Automatic monitoring and metering system for pipeline fuel supply for multiple aircraft types

    Abstract: An automatic monitoring and metering system scheme for pipeline fuel supply of multiple aircraft types was proposed, and a single-machine centralized control and distributed control model was developed to realize automatic control of pipeline fuel supply for multiple aircraft types, and achieved good results in practical applications. Effect.

    Keywords: Monitoring pipeline oil supply network system field bus

In a multi-type aircraft pipeline fuel supply system, various technical parameters should continue to change with the type and model of refueling aircraft and the number of simultaneous refueling aircraft. In order to ensure that all technical parameters during the refueling process can meet the needs of the refueling aircraft, an automated system for automatic monitoring must be established. To this end, we have successfully developed a single-machine centralized control and distributed control model to achieve automatic monitoring, measurement and management of pipeline fuel supply for multiple aircraft types.

1 Main technical requirements

(1) Remote control of oil pump

Realize that the pump room is unattended, and the working status of the oil pump is reflected on the computer screen in the central control room, and the oil pump is remotely controlled through the computer.

(2) Monitoring the liquid level of oil tanks in use

During the refueling process, it is very necessary to monitor the liquid level in the oil tank. The system should be able to monitor the liquid level of the oil tank in real time, vividly display the collected liquid level value on the computer screen, and set up a limit alarm device.

(3) Monitoring of oil pressure

In order to meet the oil pressure needs of aircraft when refueling, the pressure gauge signals installed on the pipeline at the outlet of the oil pump, on the oil main pipe, etc. are sent to the computer and monitored according to different aircraft types and different refueling methods.

(4) Monitoring of oil temperature

A temperature sensor is installed at the junction of the oil pipeline and the branch pipe. The sampling period is within 1 second and the temperature resolution is less than 0.1 degrees.

(5) Automatic measurement conversion

Using the weight (mass) of the oil in the air as the calculation standard, the measured oil temperature is converted to the performance temperature at that time, and then the weight is calculated based on the accumulated count of the added oil body.

(6) Automatically identify machine number

In order to prevent oil from flowing out, the aircraft number identification function is set up. The on-site controller implements aircraft identification through an IC card. The IC card also has management functions and can store refueling passwords and record refueling quantities.

(7) Output printing

① Can print out the current refueling list of each aircraft and the cumulative refueling list for ten days, months, quarters and years; ② Print the total refueling list of the aircraft on the day; ③ Print the total refueling list for ten days and months; ④ Print other required information.

(8) For the safety of the refueling system itself and the refueling operation process, a variety of protection functions are set up, mainly including:

①Oil overpressure protection

Track and detect the oil pressure in the system. If the oil pressure exceeds the limit due to water hammer or failure, on the one hand, the pump will be stopped to stop refueling, and on the other hand, the safety valve leading to the vent tank pipeline will be opened to relieve the pressure.

②Pump abnormality protection

The oil pump control cabinet of the refueling system has various protections such as overload, overheating, voltage overvoltage/undervoltage, overcurrent, power short circuit, and open circuit.

2 System structure and working principle

2.1 Hardware structure

Considering actual needs and economic issues, we designed two systems: single-machine centralized control and distributed control.

2.1.1 Single-machine centralized control system

The hardware structure block diagram of the single-machine centralized control system is shown in Figure 1. The central computer adopts PC bus 486 industrial computer with 8M memory. The expansion interface templates include: photoelectric isolation analog input board (32 channels, 12 bits), pulse input board (12 channel, 16 bits), photoelectric isolation switching output board (32 channels). Signal conditioning realizes the isolation, amplification, I/V conversion and shaping of on-site signals to improve the anti-interference performance of the system. On-site sensors and valves are centrally powered by the system, which provides 24V and 12V DC regulated power supplies.

2.1.1 Distributed control system

The hardware structure block diagram of the distributed control system is shown in Figure 2. This system adopts "centralized management and decentralized control" as a large-scale design. A field controller is designed at each fuel port to directly control each fuel port. The central computer controls and manages the field controller through the BITBUS field bus to realize the system monitoring and statistical processing of information. Due to decentralized control, when the central computer or a certain control unit fails, other control units will continue to work, improving the reliability of the system.

The on-site controller accepts keyboard operation information and reads aircraft refueling information from the IC card to implement flow measurement, pressure and temperature inspection, and electro-hydraulic valve control. The field controller consists of a STD industrial computer CPU template, communication board, I/O template, and analog input board to form a minimum system. In addition, there are extended IC card readers, keyboards, monitors, etc.

2.2 Software structure

The software development language is C language and is divided into the following parts:

(1) Data collection, digital filtering, unit conversion;

(2) Refueling parameter control;

(3) Refueling information processing (system and reports);

(4) Network communication (distribution system);

(5) System measurement calibration and auxiliary tools;

(6) IC card issuance system (distribution system);

(7) On-site controller data collection and processing, refueling control and network communication.

2.3 System structure

The automatic monitoring and metering system mainly consists of on-site sensors, flow meters, electro-hydraulic valves, on-site controller signal processing units and central control room computers.

2.3.1 Signal conditioning part and separation auxiliary instruments

Taking the system's signal system into consideration, the signal conditioning circuit was optimized and designed, including signal isolation and amplification circuit, shaping and limiting circuit, and signal conversion circuit to respectively complete electro-hydraulic valve control and flow meter pulse signal shaping and level conversion. , temperature and liquid level sensor current/voltage conversion. The circuit design makes full use of isolation and filtering technology to effectively reduce external interference.

2.3.2 Flow measurement and calibration

Flow measurement is key to implementing refueling control, process monitoring, refueling systems and recorders. Flow measurement adopts waist wheel flow meter and photoelectric flow converter. The converter outputs a pulse signal, which improves the signal's anti-interference ability and measurement accuracy.

2.3.3 Field controller and IC card application

As the lower computer of the distributed control system, the on-site controller controls and measures the fuel inlet and communicates with the upper computer.

The main functions completed by the on-site controller are: refueling process control, measurement, communication, and IC card reading and writing. The system is set up with two refueling methods: one is quantitative refueling; the other is arbitrary amount refueling. Do not enter the setting value for any refueling method. After reading the aircraft refueling information through the IC card or inputting the aircraft refueling information through the keyboard and confirming refueling, the controller starts the solenoid valve to implement refueling and performs flow measurement at the same time. The refueling quantity is written into the IC card and uploaded to the host computer at the same time.

In order to improve the anti-interference ability of the on-site controller, measures have been taken in the following aspects:

(1) The input signal is optically isolated to prevent interference signals from entering;

(2) Use switching stabilized power supply to prevent power frequency interference;

(3) The casing is well shielded to prevent electromagnetic interference;

(4) Set up WATCHDOG to further improve the anti-interference and reliability of the system in terms of software.

The system uses IC cards for airport fuel supply management, which improves work efficiency and can be read and written up to 100,000 times. SEL4442 stores 256 bytes and can store aircraft number, activation time, password, the last 10 refueling times and refueling volume. When refueling begins, the on-site controller powers up the card and verifies the card's password. After the password is correct, read the aircraft number in the card and allow refueling of the aircraft. During the refueling process, always check the status of the card to confirm the existence of the card and write the current value to avoid drawing the card before the refueling is completed. It has a unified card issuance system, and the system password and aircraft number are written into the card for aircraft refueling.

2.3.4 On-site network

At the aircraft refueling site, there are many interference factors and strong interference signals. Therefore, the BITBUS communication network suitable for industrial site applications is selected, using shielded twisted pairs as the transmission medium. The BITBUS network electrical interface complies with the RS485 electrical standard and adopts self-synchronization mode. Its performance parameters are as follows:

Rate distance/number of segment nodes/segment transmission line

62.5kbps 1200m 28 (250 allowed) 1 pair

The BITBUS communication protocol frame format is as follows:

The information data format used by the system is as follows (text length is 20 bytes):

5 digits of aircraft number

Refueling status flag 1 bit

Preset refueling volume 3 digits

Refueling capacity 3 digits

Current fuel volume: 3 digits

Oil filler 1 position

4 places reserved

2.3.5 Selection of control valves

In the managed refueling of multiple aircraft types, the oil flow rate and pressure in the pipe are large, and the closing time of the ordinary solenoid valve is uncontrollable. During pressure refueling, a large water hammer pressure will be generated, causing damage to pipelines and instruments. Although the electric regulating valve can realize the control of closing the valve, its control is complicated and expensive, so the system uses an electro-hydraulic valve as the switch control.

Fuel security for multiple aircraft types is an important issue we are currently facing, and realizing automatic monitoring and measurement of pipeline fuel supply systems for multiple aircraft types is a necessary prerequisite and means for fuel security for multiple aircraft types. The realization of automatic monitoring and measurement of various aircraft pipeline fuel supply systems effectively ensures the implementation of fuel guarantee for multiple types of aircraft.