Hydrocarbon quality test method, methanol fuel automobile carbon canister emission test method

Abstract

The present application relates to the technical field of automobile emission detection, and particularly relates to a hydrocarbon mass testing method and a methanol fuel automobile carbon canister emission testing method. The present application connects the atmospheric port of the carbon canister to a micro closed chamber, continuously measures the total hydrocarbon in the closed chamber using FID, and synchronously measures the methanol concentration in the same gas using FTIR. Based on the measurement results of FID and FTIR, the signal separation of non-methanol hydrocarbons and methanol is realized, the problem that the FID response is inaccurate and the alcohol and hydrocarbon emissions cannot be distinguished in the prior art is solved, and the accuracy and reliability of the methanol fuel automobile evaporation pollutant emission testing are improved.

Description

Technical Field

[0001] This invention relates to the field of automotive emission testing technology, and in particular to a method for testing the quality of hydrocarbons and a method for testing emissions from the carbon canister of methanol fuel vehicles. Background Technology

[0002] As a clean alternative energy source, methanol fuel can be produced through various methods, including coal, natural gas, biomass, and even carbon dioxide hydrogenation, making it relatively inexpensive compared to gasoline. Secondly, methanol has a high octane rating and excellent anti-knock properties, allowing engines to use higher compression ratios, resulting in higher power performance for methanol-fueled vehicles. Furthermore, due to the oxygen-containing and sulfur-free nature of methanol molecules, its air-fuel ratio is low, leading to more complete combustion and reduced soot formation. Compared to traditional gasoline, methanol-fueled vehicles significantly reduce emissions of CO, HC, and PM particulate matter in their exhaust.

[0003] However, due to the volatility, corrosiveness, and toxicity of methanol fuel, it poses the following risks in terms of evaporative emissions: First, methanol itself is toxic, and its vapors are harmful to health; second, although pure methanol has a low vapor pressure, a mixture of methanol and gasoline may produce a high vapor pressure, increasing the risk of evaporative emissions; third, methanol is more permeable to sealing materials than gasoline, causing fuel vapors to escape through the materials themselves, forming unconventional evaporative emission pathways; fourth, compared to traditional gasoline fuel, methanol molecules are smaller and more polar, resulting in different adsorption and desorption characteristics on activated carbon. This may lead to a decrease in the adsorption efficiency of the activated carbon canister for methanol vapor, a reduction in its effective working capacity, and even difficulty in completely removing it during desorption, affecting its ability to operate continuously.

[0004] The goal of charcoal canister emission testing is to detect evaporative pollutants generated by the vehicle's fuel system and ultimately released into the external environment through the charcoal canister's vent during diurnal temperature variations. Methanol-fueled vehicles use fuels including methanol and gasoline (pure methanol-fueled vehicles contain only methanol fuel), and their charcoal canister emission pollutants mainly consist of hydrocarbon pollutants and methanol (pure methanol-fueled vehicles contain only methanol). Existing methods for measuring methanol pollutants in the vehicle's sealed compartments involve using a packed column sampling tube to collect the gas within the sealed compartment, followed by headspace gas chromatography-mass spectrometry (HGC-MS) to measure the methanol content. For example, patent document CN101986151A provides a method for testing the methanol content in evaporative pollutants from methanol vehicles. However, this method is not suitable for methanol charcoal canister emission testing based on a miniature sealed chamber for two reasons: First, the evaporative emission from the charcoal canister's vent is relatively low, requiring a miniature sealed chamber to improve testing accuracy; its volume is typically only 0.2 m³. 3 Up to 7.5 m 3However, when using packed columns or sampling tubes for sampling, continuous sampling at a flow rate of 300 mL / min to 500 mL / min is usually required for at least 4 minutes, and the sampled gas does not ultimately flow back into the micro-sealed chamber, which significantly affects the test accuracy. Secondly, in most cases, the micro-sealed chamber is located inside the vehicle's sealed compartment, and during daytime testing, both sealed chambers are simultaneously sealed, preventing test personnel from entering the vehicle's sealed compartment to sample the micro-sealed chamber. Furthermore, the collection method involves offline analysis using gas chromatography, making it impossible to obtain continuous methanol concentration values ​​within the micro-sealed chamber. Summary of the Invention

[0005] This invention aims to solve the above-mentioned problems by providing a convenient and highly accurate method for testing the quality of hydrocarbons and a method for testing the emissions from the carbon canisters of methanol fuel vehicles.

[0006] The technical solution to the problem of this invention is, firstly, to provide a method for testing the quality of hydrocarbons, comprising the following steps:

[0007] S1. Continuous measurement of the total hydrocarbon concentration in the test gas using a flame ionization detector. FID Simultaneously, the methanol concentration C in the gas to be tested was measured using a Fourier transform infrared spectrometer. MeOH ;

[0008] S2. Obtain the response coefficient η of the hydrogen flame ionization detector to methanol, and adjust the total hydrocarbon concentration C based on the response coefficient η. FID After correction, the equivalent concentration C of the non-methanol hydrocarbon components is obtained. HC = C FID - ηC MeOH ;

[0009] S3. According to C HC C MeOH Calculate the mass of the non-methanol hydrocarbon components and the mass of methanol; the sum of the two is the mass of the hydrocarbon.

[0010] This hydrocarbon can be pure methanol or a mixture of methanol and non-methanol hydrocarbons in any proportion. In this invention, based on FID and FTIR, the signals of non-methanol hydrocarbons and methanol are separated, solving the problem of inaccurate FID response to oxygen-containing organic compounds. This allows for the restoration of the true signals of non-methanol hydrocarbons, ultimately leading to a more accurate and reliable hydrocarbon quality result.

[0011] Based on this, the present invention also provides a method for testing emissions from the carbon canister of a methanol fuel vehicle, comprising the following steps:

[0012] (1) Connect the atmospheric port of the carbon canister to the micro-sealed chamber and obtain the initial hydrocarbon mass M of the micro-sealed chamber during the test period according to the method described above. 室内初始 And the final hydrocarbon mass M 室内最终 ;

[0013] (2) Emissions from the charcoal canister M = (M 室内最终 - M 室内初始 ) + (M 出 - M 入 ); where M 出 M represents the mass of hydrocarbons expelled from the miniature sealed chamber during the test. 入 The mass of hydrocarbons that entered the micro-sealed chamber during the test.

[0014] This methanol fuel can be used in pure methanol fuel vehicles or as a blend of methanol and non-methanol fuels in any proportion, such as a blend of methanol and gasoline in any proportion.

[0015] In step (1), the test gas emitted from the charcoal canister of a methanol fuel vehicle, as a preferred embodiment of the present invention, is based on C. HC When calculating the mass of non-methanol hydrocarbon components, the equivalent concentration C of the non-methanol hydrocarbon components is used. HC Corrected to standard conditions, and based on the preset hydrocarbon mass conversion coefficient and sampling volume, the mass of non-methanol hydrocarbons is calculated.

[0016] Preferably, the mass of the non-methanol hydrocarbon component = KVC HC P / T; where V is the net volume of the micro-sealed chamber, P is the atmospheric pressure at the time of sampling, T is the ambient temperature inside the micro-sealed chamber, K is 1.2 × (12 + H / C), and H / C is the average hydrogen-to-carbon ratio of non-methanol hydrocarbon components.

[0017] H / C is determined based on the composition of the gasoline; in some implementations, H / C = 2.33.

[0018] As a preferred embodiment of the present invention, the response coefficient η can be the recommended value of 0.63, or it can be obtained by actual measurement.

[0019] As a preferred embodiment of the present invention, according to C MeOH When calculating the mass of methanol, the methanol concentration C is used. MeOH Corrected to standard conditions, and the methanol mass is calculated based on the standard state density of methanol and the sampling volume.

[0020] Preferably, the corrected concentration of methanol = (T0 / T1) × (P1 / P0) × C MeOHWhere T0 and P0 are the pressure and temperature under standard conditions, T0 = 273.15 K, P0 = 101.325 kPa, and T1 and P1 are the ambient temperature and atmospheric pressure at the time of sampling in the micro-enclosed room.

[0021] Preferably, the mass of methanol = (32 / 22.4) × V × (T0 / T1) × (P1 / P0) × C MeOH Where 32 is the molar mass of methanol (g / mol), 22.4 is the molar volume of an ideal gas under standard conditions (L / mol), and V is the net volume of the micro-closed chamber.

[0022] In step (2), a macroscopic calculation framework is provided. The emission M from the carbon canister covers hydrocarbons inside the micro-closed chamber as well as hydrocarbons leaving the system, while eliminating hydrocarbons in the background air entering the system. This unifies the complex dynamic process within a conservation framework and improves the accuracy of the test results.

[0023] In some implementations, to simplify M 出 M 入 As a preferred embodiment of the present invention, the carbon canister, the miniature sealed chamber, the hydrogen flame ionization detector, and the Fourier transform infrared spectrometer are connected in sequence, and the gas analyzed by the Fourier transform infrared spectrometer is returned to the miniature sealed chamber.

[0024] In this embodiment, the gas in the miniature sealed chamber flows through the analyzer and then returns to the miniature sealed chamber, forming a closed loop. This maintains a constant total amount of gas in the chamber and improves the accuracy of long-term testing.

[0025] As a preferred embodiment of the present invention, the devices are connected by connecting pipes, the length of which does not exceed 5 m and the inner diameter does not exceed 8 mm, and their volume and length are as small as possible. The smaller diameter of the connecting pipes reduces backmixing and axial diffusion; the volume of the connecting pipes is much smaller than the volume of the micro-sealed chamber itself, ensuring the accuracy of V.

[0026] As a preferred embodiment of the present invention, the connecting pipe should be a low-permeability pipe.

[0027] As a preferred embodiment of the present invention, both the miniature sealing chamber and the connecting tube are heated or insulated to prevent methanol condensation from causing test errors and to reduce the adsorption and desorption of methanol on the tube wall.

[0028] Based on this closed loop, in some implementations, under ideal and approximate conditions, it can be assumed that: M 出 -M 入 = 0; thus simplifying the emission amount M from the charcoal canister to M = M 室内最终 - M 室内初始 .

[0029] In other implementations, since FID actually requires the sample to be introduced into a hydrogen flame for combustion to generate a signal, which consumes hydrocarbons, and clean air is added to maintain system pressure—and this added gas is purified zero-carbon air with negligible hydrocarbon content—M... 入 = 0. Therefore, the emission amount from the charcoal canister, M = M 室内最终 - M 室内初始 +M FID,loss M FID,loss = Q × ∫ρ(t)dt, where Q is the FID sampling flow rate and ρ(t) is the hydrocarbon mass concentration of the gas in the micro-sealed chamber at time t. The test calculation method is essentially the same as the hydrocarbon mass test method.

[0030] Furthermore, as a preferred embodiment of the present invention, a pretreatment step is included before step (1). The steps and order of the pretreatment vary depending on the regulations of different evaporation emission testing standards, but basically include the following steps:

[0031] Oil change: Add fuel to the tank at a certain proportion of its nominal volume. This process requires controlling the fuel temperature.

[0032] Immersion: The fuel system is placed in an immersion area at a specific ambient temperature and immersed for a specified period of time.

[0033] Carbon canister desorption: The vehicle is fixed on a chassis dynamometer with an environmental simulation chamber, and the carbon canister is desorbed according to the specified test conditions or an equivalent offline method is used.

[0034] Charcoal canister loading: Then, a mixture of gas containing butane is used to load the desorbed charcoal canister until the critical point is reached.

[0035] In a preferred embodiment of the present invention, the mixed gas is a mixture of butane and nitrogen in a volume ratio of 45% to 55%.

[0036] As a preferred embodiment of the present invention, during the loading process, the auxiliary carbon canister connected in series with the test carbon canister is continuously weighed; when the weight gain of the auxiliary carbon canister reaches a preset threshold, i.e., when the test carbon canister is determined to have reached a critical point, loading is stopped. By weighing the auxiliary carbon canister to capture the butane breakthrough, automated control of stopping upon breakthrough is achieved, ensuring that each carbon canister enters the subsequent emission test at the exact same saturation level, eliminating errors caused by different loading levels.

[0037] The beneficial effects of this invention are:

[0038] 1. This invention provides a method for testing the quality of hydrocarbons. Based on FID and FTIR, it achieves signal separation between non-methanol hydrocarbons and methanol, solves the problem of inaccurate response of FID to oxygen-containing organic compounds, and can restore the true signal of non-methanol hydrocarbons, thereby finally integrating to obtain a more realistic and accurate hydrocarbon quality result.

[0039] 2. This invention provides a method for testing the emissions from the carbon canister of a methanol-fueled vehicle based on a small-volume micro-sealed chamber. It utilizes the aforementioned hydrocarbon mass testing method, resulting in high testing accuracy and improving the accuracy and reliability of testing evaporative pollutant emissions from methanol-fueled vehicles. Detailed Implementation

[0040] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments.

[0041] A method for testing emissions from the carbon canister of a methanol-fueled vehicle includes the following steps:

[0042] Fuel system pretreatment: Oil change: Add fuel to the tank at a certain proportion of its nominal volume. The fuel temperature needs to be controlled during this process. Immersion: Place the fuel system in an immersion area at a specific ambient temperature and immerse it for the specified time. Carbon canister desorption: Fix the vehicle under test on a chassis dynamometer with an environmental simulation chamber and run it under the specified test conditions, or desorb the carbon canister using an equivalent method. Carbon canister loading: Use a mixture of butane and nitrogen at a volume ratio of 50% ± 5% and load the carbon canister at the specified butane flow rate. During this period, continuously weigh the auxiliary carbon canister. When the test carbon canister reaches the critical point, immediately shut off the butane and nitrogen gas supply.

[0043] Connection of the sampling pipeline for the carbon canister exhaust: Connect the atmospheric port of the carbon canister to the miniature sealed chamber using a low-permeability pipeline with a length not exceeding 5 m and an inner diameter not exceeding 8 mm. Connect the interior of the miniature sealed chamber to the FID using a sampling tube, also using a low-permeability pipeline with a length not exceeding 5 m and an inner diameter not exceeding 8 mm, and insulate the exterior of the miniature sealed chamber with heating or insulation. Connect the FDI outlet to the FTIR inlet using a low-permeability pipeline with a length not exceeding 5 m and an inner diameter not exceeding 8 mm, and insulate it with heating or insulation. Finally, the gas after FTIR analysis is introduced into the miniature sealed chamber through the reflux pipe.

[0044] Sampling and measurement during daytime testing: Before the test begins, the miniature sealed chamber is opened or the scavenging pump is run to purge the interior and pipelines until the background pollutants stabilize, and the zero point and distance point of FID and FTIR are calibrated. Subsequently, the day and night temperature cycle test procedure of the environmental chamber (or whole vehicle-level sealed chamber) and the carbon canister emission test procedure are run simultaneously.

[0045] Given the net volume V of a miniature sealed chamber, in meters. 3 T0 = ​​273.15 K, P0 = 101.325 kPa. In this embodiment, the response coefficient η is 0.63; K = 1.2 × (12 + H / C) = 1.2 × (12 + 2.33) = 17.196.

[0046] Initial measurement Within 10 minutes of closing and sealing the miniature sealed chamber, the temperature and pressure inside the miniature sealed chamber were measured and recorded as T. i P i The units are K and kPa, respectively; the initial hydrocarbon pollutant concentration at FID is denoted as C. FID,i The unit is ppm (volume) C1 equivalent; the methanol concentration at the initial FTIR moment is denoted as C. MeOH,i The unit is ppm (volume) C1 equivalent.

[0047] Therefore, we can calculate:

[0048] The mass of methanol at the initial moment ;

[0049] The equivalent concentration C of non-methanol hydrocarbon components at the initial time HC,i = C FID,i - ηC MeOH,i ,

[0050] The mass of non-methanol hydrocarbon components at the initial time .

[0051] Measurement after 24 hours Before the test program reaches 24h ± 6min, the zero point and distance point of FID and FTIR are calibrated, and then the temperature T in the miniature sealed chamber is measured. 24 Pressure P 24 And the concentrations of hydrocarbons and methanol in the micro-closed chamber, C FID,24 C MeOH,24 .

[0052] Therefore, we can calculate:

[0053] The mass of methanol after 24 hours ;

[0054] The equivalent concentration C of non-methanol hydrocarbon components after one day HC,24 = C FID,24 -ηC MeOH,24 ,

[0055] Mass of non-methanol hydrocarbon components after 24 hours .

[0056] Therefore, the first day's emissions from the charcoal canister

[0057] .

[0058] Among them, M 出 M represents the mass of hydrocarbons expelled from the miniature sealed chamber during the test. 入 To determine the mass of hydrocarbons entering the micro-sealed chamber during the test, M in this embodiment... 出 - M 入 It can be considered as 0.

[0059] Measurements taken two days and nights later Similarly, before the test program reaches 48h ± 6min, the zero point and distance point of FID and FTIR are calibrated, and then the temperature T in the miniature sealed chamber is measured. 48 Pressure P 48 And the concentrations of hydrocarbons and methanol in the micro-closed chamber, C FID,48 C MeOH,48 .

[0060] The second day's emissions from the charcoal canister

[0061] .

[0062] Among them, M 出 M represents the mass of hydrocarbons expelled from the miniature sealed chamber during the test. 入 To determine the mass of hydrocarbons entering the micro-sealed chamber during the test, M in this embodiment... 出 - M 入 It can be considered as 0.

[0063] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for testing the quality of hydrocarbons, characterized in that: Includes the following steps: S1. Continuous measurement of the total hydrocarbon concentration in the test gas using a flame ionization detector. FID Simultaneously, the methanol concentration C in the gas to be tested was measured using a Fourier transform infrared spectrometer. MeOH ; S2. Obtain the response coefficient η of the hydrogen flame ionization detector to methanol, and adjust the total hydrocarbon concentration C based on the response coefficient η. FID After correction, the equivalent concentration C of the non-methanol hydrocarbon components is obtained. HC = C FID - ηC MeOH ; S3. According to C HC C MeOH Calculate the mass of the non-methanol hydrocarbon components and the mass of methanol, and sum them as the mass of the hydrocarbon.

2. A method for testing emissions from the charcoal canister of a methanol fuel vehicle, characterized in that: Includes the following steps: (1) Connect the atmospheric port of the carbon canister to the micro-sealed chamber, and obtain the initial hydrocarbon mass M of the micro-sealed chamber during the test according to the method of claim 1. 室内初始 And the final hydrocarbon mass M 室内最终 ; (2) Emissions from the charcoal canister M = (M 室内最终 - M 室内初始 ) + (M 出 - M 入 ); where M 出 M represents the mass of hydrocarbons expelled from the miniature sealed chamber during the test. 入 The mass of hydrocarbons that entered the micro-sealed chamber during the test.

3. The method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 2, characterized in that: The carbon canister, the miniature sealed chamber, the hydrogen flame ionization detector, and the Fourier transform infrared spectrometer are connected in sequence, and the gas analyzed by the Fourier transform infrared spectrometer is returned to the miniature sealed chamber.

4. The method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 3, characterized in that: M 出 -M 入 = 0。 5. A method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 2, 3, or 4, characterized in that: Mass of non-methanol hydrocarbon components = KVC HC P / T; where V is the net volume of the micro-sealed chamber, P is the atmospheric pressure at the time of sampling, T is the ambient temperature inside the micro-sealed chamber, K is 1.2 × (12 + H / C), and H / C is the average hydrogen-to-carbon ratio of the non-methanol hydrocarbon components.

6. A method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 2, 3, or 4, characterized in that: The methanol concentration C MeOH Corrected to standard conditions, and the methanol mass is calculated based on the standard state density of methanol and the sampling volume.

7. A method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 2, 3, or 4, characterized in that: Before step (1), a pretreatment step is also included: after changing the oil and immersing the vehicle, the vehicle is fixed on a chassis dynamometer with an environmental simulation chamber, and the carbon canister is desorbed according to the specified test conditions or an equivalent offline method is used; then a mixture of gas containing butane is used to load the desorbed carbon canister until the critical point is reached.

8. A method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 7, characterized in that: The mixed gas is a mixture of butane and nitrogen with a volume ratio of 45% to 55%.

9. A method for testing emissions from a methanol fuel vehicle's charcoal canister according to claim 2 or 3, characterized in that: The equipment is connected by a connecting pipe, the length of which does not exceed 5 m and the inner diameter does not exceed 8 mm.

10. The method for testing emissions from the carbon canister of a methanol fuel vehicle according to claim 9, characterized in that: Both the miniature sealing chamber and the connecting pipe are heated or insulated.