Fuel oil water injection and heating and cooling integrated system for fuel oil icing test

Abstract

The invention discloses a fuel oil water injection and heating and cooling integrated system for a fuel oil icing test, and the heating and cooling control of fuel oil is realized by adjusting the rotating speed of a compressor in primary and secondary heat conduction oil circulation and the fuel oil flow of an electric heater pipeline. According to cooling selection, heat exchange of fuel oil and a refrigerant in an external plate heat exchanger is optimized, an oil tank externally-wound variable-pitch evaporator coil is selected to replace the plate heat exchanger, and second-stage heat conduction oil with large specific heat capacity is selected in an evaporator to serve as an intermediate medium for heat exchange. And the intermediate medium is cooled by the first-stage heat conduction oil to control the fuel oil temperature, so that the reliability of equipment is improved, the heat exchange area is increased, the secondary flow intensity is improved, and the heat exchange efficiency is enhanced. Water is injected from a nozzle in the fuel tank after the heating and cooling process is finished, at the moment, the temperature of the fuel tank still needs to be monitored, the heating and cooling system is started to keep the fuel temperature constant, saturated water-containing fuel meeting airworthiness standards is prepared, and the oil is discharged through an oil return opening to complete the integrated process of preparation of the saturated water-containing fuel.

Description

Technical Field

[0001] The invention relates to the technical field of water-containing fuel for aviation fuel icing test configuration, and in particular to a fuel cooling and water injection integrated system for fuel icing test. Background Art

[0002] Existing airworthiness regulations have strict requirements on the water content and temperature of test fuel. Fuel temperature and water-containing fuel configuration method directly affect the water content of fuel and the distribution pattern of free water in fuel, which in turn directly affects whether the expected amount of ice can be produced in the test oil circuit, which has an important impact on the test results. Different fuel icing test items require different fuel configuration methods and test processes. The present invention intends to study the configuration method of test fuel through relevant standards and specifications of fuel icing tests at home and abroad, and form a set of integrated fuel freezing and cooling water injection system, which can not only meet the precise control of fuel temperature, but also complete the preparation of saturated water-containing fuel while maintaining a constant temperature.

[0003] The heating and cooling system is a large inertia system. The fuel temperature regulation requires an accurate system model and the heating and cooling unit to work together to solve the coordination problem of temperature regulation rate and temperature difference limit. According to the traditional method, refrigerant is used for gas-liquid two-phase heat exchange. Due to the different specific heat capacity and heat absorption capacity of each state, during the fuel cooling process, the temperature difference between the fuel and the refrigerant in the heat exchanger exceeds 13°C, causing the free water in the fuel to freeze on the heat exchange wall, resulting in a decrease in the water content of the fuel. Therefore, it is necessary to improve the heat exchange method, adopt a new heat exchange method to replace the traditional plate heat exchanger, and improve the equipment to prevent the fuel in the tank from freezing.

[0004] In addition, the water content of the fuel in the fuel icing test and the distribution of water in the fuel have an important impact on the test results. In order to make the water content of the fuel meet the requirements of the test standard, it is necessary to control the water content and ensure that the dissolved water is evenly distributed. The existing equipment will cause the fuel temperature in the preparation process to deviate from the 27°C specified in the airworthiness standard due to the influence of natural convection heat transfer, motor heat dissipation and friction heat generated by low-viscosity fuel in the pipeline. The PPM (parts per million) of saturated water-containing fuel at different temperatures is different, resulting in the prepared saturated water-containing fuel not meeting the airworthiness specifications.

[0005] The present invention discloses a fuel water injection and cooling integrated system for fuel icing test based on the problems existing in the existing tests. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a fuel water injection and cooling integrated system for fuel freezing test in view of the defects involved in the background technology.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A fuel water injection and cooling integrated system for fuel freezing test, characterized by comprising a fuel tank, a refrigeration and heating unit, a hydraulic module and a control box.

[0009] The oil tank is provided with a temperature sensor and a low-speed agitator; the temperature sensor is used to sense the temperature of the oil in the oil tank, and the low-speed agitator is used to stir the oil in the oil tank to prevent the oil from freezing; the water injection port is respectively connected to the fifth solenoid valve, the first nozzle, the sixth solenoid valve, and the second nozzle in sequence for injecting water into the oil tank;

[0010] The refrigeration and heating unit includes an electric heater, first and second liquid storage tanks, a variable pitch coil of a refrigeration evaporator, first and second capillary tubes, a plate heat exchanger, and a condenser;

[0011] The hydraulic module comprises first to second ball valves, a motor pump group, first to third one-way valves, first to second filters, first to twelfth solenoid valves, first to third electric regulating valves, first to second safety valves, and first to second compressors;

[0012] The inlet of the oil tank is connected to one end of the second ball valve; the other end of the second ball valve is respectively connected to one end of the third electric regulating valve, one end of the seventh solenoid valve, one end of the thermal heater, and one end of the second safety valve through pipelines; the other end of the electric heater is connected to one end of the eighth solenoid valve; the other end of the third electric regulating valve, the tenth solenoid valve, and the oil return port are sequentially connected through pipelines; the other end of the seventh solenoid valve is respectively connected to the other end of the eighth solenoid valve, the other end of the second safety valve, one end of the second filter, and one end of the twelfth solenoid valve; the other end of the twelfth solenoid valve is connected to the oil supply port; the second filter, the first filter, and the ninth solenoid valve are sequentially connected;

[0013] The outlet of the oil tank, the first ball valve, the motor pump group, and one end of the third one-way valve are connected in sequence by pipelines; the other end of the third one-way valve is connected to the other end of the ninth solenoid valve and the other end of the eleventh solenoid valve;

[0014] The oil replenishing port is connected to one end of the first solenoid valve and one end of the first safety valve respectively; the other end of the first solenoid valve and the other end of the first safety valve are connected to the oil tank;

[0015] One end of the refrigeration evaporator coil is connected to one end of the second one-way valve; the other end of the second one-way valve is connected to the fourth solenoid valve and the second solenoid valve; one end of the second liquid storage tank is connected to the other end of the second electric regulating valve; the other end of the second liquid storage tank is connected to the fourth solenoid valve; the other end of the fourth solenoid valve, the second compressor, the hot side channel of the plate heat exchanger, the third solenoid valve, the second capillary tube, and the refrigeration evaporator coil are connected in sequence; one end of the cold side channel of the plate heat exchanger is connected to the second solenoid valve, the first capillary tube, and one end of the condenser in sequence; the other end of the cold side channel of the plate heat exchanger is connected to one end of the first one-way valve and one end of the first electric regulating valve; one end of the first liquid storage tank is connected to the first electric regulating valve; the other end of the first liquid storage tank is connected to the other end of the first one-way valve and one end of the first compressor; the other end of the first compressor is connected to the condenser;

[0016] The motor pump group is used to control the flow of external circulation and heating circulation fuel; the first to second filters are used to purify the oil in the external circulation and fuel output process, and filter the undissolved water; the electric regulating valve is used to control the return oil volume and the flow of thermal oil; the safety valve is used to adjust the required pressure of the system; the solenoid valve is used to control the flow of fuel entering the external circulation, heating circulation and the flow of the first and second thermal oil in the refrigeration circulation; the oil replenishment port is used to replenish the oil in the oil tank; the condenser uses water as a refrigerant to cool the first-level thermal oil;

[0017] The control box is composed of a box body, PLC, frequency converter, buttons, knobs, indicator lights, temperature control, digital display instruments, etc., and is used to control the opening of the solenoid valve in the external circulation, heating cycle, and refrigeration cycle, the speed of the motor pump group, and the speed of the first and second compressors.

[0018] The present invention discloses an operation process of the fuel water injection and heating and cooling integrated system for fuel icing test, comprising the following steps:

[0019] Step 1), manually open the first and second ball valves in the external circulation, and the control box controls the motor pump group, the seventh solenoid valve, the ninth solenoid valve, and the twelfth solenoid valve to open, so that the oil is injected into the fuel tank from the oil supply port, the twelfth solenoid valve, the seventh solenoid valve, and the second ball valve in sequence;

[0020] Step 2), the fuel temperature is fed back through the temperature sensor arranged in the fuel tank to determine whether the oil temperature reaches the airworthiness requirement of 27°C;

[0021] Step 2.1), if it is higher than the set temperature, adjust the opening of the first and second electric regulating valves and the speed of the first and second compressors through the control box, open the second, third and fourth solenoid valves, so that the first-level heat transfer oil circulates from the first liquid storage tank, the first compressor, the condenser, the first capillary, the second solenoid valve, the plate heat exchanger, and the first check valve in sequence; the second-level heat transfer oil circulates from the second liquid storage tank, the fourth solenoid valve, the second compressor, the plate heat exchanger, the third solenoid valve, the second capillary, and the refrigeration evaporator coil in sequence;

[0022] Step 2.2), if it is lower than the set temperature, close the seventh solenoid valve through the control box, open the eighth solenoid valve, and dynamically adjust the heating power of the electric heater, so that the fuel flows from the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the eleventh solenoid valve, the eighth solenoid valve, the electric heater, the second ball valve and then back to the fuel tank for circulation;

[0023] Step 2.3), if the set temperature is reached, the control box closes the first and second electric regulating valves, closes the second, third, fourth and eighth solenoid valves, closes the first and second compressors, and opens the seventh solenoid valve;

[0024] Step 3), close the ninth solenoid valve through the control box, open the fifth, sixth and eleventh solenoid valves, start the low-speed agitator, and inject free water into the fuel through the first and second nozzles at a flow rate of about 55 ml / min at a ratio of oil to water of 1000:1. If the water content meets the airworthiness standard, close the fifth and sixth solenoid valves, and the fuel passes through the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the ninth solenoid valve, the first and second filters, the seventh solenoid valve, and the second ball valve in sequence and then returns to the fuel tank for circulation;

[0025] Step 4), when the water injection volume meets the airworthiness standard, continue to circulate for about 30 minutes to ensure complete mixing and form saturated fuel. During this period, the fuel temperature must still meet the set value. If the temperature deviates from the set value, repeat step 2;

[0026] Step 5), if the cycle meets 30min, open the tenth solenoid valve and the third electric regulating valve through the control box, manually close the second ball valve, and the fuel will flow out from the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the eleventh solenoid valve, the seventh solenoid valve, the third electric regulating valve, the tenth solenoid valve, and the oil return port in sequence. After all the oil in the fuel tank is drained, close the motor pump group and the solenoid valve in the external circulation through the control box, manually close the first ball valve, and the preparation is completed.

[0027] As a further optimization scheme of the fuel water injection and heating and cooling integrated system for fuel freezing test of the present invention, the refrigeration system comprises: a condenser evaporator variable pitch coil;

[0028] The velocity vector of the fluid in the variable pitch coil of the condenser evaporator changes continuously during the flow process, which will cause secondary circulation on the cross section and enhance the heat exchange. r Correct the average Nu for heat transfer oil:

[0029]

[0030] Where d is the inner diameter of the spiral tube, m; R is the radius of the spiral tube, m. r About 0.95, c of the spiral tube heat exchanger r It is about 1.083. Therefore, when the heat exchange area is equal, Nu increases by about 14%. The surface heat transfer coefficient of the spiral tube can be calculated from Nu:

[0031]

[0032] In the formula, h i is the heat transfer coefficient of the inner surface of the tube, J / m 3 ·h·℃; l is the pipe diameter, m; the heat transfer coefficient is:

[0033]

[0034] Where v is the heat transfer coefficient, J / m 3 ·s·℃;h i is the heat transfer coefficient of the inner surface of the spiral tube heat exchanger, J / m 3 ·s·℃;h 0 is the heat transfer coefficient of the outer surface of the spiral tube heat exchanger, J / m 3 ·s·℃; λ is the thermal conductivity of the pipe, J / m 3 ·s·℃;k i , k o They are the reciprocals of the thermal resistance of the scale layer inside and outside the pipe, J / m 3 ·s·℃; It is the ratio of the outer surface area to the inner surface area of ​​the heat exchange tube. The final heat transfer is:

[0035] Q=AvΔT

[0036] Where A is the heat transfer area, m 2 ; ΔT is the average heat transfer temperature difference, °C. Therefore, when the heat exchange area and pipe material selection are the same, the heat transfer capacity of the spiral tube heat exchanger is increased by 14% compared with the plate heat exchanger.

[0037] The condenser evaporator coils are divided into two heat exchange modes: external winding and internal winding. The external winding heat exchange coils are completely isolated from the oil, and the tube wall is not corroded by the fuel oil, which prevents the fuel oil from being contaminated by the leakage of the heat transfer oil. At the same time, it avoids the scaling of the heat exchange coil tube wall, improves the reliability of the system heat exchange, and reserves space for the low-speed agitator built into the fuel tank.

[0038] Compared with the equal pitch condensing coil, the initial spiral pitch of the outer winding variable pitch condensing coil is reduced, the contact area between the bottom condensing coil and the oil tank is increased, the effective heat exchange area is enlarged, the bottom heat flux continues to increase, the heat exchange rate is further improved, the fuel at the bottom of the oil tank flows upward faster, the convection effect of each temperature layer in the tank is enhanced, the heat transfer and flow characteristics of the oil tank are improved, the temperature difference between the upper and lower parts of the oil tank is reduced, and the thermal stratification of the oil tank is improved. Therefore, for the outer winding variable pitch coil, reasonably reducing the initial spiral pitch can improve the fuel flow and heat transfer performance.

[0039] As a further optimization scheme of the fuel water injection and heating and cooling integrated system for fuel icing test of the present invention, the water injection system includes: a low-speed agitator;

[0040] The speed and torque of the low-speed agitator are controlled by the reducer above the agitator. The agitator is turned on during the water injection cycle to prevent the oil in the tank from increasing in viscosity due to low temperature when the temperature drops, which leads to difficulty in oil discharge. A vertical agitator is used, the mounting flange is bolted and fixed, and the blades are inserted into the fuel, which requires less space and can improve the oil quality.

[0041] As a further optimization scheme of the fuel water injection and heating and cooling integrated system for fuel freezing test of the present invention, the refrigeration unit includes: a secondary heat transfer oil circulation system;

[0042] The secondary heat transfer oil system pipeline is composed of a refrigeration evaporator coil, a second capillary tube, a third solenoid valve, a plate heat exchanger, a second compressor, a fourth solenoid valve, a second oil storage tank, a second electric regulating valve, and a second non-return valve. A secondary heat transfer oil with a large specific heat capacity is selected to exchange heat with the fuel oil through an externally wound refrigeration evaporator coil to ensure that the temperature difference on both sides of the heat exchange wall does not exceed 13°C to prevent the fuel oil from freezing on the wall. The secondary heat transfer oil, as an intermediate medium, needs to be temperature controlled by the primary heat transfer oil, and then heat exchanged with the fuel oil to control the fuel oil temperature. Cooling the fuel oil through the secondary heat transfer oil circulation system can improve the temperature control accuracy, enhance the system stability and reliability, and ensure the accuracy of the test.

[0043] As a further optimization scheme of the fuel water injection and cooling integrated system for fuel icing test of the present invention, the water injection system includes: an integrated design;

[0044] The common pipeline of the integrated fuel cooling and water injection system of the fuel freezing test is composed of a first ball valve, a motor pump group, a third one-way valve, a ninth solenoid valve, first and second filters (eleventh solenoid valve), a seventh solenoid valve, and a second ball valve, which improves equipment utilization while preventing test errors caused by oil transfer.

[0045] In addition, according to the test, the functional relationship between the saturated water content of fuel and temperature is:

[0046] P=57.44616+1.78542t+0.01921t 2

[0047] In the formula, P is the saturated water content of the fuel, PPM; t is the temperature of the fuel, °C. Therefore, the saturated water content corresponding to different temperatures is different. In order to improve the quality of the oil, the oil temperature needs to be kept constant during the water injection cycle. This integrated design can monitor the dynamic changes of the fuel temperature in real time through the temperature sensor during the water injection cycle, and ensure that the prepared water-containing fuel has a constant oil temperature during the preparation process by turning on the cooling system, reducing the test error and strictly meeting the airworthiness requirements.

[0048] Beneficial results of the present invention:

[0049] 1. The present invention designs an externally wound variable pitch condensing refrigerator coil for cooling the oil tank, which increases the heat exchange area and improves the heat exchange efficiency while ensuring reliability, avoiding scaling and corrosion, and installing a low-speed stirring device in the oil tank to prevent the oil from freezing.

[0050] 2. The present invention improves the cooling technology. On the basis of the original refrigerant cooling, a secondary heat transfer oil with a large specific heat capacity is added as an intermediate medium to exchange heat with the fuel through a variable pitch condensing coil to ensure that the temperature difference between the fuel and the refrigerant does not exceed 13°C, preventing free water from freezing on the heat exchange wall surface, meeting the airworthiness requirements while improving the heat exchange accuracy.

[0051] 3. The present invention integrates the independent heating and cooling system and the water injection system into an integrated operation, effectively solving the problem that the prepared water-containing fuel does not meet the airworthiness standards due to the change in oil temperature during the water injection cycle, and designs an operating process corresponding to this system, making the fuel freezing and water-containing fuel test more efficient and standardized. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of the process of the present invention;

[0053] Figure 2 A diagram of an integrated fuel cooling and water injection system for a fuel icing test of the present invention;

[0054] Figure 3It is a schematic diagram of the oil tank model of the outer-wound variable pitch condenser evaporator coil in the present invention;

[0055] Figure 4 This is a schematic diagram of a low-speed agitator built into the oil tank of the present invention;

[0056] In the figure, 1-condenser, 2-solenoid valve, 3-safety valve, 4-compressor, 5-capillary tube, 6-liquid storage tank, 7-check valve, 8-plate heat exchanger, 9-refrigeration evaporator coil, 10-low-speed agitator, 11-temperature sensor, 12-nozzle, 13-ball valve, 14-motor pump group, 15-filter, 16-electric regulating valve, 17-electric heater, 18-control box. DETAILED DESCRIPTION

[0057] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0058] Reference Figure 1 The working process of the fuel water injection and heating and cooling integrated system based on the fuel icing test of the present invention includes the following steps:

[0059] Designed an integrated fuel cooling and water injection system for the fuel icing test, and improved the system operation process; Figure 2 As shown, a fuel cooling and water injection integrated system for fuel freezing test is characterized by comprising a fuel tank, a refrigeration and heating unit, a hydraulic module and a control box.

[0060] The oil tank is provided with a temperature sensor and a low-speed agitator; the temperature sensor is used to sense the temperature of the oil in the oil tank, and the low-speed agitator is used to stir the oil in the oil tank to prevent the oil from freezing; the water injection port is respectively connected to the fifth solenoid valve, the first nozzle, the sixth solenoid valve, and the second nozzle in sequence for injecting water into the oil tank;

[0061] The refrigeration and heating unit includes an electric heater, first and second liquid storage tanks, a variable pitch coil of a refrigeration evaporator, first and second capillary tubes, a plate heat exchanger, and a condenser;

[0062] The hydraulic module comprises first to second ball valves, a motor pump group, first to third one-way valves, first to second filters, first to twelfth solenoid valves, first to third electric regulating valves, first to second safety valves, and first to second compressors;

[0063] The inlet of the oil tank is connected to one end of the second ball valve; the other end of the second ball valve is respectively connected to one end of the third electric regulating valve, one end of the seventh solenoid valve, one end of the thermal heater, and one end of the second safety valve through pipelines; the other end of the electric heater is connected to one end of the eighth solenoid valve; the other end of the third electric regulating valve, the tenth solenoid valve, and the oil return port are sequentially connected through pipelines; the other end of the seventh solenoid valve is respectively connected to the other end of the eighth solenoid valve, the other end of the second safety valve, one end of the second filter, and one end of the twelfth solenoid valve; the other end of the twelfth solenoid valve is connected to the oil supply port; the second filter, the first filter, and the ninth solenoid valve are sequentially connected;

[0064] The outlet of the oil tank, the first ball valve, the motor pump group, and one end of the third one-way valve are connected in sequence by pipelines; the other end of the third one-way valve is connected to the other end of the ninth solenoid valve and the other end of the eleventh solenoid valve;

[0065] The oil replenishing port is connected to one end of the first solenoid valve and one end of the first safety valve respectively; the other end of the first solenoid valve and the other end of the first safety valve are connected to the oil tank;

[0066] One end of the refrigeration evaporator coil is connected to one end of the second one-way valve; the other end of the second one-way valve is connected to the fourth solenoid valve and the second solenoid valve; one end of the second liquid storage tank is connected to the other end of the second electric regulating valve; the other end of the second liquid storage tank is connected to the fourth solenoid valve; the other end of the fourth solenoid valve, the second compressor, the hot side channel of the plate heat exchanger, the third solenoid valve, the second capillary tube, and the refrigeration evaporator coil are connected in sequence; one end of the cold side channel of the plate heat exchanger is connected to the second solenoid valve, the first capillary tube, and one end of the condenser in sequence; the other end of the cold side channel of the plate heat exchanger is connected to one end of the first one-way valve and one end of the first electric regulating valve; one end of the first liquid storage tank is connected to the first electric regulating valve; the other end of the first liquid storage tank is connected to the other end of the first one-way valve and one end of the first compressor; the other end of the first compressor is connected to the condenser;

[0067] The motor pump group is used to control the flow of external circulation and heating circulation fuel; the first to second filters are used to purify the oil in the external circulation and fuel output process, and filter the undissolved water; the electric regulating valve is used to control the return oil volume and the flow of thermal oil; the safety valve is used to adjust the required pressure of the system; the solenoid valve is used to control the flow of fuel entering the external circulation, heating circulation and the flow of the first and second thermal oil in the refrigeration circulation; the oil replenishment port is used to replenish the oil in the oil tank; the condenser uses water as a refrigerant to cool the first-level thermal oil;

[0068] The control box is composed of a box body, PLC, frequency converter, buttons, knobs, indicator lights, temperature control, digital display instruments, etc., and is used to control the opening of the solenoid valve in the external circulation, heating cycle, and refrigeration cycle, the speed of the motor pump group, and the speed of the first and second compressors.

[0069] Step 1), manually open the first and second ball valves in the external circulation, and the control box controls the motor pump group, the seventh solenoid valve, the ninth solenoid valve, and the twelfth solenoid valve to open, so that the oil is injected into the fuel tank from the oil supply port, the twelfth solenoid valve, the seventh solenoid valve, and the second ball valve in sequence;

[0070] Step 2), the fuel temperature is fed back through the temperature sensor arranged in the fuel tank to determine whether the oil temperature reaches the airworthiness requirement of 27°C;

[0071] Step 2.1), if it is higher than the set temperature, adjust the opening of the first and second electric regulating valves and the speed of the first and second compressors through the control box, open the second, third and fourth solenoid valves, so that the first-level heat transfer oil circulates from the first liquid storage tank, the first compressor, the condenser, the first capillary, the second solenoid valve, the plate heat exchanger, and the first check valve in sequence; the second-level heat transfer oil circulates from the second liquid storage tank, the fourth solenoid valve, the second compressor, the plate heat exchanger, the third solenoid valve, the second capillary, and the refrigeration evaporator coil in sequence;

[0072] Step 2.2), if it is lower than the set temperature, close the seventh solenoid valve through the control box, open the eighth solenoid valve, and dynamically adjust the heating power of the electric heater, so that the fuel flows from the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the eleventh solenoid valve, the eighth solenoid valve, the electric heater, the second ball valve and then back to the fuel tank for circulation;

[0073] Step 2.3), if the set temperature is reached, the control box closes the first and second electric regulating valves, closes the second, third, fourth and eighth solenoid valves, closes the first and second compressors, and opens the seventh solenoid valve;

[0074] Step 3), close the ninth solenoid valve through the control box, open the fifth, sixth and eleventh solenoid valves, start the low-speed agitator, and inject free water into the fuel through the first and second nozzles at a flow rate of about 55 ml / min at a ratio of oil to water of 1000:1. If the water content meets the airworthiness standard, close the fifth and sixth solenoid valves, and the fuel passes through the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the ninth solenoid valve, the first and second filters, the seventh solenoid valve, and the second ball valve in sequence and then returns to the fuel tank for circulation;

[0075] Step 4), when the water injection volume meets the airworthiness standard, continue to circulate for about 30 minutes to ensure complete mixing and form saturated fuel. During this period, the fuel temperature must still meet the set value. If the temperature deviates from the set value, repeat step 2;

[0076] Step 5), if the cycle meets 30min, open the tenth solenoid valve and the third electric regulating valve through the control box, manually close the second ball valve, and the fuel will flow out from the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the eleventh solenoid valve, the seventh solenoid valve, the third electric regulating valve, the tenth solenoid valve, and the oil return port in sequence. After all the oil in the fuel tank is drained, close the motor pump group and the solenoid valve in the external circulation through the control box, manually close the first ball valve, and the preparation is completed.

[0077] Designed a variable pitch refrigeration evaporator coil with oil tank external winding, such as Figure 3 As shown, the coil uses DN30 copper tube, and the outside of the coil is covered with insulation material to ensure thermal insulation. The pitch of the coil adopts a variable pitch from the initial 25mm to 75mm. Compared with the fixed pitch coil with a constant pitch of 50mm, the contact area between the bottom condensing coil and the fuel tank is increased, the effective heat exchange area is increased, the bottom heat flux continues to increase, the heat exchange rate is further improved, and at the same time, the fuel on the top of the fuel tank is accelerated to flow downward to reduce the temperature difference between the upper and lower parts of the fuel tank, improve the thermal stratification of the fuel tank, and improve the heat transfer performance.

[0078] A low-speed agitator built into the oil tank is designed based on the speed and torque of the reducer, such as Figure 4 As shown, the stirrer is installed on the top cover of the fuel tank, and the stirrer is turned on during the water filling process to prevent the fuel in the fuel tank from increasing in viscosity due to low temperature when cooling down, which leads to difficulty in oil discharge. A vertical stirrer is used, the mounting flange is bolted and fixed, and the blades are inserted into the fuel, which requires less space and can improve the oil discharge quality.

[0079] In summary, the present invention adopts a variable pitch condensing evaporator wound outside the oil tank to cool the oil, and sets up a secondary heat transfer oil circulation pipeline to avoid direct heat exchange between the refrigerant and the fuel, effectively combines the originally independent cooling system and the water injection circulation system, and builds an agitator in the oil tank to prevent the oil in the oil tank from freezing. This integrated system can achieve precise temperature control and improve temperature control efficiency. It can keep the oil temperature constant during the circulation process of preparing water-containing fuel to meet the airworthiness requirements, and provides a new method for preparing water-containing fuel for fuel freezing tests in actual engineering.

Claims

1. A fuel water injection and cooling integrated system for fuel icing test, characterized in that: It includes oil tank, refrigeration and heating unit, hydraulic module and control box. The oil tank is provided with a temperature sensor and a low-speed agitator; the temperature sensor is used to sense the temperature of the oil in the oil tank, and the low-speed agitator is used to stir the oil in the oil tank to prevent the oil from freezing; the water injection port is respectively connected to the fifth solenoid valve, the first nozzle, the sixth solenoid valve, and the second nozzle in sequence for injecting water into the oil tank; The refrigeration and heating unit includes an electric heater, first and second liquid storage tanks, a variable pitch coil of a refrigeration evaporator, first and second capillary tubes, a plate heat exchanger, and a condenser; The hydraulic module comprises first to second ball valves, a motor pump group, first to third one-way valves, first to second filters, first to twelfth solenoid valves, first to third electric regulating valves, first to second safety valves, and first to second compressors; The inlet of the oil tank is connected to one end of the second ball valve; the other end of the second ball valve is respectively connected to one end of the third electric regulating valve, one end of the seventh solenoid valve, one end of the electric heater, and one end of the second safety valve through pipelines; the other end of the electric heater is connected to one end of the eighth solenoid valve; the other end of the third electric regulating valve, the tenth solenoid valve, and the oil return port are sequentially connected through pipelines; the other end of the seventh solenoid valve is respectively connected to the other end of the eighth solenoid valve, the other end of the second safety valve, one end of the second filter, and one end of the twelfth solenoid valve; the other end of the twelfth solenoid valve is connected to the oil supply port; the second filter, the first filter, and the ninth solenoid valve are sequentially connected; The outlet of the oil tank, the first ball valve, the motor pump group, and one end of the third one-way valve are connected in sequence by pipelines; the other end of the third one-way valve is connected to the other end of the ninth solenoid valve and the other end of the eleventh solenoid valve; The oil replenishing port is connected to one end of the first solenoid valve and one end of the first safety valve respectively; the other end of the first solenoid valve and the other end of the first safety valve are connected to the oil tank; One end of the refrigeration evaporator coil is connected to one end of the second one-way valve; the other end of the second one-way valve is connected to the fourth solenoid valve and the second solenoid valve; one end of the second liquid storage tank is connected to the other end of the second electric regulating valve; the other end of the second liquid storage tank is connected to the fourth solenoid valve; the other end of the fourth solenoid valve, the second compressor, the hot side channel of the plate heat exchanger, the third solenoid valve, the second capillary tube, and the refrigeration evaporator coil are connected in sequence; one end of the cold side channel of the plate heat exchanger is connected to the second solenoid valve, the first capillary tube, and one end of the condenser in sequence; the other end of the cold side channel of the plate heat exchanger is connected to one end of the first one-way valve and one end of the first electric regulating valve; one end of the first liquid storage tank is connected to the first electric regulating valve; the other end of the first liquid storage tank is connected to the other end of the first one-way valve and one end of the first compressor; the other end of the first compressor is connected to the condenser; The motor pump group is used to control the flow of external circulation and heating circulation fuel; the first to second filters are used to purify the oil in the external circulation and fuel output process, and filter the undissolved water; the electric regulating valve is used to control the return oil volume and the flow of thermal oil; the safety valve is used to adjust the required pressure of the system; the solenoid valve is used to control the flow of fuel entering the external circulation, heating circulation and the flow of the first and second thermal oil in the refrigeration circulation; the oil replenishment port is used to replenish the oil in the oil tank; the condenser uses water as a refrigerant to cool the first-level thermal oil; The control box is composed of a box body, PLC, frequency converter, buttons, knobs, indicator lights, temperature control, digital display instruments, etc., and is used to control the opening of the solenoid valve in the external circulation, heating cycle, and refrigeration cycle, the speed of the motor pump group, and the speed of the first and second compressors.

2. The integrated fuel water injection and heating and cooling system for fuel icing test according to claim 1 is characterized in that: The following steps are involved: Step 1), manually open the first and second ball valves in the external circulation, and the control box controls the motor pump group, the seventh solenoid valve, the eleventh solenoid valve, and the twelfth solenoid valve to open, so that the oil is injected into the fuel tank from the oil supply port, the twelfth solenoid valve, the seventh solenoid valve, and the second ball valve in sequence; Step 2), the fuel temperature is fed back through the temperature sensor arranged in the fuel tank to determine whether the oil temperature reaches the airworthiness requirement of 27°C; Step 2.1), if it is higher than the set temperature, adjust the opening of the first and second electric regulating valves and the speed of the first and second compressors through the control box, open the second, third and fourth solenoid valves, so that the first-level heat transfer oil circulates from the first liquid storage tank, the first compressor, the condenser, the first capillary, the second solenoid valve, the plate heat exchanger, and the first check valve in sequence; the second-level heat transfer oil circulates from the second liquid storage tank, the fourth solenoid valve, the second compressor, the plate heat exchanger, the third solenoid valve, the second capillary, and the refrigeration evaporator coil in sequence; Step 2.2), if it is lower than the set temperature, close the seventh solenoid valve through the control box, open the eighth solenoid valve, and dynamically adjust the heating power of the electric heater, so that the fuel flows from the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the eleventh solenoid valve, the eighth solenoid valve, the electric heater, the second ball valve and then back to the fuel tank for circulation; Step 2.3), if the set temperature is reached, the control box closes the first and second electric regulating valves, closes the second, third, fourth and eighth solenoid valves, closes the first and second compressors, and opens the seventh solenoid valve; Step 3), close the ninth solenoid valve through the control box, open the fifth, sixth and eleventh solenoid valves, start the low-speed agitator, and inject free water into the fuel through the first and second nozzles at a flow rate of about 55 ml / min at a ratio of oil to water of 1000:

1. If the water content meets the airworthiness standard, close the fifth and sixth solenoid valves, and the fuel passes through the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the ninth solenoid valve, the first and second filters, the seventh solenoid valve, and the second ball valve in sequence and then returns to the fuel tank for circulation; Step 4), when the water injection volume meets the airworthiness standard, continue to circulate for about 30 minutes to ensure complete mixing and form saturated fuel. During this period, the fuel temperature must still meet the set value. If the temperature deviates from the set value, repeat step 2; Step 5), if the cycle meets 30min, open the tenth solenoid valve and the third electric regulating valve through the control box, manually close the second ball valve, and the fuel is discharged from the fuel tank, the first ball valve, the motor pump group, the third one-way valve, the ninth solenoid valve, the first and second filters, the seventh solenoid valve, the third electric regulating valve, the tenth solenoid valve, and the return oil port in sequence. After all the oil in the fuel tank is drained, close the motor pump group and the solenoid valve in the external circulation through the control box, manually close the first ball valve, and the preparation is completed.

3. The integrated fuel water injection and heating and cooling system for fuel icing test according to claim 1 is characterized in that: The refrigeration system comprises: a condenser evaporator variable pitch coil; The velocity vector of the fluid in the variable pitch coil of the condenser evaporator changes continuously during the flow process, which will cause secondary circulation on the cross section and enhance the heat exchange. r Correct the average Nu for heat transfer oil: Where d is the inner diameter of the spiral tube, m; R is the radius of the spiral tube, m. r About 0.95, c of the spiral tube heat exchanger r It is about 1.

083. When the heat exchange area and pipe material are the same, the heat exchange capacity of the spiral tube heat exchanger is increased by 14% compared with the plate heat exchanger. The condenser evaporator coils are divided into two heat exchange modes: external winding and internal winding. The external winding heat exchange coils are completely isolated from the oil, and the tube wall is not corroded by the fuel oil, which prevents the fuel oil from being contaminated by the leakage of the heat transfer oil. At the same time, it avoids the scaling of the heat exchange coil tube wall, improves the reliability of the system heat exchange, and reserves space for the low-speed agitator built into the fuel tank. Compared with the equal pitch condensing coil, the initial spiral pitch of the outer winding variable pitch condensing coil is reduced, the contact area between the bottom condensing coil and the oil tank is increased, the effective heat exchange area is enlarged, the bottom heat flux continues to increase, the heat exchange rate is further improved, the fuel at the bottom of the oil tank flows upward faster, the convection effect of each temperature layer in the tank is enhanced, the heat transfer and flow characteristics of the oil tank are improved, the temperature difference between the upper and lower parts of the oil tank is reduced, and the thermal stratification of the oil tank is improved. Therefore, for the outer winding variable pitch coil, reasonably reducing the initial spiral pitch can improve the fuel flow and heat transfer performance.

4. The integrated fuel water injection and heating and cooling system for fuel icing test according to claim 1 is characterized in that: The water injection system comprises: a low-speed agitator; The speed and torque of the low-speed agitator are controlled by the reducer above the agitator. The agitator is turned on during the water injection cycle to prevent the oil in the tank from increasing in viscosity due to low temperature when the temperature drops, which leads to difficulty in oil discharge. A vertical agitator is used, the mounting flange is bolted and fixed, and the blades are inserted into the fuel, which requires less space and can improve the oil quality.

5. The integrated fuel water injection and heating and cooling system for fuel icing test according to claim 1 is characterized in that: The refrigeration unit comprises: a secondary heat transfer oil circulation system; The secondary heat transfer oil system pipeline is composed of a refrigeration evaporator coil, a second capillary tube, a third solenoid valve, a plate heat exchanger, a second compressor, a fourth solenoid valve, a second oil storage tank, a second electric regulating valve, and a second non-return valve. A secondary heat transfer oil with a large specific heat capacity is selected to exchange heat with the fuel oil through an externally wound refrigeration evaporator coil to ensure that the temperature difference on both sides of the heat exchange wall does not exceed 13°C to prevent the fuel oil from freezing on the wall. The secondary heat transfer oil, as an intermediate medium, needs to be temperature controlled by the primary heat transfer oil, and then heat exchanged with the fuel oil to control the fuel oil temperature. Cooling the fuel oil through the secondary heat transfer oil circulation system can improve the temperature control accuracy, enhance the system stability and reliability, and ensure the accuracy of the test.

6. The working steps of the fuel water injection and heating and cooling integrated system for fuel icing test according to claim 2 are characterized in that: The system comprises an integrated design; The common pipeline of the integrated fuel cooling and water injection system of the fuel freezing test is composed of a first ball valve, a motor pump group, a third one-way valve, a ninth solenoid valve, first and second filters (eleventh solenoid valve), a seventh solenoid valve, and a second ball valve, which improves equipment utilization while preventing test errors caused by oil transfer. In addition, according to the test, the functional relationship between the saturated water content of fuel and temperature is: P=57.44616+1.78542t+0.01921t 2 In the formula, P is the saturated water content of the fuel, PPM; t is the temperature of the fuel, °C. Therefore, the saturated water content corresponding to different temperatures is different. In order to improve the quality of the oil, the oil temperature needs to be kept constant during the water injection cycle. This integrated design can monitor the dynamic changes of the fuel temperature in real time through the temperature sensor during the water injection cycle, and ensure that the prepared water-containing fuel has a constant oil temperature during the preparation process by turning on the cooling system, reducing the test error and strictly meeting the airworthiness requirements.

Images