A gas-liquid ratio control method for secondary oil gas recovery of a fuel dispenser

Abstract

The present application relates to gas-liquid ratio control, in particular to a kind of gas-liquid ratio control method of secondary oil gas recovery of oil dispenser, and whether oil dispenser reaches stable state is judged when calculating cumulative oil quantity and cumulative gas quantity when oil dispenser starts to fuel;When oil dispenser reaches stable state, target average gas flow is calculated, and target average gas flow is used as target flow, and the corresponding PWM out Is obtained;Gas-liquid ratio controller controls valve or frequency conversion pump using PWM out , and the updated average oil flow value, average gas flow value are calculated;According to average gas flow value, PWM out Is iteratively updated, and based on updated PWM out , valve or frequency conversion pump is controlled;The technical scheme provided by the present application can effectively overcome the defects that environmental protection requirements cannot be met due to the larger error of gas-liquid ratio result in prior art.

Description

Technical Field

[0001] This invention relates to gas-liquid ratio control, and more specifically to a gas-liquid ratio control method for secondary oil and gas recovery in a fuel dispenser. Background Technology

[0002] Petroleum products generate emissions during production, storage, transportation, sales, and use, polluting the environment and wasting resources. Gas stations, as locations for oil storage and sales, have always been a key focus of environmental protection departments for their oil and gas emissions. Currently, most gas stations in my country have completed secondary oil and gas recovery upgrades, enabling them to recover escaping oil and gas near the fuel tank opening into the gas phase space of the underground tank during refueling via an oil and gas recovery vacuum pump. The ratio between the recovered gas volume and the refueling volume is called the gas-liquid ratio, a crucial parameter reflecting the equipment's operating status. According to GB 20952-2007 "Emission Standard for Air Pollutants from Gas Stations," the gas-liquid ratio range for gas station oil and gas recovery systems should be 1.0 to 1.2.

[0003] Currently, there are two main methods for controlling the gas-liquid ratio: The first method involves manually adjusting the return gas flow rate using coarse and fine adjustment knobs. However, this method has a significant drawback: instability. Changes in on-site conditions, such as variations in oil flow rate, can lead to severe imbalances in the gas-liquid ratio. The second method uses closed-loop PID control. This method has a slower stabilization time, especially in scenarios where the oil volume changes frequently during refueling, often resulting in the gas-liquid ratio failing to meet standards at the end of refueling. Currently, in environmental comparisons, multi-parameter oil and gas recovery analyzers are commonly used to test whether on-site oil and gas recovery meets standards. Most of these analyzers use volumetric gas flow meters, which, due to inertia, can cause measurement deviations in frequently changing pulsating flows. Ultimately, this manifests as the online gas-liquid ratio result after PID control meeting requirements, but third-party testing results showing non-compliance.

[0004] Currently, electronic gas-liquid ratio regulating devices are divided into two types: one is a fixed-frequency vacuum pump, which controls the return gas resistance by controlling the opening of an electromagnetic proportional valve, thereby regulating the gas-liquid ratio; the other is a variable-frequency vacuum pump, which changes the pumping flow rate by controlling the operating frequency of the variable-frequency vacuum pump, thus achieving the purpose of regulating the gas-liquid ratio. Based on these two types of pumps, this application proposes a gas-liquid ratio control method based on target control. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings of the existing technology, the present invention provides a gas-liquid ratio control method for secondary oil and gas recovery of fuel dispensers, which can effectively overcome the defects of the existing technology that cannot meet environmental protection requirements due to large errors in the gas-liquid ratio results.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for controlling the gas-liquid ratio in secondary vapor recovery of a fuel dispenser, comprising the following steps:

[0010] S1. Calculate the cumulative fuel volume and cumulative gas volume when the fuel dispenser starts refueling, and determine whether the fuel dispenser has reached a stable state;

[0011] S2. When the fuel dispenser reaches a stable state, calculate the target average gas flow rate, use the target average gas flow rate as the target flow rate, and obtain the corresponding output pulse width modulation (PWM). out ;

[0012] S3, the gas-liquid ratio controller utilizes output pulse width modulation (PWM). out Control the valves or variable frequency pumps, and calculate the updated average oil flow rate and average air flow rate;

[0013] S4. Modulate the output pulse width modulation (PWM) based on the average airflow value. out Perform iterative updates and modulate the PWM based on the updated output pulse width. out To control valves or variable frequency pumps.

[0014] Preferably, in step S1, calculating the cumulative fuel volume and cumulative gas volume when the fuel dispenser starts refueling includes:

[0015] When the first oil pulse is detected from the fuel dispenser, it is considered the start of refueling. The gas-liquid ratio controller calculates the cumulative oil quantity V based on the number of oil pulses and the equivalent value of the oil pulses. oil-total Simultaneously, based on the number of gas pulses and the equivalent value of the gas pulses, the cumulative oil quantity V is calculated. gas-total .

[0016] Preferably, determining whether the refueling machine has reached a stable state in step S1 includes:

[0017] When V oil-total ≤V oil-th At that time, the gas-liquid ratio controller outputs a default pulse width modulation (PWM) signal. default Control the valve or variable frequency pump, wait for the oil and gas flow to stabilize, and collect oil and gas pulses during the waiting process;

[0018] When V oil-total >V oil-th At that time, calculate the average oil flow rate. Average airflow value and the mean square deviation of oil flow rate And based on the mean square deviation of oil flow rate Determine if the fuel dispenser has reached a stable state;

[0019] Among them, V oil-th This is the cumulative oil consumption threshold.

[0020] Preferably, in step S2, when the refueling machine reaches a steady state, the target average gas flow rate is calculated, including:

[0021] S21. When the fuel dispenser reaches a stable state, calculate the cumulative oil flow rate Q. O Cumulative gas flow rate Q G Assume V oil-end The target remaining cumulative gas flow rate Q is calculated based on the ideal gas-liquid ratio target value j, representing the cumulative fuel volume at the end of refueling. GT :

[0022]

[0023] S22. When the fuel dispenser is in a stable state, the average fuel flow rate value will be... The remaining time T is calculated using the reference oil flow rate value as the initial reference for the calculation of the remaining time. left :

[0024]

[0025] S23. Further calculations yield the target average gas flow rate V. GT :

[0026] .

[0027] Preferably, the cumulative fuel volume V at the end of the refueling process... oil-end The initial value is greater than 10L, when the cumulative oil flow rate Q O Greater than the accumulated fuel volume V at the end of refueling oil-end If refueling is not yet finished, the accumulated fuel volume V at the end of refueling will be recorded. oil-end Add 5L more fuel until refueling is complete.

[0028] Preferably, in step S2, the target average airflow rate is used as the target flow rate to obtain the corresponding output pulse width modulation (PWM). out ,include:

[0029] S24. Construct an empirical operating curve for a valve or variable frequency pump based on empirical flow rate and empirical PWM value, and correct the actual flow rate corresponding to each PWM interval of the empirical operating curve to obtain the corrected empirical operating curve.

[0030] S25, Target average gas flow rate V GT As the target traffic V target The corresponding output pulse width modulation (PWM) is calculated based on S24. out .

[0031] Preferably, in S24, an empirical operating curve for the valve or variable frequency pump based on empirical flow rate and empirical PWM value is constructed, and the actual flow rate corresponding to each PWM interval of the empirical operating curve is corrected to obtain a corrected empirical operating curve, including:

[0032] S241. Establish an experience flow V1, V2, ..., V N Compared with empirical PWM values ​​PWM1, PWM2, ..., PWM N The two-dimensional table uses the empirical PWM value as the horizontal axis and the empirical flow rate as the vertical axis. Each flow rate interval is obtained through linear interpolation.

[0033] S242, Based on target traffic V target The corresponding flow range can be obtained by looking up the table. The PWM values ​​corresponding to the endpoints of this flow range are respectively PWM i PWM i+1 The target flow rate V is calculated using linear interpolation. target Corresponding output pulse width modulation (PWM) out :

[0034]

[0035] S243, Gas-Liquid Ratio Controller Output Pulse Width Modulation (PWM) out Control the valve or variable frequency pump, and wait for T0 seconds for airflow stabilization. A gas flow meter installed on the pipeline collects the instantaneous gas flow rate at N points, and calculates the average gas flow rate V at these N points. average As output pulse width modulation (PWM) out The corresponding actual traffic;

[0036] S244, Based on target traffic V target and average gas flow rate V average Calculated flow range Correction factor k:

[0037]

[0038] And based on the correction factor k, V i V i+1 Corrected to kV respectively i kV i+1 ;

[0039] S245. After multiple refuelings, the change in oil flow rate of the fuel dispenser will cause the target flow rate V to decrease. target The difference is used to continuously correct the actual flow rate corresponding to each PWM interval of the empirical working curve, thus obtaining the corrected empirical working curve.

[0040] Preferably, the gas-liquid ratio controller in S3 utilizes output pulse width modulation (PWM). out Control valves or variable frequency pumps, and calculate updated average oil flow rate and average air flow rate values, including:

[0041] Gas-liquid ratio controller outputs pulse width modulation (PWM) out Control the valve or variable frequency pump and wait for T0 seconds for airflow stabilization. The gas-liquid ratio controller simultaneously collects the instantaneous oil flow rate and instantaneous gas flow rate at N points and calculates the updated average oil flow rate value. Average airflow value .

[0042] Preferably, in S4, the output pulse width modulation (PWM) is based on the average air flow rate value. out Perform iterative updates and modulate the PWM based on the updated output pulse width. out Controlling valves or variable frequency pumps includes:

[0043] When the average air flow rate At that time, the gas-liquid ratio controller maintains the current output pulse width modulation (PWM). out Control valves or variable frequency pumps;

[0044] When the average air flow rate At that time, return to S2 to adjust the output pulse width modulation (PWM). out Perform iterative updates to calculate the updated output pulse width modulation (PWM). out The gas-liquid ratio controller outputs updated output pulse width modulation (PWM). out Control valves or variable frequency pumps;

[0045] Where a and b represent the control average gas flow rate values, respectively. The lower limit coefficient and the upper limit coefficient.

[0046] (III) Beneficial Effects

[0047] Compared with the prior art, the gas-liquid ratio control method for secondary oil and gas recovery of fuel dispensers provided by this invention adopts a target-based control algorithm. In the entire control process, the PWM value is output to the target value in a step-like manner, which reduces the back-and-forth oscillation of the gas-liquid ratio during the control process. Ultimately, it achieves the purpose of reducing the deviation between the control result and the third-party test result, which greatly improves the pass rate of the on-site gas-liquid ratio test result, and also meets the environmental protection requirements. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0049] Figure 1 This is a schematic diagram of the process of the present invention;

[0050] Figure 2 This is a real-time control curve of the gas-liquid ratio at the site.

[0051] Figure 3 This is a comparison chart between the gas-liquid ratio results obtained using the technical solution of this application and the results of third-party testing;

[0052] Figure 4 This is a comparison chart between the gas-liquid ratio results obtained using traditional closed-loop PID control and the results from third-party testing. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] A method for controlling the gas-liquid ratio in secondary vapor recovery of fuel dispensers, such as... Figure 1 As shown, S1 calculates the cumulative oil volume and cumulative gas volume when the fuel dispenser starts refueling, and determines whether the fuel dispenser has reached a stable state.

[0055] 1) Calculate the cumulative fuel volume and cumulative gas volume when the fuel dispenser starts dispensing, including:

[0056] When the first oil pulse is detected from the fuel dispenser, it is considered the start of refueling. The gas-liquid ratio controller calculates the cumulative oil quantity V based on the number of oil pulses and the equivalent value of the oil pulses. oil-total Simultaneously, based on the number of gas pulses and the equivalent value of the gas pulses, the cumulative oil quantity V is calculated. gas-total .

[0057] 2) Determine if the fuel dispenser has reached a stable state, including:

[0058] When V oil-total ≤V oil-th At that time, the gas-liquid ratio controller outputs a default pulse width modulation (PWM) signal. defaultControl the valve or variable frequency pump, wait for the oil and gas flow to stabilize, and collect oil and gas pulses during the waiting process;

[0059] When V oil-total >V oil-th At that time, calculate the average oil flow rate. Average airflow value and the mean square deviation of oil flow rate And based on the mean square deviation of oil flow rate Determine if the fuel dispenser has reached a stable state;

[0060] Among them, V oil-th This is the cumulative oil consumption threshold.

[0061] S2. When the fuel dispenser reaches a stable state, calculate the target average gas flow rate, use the target average gas flow rate as the target flow rate, and obtain the corresponding output pulse width modulation (PWM). out .

[0062] 1) Calculate the target average gas flow rate when the fuel dispenser reaches a steady state, including:

[0063] S21. When the fuel dispenser reaches a stable state, calculate the cumulative oil flow rate Q. O Cumulative gas flow rate Q G Assume V oil-end The target remaining cumulative gas flow rate Q is calculated based on the ideal gas-liquid ratio target value of 1.1, representing the cumulative fuel volume at the end of refueling. GT :

[0064]

[0065] S22. When the fuel dispenser is in a stable state, the average fuel flow rate value will be... The remaining time T is calculated using the reference oil flow rate value as the initial reference for the calculation of the remaining time. left :

[0066]

[0067] S23. Further calculations yield the target average gas flow rate V. GT :

[0068] .

[0069] Based on third-party comparison experience, the refueling volume during the gas-liquid ratio check is 15-16L. Therefore, the cumulative oil volume V at the end of refueling will be used as the reference. oil-end The initial value is set to 16L, and the cumulative oil flow rate Q is... O Greater than the accumulated fuel volume V at the end of refueling oil-end If refueling is not yet finished, the accumulated fuel volume V at the end of refueling will be recorded.oil-end Add 5L more until refueling is complete.

[0070] 2) Using the target average airflow rate as the target flow rate, obtain the corresponding output pulse width modulation (PWM). out ,include:

[0071] S24. Construct an empirical operating curve for a valve or variable frequency pump based on empirical flow rate and empirical PWM value, and correct the actual flow rate corresponding to each PWM interval of the empirical operating curve to obtain the corrected empirical operating curve.

[0072] S25, Target average gas flow rate V GT As the target traffic V target The corresponding output pulse width modulation (PWM) is calculated based on S24. out .

[0073] Specifically, an empirical operating curve for a valve or variable frequency pump is constructed based on empirical flow rate and empirical PWM value. The actual flow rate corresponding to each PWM interval of the empirical operating curve is then corrected to obtain the corrected empirical operating curve, including:

[0074] S241. Establish an experience flow V1, V2, ..., V N Compared with empirical PWM values ​​PWM1, PWM2, ..., PWM N The two-dimensional table uses the empirical PWM value as the horizontal axis and the empirical flow rate as the vertical axis. Each flow rate interval is obtained through linear interpolation.

[0075] S242, Based on target traffic V target The corresponding flow range can be obtained by looking up the table. The PWM values ​​corresponding to the endpoints of this flow range are respectively PWM i PWM i+1 The target flow rate V is calculated using linear interpolation. target Corresponding output pulse width modulation (PWM) out :

[0076]

[0077] S243, Gas-Liquid Ratio Controller Output Pulse Width Modulation (PWM) out Control the valve or variable frequency pump, and wait for T0 seconds for airflow stabilization. A gas flow meter installed on the pipeline collects the instantaneous gas flow rate at N points, and calculates the average gas flow rate V at these N points. average As output pulse width modulation (PWM) out The corresponding actual traffic;

[0078] S244, Based on target traffic V target and average gas flow rate Vaverage Calculated flow range Correction factor k:

[0079]

[0080] And based on the correction factor k, V i V i+1 Corrected to kV respectively i kV i+1 ;

[0081] S245. After multiple refuelings, the change in oil flow rate of the fuel dispenser will cause the target flow rate V to decrease. target The difference is used to continuously correct the actual flow rate corresponding to each PWM interval of the empirical working curve, thus obtaining the corrected empirical working curve.

[0082] S3, the gas-liquid ratio controller utilizes output pulse width modulation (PWM). out Control valves or variable frequency pumps, and calculate updated average oil flow rate and average air flow rate values, specifically including:

[0083] Gas-liquid ratio controller outputs pulse width modulation (PWM) out Control the valve or variable frequency pump and wait for T0 seconds for airflow stabilization. The gas-liquid ratio controller simultaneously collects the instantaneous oil flow rate and instantaneous gas flow rate at N points and calculates the updated average oil flow rate value. Average airflow value .

[0084] S4. Modulate the output pulse width modulation (PWM) based on the average airflow value. out Perform iterative updates and modulate the PWM based on the updated output pulse width. out Controlling valves or variable frequency pumps specifically includes:

[0085] When the average air flow rate At that time, the gas-liquid ratio controller maintains the current output pulse width modulation (PWM). out Control valves or variable frequency pumps;

[0086] When the average air flow rate At that time, return to S2 to adjust the output pulse width modulation (PWM). out Perform iterative updates to calculate the updated output pulse width modulation (PWM). out The gas-liquid ratio controller outputs updated output pulse width modulation (PWM). out Control valves or variable frequency pumps.

[0087] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the gas-liquid ratio in fuel dispenser vapor recovery, characterized in that: Includes the following steps: S1. Calculate the cumulative fuel volume and cumulative gas volume when the fuel dispenser starts refueling, and determine whether the fuel dispenser has reached a stable state; S2. When the fuel dispenser reaches a stable state, calculate the target average gas flow rate, use the target average gas flow rate as the target flow rate, and obtain the corresponding output pulse width modulation (PWM). out ; S3, the gas-liquid ratio controller utilizes output pulse width modulation (PWM). out Control the valves or variable frequency pumps, and calculate the updated average oil flow rate and average air flow rate; S4. Modulate the output pulse width modulation (PWM) based on the average airflow value. out Perform iterative updates and modulate the PWM based on the updated output pulse width. out Control valves or variable frequency pumps; In S2, the target average airflow rate is used as the target flow rate to obtain the corresponding output pulse width modulation (PWM). out ,include: S24. Construct an empirical operating curve for a valve or variable frequency pump based on empirical flow rate and empirical PWM value, and correct the actual flow rate corresponding to each PWM interval of the empirical operating curve to obtain the corrected empirical operating curve, specifically including: S241. Establish an experience flow V1, V2, ..., V N Compared with empirical PWM values ​​PWM1, PWM2, ..., PWM N The two-dimensional table uses the empirical PWM value as the horizontal axis and the empirical flow rate as the vertical axis. Each flow rate interval is obtained through linear interpolation. S242, Based on target traffic V target The corresponding flow range can be obtained by looking up the table. The PWM values ​​corresponding to the endpoints of this flow range are respectively PWM i PWM i+1 The target flow rate V is calculated using linear interpolation. target Corresponding output pulse width modulation (PWM) out : S243, Gas-Liquid Ratio Controller Output Pulse Width Modulation (PWM) out Control the valve or variable frequency pump, and wait for T0 seconds for airflow stabilization. A gas flow meter installed on the pipeline collects the instantaneous gas flow rate at N points, and calculates the average gas flow rate V at these N points. average As output pulse width modulation (PWM) out The corresponding actual traffic; S244, Based on target traffic V target and average gas flow rate V average Calculated flow range Correction factor k: And based on the correction factor k, V i V i+1 Corrected to kV respectively i kV i+1 ; S245. After multiple refuelings, the change in oil flow rate of the fuel dispenser will cause the target flow rate V to decrease. target The difference is used to continuously correct the actual flow rate corresponding to each PWM interval of the empirical working curve, so as to obtain the corrected empirical working curve. S25, Target average gas flow rate V GT As the target traffic V target The corresponding output pulse width modulation (PWM) is calculated based on S24. out .

2. The gas-liquid ratio control method for fuel dispenser vapor recovery according to claim 1, characterized in that: S1 calculates the cumulative fuel volume and cumulative gas volume when the fuel dispenser starts refueling, including: When the first oil pulse is detected from the fuel dispenser, it is considered the start of refueling. The gas-liquid ratio controller calculates the cumulative oil quantity V based on the number of oil pulses and the equivalent value of the oil pulses. oil-total Simultaneously, based on the number of gas pulses and the equivalent value of the gas pulses, the cumulative oil quantity V is calculated. gas-total .

3. The gas-liquid ratio control method for fuel dispenser vapor recovery according to claim 2, characterized in that: S1 determines whether the refueling machine has reached a stable state, including: When V oil-total ≤V oil-th At that time, the gas-liquid ratio controller outputs a default pulse width modulation (PWM) signal. default Control the valve or variable frequency pump, wait for the oil and gas flow to stabilize, and collect oil and gas pulses during the waiting process; When V oil-total >V oil-th At that time, calculate the average oil flow rate. Average airflow value and the mean square deviation of oil flow rate And based on the mean square deviation of oil flow rate Determine if the fuel dispenser has reached a stable state; Among them, V oil-th This is the cumulative oil consumption threshold.

4. The gas-liquid ratio control method for fuel dispenser vapor recovery according to claim 3, characterized in that: In S2, when the refueling machine reaches a steady state, the target average gas flow rate is calculated, including: S21. When the fuel dispenser reaches a stable state, calculate the cumulative oil flow rate Q. O Cumulative gas flow rate Q G Assume V oil-end The target remaining cumulative gas flow rate Q is calculated based on the ideal gas-liquid ratio target value j, representing the cumulative fuel volume at the end of refueling. GT : S22. When the fuel dispenser is in a stable state, the average fuel flow rate value will be... The remaining time T is calculated using the reference oil flow rate value as the initial reference for the calculation of the remaining time. left : S23. Further calculations yield the target average gas flow rate V. GT : 。 5. The gas-liquid ratio control method for fuel dispenser vapor recovery according to claim 4, characterized in that: The cumulative fuel volume V at the end of refueling oil-end The initial value is greater than 10L, when the cumulative oil flow rate Q O Greater than the accumulated fuel volume V at the end of refueling oil-end If refueling is not yet finished, the accumulated fuel volume V at the end of refueling will be recorded. oil-end Add 5L more until refueling is complete.

6. The gas-liquid ratio control method for fuel dispenser vapor recovery according to claim 1, characterized in that: The gas-liquid ratio controller in S3 utilizes output pulse width modulation (PWM). out Control valves or variable frequency pumps, and calculate updated average oil flow rate and average air flow rate values, including: Gas-liquid ratio controller outputs pulse width modulation (PWM) out Control the valve or variable frequency pump and wait for T0 seconds for airflow stabilization. The gas-liquid ratio controller simultaneously collects the instantaneous oil flow rate and instantaneous gas flow rate at N points and calculates the updated average oil flow rate value. Average airflow value .

7. The gas-liquid ratio control method for fuel dispenser vapor recovery according to claim 6, characterized in that: S4 modulates the output pulse width modulation (PWM) based on the average airflow rate. out Perform iterative updates and modulate the PWM based on the updated output pulse width. out Controlling valves or variable frequency pumps includes: When the average air flow rate At that time, the gas-liquid ratio controller maintains the current output pulse width modulation (PWM). out Control valves or variable frequency pumps; When the average air flow rate At that time, return to S2 to adjust the output pulse width modulation (PWM). out Perform iterative updates to calculate the updated output pulse width modulation (PWM). out The gas-liquid ratio controller outputs updated output pulse width modulation (PWM). out Control valves or variable frequency pumps; Where a and b represent the control average gas flow rate values, respectively. The lower limit coefficient and the upper limit coefficient.

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