A method and test bench for EGR rate testing of carbon-free gas engines

Abstract

This invention relates to the field of engine exhaust gas recirculation control technology, specifically to a method and test bench for detecting the EGR rate of a carbon-free gas engine. The method includes the following steps: determining the air-fuel equivalence ratio based on the mass flow rate of the carbon-free gas entering the engine and the mass flow rate of air; determining the exhaust gas molecular mass of the EGR cycle based on the air-fuel equivalence ratio; determining the oxygen fraction error based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side; determining the EGR cycle mass flow rate based on the oxygen fraction error, the exhaust gas molecular mass, the air molecular mass, and the intake air mass flow rate; and determining the EGR rate based on the EGR cycle mass flow rate, the mass flow rate of the carbon-free gas entering the engine, and the air mass flow rate. This method solves the problems in existing technologies where carbon-free gas engines do not contain carbon, making it impossible to use CO2 sensors to measure the EGR rate, and where the accuracy of EGR rate measurement is affected by gas pulse measurement when using a venturi tube detection method.

Description

Technical Field

[0001] This invention relates to the field of engine exhaust gas recirculation control technology, specifically to a method and test bench for detecting the EGR rate of a carbon-free gas engine. Background Technology

[0002] EGR rate is defined as the ratio of the amount of recirculated exhaust gas to the total amount of intake air drawn into the cylinder. Reasonable control of EGR rate is extremely important for the purification effect of nitrogen oxides and the overall engine emissions. When conducting calibration tests, a method is needed to quantify EGR rate in order to evaluate the impact of exhaust gas recirculation on engine performance.

[0003] Current methods for detecting EGR rate in engines are based on traditional carbon-containing fossil fuel engines. Therefore, EGR rate can be measured by detecting CO2 concentrations in the intake and exhaust manifolds. Since carbon-free gas engines do not contain carbon, CO2 sensors cannot be used to measure EGR rate. Another method uses a venturi tube to detect upstream pressure to achieve EGR rate detection. However, with the venturi tube method, gas pulses will affect the accuracy of the EGR rate measurement. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method and test bench for detecting the EGR rate of a carbon-free gas engine. This method solves the problems in existing technologies where carbon-free gas engines do not contain carbon, making it impossible to use CO2 sensors to measure the EGR rate, and where gas pulses affect the accuracy of EGR rate measurement when using a venturi tube detection method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for detecting the EGR rate of a carbon-free gas engine, comprising the following steps:

[0007] The air-fuel equivalence ratio is determined based on the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side.

[0008] Determine the molecular mass of the exhaust gas in the EGR cycle based on the air-fuel equivalence ratio;

[0009] The oxygen fraction error is determined based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side.

[0010] The EGR cycle mass flow rate is determined based on the oxygen fraction error, exhaust gas molecular mass, air molecular mass, and intake air mass flow rate.

[0011] The EGR rate is determined based on the EGR cycle mass flow rate, the carbon-free fuel gas mass flow rate entering the engine side, and the air mass flow rate.

[0012] In some alternative solutions, determining the air-fuel equivalence ratio based on the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side includes:

[0013] Obtain the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side;

[0014] According to the formula Determine the air-fuel equivalence ratio λ;

[0015] in, The mass flow rate of air entering the engine side. α represents the mass flow rate of carbon-free fuel gas entering the engine side, and α is the air-fuel coefficient.

[0016] In some alternative solutions, determining the exhaust gas molecular mass of the EGR cycle based on the air-fuel equivalence ratio includes:

[0017] According to the formula Determine the exhaust gas molecular weight (MW) of the EGR cycle EGR ;

[0018] Where a1, a2, b1, b2, c1, c2, d1, and d2 are calibration fitting coefficients.

[0019] In some alternative solutions, determining the oxygen fraction error based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side includes:

[0020] Obtain the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side;

[0021] According to the formula Determining the oxygen fraction error

[0022] in, This refers to the mole fraction of oxygen on the intake side. This represents the mole fraction of oxygen on the exhaust side. This represents the mole fraction of oxygen in the air.

[0023] In some alternative solutions, before obtaining the oxygen mole fraction on the exhaust side, the concentration of carbon-free fuel gas in the engine exhaust is also detected, and the detection signal is transmitted to the processor. When the concentration of carbon-free fuel gas is greater than a set concentration value, the detection of the oxygen mole fraction on the exhaust side is stopped.

[0024] In some alternative solutions, determining the EGR cycle mass flow rate based on oxygen fraction error, exhaust gas molecular mass, air molecular mass, and the mass flow rate of air entering the engine side includes:

[0025] According to the formula Determine the EGR cycle mass flow rate

[0026] in, For the mass flow rate of air entering the engine side, MW air For the molecular mass of air, MW EGR This refers to the molecular weight of the exhaust gas in the EGR cycle.

[0027] In some alternative solutions, determining the EGR rate based on the EGR cycle mass flow rate, the carbon-free fuel gas mass flow rate entering the engine side, and the air mass flow rate includes:

[0028] According to the formula Determine the EGR rate.

[0029] in, The mass flow rate of air entering the engine side. For the mass flow rate of carbon-free fuel gas entering the engine side, This refers to the EGR circulating mass flow rate.

[0030] On the other hand, the present invention also provides a test bench for EGR rate testing of carbon-free gas engines, for implementing the carbon-free gas engine EGR rate testing method described above, comprising:

[0031] The system includes a carbon-free fuel flow meter, an air flow meter, and an intake-side wide-range oxygen sensor installed on the engine side, and an exhaust-side wide-range oxygen sensor installed on the engine exhaust side. The carbon-free fuel flow meter is used to detect the mass flow rate of carbon-free fuel entering the engine side, the air flow meter detects the mass flow rate of air entering the engine side, the intake-side wide-range oxygen sensor is used to detect the oxygen mole fraction on the intake side, and the exhaust-side wide-range oxygen sensor detects the oxygen mole fraction on the exhaust side.

[0032] The processor, which is connected to the carbon-free fuel flow meter, air flow meter, intake-side wide-range oxygen sensor and exhaust-side wide-range oxygen sensor, is used to determine the EGR rate based on the detected carbon-free fuel mass flow rate entering the engine side, air mass flow rate entering the engine side, intake-side oxygen mole fraction and exhaust-side oxygen mole fraction.

[0033] In some alternative configurations, the carbon-free gas engine EGR rate testing bench also includes a carbon-free gas sensor, which is installed on the exhaust side of the engine and located before the recirculation pipe inlet to detect the concentration of carbon-free gas in the engine exhaust and transmit the detection signal to the processor.

[0034] In some alternative solutions, the carbon-free gas engine EGR rate testing bench also includes a testing pipe, the two ends of which are connected to the exhaust pipe of the engine, and the two ends are located sequentially in the exhaust flow direction of the exhaust pipe. The carbon-free gas sensor is disposed on the testing pipe, and a cooler is provided between the upstream air intake of the testing pipe connected to the exhaust pipe and the carbon-free gas sensor.

[0035] Compared with existing technologies, the advantages of this invention are as follows: This method determines the air-fuel equivalence ratio based on the mass flow rate of carbon-free fuel gas entering the engine side and the mass flow rate of air; it determines the exhaust gas molecular mass of the EGR cycle based on the air-fuel equivalence ratio; it determines the oxygen fraction error based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side; it determines the EGR cycle mass flow rate based on the oxygen fraction error, the exhaust gas molecular mass, the air molecular mass, and the intake air mass flow rate; and it determines the EGR rate based on the EGR cycle mass flow rate, the mass flow rate of carbon-free fuel gas entering the engine side, and the air mass flow rate. Using this method, the EGR rate of engines using carbon-free fuel gas can be measured. Furthermore, it eliminates the need for a venturi tube for detection, thus resulting in relatively accurate test results.

[0036] Additionally, in some alternative solutions, a carbon-free fuel gas sensor is installed on the engine's exhaust pipe to monitor the carbon-free fuel gas content in the exhaust pipe in real time. Only when the carbon-free fuel gas content in the exhaust pipe falls below a set concentration value within a certain time period will the intake-side wide-range oxygen sensor in the intake pipe and the exhaust-side wide-range oxygen sensor in the exhaust pipe be activated. If the carbon-free fuel gas concentration exceeds the set concentration value, the detection of the oxygen mole fraction on the exhaust side will be stopped to prevent the carbon-free fuel gas from detonating in the exhaust pipe and causing a safety accident.

[0037] A detection pipe leads out a path of exhaust gas from the exhaust pipe, allowing the combusted exhaust gas to pass through it. A cooler is installed between the upstream air intake and the carbon-free gas sensor, connecting the detection pipe to the exhaust pipe. This cools the exhaust gas, allowing the carbon-free gas sensor on the detection pipe to detect it. For example, currently, the highest operating temperature of hydrogen sensors on the market is below 90°C. Therefore, the exhaust gas is cooled to below 90°C by the cooler before the hydrogen sensor measures the hydrogen concentration in the exhaust gas. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart of the EGR rate detection method for a carbon-free gas engine in an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the structure of the EGR rate testing bench for a carbon-free gas engine in an embodiment of the present invention.

[0041] In the diagram: 1. Engine; 11. Spark plug; 2. Intake manifold; 21. Throttle valve; 22. Intake-side wide-range oxygen sensor; 23a. Hydrogen injector; 23b. Hydrogen direct injection injector; 23c. Ammonia injector; 24. Mixer; 3. Exhaust manifold; 31. Exhaust-side wide-range oxygen sensor; 32. Carbon-free fuel sensor; 33. Detection pipe; 34. Cooler; 4. Circulation pipe; 41. EGR cooler; 42. EGR valve; 43. EGR check valve; 5. Processor. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] Figure 1 This is a flowchart of the EGR rate detection method for a carbon-free gas engine in an embodiment of the present invention, as shown below. Figure 1 As shown, this invention provides a method for detecting the EGR rate of a carbon-free gas engine, comprising the following steps:

[0045] S1: Determine the air-fuel equivalence ratio based on the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side.

[0046] In some optional embodiments, step S1 includes:

[0047] S11: Obtain the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side.

[0048] In this example, the mass flow rates of carbon-free fuel gas and air entering the engine are obtained by installing a carbon-free fuel gas mass flow meter and an air mass flow meter on the side where the fuel gas enters the engine, respectively. In this example, the test is conducted on a test bench, allowing the mass flow rates of carbon-free fuel gas and air entering the engine to be obtained from the gas source.

[0049] S12: According to the formula Determine the air-fuel equivalence ratio λ, where, This refers to the air mass flow rate on the intake side. The mass flow rate of carbon-free fuel gas entering the engine side is α, which is the air-fuel ratio, i.e., the ratio of the stoichiometric air-fuel ratio to the theoretical amount (mass) of air required for the complete combustion of 1 kg of fuel.

[0050] In this example, the carbon-free fuel is hydrogen, and the air-fuel ratio α is 34.2. When other fuels are used, such as hydrogen-ammonia fuel, the air-fuel ratio α can be adjusted accordingly.

[0051] S2: Determine the molecular mass of the exhaust gas in the EGR cycle based on the air-fuel equivalence ratio.

[0052] In some optional embodiments, step S2 includes:

[0053] According to the formula Determine the exhaust gas molecular weight (MW) of the EGR cycle EGR ;

[0054] Where a1, a2, b1, b2, c1, c2, d1, and d2 are calibration fitting coefficients.

[0055] In this example, the carbon-free fuel gas is hydrogen, a1 = 5.12, a2 ​​= 0.15, b1 = 177.41, b2 = 37.12, c1 = 0.26, c2 = 0.21, d1 = 12.53, d2 = 6.63.

[0056] Right now When λ≥1, adopt Calculate, when λ < 1, use calculate.

[0057] When other types of fuel are used instead of carbon-free fuel, a1, a2, b1, b2, c1, c2, d1, and d2 are recalibrated.

[0058] S3: Determine the oxygen fraction error based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side.

[0059] In some optional embodiments, step S3 includes:

[0060] S31: Obtain the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side.

[0061] In this example, an intake-side wide-range oxygen sensor is installed on the engine side, and an exhaust-side wide-range oxygen sensor is installed on the engine exhaust side. The intake-side wide-range oxygen sensor is used to detect the oxygen mole fraction on the intake side, and the exhaust-side wide-range oxygen sensor is used to detect the oxygen mole fraction on the exhaust side.

[0062] S32: According to the formula Determining the oxygen fraction error in, This refers to the mole fraction of oxygen on the intake side. This represents the mole fraction of oxygen on the exhaust side. This represents the mole fraction of oxygen in the air.

[0063] In this example, the oxygen mole fraction in the air is taken as 0.209; of course, in actual use, the oxygen mole fraction in the air can be re-determined according to the altitude.

[0064] In addition, in some optional embodiments, before obtaining the oxygen mole fraction on the exhaust side, the concentration of carbon-free fuel gas in the engine exhaust is also detected, and the detection signal is transmitted to the processor. When the concentration of carbon-free fuel gas is greater than a set concentration value, the detection of the oxygen mole fraction on the exhaust side is stopped.

[0065] Because wide-range oxygen sensors heat the sensor's front probe to over 600°C upon startup, a high concentration of carbon-free fuel gas in the exhaust may ignite it. Therefore, it's necessary to monitor the concentration of carbon-free fuel gas in the engine exhaust. If the concentration exceeds a set value, the oxygen mole fraction measurement on the exhaust side should be stopped to prevent deflagration of carbon-free fuel gas in the exhaust pipe, which could lead to a safety accident.

[0066] In this example, the carbon-free fuel is hydrogen. Because the hydrogen engine uses a lean-burn combustion mode, the content of unburned hydrogen in the exhaust pipe is relatively high. Hydrogen has a very wide ignition limit. Therefore, it is necessary to control the EGR rate during testing to prevent the combustion of unburned hydrogen in the exhaust pipe and avoid an explosion.

[0067] S4: Determine the EGR cycle mass flow rate based on the oxygen fraction error, exhaust gas molecular mass, air molecular mass, and intake air mass flow rate.

[0068] In some optional embodiments, step S4 includes:

[0069] According to the formula Determine the EGR cycle mass flow rate in, For intake-side air mass flow rate, MW air For the molecular mass of air, MW EGR This refers to the molecular weight of the exhaust gas in the EGR cycle.

[0070] S5: Determine the EGR rate based on the EGR cycle mass flow rate, the carbon-free fuel gas mass flow rate entering the engine side, and the air mass flow rate.

[0071] In some optional embodiments, step S5 includes:

[0072] According to the formula Determine the EGR rate, where, This refers to the intake-side air mass flow rate. For the mass flow rate of carbon-free fuel gas entering the engine side, This refers to the EGR circulating mass flow rate.

[0073] The proposed EGR rate detection method for carbon-free gas engines determines the air-fuel equivalence ratio based on the mass flow rate of carbon-free gas and air entering the engine. Based on the air-fuel equivalence ratio, the exhaust gas molecular mass of the EGR cycle is determined. The oxygen fraction error is determined based on the oxygen mole fraction on the intake and exhaust sides. The EGR cycle mass flow rate is determined based on the oxygen fraction error, exhaust gas molecular mass, air molecular mass, and intake air mass flow rate. Finally, the EGR rate is determined based on the EGR cycle mass flow rate, the mass flow rate of carbon-free gas entering the engine, and the air mass flow rate. This method can measure the EGR rate of engines using carbon-free gas as fuel. It also eliminates the need for a venturi tube, resulting in relatively accurate test results.

[0074] Figure 2 This is a schematic diagram of the structure of the EGR rate testing bench for a carbon-free gas engine in an embodiment of the present invention, as shown below. Figure 2 As shown, in hydrogen or ammonia-hydrogen engines (where ammonia is injected into the mixer in the intake manifold), using exhaust gas recirculation (EGR) can effectively reduce NOx production by lowering the in-cylinder combustion temperature and increasing the power output of the hydrogen / ammonia-hydrogen engine. During the performance development of hydrogen / ammonia-hydrogen engines, the opening of the EGR valve is accurately calibrated based on the EGR rate under different engine loads. Therefore, accurate measurement of the EGR rate is crucial in the development of hydrogen / ammonia-hydrogen engines.

[0075] A typical test bench includes an engine 1, an intake manifold 2, an exhaust manifold 3, and an EGR circulation manifold 4; wherein, the circulation manifold 4 is equipped with an EGR cooler 41, an EGR valve 42, and an EGR check valve 43 in sequence from the connection with the exhaust manifold 3 to the connection with the intake manifold 2; the intake manifold 2 is equipped with a throttle valve 21 and a carbon-free gas injector.

[0076] On the other hand, the present invention provides a test bench for EGR rate testing of carbon-free gas engines, used to implement the above-mentioned EGR rate testing method for carbon-free gas engines, including:

[0077] The system includes a carbon-free fuel flow meter, an air flow meter, and an intake-side wide-range oxygen sensor installed on the engine's inlet side, and an exhaust-side wide-range oxygen sensor installed on the engine's exhaust side. The carbon-free fuel flow meter is used to detect the mass flow rate of carbon-free fuel entering the engine side, the air flow meter detects the mass flow rate of air entering the engine side, the intake-side wide-range oxygen sensor detects the oxygen mole fraction on the intake side, and the exhaust-side wide-range oxygen sensor detects the oxygen mole fraction on the exhaust side.

[0078] The processor, which is connected to the carbon-free fuel flow meter, air flow meter, intake-side wide-range oxygen sensor and exhaust-side wide-range oxygen sensor, is used to determine the EGR rate based on the detected carbon-free fuel mass flow rate entering the engine side, intake-side air mass flow rate, intake-side oxygen mole fraction and exhaust-side oxygen mole fraction.

[0079] The carbon-free gas engine EGR rate testing bench using this solution connects processor 5 to the carbon-free gas flow meter, air flow meter, intake-side wide-range oxygen sensor, and exhaust-side wide-range oxygen sensor. It acquires and detects the carbon-free gas mass flow rate entering the engine side, the intake-side air mass flow rate, the intake-side oxygen mole fraction, and the exhaust-side oxygen mole fraction. Based on the carbon-free gas mass flow rate and air mass flow rate on the engine side, the air-fuel equivalence ratio is determined; based on the air-fuel equivalence ratio, the exhaust gas molecular mass of the EGR cycle is determined; based on the intake-side oxygen mole fraction and the exhaust-side oxygen mole fraction, the oxygen fraction error is determined; based on the oxygen fraction error, the exhaust gas molecular mass, the air molecular mass, and the intake-side air mass flow rate, the EGR cycle mass flow rate is determined; and based on the EGR cycle mass flow rate, the carbon-free gas mass flow rate entering the engine side, and the air mass flow rate, the EGR rate is determined. This test bench can measure the EGR rate of engines using carbon-free gas as fuel.

[0080] In this example, the engine 1 is equipped with a spark plug 11, the intake side wide-range oxygen sensor 22 is installed on the intake pipe 2 between the connection between the circulation pipe and the intake pipe 2 and the carbon-free gas injector, and the exhaust side wide-range oxygen sensor 31 is installed on the exhaust pipe 3 between the connection between the circulation pipe 4 and the exhaust pipe 3 and the engine 1.

[0081] When engine 1 is a hydrogen direct injection engine, a hydrogen direct injection injector 23b is provided on the hydrogen engine; when engine 1 is a hydrogen intake port injection engine, a hydrogen injector 23a is provided on the intake pipe 2, which is located on the intake pipe 2 between the mixer 24 and engine 1; when engine 1 is an ammonia-hydrogen engine, a mixer 24 is provided on the intake pipe 2 between the intake side wide-range oxygen sensor 22 and engine 1, and an ammonia injector 23c is provided on the mixer 24.

[0082] In some optional embodiments, the carbon-free gas engine EGR rate testing bench also includes a carbon-free gas sensor, which is set on the exhaust side of the engine and located before the inlet of the recirculation pipe to detect the concentration of carbon-free gas in the engine exhaust and transmit the detection signal to the processor.

[0083] In this example, the carbon-free gas sensor 32 is installed on the exhaust side, and the wide-range oxygen sensor 31 is installed on the exhaust pipe 3 between the engine 1 and the exhaust pipe. Because the wide-range oxygen sensor heats its front probe to over 600°C when starting measurement, a high concentration of carbon-free gas in the exhaust may cause it to ignite. Therefore, the carbon-free gas sensor 32 is installed on the exhaust pipe 3 to detect the concentration of carbon-free gas in the engine exhaust. If the concentration of carbon-free gas exceeds a set value, the detection of the oxygen mole fraction on the exhaust side is stopped to prevent deflagration of carbon-free gas in the exhaust pipe and avoid a safety accident.

[0084] In some optional embodiments, the carbon-free gas engine EGR rate testing test bench further includes a testing pipe, the two ends of which are used to connect to the exhaust pipe of the engine, and the two ends are sequentially located in the exhaust flow direction of the exhaust pipe. The carbon-free gas sensor is disposed on the testing pipe, and a cooler is provided between the upstream air inlet of the testing pipe connected to the exhaust pipe and the carbon-free gas sensor.

[0085] In this embodiment, the two ends of the detection pipe 33 are connected to the exhaust pipe 3 of the engine 1, and the two ends are sequentially located in the exhaust flow direction of the exhaust pipe 3. This allows the exhaust gas after engine combustion to pass through the detection pipe, enabling the carbon-free gas sensor 32 installed on the detection pipe to detect the concentration of carbon-free gas in the exhaust gas discharged by the engine 1. Furthermore, conventional carbon-free gas sensors cannot operate in high-temperature environments. However, due to the high temperature of the exhaust gas after engine combustion, the carbon-free gas sensor cannot directly measure the concentration of carbon-free gas in the exhaust gas. In this solution, the detection pipe 33 is installed in parallel with the exhaust pipe 3 in the exhaust flow direction, allowing the exhaust gas after combustion to pass through the detection pipe 33. A cooler 34 is installed between the upstream air inlet of the detection pipe and the exhaust pipe and the carbon-free gas sensor, which cools the exhaust gas after engine combustion, allowing the carbon-free gas sensor on the detection pipe 33 to detect the cooled exhaust gas.

[0086] In summary, the processor connects to the carbon-free fuel flow meter, air flow meter, intake-side wide-range oxygen sensor, and exhaust-side wide-range oxygen sensor to acquire the detected carbon-free fuel mass flow rate, intake-side air mass flow rate, intake-side oxygen mole fraction, and exhaust-side oxygen mole fraction on the intake engine side. Based on the carbon-free fuel mass flow rate and air mass flow rate on the intake engine side, the air-fuel equivalence ratio is determined; based on the air-fuel equivalence ratio, the exhaust gas molecular mass of the EGR cycle is determined; based on the intake-side oxygen mole fraction and exhaust-side oxygen mole fraction, the oxygen fraction error is determined; based on the oxygen fraction error, exhaust gas molecular mass, air molecular mass, and intake-side air mass flow rate, the EGR cycle mass flow rate is determined; and based on the EGR cycle mass flow rate, the carbon-free fuel mass flow rate on the intake engine side, and the air mass flow rate, the EGR rate is determined. Using the test bench of this scheme, the EGR rate of engines using carbon-free fuel can be measured. It also eliminates the need for venturi tube testing, thus resulting in relatively accurate test results.

[0087] A carbon-free fuel gas sensor 32 is installed on the engine's exhaust pipe to monitor the carbon-free fuel gas content in the exhaust pipe in real time. Only when the carbon-free fuel gas content in the exhaust pipe is less than a set volume ratio within a certain time period will the intake-side wide-range oxygen sensor 22 in the intake pipe 2 and the exhaust-side wide-range oxygen sensor 31 in the exhaust pipe 3 be activated. If the carbon-free fuel gas concentration exceeds a set concentration value, the detection of the oxygen mole fraction on the exhaust side will be stopped to prevent the carbon-free fuel gas from undergoing detonation in the exhaust pipe and causing a safety accident.

[0088] A path of exhaust gas is drawn out from the exhaust pipe 3 via a detection pipe 33. The exhaust gas after combustion passes through the detection pipe 33, and a cooler 34 is installed between the upstream air intake of the detection pipe 33 and the carbon-free gas sensor 32. This cools the exhaust gas after combustion, allowing the carbon-free gas sensor on the detection pipe 33 to detect the cooled exhaust gas. For example, the highest operating temperature of currently available hydrogen sensors is below 90°C. Therefore, the exhaust gas is cooled to below 90°C by the cooler before the hydrogen concentration in the exhaust gas is measured by the hydrogen sensor. Furthermore, this solution can be used in engines with zero-carbon hybrid fuels, such as hydrogen engines or ammonia-hydrogen hybrid fuel engines.

[0089] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0090] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0091] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for detecting the EGR rate of a carbon-free gas engine, characterized in that, Includes the following steps: The air-fuel equivalence ratio is determined based on the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side. Determine the molecular mass of the exhaust gas in the EGR cycle based on the air-fuel equivalence ratio; The oxygen fraction error is determined based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side. The EGR cycle mass flow rate is determined based on the oxygen fraction error, exhaust gas molecular mass, air molecular mass, and intake air mass flow rate. The EGR rate is determined based on the EGR cycle mass flow rate, the carbon-free fuel gas mass flow rate entering the engine side, and the air mass flow rate. The determination of the exhaust gas molecular mass of the EGR cycle based on the air-fuel equivalence ratio includes: According to the formula Determine the molecular weight of the exhaust gas in the EGR cycle. ; in, , , , , , , and These are the calibration fitting coefficients; The determination of oxygen fraction error based on the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side includes: Obtain the oxygen mole fraction on the intake side and the oxygen mole fraction on the exhaust side; According to the formula Determine the oxygen fraction error ; in, This refers to the mole fraction of oxygen on the intake side. This represents the mole fraction of oxygen on the exhaust side. This represents the mole fraction of oxygen in the air.

2. The EGR rate detection method for a carbon-free gas engine as described in claim 1, characterized in that, The determination of the air-fuel equivalence ratio based on the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side includes: Obtain the mass flow rate of carbon-free fuel gas and the mass flow rate of air entering the engine side; According to the formula Determine the air-fuel equivalence ratio ; in, The mass flow rate of air entering the engine side. For the mass flow rate of carbon-free fuel gas entering the engine side, This is the air-fuel ratio.

3. The EGR rate detection method for a carbon-free gas engine as described in claim 1, characterized in that, Before obtaining the oxygen mole fraction on the exhaust side, the concentration of carbon-free fuel gas in the engine exhaust is also detected, and the detection signal is transmitted to the processor. When the concentration of carbon-free fuel gas is greater than the set concentration value, the detection of the oxygen mole fraction on the exhaust side is stopped.

4. The EGR rate detection method for a carbon-free gas engine as described in claim 1, characterized in that, The determination of EGR cycle mass flow rate based on oxygen fraction error, exhaust gas molecular mass, air molecular mass, and intake air mass flow rate includes: According to the formula Determine the EGR cycle mass flow rate ; in, This refers to the intake-side air mass flow rate. The mass of an air molecule. This refers to the molecular weight of the exhaust gas in the EGR cycle.

5. The EGR rate detection method for a carbon-free gas engine as described in claim 1, characterized in that, The determination of the EGR rate based on the EGR cycle mass flow rate, the carbon-free fuel gas mass flow rate on the engine side, and the air mass flow rate includes: According to the formula Determine the EGR rate. in, This refers to the intake-side air mass flow rate. For the mass flow rate of carbon-free fuel gas entering the engine side, This refers to the EGR circulating mass flow rate.

6. A test bench for testing the EGR rate of a carbon-free gas engine, characterized in that, The method for implementing the EGR rate detection method for a carbon-free gas engine as described in claim 1 includes: The system includes a carbon-free fuel flow meter, an air flow meter, and an intake-side wide-range oxygen sensor installed on the engine side, and an exhaust-side wide-range oxygen sensor installed on the engine exhaust side. The carbon-free fuel flow meter is used to detect the mass flow rate of carbon-free fuel entering the engine side, the air flow meter detects the mass flow rate of air entering the engine side, the intake-side wide-range oxygen sensor is used to detect the oxygen mole fraction on the intake side, and the exhaust-side wide-range oxygen sensor detects the oxygen mole fraction on the exhaust side. The processor, which is connected to the carbon-free fuel flow meter, air flow meter, intake-side wide-range oxygen sensor and exhaust-side wide-range oxygen sensor, is used to determine the EGR rate based on the detected carbon-free fuel mass flow rate entering the engine side, air mass flow rate entering the engine side, intake-side oxygen mole fraction and exhaust-side oxygen mole fraction.

7. The carbon-free gas engine EGR rate testing bench as described in claim 6, characterized in that, It also includes a carbon-free gas sensor, which is installed on the exhaust side of the engine and located before the inlet of the recirculation pipe to detect the concentration of carbon-free gas in the engine exhaust and transmit the detection signal to the processor.

8. The carbon-free gas engine EGR rate testing bench as described in claim 7, characterized in that, It also includes a detection pipe, the two ends of which are used to connect to the exhaust pipe of the engine, and the two ends are located sequentially in the direction of exhaust flow of the exhaust pipe. The carbon-free gas sensor is disposed on the detection pipe, and a cooler is provided between the upstream air inlet of the detection pipe and the exhaust pipe and the carbon-free gas sensor.

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