Internal combustion engine and method for operating internal combustion engine

Abstract

To provide an internal combustion engine and a method of operating the internal combustion engine which allow a precise setting of engine parameters.SOLUTION: The present invention relates to an internal combustion engine 10 comprising a system for exhaust gas recirculation, and to a method for operating the internal combustion engine. The internal combustion engine 10, namely a large vessel engine or a stationary engine, which is operable at least in a gas mode, comprises at least one cylinder 11 having an inner diameter 12 of at least 200 mm. The internal combustion engine 10 comprises a turbocharger 13, which comprises a turbine 14 and a compressor 15. The engine comprises a low-pressure exhaust gas recirculation path 16 with an EGR valve 17. The internal combustion engine 10 further comprises a first measuring unit 18 for providing a signal representative of an excess air ratio in the low-pressure exhaust gas recirculation path, preferably the first measuring unit has a lambda sensor arranged downstream of the EGR valve 17.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine having a system for recirculating exhaust gases, and to a method for operating an internal combustion engine.

[0002] The present invention preferably relates to an internal combustion engine, such as a large marine or ship engine or a stationary engine, in which the cylinder has an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke cross-head engine. [Background technology]

[0003] The engine may be a diesel engine or a gas engine, a dual-fuel engine or a multi-fuel engine. Such engines may be capable of combustion of gaseous fuels or liquid and / or gaseous fuels, as well as auto-ignition or forced ignition.

[0004] The term internal combustion engine therefore also generally refers to large engines capable of operating not only in diesel mode, characterized by the autoignition of fuel, but also in Otto mode, characterized by the active ignition of fuel, for example by spark ignition, or in a mixture of the two. Furthermore, the term internal combustion engine particularly includes dual-fuel engines and large engines in which the autoignition of one fuel is used for the active ignition of another fuel.

[0005] The engine has at least one cylinder containing a piston. The piston is connected to the crankshaft. During engine operation, the piston reciprocates between top dead center (TDC) and bottom dead center (BDC). The cylinder typically has at least one intake air passage opening, particularly an air inlet located in the cylinder liner, and at least one exhaust air passage opening, particularly an exhaust outlet located in the cylinder cover. Preferably, the air inlet is fluidly connected to a scavenging air receiver.

[0006] The internal combustion engine can be a two-stroke engine that is scavenged in the vertical direction.

[0007] The engine speed is preferably less than 800 RPM (four-stroke), and more preferably less than 200 RPM (two-stroke), which suggests the designation of a low-speed engine.

[0008] The fuel can be diesel or marine diesel oil or heavy fuel oil, or an emulsion, or a slurry, or methanol, or ethanol, and gases such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), etc.

[0009] Further possible fuels that may be added upon request are liquefied biogas (LBG), biofuels (e.g., algal fuel or seaweed oil), hydrogen, synthetic fuels from CO2 (e.g., those made by power-to-gas or power-to-liquid).

[0010] Large ships, especially cargo ships, are usually powered by internal combustion engines, especially diesel and / or gas engines, mostly two-stroke, cross-head engines. In the case of liquid fuels such as heavy fuel oil, marine diesel oil, diesel, or other liquids burned in the engine, and in the case of gaseous fuels such as LNG, LPG, or others, the exhaust from this combustion process needs to be purified to comply with current pollutant regulations such as IMO Tier III rules.

[0011] The internal combustion engine can operate in gas mode. A fluid fuel such as gas fuel can be provided by a gas inlet valve or a pressurized gas liquid can be provided as a liquid, which is used for torque generation. In gas mode, further, for induced ignition, injection of a small amount of liquid fuel, sometimes called pilot injection, can be carried out.

[0012] In addition to air and fluid fuel, an inert gas such as exhaust gas can be introduced into the cylinder. The engine can have a high-pressure or low-pressure exhaust gas recirculation path.

[0013] Modern four-stroke Otto-cycle engines use closed-loop lambda control to measure the oxygen content in the exhaust gas and control the amount of fuel injected into the engine in order to maintain lambda within desirable limits and to avoid rich combustion.

[0014] In two-stroke engines, in-cylinder lambda measurement can be difficult due to the cylinder scavenging process that allows air to enter the inlet port and mix with the exhaust gas during the opening of the exhaust valve. Therefore, the measurement of residual combustion oxygen in the exhaust gas is not reliable.

[0015] It is known from European Patent Application Publication No. 3722572A1 that the combustion pressure peak angle can be adjusted by adapting the pilot fuel injection timing, by adapting the EGR rate, by adapting the amount of fuel added, by adapting the scavenging air pressure, and / or by adapting the amount of inert additives. The EGR rate can have a strong influence on the combustion process.

[0016] The EGR system can result in a reduction in the temperature after compression and the inerting of the cylinder charge, which helps to suppress premature ignition of the charge and knocking of the engine.

[0017] It is known that an inert gas such as exhaust gas can be introduced into the cylinder to reduce or avoid abnormal combustion processes. It is known from European Patent Application Publication No. 3081890A1 that knocking and misfires can also be reduced or avoided by adjusting the EGR rate to prevent premature ignition.

[0018] Furthermore, the application of exhaust gas recirculation can reduce the exhaust gas emissions of CH4, THC, NO x , CO.

[0019] However, the higher the EGR rate, the greater the risk of the air-to-fuel ratio (AFR) in the cylinder becoming excessively low. The air-to-fuel ratio is the mass ratio of solid, liquid, or gaseous fuels present during the combustion process.

[0020] The EGR rate can be measured in a combustion engine that uses EGR to optimize the combustion process by measuring the O2 concentration at the front and rear of the engine, for example, in the scavenging receiver and at the exhaust port. Alternatively, the EGR rate can be calculated by measuring the CO2 concentration in the exhaust gas and the scavenging packing.

[0021] International Patent Publication No. 2011 / 076837A1 teaches how to measure and control the EGR rate, and how to determine the EGR mass flow from the total exhaust mass flow through the cylinder and the turbine mass flow through the turbine. [Prior art documents] [Patent Documents]

[0022] [Patent Document 1] European Patent Application Publication No. 3722572A1 [Patent Document 2] European Patent Application Publication No. 3081890A1 [Patent Document 3] International Patent Application Publication No. 2011 / 076837A1 [Non-patent literature]

[0023] [Non-Patent Document 1] Guzzella, Onder: "Introduction to Modeling and Control of Internal Combustion Engine Systems," ISBN 3-540-22274-x, Springer-Verlag, Berlin, 2004. [Non-Patent Document 2] User manual for Mitsubishi METurbo TZ-E002-5573, "Guideline for MET turbocharger project," April 2017, pages 54 onwards. [Overview of the Initiative] [Problems that the invention aims to solve]

[0024] An object of the present invention is to avoid the shortcomings of the prior art, and in particular to provide an internal combustion engine and a method for operating an internal combustion engine that enables precise setting of engine parameters. [Means for solving the problem]

[0025] According to the present invention, the internal combustion engine is a large marine engine or stationary engine capable of operating in at least gas mode.

[0026] The internal combustion engine has at least one cylinder having an inner diameter of at least 200 mm.

[0027] An internal combustion engine may have at least one gas intake valve for supplying fluid fuel to the cylinder. The fluid fuel may be a fuel gas or a high-pressure fuel liquid that vaporizes upon entering the cylinder.

[0028] The internal combustion engine has at least one supercharger having at least one turbine and at least one compressor.

[0029] A supercharger uses exhaust gases expelled from the cylinder to increase the amount of air supplied to the cylinder. The air compressed by the supercharger can be supplied to a scavenging receiver that is fluidly connected to the intake air passage opening.

[0030] The internal combustion engine has a low-pressure exhaust gas recirculation path with an EGR valve.

[0031] For low-pressure exhaust gas recirculation, the exhaust gases pass through the turbocharger turbine and / or the turbocharger compressor before being mixed with the atmosphere and / or entering the cylinders as part of the scavenging air. In this case, the EGR path typically branches off downstream of the turbine.

[0032] The internal combustion engine further includes a first measuring unit for providing a signal representing the excess-air ratio in the low-pressure exhaust gas recirculation path.

[0033] The first measuring unit may have a lambda sensor located downstream of the EGR valve. Lambda λ, also known as the air-fuel equivalent ratio, is the ratio of the actual air-fuel ratio to a given mixture according to stoichiometry. λ = 1.0 means the mixture is stoichiometric, λ < 1.0 for rich mixtures, and λ > 1.0 for lean mixtures.

[0034] The air-fuel equivalent ratio should always be greater than 1. Typically, at a 50% EGR rate, the lambda λ is 1.5.

[0035] The excess air ratio may be specified by the air-fuel ratio or by the air-fuel equivalent ratio λ.

[0036] Typically, a lambda sensor measures the proportion of oxygen (O2) in the gas being analyzed, in this case, the recirculated exhaust gas. If the type of fuel is known, the air-fuel equivalent ratio can be determined from the oxygen content, and the theoretical air quantity requirement can be determined accordingly.

[0037] Standard broadband lambda probes perform very well within the lambda range of approximately λ 1.5 to 1.7.

[0038] For example, the ETAS ES63x lambda module can be used as a measurement unit with a standard broadband lambda probe for any common fuel.

[0039] Therefore, it will be possible to calculate the EGR rate through lambda measurement in the exhaust gas, fuel consumption, and turbine mass flow calculations.

[0040] Knowing the air-fuel equivalent ratio of the exhaust gas allows for the determination of further values ​​for controlling combustion.

[0041] The internal combustion engine may have a second measuring unit having at least one sensor for providing a signal representing ambient pressure, and preferably at least one sensor for providing a signal representing ambient temperature.

[0042] The internal combustion engine may further include a third measuring unit having at least one sensor for providing a signal representing the pressure downstream of the turbine, at least one sensor for providing a signal representing the pressure upstream of the turbine, and at least one sensor for providing a signal representing the temperature upstream of the turbine.

[0043] The internal combustion engine may further include a first control unit configured to receive signals from a first measuring unit, a second measuring unit, and a third measuring unit.

[0044] Preferably, the first control unit is configured to determine the turbine mass flow based on the upstream and downstream pressures and the upstream temperature, respectively.

[0045] As disclosed in International Patent Publication No. 2011076837A1, turbine mass flow m turbineThe calculation can be performed by applying well-known equations derived from a turbine model, which is determined by using known mathematical formulas similar to the throttle equation, for example. This model is described, for example, in Guzzella, Onder: "Introduction to Modeling and Control of Internal Combustion Engine Systems," ISBN 3-540-22274-x, Springer-Verlag, Berlin, 2004.

[0046] Typically, as can be seen in the user manual for Mitsubishi METurbo TZ-E002-5573, "Guideline for MET turbocharger project," April 2017, pp. 54 et seq., each turbocharger is given individual turbine flow characteristics. The gas flow rate, in kg / s units, is given as a function of turbine flow parameters that have a characteristic relationship with the temperature and pressure before the turbine, ambient temperature and pressure, and the turbine pressure ratio.

[0047] Turbine Mass Flow m turbine This is part of the exhaust gas that passes through the turbine. If the wastegate is open, another part of the exhaust gas passes through it. In the engine's gas mode, the wastegate remains closed.

[0048] Alternatively, turbine mass flow m turbine Alternatively, the "Exh mass flow rate, turbine-in" can be calculated from the energy balance of the turbocharger.

number

[0049] "p5 turbine-in" is the turbine-upstream pressure, which can be measured between the exhaust receiver and the turbine, preferably near the turbine. "p0 ambient" is the ambient pressure, which can be measured anywhere in the engine, for example.

[0050] The term "psi1" is

number

number

[0051] The first control unit may be configured to determine the EGR rate based on signals from the first measurement unit, the second measurement unit, and the third measurement unit, particularly the turbine mass flow signal.

[0052] Typically, ambient pressure and ambient temperature values ​​are available in a given control unit of the ship's motor. Alternatively, the first control unit may have input lines for receiving signals representing ambient pressure and preferably ambient temperature from an external device. The first control unit may use these values ​​to determine the EGR rate.

[0053] Exhaust gas recirculation rate or EGR rate X EGR For example, the following ratio:

number

[0054] In these equations, m turbineis the mass flow rate through the turbine, m fuel is the fuel mass flow rate, λ exhaust is the air-fuel equivalence ratio in the exhaust gas measured by the first measurement unit, L ST is the theoretical air requirement or the theoretical air-fuel ratio.

[0055] To determine the mass flow rate through the turbine, for example, as described above, the ambient pressure needs to be known.

[0056] The fuel mass flow rate m fuel is usually available in a given control unit of the marine motor. Additionally or alternatively, the first control unit is configured to determine the fuel mass flow rate based on information about the amount and type of fuel actually used in the combustion engine.

[0057] Typically, combustion can be controlled by setting the EGR rate. However, the combustion control should be able to adjust the EGR rate in an accurate manner. To enable accurate combustion control, the determination of the actual EGR rate is important.

[0058] The first control unit can be configured to compare the determined EGR rate with a pre-determined value and / or a pre-determined interval. The pre-determined value and / or the pre-determined interval may be determined in field tests, or may be taken from a map, or may be selected according to a pressure curve.

[0059] The set points generally depend on the load. They may vary depending on the type of engine and may depend on the bore size. The set points may also depend on the engine speed and output.

[0060] The first control unit can be configured to generate a signal if the EGR rate is greater or less than a pre-determined value and / or a pre-determined interval. The internal combustion engine may have a monitor for displaying the signal. The monitor can be a visual and / or an audible monitor.

[0061] As a result, the user can recognize if the EGR rate has reached an undesirable value, and in this case, stop or modify the control process. This helps avoid setting the EGR rate in an unreasonable way.

[0062] The first control unit may be configured to determine the difference between the determined EGR rate and a predetermined value and / or interval.

[0063] The first control unit may be configured to respond to a determined EGR rate that is greater than or less than a predetermined value and / or predetermined interval by stopping and / or correcting the control process that sets a new EGR rate.

[0064] Combustion control may allow for adjustment of the EGR rate.

[0065] To perform this in an accurate manner, a method for determining the actual EGR rate is proposed.

[0066] An internal combustion engine may have a second control unit configured to regulate the flow of exhaust gases in the EGR path. The second control unit may be part of the first control unit. The first and / or second control units may be part of an engine control system.

[0067] A second control unit may be configured to adjust the flow of exhaust gas in the EGR path based on signals representing combustion parameters, emission levels, engine performance, ambient conditions, fuel characteristics, and / or the air-fuel ratio in the cylinder.

[0068] The second control unit may be configured to take into account the determined EGR rate when adjusting the flow of exhaust gas in the EGR path.

[0069] Combustion parameters are parameters that indicate the characteristics of combustion, such as peak cylinder pressure, premature ignition, knocking and / or misfire events, or beta value β.

[0070] The beta value β is a parameter related to the pressure increase during combustion. β=(p max -p comp ) / (θ pmax -θ PIT ) In the above equation, p max θ is the maximum cylinder pressure, pmax The crank angle at which the maximum cylinder pressure is reached is p comp θ is the cylinder pressure reached after compression. PIT This is the crank angle at which pilot fuel is injected.

[0071] Emission levels are NO in exhaust gases. x These are parameters that indicate the characteristics of exhaust gas quality, such as the CH4 value.

[0072] Engine performance refers to parameters that indicate the characteristics of engine output, such as the temperature at the turbine outlet.

[0073] Ambient conditions are parameters that describe the characteristics of the environment, such as ambient temperature, ambient humidity, and / or ambient pressure.

[0074] Fuel characteristics refer to the properties of the fuel being used, such as fuel quality, methane number, or calorific value.

[0075] Taking the determined EGR rate into account may mean that the second control unit may be configured to compare the EGR rate with a predetermined value and / or predetermined interval, and / or to perform further processing using the difference between the EGR rate and the predetermined value and / or predetermined interval provided by the first control unit.

[0076] The second control unit may be configured to stop adjusting the EGR rate, correct the adjustment of the EGR rate, change parameters other than the EGR rate, and / or trigger maintenance if the determined EGR rate is too low or too high, or if the difference from a predetermined EGR rate value reaches a predetermined level.

[0077] An internal combustion engine may have a third control unit configured to receive signals from a first measuring unit and to determine the air-fuel ratio or air-fuel equivalent ratio (λ) in the cylinder based on signals from the first measuring unit and from second and third measuring units. Alternatively or additionally, the air-fuel ratio or air-fuel equivalent ratio (λ) in the cylinder based on signals from the first measuring unit and signals from the first control unit.

[0078] The in-cylinder lambda value can be determined by the following formula: λ cylinder =(m L +m L,EGR ) / (L ST *m fuel )

[0079] In this formula, m fuel m is the fuel mass flow rate. L L is the mass flow rate of air entering the combustion chamber. ST This is the stoichiometric air-fuel ratio, m L,EGR This is the air equivalent oxygen mass flow rate from the recirculated exhaust gas.

[0080] Air equivalent oxygen mass flow rate m from recirculated exhaust gas L,EGR The following formula m L,EGR =m EGR *w O2 / 0.232 It can be limited by the above formula, and m EGR w is the mass flow rate of the recirculated exhaust gas, O2 This is the mass fraction of oxygen in the air.

[0081] The mass flow rate of the recirculated exhaust gas is related to the exhaust gas recirculation rate by the following equation. m EGR =m L / X EGR / (1-X EGR )

[0082] The mass fraction of oxygen in the air w O2 teeth w O2 =ν O2,exhaust *0.232 / 0.2095 It can be limited by the above equation, and ν O2,exhaust This is the mole fraction of oxygen in the exhaust gas.

[0083] mole fraction ν O2 The general formula is as follows: ν O2 =(λ exhaust -1) / (4.76λ exhaust +(H B / C B ) / (H B / C B +4)) It can be calculated by the above formula, and H B This is the hydrogen content of the fuel, C B H is the carbon content of the fuel. B and C B This is a quantity specific to the fuel. In the case of CH4, H B The value of C is considered to be 4. B The value is considered to be 1.

[0084] λ exhaust It is measured in exhaust gas using a lambda probe.

[0085] In this case, if the fuel used, the mass flow rate of the exhaust gas, and the lambda are known, the EGR rate and the in-cylinder lambda can be calculated.

[0086] Both values ​​can be used to accurately monitor the combustion process and to improve the control of the combustion process.

[0087] According to the present invention, a method for operating an internal combustion engine as described above includes the step of providing a signal representing the excess air ratio in the low-pressure exhaust gas recirculation path.

[0088] This value can be used to monitor the combustion process and to improve the control of the combustion process.

[0089] The method may further include the steps of providing a signal representing ambient pressure and preferably a signal representing ambient temperature, a signal representing pressure downstream of the turbine, a signal representing a pressure sensor upstream of the turbine, and a signal representing temperature upstream of the turbine.

[0090] The method may further include the step of determining the EGR rate based on a signal representing the excess air ratio in the low-pressure exhaust gas recirculation path, a signal representing the ambient pressure, a signal representing the pressure downstream of the turbine, a signal representing the pressure upstream of the turbine, and / or a signal representing the temperature upstream of the turbine.

[0091] Preferably, the turbine mass flow is determined based on the upstream temperature and / or ambient pressure for both the upstream and downstream pressures, respectively.

[0092] Furthermore, the air-fuel ratio or air-fuel equivalent ratio (λ) in the cylinder can be determined based on a signal representing the excess air ratio in the low-pressure exhaust gas recirculation path.

[0093] The present invention will be further described below with reference to examples and figures. The same reference numerals indicate functionally corresponding features. [Brief explanation of the drawing]

[0094] [Figure 1] This is a schematic diagram of an internal combustion engine. [Figure 2] This is a schematic representation of further examples of internal combustion engines. [Modes for carrying out the invention]

[0095] Figure 1 shows a first example of an internal combustion engine 10 having a cylinder 11 with a reciprocating piston 9 having an inner diameter 12 of at least 200 mm. The internal combustion engine 10 has a system for exhaust gas recirculation, with an EGR path 16 located between the exhaust outlet 31 and the air inlet 32 ​​of the cylinder 11. The internal combustion engine 10 has a supercharger 13 having a turbine 14 and a compressor 15.

[0096] The exhaust gas recirculation system is a low-pressure system, and the recirculated exhaust gas can be guided through the compressor 15 of the supercharger 13 to the air inlet 32 ​​of the cylinder 11, where the exhaust gas is mixed with the atmosphere. In this example, the exhaust gas can be guided through the turbine 14 of the supercharger 13, and the EGR path 16 branches downstream of the turbine 14.

[0097] The amount of recirculated exhaust gas can be controlled by setting the EGR valve 17 and the back pressure valve 29.

[0098] A first measurement unit 18 is located downstream of the EGR valve 17. The measurement unit 18 has a lambda sensor and provides a signal to the first control unit 20 representing the excess air ratio in the low-pressure exhaust gas recirculation path.

[0099] The combustion engine may have a second measuring unit 8 (see Figure 2) which has at least one sensor 2 (see Figure 2) for providing a signal representing ambient pressure and at least one sensor 3 (see Figure 2) for providing a signal representing ambient temperature.

[0100] The third measurement unit 19 is located near the turbine 19.

[0101] The first control unit may calculate the EGR rate based on signals from the first measurement unit 18, the second measurement unit 8 (see Figure 2), and / or the third measurement unit 19.

[0102] The internal combustion engine 10 has a second control unit 21 configured to adjust the flow of exhaust gas in the EGR path 16 by setting a back pressure valve 29.

[0103] The second control unit 21 adjusts the flow of exhaust gas in the EGR path based on combustion parameters. Combustion parameters can be determined from signals received from the cylinder measuring unit 33, which provides, for example, pressure measurements in the cylinder 11, particularly the peak combustion pressure, premature ignition, knocking and / or misfire events, or β values.

[0104] Figure 2 shows a schematic representation of a further example of the internal combustion engine 10.

[0105] At least one exhaust gas from cylinder 11 (see Figure 1) is collected in the exhaust gas receiver 27 and can be recirculated to the scavenging air receiver 28 via the turbine 14 and compressor 15 of the supercharger 13.

[0106] The low-pressure EGR path 16 branches off downstream of the turbine 14. The EGR path has an EGR valve 17. Downstream of the junction to the EGR path is a back pressure valve 29 which can be used to control the amount of exhaust gas that is recirculated.

[0107] Furthermore, the EGR path may include a blower not shown in the diagram.

[0108] A first measurement unit 18 is located downstream of the EGR valve 17. This example shows two typical locations for the first measurement unit 18: upstream and downstream of the EGR cooler 24.

[0109] The combustion engine may have a second measuring unit 8 having at least one sensor 2 for providing a signal representing ambient pressure and at least one sensor 3 for providing a signal representing ambient temperature.

[0110] The third measurement unit 19 (see Figure 1) includes a sensor 22b for providing a signal representing the pressure downstream of the turbine 14, a sensor 22a for providing a signal representing the pressure upstream of the turbine 14, a sensor 23a for providing a signal representing the temperature upstream of the turbine 14, and a sensor 23b for providing a signal representing the temperature downstream of the turbine 14.

[0111] The temperature downstream of the turbine corresponds to the temperature of the exhaust gas upstream of the EGR cooler 24. The temperature can be used to calculate the adiabatic index κ of the exhaust gas.

[0112] The exhaust gas is mixed with the atmosphere 33 and guided to the scavenging air receiver 28 via the scavenging air cooler 25 and finally via the blower 26.

Claims

1. An internal combustion engine (10), i.e. a large marine engine or a stationary engine, capable of operating at least in gas mode, The internal combustion engine (10) has at least one cylinder (11) with an inner diameter (12) of at least 200 mm; The internal combustion engine (10) has a turbocharger (13) having a turbine (14) and a compressor (15), The internal combustion engine (10) has a low-pressure exhaust gas recirculation path (16) having an EGR valve (17), The internal combustion engine (10) further comprises a first measuring unit (18) for providing a signal representative of the excess air fraction in the low pressure exhaust gas recirculation path.

2. An internal combustion engine (10) as described in claim 1, wherein the first measuring unit has a lambda sensor arranged downstream of the EGR valve (17).

3. the internal combustion engine (10) has a second measuring unit (8), the second measuring unit (8) comprising at least one sensor (2) for providing a signal representative of the ambient pressure; the internal combustion engine (10) has a third measuring unit (19) comprising at least one sensor (22b) for providing a signal representative of a pressure downstream of the turbine (14), at least one sensor (22a) for providing a signal representative of a pressure upstream of the turbine (14), and / or at least one sensor (23a) for providing a signal representative of a temperature upstream of the turbine (14); and The internal combustion engine (10) has a first control unit (20), the first control unit (20) - receiving a signal from said first measurement unit (18); - receiving a signal from said second measurement unit (8), - receiving a signal from said third measurement unit (19); and determining the EGR rate based on the signals from the first measuring unit (18), the second measuring unit (18) and the third measuring unit (19); 2. The internal combustion engine (10) of claim 1, wherein the internal combustion engine (10) is configured as follows:

4. An internal combustion engine (10) as described in claim 3, wherein the second measuring unit (8) comprises at least one sensor (3) for providing a signal representative of the ambient temperature.

5. An internal combustion engine (10) as described in claim 3, wherein the first control unit (20) is configured to determine turbine mass flow based on each of the upstream and downstream pressures and the upstream temperature.

6. 4. The internal combustion engine (10) of claim 3, wherein the first control unit (20) is configured to compare the determined EGR rate with a predetermined value and / or a predetermined interval.

7. 7. The internal combustion engine (10) of claim 6, wherein the first control unit (20) is configured to generate a signal when the EGR rate is greater than or less than the predetermined value and / or the predetermined interval.

8. 8. The internal combustion engine (10) of claim 7, wherein the internal combustion engine has a monitor for displaying the signal.

9. The internal combustion engine has a second control unit (21), the second control unit (21) combustion parameters, - emission levels, - engine performance, ambient conditions, fuel properties, and - the air-fuel ratio or air-fuel equivalence ratio (λ) in said cylinder and 4. The internal combustion engine (10) of claim 3, wherein the second control unit is configured to take the determined EGR rate into account when adjusting the flow of exhaust gas in the EGR path.

10. - the combustion parameters are combustion peak pressure, pre-ignition, knocking and / or misfire events, or beta value, - the emission level is the NO x value or the CH 4 value in the exhaust gas; - the engine performance is the temperature at the turbine outlet; - said ambient conditions are at least one of temperature, humidity and pressure; The fuel property is fuel quality, methane number, or calorific value.

10. The internal combustion engine (10) according to claim 9, characterized by at least one of the following:

11. The internal combustion engine (10) has a third control unit (16), the third control unit comprising: - receiving a signal from said first measurement unit (18); - determining the air-fuel ratio or air-fuel equivalence ratio (λ) in said cylinder (11) based on said signal from said first measuring unit (18); 4. An internal combustion engine (10) according to claim 3, configured as follows:

12. 2. A method for operating an internal combustion engine (10) according to claim 1, comprising: - providing a signal representative of the excess air ratio in said low pressure exhaust gas recirculation path; A method comprising:

13. - providing a signal representative of the ambient pressure and a signal representative of the ambient temperature; - providing a signal representative of a pressure downstream of the turbine (14), a signal representative of a pressure sensor upstream of the turbine (14), and a signal representative of a temperature upstream of the turbine (14); determining the EGR rate based on the signal representative of the excess air rate in the low pressure exhaust gas recirculation path (16), the signal representative of the pressure downstream of the turbine (14), the signal representative of the pressure upstream of the turbine (14), and the signal representative of the temperature upstream of the turbine (14); The method of claim 12 further comprising:

14. The method of claim 13, further comprising a step of determining the turbine mass flow based on each of the upstream and downstream pressures and the upstream temperature.

15. 13. The method of claim 12, further comprising determining an air-fuel ratio or air-fuel equivalence ratio (λ) in the cylinder (10) based on a signal representative of an excess air fraction in the low pressure exhaust gas recirculation path (16).

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