17, wherein said controller (55) comprises a cylinder- specific cylinder offset module for each cylinder, said cylinder-specific offset module being configured for offsetting said common torque signal, said common peak pressure signal, and/or said common compression pressure signal for a specific cylinder concerned.

19. An engine according to any one of claims 1 to 18 wherein said cylinder-specific offset module is controlled manually or automatically.

20. An engine according to any one of claims 1 to 19 wherein said controller (55) is configured to control the cylinders (1) of the engine individually without consideration for cylinder balance.

21. An engine according to any one of claims 1 to 20 wherein: said controller (55) is configured to continuously calculate an error value as the difference between

29 DK 2019 70697 A1 sald cylinder-specific torque and said actual cylinder-specific torque and to apply a correction based on proportional and integral terms, if said engine has element a), said controller (55) is configured to continuously calculate an error value as the difference between said cylinder-specific peak pressure and said actual cylinder-specific peak pressure and to apply a correction based on proportional and integral terms, if said engine has element b), said controller (55) is configured to continuously calculate an error value as the difference between said cylinder-specific compression pressure and said actual cylinder-specific compression pressure and to apply a correction based on proportional and integral terms, if said engine has element c).

22. An engine according to any one of claims 1 to 21, wherein said fuel delivery system (30) is configured for delivering a quantity of first fuel and/or quantity of second fuel to the cylinder (1) concerned.

23. A method of operating a large low speed two-stroke uniflow scavenged turbocharged internal combustion engine with crossheads (9), said engine comprising: a plurality of cylinders (1) having: - an exhaust valve (4), - an exhaust valve actuation system (46) for actuating said exhaust valve (4), - a fuel delivery system (30) for delivering a quantity of first fuel to the cylinder (1) concerned,

- DK 2019 70697 A1 - a pressure sensor (42) for generating a cylinder- specific pressure signal representative of a pressure in the cylinder (1) concerned, an exhaust gas driven turbocharger (5) for pressurizing scavenging air for the cylinders (1), said method comprising: closed loop controlling at least one combustion process parameter of the cylinders (1) cylinder-specifically as a function of - said cylinder-specific pressure signal, and o common setpoints for all cylinders (1), or o cylinder-specific setpoints that are cylinder- specific offsets of said common setpoints.

24. The method according to claim 23, wherein at least one combustion process parameter comprises: - fuel quantity, - timing of start of fuel injection, and/or - timing of exhaust valve closing.

25. A method according to claim 23 or 24, wherein said closed loop control is performed without any consideration to maintain cylinder balance.

26. A method according to any one of claims 23 to 25, wherein said closed loop controlling applies a correction based on proportional and integral terms.

27. A method according to any one of claims 22 to 26, wherein said common setpoints are: - a common torque signal representative of the torque to be delivered by the engine, and/or of DK 2019 70697 A1 - a common peak pressure signal representative of the peak cylinder pressure to be realized in said cylinders, - and/or a common compression pressure signal representative of the compression pressure to be realized in said cylinders.

28. A method according to any one of claims 23 to 27, wherein said closed loop control uses a cylinder- specific measured cylinder pressure as a reference value.

29. A method according to claim 28, wherein a cylinder- specific mean indicated cylinder pressure is derived from said cylinder-specific measured cylinder pressure, and/or wherein a cylinder-specific peak pressure is derived from said cylinder-specific measured cylinder pressure, and/or wherein a cylinder-specific compression pressure is derived from said cylinder-specific measured pressure.