Engine liquid ammonia gasification detection method, liquid ammonia supply system and vehicle

Abstract

The application discloses an engine liquid ammonia gasification detection method, a liquid ammonia supply system and a vehicle, and relates to the technical field of ammonia fuel engines. The method comprises the following steps: starting the engine, performing variable working condition operation and collecting liquid ammonia flow under different working conditions; judging whether the absolute value of the difference of the liquid ammonia flow under different working conditions is greater than 0, and performing corresponding operation; collecting real-time rail pressure, performing calculation and analysis, and taking corresponding measures according to the analysis result; collecting the real-time pressure of each measuring point in the oil circuit, performing calculation and analysis, and judging the influence degree of the liquid ammonia gasification amount on the engine; if the influence degree is not great, compensation measures are performed; if the influence degree is great, the load is reduced or the engine is stopped according to the calibration setting. The pressure condition in the liquid ammonia supply system can be monitored as a whole, the liquid ammonia gasification phenomenon in the pipeline can be found in time, and corresponding treatment modes are provided according to the influence degree; and the fault troubleshooting efficiency is improved, and manpower and material resources are saved.

Description

Technical Field

[0001] This invention relates to the field of ammonia fuel engine technology, and in particular to a method for detecting liquid ammonia vaporization in an engine, a liquid ammonia supply system, and a vehicle. Background Technology

[0002] Ammonia is an excellent hydrogen storage carrier with more stable physicochemical properties, making it safer to store and transport. It is a new type of zero-carbon fuel with obvious advantages, and the large-scale industrial production technology of ammonia is relatively mature.

[0003] When air bubbles are present in the liquid ammonia supply system, their volume changes with the reciprocating motion of the high-pressure oil pump plunger. During the compression stroke, the bubbles are compressed, preventing the oil pressure from rising to the specified injection pressure. During the suction stroke, the bubbles expand back to their original volume, preventing sufficient negative pressure from being generated in the pipeline. Thus, the presence of air bubbles acts like a blockage, resulting in insufficient or even interrupted ammonia supply.

[0004] Currently, the detection of air bubbles in liquid ammonia supply systems relies on assessing engine performance during vehicle operation. Torque fluctuations during normal driving suggest air bubbles in the liquid ammonia supply system. In such cases, professional technicians are needed to troubleshoot and manually eliminate the air bubbles. Existing technology involves collecting pressure data from the pipeline before the metering valve. When the measured pressure exceeds a certain threshold, air bubbles are considered to be present in the pipeline. However, a pressure exceeding the threshold for a short period does not necessarily lead to engine deterioration; adjusting injection parameters can ensure normal engine operation. Additionally, researchers have proposed a gas / liquid separation device, but its complexity and high cost currently preclude its application in automobiles.

[0005] CN117211999A provides an engine liquid ammonia fuel supply system and its control method, comprising: a liquid ammonia storage tank; a detection device for detecting the temperature and pressure of ammonia fuel in the liquid ammonia injector of the engine liquid ammonia fuel supply system; a controller for obtaining the saturated vapor pressure of the ammonia fuel based on the temperature and pressure, and sending a pressurization signal when the pressure is less than the saturated vapor pressure; a pressurization device disposed in the injection pipeline where the liquid ammonia injector is located and electrically connected to the controller, for receiving the pressurization signal and increasing the compression pressure according to the pressurization signal to liquefy the ammonia fuel; and a liquid ammonia injector disposed in the cylinder head of the engine and connected to the liquid ammonia storage tank for injecting the ammonia fuel into the combustion chamber of the engine. However, this prior art still cannot monitor the vaporization of liquid ammonia. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting liquid ammonia vaporization in an engine, a liquid ammonia supply system, and a vehicle. This method can monitor the overall pressure within the liquid ammonia supply system, promptly detect liquid ammonia vaporization in the pipeline, and provide corresponding handling methods based on the degree of impact. This is beneficial for improving troubleshooting efficiency and saving manpower and resources.

[0007] This invention provides the following solutions

[0008] A method for detecting the vaporization of liquid ammonia in an engine includes the following steps:

[0009] S1. Start the engine, perform variable operating condition operation and collect the liquid ammonia flow rate under different operating conditions;

[0010] S2. Determine whether the absolute value of the difference in liquid ammonia flow rate under different operating conditions is greater than 0, and perform the corresponding operation.

[0011] S3. Collect real-time rail pressure, perform calculation and analysis, and take corresponding measures based on the analysis results;

[0012] S4. Collect the real-time pressure at each measuring point in the oil circuit, perform calculations and analysis, and determine the degree of impact of liquid ammonia vaporization on the engine; if the impact is not significant, implement compensation measures.

[0013] S5. Reduce the load or shut down the machine according to the calibration settings.

[0014] Furthermore, step S2 includes the following: the difference in liquid ammonia flow rate under different operating conditions is ΔQ. If |ΔQ|=0, then step S1 is executed again; if |ΔQ|>0, then step S3 is executed.

[0015] Furthermore, step S3 includes calculating the pressure change rate dpi / dt based on the real-time collected rail pressure pi, and referring to the maximum rail pressure change rate ai pre-calibrated in MAP1, and comparing dpi / dt with ai;

[0016] If dpi / dt > ai, then the liquid ammonia is determined to be severely vaporized, and step S5 is executed;

[0017] If dpi / dt≤ai, then proceed to step S4.

[0018] Furthermore, step S4 includes,

[0019] S41. Under the same operating conditions, collect the real-time pressure at each measuring point in the oil circuit, and record the pressure P at the nth measuring point in the oil circuit at fixed intervals when pressure fluctuations are detected. n-i，measure And compared with the maximum pressure P of this working condition in the pre-calibrated MAP2. n-i，limit Perform a comparison;

[0020] S42. Calculate the first recording time t.n-1 With the current recording time t n-i Time difference Δt, Δt = t n-i -t n-1 And compared with the longest response time T of this working condition in the pre-calibrated MAP2. n-i Perform a comparison;

[0021] S43. Based on the comparison results of steps S41 and S42, determine the degree of influence of liquid ammonia vaporization. If the degree of influence is determined to be small, compensate for the fuel supply; if the degree of influence is determined to be large, execute step S5. n is the measurement point number, corresponding to different measurement point positions, and i is the current recording number of the corresponding measurement point in the oil circuit.

[0022] Furthermore, step S43 includes determining the current recording time t. n-i Record pressure P n-i，measure Does P satisfy? n-i，measure >P n-i，limit And the time difference Δt satisfies Δt>T n-i If yes, then the impact of the liquid ammonia vaporization is determined to be significant, and step S5 is executed; if no, then the impact is determined to be minor, and fuel supply is compensated.

[0023] Furthermore, step S4 specifically includes recording the pressure P at the nth measuring point m times consecutively. n-i，measure and with P n-i，limit For comparison, m ≥ i;

[0024] If the results of m consecutive alignments are all P n-i，measure ≤P n-i，limit If the system is stable, a small amount of fuel supply will be compensated.

[0025] If the first alignment result is P in the m-th iteration n-i，measure >P n-i，limit If i=m, then the system is deemed to be at risk, the recording and analysis frequency is increased to continue recording and analysis, and compensation is initiated through liquid ammonia injection.

[0026] If at least two consecutive alignment results appear in m record analyses or subsequent record analyses, the result is P. n-i，measure >P n-i，limit Then calculate the time difference Δt = t n-i -t n-1 and with T n-i Compare the results and determine the extent of the impact on the amount of liquid ammonia vaporization.

[0027] If Δt≤T n-i If the impact is not significant, the liquid ammonia injection parameters should be adjusted to compensate.

[0028] If Δt>T n-i If the system is found to be out of balance and the impact is significant, then step S5 is executed.

[0029] Furthermore, each measuring point in the oil circuit includes a first measuring point, a second measuring point, and a third measuring point. The first measuring point is near the rear end of the switching valve, the second measuring point is near the rear end of the flow meter, and the third measuring point is near the rear end of the pressure boosting valve.

[0030] Step S43 further includes, if the impact is determined to be minor, in addition to compensating for the fuel supply, taking corresponding compensation measures based on the location of the measuring point where gasification occurs; specifically including:

[0031] If vaporization is detected at the pressure measuring point after the valve is switched, the venting system is controlled to remove air bubbles upstream of the liquid ammonia supply system.

[0032] If vaporization is detected at the pressure measuring point after the flow meter, the cooling system of the pipeline after the flow meter is controlled to perform local cooling to ensure the normal operation of the supply system.

[0033] If vaporization is detected at the pressure measuring point after the pressure booster valve, the cooling system of the pipeline after the pressure booster valve is controlled to perform local cooling and reliquefy the ammonia.

[0034] A liquid ammonia supply system for implementing the above-mentioned engine liquid ammonia vaporization detection method includes a main system, a cooling system, and a venting system. The venting system is connected to the main system via a pipeline, and the cooling system is located outside a portion of the pipeline of the main system.

[0035] Furthermore, the main system includes a liquid ammonia tank, a switching valve, a pressure sensor downstream of the switching valve, a fine filter, a flow meter, a pressure sensor downstream of the flow meter, a booster valve, a pressure sensor downstream of the booster valve, a rail pressure sensor, a high-pressure common rail device, and an ammonia engine, all connected sequentially by pipelines. A main return oil line connects the ammonia engine and the liquid ammonia tank. The pipeline between the fine filter and the flow meter is connected to the main return oil line via a first return oil branch. The pipeline between the pressure sensor downstream of the flow meter and the booster valve is connected to the main return oil line via a second return oil branch. A return oil pump is installed on the main return oil line between the first return oil branch and the liquid ammonia tank. The main system also includes an ECU, which is electrically connected to each pressure sensor, switching valve, flow meter, booster valve, high-pressure common rail device, ammonia engine, and return oil pump.

[0036] The cooling system includes a first pipeline cooling system installed on the pipeline between the pressure sensor after the flow meter and the booster valve, and a second pipeline cooling system installed on the pipeline between the pressure sensor after the booster valve and the rail pressure sensor.

[0037] The venting system includes a venting valve, an ammonia fuel gas-liquid separator, a scrubbing tower, an ammonia water buffer tank, a venting circuit switch valve, and an SCR system, which are connected in sequence through pipelines. The venting valve is connected to the pressure sensor and the fine filter through a pipeline connected to the switch valve. The venting valve and the venting circuit switch valve are electrically connected to the ECU.

[0038] A vehicle, including the aforementioned liquid ammonia supply system, enables a method for detecting the vaporization of liquid ammonia in an engine.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] This invention addresses the issues of rail pressure fluctuations and combustion degradation in liquid ammonia supply systems caused by partial liquid ammonia vaporization due to pressure and temperature changes. It proposes a structure and method for pressure protection and fuel supply strategy adjustment using multi-point pressure feedback correction in the liquid ammonia supply pipeline, specifically involving the following aspects:

[0041] By utilizing the varying degrees of influence of different measuring points on engine operating status, the degree of vaporization of liquid ammonia in the liquid ammonia supply system can be determined, thus avoiding unnecessary user intervention.

[0042] Evaluation methods and threshold calibration for pressure fluctuations at different locations.

[0043] This liquid ammonia vaporization detection system collects pressure data in real time from pressure measuring points. The ECU uses the collected data and a preset evaluation method to determine the vaporization status of the liquid ammonia in the supply system. It can promptly predict the deterioration of engine operating conditions caused by pressure fluctuations, and compensate for insufficient ammonia supply by adjusting injection parameters, reducing load, or shutting down the engine, effectively minimizing losses caused by the deterioration of the ammonia engine's condition. Attached Figure Description

[0044] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0045] Appendix Figure 1 This is a schematic flowchart of the engine liquid ammonia vaporization detection method described in this invention;

[0046] Appendix Figure 2 This is a schematic diagram of the control logic for the engine liquid ammonia vaporization detection method described in this invention;

[0047] Appendix Figure 3This is a schematic diagram of the control logic for taking corresponding compensation measures based on the location of the measuring point where vaporization occurs, as described in this invention.

[0048] Appendix Figure 4 This is a schematic diagram of the liquid ammonia supply system described in this invention.

[0049] In the picture:

[0050] 1. Liquid ammonia tank; 2. First switching valve; 3. Pressure sensor after switching valve; 4. Fine filter; 5. Flow meter; 6. Pressure sensor after flow meter; 7. Pressure booster valve; 8. Pressure sensor after pressure booster valve; 9. Rail pressure sensor; 10. High-pressure common rail device; 11. Nozzle; 12. Ammonia engine; 13. Return oil circuit; 14. Return oil pump; 15. Vent valve; 16. Ammonia fuel gas-liquid separator; 17. Scrubber; 18. Ammonia water buffer tank; 19. Second switching valve; 20. SCR system; 21. First pipeline cooling system; 22. Second pipeline cooling system. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0053] It should be understood that the term "and / or" used in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0054] It should be understood that although the terms first, second, third, etc., may be used in the embodiments of this application, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, first may also be referred to as second without departing from the scope of the embodiments of this application, and similarly, second may also be referred to as first.

[0055] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0056] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0057] It should be noted that any symbols and / or numbers present in the specification that are not marked in the accompanying drawings are not reference numerals.

[0058] Example 1, please refer to Figure 4 As shown, this embodiment provides a liquid ammonia supply system, including a liquid ammonia tank 1, a switching valve, a pressure sensor 3 after the switching valve, a fine filter 4, a flow meter 5, a pressure sensor 6 after the flow meter, a pressure boosting valve 7, a pressure sensor 8 after the pressure boosting valve, a rail pressure sensor 9, a high-pressure common rail device 10, and an ammonia engine 12 connected in sequence by pipelines. A return oil main line is connected between the ammonia engine 12 and the liquid ammonia tank 1. The pipeline between the fine filter 4 and the flow meter 5 is connected to the return oil main line through a first return oil branch line. The pipeline between the pressure sensor 6 after the flow meter and the pressure boosting valve 7 is connected to the return oil main line through a second return oil branch line. A return oil pump 14 is installed on the return oil main line between the first return oil branch line and the liquid ammonia tank 1.

[0059] The system also includes an ECU, or electronic control unit, which is electrically connected to each pressure sensor, switching valve, flow meter 5, booster valve 7, high-pressure common rail device 10, ammonia engine 12 and return oil pump 14. The high-pressure common rail device 10 includes a high-pressure oil pump, a common rail chamber and a high-pressure oil pipe, which is used to completely separate the generation of injection pressure and the injection process. The high-pressure common rail device 10 is connected to the nozzle 11 of the ammonia engine 12 through a pipeline.

[0060] Pressure measuring points and pressure sensors are installed at the following locations: after the switching valve, after the flow meter 5, after the booster valve 7, and on the high-pressure common rail. The vaporization of ammonia in the liquid ammonia supply system is monitored by measuring pressure fluctuations. The pressure measuring points are set after components such as the valve body and flow meter 5 because the fluid is more easily vaporized after passing through the throttling effect of the valve. It is worth noting that the pressure sensor should be placed as close as possible to the adjacent components to ensure rapid response and reduce the influence of other factors.

[0061] Liquid ammonia enters the supply system from the liquid ammonia tank 1 through the switch valve, passes through the fine filter 4 to filter impurities, flows through the flow meter 5, and is then pressurized to 35-50MPa by the pressure boosting valve 7 before being supplied to the high-pressure common rail device 10, and then sprayed into the cylinder of the ammonia engine 12 through the nozzle 11.

[0062] In addition, return oil lines 13 are set in multiple parts of the supply system to pump unused liquid ammonia back into the ammonia tank through return oil pump 14; on the one hand, this reduces unnecessary waste of liquid ammonia, and on the other hand, it prevents redundant liquid ammonia in the supply system from flowing into the high-pressure common rail device 10 after being pressurized by the pressure boosting valve 7, which would cause rail pressure fluctuations.

[0063] The system also includes a cooling system; pipeline cooling systems are set up in different sections of the liquid ammonia supply system. For example, in this embodiment, a first pipeline cooling system 21 is set up on the pipeline between the pressure sensor 6 after the flow meter and the pressure boosting valve 7, and a second pipeline cooling system 22 is set up on the pipeline between the pressure sensor 8 after the pressure boosting valve and the rail pressure sensor 9. The pipeline cooling system can be a liquid nitrogen intercooler, which is used to make the ammonia gas reliquefy when it is cooled.

[0064] In addition, a venting system is connected to the pipeline between the pressure sensor 3 after the switching valve and the fine filter 4; the venting system includes a venting valve 15, an ammonia fuel gas-liquid separator 16, a scrubbing tower 17, an ammonia water buffer tank 18, a venting circuit switching valve and an SCR system 20 connected in sequence through the pipeline. The venting valve 15 is connected to the pipeline between the pressure sensor 3 after the switching valve and the fine filter 4 through the pipeline; the venting valve 15 and the venting circuit switching valve are electrically connected to the ECU respectively.

[0065] When the venting standard is met, the ECU controls the venting valve 15 to open. Partially vaporized liquid ammonia in the pipeline is filtered out by the ammonia fuel gas-liquid separator 16, then converted into ammonia water after being sprayed through the scrubbing tower 17 and transported to the ammonia water buffer tank 18. The function of the ammonia water buffer tank 18 is to maintain the ammonia water obtained after being sprayed through the scrubbing tower 17 at a relatively reasonable concentration. When the ammonia water reaches a certain concentration, the ECU controls the venting circuit switch valve to open, and the ammonia water flows into the SCR system 20. The SCR (Selective Catalytic Reduction) system is a core technology used for exhaust gas aftertreatment, which uses urea solution to remove nitrogen oxides (NOx). xThe urea is converted into harmless nitrogen (N2) and water (H2O), and is widely used to reduce pollutant emissions from vehicles and industrial equipment. When the urea concentration is around 32.5%, the SCR system 20 exhibits high denitrification capacity. Furthermore, the venting system is located upstream of the entire liquid ammonia supply system because the bubbles generated by upstream vaporization, after passing through multiple throttling components, would produce a more severe vaporization phenomenon; therefore, air bubbles should be vented as much as possible upstream.

[0066] Example 2, please refer to Figure 1 As shown, this embodiment provides a method for detecting the vaporization of liquid ammonia in an engine, based on the aforementioned liquid ammonia supply system, and includes the following steps:

[0067] S1. Start the engine, perform variable operating condition operation and collect the liquid ammonia flow rate under different operating conditions;

[0068] S2. Determine whether the absolute value of the difference in liquid ammonia flow rate under different operating conditions is greater than 0, and perform the corresponding operation.

[0069] S3. Collect real-time rail pressure, perform calculation and analysis, and take corresponding measures based on the analysis results;

[0070] S4. Collect the real-time pressure at each measuring point in the oil circuit, perform calculations and analysis, and determine the degree of influence of liquid ammonia vaporization; if the degree of influence is not significant, implement compensation measures.

[0071] S5. Reduce the load or shut down the machine according to the calibration settings.

[0072] This method mainly uses pressure sensors installed at different locations in the liquid ammonia supply system to collect data, which is then transmitted to the ECU. The ECU determines the operating status based on the collected data and controls the entire device accordingly, thereby achieving real-time monitoring of the vaporization status of the liquid ammonia supply system and maintaining the stability of the liquid ammonia supply capacity. The ECU uses the sensor data to determine the compensation or handling methods under this operating condition.

[0073] Specifically, the rail pressure pi is collected in real time by the rail pressure sensor 9, and the ECU judges the degree of vaporization of liquid ammonia based on the fluctuation of pi. Since the high-pressure common rail device 10 is the last link for liquid ammonia to enter the cylinder through the nozzle 11, the fluctuation of rail pressure pi has a huge impact on the engine operating status. Therefore, the detection of rail pressure pi should be upstream of the logic judgment.

[0074] Specifically, when bubbles are present in the supply system, i.e. when ammonia is vaporized, the pressure in the supply system will rise. The degree of liquid ammonia vaporization is characterized by judging the degree of pressure change, and then the corresponding measures are determined by judging the degree of impact of liquid ammonia vaporization on the engine status.

[0075] Please see Figure 2As shown, when the liquid ammonia flow rate is measured as Qi, the engine operating state is more sensitive to fluctuations in rail pressure pi. Therefore, the pressure change rate dpi / dt is used as the evaluation index because the pressure change rate can react to pressure fluctuations more promptly and quickly. The maximum allowable rail pressure change rate ai under each operating condition is calibrated in the ECU's stored data MAP1 based on the operating conditions. It can be considered that under high load and high flow rate, the liquid ammonia has a stronger tendency to vaporize in the supply system. Therefore, the threshold should be more stringent under high load conditions, that is, the maximum allowable rail pressure change rate ai preset in MAP1 should decrease as the liquid ammonia flow rate increases. For example, the operating condition when the vehicle load is less than or equal to 50% is the low-load operating condition, and the operating condition when the vehicle load is greater than 50% is the high-load operating condition. Under the low-load operating condition, the liquid ammonia flow rate is Q1, the collected rail pressure is p1, and the pressure change rate is dp1 / dt. At this time, the maximum allowable rail pressure change rate preset in MAP1 is a1, which can be set to 0.6 MPa / ms. Under the high-load operating condition, the liquid ammonia flow rate is Q2, the collected rail pressure is p2, and the pressure change rate is dp2 / dt. At this time, the maximum allowable rail pressure change rate preset in MAP1, a2, needs to be reduced to 0.3 MPa / ms.

[0076] Let Qi be the liquid ammonia flow rate under the i-th operating condition, and Qj be the liquid ammonia flow rate under the j-th operating condition. Let ΔQ be the flow rate difference between the i-th and j-th operating conditions. Then ΔQ = Qj - Qi.

[0077] If the engine is running and undergoing variable operating conditions, and |△Q|=0, it can be assumed that there is a communication problem between the ECU and the vehicle, and the engine needs to be restarted. If |△Q|>0, the ECU calculates the derivative of dpi / dt of the real-time collected rail pressure pi and compares it with the maximum rail pressure change rate ai in the pre-calibrated MAP1. If dpi / dt>ai, the engine operating status fluctuates greatly, which can be considered as severe liquid ammonia vaporization. The load should be reduced or the engine should be shut down according to the calibration settings. If dpi / dt≤ai, downstream logic judgment is performed.

[0078] Specifically, since pressure fluctuations near the back end of the switching valve (first measuring point), the back end of flow meter 5 (second measuring point), and the back end of booster valve 7 (third measuring point) have less impact on engine status than rail pressure fluctuations, a more lenient evaluation index should be adopted. Furthermore, it can be assumed that pressure fluctuations at locations farther from the engine have less impact on engine status, meaning that the pressure thresholds at the first, second, and third measuring points gradually decrease and approach the target pressure. When the operating conditions change, resulting in a large liquid ammonia supply, i.e., a large liquid ammonia flow rate, the vaporization phenomenon will be more pronounced.

[0079] When the liquid ammonia flow rate is Qi, the pressure collected in real time at the nth measuring point is P. n-i，measure The time of this moment is denoted as t. n-iThe ECU's stored data MAP2 is calibrated based on operating conditions, specifying the longest response time T as varying with flow rate. n-i (i.e., the maximum duration of pressure exceeding the limit) and the maximum allowable pressure P at each liquid ammonia flow rate. n-i，limit P n-i，limit The response time should become more stringent as the load increases, meaning it should approach the target pressure value more closely as the liquid ammonia flow rate increases. Furthermore, the longest response time T... n-i Specific load factors and the placement of pressure sensors should also be considered. The actual settings should be based on the actual vehicle structure and test calibration.

[0080] Specifically, taking the pressure after flow meter 5 (second measuring point) as an example; P in MAP2 n-i，limit The calibration method is as follows: At time t1, the liquid ammonia flow rate measured by flowmeter 5 is Q1, and the pressure measured by pressure sensor 6 downstream of the flowmeter is P. 2-1，measure The target rail pressure at rail pressure sensor 9 is P. 0-1，target At time t2, the liquid ammonia flow rate measured by flow meter 5 is Q2, and the pressure measured by pressure sensor 6 downstream of the flow meter is P. 2-2，measure The corresponding target orbital pressure is P. 0-2，target Similarly, at time ti, the liquid ammonia flow rate measured by flowmeter 5 is Qi, and the pressure measured by pressure sensor 6 downstream of the flowmeter is P. 2-i，measure The target rail pressure at rail pressure sensor 9 is P. 0-i，target All corresponding MAP2 calibration values ​​are determined by calibration data, and under low load conditions, the maximum allowable pressure at the second measuring point can be set to P. 2-i，limit =P 0-i，target ×1.1; Under heavy load conditions, the pressure threshold P 2-i，limit =P 0-i，target ×1.05.

[0081] When the vehicle is running, when the pressure sensor 6 after the flow meter detects pressure fluctuations, the ECU starts to record the pressure after the flow meter 5 at fixed intervals and records it multiple times. For example, in this embodiment, the pressure after the flow meter 5 is recorded three times in a row, with a time interval of T1, and compared with the calibration value in MAP2.

[0082] If P 2-1，measure ≤P 2-1，limit P 2-2，measure ≤P 2-2，limit P 2-3，measure ≤P 2-3，limit If the system is deemed stable, then liquid ammonia injection is performed through the high-pressure common rail device 10 to slightly compensate for the fuel supply.

[0083] If P 2-1，measure ≤P 2-1，limit P 2-2，measure ≤P2-2，limit P 2-3，measure >P 2-3，limit If the system is deemed to be at risk, the recording and analysis frequency is increased to continue recording and analysis, the time interval is shortened from T1 to T2, and compensation is started through liquid ammonia injection.

[0084] If P 2-1，measure ≤P 2-1，limit P 2-2，measure >P 2-2，limit P 2-3，measure >P 2-3，limit Then calculate the time difference Δt = t 2-3 -t 2-1 and with T 2-3 Perform a comparison; if Δt ≤ T 2-3 Then Δt is still within the longest response time T specified by MAP2. 2-3 Within this range, adjust the injection parameters and continue to compensate through injection; if Δt > T 2-3 If this occurs, it is determined to be a system malfunction. The amount of liquid ammonia vaporization has a significant impact on the engine, and it is necessary to reduce the load or shut down the engine according to the calibration settings.

[0085] Since the pressure fluctuations after flow meter 5 have a smaller impact on the engine condition than the rail pressure fluctuations, when P 2-i，measure >P 2-i，limit Time may not necessarily have an adverse effect on engine operation, so response time must also be considered; when Δt≤T 2-3 When Δt > T, it can be assumed that within the longest response time calibrated by MAP2, the pressure of the supply system is capable of returning to stability or that the engine state can be kept unaffected by compensation of injection parameters; 2-3 And P appears continuously 2-i，measure >P 2-i，limit When comparing the results, it was concluded that the liquid ammonia was severely vaporized, and it was necessary to reduce the load or shut down the machine for inspection.

[0086] Similarly, the calculation methods and judgment criteria for the pressure measurement points near the back end of the switching valve (first measuring point) and near the back end of the booster valve 7 (third measuring point) are roughly the same; the difference is that the degree of influence of pressure measuring points at different locations on the engine state is different, so it is only necessary to select an appropriate multiplicative coefficient for the calibration value in MAP2. Liquid ammonia is pressurized after passing through flow meter 5, and the gas is compressible, so the bubbles will generate strong pressure fluctuations after being pressurized; therefore, a narrower threshold should be used for the pressure fluctuations after flow meter 5. In addition, it can be considered that the farther the pressure measuring point is from the engine, the lower the sensitivity of its pressure fluctuations to the engine operating state; therefore, in this embodiment, the MAP thresholds calibrated for the pressure measuring points after the switching valve and after the booster valve 7 are multiplied by 1.05 and 0.95 respectively based on MAP2.

[0087] Please see Figure 3 As shown, multiple pressure measuring points can accurately determine the location of severe liquid ammonia vaporization. The ECU controls different locations to take corresponding compensation measures by judging the magnitude of Δt and ΔQ at different pressure measuring points and their corresponding data calibration thresholds. When vaporization is detected at the pressure measuring point after the switch valve, the ECU controls the venting system to work, eliminating as many air bubbles as possible upstream of the liquid ammonia supply system. When vaporization is detected at the pressure measuring point after flow meter 5, the ECU controls the cooling system of the pipeline after flow meter 5 to work, providing localized cooling to ensure normal operation of the supply system. When vaporization is detected at the pressure measuring point after booster valve 7, the ECU controls the cooling system of the pipeline after booster valve 7 to work, providing localized cooling to reliquefy the ammonia.

[0088] Pressure fluctuations at various measuring points will affect the ammonia supply to the engine to varying degrees. What they have in common is that they are all compensated by dual-fuel injection pulse width. When the compensation cannot make the engine operation state more stable, it is inevitable to shut down the engine. At this time, the pressure in the pipeline can be released manually.

[0089] Example 3: This example provides a vehicle including the above-mentioned liquid ammonia supply system, which can realize the engine liquid ammonia vaporization detection method.

[0090] 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 do 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 detecting the vaporization of liquid ammonia in an engine, characterized in that, Includes the following steps: S1. Start the engine, perform variable operating condition operation and collect the liquid ammonia flow rate under different operating conditions; S2. Determine whether the absolute value of the difference in liquid ammonia flow rate under different operating conditions is greater than 0, and perform the corresponding operation. S3. Collect real-time rail pressure and perform calculation and analysis. If it is determined that the liquid ammonia is severely vaporized, proceed to step S5; otherwise, proceed to step S4. S4. Collect the real-time pressure at each measuring point in the oil circuit, perform calculation and analysis, and determine the degree of impact of liquid ammonia vaporization on the engine; if the impact is not significant, implement compensation measures; if the impact is determined to be significant, proceed to step S5. S5. Reduce the load or shut down the machine according to the calibration settings.

2. The method for detecting liquid ammonia vaporization in an engine according to claim 1, characterized in that, Step S2 includes the difference in liquid ammonia flow rate under different operating conditions being ΔQ. If |ΔQ|=0, then step S1 is executed again. If |△Q|>0, then proceed to step S3.

3. The method for detecting liquid ammonia vaporization in an engine according to claim 1, characterized in that, Step S3 includes calculating the pressure change rate dpi / dt based on the real-time collected rail pressure pi, and referring to the maximum rail pressure change rate ai pre-calibrated in MAP1, and comparing dpi / dt with ai; If dpi / dt > ai, then the liquid ammonia is determined to be severely vaporized, and step S5 is executed; If dpi / dt≤ai, then proceed to step S4.

4. The method for detecting liquid ammonia vaporization in an engine according to claim 1, characterized in that, Step S4 includes, S41. Under the same operating conditions, collect the real-time pressure at each measuring point in the oil circuit, and record the pressure P at the nth measuring point in the oil circuit at fixed intervals when pressure fluctuations are detected. n-i，measure And compared with the maximum pressure P of this working condition in the pre-calibrated MAP2. n-i，limit Perform a comparison; S42. Calculate the first recording time t. n-1 With the current recording time t n-i Time difference Δt, Δt = t n-i -t n-1 And compared with the longest response time T of this working condition in the pre-calibrated MAP2. n-i Perform a comparison; S43. Based on the comparison results of steps S41 and S42, determine the degree of influence of liquid ammonia vaporization. If the degree of influence is determined to be small, compensate for the fuel supply; if the degree of influence is determined to be large, execute step S5. n is the measurement point number, corresponding to different measurement point positions, and i is the current recording number of the corresponding measurement point in the oil circuit.

5. The method for detecting liquid ammonia vaporization in an engine according to claim 4, characterized in that, Step S43 includes determining the current recording time t. n-i Record pressure P n-i，measure Does P satisfy? n-i，measure >P n-i，limit And the time difference Δt satisfies Δt>T n-i If yes, then the impact of the liquid ammonia vaporization is determined to be significant, and step S5 is executed; if no, then the impact is determined to be minor, and fuel supply is compensated.

6. The method for detecting liquid ammonia vaporization in an engine according to claim 5, characterized in that, Step S4 specifically includes recording the pressure P at the nth measuring point m times consecutively. n-i，measure and with P n-i，limit For comparison, m ≥ i; If the results of m consecutive alignments are all P n-i，measure ≤P n-i，limit If the system is stable, a small amount of fuel supply will be compensated. If the first alignment result is P in the m-th iteration n-i，measure >P n-i，limit If i=m, then the system is determined to be at risk, the recording and analysis frequency is increased to continue recording and analysis, and compensation is started through liquid ammonia injection; If at least two consecutive alignment results are found in m record analyses or subsequent record analyses, then P is a valid alignment result. n-i，measure >P n-i，limit Then calculate the time difference Δt = t n-i -t n-1 and with T n-i Compare the results and determine the extent of the impact on the amount of liquid ammonia vaporization. If Δt≤T n-i If the impact is not significant, the liquid ammonia injection parameters should be adjusted to compensate. If Δt>T n-i If the system is found to be out of balance and the impact is significant, then step S5 is executed.

7. The method for detecting liquid ammonia vaporization in an engine according to claim 4, characterized in that, Each measuring point in the oil circuit includes a first measuring point, a second measuring point, and a third measuring point. The first measuring point is near the rear end of the switching valve, the second measuring point is near the rear end of the flow meter, and the third measuring point is near the rear end of the pressure boosting valve. Step S43 further includes, if the impact is determined to be minor, in addition to compensating for the fuel supply, taking corresponding compensation measures based on the location of the measuring point where gasification occurs; specifically including: If vaporization is detected at the pressure measuring point after the valve is switched, the venting system is controlled to remove air bubbles upstream of the liquid ammonia supply system. If vaporization is detected at the pressure measuring point after the flow meter, the cooling system of the pipeline after the flow meter is controlled to perform local cooling to ensure the normal operation of the supply system. If vaporization is detected at the pressure measuring point after the pressure booster valve, the cooling system of the pipeline after the pressure booster valve is controlled to perform local cooling and reliquefy the ammonia.

8. A liquid ammonia supply system, characterized in that, The method for detecting liquid ammonia vaporization in an engine as described in any one of claims 1-7 includes a main system, a cooling system, and a venting system, wherein the venting system is connected to the main system via a pipeline, and the cooling system is located outside a portion of the pipeline of the main system.

9. The liquid ammonia supply system according to claim 8, characterized in that, The main system includes a liquid ammonia tank (1), a switching valve, a pressure sensor (3) after the switching valve, a fine filter (4), a flow meter (5), a pressure sensor (6) after the flow meter, a booster valve (7), a pressure sensor (8) after the booster valve, a rail pressure sensor (9), a high-pressure common rail device (10), and an ammonia engine (12) connected in sequence by pipelines. A return oil main line is connected between the ammonia engine (12) and the liquid ammonia tank (1). The pipeline between the fine filter (4) and the flow meter (5) is connected to the return oil main line through a first return oil branch. The pipeline between the pressure sensor (6) after the flow meter and the booster valve (7) is connected to the return oil main line through a second return oil branch. A return oil pump (14) is installed on the return oil main line between the first return oil branch and the liquid ammonia tank (1). The main system also includes an ECU, which is electrically connected to each pressure sensor, switching valve, flow meter (5), booster valve (7), high-pressure common rail device (10), ammonia engine (12), and return oil pump (14). The cooling system includes a first pipeline cooling system (21) installed on the pipeline between the pressure sensor (6) after the flow meter and the booster valve (7), and a second pipeline cooling system (22) installed on the pipeline between the pressure sensor (8) after the booster valve and the rail pressure sensor (9). The venting system includes a venting valve (15), an ammonia fuel gas-liquid separator (16), a scrubbing tower (17), an ammonia water buffer tank (18), a venting circuit switch valve, and an SCR system (20) connected in sequence through pipelines. The venting valve (15) is connected to the pipeline between the pressure sensor (3) and the fine filter (4) after the switch valve through a pipeline. The venting valve (15) and the venting circuit switch valve are electrically connected to the ECU.

10. A vehicle, characterized in that, Includes the liquid ammonia supply system as described in claim 9.

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