EP3371440A1

EP3371440A1 - Internal combustion engine with injection quantity control

Info

Publication number: EP3371440A1
Application number: EP16798618.1A
Authority: EP
Inventors: Medy Satria; Dino Imhof; Raphael Burgmair
Original assignee: GE Jenbacher GmbH and Co OHG
Current assignee: Innio Jenbacher GmbH and Co OG
Priority date: 2015-11-04
Filing date: 2016-11-03
Publication date: 2018-09-12
Also published as: US11035309B2; CN108350821A; CA3002559A1; US20180363581A1; EP3165749A1; WO2017075642A1

Abstract

The invention relates to a dual-fuel internal combustion engine comprising: a regulating device; at least one combustion chamber; at least one gas supply device for supplying a gaseous fuel to the at least one combustion chamber; and at least one injector for injecting liquid fuel into the at least one combustion chamber, which can be regulated by the regulating device by means of an actuator control signal, the regulating device regulating an opening of the needle of the injector in the ballistic region of the needle, in a pilot operating mode of the internal combustion engine, by means of the actuator control signal. An algorithm is provided in the regulating device, which receives at least the actuator control signal (Δt) as an input variable and calculates a position of the needle (6) by means of an injector model, compares said position with a needle position set point value (z^ref), and corrects the actuator control signal (Δt) according to the result of the comparison. The invention also relates to a method for operating such an internal combustion engine and to an injector of such an internal combustion engine.

Description

INTERNAL COMBUSTION ENGINE WITH INJECTION CONTROL

The present invention relates to a dual-fuel internal combustion engine having the features of the preamble of claim 1 and a method having the features of the preamble of claim 10 or 1 1.

Dual-fuel internal combustion engines are typically operated in two modes of operation. A distinction is made between a mode of operation with primarily liquid fuel supply ("liquid operation" for short, "diesel operation" in the case of using diesel as a liquid fuel) and a mode of operation with primary gaseous fuel supply in which the liquid fuel serves as a pilot fuel for initiating combustion ( "Gas operation", also referred to as "pilot operation" or "pilot jet operation".) As an example of the liquid fuel is called diesel.It could also be heavy fuel oil or another auto-ignitable fuel.As an example of the gaseous fuel is called natural gas there are other gaseous fuels like biogas etc.

In pilot operation, a small amount of liquid fuel is introduced as so-called pilot injection in a combustion chamber of a piston-cylinder unit. The conditions prevailing at the time of injection ignite the introduced liquid fuel and ignite a mixture of gaseous fuel and air present in the combustion chamber of the piston-cylinder unit. The amount of liquid fuel of a pilot injection is typically 0.5-5% of the total amount of energy supplied to the combustion chamber of the piston-cylinder unit in one operating cycle of the internal combustion engine.

To clarify the definition, it is defined that the internal combustion engine is operated either in pilot operation or in liquid operation. Regarding the controller, the pilot mode of the internal combustion engine is referred to as a pilot mode, a liquid mode of the internal combustion engine is referred to as a liquid mode with respect to the controller.

By a ballistic region is meant an operation of the liquid fuel injector wherein the needle extends from a "full-closed" position moves to a "full-open" position but does not reach it, as a result, the needle moves back toward the "full-close" position without reaching the "full-open" position Substitution rates indicate what proportion of the energy supplied to the internal combustion engine is supplied in the form of the gaseous fuel., Substitution rates between 98 and 99.5% are sought. Such high substitution rates require a design of the internal combustion engine, for example with regard to the compression ratio which corresponds to that of a gas engine partially conflicting requirements for the internal combustion engine for a pilot operation and a liquid operation lead to compromises in the design, for example in terms of the compression ratio.

A problem in the prior art is that over the life of a liquid fuel injector exact control of the needle position in the ballistic area using a single injector with only one needle is not possible. In this area, due to statistical variations, manufacturing variability, wear, etc., the actuation of the needle-opening actuator does not unambiguously map to the mass of injected liquid fuel.

Thus, instead of using only a single-needle injector operable in both a pilot mode and an increased liquid fuel mode of operation, either two separate injectors or an injector with two separate needles are employed. It is also known to limit the substitution rate upwards.

WO 2014/202202 A1 describes an injector for a generic internal combustion engine, in which by means of a pressure sensor arranged in the injector the pressure drop in a storage chamber is measured and from this the actual injection duration is determined. For very small amounts, however, the pressure drop is too low to produce a sufficiently accurate correlation with the duration of injection The object of the invention is to provide a dual-fuel internal combustion engine and a method in which an exact control of the needle position in the ballistic range is possible. This object is achieved by an internal combustion engine having the features of claim 1 and a method having the features of claims 10 and 11, respectively. Advantageous embodiments of the invention are defined in the dependent claims.

Characterized in that in the control device, an algorithm is stored, which receives at least the Aktuatoransteuersignal as inputs and calculated via an injector model, the needle position and comparing the calculated using the injector model needle position with a desired needle position setpoint and depending on the result of the comparison leaves the Aktuatoransteuersignal same or corrected , it is possible to precisely control the needle in the ballistic area. As a result, the exact injection of very small amounts of liquid fuel using only one injector with only one needle is possible, the substitution rate does not have to be limited to the top. One and the same injector can be operated in a range of 0% substitution rate up to a selected upper limit (eg 99.5%) of the substitution rate. It is therefore possible with the same injector with only one needle operating in liquid mode, in pilot mode or a mixed operation.

The control device is particularly preferably designed to execute the algorithm during each combustion cycle or selected combustion cycles of the internal combustion engine and to correct the actuator drive signal during deviations during this combustion cycle in case of deviations.

The algorithm estimates a needle position based on the actuator drive signal. The invention then starts from the needle position calculated by the algorithm and compares this value with the desired needle position setpoint. In case of deviations can be corrected immediately (eg within 10 milliseconds).

Preferably, at least one sensor is provided, by which at least one measured variable of the at least one injector can be measured, wherein the sensor Signal connection with the control device is or can be brought. In this case, the algorithm may calculate the needle position taking into account the at least one measurand via the injector model. Of course, it is also possible to use a plurality of measured variables for estimating the applied mass of liquid fuel.

Preferably, the algorithm has a feedforward control which calculates from the desired needle position setpoint a pilot command (also referred to as a "pilot control signal") for the actuator drive signal The feedforward ensures a fast system response since it drives the injector as if there were no injector variability exist.

In an embodiment of the control device with pilot control, it can be particularly preferred that the algorithm has a feedback loop which, taking into account the pilot command for the needle position calculated by the precontrol and the at least one measured variable, calculates the needle position by means of the injector model and if necessary (in the presence of a Deviation) corrects the needle position setpoint calculated by the precontrol. The feedback loop is used to correct the inaccuracies of feedforward (due to manufacturing variability, wear, etc.) causing injector drift.

The algorithm preferably has an observer, who, using the injector model, estimates the needle position as a function of the at least one measured variable and the at least one actuator drive signal. Actual needle position measurement is therefore not required for the feedback loop. Regardless of whether a feedback loop is provided, the observer estimated needle position in the feedforward control can be used to enhance the actuator drive signal.

Various possible embodiments of the observer are known to the person skilled in the literature (eg Luenberger observers, Kalman filters, "Sliding Mode" observers, etc.). The observer can also serve to take into account, with the aid of the injector model, the state of the injector that changes over the life of the injector (eg due to aging or wear) for an improvement of the pilot signal and / or of the actuator drive signal.

Basically, it is possible to calculate the actuator drive signal based on the needle position setpoint and based on the estimated needle position by the observer. This gives an adaptive, modified by the observer pilot signal. In this case, the control is therefore not constructed in two parts, with a feedforward control and a feedback control loop which corrects the precontrol signal.

It can be provided that the injector model at least includes:

the pressure courses in the volumes of the injector filled with the liquid fuel - mass flow rates between the volumes of the injector filled with the liquid fuel

Dynamics of the actuator of the needle, preferably dynamics of a solenoid valve

The injector may have at least:

- An associated with a common rail of the internal combustion engine input storage chamber

a liquid fuel storage chamber connected to the input storage chamber

- A volume connected to the storage chamber via needle seat

- An on the one hand with the storage chamber and on the other hand connected to a drain line connection volume

- A closed by a needle and connected to the volume via needle seat associated discharge opening for liquid fuel

- An activatable by means of Aktuatoransteuersignals actuator, preferably solenoid valve, for opening the needle

- Preferably, on the one hand with the storage chamber and on the other hand connected to the connecting volume control chamber The needle is usually biased against the opening direction by a spring.

It can also be provided an injector, which manages without control chamber, for example an injector, in which the needle is driven by a piezoelectric element.

The at least one measurand may be e.g. be selected from the following sizes or a combination thereof:

- Pressure in a common rail of the internal combustion engine

- Pressure in an input storage chamber of the injector

- Pressure in a control chamber of the injector

The invention may preferably be used in a stationary internal combustion engine, for marine applications or mobile applications such as so-called "Non-Road Mobile Machinery" (NRMM), preferably in each case as a reciprocating piston engine The internal combustion engine preferably has a multiplicity of combustion chambers with corresponding gas supply devices and injectors The regulation can be carried out individually for each combustion chamber, for example for the operation of compressor systems or with a generator.

Embodiments of the invention will be explained with reference to FIGS. Show it:

Fig. 1 shows a first embodiment of the control scheme according to the invention

Fig. 2 shows a second embodiment of the control scheme according to the invention

3 shows a first example of a schematically illustrated injector

4 shows a second example of a schematically illustrated injector

Fig. 1: The aim of the injector control is in this embodiment, the regulation of the position z of the needle 6 of the injector also for the ballistic range to a needle position setpoint out by the duration At the actuation of an actuator of the

Needle during an injection process for the liquid fuel, so to speak in real time is regulated. The rule strategy is done by

- A feedforward control (FF), which from a desired needle position setpoint, a pilot signal (hereinafter also referred to as "control command") for the

Duration At the actuation of the actuator the needle is calculated and

a feedback loop (FB), which is calculated using an observer 7 ("State Estimator"), taking into account the precontrol calculated by

Control command for the duration At the actuation of the actuator of the needle and at least one measured variable y (eg one of the occurring in the injector pressure gradients PIA, PCC, PJC, PAC, PSA or the beginning of lifting the needle from the needle seat) by means of an injector model Estimate the position z of the needle and, if necessary, correct the setpoint value Δt _ff calculated by the pre-control for the injection duration by means of a correction value Δt _fb to the actual duration of the actuator drive signal At for the needle.

The pilot control ensures a fast system response, since it drives the actuator of the needle 6 with a duration Δt _ff , as if there were no injector variability. The feedforward controller uses a calibrated injector map (which indicates energization duration via injection mass or volume) or the inverted injector model to convert the needle position command value z ^ref to the pilot command for the duration At of the actuation of the actuator of the needle.

The feedback loop (FB) is used to correct the inaccuracies of feedforward (due to manufacturing variability, wear, etc.) that cause injector drift. The feedback loop compares the needle position setpoint z ^ref with the estimated position of the needle and outputs as feedback a correction control command Δt _ff (which may be negative) for the duration of actuation of the actuator of the needle if there is a discrepancy between z ^ref and z. The addition of Δt _ff and Δt _fb gives the final duration Δt of the actuation of the actuator of the needle. The observer estimates the position of the needle z as a function of at least one measured variable y and the final duration Δt of the actuation of the actuator of the needle 6. The at least one measured variable can relate, for example, to: common rail pressure p _CR , pressure in the input storage chamber p _IA , pressure in the control chamber p _cc and start of lifting the needle from the needle seat. The observer uses a reduced injector model to estimate the position z of the needle 6.

Fig. 2:

This figure shows a one-piece constructed control in which the Aktuatoransteuersignal At is calculated on the basis of the needle position setpoint z ^ref and on the basis of the observer estimated, used in the pilot model parameter .DELTA.mod _mod .. This gives an adaptive, modified by the observer pilot signal. In this case, the control is therefore not constructed in two parts, with a feedforward control and a feedback control loop which corrects the precontrol signal.

3 shows a block diagram of a reduced injector model. The injector model consists of a structural model of the injector and a system of equations describing the dynamic behavior of the structural model. The structural model consists of five modeled volumes: input storage chamber 1, storage chamber 3, control chamber 2, volume via needle seat 4 and connection volume 5.

The storage chamber 1 represents the summary of all volumes from the check valve to the volume 4 above the needle seat. The volume 4 above the needle seat represents the summary of all volumes between the needle seat to the The connection volume 5 represents the summary of all volumes, which connects the volumes of the storage chamber 3 and the control chamber 2 with the solenoid valve. FIG. 4 shows an alternatively designed injector which does not require a control chamber 2, for example an injector, in which the needle is actuated by a piezo element. The following equation system does not relate to the embodiment shown in FIG. The formulation of a corresponding equation system can be carried out analogously to the equation system shown below.

The dynamic behavior of the structure model is described by the following equation systems:

pressure dynamics

The time evolution of the pressure within each of the volumes is calculated based on a combination of the mass conservation rate and the pressure-density characteristic of the liquid fuel. The temporal evolution of the pressure results from:

Used formula symbols

Pressure in the input storage chamber 1 in bar

Pressure in the control chamber 2 in bar

Pressure in the connection volume 5 in bar

Pressure in the storage chamber 3 in bar

Pressure in the small storage chamber 4 in bar

Diesel mass density within the input storage chamber

1 in kg / m ³

Diesel mass density inside the control chamber 2 in kg / m ³ Diesel mass density within the connection volume 5

in kg / m ³

Diesel mass density within the storage chamber 3 in kg / m ³

Diesel mass density within the small storage chamber 4

in kg / m ³

Compression module of the diesel fuel in bar

needle dynamics

The needle position is calculated using the following equation of motion:

Used formula characters:

Needle position in meters (m)

Maximum deflection of the needle 6 in m

Spring stiffness in N / m

Spring damping coefficient in N.s / m

Spring preload in N

Hydraulic effective area in the storage chamber 3 in m ² Hydraulic effective area in the small storage chamber 4 in m ²

Hydraulic effective area in the control chamber 2 in m ²

Dynamics of the solenoid valve

The solenoid valve is modeled by a first order transfer function that converts the valve opening command to a valve position. This is given by:

The transient system behavior is determined by the time constant characterized and the position of the needle 6 at the maximum valve opening is given by. Instead of

A solenoid valve also allows piezoelectric actuation.

Mass flow rates

The mass flow rate through each valve is calculated from the standard throttling equation for liquids, which reads:

Used formula characters:

Mass flux density via the input choke in kg / s

Mass flow rate via the bypass valve between

Storage chamber 3 and connection volume 5 in kg / s

Mass flow rate via the feed valve at the inlet of the

Control chamber 2 in kg / s

Mass flow rate via the outlet valve of the control chamber 2 in kg / s

Mass flow rate via the solenoid valve in kg / s

Mass flow rate over the inlet of the storage chamber 3 in kg / s

Mass flow rate over the needle seat in kg / s

Mass flow rate via the injector nozzle in kg / s

On the basis of the injector model formulated above, the person skilled in the art obtains by means of the observer in a manner known per se (see, for example, Isermann, Rolf, "Digital Control Systems", Springer Verlag Heidelberg 1977, Chapter 22.3.2, page 379 ff., Or F. Castillo et al., "Simultaneous Air Fraction and Low-Pressure EGR Mass Flow Rate Estimation for Diesel Engines", IFAC Joint Conference SSSC - 5th Symposium on System Structure and Control, Grenoble, France 2013) estimates the estimated position of the needle z.

Using the above systems of equations one constructs the so-called observer equations, preferably using a per se known observer of the "sliding mode observer" type, by adding to the equations of the injector model the so-called observer law In a "sliding mode" observer, one obtains the observer law by calculating a hypersurface from the at least one measurement signal and the value resulting from the observer equations by squaring the hypersurface equation to obtain a generalized Ljapunov equation (generalized The observer law is that function which minimizes the functional equation, which can be determined by the well-known variation techniques or numerically, which is done within a combustion cycle for each time step (depending on the time resolution of the regulation).

The result, depending on the application, is the estimated injected mass of liquid fuel, the position of the needle 6, or one of the pressures in a volume of the injector.

Claims

claims

1 . Dual fuel internal combustion engine, with:

- a control device

- at least one combustion chamber

- At least one Gaszuführvorrichtung for supplying a gaseous fuel to the at least one combustion chamber and

at least one injector for injecting liquid fuel into the at least one combustion chamber controllable by the control device via an actuator drive signal, the at least one injector having a liquid fuel discharge opening closable by a needle (6), and wherein the control device is in a pilot operating mode Internal combustion engine via the Aktuatoransteuersignal an opening of the needle in the ballistic range of the needle regulates

characterized in that in the control device, an algorithm is stored, which receives at least the Aktuatoransteuersignal as input variables and calculates a position of the needle (6) via an injector model

and the position of the needle calculated by the injector model with a needle position setpoint compares and, depending on the result of the comparison, the actuator drive signal equal to or corrected.

2. Dual-fuel internal combustion engine according to claim 1, wherein the algorithm comprises a feedforward control (FF), which from the needle position setpoint a

Pre-control signal for the Aktuatoransteuersignal calculated.

3. dual-fuel internal combustion engine according to at least one of the preceding claims, wherein at least one sensor is provided, through which at least one measured variable (y) of the at least one injector is measurable, wherein the sensor is in signal communication with the control device or can be brought.

4. Dual-fuel internal combustion engine according to claim 3, wherein the algorithm is a feedback loop (FB), which taking into account of the Precontrol calculated control command (.DELTA.t) for the position of the needle (6) and the at least one measured variable (y) by means of the injector model calculates the needle position and possibly corrects the Aktuatoransteuersignal (.DELTA.t) calculated by the pilot control.

5. Dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the algorithm comprises an observer, which estimates the needle position (z) using the injector model and taking into account the Aktuatoransteuersignals (.DELTA.t) and the at least one measured variable (y).

6. Dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the injector model at least includes:

- The pressure curves in filled with the liquid fuel

Volumes of the injector

- Mass flow rates between the volumes of the injector filled with the liquid fuel

Dynamics of the actuator of the needle, preferably dynamics of a solenoid valve

7. Dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the injector comprises at least:

- An input storage chamber (1) connected to a common rail of the internal combustion engine

- A liquid fuel storage chamber (3) connected to the input storage chamber (1)

- One connected to the storage chamber (3) volume (4) via needle seat

a connecting volume (5) connected on the one hand to the storage chamber (3) and on the other hand to a discharge line

- A closed by the needle (6) and with the volume (4) via needle seat associated discharge opening for liquid fuel

an actuator which can be actuated by means of the actuator drive signal, preferably a solenoid valve, for opening the needle (6) preferably a control chamber (2) connected on the one hand to the storage chamber (3) and on the other hand to the connecting volume (5)

8. Dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the at least one measured variable is selected from the following variables or a combination thereof:

- Pressure in a common rail of the internal combustion engine

- Pressure in an input storage chamber (1) of the injector

- Pressure in a control chamber (2) of the injector

- Beginning of lifting the needle (6) from the needle seat

9. A dual-fuel internal combustion engine according to at least one of the preceding claims, wherein the control device is adapted to execute the algorithm during each combustion cycle or selected combustion cycles of the internal combustion engine and to correct the Aktuatoransteuersignal (At) during this combustion cycle in case of deviations.

10. A method for operating a dual-fuel internal combustion engine, in particular a dual-fuel internal combustion engine according to at least one of the preceding claims, wherein a combustion chamber of the internal combustion engine liquid fuel is supplied, characterized in that a needle position of a needle of an injector for the liquid fuel is calculated in response to an actuator drive signal (At) of an actuator of the liquid fuel injector using an injector model, and the actuator drive signal (At) is corrected in case of deviations between a needle position command value and the calculated position;

Method is performed during each combustion cycle or selected combustion cycles of the internal combustion engine and a possible correction of the Aktuatoransteuersignals (.DELTA.t) takes place during this combustion cycle.

1 1. Method for operating an injector, with which injector liquid fuel can be supplied to a combustion chamber of an internal combustion engine, characterized characterized in that a needle position of a needle of a liquid fuel injector is calculated in response to an actuator drive signal (Δt) of an actuator of the liquid fuel injector using an injector model and the actuator drive signal (Δt) in case of deviations between a needle position target value (/ ^ef ) and the calculated position is corrected.