CN115683641A - Carbon-free gas engine EGR rate detection method and test bench - Google Patents
Carbon-free gas engine EGR rate detection method and test bench Download PDFInfo
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Abstract
The invention relates to the technical field of engine exhaust gas recirculation control, in particular to a carbon-free gas engine EGR rate detection method and a test bed, wherein the detection method comprises the following steps: determining an air-fuel equivalence ratio according to the mass flow rate and the air mass flow rate of the carbon-free fuel gas entering the engine side; determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio; determining an oxygen fraction error according to the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the air outlet side; determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side; and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow. Can solve the problems that the carbon-free gas engine in the prior art does not contain carbon element and can not adopt CO 2 The sensor measures the EGR rate, and the gas pulse measurement influences the measurement precision of the EGR rate by adopting a detection mode of a Venturi tube.
Description
Technical Field
The invention relates to the technical field of engine exhaust gas recirculation control, in particular to a carbon-free gas engine EGR rate detection method and a test bench.
Background
The EGR rate is defined as the ratio of the amount of exhaust gas recirculated to the total amount of intake air drawn into the cylinder, and reasonable control of the EGR rate is extremely important to the purification effect of nitrogen oxides and the overall emissions, and a method is required to quantify the EGR rate when performing a calibration test to evaluate the influence of exhaust gas recirculation on the engine performance.
The EGR rate detection method of the engine is based on the traditional carbon-containing fossil fuel engine. It is therefore possible to detect CO in the intake manifold and the exhaust manifold 2 The concentration measures the EGR rate. Because the carbon-free gas engine does not contain carbon element, CO can not be adopted 2 The sensor measures the EGR rate. There is also a method of detecting the EGR rate by detecting the upstream pressure of the venturi. However, with the venturi approach, the gas pulse will affect the accuracy of the EGR rate measurement.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for detecting the EGR rate of a carbon-free gas engine and a test bench, which can solve the problems that the carbon-free gas engine in the prior art does not contain carbon element and cannot adopt CO 2 The sensor(s) of (2) measure the EGR rate and, with the venturi tube detection mode, the gas pulse will measure the problem of affecting the accuracy of the EGR rate measurement.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a carbon-free gas engine EGR rate detection method, which comprises the following steps:
determining an air-fuel equivalence ratio according to the mass flow rate of the carbon-free fuel gas entering the engine side and the mass flow rate of air;
determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio;
determining an oxygen fraction error according to the oxygen mole fraction at the intake side and the oxygen mole fraction at the exhaust side;
determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side;
and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow.
In some alternatives, the determining an air-fuel equivalence ratio based on a mass flow rate of the carbon-free fuel gas and a mass flow rate of air entering the engine side includes:
acquiring the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side;
according to the formula
Determining an air-fuel equivalence ratio lambda;
wherein the content of the first and second substances,
for the mass flow of air into the engine side,
alpha is the air-fuel coefficient for the mass flow of the carbon-free fuel gas entering the engine side.
In some alternatives, said determining molecular mass of exhaust gas of the EGR cycle based on air-fuel equivalence ratio comprises:
according to the formula
Determining exhaust gas molecular mass MW of EGR cycle EGR ；
Wherein, a 1 、a 2 、b 1 、b 2 、c 1 、c 2 、d 1 And d 2 Respectively, are the calibration fitting coefficients.
In some alternatives, said determining an oxygen fraction error based on the intake side oxygen mole fraction and the exhaust side oxygen mole fraction comprises:
acquiring an air inlet side oxygen mole fraction and an exhaust side oxygen mole fraction;
according to the formula
Determining oxygen fraction error
Wherein, the first and the second end of the pipe are connected with each other,
is the oxygen mole fraction on the intake side,
is the mole fraction of oxygen on the exhaust side,
is the oxygen mole fraction in air.
In some optional schemes, before acquiring the oxygen mole fraction on the exhaust side, the carbon-free gas concentration in the exhaust gas of the engine is also detected, a detection signal is transmitted to the processor, and when the carbon-free gas concentration is larger than a set concentration value, the detection of the oxygen mole fraction on the exhaust side is stopped.
In some alternatives, said determining an EGR cycle mass flow based on the oxygen fraction error, the exhaust gas molecular mass, the air molecular mass, and the air mass flow entering the engine side comprises:
according to the formula
Determining EGR cycle mass flow
Wherein, the first and the second end of the pipe are connected with each other,
for the mass flow of air into the engine side, MW air Is the molecular mass of air, MW EGR Is the molecular mass of the exhaust gas of the EGR cycle.
In some alternatives, said determining an EGR rate based on an EGR cycle mass flow, a carbon-free gas mass flow into an engine side, and an air mass flow, comprises:
according to the formula
The rate of EGR is determined,
wherein, the first and the second end of the pipe are connected with each other,
for the mass flow of air into the engine side,
for the mass flow of the carbon-free gas into the engine side,
is the EGR loop mass flow.
On the other hand, the invention also provides a test bed for detecting the EGR rate of the carbon-free gas engine, which is used for implementing any one of the EGR rate detection methods of the carbon-free gas engine, and comprises the following steps:
a carbon-free gas flow meter, an air flow meter and an air intake side wide-range type oxygen sensor for being disposed on an intake side of the engine, and an exhaust side wide-range type oxygen sensor for being disposed on an exhaust side of the engine, the carbon-free gas flow meter being for detecting a mass flow rate of carbon-free gas entering the engine side, the air flow meter being for detecting a mass flow rate of air entering the engine side, the air intake side wide-range type oxygen sensor being for detecting an intake side oxygen mole fraction, the exhaust side wide-range type oxygen sensor being for detecting an exhaust side oxygen mole fraction;
and the processor is in signal connection with the carbon-free gas flow meter, the air inlet side wide-area type oxygen sensor and the exhaust side wide-area type oxygen sensor and is used for determining the EGR rate according to the mass flow of the carbon-free gas entering the engine side, the mass flow of the air entering the engine side, the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the exhaust side.
In some optional solutions, the carbon-free gas engine EGR rate detection test bed further comprises a carbon-free gas sensor for detecting a carbon-free gas concentration in the exhaust gas of the engine and transmitting a detection signal to the processor, the carbon-free gas sensor being disposed on the exhaust gas side of the engine and located before the inlet of the circulation duct.
In some optional schemes, the test bed for detecting the EGR rate of the carbon-free gas engine further comprises a detection pipeline, two ends of the detection pipeline are used for being connected with an exhaust pipeline of the engine, and are sequentially located in the flowing direction of exhaust gas of the exhaust pipeline, the carbon-free gas sensor is arranged on the detection pipeline, and a cooler is arranged between an upstream air inlet of the detection pipeline connected with the exhaust pipeline and the carbon-free gas sensor.
Compared with the prior art, the invention has the advantages that: according to the scheme, the air-fuel equivalence ratio is determined according to the mass flow of the carbon-free fuel gas entering the engine side and the mass flow of the air; determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio; determining an oxygen fraction error according to the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the air outlet side; determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side; and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow. By adopting the scheme, the EGR rate of the engine taking carbon-free fuel gas as fuel can be measured. And the venturi tube is not required to be used for detection, so that the detection result is relatively accurate.
In addition, in some optional schemes, a carbon-free fuel gas sensor is arranged on an exhaust pipeline of the engine, and the content of the carbon-free fuel gas in the exhaust pipe is monitored in real time. The intake-side wide-area oxygen sensor in the intake duct and the exhaust-side wide-area oxygen sensor in the exhaust duct are activated only when the carbon-free gas content in the exhaust duct is less than a set concentration value within a time period. If the concentration of the carbon-free gas is greater than the set concentration value, the detection of the oxygen mole fraction at the exhaust side is stopped, and the safety accident caused by the explosion of the carbon-free gas in the exhaust pipe is avoided.
The exhaust gas is led out of the exhaust pipeline by the aid of the detection pipeline, combusted tail gas passes through the detection pipeline, a cooler is arranged between an upstream air inlet and a carbon-free gas sensor, which are connected with the exhaust pipeline, of the detection pipeline, and the carbon-free gas sensor arranged on the detection pipeline can detect the cooled tail gas after the temperature of the tail gas combusted by the engine is reduced. For example, currently available hydrogen sensors have a maximum operating temperature below 90 ℃, so the exhaust gas is cooled to below 90 ℃ by a cooler, and the hydrogen concentration in the exhaust gas is measured by a hydrogen sensor.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a method for detecting an EGR rate of a carbon-free gas engine according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a carbon-free gas engine EGR rate detection test bed in the embodiment of the invention.
In the figure: 1. an engine; 11. a spark plug; 2. an air intake duct; 21. a throttle valve; 22. an intake side wide-area type oxygen sensor; 23a, a hydrogen injector; 23b, a hydrogen in-cylinder direct injection injector; 23c, an ammonia injector; 24. a mixer; 3. an exhaust duct; 31. an exhaust-side wide-area oxygen sensor; 32. a carbon-free gas sensor; 33. detecting a pipeline; 34. a cooler; 4. a circulating pipeline; 41. an EGR cooler; 42. an EGR valve; 43. an EGR one-way valve; 5. a processor.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
Fig. 1 is a flowchart of a method for detecting an EGR rate of a carbon-free gas engine according to an embodiment of the present invention, and as shown in fig. 1, the present invention provides a method for detecting an EGR rate of a carbon-free gas engine, including the following steps:
s1: the air-fuel equivalence ratio is determined based on the mass flow of the carbon-free fuel gas and the mass flow of air entering the engine side.
In some optional embodiments, step S1 comprises:
s11: and acquiring the mass flow rate of the carbon-free fuel gas and the mass flow rate of the air entering the engine side.
In this example, the mass flow rate of the carbon-free gas and the mass flow rate of the air entering the engine side are obtained by providing the mass flow rate of the carbon-free gas and the mass flow rate of the air at the side entering the engine, respectively. In this example, the test is performed on a test rig, and the mass flow of the carbon-free fuel gas and the mass flow of air into the engine side can be obtained from the air supply.
S12: according to the formula
The air-fuel equivalence ratio, λ, is determined, wherein,
is the mass flow of air on the intake side,
α is an air-fuel ratio, i.e., a ratio of a stoichiometric air-fuel ratio of 1kg to a stoichiometric air-fuel ratio of the theoretical amount (mass) of air required for complete combustion of the fuel, for a mass flow rate of the carbon-free fuel gas entering the engine side.
In this example, the carbon-free fuel gas is hydrogen, and the air-fuel coefficient α is 34.2. When the adopted carbon-free fuel gas is other fuel gas, such as hydrogen ammonia fuel, the value of the air-fuel coefficient alpha can be adjusted adaptively.
S2: based on the air-fuel equivalence ratio, the molecular mass of the exhaust gas of the EGR cycle is determined.
In some optional embodiments, step S2 comprises:
according to the formula
Determining exhaust gas molecular mass MW of EGR cycle EGR ；
Wherein, a 1 、a 2 、b 1 、b 2 、c 1 、c 2 、d 1 And d 2 Respectively, are the calibration fitting coefficients.
In this example, the carbon-free fuel gas is hydrogen gas, a 1 ＝5.12，a 2 ＝0.15，b 1 ＝177.41，b 2 ＝37.12，c 1 ＝0.26，c 2 ＝0.21，d 1 ＝12.53，d 2 ＝6.63。
Namely, it is
When λ is greater than or equal to 1, adopt
Calculating when λ is less than 1, using
And (4) calculating.
When the carbon-free fuel gas is other fuel gas, a 1 、a 2 、b 1 、b 2 、c 1 、c 2 、d 1 And d 2 And (5) recalibrating.
S3: an oxygen fraction error is determined based on the intake side oxygen mole fraction and the exhaust side oxygen mole fraction.
In some optional embodiments, step S3 comprises:
s31: an intake side oxygen mole fraction and an exhaust side oxygen mole fraction are obtained.
In this example, an intake side wide-range oxygen sensor for detecting an intake side oxygen mole fraction and an exhaust side wide-range oxygen sensor for detecting an exhaust side oxygen mole fraction are provided on the side of the intake to the engine and on the side of the exhaust to the engine.
S32: according to the formula
Determining oxygen fraction error
Wherein the content of the first and second substances,
is the oxygen mole fraction on the intake side,
is the mole fraction of oxygen on the exhaust side,
is the oxygen mole fraction in air.
In this example, the oxygen mole fraction in air is taken to be 0.209; of course, in actual use, the oxygen mole fraction in the air can be re-determined according to the altitude.
In addition, in some optional embodiments, before acquiring the exhaust-side oxygen mole fraction, the carbon-free gas concentration in the engine exhaust is also detected, a detection signal is transmitted to the processor, and when the carbon-free gas concentration is greater than a set concentration value, the detection of the exhaust-side oxygen mole fraction is stopped.
When the wide-area oxygen sensor starts measurement, the front-end probe of the sensor is heated to be more than 600 ℃. If the content of the carbon-free fuel gas in the exhaust gas is high, the carbon-free fuel gas can be ignited, so that the concentration of the carbon-free fuel gas in the exhaust gas of the engine needs to be detected, and if the concentration of the carbon-free fuel gas is greater than a set concentration value, the detection of the oxygen mole fraction on the exhaust side is stopped, so that the carbon-free fuel gas is prevented from exploding in an exhaust pipe to cause safety accidents.
In this example, hydrogen is used as the carbon-free fuel gas, and the content of unburned hydrogen in the exhaust pipe is high when a lean combustion mode is used in the hydrogen engine. While the ignition limit for hydrogen is very broad. Therefore, it is necessary to control the EGR rate to prevent the unburned hydrogen from being burned in the exhaust pipe and to avoid explosion.
S4: and determining the EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the air mass flow at the air inlet side.
In some optional embodiments, step S4 comprises:
according to the formula
Determining EGR cycle mass flow
Wherein the content of the first and second substances,
for air mass flow at the inlet side, MW air Is the molecular mass of air, MW EGR Is the molecular mass of the exhaust gas of the EGR cycle.
S5: and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow.
In some optional embodiments, step S5 comprises:
according to the formula
An EGR rate is determined, wherein,
for the mass flow of air on the inlet side,
for the mass flow of the carbon-free gas into the engine side,
is the EGR loop mass flow.
By adopting the method for detecting the EGR rate of the carbon-free gas engine, the air-fuel equivalence ratio is determined according to the mass flow of the carbon-free gas and the mass flow of air entering the engine side; determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio; determining an oxygen fraction error according to the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the air outlet side; determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side; and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow. By adopting the method, the EGR rate of the engine taking carbon-free fuel gas as fuel can be measured. And the venturi tube is not required to be used for detection, so that the detection result is relatively accurate.
Fig. 2 is a schematic structural diagram of an EGR rate detection test bed of a carbon-free gas engine according to an embodiment of the present invention, and as shown in fig. 2, in a hydrogen engine or an ammonia-hydrogen engine (ammonia is injected into a mixer of an intake manifold), an Exhaust Gas Recirculation (EGR) mode is used to reduce in-cylinder combustion temperature, effectively reduce NOx generation, and increase the power of the hydrogen/ammonia-hydrogen engine. In the development of the performance of the hydrogen/ammonia-hydrogen engine, the opening degree of an EGR valve is accurately calibrated according to the EGR rate under different loads of the engine. Accurate measurement of EGR rates is therefore of paramount importance in the development of hydrogen/ammonia-hydrogen engines.
The conventional test bench comprises an engine 1, an air inlet pipeline 2, an exhaust pipeline 3 and an EGR circulating pipeline 4; wherein, an EGR cooler 41, an EGR valve 42 and an EGR one-way valve 43 are arranged on the circulating pipeline 4 in sequence from the connection part with the exhaust pipeline 3 to the connection part with the air inlet pipeline 2; the air inlet pipeline 2 is provided with a throttle valve 21 and a carbon-free gas ejector.
In another aspect, the present invention provides a test bed for detecting an EGR rate of a carbon-free gas engine, which is used for implementing the EGR rate detecting method of the carbon-free gas engine, and includes:
the system comprises a carbon-free gas flow meter, an air flow meter and an air inlet side wide-area type oxygen sensor which are arranged on the side, entering an engine, of the engine, and an air outlet side wide-area type oxygen sensor which is arranged on the side, exiting the engine, of the engine, wherein the carbon-free gas flow meter is used for detecting the mass flow of the carbon-free gas entering the side of the engine, the air flow meter is used for detecting the mass flow of the air entering the side of the engine, the air inlet side wide-area type oxygen sensor is used for detecting the oxygen mole fraction on the air inlet side, and the oxygen mole fraction on the air outlet side of the exhaust side wide-area type oxygen sensor.
And the processor is in signal connection with the carbon-free gas flow meter, the air inlet side wide-area type oxygen sensor and the exhaust side wide-area type oxygen sensor and is used for determining the EGR rate according to the mass flow of the carbon-free gas entering the engine side, the air inlet side air mass flow, the air inlet side oxygen mole fraction and the exhaust side oxygen mole fraction obtained through detection.
According to the EGR rate detection test bed of the carbon-free gas engine, the processor 5 is in signal connection with the carbon-free gas flow meter, the air inlet side wide-area oxygen sensor and the exhaust side wide-area oxygen sensor, the carbon-free gas mass flow entering the engine side, the air inlet side air mass flow, the air inlet side oxygen mole fraction and the exhaust side oxygen mole fraction are obtained and obtained through detection, and the air-fuel equivalence ratio is determined according to the carbon-free gas mass flow and the air mass flow of the air inlet engine side; determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio; determining an oxygen fraction error according to the oxygen mole fraction at the intake side and the oxygen mole fraction at the exhaust side; determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side; and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow. The test bench of this scheme of adoption can measure the EGR rate of the engine of carbon-free gas as fuel.
In this example, the engine 1 is provided with the ignition plug 11, the intake-side wide-range oxygen sensor 22 is provided in the intake pipe 2 between the connection point of the circulation pipe and the intake pipe 2 and the carbon-free gas injector, and the exhaust-side wide-range oxygen sensor 31 is provided in the exhaust pipe 3 between the connection point of the circulation pipe 4 and the exhaust pipe 3 and the engine 1.
When the engine 1 is a hydrogen cylinder direct injection engine, the hydrogen engine is provided with a hydrogen cylinder direct injection injector 23b; when the engine 1 is a hydrogen gas port injection type engine, the intake pipe 2 is provided with a hydrogen injector 23a provided on the intake pipe 2 between the mixer 24 and the engine 1; when the engine 1 is an ammonia-hydrogen engine, a mixer 24 is provided in the intake pipe 2 between the intake-side wide-range oxygen sensor 22 and the engine 1, and an ammonia injector 23c is provided in the mixer 24.
In some optional embodiments, the carbon-free gas engine EGR rate detection test rig further comprises a carbon-free gas sensor for detecting a carbon-free gas concentration in an exhaust gas of the engine and transmitting a detection signal to the processor, the carbon-free gas sensor being disposed on an exhaust gas side of the engine and in front of an inlet of the circulation duct.
In this example, the carbon-free gas sensor 32 is provided in the exhaust-side wide-range oxygen sensor 31 provided in the exhaust pipe 3 between the engine 1, and the wide-range oxygen sensor heats the tip end probe of the sensor to 600 ℃. If the content of the carbon-free gas in the exhaust gas is high, the carbon-free gas can be ignited, therefore, the carbon-free gas sensor 32 is arranged on the exhaust pipeline 3, the concentration of the carbon-free gas in the exhaust gas of the engine is detected, and if the concentration of the carbon-free gas is larger than a set concentration value, the detection of the oxygen mole fraction at the exhaust side is stopped, so that the explosion of the carbon-free gas in an exhaust pipe is avoided, and the safety accident is avoided.
In some optional embodiments, the test bench for detecting the EGR rate of the carbon-free gas engine further comprises a detection pipeline, two ends of the detection pipeline are used for being connected with an exhaust pipeline of the engine, and are sequentially located in the flowing direction of exhaust gas of the exhaust pipeline, the carbon-free gas sensor is arranged on the detection pipeline, and a cooler is arranged between an upstream air inlet of the detection pipeline connected with the exhaust pipeline and the carbon-free gas sensor.
In this embodiment, the two ends of the detection pipeline 33 are connected to the exhaust pipeline 3 of the engine 1, and the two ends are sequentially located in the exhaust flowing direction of the exhaust pipeline 3, so that the exhaust gas after combustion of the engine can pass through the detection pipeline, and the carbon-free gas sensor 32 disposed on the detection pipeline can detect the concentration of the carbon-free gas in the exhaust gas discharged from the engine 1. In addition, although a general carbon-free gas sensor cannot be used in a high-temperature environment, the carbon-free gas sensor cannot directly measure the concentration of carbon-free gas in exhaust gas because the temperature of exhaust gas after engine combustion is high. Set up in this scheme that detection pipeline 33 and exhaust duct 3 are parallelly connected on the carminative flow direction of exhaust duct 3, make the tail gas after the burning, through detection pipeline 33 to be equipped with cooler 34 between the upstream air inlet that detection pipeline and exhaust duct are connected and the carbon-free gas sensor, can cool down the tail gas after the engine burning, make the carbon-free gas sensor who sets up on the detection pipeline 33 can detect the tail gas after the cooling.
In conclusion, the processor is in signal connection with the carbon-free gas flow meter, the air inlet side wide-area oxygen sensor and the exhaust side wide-area oxygen sensor, obtains the detected carbon-free gas mass flow, air inlet side air mass flow, air inlet side oxygen mole fraction and exhaust side oxygen mole fraction of the air inlet engine side, and determines the air-fuel equivalence ratio according to the carbon-free gas mass flow and the air mass flow of the air inlet engine side; determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio; determining an oxygen fraction error according to the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the air outlet side; determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side; and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow on the side of the intake engine and the air mass flow. The test bench of this scheme of adoption can measure the EGR rate of the engine of carbon-free gas as fuel. And the venturi tube is not required to be used for detection, so that the detection result is relatively accurate.
And a carbon-free gas sensor 32 is arranged on an exhaust pipeline of the engine, so that the content of the carbon-free gas in the exhaust pipeline is monitored in real time. The intake-side wide-area oxygen sensor 22 in the intake duct 2 and the exhaust-side wide-area oxygen sensor 31 in the exhaust duct 3 will be activated only when the carbon-free gas content in the exhaust duct is less than the set volume ratio for the period of time. If the concentration of the carbon-free fuel gas is greater than the set concentration value, the detection of the oxygen mole fraction at the exhaust side is stopped, and the explosion of the carbon-free fuel gas in the exhaust pipe is avoided to cause safety accidents.
Utilize detection pipeline 33 to draw out a way waste gas in exhaust duct 3, make the tail gas after the burning, through detection pipeline 33 to be equipped with cooler 34 between the upstream air inlet that detection pipeline 33 and exhaust duct 3 are connected and carbonless gas sensor 32, can cool down the tail gas after the engine burning, make the carbonless gas sensor who sets up on the detection pipeline 33 can detect the tail gas after the cooling. For example, currently available hydrogen sensors have a maximum operating temperature below 90 ℃, so the exhaust gas is cooled to below 90 ℃ by a cooler, and the hydrogen concentration in the exhaust gas is measured by a hydrogen sensor. In addition, the scheme can be used for engines with zero carbon mixed fuel, such as hydrogen engines or engines with ammonia-hydrogen mixed fuel.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
It is noted that, in this application, relational terms such as "first" and "second," and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for detecting the EGR rate of a carbon-free gas engine is characterized by comprising the following steps:
determining an air-fuel equivalence ratio according to the mass flow rate of the carbon-free fuel gas entering the engine side and the mass flow rate of air;
determining the molecular mass of the exhaust gas of the EGR circulation according to the air-fuel equivalence ratio;
determining an oxygen fraction error according to the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the air outlet side;
determining EGR circulation mass flow according to the oxygen fraction error, the molecular mass of the exhaust gas, the molecular mass of the air and the mass flow of the air at the air inlet side;
and determining the EGR rate according to the EGR circulation mass flow, the carbon-free gas mass flow entering the engine side and the air mass flow.
2. The method for detecting an EGR rate of a carbon-free gas engine as claimed in claim 1, wherein the determining an air-fuel equivalence ratio based on a mass flow rate of the carbon-free gas and a mass flow rate of air entering the engine side comprises:
acquiring the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side;
according to the formula
Determining an air-fuel equivalence ratio lambda;
wherein the content of the first and second substances,
for the mass flow of air into the engine side,
alpha is the air-fuel coefficient for the mass flow of the carbon-free fuel gas entering the engine side.
3. The method for detecting the EGR rate of a carbon-free gas engine according to claim 1, wherein the determining the molecular mass of the exhaust gas of the EGR cycle according to the air-fuel equivalence ratio comprises:
according to the formula
Determining exhaust gas molecular mass MW of EGR cycle EGR ；
Wherein, a 1 、a 2 、b 1 、b 2 、c 1 、c 2 、d 1 And d 2 Respectively, are the calibration fitting coefficients.
4. The method of claim 1, wherein determining an oxygen fraction error based on an intake side oxygen mole fraction and an exhaust side oxygen mole fraction, comprises:
acquiring the oxygen mole fraction of an air inlet side and the oxygen mole fraction of an exhaust side;
according to the formula
Determining oxygen fraction error
Wherein the content of the first and second substances,
is the oxygen mole fraction on the intake side,
is the mole fraction of oxygen on the exhaust side,
is the oxygen mole fraction in air.
5. The method of claim 4, wherein a carbon-free gas engine EGR rate detection is further detected in the engine exhaust before the exhaust side oxygen mole fraction is obtained, and wherein a detection signal is transmitted to the processor, and wherein the detection of the exhaust side oxygen mole fraction is stopped when the carbon-free gas concentration is greater than a set concentration value.
6. The method of claim 1, wherein determining an EGR cycle mass flow based on the oxygen fraction error, the exhaust gas molecular mass, the air molecular mass, and the intake side air mass flow comprises:
according to the formula
Determining EGR cycle mass flow
Wherein the content of the first and second substances,
for air mass flow at the inlet side, MW air Is the molecular mass of air, MW EGR Is the molecular mass of the exhaust gas of the EGR cycle.
7. The method for detecting an EGR rate of a carbon-free gas engine as claimed in claim 1, wherein the determining the EGR rate based on the EGR cycle mass flow rate, the engine-side carbon-free gas mass flow rate and the air mass flow rate comprises:
according to the formula
The rate of EGR is determined,
wherein the content of the first and second substances,
for the mass flow of air on the inlet side,
for the mass flow of the carbon-free gas into the engine side,
is the EGR loop mass flow.
8. A carbon-free gas engine EGR rate detection test bench for implementing the carbon-free gas engine EGR rate detection method of claim 1, comprising:
a carbon-free gas flow meter, an air flow meter and an air inlet side wide-area type oxygen sensor which are arranged on the side of entering the engine, and an air outlet side wide-area type oxygen sensor which is arranged on the side of the exhaust of the engine, wherein the carbon-free gas flow meter is used for detecting the mass flow of the carbon-free gas entering the side of the engine, the air flow meter is used for detecting the mass flow of the air entering the side of the engine, the air inlet side wide-area type oxygen sensor is used for detecting the oxygen mole fraction on the air inlet side, and the oxygen mole fraction on the exhaust side of the exhaust side wide-area type oxygen sensor is used for detecting the oxygen mole fraction on the exhaust side;
and the processor is in signal connection with the carbon-free gas flow meter, the air inlet side wide-area type oxygen sensor and the exhaust side wide-area type oxygen sensor and is used for determining the EGR rate according to the mass flow of the carbon-free gas entering the engine side, the mass flow of the air entering the engine side, the oxygen mole fraction at the air inlet side and the oxygen mole fraction at the exhaust side.
9. The carbon-free gas engine EGR rate detection test rig of claim 8, further comprising a carbon-free gas sensor for detecting a carbon-free gas concentration in engine exhaust gas disposed on an exhaust side of the engine and before an inlet of a circulation duct, and transmitting a detection signal to the processor.
10. The test bed for detecting the EGR rate of the carbon-free gas engine as recited in claim 9, further comprising a detection pipeline, wherein two ends of the detection pipeline are used for being connected with an exhaust pipeline of the engine, and the two ends are sequentially positioned in the flowing direction of exhaust gas of the exhaust pipeline, the carbon-free gas sensor is arranged on the detection pipeline, and a cooler is arranged between an upstream air inlet of the detection pipeline connected with the exhaust pipeline and the carbon-free gas sensor.
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