DE102010045593A1 - System for detecting type of e.g. compressed natural gas utilized for operating dual-fuel engine of motor car, has sensor unit designed so as to detect type of fuel located in suction tube from measured parameter during operation - Google Patents

Abstract

The system (4) has a sensor unit (26) for measuring a parameter that characterizes a type of different gaseous fuels, which are burnt in a cylinder (12) to operate a combustion engine (2). The sensor unit is designed in such a manner that the type of the fuel located in a suction tube (18) is detected from the measured parameter during operation. The sensor unit comprises a first sensor for measuring air-mass flow in the suction tube, a second sensor (28) for measuring a lambda value, and third- and fourth sensors for measuring fuel injector pressure and tube pressure, respectively. Independent claims are also included for the following: (1) a system for controlling a combustion engine (2) a method for detecting a type of gaseous fuel (3) a computer program comprising a set of instructions for executing a method for detecting a type of gaseous fuel.

Description

The present application relates to a system and method for detecting the nature of a gaseous fuel, a system and method for controlling an internal combustion engine, in particular an internal combustion engine, which can be operated with two different gaseous fuels, as well as an internal combustion engine and a motor vehicle.

An internal combustion engine according to the Otto principle is in the DE 103 18 963 A1 disclosed. This internal combustion engine can be operated with two different knock-resistant fuels, such as gasoline and natural gas. Gasoline is used as a reserve fuel, so that the engine can also be operated when the main fuel, ie natural gas, is used up or not. Such internal combustion engines are also called multi-fuel engines.

In an engine according to the Otto principle, an air-fuel mixture in a combustion chamber, such as a cylinder, is compressed and then ignited with a spark plug. However, compression can lead to spontaneous ignition, which is undesirable because it can damage the engine.

Different fuels typically have different knock strengths, i. H. their mixture with air can be compressed to different degrees before it comes to unwanted spontaneous inflammation and tapping.

In order to make the most of the fuel, however, it is desirable to compress it as much as possible prior to the externally induced ignition. This is achieved by the design of the engine so that typically one engine can be optimally designed and adjusted for only one fuel. If this engine is operated with a different fuel, knocking may occur, which may damage the engine.

In order to reliably use an engine with different fuels of different knock resistance, is in the DE 103 18 963 A1 the fuel metering system is adjusted depending on the fuel type. Consequently, the engine can be operated not only with natural gas but also with gasoline, although the efficiency in gasoline operation is lower than in natural gas operation.

However, other internal combustion engines and systems and methods for driving an internal combustion engine with different fuels are desirable to further increase the efficiency of the engine.

In one embodiment, a system for detecting the type of gaseous fuel is provided. The gaseous fuel is used for operating an internal combustion engine with a suction pipe and at least one cylinder. For operating the internal combustion engine, at least two different gaseous fuels can be burned in the cylinder. The system includes sensor means for measuring at least one parameter indicative of the nature of the gaseous fuel. The sensor means is designed such that during operation of the internal combustion engine, the type of gaseous fuel which is located in the intake manifold is detected from the measured parameter.

This system allows the engine to operate on different gaseous fuels without the type of fuel being previously known to the system. The type of fuel that is in the intake manifold and is fed into the cylinder or into the cylinder is detected by direct measurement on the internal combustion engine. This has the advantage that another fuel can be used to operate the engine, for example, if the conventional fuel is not present, without the control system of the internal combustion engine and / or the internal combustion engine itself must be manually adjusted to the new fuel.

The mixture to be identified of the different gaseous fuels is initially in the fuel supply to the engine, which may be, for example, an injector rail. After the injection in the intake manifold, air is also present.

The sensor means may include one or more sensors that measure parameters of parameters that characterize the fuels. Consequently, from these parameters or from the measured values of these parameters, the type of fuel and optionally the mixing ratio of two different gaseous fuels can be determined.

In one exemplary embodiment, the sensor means comprises a first sensor for measuring the air mass flow in a suction tube of the cylinder and / or a second sensor for measuring λ and / or a third sensor for measuring the fuel injector pressure and / or a fourth sensor for measuring the intake manifold pressure and / or or a fifth sensor for measuring a temperature of the fuel. λ is the lambda value of a fuel-air mixture. In one embodiment, all five sensors are provided and the type of fuel is determined from the five measured values of these parameters.

The system includes means for detecting an identification value indicative of the fuels. In one exemplary embodiment, the identification value is determined from the measured values of the air mass flow in a suction pipe of the cylinder and / or λ and / or the fuel injector pressure and / or the intake manifold pressure and / or the temperature. This means for detecting the identification value of the fuel type may be a microprocessor or a program that is performed by the existing engine control unit.

des gasförmigen Kraftstoffs sein, wobei F(T, G) ein temperaturabhängiger Identifikationswert der gasförmigen Kraftstoffzusammensetzung, m ._L Luftmassenstrom, C eine geometrieabhängige Konstante der Kraftstoffführung, λ der Lamdba-Wert eines Brennstoff-Luft-Gemisches und Δp die Differenz eines Kraftstoffinjektordrucks und eines Saugrohrdrucks ist.The identification value can be the density, the viscosity or the ratio

gaseous fuel, where F (T, G) is a temperature-dependent identification value of the gaseous fuel composition, m. _L Air mass flow, C is a geometry-dependent constant of the fuel guide, λ is the Lamdba value of a fuel-air mixture and Δp is the difference of a fuel injector pressure and a Saugrohrdrucks.

The means for detecting the identification value comprises in one embodiment previously known identification values of various gaseous fuels and means for comparing the detected identification value with the previously known identification values to determine the type of fuel in the intake manifold.

These previously known identification values can be stored in the form of a table or database in the memory of the engine control unit. The comparison of the determined identification value with the previously known identification values can be carried out, for example, by the means for detecting the identification value or by the engine control unit.

A system for controlling an internal combustion engine is also indicated. The internal combustion engine has an intake manifold and at least one cylinder, wherein at least two different gaseous fuels in the cylinder can be burned to operate the internal combustion engine. The system for controlling the internal combustion engine comprises a system for detecting the type of gaseous fuel according to one of the preceding embodiments and means for controlling the combustion of the gaseous fuel in the cylinder. The means for controlling the combustion is designed such that during the operation of the internal combustion engine, the combustion is regulated depending on the detected type of fuel.

Consequently, an engine equipped with this system can be operated not only with different gaseous fuels sequentially, but also with any mixture of two or more gaseous fuels because not only the kind but also the mixing ratio of the fuels directly before its entry into the cylinder can be detected. After the type or mixture of the gaseous fuel, which is located in the intake manifold, is determined, the combustion is controlled accordingly. Consequently, the engine and in particular the combustion in the cylinder during operation can be continuously controlled and optimized in order to increase the efficiency of the engine and avoid knocking.

The means for controlling the combustion may include means for adjusting the ignition timing and / or means for adjusting the fuel injector pressure and / or means for adjusting the duration of the fuel injection. The fuel-air mixture can also be adjusted by adjusting the amount of air.

An internal combustion engine with an intake manifold and at least one cylinder is also indicated, wherein at least two different gaseous fuels in the cylinder can be burned for operating the internal combustion engine. The internal combustion engine has a system according to one of the preceding embodiments.

This internal combustion engine may be run on a fuel other than a previous fuel that has been operating the engine. Alternatively, a mixture of two different gaseous fuels, such as LPG (Liquified Petroleum Gas) and CNG (Compressed Natural Gas) can be used. Each gaseous fuel can be stored in a separate tank.

These two different fuels can be injected through different fuel injectors into the intake manifold or directly into the cylinder. In one embodiment, however, the engine has a fuel supply line to the cylinder, which is designed such that two different gaseous fuels with a single fuel injector in the intake manifold can be injected. The two different gaseous fuels are mixed together before this mixture is injected into the intake manifold. This has the advantage that fewer fuel injectors are needed, so that the construction is simplified.

In another embodiment, in addition to the two different gaseous fuels, the engine may also be operated with a liquid fuel, such as gasoline. The liquid fuel can be stored in a separate tank and injected via a separate feed into the intake manifold or into the cylinder. Thus, in one embodiment, the internal combustion engine further includes another fuel injector for selectively injecting a liquid fuel into the cylinder or in an intake manifold of the cylinder.

The internal combustion engine can be based on the Otto principle. In this case, each cylinder has a spark plug with which the fuel-air mixture is ignited in the cylinder. In a further embodiment, the internal combustion engine is a diesel engine, wherein a Zündstrahlverfahren can be used. In the Zündstrahlverfahren a small pilot injection is used by means of a suitable diesel fuel for auto-ignition to tear the further cylinder filling of a variable fuel gas-air mixture with the combustion. With this method, when using high-compression-ratio fuels such as natural gas, for example, cylinder pressures and temperatures can be reduced as compared to a pure diesel method.

The application also provides a motor vehicle with an internal combustion engine with an intake manifold and at least one cylinder, wherein at least two different gaseous fuels can be burned in the cylinder to operate the internal combustion engine. The motor vehicle has a system according to one of the preceding embodiments, with which the type of gaseous fuel detected and optionally the combustion can be controlled.

This motor vehicle may have a plurality of tanks for storing the various fuels, wherein the number of the desired number of fuels may correspond. For example, the engine has two gaseous fuel tanks and a liquid fuel tank when the motor vehicle is operated with two different gaseous fuels, such as PLG, CNG, and gasoline.

The application also provides a method of detecting the type of gaseous fuel used to operate an internal combustion engine having an intake manifold and at least one cylinder, wherein at least two different gaseous fuels can be burned in the cylinder. During operation of the internal combustion engine, the type of gaseous fuel that is in the intake manifold is detected directly by measuring.

This method not only makes it possible to directly detect the type of fuel that is in the intake manifold and which is supplied to the cylinder, but also to adjust the operation of the engine and in particular the combustion of the fuel according to the detected fuel and thereby optimize. This can take place without the type of fuel being previously known to the system, in particular the engine control system, since this is measured and determined directly at the internal combustion engine and in particular from the fuel in the intake manifold.

For detecting the type of fuel, the mass air flow in a suction pipe of the cylinder and / or λ, the lambda value, and / or the fuel injector pressure and / or the intake pipe pressure and / or the temperature of the fuel can be measured. In one embodiment, the combination of air mass flow, λ, fuel injector pressure, manifold pressure, and temperature are measured, and these values are then used to determine the type of fuel.

festgestellt werden. F(T, G) ist ein temperaturabhängiger Identifikationswert der gasförmigen Kraftstoffzusammensetzung, m .L Luftmassenstrom, C eine geometrieabhängige Konstante der Kraftstoffführung, λ der Lamdba-Wert eines Brennstoff-Luft-Gemisches und Δp die Differenz eines Kraftstoffinjektordrucks und eines Saugrohrdrucks.The type of fuel can be determined with an identification value that identifies the fuel type. In one embodiment, the identification value is measured values of the Air mass flow, λ, the fuel injector pressure, the intake manifold pressure, and / or the temperature detected. The identification value may be the density or the viscosity of the fuel or by the ratio

be determined. F (T, G) is a temperature-dependent identification value of the gaseous fuel composition, m .L Air mass flow, C is a geometry-dependent constant of the fuel guide, λ the Lamdba value of a fuel-air mixture and Δp the difference of a fuel injector pressure and an intake manifold pressure.

The values of these parameters can be determined with suitable sensors and the calculation of the identification value and its comparison with known identification values of known possible fuels can be carried out with a microprocessor, for example with that of the engine control unit.

A method for controlling an internal combustion engine with an intake manifold and at least one cylinder is specified, wherein at least two different gaseous fuels can be burned for operating the internal combustion engine. During operation of the internal combustion engine, the type of gaseous fuel is detected by a method according to any one of the preceding embodiments, and thereafter, the combustion of the gaseous fuel in the cylinder is controlled depending on the detected type of the fuel.

After detecting the type of fuel, the combustion in the cylinder is controlled, so that the combustion of this fuel runs better. This can improve the efficiency of the engine and prevent knocking to avoid damaging the engine. The combustion may be regulated by adjusting the ignition timing and / or the fuel injector pressure, and / or the duration of the fuel injection.

Further, the air-fuel ratio can be adjusted by adjusting the amount of air. The amount of air, and thus the air-fuel ratio, may also be adjusted, for example, by adjusting the position of the throttle and / or a charging device when the engine is a supercharged engine to allow combustion by adjusting the throttle position in the intake manifold and / or or the boost pressure is regulated.

Advantageously, the combustion is controlled so that knocking is avoided. Furthermore, the maximum throttle position and the maximum boost pressure can be limited in turbocharged engines to avoid knocking.

This method of detecting the gaseous fuel type and controlling an internal combustion engine can thus be used to operate a multi-fuel engine in different ways. For example, two different gaseous fuels may be used sequentially one after the other. This can take place, for example, if the desired fuel is not present when the tank needs to be filled. The internal combustion engine is thus manually switched between the fuel types.

Alternatively, the method may be used when the internal combustion engine is operated with two different gaseous fuels of different mixing ratios. The ratio between the fuels may be adjusted depending on operating parameters such as speed and speed to increase the efficiency of the engine. In this embodiment, the engine can be automatically switched between the types of fuel. Furthermore, the mixing ratio can be adjusted automatically.

The method can also be used to operate a motor in several of these operating modes.

The application also provides a computer program for detecting the nature of a gaseous fuel and optionally for controlling an internal combustion engine with a method according to one of the preceding embodiments. This computer program can be stored on a data medium. This data carrier may be a portable storage medium such as a floppy disk or a storage medium in a module or in a control unit of the internal combustion engine. The computer program can also be contained in a microcontroller or a semiconductor chip.

Embodiments of the invention will now be described with reference to the drawings.

1 shows a schematic view of a motor vehicle with a system for detecting the type of gaseous fuel and a system for controlling an internal combustion engine according to a first embodiment,

2 shows an enlarged view of the systems of 1 .

3 shows a diagram of different characteristics of different gaseous fuels, and

4 shows a three-dimensional plot of liquefied petroleum gas condensate content in a mixture of natural gas and LPG.

1 shows a schematic plan view of a motor vehicle 1 with an internal combustion engine 2 , which can be operated with two different gaseous fuels as well as with a liquid fuel. The terms "gaseous" and "liquid" are used herein to refer to the state of the fuel, ie, the gas phase, or liquid phase, just prior to its injection into the combustion chamber 3 or combustion chambers of the engine 1 to describe.

The internal combustion engine also has a system 4 for detecting the gaseous fuel and a system 5 for controlling the combustion in the combustion chambers. 2 shows an enlarged view of the system 4 for detecting the gaseous fuel and the system 5 to control the combustion of 1 ,

The internal combustion engine 2 is about a gearbox 6 with the wheels 7 connected to the motor vehicle. The car 1 also has three separate fuel tanks 8th . 9 . 10 each containing a variety of the three different fuels. In this embodiment, the internal combustion engine 1 with gasoline from the tank 8th , or pure LPG (Liquified Petroleum Gas) from the tank 9 which is also known as LPG, or pure CNG (Compressed Natural Gas) from the tank 10 or a mixture of LPG and CNG. The number of tanks is not limited to three, but can be provided less than three tanks, for example, two tanks for gaseous fuels or more than three tanks. The internal combustion engine 2 based on the Otto principle.

The internal combustion engine 2 has four cylinders in this embodiment 12 with a piston 11 with, each a combustion chamber 3 provides. However, the number of cylinders is not limited to four but may be less than four cylinders, for example three cylinders, or more than four cylinders, for example six cylinders.

Every cylinder 12 has a suction channel 13 on that with the suction pipe 18 is connected and is supplied through the air and fuel in the cylinder. Every cylinder 12 also has an exhaust duct 14 on, through which the exhaust gases from the combustion into the catalyst 15 and in the exhaust pipe 16 of the motor vehicle 1 be steered. The internal combustion engine 2 is a supercharged engine and can be a turbocharger or supercharger 17 have, the charged air to the intake manifold 18 supplies. Air is also released by operating the throttle 19 to the intake manifold 18 delivered.

The internal combustion engine 2 can be operated with different gaseous fuels as well as with a liquid fuel. Consequently, the internal combustion engine points 2 three separate supply lines 20 . 21 . 22 up, different from the three fuel tanks 8th . 9 . 10 to the suction pipe 18 extend. Each supply line is equipped with a valve 23 . 24 . 25 provided so that the tank 8th . 9 . 10 from the suction pipe 18 can be selectively separated or selectively connected to the suction tube. This separation or connection can take place automatically or manually, and allows a change in the type of fuel or the mixing ratio of two fuels.

The properties of different fuels, such as anti-knock and energy density, are not the same. Consequently, the internal combustion engine 2 depending on the type of fuel that is in the intake manifold 18 operated to optimize combustion in the cylinders and avoid knocking. The mixture to be identified of the different gaseous fuels is initially in the fuel supply to the engine, which may be, for example, an injector rail. After the injection in the intake manifold, air is also present.

The system 4 Sensor means for detecting the type of fuel 26 on, which is designed such that during operation of the internal combustion engine 2 the type of fuel that goes to the intake manifold 18 is delivered continuously can be determined. In particular, the type of fuel can be detected directly from measured values of parameters without the fuel and the tank in which the fuel is stored, the system 5 is already known to control the engine.

In this embodiment, the sensor means 26 five sensors, with the help of the type of gaseous fuel is determined. A first sensor 27 measures the air mass flow in the intake manifold 18 , A second sensor 28 is arranged in the exhaust passage or exhaust pipe and measures λ, the lambda value of the fuel-air mixture. A third sensor 29 measures the fuel injector pressure. A fourth sensor 30 measures the intake manifold pressure and a fifth sensor 31 measures the temperature of the fuel in the fuel supply, such as an injector rail for example.

wobei F(T, G) ein temperaturabhängiger Identifikationswert der gasförmigen Kraftstoffzusammensetzung m ._L Luftmassenstrom, C eine geometrieabhängige Konstante der Kraftstoffführung, λ der Lamdba-Wert eines Brennstoff-Luft-Gemisches und Δp die Differenz eines Kraftstoffinjektordrucks und eines Saugrohrdrucks ist.An identification value, from which the type of gaseous fuel from various possible species can be determined, is determined from these measured values. In this embodiment, the identification value is determined by the following formula.

where F (T, G) is a temperature-dependent identification value of the gaseous fuel composition m. _L Air mass flow, C is a geometry-dependent constant of the fuel guide, λ is the Lamdba value of a fuel-air mixture and Δp is the difference of a fuel injector pressure and a Saugrohrdrucks.

The air mass flow is with the first sensor 27 and the lambda value with the second sensor 28 detected. Δp becomes from the values of the third sensor 29 and the fourth sensor 30 determined.

3 shows a diagram of prior art identification values F (T, G) for various gaseous fuels. When the determined value from the measured parameters is compared with these possibilities, the type of gaseous fuel that is in the intake manifold can be determined 18 is found. These previously known values can be found in one of the systems 4 and 5 get saved.

After the type of fuel is determined, the combustion will be dependent on the fuel type and / or mixing ratio with the system 5 controlled.

The system 5 For controlling the combustion of the gaseous fuel or the gaseous fuels is designed such that it controls the combustion depending on the detected type of gaseous fuel. The type of gaseous fuel used by the cylinders 12 is supplied, thus during operation of the engine 2 continuously measured and the combustion regulated and optimized accordingly.

The system 5 to control the combustion, the ignition timing with the help of another crankshaft sensor 32 and the control of the spark plug 33 and / or by the control of the injector 34 that the fuel in the intake manifold 18 inject, adjust to set the fuel injector pressure and / or the duration of the fuel injection. As a result, the combustion for the detected fuel can be optimized. Furthermore, the system can 5 set the maximum throttle position and the maximum boost pressure with supercharged engines to avoid knocking, as in the 1 and 2 with the control lines 35 and 36 is shown.

The air-fuel ratio may be further adjusted by the amount of air to control the combustion. The amount of air, and hence the air-fuel ratio, may also be adjusted, for example, by adjusting the position of the throttle and / or the amount of air that is directed from the compressor into the intake manifold.

Embodiments of the control of the internal combustion engine 2 with the system 4 for detecting the type of gaseous fuel and the system 5 to control the combustion will now be explained.

The engine can be operated with any mixing ratio of LPG and CNG, ranging from pure LPG and no CNG content to no LPG and pure CNG content. It is the task of the system to continuously adjust the operation of the engine to the currently existing mixing ratio such that the engine with the best possible efficiency is operated. The system must be able to adapt the engine's operating parameters to the widely differing stoichiometric air conditions, to the very different knocking properties and to the current tau curves, in order to avoid fuel condensates and to adapt to the very different energy densities of the respective mixing ratio to ensure optimum engine operation.

A particularly advantageous embodiment of the system is to combine the two gaseous fuels - even before the injection into the engine - as a mixture and inject the same injectors into the engine, as in the 1 and 2 with the fuel injector 34 is shown. In the case of LPG and CNG, both fuels would be in gaseous mixture in the fuel supply line, making the use of the same variable gas mixture injector extremely practical, since this lessens the tight space on the engine (package) less than with separate injectors and so on minimized costs.

Another advantage of the gas mixture injection by the / the same injector (s) is that it is structurally still possible, further injectors 37 for additional liquid fuel (eg for gasoline) to optionally enable liquid fuel operation.

For operation with blending the gaseous fuels prior to injection, it is assumed that the fuel mixture is such that condensation of the fuel with the higher boiling point is precluded. Since the gas injector should be designed for the gaseous phase, would be injected by unplanned injection of liquid parts a significantly different amount of fuel, resulting in uncontrollable engine behavior (knocking). For example, liquid LPG fractions which have precipitated out of the gaseous phase by retrograde condensation and accumulate in fuel system siphon sites may be entrained and injected under appropriate flow conditions. Even knock control systems are then not always able to avoid a knocking damage to the engine.

The task of the gaseous fuel mixture preparation is therefore to safely avoid the wet steam region of the current gaseous fuel mixture. 4 shows a qualitative picture for the condensate content β of a natural gas / LPG mixture. The forbidden area that can cause knocking is below the topographical area shown, where both gaseous and liquid fuel are present.

The adjustment of the manipulated variable of the injection pressure is carried out by the analysis of the gas mixture described below, starting from the "safe" side, that is, starting from low injection pressures that cause no condensate. About the gas analysis described, the engine parameters - such. As the injection pressure - then brought to the optimal values.

m ._L

= Luftmassenstrom

m ._B

= Gaskraftstoffmassestrom

l_st

= Stöchiometrisches Luftverhältnis

l

= Aktuelles Luftverhältnis

An advantage of the system described here is that the necessary components are usually already present on the motors. This becomes clear in the following description:
The lambda value of a fuel-air mixture results in:

m. _L

= Air mass flow

m. _B

= Gaseous fuel mass flow

l _st

= Stoichiometric air ratio

l

= Current air ratio

C

= Geometrieabhängige Konstante der Kraftstofführung

ρ(T, G)

= Temperatur und Gaskraftstoff -abhängige Dichte

η(T, G)

= Temperatur- und Gaskraftstoff -abhängige dynamische Viskosität (im Bereich sinnvoller Injektionsdrücke wenig druckabhängig)

Δp

= Differenz Injektionsdruck zu Saugrohrdruck (Ladedruck bei aufgeladenem Motor)

T

= Thermodynamische Temperatur

G

= Vorliegende Gaskraftstoff-Mischung

The fuel mass flow is:

C

= Geometry-dependent constant of the fuel guide

ρ (T, G)

= Temperature and gas fuel-dependent density

η (T, G)

= Temperature and gas fuel-dependent dynamic viscosity (in the range of reasonable injection pressures little pressure-dependent)

Ap

= Differential injection pressure to intake manifold pressure (charge pressure with charged engine)

T

= Thermodynamic temperature

G

= Present gas fuel mixture

From (I) and (II) results as a temperature-dependent identification value for the gaseous fuel composition:

• CNG G20 = 100 Vol% Methan
• CNG G25 = 84 Vol% Methan, 16 Vol% Stickstoff
• LPG A = 85 Vol% Propan, 15 Vol% Butan
• LPG B = 30 Vol% Propan, 70 Vol% Butan

To characterize the bandwidths of the gas fuels CNG and LPG, the limit qualities used in the exhaust gas type tests will be selected below as representatives.

• CNG G20 = 100% by volume methane
• CNG G25 = 84% by volume of methane, 16% by volume of nitrogen
• LPG A = 85% by volume of propane, 15% by volume of butane
• LPG B = 30% by volume of propane, 70% by volume of butane

References and calculations give the following values (here for t = 25 ° C., Δp = 2 bar), which are summarized in Table 1. R ρ η lst ρ / η · lst ρ% ρ / η% ρ / η · lst% J / (kgK) kg / m3 Ns / m2 s / m2 G20 518.3 1.3 11.2 17.3 2 29.9 20.05 23.0 G25 462.9 1:45 12.3 13 1:53 33.3 20.9 17.6 LPG A 180.8 3.71 8.2 15.7 7.1 85.3 80.1 81.6 LPG B 154.2 4:35 7.7 15.6 8.7 100.0 100.0 100 Table 1

On the basis of these characteristics a clear distinction of the gas compositions G is possible. In this case, instead of the blue characteristic of the factor F (T, G), the density of the gas mixture or the quotient of density and dynamic viscosity can be used as the basis of a motor control.

In the following, however, consider the factor F (T, G). The blue curve shown above represents an isothermal curve of F (T = const., G). The overall characteristic of F (T, G) is given as a map, which depends on the gas fuel composition G and its temperature T.

According to equation (III), the determination of F (T, G) can take place with measured values of sensors present on the motor.

• 1. Luftmassenmesser für m_L
• 2. Lambda-Sonde für λ
• 3. Ansaug- oder Ladedrucksensor, sowie Injektions-Raildruck-Sensor zur Ermittlung von Δp
• 4. Injektions-Rail-Temperatur-Sensor zur Ermittlung von T

These sensors are as follows:

• 1. Air mass meter for m _L
• 2. Lambda probe for λ
• 3. Intake or charge pressure sensor, as well as injection rail pressure sensor for determining Δp
• 4. Injection rail temperature sensor for determining T

• 1. Der Motor wird bei gegebenen Injektionsdruck von der Lambda-Regelung durch Anpassung der Injektionsdauer der Injektoren auf den gewünschten Lambda-Wert eingeregelt
• 2. Durch Messung des Luftmassenstromes in dem Motor, des Injektionsdruckes, des Saugrohr- bzw. Ladedruckes sowie mit dem eingeregelten Lambda-Wert kann nach Gleichung (III) der Faktor F(T, G) ermittelt werden. Die vorhandene Konstante C ist abhängig von der Geometrie des Injektionssystems und daher bekannt
• 3. Durch Messung der Injektionstemperatur wird die Isotherme des Faktors F(T = konst., G) aus dem vorhandenen Kennfeld bestimmt und der unter 2. berechnete Wert F(T, G) auf der Isotherme gesucht. Dabei ist es vorteilhaft, wie folgt eine Bereichsunterscheidung vorzunehmen, die auch in der 3 dargestellt ist.
• A. Niedrige F(T, G)-Werte → CNG-Bereich Bereich kann mehrdeutige Werte für F(T, G) ergeben, jedoch kann aufgrund der niedrigen Werte eindeutig auf den alleinigen Kraftstoff CNG geschlossen werden.
• B. Weiter Bereich mittlerer F(T, G)-Werte → CNG/LPG-Mischbereich Eindeutige Werte für F(T, G), welche einem bestimmten Mischungsverhältnis CNG/LPG zugeordnet werden können
• C. Hohe F(T, G)-Werte → LPG-Bereich Eindeutige Werte für F(T, G), welche einem bestimmten Mischungsverhältnis LPG A/LPG B zugeordnet werden können

The following description is intended to describe the process of identifying the current gas fuel mixture. This determination runs continuously during engine operation to always identify the current gas mixture:

• 1. The engine is adjusted at given injection pressure of the lambda control by adjusting the injection duration of the injectors to the desired lambda value
• 2. The factor F (T, G) can be determined by measuring the air mass flow in the engine, the injection pressure, the intake manifold pressure and the adjusted lambda value according to equation (III). The existing constant C is dependent on the geometry of the injection system and therefore known
• 3. By measuring the injection temperature, the isotherm of the factor F (T = const., G) is determined from the existing map and the value F (T, G) calculated under 2. is searched for on the isotherm. It is advantageous to make a distinction as follows, which also in the 3 is shown.
• A. Low F (T, G) Values → CNG Range Range may give ambiguous values for F (T, G), but due to the low values, CNG can be uniquely determined to be the sole CNG fuel.
• B. Wide range of mean F (T, G) values → CNG / LPG mixing range Unique values for F (T, G), which can be assigned to a specific mixing ratio CNG / LPG
• C. High F (T, G) values → LPG range Unique values for F (T, G), which can be assigned to a specific mixing ratio LPG A / LPG B

After the current gas mixture G is known, there are also essential fuel information for further control of the engine. These are z. B. the knock resistance, the stoichiometric air ratio, the tau curves for the LPG content in the gas mixture for the areas B, C and the energy density, which can be read from stored in the engine control unit databases.

• 1. Zündzeitpunkt
• 2. Maximale Drosselklappenstellung
• 3. Maximaler Ladedruck bei aufgeladenen Motoren
• 4. Injektionsdruck des Gasgemisches (Vermeidung von Kondensationseffekten in den Bereichen B und C sowie und Anpassung an die Energiedichte des Gaskraftstoffes)
• 5. Ggf. Anpassung der Injektionszeiten der Gasinjektoren

Following this, appropriate engine parameters are to be adjusted so that the engine efficiency is optimally operated without hazardous effects, such as knocking engine operation, z. As by fuel condensation to risk. These parameters dependent on the gas mixture G are as follows:

• 1st ignition point
• 2. Maximum throttle position
• 3. Maximum boost pressure with supercharged engines
• 4. Injection pressure of the gas mixture (avoiding condensation effects in the areas B and C as well as and adaptation to the energy density of the gas fuel)
• 5. If necessary Adjustment of the injection times of the gas injectors

From 4. shows that the injection pressure of the gas mixture should be regulated. This is on the one hand necessary when using the same gas injectors (gas mixture is generated in front of the engine), since the energy densities of the different fuel gases are sometimes far apart. So z. B. the energy density of gaseous LPG about three times higher than that of CNG, which would mean without injection pressure control too much bandwidth in the injection volume flow and makes difficulties with the same injectors. Therefore, an adjustment of the injection pressure is recommended especially in the mixing area B.

On the other hand, it must be strictly observed that the regulated parameter injection pressure at the existing injection temperature never drifts into the wet steam region of the current gas mixture B or C, which can lead to sudden injection of liquid-accumulated liquid gas components by condensation effects, which uncontrollable knocking behavior and thus the destruction of the engine Episode has.

It should also be mentioned that other existing control circuits of the engine - such. As the knock control - continue to be used to z. B. to have a quick countermeasure when knocking should occur.

• 1. Fahrzeug mit manueller Betriebsartenumschaltung zwischen Gaskraftstoff und Benzin, wobei der Gasbetrieb mit einer beliebigen Mischung der verschiedenen Gaskraftstoffe (z. B. aus CNG und LPG) dargestellt wird
• 2. Fahrzeug mit manueller Betriebsartenumschaltung zwischen den jeweiligen Gaskraftstoffen und Benzin, z. B. jeweils CNG-Betrieb oder LPG-Betrieb oder Benzinbetrieb
• 3. Fahrzeug mit automatischer Umschaltung zwischen den verschiedenen Kraftstoffen, abhängig von Kriterien wie z. B. der jeweiligen Kraftstofffüllmenge (Fahrzeug entscheidet automatisch, ob z. B. CNG, LPG oder Benzin zum Betrieb verwendet wird)
• 4. Einer beliebigen Kombination aus den zuvor genannten Varianten 1 bis 3

By means of the described system, different operating modes can be realized with a corresponding gas vehicle, depending on the customer's wishes. This could be z. For example:

• 1. Manual mode changeover vehicle between gas fuel and gasoline, wherein the gas operation is represented with any mixture of different gas fuels (eg from CNG and LPG)
• 2. Vehicle with manual mode switching between the respective gas fuels and gasoline, eg. B. each CNG operation or LPG operation or gasoline operation
• 3. Vehicle with automatic switching between the different fuels, depending on criteria such. Eg the respective fuel fill quantity (vehicle decides automatically whether eg CNG, LPG or gasoline is used for operation)
• 4. Any combination of the aforementioned variants 1 to 3

LIST OF REFERENCE NUMBERS

1

motor vehicle

2

internal combustion engine

3

combustion chamber

4

System for detecting a gaseous fuel

5

System for controlling the combustion

6

transmission

7

wheel

8th

first fuel tank

9

second fuel tank

10

third fuel tank

11

piston

12

cylinder

13

intake port

14

exhaust duct

15

catalyst

16

exhaust pipe

17

compressor

18

suction tube

19

throttle

20

first fuel supply line

21

second fuel supply line

22

third fuel supply

23

first valve

24

second valve

25

third valve

26

sensor means

27

first sensor

28

second sensor

29

third sensor

30

fourth sensor

31

fifth sensor

32

crankshaft sensor

33

spark plug

34

fuel injector

35

throttle control

36

Boost pressure control

37

Injector

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10318963 A1 [0002, 0006]

Claims (15)

System ( 4 ) for detecting the type of gaseous fuel used to operate an internal combustion engine ( 2 ) with a suction tube ( 18 ) and at least one cylinder ( 12 ) is used, wherein for operating the internal combustion engine ( 2 ) at least two different gaseous fuels in the cylinder ( 12 ) can be burned, whereby the system ( 4 ) Sensor means ( 26 ) for measuring at least one parameter characterizing the nature of the gaseous fuel, the sensor means ( 26 ) is designed such that during operation of the internal combustion engine ( 2 ) the type of gaseous fuel which is present in the intake manifold ( 18 ) is detected from the measured parameter. System ( 4 ) according to claim 1, wherein the sensor means ( 26 ) a first sensor ( 27 ) for measuring an air mass flow in the intake manifold of the cylinder and / or a second sensor ( 28 ) for measuring the lambda value λ and / or a third sensor ( 29 ) for measuring a fuel injector pressure and / or a fourth sensor ( 30 ) for measuring an intake manifold pressure and / or a fifth sensor ( 31 ) for measuring a temperature of the fuel. System ( 4 ) according to claim 1 or claim 2, wherein the system ( 4 ) further means for detecting an identification value, which characterizes the type of fuel, from measured values of an air mass flow in the intake manifold ( 18 ) and / or λ, the lambda value, and / or a fuel injector pressure and / or an intake manifold pressure and / or a temperature, wherein the identification value, the density, the viscosity and / or the ratio

where F (T, G) is a temperature-dependent identification value of the gaseous fuel composition, m. _L Air mass flow, C is a geometry-dependent constant of the fuel guide, λ is the lambda value of a fuel-air mixture and Δp is the difference of a fuel injector pressure and a Saugrohrdrucks. System ( 4 ) according to claim 3, wherein the means for detecting the identification value comprise known identification values of various gaseous fuels and means for comparing the detected identification value with the previously known identification values to determine the type of fuel in the intake manifold. System ( 5 ) for controlling an internal combustion engine ( 2 ) with a suction tube ( 18 ) and at least one cylinder ( 12 ), wherein for operating the internal combustion engine ( 2 ) at least two different gaseous fuels in the cylinder ( 12 ) can be burned, which is a system ( 4 ) for detecting the type of gaseous fuel according to one of claims 1 to 4, and means for controlling the combustion of the gaseous fuel in the cylinder, wherein the means ( 32 . 33 . 34 . 35 . 36 ) is designed for controlling the combustion such that during operation of the internal combustion engine ( 2 ) the combustion is regulated depending on the detected type of fuel. System ( 5 ) according to claim 5, wherein the means for controlling means ( 32 . 33 ) for adjusting the ignition timing and / or means ( 33 ) for adjusting the fuel injector pressure and / or means ( 34 ) for adjusting the duration of the fuel injection. Internal combustion engine ( 2 ) with a suction tube ( 18 ) and at least one cylinder ( 12 ), wherein for operating the internal combustion engine ( 2 ) at least two different gaseous Fuels in the cylinder ( 12 ) and with a system ( 4 . 5 ) according to one of claims 1 to 6. Motor vehicle ( 1 ) with an internal combustion engine ( 2 ) with a suction tube ( 18 ) and at least one cylinder ( 12 ), wherein for operating the internal combustion engine ( 2 ) at least two different gaseous fuels in the cylinder ( 12 ) and with a system ( 4 . 5 ) according to one of claims 1 to 6. Method for detecting the type of gaseous fuel used to operate an internal combustion engine ( 2 ) with a suction tube ( 18 ) and at least one cylinder ( 12 ), wherein at least two different gaseous fuels in the cylinder ( 12 ) can be burned, during the operation of the internal combustion engine ( 2 ) the type of gaseous fuel which is present in the intake manifold ( 18 ) is detected directly by measuring. The method of claim 9, wherein for detecting the type of fuel, an air mass flow in the intake manifold ( 18 ) and / or λ, the lambda value of a fuel-air mixture, and / or a fuel injector pressure and / or an intake manifold pressure and / or a temperature of the fuel are measured. A method according to claim 9 or claim 10, wherein an identification value indicative of the nature of the fuel is detected from measured values of air mass flow, λ, fuel injector pressure, manifold pressure, and / or temperature, the identification value being density, viscosity and / or the relationship

where F (T, G) is a temperature-dependent identification value of the gaseous fuel composition, m. _L Air mass flow, C is a geometry-dependent constant of the fuel guide, λ is the Lamdba value of a fuel-air mixture and Δp is the difference of a fuel injector pressure and a Saugrohrdrucks. Method according to claim 11, wherein after determining the identification value of the gaseous fuel, this is compared with previously known identification values of various gaseous fuels in order to determine the type of fuel in the intake manifold ( 18 ). Method for controlling an internal combustion engine ( 2 ) with a suction tube ( 18 ) and at least one cylinder ( 12 ), wherein for operating the internal combustion engine ( 2 ) at least two different gaseous fuels can be burned, during the operation of the internal combustion engine ( 2 ) the nature of the gaseous fuel is determined by a method according to one of claims 9 to 12, and then the combustion of the gaseous fuel in the cylinder ( 12 ) is regulated depending on the detected type of fuel. Method according to claim 13, wherein the combustion in the cylinder ( 12 ) is controlled by adjusting the ignition timing and / or the fuel injector pressure and / or the duration of the fuel injection and / or the throttle position in the intake manifold and / or the boost pressure. Computer program for carrying out a method according to one of Claims 9 to 14.

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