CN107886593A - A kind of computational methods of fuel tank discharge vaporization leak diagnostics inspection policies - Google Patents
A kind of computational methods of fuel tank discharge vaporization leak diagnostics inspection policies Download PDFInfo
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- 239000002828 fuel tank Substances 0.000 title claims abstract description 119
- 238000007689 inspection Methods 0.000 title abstract description 3
- 230000008016 vaporization Effects 0.000 title abstract 3
- 238000009834 vaporization Methods 0.000 title abstract 3
- 238000000205 computational method Methods 0.000 title abstract 2
- 238000001514 detection method Methods 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims abstract description 19
- 238000007906 compression Methods 0.000 claims abstract description 7
- 230000006835 compression Effects 0.000 claims abstract description 4
- 238000003745 diagnosis Methods 0.000 claims description 21
- 239000007789 gas Substances 0.000 claims description 19
- 238000004364 calculation method Methods 0.000 claims description 17
- 239000000446 fuel Substances 0.000 claims description 9
- 230000000704 physical effect Effects 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 2
- 239000002737 fuel gas Substances 0.000 claims description 2
- 239000000295 fuel oil Substances 0.000 abstract 2
- 238000011217 control strategy Methods 0.000 abstract 1
- 238000004134 energy conservation Methods 0.000 abstract 1
- 238000002347 injection Methods 0.000 abstract 1
- 239000007924 injection Substances 0.000 abstract 1
- 239000003570 air Substances 0.000 description 40
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 238000012544 monitoring process Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 239000012080 ambient air Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012806 monitoring device Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- G—PHYSICS
- G07—CHECKING-DEVICES
- G07C—TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
- G07C5/00—Registering or indicating the working of vehicles
- G07C5/08—Registering or indicating performance data other than driving, working, idle, or waiting time, with or without registering driving, working, idle or waiting time
- G07C5/0808—Diagnosing performance data
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Abstract
Description
技术领域technical field
本发明涉及燃油箱泄漏诊断检测领域，具体涉及一种燃油箱蒸发排放泄漏诊断检测策略的计算方法，对实际检漏过程中的充气和检测时间做出精确控制，提高诊断的精准性。The invention relates to the field of diagnosis and detection of fuel tank leakage, in particular to a calculation method for a diagnosis and detection strategy of evaporative emission leakage of a fuel tank, which precisely controls the inflation and detection time in the actual leak detection process and improves the accuracy of diagnosis.
背景技术Background technique
在汽车行驶一段时间以后，燃油箱会因较高的环境温度以及燃油箱中燃油泵功率损失生成的热，产生一些碳氢化合物蒸汽。当油箱中存在微小泄漏时，这些蒸汽通过泄漏孔排放到环境中，形成蒸发排放污染物，这对环境会造成很大的危害，同时也是一种资源的浪费。After the car has been running for a period of time, the fuel tank will generate some hydrocarbon vapors due to the high ambient temperature and the heat generated by the power loss of the fuel pump in the fuel tank. When there is a small leak in the fuel tank, the steam is discharged into the environment through the leak hole, forming evaporative emission pollutants, which will cause great harm to the environment and is also a waste of resources.
目前，已有许多国家制定并出台了相当严格的汽车环保排放政策来限制这些蒸发物排放，美国加州空气资源委员会在最新出台的法规中，要求检测相当于一个0.5mm孔径的蒸汽泄漏，并将其检测结果反馈到汽车发动机控制ECU，并对车主实施故障报警提示，以实时监测燃油箱泄漏超标情况。中国也于2017年1月1日在全国范围内执行GB18352.5—2013《轻型汽车污染物排放限制级测量方法(中国第五阶段)》，文件中也增加了对燃油箱蒸发排放的检查要求，促使汽车制造商对产品技术做出进一步的改进升级。At present, many countries have formulated and issued very strict automobile environmental protection emission policies to limit these evaporative emissions. In the latest regulations issued by the California Air Resources Board, it is required to detect a vapor leak equivalent to a 0.5mm aperture, and to The detection results are fed back to the car engine control ECU, and the car owner is given a fault alarm prompt to monitor the leakage of the fuel tank in real time. China also implemented GB18352.5-2013 "Light Vehicle Pollutant Emission Limit Level Measurement Method (China Phase V)" nationwide on January 1, 2017, and the inspection requirements for fuel tank evaporative emissions have also been added to the document , Prompting automakers to make further improvements and upgrades to product technology.
为了限制燃油箱中碳氢化合物蒸汽的微小泄漏排放，一种方法是在汽车中安装燃油箱泄漏诊断模块，该诊断模块可以识别整个燃油箱通风系统中是否存在轻微泄漏(超过0.5mm孔径)和重大泄漏(超过1mm孔径)，并通过故障指示灯显示。检测燃油箱系统是否泄漏的方法是：首先，空气压缩机建立起一个相当于参考泄漏量为0.5mm孔径的计示压力并维持一段时间，并将维持此计示压力的泵电流作为参考电流值；然后，通过此压缩机向待测燃油箱中充气，在随后进行的压力建立过程中，记录实测泵电流值并与参考电流值进行比较，如果与参考电流值相比有所下降，说明燃油箱系统中存在泄漏的信号，如果超过参考电流值时则表明系统中没有泄漏。然而，在空气压缩机向油箱充气阶段，如何根据实际环境和不同的压缩机工况精准控制充气以及检测时间也是一个技术难题。In order to limit the emission of small leaks of hydrocarbon vapors in the fuel tank, one method is to install a fuel tank leak diagnostic module in the car, which can identify whether there are minor leaks (more than 0.5mm hole diameter) in the entire fuel tank ventilation system and Significant leaks (over 1mm pore size) are indicated by a fault indicator light. The method to detect whether the fuel tank system is leaking is as follows: first, the air compressor establishes a gauge pressure equivalent to a reference leakage of 0.5mm aperture and maintains it for a period of time, and uses the pump current that maintains the gauge pressure as the reference current value ; Then, fill the fuel tank to be tested through this compressor, and record the measured pump current value and compare it with the reference current value during the subsequent pressure build-up process. If there is a signal of leakage in the tank system, if the reference current value is exceeded, it indicates that there is no leakage in the system. However, when the air compressor is filling the oil tank, how to accurately control the filling and detection time according to the actual environment and different compressor working conditions is also a technical problem.
发明内容Contents of the invention
本发明的目的在于针对上述现有技术中的问题，提供一种燃油箱蒸发排放泄漏诊断检测策略的计算方法，对运用于汽车燃油箱蒸发排放泄漏诊断模块中的泄漏诊断检测策略，在燃油箱所处的实际环境条件下，通过计算，精确控制实际检漏过程中的充气和检测时间，以实现蒸发排放泄漏诊断的精准性，从而优化蒸发排放泄漏诊断检测策略的应用。The purpose of the present invention is to solve the above-mentioned problems in the prior art, and provide a calculation method for a fuel tank evaporative emission leakage diagnosis and detection strategy. Under the actual environmental conditions, through calculation, the inflation and detection time in the actual leak detection process can be accurately controlled to achieve the accuracy of evaporative emission leak diagnosis, thereby optimizing the application of evaporative emission leak diagnosis and detection strategies.
为了实现上述目的，本发明采用的技术方案包括以下步骤：In order to achieve the above object, the technical solution adopted in the present invention comprises the following steps:
S1：将待检测燃油箱简化为开口系统，计算燃油箱的泄漏速度和燃油箱质量泄漏率；S1: Simplify the fuel tank to be tested into an opening system, and calculate the leakage rate of the fuel tank and the mass leakage rate of the fuel tank;
S2：在空气压缩机向燃油箱充气阶段，根据燃油箱的进气率以及压缩机的排气率，计算压缩机的排气温度，再根据工程热力学定律，得出燃油箱的进气焓值与油气泄漏的焓值；S2: When the air compressor is filling the fuel tank, calculate the exhaust temperature of the compressor according to the intake rate of the fuel tank and the exhaust rate of the compressor, and then calculate the intake enthalpy of the fuel tank according to the law of engineering thermodynamics Enthalpy with oil and gas leakage;
S3：建立燃油箱的质量守恒方程，并结合充气后燃油箱质量Mb的计算关系式：S3: Establish the mass conservation equation of the fuel tank, and combine the calculation relationship of the mass M b of the fuel tank after inflation:
以及空腔内压计算公式 And the calculation formula of cavity internal pressure
求得压缩机充气阶段，燃油箱压力保持平衡时所用时间t，即泄漏检测需要时间；Obtain the time t required for the pressure of the fuel tank to be balanced during the charging stage of the compressor, that is, the time required for leak detection;
式中，Mo为燃油箱固有的质量，min为燃油箱进气率及压缩机排气率，mout为燃油箱油气的泄漏率，R为气体常数，T0为气体温度，Vb为油箱空腔体积。In the formula, M o is the inherent mass of the fuel tank, min is the intake rate of the fuel tank and the exhaust rate of the compressor, m out is the leakage rate of fuel gas in the fuel tank, R is the gas constant, T 0 is the gas temperature, V b is the volume of the tank cavity.
油箱蒸发排放泄漏诊断检测策略是由空气压缩机向燃油箱中充气一段时间后，记录带动压缩机的电动机电流值，并与空气泵通过孔径为0.5mm的基准开口所测泵电流值进行对比，根据对比结果来判断燃油箱是否存在直径0.5mm以上的燃油泄漏。The fuel tank evaporative emission leakage diagnosis and detection strategy is to record the current value of the motor driving the compressor after the air compressor inflates the fuel tank for a period of time, and compare it with the pump current value measured by the air pump through the reference opening with an aperture of 0.5mm. According to the comparison results, judge whether there is any fuel leakage with a diameter of 0.5mm or more in the fuel tank.
所述的步骤S1中，油箱内外压差ΔP与泄漏速度vb的关系为：In the step S1, the relationship between the internal and external pressure difference ΔP of the fuel tank and the leakage velocity v b is:
燃油箱的泄漏速度为：The leak rate of the fuel tank is:
根据燃油箱的泄漏孔径Db，燃油箱质量泄漏率表示为：According to the leakage hole diameter D b of the fuel tank, the mass leakage rate of the fuel tank is expressed as:
式中，ρb为油液密度，ξb为泄漏系数。In the formula, ρ b is the oil density, and ξ b is the leakage coefficient.
所述的步骤S2中，在压缩机压缩过程中，进气温度T0与排气温度为Tin有如下关系：In the step S2, during the compression process of the compressor, the intake air temperature T0 has the following relationship with the discharge temperature Tin :
即压缩机的排气温度为：That is, the discharge temperature of the compressor is:
式中的n根据压缩机实际内部压缩热力过程在1～1.4取值；In the formula, n takes a value from 1 to 1.4 according to the actual internal compression thermodynamic process of the compressor;
温度为T的空气焓值h表示为：The air enthalpy value h at temperature T is expressed as:
h＝f(T,d)h=f(T,d)
式中的d为每千克干空气中含有的水蒸气质量，单位为kg/kg；燃油箱进气焓值表示为：hin＝f(Tin,d)，其具体值查询热物性参数表或者通过其相关公式计算得出；In the formula, d is the mass of water vapor contained in each kilogram of dry air, and the unit is kg/kg; the intake enthalpy value of the fuel tank is expressed as: h in =f(T in ,d), and its specific value can be found in the thermal physical property parameter table Or calculated by its related formula;
hout为燃油箱油气泄漏的焓值，hout＝f(Tout,d)。h out is the enthalpy value of fuel tank gas leakage, h out =f(T out ,d).
所述的步骤S3中，建立燃油箱的质量守恒方程如下：In the step S3, the mass conservation equation of the fuel tank is established as follows:
式中，hb为充气后燃油箱焓值，ho为燃油箱固有的焓值。In the formula, h b is the enthalpy value of the fuel tank after inflation, and h o is the intrinsic enthalpy value of the fuel tank.
采用四阶龙格库塔法求解燃油箱内部气体的质量守恒方程，具体的计算方法如下：The fourth-order Runge-Kutta method is used to solve the mass conservation equation of the gas inside the fuel tank. The specific calculation method is as follows:
上式中的是迭代i步时油箱内气体质量，是迭代i+1步时油箱内气体质量，ti是迭代第i步时的时间，Δt是迭代时间步长；in the above formula is the mass of the gas in the fuel tank at the iterative step i, is the gas mass in the fuel tank when iterating step i+1, t i is the time when iterating step i, and Δt is the iterative time step;
结合漏泄率求解公式：Combined with the leak rate solution formula:
通过迭代求得燃油箱压力保持平衡时所用时间，即泄漏检测需要时间。The time taken for the fuel tank pressure to maintain balance is obtained through iteration, that is, the time required for leak detection.
与现有技术相比，本发明具有如下的有益效果：燃油箱蒸发排放控制系统泄漏诊断监测时，新鲜空气进入空气压缩机，空气压缩机由电机带动。其中，空气压缩机启停即电机的启停通过行车电脑ECU来控制。空气压缩机压缩后的出口气体分为两路，一路通过标准直径为0.5mm的参考泄漏测试孔，另一路则经活性碳罐后，在燃油箱泄漏诊断监测阶段经过流量计进入燃油箱完成充气工作。行车电脑ECU负责采集空气压缩机所用电机电流、燃油箱进气口流量以及燃油箱内部油箱液位、压力信号，同时控制空气压缩机运转时间。行车电脑ECU在不同的环境工况下，通过本发明能够计算并设定检测泄漏阶段空气泵向燃油泵充气所用时间，对实际检漏过程中的充气和检测时间做出精确控制，以实现蒸发排放泄漏诊断的精准性，从而使得压缩机充气检漏方法更加方便地运用于实践中。Compared with the prior art, the present invention has the following beneficial effects: during leakage diagnosis and monitoring of the fuel tank evaporative emission control system, fresh air enters the air compressor, and the air compressor is driven by a motor. Among them, the start and stop of the air compressor means the start and stop of the motor are controlled by the driving computer ECU. The outlet gas compressed by the air compressor is divided into two paths, one path passes through the reference leak test hole with a standard diameter of 0.5mm, and the other path passes through the activated carbon tank, and then enters the fuel tank through the flowmeter during the fuel tank leakage diagnosis and monitoring stage to complete the inflation Work. The driving computer ECU is responsible for collecting the motor current used by the air compressor, the flow rate of the air inlet of the fuel tank, the liquid level and pressure signal inside the fuel tank, and at the same time controlling the running time of the air compressor. Under different environmental conditions, the ECU of the driving computer can calculate and set the time for the air pump to inflate the fuel pump during the leakage detection stage, and accurately control the inflation and detection time in the actual leak detection process to achieve evaporation The accuracy of discharge leakage diagnosis makes the method of compressor air leakage detection more convenient to be used in practice.
进一步的，本发明采用四阶龙格库塔法求解燃油箱的质量守恒方程，精度较高。Further, the present invention adopts the fourth-order Runge-Kutta method to solve the mass conservation equation of the fuel tank, with high precision.
附图说明Description of drawings
图1燃油箱蒸发排放泄漏诊断检测系统示意图；Fig. 1 Schematic diagram of diagnosis and detection system for evaporative emission leakage of fuel tank;
图中：1.空气泵新鲜空气入口；2.空气压缩机；3.电机；4.0.5mm参考泄漏测试孔；5.活性碳罐；6.发动机燃烧室连接管路；7.燃油箱；8.泄漏孔；9.流量计；10.燃油进气阀；11.三通阀。In the figure: 1. Air pump fresh air inlet; 2. Air compressor; 3. Motor; 4.0.5mm reference leak test hole; 5. Activated carbon tank; 6. Engine combustion chamber connecting pipe; 7. Fuel tank; 8 . Leak hole; 9. Flow meter; 10. Fuel intake valve; 11. Three-way valve.
具体实施方式Detailed ways
下面结合附图对本发明做进一步的详细说明。The present invention will be described in further detail below in conjunction with the accompanying drawings.
参见图1，燃油箱蒸发排放控制系统泄漏诊断监测时，新鲜空气经空气泵新鲜空气入口1进入空气压缩机2，空气压缩机2由电机3带动。其中，空气压缩机2启停即电机3的启停则由行车电脑ECU来控制。空气压缩机2压缩后的出口气体经三通阀11后分为两路，一路通过0.5mm参考泄漏测试孔4，另一路则经活性碳罐5后，在燃油箱泄漏诊断监测阶段经过流量计9进入燃油箱7完成充气工作。行车电脑ECU负责采集空气压缩机2所用电机电流、燃油箱进气口流量以及燃油箱内部油箱液位及压力信号，同时控制空气压缩机2运转时间。Referring to Fig. 1, during the leakage diagnosis and monitoring of the fuel tank evaporative emission control system, fresh air enters the air compressor 2 through the fresh air inlet 1 of the air pump, and the air compressor 2 is driven by the motor 3. Wherein, the start and stop of the air compressor 2, that is, the start and stop of the motor 3 is controlled by the driving computer ECU. The outlet gas compressed by the air compressor 2 is divided into two paths after passing through the three-way valve 11. One path passes through the 0.5mm reference leak test hole 4, and the other path passes through the activated carbon tank 5 and then passes through the flow meter during the fuel tank leakage diagnosis and monitoring stage. 9 enters the fuel tank 7 to complete the inflation work. The driving computer ECU is responsible for collecting the motor current used by the air compressor 2, the flow rate of the air inlet of the fuel tank, the liquid level and pressure signal inside the fuel tank, and at the same time controlling the running time of the air compressor 2.
其具体监测策略为：Its specific monitoring strategy is as follows:
1)关闭汽车发动机，通过行车电脑其他监测装置，监测行车是否满足行车电压在9-16V、环境气压大于730hPa、发动机高于5℃、进气温度高于5℃同时波动小于12℃、汽车较长时间在部分负荷下行驶、车速介于3-150km/h之间等条件；1) Turn off the car engine, and use other monitoring devices of the driving computer to monitor whether the driving voltage is 9-16V, the ambient air pressure is greater than 730hPa, the engine is higher than 5°C, the intake air temperature is higher than 5°C and the fluctuation is less than 12°C. Driving under partial load for a long time, and the vehicle speed is between 3-150km/h;
2)如若满足步骤1中的检测执行先决条件，则气动泄漏检测模块启动运行，首先行车电脑ECU关闭燃油进气阀10，切断压缩空气和燃油蒸汽进入汽车发动机；2) If the detection execution prerequisites in step 1 are satisfied, the pneumatic leakage detection module starts to run, firstly, the driving computer ECU closes the fuel intake valve 10, and cuts off compressed air and fuel vapor from entering the automobile engine;
3)行车电脑ECU持续检测燃油箱7内蒸汽空间的温度变化情况。3) The trip computer ECU continuously detects the temperature change of the vapor space in the fuel tank 7 .
在一定时间内，燃油箱7内温度变化若超过一定值则终止泄漏检测模块。原因是温度对燃油箱7内的蒸气压有很大的影响，若检测时间段内燃油箱7内的蒸气压变化太大，会导致检测时间程序计算出现较大误差，可能导致泄漏诊断误判；Within a certain period of time, if the temperature change in the fuel tank 7 exceeds a certain value, the leak detection module will be terminated. The reason is that temperature has a great influence on the vapor pressure in the fuel tank 7. If the vapor pressure in the fuel tank 7 changes too much during the detection period, it will cause a large error in the calculation of the detection time program, which may lead to misjudgment of leakage diagnosis;
4)启动电机带动空气压缩机2运转，行车电脑ECU控制三通阀11使得压缩气体通过0.5mm参考泄漏测试孔，维持此过程10-15s，ECU记录电机电流作为泄漏检测参考电流值；4) Start the motor to drive the air compressor 2 to run, the trip computer ECU controls the three-way valve 11 to make the compressed gas pass through the 0.5mm reference leak test hole, and maintain this process for 10-15s, and the ECU records the motor current as the reference current value for leak detection;
5)标准参考电流记录后，行车电脑ECU调节三通阀11使得压缩气体通过活性碳罐5进入燃油箱7完成泄漏检测阶段。在此期间，ECU会采集进入燃油箱7的压缩空气流量以及燃油箱内的温度和蒸汽压力，通过本发明计算空气压缩机充气时间，并将其反馈到电机，以此控制实际充气时间。本发明的计算方法包括以下步骤：5) After the standard reference current is recorded, the trip computer ECU adjusts the three-way valve 11 so that the compressed gas enters the fuel tank 7 through the activated carbon tank 5 to complete the leak detection stage. During this period, the ECU will collect the compressed air flow entering the fuel tank 7 as well as the temperature and vapor pressure in the fuel tank, calculate the charging time of the air compressor through the present invention, and feed it back to the motor to control the actual charging time. Calculation method of the present invention comprises the following steps:
将待检测燃油箱简化为一开口系统，油箱空腔体积为Vb，密度为ρb，空腔内压力Pb，大气压为P0，泄漏系数为ξb，根据流体力学知识，油箱内外压差ΔP与泄漏速度vb的关系为：The fuel tank to be tested is simplified as an open system, the cavity volume of the fuel tank is V b , the density is ρ b , the pressure in the cavity is P b , the atmospheric pressure is P 0 , and the leakage coefficient is ξ b . According to the knowledge of fluid mechanics, the internal and external pressure of the fuel tank差ΔP与泄漏速度v b的关系为：
燃油箱的泄漏速度为：The leak rate of the fuel tank is:
根据燃油箱的泄漏孔径Db，则燃油箱质量泄漏率为：According to the leakage hole diameter D b of the fuel tank, the mass leakage rate of the fuel tank is:
在空气压缩机向燃油箱充气阶段，燃油箱进气率及压缩机排气率为min；在压缩机压缩过程中，进气温度T0，排气温度为Tin，根据热力过程，二者之间有如下关系：When the air compressor fills the fuel tank, the intake rate of the fuel tank and the exhaust rate of the compressor are min ; during the compression process of the compressor, the intake temperature is T 0 and the exhaust temperature is T in . According to the thermal process, the two There is the following relationship between them:
即压缩机的排气温度为：That is, the discharge temperature of the compressor is:
此处n的取值取决于压缩机实际内部压缩热力过程，n的建议取值为1-1.4。The value of n here depends on the actual internal compression thermodynamic process of the compressor, and the recommended value of n is 1-1.4.
根据工程热力学知识，温度为T的空气焓值h可以表示为：According to the knowledge of engineering thermodynamics, the enthalpy value h of air at temperature T can be expressed as:
hin＝f(T,d)；h in = f(T,d);
式中，d为每千克干空气中含有的水蒸气质量(kg/kg)。则燃油箱进气焓值可表示为：hin＝f(Tin,d)，其具体值可以查询热物性参数表或者通过其相关公式计算得出。In the formula, d is the mass of water vapor contained in each kilogram of dry air (kg/kg). Then the intake enthalpy value of the fuel tank can be expressed as: h in =f(T in ,d), and its specific value can be obtained by consulting the thermal physical property parameter table or calculating it through related formulas.
以燃油箱为开口系统，建立质量守恒方程：Taking the fuel tank as an opening system, the mass conservation equation is established:
式中，Mb和hb分别为一定充气阶段内燃油箱质量变化及焓值变化量，而Mo和ho分别为燃油箱固有的质量和焓值。同时，燃油箱质量变化量Mb也满足如下关系：In the formula, M b and h b are the mass change and enthalpy change of the fuel tank in a certain filling stage, respectively, while M o and h o are the intrinsic mass and enthalpy of the fuel tank, respectively. At the same time, the mass change Mb of the fuel tank also satisfies the following relationship:
此外，根据热力学知识，燃油箱内也有如下关系式：In addition, according to the knowledge of thermodynamics, there is also the following relationship in the fuel tank:
其中T0为气体温度。where T0 is the gas temperature.
根据以上关系式，便可以求得压缩机充气阶段，燃油箱压力保持平衡时所用的时间，也即是燃油箱泄漏检测建议所用时间值。具体求解步骤如下：According to the above relational formula, the time taken for the pressure of the fuel tank to be balanced during the charging stage of the compressor can be obtained, that is, the recommended time value for fuel tank leak detection. The specific solution steps are as follows:
对于微分方程求解，采用四阶龙格库塔法求解标准质量守恒方程，即：For differential equation solving, the fourth-order Runge-Kutta method is used to solve the standard mass conservation equation, namely:
结合漏泄率求解公式：Combined with the leak rate solution formula:
通过迭代求得燃油箱压力保持平衡时所用时间，即泄漏检测需要时间。The time taken for the fuel tank pressure to maintain balance is obtained through iteration, that is, the time required for leak detection.
6)在泄漏检测阶段记录电机电流随时间变化过程，并与基准泄漏检测参考电流值进行对比。如果与先前测得的参考电流相比识别到电流有所下降，这就是在燃油系统中存在泄漏的信号；如果超过参考电流时表明系统中没有泄漏。6) During the leakage detection stage, record the change process of the motor current with time, and compare it with the reference current value of the baseline leakage detection. If a drop in current is detected compared to a previously measured reference current, this is a sign of a leak in the fuel system; if the reference current is exceeded, there is no leak in the system.
以上内容对本发明的目的、技术方案和有益效果进行了详细的说明，所应理解的是，以上所述仅为本发明的一种具体实施方式，并不用于限定本发明的保护范围。凡在本发明的精神和原则之内，所做的任何修改、等同替换及改进等，均应包含在本发明的包含范围之内。The above content has described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the protection scope of the present invention. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the scope of the present invention.
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