SE541367C2

SE541367C2 - Method and system for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine

Info

Publication number: SE541367C2
Application number: SE1751045A
Authority: SE
Inventors: Moreno Carlos Jorques; Ola Stenlåås; Per TUNESTÅL
Original assignee: Scania Cv Ab
Priority date: 2017-08-31
Filing date: 2017-08-31
Publication date: 2019-08-27
Also published as: SE1751045A1; WO2019045623A1

Abstract

The present disclosure relates to a method 400 for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine. The method comprises the step 420 of determining a pressure inside the combustion chamber. The method further comprises the step 430 of determining the possible start of vaporisation of the injected pilot fuel. The method even further comprises the step 435 of determining the possible start of combustion of the injected pilot fuel. The pilot injection fuel mass is determined 460 based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion.The present disclosure further relates to a method for controlling an injection to a combustion chamber of an engine, to a method for controlling an injection to a second combustion chamber of an engine, to a system for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine, to a vehicle, to a computer program product and to a computer-readable storage medium.

Description

Method and system for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine TECHNICAL FIELD The present disclosure relates to a method and a system for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine. The present disclosure further relates to a vehicle, a computer program product, and a computer-readable storage medium. The present disclosure even further relates to a method for controlling an injection to a combustion chamber of an engine and to a method for controlling an injection to a second combustion chamber of an engine BACKGROUND ART Pilot injections are sometimes used at combustion engines for injecting a small amount of fuel into a combustion chamber of the engine prior to the main injection. The amount of fuel injected during the pilot injection is generally only a small fraction of the amount of fuel of the main injection. The time of injection and the amount of the fuel injected during the pilot injection are sensitive to many variables, such as the geometry of an injector, variations in the fuel pressure, variations in the temperature of the fuel and/or the combustion chamber, quality of the fuel, variations in the flow current of the fuel, and the like.

All this leads to a considerable uncertainty regarding the amount of injected fuel during pilot injection, and regarding how much of that fuel has burned prior the start of subsequent injections. It might happen that no fuel at all is burned during pilot injection due to the variations and influences described above. These variations and uncertainties thus can lead to variations in performance of the engine and to variations in emissions, for example NOx-emissions, the sound of the engine, properties of the particulate matter, PM, and the like.

There is thus a need to gain better information regarding the pilot injection and/or to alleviate some of the above mentioned effects.

There is also a need to minimise NOx-emissions, the noise of the engine, potentially harmful properties of the PM, and the like.

SUMMARY OF THE INVENTION It is thus an objective of the present disclosure to gain better information regarding the pilot injection and/or to alleviate some of the above mentioned effects.

It is a further objective of the present disclosure to minimise any of NOx-emissions, the noise of the engine, potentially harmful properties of the PM.

It is a further objective of the present disclosure to present alternatives to the hitherto known methods and systems.

At least some of the objectives are achieved by a method for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine. The method comprises the step of determining a pressure inside the combustion chamber. The method further comprises the step of determining the possible start of vaporisation of the injected pilot fuel. The method even further comprises the step of determining the possible start of combustion of the injected pilot fuel. The pilot injection fuel mass is then determined based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion.

Therefore a better knowledge regarding the fuel mass of the pilot injection can be gained. Since the method relates, at least to a larger amount, to what happens after the fuel mass has been entered the combustion chamber, this better knowledge can especially consider any effects of an injector or an injection process into the combustion chamber. This is achieved without the need to know these effects in detail. Thus, wear, variations, and the like can be taken care of.

In one example, the pressure inside the combustion chamber is determined based on a measurement of a pressure sensor in the combustion chamber. This allows for an especially fast implementation of the method. It might especially reduce the needed computational power for performing the method. As an example, the pressure can be related to the heat release inside the combustion chamber. Several of the determinations of the method can in its turn be easily related to the heat release.

In one example, the method further comprises the step of providing a first model for determining the vaporisation delay of the injected pilot injection fuel. The first model is based on an estimated pilot injection fuel mass. The method further comprises the step of determining a first estimation for the pilot injection fuel mass based on the determined possible start of vaporisation of the injected pilot injection fuel and based on an inversion of the first model. This allows for a computational easy determination of the fuel mass.

In one example, the method further comprises the step of providing a second model for determining the combustion delay of the injected pilot injection fuel. The second model is based on an estimated pilot injection fuel mass. The method further comprises the step of determining a second estimation for the pilot injection fuel mass based on the determined possible start of combustion of the injected pilot injection fuel and based on an inversion of the second model. This allows for a computationally easy determination of the fuel mass.

In one example, the determining of the pilot injection fuel mass comprises an estimating method, such as, for example, applying a Kalman filter, Extended Kalman Filter, neural networks, particle filter. This provides an especially robust method.

In one example, the determining of the pilot injection fuel mass comprises iteratively performing estimations for the pilot injection fuel mass during different volumes in the combustion chamber and/or different orientations of a crank shaft connected to the combustion chamber. Hereby, the determined pilot injection fuel mass corresponds to the estimated pilot injection fuel mass when it is determined that the combustion in the combustion chamber during the pilot ends. Due to the iterations an especially robust result is achieved.

In one example, the method further comprises the step of estimating a vaporised mass of the pilot injection fuel. The method further comprises estimating a combusted mass of the pilot injection fuel. The method even further comprises determining the pilot injection fuel mass based on the estimated vaporised and/or combusted mass of the pilot injection fuel. This allows for an even more accurate result.

At least some of the objectives are achieved by a method for controlling an injection to a combustion chamber of an engine. The method comprises the step of determining in-cycle a pilot injection fuel mass in the combustion chamber of the engine according to the present disclosure. The method further comprises controlling a later injection to the combustion chamber based on the determined pilot injection fuel mass. This controlling is preferably performed in such a way that at least some of the emissions of the combustion process are reduced, such as NOx-emissions, the noise of the engine, potentially harmful properties of the PM, and the like. The better the knowledge of the actual fuel mass of the pilot injection, the more accurate can any later adaption be performed and thus the better can the emissions be reduced.

At least some of the objectives are achieved by a method for controlling an injection to a second combustion chamber of an engine. The method comprises the step of determining incycle a pilot injection fuel mass in a first combustion chamber of the engine according to the present disclosure. The method further comprises the step of controlling an injection to a second combustion chamber based on the determined pilot injection fuel mass of the first combustion chamber. Herein, the first and the second combustion chamber are different combustion chambers. This method has the same advantages as the previous described method.

At least some of the objectives are achieved by a system for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine. The system comprises means for determining a pressure inside the combustion chamber. The system further comprises means for determining the possible start of vaporisation of the injected pilot fuel. The system even further comprises means for determining the possible start of combustion of the injected pilot fuel. The system yet even further comprises means for determining the pilot injection fuel mass based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion.

In one embodiment, the means for determining a pressure inside the combustion chamber comprise a pressure sensor in the combustion chamber.

In one embodiment, the means for determining the possible start of vaporisation of the injected pilot fuel and/or the means for determining the possible start of combustion of the injected pilot fuel and/or the means for determining the pilot injection fuel mass comprise a field programmable gate array, FPGA. This allows for an especially fast performance of the system.

At least some of the objectives are achieved by a vehicle, comprising the system according to the present disclosure.

At least some of the objectives are achieved by a computer program product. The computer program product comprises instructions which, when the program is executed by a computer, cause the computer to carry out any of the methods of the present disclosure.

At least some of the objectives are achieved by a computer-readable storage medium. The medium comprises instructions which, when executed by a computer, cause the computer to carry out any of the methods of the present disclosure.

The system, the vehicle, the computer program product and the computer-readable storage medium have corresponding advantages as have been described in connection with the corresponding examples of the method according to this disclosure.

Further advantages of the present invention are described in the following detailed description and/or will arise to a person skilled in the art when performing the invention.

BRIEF DESCRIPTION OF THE DRAWINGS For a more detailed understanding of the present invention and its objects and advantages, reference is made to the following detailed description which should be read together with the accompanying drawings. Same reference numbers refer to same components in the different figures. In the following, Fig. 1 shows, in a schematic way, a vehicle according to one embodiment of the present invention; Fig. 2 shows, in a schematic way, a system according to one embodiment of the present invention; Fig. 3a-c show, in a schematic way, examples of how different physical variables relate to each other when performing the present disclosure; Fig. 4a shows, in a schematic way, a flow chart over an example of a method for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine; Fig. 4b shows, in a schematic way, a flow chart over an example of a method for controlling an injection to a combustion chamber of an engine; Fig. 4c shows, in a schematic way, a flow chart over an example of a method for controlling an injection to a second combustion chamber of an engine; and Fig. 5 shows, in a schematic way, a device which can be used in connection with the present invention.

DETAILED DESCRIPTION Fig. 1 shows a side view of a vehicle 100. In the shown example, the vehicle comprises a tractor unit 110 and a trailer unit 112. The vehicle 100 can be a heavy vehicle such as a truck. In one example, no trailer unit is connected to the vehicle 100. The vehicle 100 comprises a combustion engine. The vehicle comprises a system 299 for determining in-cycle a pilot injection fuel mass in a combustion chamber of the engine. In the following, the terms engine and combustion engine are used interchangeably. No different meaning is intended. The system 299 is described in more detail in relation to Fig. 2a. The system 299 can be arranged in the tractor unit 110.

In one example, the vehicle 100 is a bus. The vehicle 100 can be any kind of vehicle comprising a combustion engine. Other examples of vehicles comprising a combustion engine are boats, passenger cars, construction vehicles, and locomotives. The present invention can also be used in connection with any other platform than vehicles, as long as this platform comprises a combustion engine. One example is a power plant with a combustion engine.

The innovative method and the innovative system according to one aspect of the invention are also well suited to, for example, systems which comprise industrial engines and/or enginepowered industrial robots.

In the following, the system 299 will be described as it can be embodied when using it in a vehicle. As a consequence, not all components in the description are necessary. Instead, most of the components are optional. They are, however, added in the description for showing a preferred embodiment of the present disclosure.

The term "link" refers herein to a communication link which may be a physical connection such as an opto-electronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link.

Throughout the application, the term "in-cycle" relates to the fact that the determination of the fuel mass is performed during the thermodynamic cycle in a combustion chamber in which the fuel mass is injected. In other words, the determination of the fuel mass does not require that the combustion is finished before the determination of the fuel mass can be performed.

Fig. 2 shows, in a schematic way, a system 299 according to one embodiment of the present invention. The system 299 can perform any of the method steps described later in relation to Fig. 4.

The system 299 can comprise a combustion engine 210. The engine 210 comprises at least one combustion chamber. In one example, the at least one combustion chamber comprises a first cylinder 240. The at least one combustion chamber can comprise a second cylinder 241. The at least one combustion chamber can comprise any number of cylinders. In the following, several aspects of the disclosure are exemplified on the first and/or second cylinders 240, 241, but it should be emphasised that any other combustion chamber than a cylinder would work as well. In the following the term first might be omitted when referring to the first cylinder 240.

The system 299 can comprise a fuel tank 220. The fuel tank 220 can comprise fuel for a main injection and/or a pilot injection. The system 299 can comprise a fuel ray 260 connected to the fuel tank. The fuel ray 260 can be arranged to transport the fuel from the fuel tank 220 to the first and/or second cylinder 240, 241. The system 299 can comprise a fuel injector 250. The fuel injector 250 can be arranged to inject the fuel from the fuel ray 260 into the cylinder 240.

Instead of a fuel ray 260 any other fuel transport arrangement can be used. The injector 250 can be arranged to inject a pre-determined amount of fuel into the cylinder 240. It should be understood that what is described here and in the following in relation to the cylinder usually refers to the space in the cylinder which forms the combustion chamber. The pre-determined amount of fuel can vary from injection to injection. As an example, the pre-determined amount of fuel injected can be different between a pilot injection and a main fuel injection. In general, the pre-determined amount of fuel is not directly controlled by a fuel amount sensor. Instead, the amount of fuel is usually controlled by controlling the opening time of the injector. Instead and/or additionally the amount of fuel can be controlled by any other variable which can be transferred to the fuel amount. In general, the actually injected amount of fuel can deviate from the pre-determined amount of fuel. This can be due to any of the effects described in the background section, due to wear of components, or due to any other reason.

The injector 250 can be arranged to inject a pilot injection into the cylinder 240. The injector can be arranged to inject a main injection into the cylinder 240.

The system 299 can comprise a first control unit 200. The first control unit 200 can be arranged for communication with the injector 240 via a link L240.The first control unit can be arranged to control the injector 250. The first control unit can be arranged to open the injector 250 for a pre-determined amount of time so that fuel is inserted into the cylinder during that opening time. The first control unit 200 can be arranged to receive information from the injector 250.

The system 299 comprises means for determining a pressure inside the cylinder 240. The means for determining a pressure inside the cylinder can be embodied by a pressure sensor 245 or can comprise the pressure sensor 245. The pressure sensor 245 can be arranged to measure the pressure inside the cylinder 240, i.e. inside the combustion chamber. The first control unit 200 can be arranged for communication with the pressure sensor 245 via a link L245.The first control unit can be arranged to control the pressure sensor 245. The first control unit 200 can be arranged to receive information from the pressure sensor 245, such as a measured pressure value.

The means for determining a pressure inside the cylinder 240 can comprise a first virtual sensor. The first virtual sensor can be arranged to determine the pressure inside the cylinder 240. The determining of the pressure inside the cylinder can be based on information from a knock sensor (not shown in the figure). The determining of the pressure inside the cylinder can be based on information from an ion current sensor (not shown in the figure). The means for determining the pressure inside the cylinder 240 can comprise the first control unit 200. The first control unit 200 can be arranged to perform partly or in total the functioning of the first virtual sensor.

The system 299 can comprise means for determining a temperature inside the cylinder 270. The means for determining a temperature inside the cylinder can be embodied by a temperature sensor 270 or can comprise the pressure sensor 270. The temperature sensor 270 can be arranged to measure the temperature inside the cylinder 240, i.e. inside the combustion chamber. The first control unit 200 can be arranged for communication with the temperature sensor 270 via a link L270.The first control unit can be arranged to control the temperature sensor 270. The first control unit 200 can be arranged to receive information from the temperature sensor 270, such as a measured temperature value.

The means for determining a temperature inside the cylinder 240 can comprise a second virtual sensor. The second virtual sensor can be arranged to determine the temperature inside the cylinder 240. The means for determining the temperature inside the cylinder 240 can comprise the first control unit 200. The first control unit 200 can be arranged to perform partly or in total the functioning of the second virtual sensor.

The system 299 comprises means for determining the possible start of vaporisation of the injected pilot fuel. The means can comprise the pressure sensor 245 and/or the temperature sensor 270. The means can comprise the first control unit 200. In one example, the means for determining the possible start of vaporisation of the injected pilot fuel comprise a virtual sensor for determining the heat release in the combustion chamber.

The system 299 comprises means for determining the possible start of combustion of the injected pilot fuel. The means can comprise the pressure sensor 245 and/or the temperature sensor 270. The means can comprise the first control unit 200. In one example, the means for determining the possible start of combustion of the injected pilot fuel comprise a virtual sensor for determining the heat release in the combustion chamber.

In one example, the first control unit 200 is arranged to determine the possible start of vaporisation and/or combustion of the injected pilot fuel based on received information from the pressure and/or the temperature sensor 245, 270 and/or the virtual heat release sensor. This is further described in relation to Fig. 3 and 4.

The system comprises means for determining the pilot injection fuel mass based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion. The means can comprise the first control unit 200. In one example, the first control unit 200 comprises a field-programmable gate array, FPGA. This allows for a comparably fast system for determining the fuel mass of the pilot injection.

The system 299 can comprise a fuel ray pressure sensor 261. The fuel ray pressure sensor 261 can be arranged to measure the pressure inside the fuel ray 260. The first control unit 200 can be arranged for communication with the fuel ray pressure sensor 261 via a link L261.The first control unit can be arranged to control the fuel ray pressure sensor 261. The first control unit 200 can be arranged to receive information from the fuel ray pressure sensor 261, such as a measured pressure value inside the fuel ray.

The first control unit 200 can be arranged to detect the start of injection into the combustion chamber. This detection can be based on a dip in the pressure values inside the fuel ray.

The system 299 can comprise a fuel ray temperature sensor 262. The fuel ray temperature sensor 262 can be arranged to measure the temperature inside the fuel ray 260. The first control unit 200 can be arranged for communication with the fuel ray temperature sensor 262 via a link L262.The first control unit can be arranged to control the fuel ray temperature sensor 262. The first control unit 200 can be arranged to receive information from the fuel ray temperature sensor 262, such as a measured temperature value inside the fuel ray.

The first control unit 200 can be arranged to use detected values from the fuel ray temperature sensor 262 and/or the fuel ray pressure sensor 261 when determining the fuel mass of the injected fuel during pilot injection. In one example, the first control unit 200 is arranged to use detected values from the fuel ray temperature sensor 262 and/or the fuel ray pressure sensor 261 for setting boundary values for any of the models which will be described later in relation to Fig. 4.

The first control unit 200 can be arranged to control the injector 250 based on the determined fuel mass of the pilot injection. The first control unit 200 can be especially arranged to perform anything described later in relation to the method 480. As an example, the first control unit 200 can be arranged to adapt a later injection via the injector 250 based on the determined fuel mass of the pilot injection.

The first control unit 200 can be arranged to control an injector (not shown) which injects fuel into the second cylinder 241 based on the determined fuel mass of the pilot injection. The first control unit 200 can be especially arranged to perform anything described later in relation to the method 490. As an example, the first control unit 200 can be arranged to adapt a later injection via the injector which injects fuel into the second cylinder 241 based on the determined fuel mass of the pilot injection.

The system 299 can comprise a crank shaft 230. The crank shaft can be connected to the engine 210 via a piston arrangement 231. The angular orientation of the crank shaft 230 and/or the angular orientation and/or longitudinal position of the piston arrangement can be arranged to define the volume of the combustion chamber.

The system 299 can comprise a crank angle degree sensor 235, CAD sensor 235. CAD sensor 235 can be arranged to measure the crank angle degree of the crank shaft 230. The first control unit 200 can be arranged for communication with the CAD sensor 235 via a link L235. The first control unit can be arranged to control the CAD sensor 235. The first control unit 200 can be arranged to receive information from the CAD sensor 235. The first control unit 200 and/or the CAD sensor 235 can be arranged to determine the CAD and/or a rotational speed of the crank shaft 230. The first control unit 200 can be arranged to use the CAD and/or the rotational speed of the crank shaft 230 when performing any of the method steps described in relation to Fig. 4.

A second control unit 205 is arranged for communication with the first control unit 200 via a link L205 and may be detachably connected to it. It may be a control unit external to the vehicle 100. It may be adapted to conducting the innovative method steps according to the invention. The second control unit 205 may be arranged to perform the inventive method steps according to the invention. It may be used to cross-load software to the first control unit 200, particularly software for conducting the innovative method. It may alternatively be arranged for communication with the first control unit 200 via an internal network on board the vehicle. It may be adapted to performing substantially the same functions as the first control unit 200, such as adapting the control of the gas engine in a vehicle. The innovative method may be conducted by the first control unit 200 or the second control unit 205, or by both of them. In one example, the second control unit 205 comprises a field-programmable gate array, FPGA.

Fig. 3a-c show, in a schematic way, examples of how different physical variables relate to each other when performing the present disclosure. In these figures, the horizontal axis depicts the crank axis degree, CAD. The figures are simulation results and it should be understood that the shown values on the horizontal and vertical axes relate to a simulation of a specific situation and that these values might be different in different situation. As an example, the CAD might be different for different cylinders of an engine.

In Fig. 3a the heat release rate, HR rate, is denoted on the vertical axis, for example as J/CAD. The continuous curve 310 thus depicts the HR rate as a function of the CAD. Since the CAD changes due to the rotation of the engine, the depicted figure can be equally well seen as an evolution of the HR rate over time. At a first moment 311 the pilot injection fuel mass is injected into the combustion chamber. The first moment 311 relates to the actual pilot injection. For some moment of time, i.e. for some CAD, no change in the HR rate occurs. At a second moment 312, the injected fuel mass starts to vaporise. This can be seen by a decrease in the HR rate, especially in that the HR rate drops below zero. At a third moment 313 the injected fuel mass gets ignited, i.e. the combustion starts. This can be seen by an increase in the HR rate. The HR rate first rises until a peak and then decreases again, but remains above zero.

In Fig. 3b, different states of the injected fuel mass are depicted. The continuous line 320 relates to the injected fuel mass. The dashed line 322 relates to the vaporised fuel mass. The dotted line 321 relates to the premixed fuel mass. The line 323 which is dashed with different distances relates to the burned, i.e. combusted fuel mass. On the vertical axis the normalised mass flow is depicted. It should be observed that Fig. 4b depicts a simulated situation. Thus, in the model used, the injection is simulated to coincide with the start of the vaporisation. Thus, there is a shift in the injection between Fig. 4a and Fig. 4b. It should be emphasised that this shift is solely due to the chosen simulation and not due to a real shift. As will be clear later from the description of Fig. 4a, the vaporisation delay, i.e. the difference between the first and the second moment 311 and 312, will be determined in one step, for example step 430. This step is in general independent from a model which is used to determine in which state the injected fuel is at a specific moment of time and which is also described later in relation to step 450 and 455. However, it is possible to choose a model where the actual and the simulated start of ignition coincide.

In Fig. 3c the curves show the same states as in Fig. 4b. However, here the vertical axis denotes the normalised accumulated mass. As can be seen from the simulation in Fig. 4b and 4c, after same time all injected fuel has been vaporised. This complete vaporisation is delayed to the moment when all fuel is injected. After some time the fuel transfers into a premixed state at a high rate and a short moment thereafter starts to ignite. The accumulated burned fuel rises at a lower rate than the injected, the vaporised and the premixed fuel.

It should be emphasised that Fig. 3a-c are used for illustrative purposes only. Different simulations might be used. Other models might be used in relation to the present disclosure. Examples of other models which can be used in relation to the present disclosure are models comprising more or less states of the injected fuel, or different states of the injected fuel. As an example, a model might comprise diffusive combustion of the fuel. Another example of a model which might be used in relation to the present disclosure is a black-box model. Such a model might describe the heat release dynamics in the combustion chamber.

Fig. 4a shows, in a schematic way, a flow chart over an example of a method 400 for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine. The method 400 starts with the optional step 410.

In the optional step 410 a first model for a vaporisation delay of the injected pilot injection fuel is provided. The vaporisation delay relates to the time period between injection of the pilot injection fuel and the start of vaporisation of the injected fuel. The model for the vaporisation delay determines preferably the crank angle degree difference, CAD difference, ??, at which vaporisation starts based on the injected fuel mass during pilot injection, mpilot. In the following, the method 400 will be described in relation to CAD. This is due to the fact that measuring a CAD is comparably easy in vehicles. The CAD can be directly related to a current volume of the combustion chamber. Thus, whenever the description of the method 400 relates to CAD, it could alternatively relate to any other variable which can be transformed into the volume of the combustion chamber. This will especially be useful in case no crankshaft is connected to the engine. In one example, the vaporisation delay in the first vaporisation delay model is based on any of the following variables: engine speed, engine load, pressure inside the combustion chamber, temperature inside the combustion chamber, a first calibration parameter. In a preferred example, the vaporisation delay in the first vaporisation delay model is based at least on the pressure inside the combustion chamber. After step 410, the optional step 411 is performed.

In the optional step 411 a second model for a combustion delay of the injected pilot injection fuel is provided. The combustion delay relates to the time period between injection and/or vaporisation of a fuel and start of ignition of the injected fuel. The second model for the combustion delay determines preferably the crank angle degree difference, CAD difference, ??, at which ignition starts based on the injected fuel mass during pilot injection, mpilot. In one example, the combustion delay in the second combustion delay model is based on any of the following variables: engine speed, engine load, pressure inside the combustion chamber, temperature inside the combustion chamber, a second calibration parameter. In a preferred example, the second combustion delay in the combustion delay model is based at least on the pressure inside the combustion chamber. After step 411, step 420 is performed.

In step 420 the pressure inside the combustion chamber is determined. In one example, this is performed by a pressure sensor in the combustion chamber. This has the advantage in providing an especially fast way of providing the pressure inside the combustion chamber. In one example, the determination of the pressure inside the combustion chamber is performed by a virtual sensor. The method continues with the optional step 421.

In the optional step 421, at least one additional variable is determined. In one example, the at least one additional variable comprises the engine speed. Determining the engine speed is in one example performed with a crank angle degree sensor. It is well known in the art how to achieve the engine speed from a CAD sensor. In one example, the at least one additional variable comprises the engine load. In one example, the at least one additional variable comprises the temperature inside the combustion chamber. In one example, the temperature inside the combustion chamber is determined via a temperature sensor in the combustion chamber. The method continues with the step 430.

In step 430, the possible start of vaporisation of the injected pilot fuel is determined. Herein, the term possible relates to the fact that the fuel under certain circumstances might not vaporise at all. In that case, step 430 detects preferably that no vaporisation occurred. A reason for no vaporisation could be a miss injection. In one example, the start of vaporisation is determined based on the heat release, HR, and/or HR rate in the combustion chamber. This is illustrated in relation to Fig. 3. In one example, it is determined that the vaporisation starts when the HR rate turns negative. The method continues with step 435.

In step 435 the possible start of combustion of the injected pilot fuel is determined. Herein, the term possible relates to the fact that the fuel under certain circumstances might not ignite at all. In that case, step 430 detects preferably that no combustion occurred. A reason for no ignition might be a misfire. In one example, the start of combustion is determined based on the heat release, HR, and/or HR rate in the combustion chamber. This is illustrated in relation to Fig. 3. In one example, it is determined that the vaporisation starts when the HR rate is rising. The method continues with the optional step 440.

In the optional step 440 a first estimation for the pilot injection fuel mass is determined. The first estimation is based on the determined possible start of vaporisation of the injected pilot injection fuel. The first estimation is further based on an inversion of the first model. It should be understood that the possible start of vaporisation directly relates to the vaporisation delay. Since the first model provides a value for the vaporisation delay based on mpilot, an inversion of the first model provides a first estimation of mpilotwhen the start of vaporisation is known. The method continues with the optional step 445.

In the optional step 445 a second estimation for the pilot injection fuel mass is determined. The second estimation is based on the determined possible start of combustion of the injected pilot injection fuel. The second estimation is further based on an inversion of the second model. It should be understood that the possible start of combustion directly relates to the combustion delay. Since the second model provides a value for the combustion delay based on mpilot, an inversion of the second model provides a second estimation of mpilotwhen the start of combustion is known. The method continues with the optional step 450.

In the optional step 450 a vaporised mass of the pilot injection fuel is estimated. The estimation of the vaporised mass can be based on a pilot combustion model. In one example, the pilot combustion model describes transitions between different masses of the injected fuel. In one example, the different masses comprise the injected mass, the vaporised mass, a premixed mass and a burned mass. In one example, the model is normalised based on the total injected mass. The pilot combustion model can be a set of linear equations. In one example, the pilot combustion model is based on the heat release. The method continues with the optional step 455.

In the optional step 455 a combusted mass of the pilot injection fuel is estimated. The estimation of the vaporised mass can be based on a pilot combustion model. The pilot combustion model for estimating the combusted mass is preferably the same pilot combustion model as the pilot combustion model for estimating the vaporised mass. However, in principle even another pilot combustion model can be used for estimating the combusted mass. The method continues with the step 460.

In step 450 and/or step 455 other models might be used. Examples of other models have been described in relation to Fig. 3.

In the step 460 the pilot injection fuel mass is determined. This determination is based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion. In one example, the determination is indirectly based on the determined pressure. This can, for example, be the case if the determination of the possible start of vaporisation and/or the determination of the possible start of combustion is based on the determined pressure. In one example, the pilot injection fuel mass is determined directly based on the determined pressure.

In one example, the determination of the pilot injection fuel mass comprises an estimation method. In one example, the estimation method comprises applying a Kalman filter. In one example, the estimation method comprises applying an Extended Kalman Filter. The estimation method can comprise using neural networks and/or particle filter(s). The estimation method is preferably based at least on the first estimation of the fuel mass and/or the second estimation of the fuel mass as described above. In one example, the estimation method is based on the estimation for the estimated combusted mass of the pilot injection fuel. In one example the method is based on the estimated vaporised mass of the pilot injection fuel. In a preferred example, the estimation method is based on the first estimation, the second estimation, the estimated vaporised mass, and the estimated combusted mass. The method continues with the optional step 470.

In the optional step 470 it is determined whether the combustion has finished, i.e. whether the end of combustion, EOC, is achieved. In one example, it is determined that the EOC is achieved in case the estimation for the combusted mass has reached and/or passed a certain threshold value. The threshold value can be fraction of the total injected mass. In one example, it is determined that the EOC is achieved in case estimation for the combusted mass has reached 95 % of the total injected pilot injection fuel mass.

In one example, the method 400 ends after step 470. In one example, at least some of the method steps are performed iteratively. As an example, the steps 450 and/or 455 and/or 460 and/or 470 are performed iteratively. As an example, in case it is determined in step 470 that the EOC is not achieved, a new estimation for the vaporised mass and/or the combusted mass can be made. The determination of the pilot injection fuel mass can then be based on that/these new estimation(s). The determination of the pilot injection fuel mass in step 460 can further be based on any of the previous estimations. In one example, determining of the pilot injection fuel mass comprises iteratively performing estimations for the pilot injected fuel mass during different volumes in the combustion chamber and/or different orientations of a crank shaft connected to the combustion chamber. Usually, at least the estimations for the vaporised and/or combusted fuel masses will differ between these different estimations. In one example, the determined pilot injection fuel mass corresponds to the estimated pilot injection fuel mass when it is determined that the combustion in the combustion chamber during the pilot ends. This is, for example, the case if is determined in step 470 that the EOC is achieved.

The method 400 has been described above in a sequential way. It should, however, be understood that the steps of the methods equally well can be performed partly or fully in parallel. As an example, any of the estimations described above could be derived in parallel.

It should be emphasised that the first estimation, the second estimation, and results from the estimation(s) for the vaporised mass and/or the combusted mass in general do not coincide. There are, in general, deviations due to measurement uncertainties and/or due to limitations in the used model(s). Therefore, each estimation possesses, in general, a value for its confidence. In one example, all used estimations are combined so that the final estimation has a maximum confidence/minimum uncertainty. In one example, the value of confidence is a standard deviation. This can, for example, be the case if the estimations are modelled as being normally distributed. In one example, all used estimations are combined so that the final estimation has a minimum variance/minimum standard deviation. This might be applied in step 460.

Fig. 4b shows, in a schematic way, a flow chart over an example of a method 480 for controlling an injection to a combustion chamber of an engine. The method starts with the step 400. In step 400, a pilot injection fuel mass in the combustion chamber of the engine is determined in-cycle. This has been described in detail above. The method continues with the step 485.

In step 485 a later injection to the combustion chamber is controlled based on the determined pilot injection fuel mass. The later injection can relate to a later pilot injection to the combustion chamber. In one example, the controlling comprises adding and/or removing a later pilot injection. In one example, the controlling comprises shifting the time of a later pilot injection. The controlling can comprise increasing or decreasing the amount of fuel intended to be injected during a later pilot injection. The controlling can comprise adapting the time where a valve to/and or from the combustion chamber is opened during a later pilot injection. The term later pilot injection can relate to the subsequent pilot injection and/or to any other pilot injection at a later moment of time. In one example, the controlling is performed in case the determined pilot injection fuel mass is above and/or below a pre-determined threshold. The pre-determined threshold can be different for different control adjustments. As an example, an adjustment which changes the amount of fuel which is intended to be injected during a later pilot injection might be performed based on a different threshold than an adjustment relating to a change in time of a later pilot injection. However, the control adjustment does not necessarily need to be based on threshold. The control adjustment can additionally and/or alternatively be performed directly on the determined amount of pilot injection fuel.

What has been described above in relation to a later pilot injection can alternatively and/or additionally be applied to a later main injection and/or post injection into the combustion chamber. After step 485 the method 480 ends.

Fig. 4c shows, in a schematic way, a flow chart over an example of a method 490 for controlling an injection to a second combustion chamber of an engine. The method 490 starts with the step 400 of determining in-cycle a pilot injection fuel mass in a first combustion chamber of the engine. This has been described in more detail above. The method continues with step 495.

In step 495 an injection to a second combustion chamber is controled based on the determined pilot injection fuel mass of the first combustion chamber. The first and the second combustion chamber are different combustion chambers. As an example, the first combustion chamber is a first cylinder of an engine and the second combustion chamber is a second cylinder of the engine. The control of the injection to the second combustion chamber can comprise any of the controls/adaptions described above in step 485 in relation to controls/adaptions of injections to the same combustion chamber. After step 495 the method 490 ends.

The fuel of the later injection in step 485 and/or step 495 can be the same fuel as in the pilot injection or can be a fuel different from the fuel used during the pilot injection.

In the context of this disclosure, the term pilot injection relates to the fact that the pilot injection is prior to another injection. The other injection can be a main injection, another pilot injection, or a post injection. The term pilot injection itself can thus in one embodiment relate to a main injection and/or a post injection. In one example, the term pilot injection relates to an injection where the amount of fuel which is intended to be injected is lower than a certain fraction of the amount of fuel which is intended to be injected during a following injection. In one example, the fraction is 80 %, 50 %, or 30 %. The following injection can be an injection which follows directly after, or at a later moment.

Figure 5 is a diagram of one version of a device 500. The control units 200 and 205 described with reference to Figure 2 may in one version comprise the device 500. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

The computer program comprises routines for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine.

The computer program P may comprise routines for determining a pressure inside the combustion chamber. This may at least partly be performed by means of the first control unit 200 and or the pressure sensor 245. The computer program P may comprise routines for determining the possible start of vaporisation of the injected pilot fuel. The computer program P may comprise routines for determining the possible start of combustion of the injected pilot fuel.

The computer program P may comprise routines for determining the pilot injection fuel mass based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion. This may at least partly be performed by means of said first control unit 200. The computer program P may comprise routines for performing an estimation method when determining the pilot injection fuel mass. This estimation method might comprise any of the estimation methods described above in relation to Fig. 4.

The computer program P may comprise routines for controlling the injector 250 and/or any other injector based on the determined fuel mass of the pilot injection.

The program P may be stored in an executable form or in compressed form in a memory 560 and/or in a read/write memory 550.

Where it is stated that the data processing unit 510 performs a certain function, it means that it conducts a certain part of the program which is stored in the memory 560 or a certain part of the program which is stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit via a data bus 511. The read/write memory 550 is arranged to communicate with the data processing unit 510 via a data bus 514. The links L205, L235, L245, L250, L261, L262 and L270, for example, may be connected to the data port 599 (see Figure 2).

When data are received on the data port 599, they can be stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 can be prepared to conduct code execution as described above.

Parts of the methods herein described may be conducted by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, methods herein described are executed.

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is neither intended to be exhaustive, nor to limit the invention to the variants described. Many modifications and variations will obviously suggest themselves to one skilled in the art. The embodiments have been chosen and described in order to best explain the principles of the invention and their practical applications and thereby make it possible for one skilled in the art to understand the invention for different embodiments and with the various modifications appropriate to the intended use.

It should especially be noted that the system according to the present disclosure can be arranged to perform any of the steps or actions described in relation to any of the methods 400, 480, and/or 490. It should also be understood that any of the methods according to the present disclosure can further comprise any of the actions attributed to an element of the system 299 described in relation to Fig. 2. The same applies to the computer program product and the computer-readable storage medium.

List of references: 200 First control unit 205 Second control unit 210 Engine 220 Fuel tank 230 Crank shaft 231 Piston arrangement 235 Crank angle degree sensor 240 First cylinder 241 Second cylinder 245 Pressure sensor 250 Fuel injector 260 Fuel ray 261 Pressure sensor 262 Temperature sensor 270 Temperature sensor

Claims

1. A method (400) for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine, the method comprising the steps of: - determining (420) a pressure inside the combustion chamber; - determining (430) the possible start of vaporisation of the injected pilot fuel; - determining (435) the possible start of combustion of the injected pilot fuel; - determining (460) the pilot injection fuel mass based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion.

2. The method according to the previous claim, wherein said pressure inside the combustion chamber is determined based on a measurement of a pressure sensor in the combustion chamber.

3. The method according to anyone of the previous claims, further comprising the steps of: - providing (410) a first model for determining the vaporisation delay of the injected pilot injection fuel, wherein said first model is based on an estimated pilot injection fuel mass; and - determining (440) a first estimation for the pilot injection fuel mass based on the determined possible start of vaporisation of the injected pilot injection fuel and based on an inversion of the first model.

4. The method according to anyone of the previous claims, further comprising the steps of: - providing (411) a second model for determining the combustion delay of the injected pilot injection fuel, wherein said second model is based on an estimated pilot injection fuel mass; and - determining (445) a second estimation for the pilot injection fuel mass based on the determined possible start of combustion of the injected pilot injection fuel and based on an inversion of the second model.

5. The method according to anyone of the previous claims, wherein said determining of the pilot injection fuel mass comprises an estimating method, such as, for example, applying a Kalman filter, Extended Kalman Filter, neural networks, particle filter.

6. The method according to anyone of the previous claims, wherein said determining of the pilot injection fuel mass comprises iteratively performing estimations for the pilot injection fuel mass during different volumes in the combustion chamber and/or different orientations of a crank shaft connected to the combustion chamber, and wherein the determined pilot injection fuel mass corresponds to the estimated pilot injection fuel mass when it is determined that the combustion in the combustion chamber during the pilot ends.

7. The method according to anyone of the previous claim, further comprising the steps of: - estimating (450) a vaporised mass of the pilot injection fuel; and/or - estimating (455) a combusted mass of the pilot injection fuel; and - determining (460) the pilot injection fuel mass based on the estimated vaporised and/or combusted mass of the pilot injection fuel.

8. A method (480) for controlling an injection to a combustion chamber of an engine, the method comprising the steps: - determining (400) in-cycle a pilot injection fuel mass in the combustion chamber of the engine according to anyone of the previous claims; - controlling (485) a later injection to the combustion chamber based on the determined pilot injection fuel mass.

9. A method (490) for controlling an injection to a second combustion chamber of an engine, the method comprising the steps: - determining (400) in-cycle a pilot injection fuel mass in a first combustion chamber of the engine according to anyone of claims 1-7; - controlling (495) an injection to a second combustion chamber based on the determined pilot injection fuel mass of the first combustion chamber, wherein the first and the second combustion chamber are different combustion chambers.

10. A system (299) for determining in-cycle a pilot injection fuel mass in a combustion chamber of an engine (210), the system comprising: - means (200, 205, 245) for determining a pressure inside the combustion chamber; - means (200, 205) for determining the possible start of vaporisation of the injected pilot fuel; - means (200, 205) for determining the possible start of combustion of the injected pilot fuel; - means (200, 205) for determining the pilot injection fuel mass based on the determined pressure, the determined possible start of vaporisation, and the determined possible start of combustion.

11. The system according to the previous claim, wherein said means (200, 205, 245) for determining a pressure inside the combustion chamber comprise a pressure sensor (245) in the combustion chamber.

12. The system according to anyone of claims 10-11, wherein the means for determining the possible start of vaporisation of the injected pilot fuel and/or the means for determining the possible start of combustion of the injected pilot fuel and/or the means for determining the pilot injection fuel mass comprise a field programmable gate array. FPGA.

13. A vehicle (100), comprising the system according to anyone of claims 10-12.

14. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to anyone of claims 1-9.

15. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to anyone of claims 1-9.