CN112832933B - Method for detecting evaporation leakage of automobile fuel - Google Patents

Method for detecting evaporation leakage of automobile fuel Download PDF

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CN112832933B
CN112832933B CN202110167572.9A CN202110167572A CN112832933B CN 112832933 B CN112832933 B CN 112832933B CN 202110167572 A CN202110167572 A CN 202110167572A CN 112832933 B CN112832933 B CN 112832933B
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delta
fuel vapor
sampling
leakage
fuel
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CN112832933A (en
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朱卫萍
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/08—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding fuel vapours drawn from engine fuel reservoir
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
    • G01M3/32—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Examining Or Testing Airtightness (AREA)

Abstract

The method for detecting the evaporation and leakage of the fuel oil of the automobile comprises the steps of measuring the temperature and the air pressure of the fuel oil vapor of a closed fuel tank or a fuel tank cover, setting a sampling time interval delta s, setting the moment P2 of the detection sampling end point as a fixed value, measuring the temperature of the pressurized fuel oil vapor, calculating the leakage amount of the unit volume of the fuel oil vapor in the state of the detection sampling end point according to a gas state equation and the unit volume leakage rate delta limit value of the fuel oil vapor in the state of the specified standard state, calculating the air pressure difference delta P to obtain the air pressure P1 at the moment of the sampling start point, or after the delta P is obtained, setting the P1 as the fixed value, calculating P2= P1-delta P, eliminating the influence of the temperature and the volume of the fuel oil vapor on the detection, and accurately detecting and evaluating the leakage degree of the fuel oil vapor of the fuel tank or the fuel tank cover in the unified standard state.

Description

Method for detecting evaporation leakage of automobile fuel
Technical Field
The method for detecting the evaporation leakage of the fuel of the automobile determines the pressure difference of the fuel vapor leakage and detects the leakage degree of an oil tank or an oil tank cover according to the single volume fuel vapor leakage rate limit value under the specified standard state, and belongs to the technical field of automobile emission detection.
Background
In order to prevent fuel vapor of an oil tank from overflowing to the atmosphere to cause pollution, a fuel vapor purification system of the oil tank is installed on a gasoline vehicle, a vapor valve, an active carbon tank storage device and the like are usually arranged on the oil tank, an air valve is usually arranged on a fuel tank cover, and large fuel vapor leakage can be generated after the sealing performance of a valve body is reduced. The method for detecting the evaporation leakage of the fuel oil of the automobile overcomes the defects of the prior art, and determines the detection pressure difference of the fuel oil vapor leakage by adopting an ideal gas state equation and a specified single volume fuel oil vapor leakage rate limit value under a standard state.
Disclosure of Invention
The pressure and temperature of fuel vapor in an automobile fuel tank are not large, the change of the pressure and temperature in the leakage process is small, the compression coefficient of the fuel vapor can be set to be 1, the change of the state of the fuel vapor is approximately taken as the change of an ideal gas state, and the change of the state of the fuel vapor can be taken as the change of an isothermal gas state within a short sampling time interval.
The temperature to, the pressure Po of the detected ambient conditions is measured, and during the pressure drop of the leakage of pressurized fuel vapor, a sampling time interval Δ s is defined, which can be chosen in the range 5s to 30s, or equal to a defined time of the leakage rate limit. The volume V1, the pressure P1, and the temperature t1 of the fuel vapor at the starting point of sampling, the volume V2, the pressure P2, the temperature t2, and the leakage volume Δ V at the ending point of sampling, and the temperature unit "c" may be set to t1= t2, and the fuel vapor state at the starting point of sampling and the ending point of sampling may be set to an isothermal gas state equation V1 × P1= V2 × P2, and the pressure difference Δ P = P1-P2= P2 × V2/V1-P2= [ (V1 + Δ V)/V1-1 ] × P2= P2 × Δ Y/V1, so that Δ Y/V1 is the leakage amount of the fuel vapor per unit volume, and V1 may be detected without measuring V1, and Δ V/V1 is proportional to Δ P when P2 is a constant value.
The limit value delta = Vb/deltas of the fuel vapor unit volume leakage rate in the standard state can be specified, vb is the fuel vapor unit volume leakage amount in the standard state, P2 is set to be a fixed value, the air pressure in the standard state is Pb, and the temperature is tb. Detecting the leakage quantity V2b of the unit volume of the fuel steam at the sampling termination point moment under the state, according to the gas state equation: vb × Pb/(273 + tb) = V2b × P2/(273 + tb 2), where the division V2b is an unknown quantity, and other parameters are measured values and known values, and the air pressure difference Δ P = P2 × V2b and P1= P2+ P2 × V2b in the detection state corresponding to the δ limit value of V2b can be calculated, and Δ P of the δ limit value changes with the temperature of the fuel vapor in the unified standard state.
The method for detecting the evaporation leakage of the automobile fuel is characterized by comprising the following steps: setting a sampling time interval deltas, measuring the temperature and the pressure of fuel vapor after the detected closed fuel tank or the pressurized fuel tank cover, setting the pressure P2 of the fuel vapor at the sampling termination point as a fixed value under the detection state, and setting the pressure difference deltaP = P1-P2= P2 xV 2/V1-P2= [ (V1 + deltaY)/V1-1 ] × P2= P2 xdeltaV/V1 = P2 xV 2b according to an isothermal gas state equation V1 xP 1= V2 xP 2, wherein the volume of the fuel vapor at the sampling termination point is V1 and the pressure is P1, the volume of the fuel vapor at the sampling termination point is V2, the pressure is P2, the temperature is t2, the leakage volume is deltaY, and the leakage quantity of the unit volume of the fuel vapor is V2b = deltaV/V1; setting a leakage rate limit value of the unit volume of the fuel vapor under a standard state to be delta, setting the leakage rate limit value of the unit volume of the fuel vapor under the standard state to be Vb, delta = Vb/deltas and Vb = delta x deltas at the sampling end point, wherein the pressure is Pb, the temperature is tb, and the leakage rate of the unit volume of the fuel vapor under the standard state is Vb; according to the gas state equation: vb × Pb/(273 + tb) = (δ × Δ s) × Pb/(273 + tb) = V2b × P2/(273 + tb), V2b is calculated, and the air pressure P1= P2+ Δ P = P2+ P2 × V2b at the sampling starting point time in the detection state corresponding to the standard state limit value δ is obtained; and taking the air pressure as P1 as the sampling starting point time, determining that the unit volume leakage rate delta j of the detected fuel steam in the standard state is less than or equal to the delta limit value when the fuel steam air pressure Pj at the sampling ending point time is more than or equal to P2 after the sampling time interval delta s, and determining that the delta j is more than the delta limit value if the Pj is less than P2, wherein the detection is unqualified. Has the following technical advantages.
1. The volume V1 of the fuel vapor is not required to be measured, the influence of the temperature and the volume of the fuel vapor on the detection is eliminated, and the leakage degree is accurately detected and evaluated under a unified standard state. The delta limit value of the detected oil tank or the oil tank cover is determined to correspond to the air pressure difference, and then the actual air pressure difference is detected.
2. During detection, a point P1 is used as a sampling starting point, and the air pressure Pj, the leakage amount Vjb per unit volume, the air pressure difference Δ Pj = Pj × Vjb, vjb = Δ Pj/Pj in a state of a sampling ending point, the air pressure difference Δ P = P2 × V2b, and V2b = Δ P/P2 are set as limit values. When Pj is more than or equal to P2, delta Pj/Pj is less than or equal to delta P/P2, so that Vjb is less than or equal to V2b, the unit volume leakage rate delta j of the fuel steam in the standard state is less than or equal to a delta limit value, the detection is qualified, otherwise, when Pj is less than P2, delta j is more than the delta limit value, the detection is unqualified.
3. When the air pressure difference delta Pj = Pj multiplied by Vjb of the detected oil tank or oil tank cover, the unit volume leakage amount Vjb = delta Pj/Pj of the fuel steam in the detected sampling termination point time state is obtained, and the unit volume leakage amount Vb and the leakage rate delta j of the fuel steam in the standard state can be obtained according to the gas state equation, wherein Vb multiplied by Pb/(273 + tb) = Vjb multiplied by Pj/(273 + tj), and Pj and tj are the pressure and the temperature of the fuel steam in the detected sampling termination point time state.
Detailed Description
Taking the fuel vapor leakage of a fuel tank and a fuel tank cover of a gasoline passenger car as an example, the specific embodiment of the method for detecting the fuel vapor leakage of the car is explained, wherein the temperature tb =23 ℃ and the air pressure Pb =101.35kPa in the standard state are set, the detection sampling time interval Delta s =10s, and the leakage rate limit value Delta =60 mL/(liter & min) =1 mL/(liter & s) =0.001 mL/(mL & s) and Vb = Delta & ltx & gts =0.001 × 10=0.01mL/mL per liter of fuel vapor volume in the standard state are defined.
1. Detecting fuel vapor leakage of a fuel tank, detecting the ambient air pressure Po =101.1kPa, the fuel vapor temperature t2=45 ℃, setting the air pressure P2= Po +2.3=101.1+2.3=103.4kPa as a fixed value at the sampling termination point of detection, and according to the gas state equation: vb × Pb/(273 + tb) = V2b × P2/(273 + t 2), 0.01 × 101.35/(273 + 23) = V2b × 103.4/(273 + 45), V2b =0.01053 is solved, and the detected air pressure difference Δ P = P2 × V2b =103.4 × 0.01053=1.0888kpa =1089pa and P1=103.4 +1.089=104.489kpa can be obtained.
If the fuel vapor pressure P1=104.489 point of the detected fuel tank is used as the sampling starting point time, the fuel vapor pressure Pj =103.8 at the sampling ending point time is larger than P2=103.4, and the detection is qualified.
Calculate Vjb = Δ Pj/Pj = (104.489-103.8)/103.8 =0.00664 as gas equation of state: vb × 101.35/(273 + 23) =0.00664 × 103.8/(273 + 45), vb =0.00633mL/mL =6.33 mL/liter, detected δ j = Vb/Δ s =6.33/10= 0.633ml/(liter · s) =37.98 mL/(liter · min), and the detection is qualified when the value is less than the limit value δ =60 mL/(liter · min).
2. Detecting fuel vapor leakage of a fuel tank cover, detecting environmental pressure Po =101.8kPa, fuel vapor temperature t2=15 ℃, setting the air pressure P2= Po +6.0=101.8+6.0=107.8kPa as a fixed value at the sampling termination point of detection, and according to a gas state equation: vb × Pb/(273 + tb) = V2b × P2/(273 + t 2), 0.01 × 101.35/(273 + 23) = V2b × 107.8/(273 + 15), solved into Y2b =0.009148, and the available limit air pressure difference Δ P = P2 × V2b =107.8 × 0.009148=0.9861kpa =986pa, and P1=107.8+0.986=108.79kpa. Measurement started from P1, pj =107.3kPa < 107.8kPa, and failure was detected.
The method for detecting the evaporation leakage of the automobile fuel eliminates the influence of the temperature and the volume of the fuel vapor on the detection, accurately measures and evaluates the fuel vapor in a unified standard state, and has the advantages of accurate and quick detection and the like.

Claims (1)

1. The method for detecting the evaporation leakage of the automobile fuel is characterized by comprising the following steps: setting a sampling time interval deltas, measuring the temperature and the pressure of fuel vapor after the detected closed fuel tank or the pressurized fuel tank cover, setting the pressure P2 of the fuel vapor at the sampling termination point as a fixed value under the detection state, and setting the pressure difference deltaP = P1-P2= P2 xV 2/V1-P2= [ (V1 + deltaV)/V1-1 ] × P2= P2 xdeltaV/V1 = P2 xV 2b according to an isothermal gas state equation V1 xP 1= V2 xP 2, wherein the volume of the fuel vapor at the sampling termination point is V1 and the pressure is P1, the volume of the fuel vapor at the sampling termination point is V2, the pressure is P2, the temperature is t2, the leakage volume is deltaV, and the leakage quantity of the unit volume of the fuel vapor is V2b = deltaV/V1; setting a fuel vapor unit volume leakage rate limit value delta under a standard state, setting a standard state fuel vapor unit volume leakage amount Vb at a sampling termination point moment, wherein the pressure is Pb, the temperature is tb, and delta = Vb/delta s; according to the gas state equation: vb × Pb/(273 + tb) = (δ × Δ s) × Pb/(273 + tb) = V2b × P2/(273 + tb 2), V2b is calculated, and the air pressure P1= P2+ Δ P = P2+ P2 × V2b at the sampling starting point time in the detection state corresponding to the standard state limit value δ is obtained; and taking the air pressure P1 as the sampling starting point time, determining that the fuel vapor pressure Pj at the sampling end point time is more than or equal to P2 after the sampling time interval deltas, determining that the unit volume leakage rate delta j of the detected fuel vapor in the standard state is less than or equal to a delta limit value, detecting the fuel vapor to be qualified, and determining that delta j is more than the delta limit value if Pj is less than P2, and detecting the fuel vapor to be unqualified.
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JP4337374B2 (en) * 2003-02-07 2009-09-30 三菱電機株式会社 Transpiration fuel gas leak detector
JP2005299394A (en) * 2004-04-06 2005-10-27 Mitsubishi Electric Corp Evaporating fuel gas leak detection device
JP4715427B2 (en) * 2005-09-28 2011-07-06 日産自動車株式会社 Leak diagnostic device for evaporative fuel processing system
JP5724983B2 (en) * 2012-10-11 2015-05-27 株式会社デンソー Fuel vapor leak detection device
JP5617951B2 (en) * 2013-04-08 2014-11-05 トヨタ自動車株式会社 Evaporative leak diagnosis device
CN106500933B (en) * 2016-12-27 2019-06-04 上海汽车集团股份有限公司 High pressure resistant fuel tank leakage diagnosing method
CN112031946B (en) * 2020-09-08 2023-04-07 广州汽车集团股份有限公司 Fault diagnosis method for fuel evaporation system

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