Heavy-duty vehicle braking wear particulate matter emission testing method
By constructing a multi-scenario, multi-load test method for particulate matter emissions from brake wear of heavy-duty vehicles, the applicability problem of existing test methods has been solved, enabling accurate assessment and scientific testing of emission levels of heavy-duty vehicles, and supporting regulatory formulation and technological research and development.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CATARC AUTOMOTIVE TEST CENT TIANJIN CO LTD
- Filing Date
- 2026-01-06
- Publication Date
- 2026-04-28
AI Technical Summary
Existing testing methods for particulate matter emissions from brake wear in light-duty vehicles are not suitable for the diverse scenarios and load characteristics of heavy-duty vehicles, resulting in test results that deviate significantly from reality and fail to accurately assess the true emission levels of heavy-duty vehicles.
Multiple emission test cycles covering different typical operating scenarios were constructed, and tests were conducted under various load conditions, including no-load, half-load, and full-load. Braking characteristic parameters were analyzed using high-precision sensor data, and a dedicated braking emission test system for heavy-duty vehicles was built to calculate particulate matter mass and quantity emission factors, ensuring the accuracy and representativeness of the test results.
It provides a true reflection of the particulate matter emission levels of heavy-duty vehicles under actual complex operating conditions, offers a scientific, rigorous, and repeatable testing scheme, fills the international gap in heavy-duty vehicle testing standards, and supports the formulation of regulations and the research and development of low-emission technologies.
Smart Images
Figure CN121933281A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of motor vehicle emission pollutant testing technology, and particularly relates to a method for testing particulate matter emissions from brake wear of heavy-duty vehicles. Background Technology
[0002] With increasingly stringent global controls on vehicle exhaust particulate matter emissions, non-exhaust particulate matter emissions, particularly brake wear particulate matter, are contributing a growing proportion to PM2.5 and PM10 in the atmosphere. The GTR 24 regulation, published by the United Nations World Forum for Harmonization of Vehicle Regulations (WP.29), established for the first time a globally unified testing procedure for brake wear particulate matter emissions from light-duty vehicles.
[0003] The current GTR 24 and its related technical standards are designed entirely for light vehicles. Its core parameters, such as test cycles (e.g., the WLTP-Brake cycle), load conditions (inertial simulation range), and braking force distribution, are based on the actual operating characteristics of light vehicles and cannot be directly applied to heavy vehicles. However, heavy vehicles and light vehicles differ fundamentally in the following aspects: 1) Complex vehicle types and operating conditions: including city buses, long-distance trucks, dump trucks, semi-trailer tractors, etc., with huge differences in their operating speed range, braking frequency and intensity.
[0004] 2) Large load variation range: The mass difference between unloaded and fully loaded is several times, resulting in braking inertia and braking energy that are much higher than those of light vehicles.
[0005] 3) Different braking system characteristics: They generally use air brakes, retarders, etc., and their braking response and torque output are significantly different from the hydraulic braking systems of light vehicles.
[0006] 4) Actual road braking characteristics are very different: Due to their large mass and inertia, heavy vehicles usually exhibit braking events with longer durations, higher braking energy, and more complex braking sequences (such as continuous downhill braking).
[0007] Currently, there are no specific testing standards or mature methods for brake wear particulate matter emissions from heavy-duty vehicles, either domestically or internationally. Directly applying testing methods for light-duty vehicles would result in test results that significantly deviate from reality, failing to accurately assess the true emission levels of heavy-duty vehicles and thus hindering effective regulation and the development of low-emission braking technologies. Therefore, developing a brake wear particulate matter emission testing method specifically for heavy-duty vehicles that can reflect their actual operating characteristics is urgently needed. Summary of the Invention
[0008] This invention provides a method for testing particulate matter emissions from brake wear of heavy-duty vehicles, addressing the limitations of current methods for testing particulate matter emissions from brake wear of light-duty vehicles, which cannot meet the testing requirements of heavy-duty vehicles under various scenarios and load characteristics. This invention employs multiple emission test cycles covering different typical operating scenarios (such as urban and highway environments) and specifies that tests must be conducted under various load conditions, including no-load, half-load, and full-load, ensuring that the test results accurately reflect the emission levels of heavy-duty vehicles under actual complex operating conditions.
[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for testing particulate matter emissions from brake wear of heavy-duty vehicles includes the following steps: S1. Obtain actual road braking characteristic data of heavy vehicles and analyze the probability distribution of braking characteristic parameters; S2. Construct a dedicated brake emission test cycle for heavy-duty vehicles; S3. Construct a brake emission testing system, including: configuration and inertial simulation of the test brake dynamometer bench, and setup of brake emission detection subsystems other than the brake dynamometer; S4. Execute the test program; S5. Calculate the particulate matter emission factor (PM) based on test data. EF,brake-i and particulate matter number emission factor PN EF,brake-i Establish a PM2.5 emission standard for vehicle braking particulate matter. EF,veh and particulate matter number emissions PN EF,veh Relationship with the emission factors.
[0010] Preferably, the particulate matter emissions from the vehicle's braking system are PM2.5. EF,veh With the particulate matter emission factor PM EF,brake-i The calculation formula is as follows: Where: c 空载 +c 半载 +c 满载 =1; In the formula: i — the number of axles of the test vehicle; PM EF,brake-i，空载 — PM emission factor under no-load test conditions, mg / km; c 空载 — The percentage of time the test vehicle spent in an unloaded state during actual operation; PM EF,brake-i，半载 — PM emission factor under half-load test conditions, mg / km; c 半载 — The percentage of time the test vehicle was in a half-load state during actual operation; PM EF,brake-i，满载— PM emission factor under full-load test conditions, mg / km; c 满载 — The percentage of time the test vehicle was in full load during actual operation; The number of particulate matter emissions from vehicle braking PN EF,veh With the particulate matter number emission factor PN EF,brake-i The calculation formula is as follows: In the formula: i — the number of axles of the test vehicle; PN EF,brake-i，空载 — PN emission factor under no-load test conditions, particles / km; c 空载 — The percentage of time the test vehicle spent in an unloaded state during actual operation; PN EF,brake-i，半载 — PN emission factor under half-load test conditions, particles / km; c 半载 — The percentage of time the test vehicle was in a half-load state during actual operation; PN EF,brake-i，满载 — PN emission factor under full-load test conditions, particles / km; c 满载 — The percentage of time the test vehicle was in full load during actual operation.
[0011] Preferably, step S1 includes the following steps: a) Obtain a large sample size of actual operating data for specific types of vehicles (such as dump trucks, city buses, etc.); b) Extract key braking characteristic parameters for specific types of heavy-duty vehicles; c) Cluster analysis and probability distribution fitting methods are used to analyze and determine the probability distribution of the braking characteristic parameters.
[0012] Preferably, the actual operating data in step a) includes: timestamp, vehicle speed, GPS location, and real braking event data collected using high-precision sensors, including: braking pressure and brake engagement status, to distinguish between braking deceleration and non-braking deceleration. It should be noted that the above actual operating data was obtained by combining data from high-precision sensors installed on a small number of representative vehicles. These high-precision sensors include brake pressure sensors and torque sensors. The data includes timestamps (accuracy 5ms), vehicle speed (0-60km / h), GPS positioning accuracy (±5m), brake pressure (±0.1MPa), and brake engagement status (0=disengaged, 1=engaged), as well as non-braking deceleration such as coasting.
[0013] The braking characteristic parameters mentioned in step b) include, but are not limited to: initial braking speed distribution, average deceleration distribution, braking duration, braking interval time, braking distance, friction work per braking cycle, and number of braking cycles per unit mileage.
[0014] Preferably, the brake emission test cycle in step S2 is a brake emission test cycle for a specific type of heavy vehicle constructed based on the probability distribution of brake characteristic parameters in step c). The emission test cycle can be selected as: basic urban cycle, highway cycle and comprehensive durability cycle. The key test parameters of the emission test cycle include: braking initiation time, braking end time, braking duration, braking initiation speed, braking end speed, average deceleration, braking distance, and specific friction work, which constitute a braking event.
[0015] It is important to note that the joint probability distribution of the numerical sequences of key test parameters in the emission test cycle must pass a chi-square test with the actual road distribution obtained in step S1 to ensure statistical consistency. The total mileage of the test cycle should be no less than 150 kilometers, including a sufficient number of braking events to ensure statistical significance and that the generated particulate matter mass reaches an accurately measurable level.
[0016] Preferably, the test of the brake dynamometer test bench system in step S3 includes three load conditions: no load, half load, and full load.
[0017] It should be noted that the above three load classifications are based on the characteristic of large load variations in heavy-duty vehicles, and the corresponding equivalent inertial mass is determined according to the vehicle type and its maximum design gross mass. Considering the potential additional energy recovery systems (such as regenerative braking in electric buses) that heavy-duty vehicles, such as dump trucks and buses, may have, the test bench system should be capable of simulating the coordinated distribution of torque between regenerative braking and friction braking, and should be able to set different recovery strategies. The test bench should be able to accurately simulate the vehicle speed-time curve required by the test cycle constructed in step S2.
[0018] Preferably, the brake emission testing subsystem in step S3, excluding the brake dynamometer, includes: a cooling air conditioner, an automated control system, a brake chamber, a sampling pipeline, and a particulate matter mass (PM) and particulate matter number (PN) emission testing equipment subsystem.
[0019] Preferably, the specific requirements of the subsystem are as follows: 1) Cooling air conditioners should be able to provide clean air at constant temperature, constant humidity and constant flow rate; 2) The automated control system should be able to achieve coordinated control between subsystems and the acquisition and recording of test data; 3) The particulate matter sampling plane should be located at least 6 times the diameter of the sampling pipe downstream of the brake chamber outlet, and the distance from the brake chamber outlet to the particulate matter sampling plane should be a horizontal straight pipe, and the distance before the brake chamber inlet should be at least 2 times the diameter of the sampling pipe, and the cross-section of the two pipe sections should not change. 4) The sampling pipeline is the pipeline between the brake chamber outlet and the particulate matter sampling probe inlet. The inner surface of the pipeline should be made of stainless steel or equivalent material that has been electrolytically polished. 5) PM and PN emissions were measured using the filter membrane weighing method and the particulate matter counter, respectively.
[0020] Preferably, step S4 includes the following test steps: First, the test is performed on the brake dynamometer bench according to the test cycle constructed in step S2 and the load conditions set in step S3. Secondly, adjust the cooling airflow to make the brake temperature as close as possible to the brake temperature level under actual road driving conditions. Then, the brakes are broken in according to the standard procedure; Finally, emissions testing begins. Throughout the testing process, time, vehicle speed, braking pressure, brake temperature, particulate matter mass / number concentration, and dilution flow rate must be measured and recorded simultaneously. At least three valid tests must be performed under each load condition, and the average value is taken as the final result.
[0021] It should be noted that: for the test vehicle of this application, only one side brake, such as the left brake or the right brake, needs to be selected for this step of the test, and it is assumed that the particulate matter emissions of the left brake and the right brake of the same axle are the same.
[0022] Preferably, the particulate matter emission factor (PM) in step S5 is... EF,brake-i The particulate matter number emission factor (PN) is calculated based on the particulate matter mass collected by the filter membrane and the total test mileage, expressed in milligrams per kilometer (mg / km). EF,brake-i The values are based on real-time particulate matter counter data, and the unit is particles per kilometer / km.
[0023] It should be noted that the final test results should provide emission factors under three conditions: no load, half load, and full load, and a weighted average should be calculated. The weights are determined based on the proportion of time spent in different load states during actual operation of this type of vehicle. Vehicle braking emissions results (PM EF,veh PN EF,veh The result is obtained by summing the emission factors of all brakes on each axle.
[0024] Compared with the prior art, the beneficial effects of the present invention are: This application designs a complete testing process, from constructing a test loop based on a combination of heavy-duty vehicle big data and actual road operation data, to bench configuration, particulate matter sampling, and data analysis. This forms a complete, scientifically rigorous, and repeatable testing scheme specifically for heavy-duty vehicles, filling a technological gap in this field both domestically and internationally. Specifically: 1) A method was proposed to extract braking characteristic parameters from a large sample size of actual operating data obtained from existing remote emission monitoring platforms for heavy-duty vehicles, construct test cycles, and perform a chi-square test on the probability distribution of braking characteristic parameters in actual vehicle road operation. By utilizing high-precision sensors such as brake pressure sensors and torque sensors, real brake friction deceleration events were accurately screened out, fundamentally solving the industry problem of non-braking deceleration interference in heavy-duty vehicles and ensuring the accuracy of braking characteristic parameter analysis.
[0025] 2) Established testing specifications for heavy-duty vehicles across multiple scenarios and load characteristics. Innovatively, it proposed constructing dedicated emission test cycles for different typical operating scenarios, such as basic urban cycles and highway cycles. This allows the testing scheme to accurately match the operating scenarios of various heavy-duty vehicles, solving the problem of "poor adaptability of general cycles" in existing technologies, and providing more targeted technical support for brake emission control under different application scenarios. It also stipulates that testing must be conducted under multiple load conditions, including no-load, half-load, and full-load, ensuring that the test results accurately reflect the emission levels of heavy-duty vehicles under actual complex operating conditions.
[0026] 3) Simultaneously, considering the potential additional energy recovery systems of heavy-duty vehicles during bench testing, the bench system should possess regenerative braking simulation capabilities. The testing process fully considers achieving accurate calculations through multi-axle individual testing combined with multi-load weighted calculations, ultimately yielding the overall vehicle braking emissions. Attached Figure Description
[0027] Figure 1 This is the overall flowchart of the test method for particulate matter emissions from heavy vehicle brake wear according to this application.
[0028] Figure 2 This is a schematic diagram of the heavy-duty vehicle brake emission testing system of this application. Detailed Implementation
[0029] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.
[0030] This application uses a "heavy-duty city bus" as an example to describe the invention in detail. The specific steps are as follows: S1. Acquisition and analysis of actual road braking data: 1) Obtain operational data of 500 heavy-duty city buses from national / local heavy-duty vehicle remote emission monitoring platforms.
[0031] 2) Randomly select 20 vehicles to install brake pressure sensors, collect detailed braking data for one month, and extract key braking characteristic parameters, including: initial braking speed, average deceleration, braking duration, braking interval time, braking distance, friction work per braking cycle, and number of braking cycles per unit mileage.
[0032] 3) Cluster analysis and probability distribution fitting methods were used to obtain the probability distribution of the braking characteristic parameters of this vehicle model. Specifically, the initial braking speed is mainly distributed between 5-50 km / h, and the average deceleration is mainly concentrated between 0.3-1.2 m / s². 2 The braking duration is mainly distributed between 3-25s, the braking interval is 30-300s, the braking distance is 2-50m, the friction work of a single braking is 0.005-0.08kJ / kg, and the number of braking times per unit mileage is about 1.2 times / km.
[0033] S2. Constructing the brake emission test cycle: 1) Construct a “basic urban loop” with a total duration of 4 hours, a distance of approximately 150 kilometers, and 300 braking events.
[0034] 2) The braking events in the cycle are composed of parameters such as initial braking speed, average deceleration, and duration, as shown in Table 1. The joint probability distribution of their numerical sequence is compared with the distribution of actual road data in step S1 using a chi-square test (p>0.05).
[0035] Table 1. Key Parameters of Basic Urban Circulation (Partial)
[0036] S3. Construct a brake emission testing system: A. Brake dynamometer bench configuration and inertial simulation: 1) The brake under test is the left-side disc brake of the front axle of the bus (for the right-side disc brake, the emission test results of the left-side disc brake can be used directly). For the brakes of the other axles, only one side of the brake should be selected for the brake emission test. This step of the test must be carried out on all axles of the test vehicle using either the left or right side brake. The test bus has two axles: the front axle and the rear axle.
[0037] 2) Set three test inertial masses: no load (8000kg), half load (12000kg), and full load (16000kg).
[0038] 3) The test bench system is set to simulate the typical electric regenerative braking strategy of this vehicle model, with a recovered energy ratio of 20%.
[0039] B. Brake emission testing subsystem setup (excluding brake dynamometer): 1) A partial flow particulate sampling system was adopted, and a suitable dilution ratio of 100:1 was set according to the particulate matter concentration and the measurement range of the particulate matter emission testing equipment.
[0040] 2) Cooling air conditioning: Adjust the airflow of the cooling air conditioning system to provide clean air at constant temperature, humidity, and flow rate. For example: temperature control range: 21~25℃, humidity control range: 45%~55% RH, constant flow rate: 600m³ / h 3 / h.
[0041] 3) Automated control system: Automatically executes brake emission test cycle through linkage control of brake, cooling air conditioning and particulate matter testing equipment, continuously samples and records test data.
[0042] 4) Brake chamber and sampling pipeline: The particulate matter sampling plane should be located at least 6 times the diameter of the sampling pipeline downstream of the brake chamber outlet, and the distance from the brake chamber outlet to the particulate matter sampling plane should be a horizontal straight pipe; before the brake chamber inlet, there should be at least 2 times the diameter of the sampling pipeline in a horizontal straight pipe, and the cross-sections of the two pipe sections should be consistent. Figure 2 The diagram shows a schematic of a heavy-duty vehicle brake emission testing system.
[0043] 5) Simultaneous sampling was performed using a 47mm Teflon filter membrane and a particulate counter.
[0044] S4. Execute the test program: 1) After the brakes are broken in, run the "basic urban cycle" three times in sequence under no-load, half-load, and full-load conditions.
[0045] 2) Record all data to ensure that parameters such as brake surface temperature and brake pressure are within a reasonable range.
[0046] S5. Result Calculation: 1) The particulate matter emission factor (PM) of the front axle brake was calculated by weighing the filter membrane. EF,brake-1 Unloaded: 12.5 mg / km, Half-loaded: 18.7 mg / km, Full-loaded: 25.4 mg / km; Particulate matter emission factor (PM) of the rear axle brake. EF,brake-2 Unloaded: 8.1 mg / km, Half-loaded: 11.2 mg / km, Full-loaded: 15.2 mg / km.
[0047] 2) The particulate matter number emission factor (PN) of the front axle brake is calculated based on the exported real-time particulate matter number concentration data. EF,brake-1 Unloaded 3.5×10 10 Units / km, half load 5.2×10 10 Units / km, fully loaded 7.1×1010 Units / km; Particulate matter emission factor PN of rear axle brakes EF,brake-2 Unloaded 1.8×10 10 Units / km, half load 3.5×10 10 Units / km, 5.7×10 at full load 10 Units per km.
[0048] 3) The time percentage data of each load state during the actual operation of the test vehicle, such as: 20% unloaded, 50% half-loaded, and 30% fully loaded. Calculate the overall braking emission results of the test vehicle according to the following formulas (1) and (2): PM EF,veh = (12.5 + 8.1) 2 20%+ (18.7+11.2) 2 50% + (25.4 + 15.2) 2 30% = 62.5 mg / km PN EF,veh = (3.5 × 10 10 +1.8×10 10 ) 2 20%+ (5.2×10 10 +3.5×10 10 ) 2 50%+ (7.1×10 10 +5.7×10 10 ) 2 30% = 1.85 × 10 11 units / km A schematic diagram of a heavy-duty vehicle brake emission testing system provided by the present invention is shown below. Figure 2 As shown.
[0049] 1) The cooling air conditioner provides clean cooling air with constant temperature, humidity and flow rate for testing. The cooling air flows through the brake chamber along the pipeline and blows the particulate matter generated by brake wear to the sampling pipeline, and finally circulates back to the cooling air conditioner (or can be discharged into the atmosphere).
[0050] 2) The brake assembly is completely enclosed in the brake chamber. Cooling air leakage is not allowed in the brake chamber or the exhaust test system piping. The cooling air leakage rate in the system should be less than 5%.
[0051] 3) The brake dynamometer shall include: a variable speed motor for accelerating or maintaining a constant speed and adjusting the test inertia; a servo controller for driving the brake; a mechanical assembly for mounting the brake under test, which allows the brake disc or brake drum to rotate freely and absorbs the reaction force generated by braking; a rigid structure for mounting all necessary subsystems, which shall be able to absorb the forces and torques generated by the brake during the test; and sensors and electronic equipment for collecting data and monitoring the operation of the test system.
[0052] 4) The automated control system is used to control the speed of the motor and the operation and interaction between different systems. It should be able to automatically execute the brake emission test cycle through the linkage control of the brake, cooling air conditioning and particulate matter testing equipment, etc.; continuously sample and record test data; and monitor signals, messages, alarms or emergency stops from operators and different systems in real time.
[0053] 5) The sampling probes of particulate matter emission testing equipment should all be extended to the sampling plane for sampling, including PM2.5. 2.5 PM 10 TPN and SPN are used to test the mass of particles with a diameter of no more than 2.5 μm, the mass of particles with a diameter of no more than 10 μm, the total number concentration of particles with a diameter of ≥10 nm, and the number concentration of solid particles with a diameter of ≥10 nm after volatile substances have been removed, respectively.
[0054] Overall, the method for testing particulate matter emissions from heavy-duty vehicle brake wear according to this invention has the following advantages: First, its pioneering and targeted nature: It is the first to propose a systematic and specialized test method for particulate matter emissions from brake wear of heavy-duty vehicles, which solves the technical problem that light-duty vehicle standards such as GTR 24 are not applicable to heavy-duty vehicles, and fills an international gap.
[0055] Second, high real representativeness: The test cycle is based on big data of actual road operation of heavy vehicles, and statistical verification is used to ensure that its braking characteristics (intensity, frequency, speed) are consistent with reality, so that the test results can truly reflect the emission level of vehicles on the road.
[0056] Third, comprehensiveness and scientific rigor: It innovatively introduces multi-load condition testing, multi-cycle scenario coverage, and regenerative braking simulation, comprehensively considering the key variables affecting the braking emissions of heavy-duty vehicles, making the testing scheme more scientific and rigorous.
[0057] Fourth, operability and scalability: This method is based on mature brake dynamometer test benches and particulate matter sampling technology. It can be implemented in existing testing institutions with only targeted adaptation and software upgrades, which facilitates future regulatory adoption and large-scale application.
[0058] Fifth, it supports the formulation of regulations: It provides the first repeatable and comparable test benchmark for heavy-duty vehicle braking emissions in this field, and provides an indispensable technical foundation for the next step of formulating national limits for particulate matter emissions from heavy-duty vehicle braking.
[0059] It is important to note that the three test cycles involved in this application (basic urban cycle, highway cycle, and comprehensive durability cycle) all follow a unified construction principle: First, based on large-sample operating data of heavy vehicles in different actual scenarios (such as urban roads, highways, and mixed roads), braking characteristic parameters for each scenario are extracted, and the probability distribution characteristics of each parameter are obtained through cluster analysis and probability distribution fitting; then, braking event sequences are generated based on these distribution characteristics, and verified through chi-square tests to ensure that their statistical characteristics are consistent with actual data. Meanwhile, the core difference between the three cycles lies in the different operating scenarios they simulate: the basic urban cycle targets frequent start-stop and low-to-medium speed braking conditions in urban areas; the highway cycle simulates braking events with higher initial speeds and longer intervals during high-speed driving; and the comprehensive durability cycle covers continuous braking and variable-intensity braking under complex road conditions such as suburban and mountainous areas. Through the combination of these three types of cycles, the braking and emission characteristics of heavy vehicles under different actual operating conditions can be comprehensively reflected, providing a scientific basis for differentiated assessment and control. This application uses the construction of the "basic urban cycle" as an example for detailed explanation.
[0060] The above description is merely an example of the embodiments of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.
Claims
1. A method for testing particulate matter emissions from heavy-duty vehicle brake wear, characterized in that: Includes the following steps: S1. Obtain actual road braking characteristic data of heavy vehicles and analyze the probability distribution of braking characteristic parameters; S2. Construct a dedicated brake emission test cycle for heavy-duty vehicles; S3. Construct a brake emission testing system, including: test brake dynamometer bench configuration and inertial simulation, and brake emission detection subsystem setup other than the brake dynamometer; S4. Execute the test program; S5. Calculate the particulate matter emission factor (PM) based on test data. EF,brake-i and particulate matter number emission factor PN EF,brake-i Establish a PM2.5 emission standard for vehicle braking particulate matter. EF,veh and particulate matter number emissions PN EF,veh Relationship with the emission factors.
2. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 1, characterized in that: The particulate matter emissions from vehicle braking EF,veh With the particulate matter emission factor PM EF,brake-i The calculation formula is as follows: Where: c 空载 +c 半载 +c 满载 =1; In the formula: i — the number of axles of the test vehicle; PM EF,brake-i，空载 — PM emission factor under no-load test conditions, mg / km; c 空载 — The percentage of time the test vehicle spent in an unloaded state during actual operation; PM EF,brake-i，半载 — PM emission factor under half-load test conditions, mg / km; c 半载 — The percentage of time the test vehicle was in a half-load state during actual operation; PM EF,brake-i，满载 — PM emission factor under full-load test conditions, mg / km; c 满载 — The percentage of time the test vehicle was in full load during actual operation; The number of particulate matter emissions from vehicle braking PN EF,veh With the particulate matter number emission factor PN EF,brake-i The calculation formula is as follows: In the formula: i — the number of axles of the test vehicle; PN EF,brake-i，空载 — PN emission factor under no-load test conditions, particles / km; c 空载 — The percentage of time the test vehicle spent in an unloaded state during actual operation; PN EF,brake-i，半载 — PN emission factor under half-load test conditions, particles / km; c 半载 — The percentage of time the test vehicle was in a half-load state during actual operation; PN EF,brake-i，满载 — PN emission factor under full-load test conditions, particles / km; c 满载 — The percentage of time the test vehicle was in full load during actual operation.
3. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 1, characterized in that: Step S1 includes the following steps: a) Obtain a large sample size of actual operational data for specific types of vehicles; b) Extract key braking characteristic parameters for specific types of heavy-duty vehicles; c) Cluster analysis and probability distribution fitting methods are used to analyze and determine the probability distribution of the braking characteristic parameters.
4. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 3, characterized in that: The actual operating data in step a) includes: timestamp, vehicle speed, GPS location, and real braking event data collected using high-precision sensors, including: braking pressure and brake engagement status, to distinguish between braking deceleration and non-braking deceleration. The braking characteristic parameters mentioned in step b) include, but are not limited to: initial braking speed, average deceleration, braking duration, braking interval time, braking distance, friction work per braking cycle, and number of braking cycles per unit mileage.
5. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 3, characterized in that: The brake emission test cycle in step S2 is a brake emission test cycle for a specific type of heavy vehicle constructed based on the probability distribution of brake characteristic parameters in step c). The emission test cycle can be selected as: basic urban cycle, highway cycle and comprehensive durability cycle. The key test parameters for the test cycle include: braking start time, braking end time, braking initial speed, braking end speed, average deceleration, braking duration, braking distance, and specific friction work.
6. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 1, characterized in that: The test of the brake dynamometer test bench system in step S3 includes three load conditions: no load, half load, and full load.
7. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 1, characterized in that, The brake emission testing subsystem in step S3, excluding the brake dynamometer, includes: a cooling air conditioner, an automated control system, a brake chamber, a sampling pipeline, and particulate matter mass (PM) and particulate matter number (PN) emission testing equipment.
8. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 7, characterized in that, The specific requirements for the subsystem are as follows: 1) Cooling air conditioners should be able to provide clean air at constant temperature, constant humidity and constant flow rate; 2) The automated control system should be able to achieve coordinated control between subsystems and the acquisition and recording of test data; 3) The particulate matter sampling plane should be located at least 6 times the diameter of the sampling pipe downstream of the brake chamber outlet, and the distance from the brake chamber outlet to the particulate matter sampling plane should be a horizontal straight pipe, and the distance before the brake chamber inlet should be at least 2 times the diameter of the sampling pipe, and the cross-section of the two pipe sections should not change. 4) The sampling pipeline is the pipeline between the brake chamber outlet and the particulate matter sampling probe inlet. The inner surface of the pipeline should be made of stainless steel or equivalent material that has been electrolytically polished. 5) PM and PN emissions were measured using the filter membrane weighing method and the particulate matter counter, respectively.
9. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 1, characterized in that, Step S4 includes the following test steps: First, the test is performed on the brake dynamometer bench according to the test cycle constructed in step S2 and the load conditions set in step S3. Secondly, adjust the cooling airflow to make the brake temperature as close as possible to the brake temperature level under actual road driving conditions. Then, the brakes are broken in according to the standard procedure; Finally, emissions testing begins. Throughout the testing process, time, vehicle speed, braking pressure, brake temperature, particulate matter mass / number concentration, and dilution flow rate must be tested and recorded simultaneously. At least three valid tests must be performed under each load condition, and the average value is taken as the final result.
10. The method for testing particulate matter emissions from heavy-duty vehicle brake wear according to claim 1, characterized in that, The particulate matter emission factor (PM) in step S5 EF,brake-i The particulate matter number emission factor (PN) is calculated based on the particulate matter mass collected by the filter membrane and the total test mileage, expressed in milligrams per kilometer (mg / km). EF,brake-i The values are based on real-time particulate matter counter data, and the unit is particles per kilometer / km.