RU2234685C2 - Method of determination of fuel capacity on flying vehicle - Google Patents

Abstract

FIELD: in-flight determination of fuel capacity of flying vehicle.

SUBSTANCE: fuel capacity is determined at definite moment of time; then consumption of fuel is determined and amount of fuel consumed from test moment to present moment is calculated and difference between fuel capacity at test moment and amount of consumed fuel is displayed on indicators. Present consumption of fuel is determined by measured parameters of flight and parameters of power plant depending on consumption of fuel; if necessary, interpolation is performed. Fuel capacity is corrected by level sensors mounted in fuel tanks of flying vehicle. Flight parameters include speed, altitude and deviation of ambient air temperature from temperature at measured altitude by international standard atmosphere. Parameters of power plant: torque on engine shaft or revolutions of rotor or propeller , engine turbine exhaust gas temperature, power takeoff and air bleed-off.

EFFECT: reduced mass of measuring equipment; enhanced reliability.

6 cl, 3 dwg

Description

The invention relates to the field of aviation, in particular, to methods for determining the fuel supply on board an aircraft (LA). The preferred area of application is long-range aviation, especially civilian. The proposed method can be used both as a primary and as a backup.

Known requirements for airworthiness standards (NLGS), aviation regulations (AP) to the reliability of aircraft (LA) and their systems. Among the systems that are subject to stringent reliability requirements are aircraft systems for measuring the fuel supply on board.

Currently, the amount of fuel on board is determined using the following methods (Demotenko N.T., Kravets A.S. and other aircraft power plants. Systems and devices. - M.: Transport, 1976, pp. 178-180; Leshchiner LB, Ulyanov I.E. Designing of fuel systems of aircraft. - M .: Mashinostroenie, 1975, pp. 225-229):

1. By measuring the fuel level in the tank, followed by calculating the fuel supply based on the calibration characteristics of the tank (the dependence of the volume of fuel in the tank on its level). Fuel metering systems designed to implement this method include fuel level sensors installed in the fuel tanks, a processing and conversion unit for signals coming from the sensors, and an indicator. Sensors can be of various types: float (potentiometric), electrical capacitive, ultrasonic, etc. The disadvantage of this method is the dependence of the accuracy of determination on the position of the aircraft in space, on the correct installation of the sensors, on their number in the measured volume.

2. By measuring the flow of fuel flowing out of the tanks and entering the engines, with the subsequent calculation of the stock as the difference between the amount of fuel in the tank and the amount of fuel consumed. Flow meter systems include flow sensors installed in the fuel lines, a conversion unit, and an indicator. The disadvantage of this method is the accumulation of measurement errors during the flight.

A common disadvantage of the known methods is the significant weight (up to 1% of the weight of the fuel) of the fuel and flow meter systems that implement these methods, which increases the weight of the aircraft and worsens its flight performance.

In addition, the main drawback of such systems is the lack of reliability that does not meet modern requirements for reliability (AP and NLGS). To ensure reliability requirements, it is necessary to reserve fuel measurement channels or install two independent fuel supply determination systems on an airplane (usually one fuel meter and one flow meter - see: N. Demotenko, A. Kravets, and others. Aviation power plants. Systems and Devices. - M.: Transport, 1976, p. 180). At the same time, redundancy of systems does not meet the requirements of aviation rules if their conversion equipment is combined (in order to reduce weight) into a single complex.

At the same time, modern aircraft are equipped with computer systems that are independent of the fuel gauge and process the signals of numerous air navigation devices and are able to predict flight conditions.

Closest to the invention is a method implemented in the control system and measuring the fuel supply of the IL-114 aircraft (see: IL-114. Technical operation manual. Section 28. Fuel system. Subsection 28.40.00. Control devices and devices. Description and Work.). The system consists of three parts (ibid., P. 7):

- measuring, including fuel gauges, density sensor, fuel gauge block and indicators,

- computing, including a block of electronic transformations,

- automatic, consisting of signaling sensors.

During the operation of the system, continuous direct measurement of the mass of fuel in the tanks is carried out using fuel gauge sensors that convert the fuel level in the tanks into an electric capacity proportional to the fuel supply. At the same time, the current fuel consumption is continuously measured using flow sensors with the subsequent determination of the total fuel remaining on the plane. The system also controls other parameters of the fuel consumption process, and the parameters it determines are displayed on indicators. To increase reliability, the system provides redundancy of equipment.

The disadvantage of this complex system is the significant total weight of its components.

The objective of the invention is to reduce the weight of the technical means installed on the aircraft specifically for the purpose of determining the fuel supply, and increase the reliability of the technical means used for this.

The problem is solved using the method of determining the fuel supply on an aircraft (LA), according to which the fuel supply is determined at a control time and at the time following the control time, the current fuel consumption per unit time is determined, the amount of spent fuel is calculated as an integral of the current fuel consumption in unit of time from the control point in time to the current point in time, determine the fuel supply at the current time as the difference between the value of the fuel reserve in the control moment of time and the calculated amount of consumed fuel and display the fuel supply by means of indicators, which differs in that at the mentioned time following the control time, the current flight parameters and operation parameters of the aircraft power plant are measured and the current fuel consumption per unit time is determined using them a pre-prepared array, the elements of which are the fuel consumption values per unit time for sets of nodal values of the flight parameters and parameter aircraft powerplant operation, performing interpolation parameters when the measured values differ from the node values.

To eliminate the error accumulated during the determination of the fuel supply caused by the impossibility of taking into account all the parameters affecting the fuel consumption, the fuel supply is corrected by the signals of the discrete discrete fuel level sensors installed in the fuel tanks, while the moment the fuel reaches the fuel level installation level of the reference sensor.

As the measured flight parameters, the aircraft’s speed, flight altitude and the deviation of the outdoor temperature from the temperature at the measured flight altitude in the international standard atmosphere are used.

As a measured parameter of the power plant operation, one of the following parameters is used: the torque on the engine shaft, or the number of revolutions of the engine rotor, or the number of revolutions of the screw (for a turboprop engine), or the temperature of the gases behind the engine turbine.

As the measured parameters of the power plant, the value of the power take-off from the engine for the needs of the aircraft and the value of the air take-off for the needs of the aircraft are additionally used.

The method can be implemented in parallel with determining the fuel supply in another way. In this case, in the course of the flight, the fuel supply is determined in a different way, during the flight of the aircraft, the operability of the equipment that implements the other method is monitored and its readings are recorded, the failure time of the said equipment is used as a control moment, and the fuel supply at the control time is determined her testimony before the moment of refusal.

The present invention allows:

1. using the achievements of modern computer technology, implement the new principle of determining the fuel supply, which consists in the fact that the current fuel consumption is calculated in real time using the array entered into the computer, the elements of which are the fuel consumption values per unit time for sets of nodal parameter values flight (altitude, speed, outdoor temperature), and power plant operation parameters;

2. reduce the weight of the on-board fuel measuring equipment (TIA), since the sensors and information-measuring systems already on the aircraft are used to implement the proposed system, and the integrated on-board computer is used as a computer. Installed on the aircraft specifically for the implementation of the proposed method (but known) are only reference discrete fuel level sensors. The total weight of these sensors is significantly less than the weight of the known systems for measuring and indicating the fuel supply;

3. increase reliability, because the reliability of the elements included in the proposed system is clearly higher than the reliability of the currently used TIA.

The invention is illustrated by drawings.

Figure 1, 2 shows typical altitude and speed characteristics (BX) of aircraft engines: figure 1 shows the dependence of engine thrust P on flight speed V (or number M) in an international standard atmosphere (ISA) for various values of flight altitude N at a constant engine speed n and at constant values of power take-off ΔN and air take-off G _air from the engine for aircraft needs; figure 2 - dependence of the specific fuel consumption C _e on the flight speed V (or number M) under the conditions of the ISA for different values of the flight altitude N, at a constant engine speed n and at constant values of power take-off ΔN and air G _air from the engine aircraft needs.

Figure 3 shows the family of dependences of the current fuel consumption g on flight speed V calculated for a specific aircraft based on the VSH (Figs. 1 and 2) under ISA conditions for a steady-state flight mode at constant values of altitude H, power take-off ΔN and air G _air from the engine to aircraft needs.

The proposed method is as follows.

At some initial reference time t _to determine the value of the fuel supply G _to on the aircraft. This value is either predefined in the tests and is present in the calculator (for example, the maximum amount of fuel refueling in an aircraft), or is entered into it automatically from a sensor (for example, from a fuel level sensor corresponding to a fixed refueling option), or manually entered according to ground meters refueling. For example, as a control moment, you can select:

- the moment the engine starts to start,

- the moment the engines enter the mode after starting,

- take-off moment

- the moment of failure of other equipment for determining the fuel supply (i.e., the moment of disappearance of the health signal of this equipment),

- the moment the fuel level passes the reference sensor installed in the fuel tank at a height corresponding to the known fuel supply.

If the method is used from the beginning of engine start, then:

where G ₀ is the initial fuel supply,

Q ₀ is the initial volume of fuel,

ρ is the actual density of the fuel.

The moment the engines enter the mode after start-up can be selected as a control moment in order to simplify the calculations, since for a particular brand of the engine the amount of fuel used up at start-up is almost constant and can be taken into account as a correction. In this case:

where G ₃ is the amount of fuel needed to start the engines.

You can begin to determine the consumption and fuel supply of the proposed method at the time of failure of other fuel measuring equipment that implements a different method of determining the fuel supply. In this case, during the flight, the operability of other fuel measuring equipment is monitored and its readings are recorded, the moment of failure of this equipment is used as a reference point in time, and the readings of this equipment before the moment of failure are taken as fuel reserve.

After the control moment is selected and the fuel supply is determined at this moment, at the next moments of the flight time, the necessary current flight parameters and current parameters of the power plant are measured using appropriate sensors and the current fuel consumption per unit time g (t) is determined from them (i.e. fuel consumption at the current moment of time) using an array of dependencies of fuel consumption of aircraft on these parameters, previously calculated and refined according to the results of flight tests. Elements of this array represent the fuel consumption per unit time for sets of nodal values of the measured parameters. The fuel consumption corresponding to actual, other than nodal, values of the parameters measured during the flight is calculated by the interpolation method indicated above. The method for calculating the elements of this array is described below.

For each of the time points for which the current fuel consumption is determined, the amount of spent fuel G _{p is} calculated as the integral of the total current fuel consumption g (t) from the control moment t _to to the current t:

The fuel supply at the current moment G _{t the} current (indicated) reserve is determined as the difference between the fuel supply at the control moment G _to and the amount of fuel consumed G _p :

The current fuel supply is displayed using an indication tool.

To eliminate the accumulation of calculation errors and improve the accuracy of readings (especially at the end of the flight), the fuel supply is adjusted. For this, the signals of discrete fuel level sensors and fuel density sensors installed in the fuel tanks are used, and the moment when the fuel level reaches the response level of the next reference sensor is taken as a control point in time. At the moment the sensor is triggered, the fuel supply is determined as follows:

where Q _rep - the amount of fuel corresponding to the level of response of the reference sensor (reference volume),

ρ is the density of the fuel, depending on the temperature and grade of fuel.

After the correction, they continue to determine the fuel supply by the measured flight and power plant parameters.

From the literature, methods are known for calculating the dependences of an aircraft fuel consumption per unit time on flight parameters and power plant operation parameters. These dependencies are used in the design and testing of aircraft.

As an example, we can cite a method based on the use of high-speed characteristics of the engine (VSH). The VSH of the engine is called the dependence of thrust and specific fuel consumption on altitude and flight speed (see: Aircraft mechanics: Flight dynamics: Textbook for aviation universities / A.F. Bochkarev et al., 2nd ed. - M .: Mechanical Engineering, 1985 , p. 44). Engine VSH are part of the technical documentation for the engine, and the methodology for their determination is described in the literature (for example, ibid., Pp. 44-72). VSH specify according to the results of flight tests.

Thus, for aircraft engines, the altitude and speed characteristics of the type shown in Figs. 1 and 2 are known, namely, the set of dependencies of the thrust values P and specific fuel consumption C _{e of the} engine (C _e is the mass flow rate of fuel per unit of thrust per unit time) versus speed V (number M) of flight for a number of values of heights H, engine rotor speed numbers n (or M _cr is the torque on the engine shaft, or n _in is the rotational speed of the screw for a turboprop engine, or T _tr is the temperature of the gases behind the engine turbine ), power take-offs ΔN and air G _air from d drive and for a number of atmospheric parameters characterizing deviations from the ISA.

The calculation of the fuel consumption of aircraft can be performed in the following order.

1) From the mathematical model of the engine, supplied by the manufacturer of the engine, a family of altitude-speed characteristics (VCR) of the engine is distinguished, set graphically, or tabularly, or in the form of computer calculation programs. As mentioned, BCX are functions:

and

where P is the engine thrust;

С _е - specific fuel consumption per engine: С _е = g / Р, i.e. fuel consumption by one engine per unit of thrust per unit of time;

a ₁ , a ₂ , ..., a _m are considered flight parameters and power plant operation parameters.

The following flight parameters can be used as a ₁ , a ₂ , ..., a _m :

V and H speed and flight altitude, respectively;

ΔT deviation of the temperature of the outside air T from the air temperature at a height H according to the MSA TN _ms , ΔT = T-TH _ms ;

and the following parameters of the power plant:

G _air - air intake from the engine for the needs of the aircraft;

ΔN - power take-off from the engine for the needs of the aircraft;

Dr is the parameter of operation of the power plant from among the measured ones, which uniquely determines the engine operating mode, which can be selected as the torque on the motor shaft M _cr , or the rotor speed of the engine n, or the rotational speed of the screw n _in (for the theater) engine turbine T _Tr .

By asking for each of the m parameters included in formulas (6) and (7) a series of nodal values, an m-dimensional array of nodal values of fuel consumption per unit time g for an aircraft engine is calculated:

The number of parameters m, on which the fuel consumption depends (for example, V, Н, ΔТ, G _air , ΔN, Dr), and the step of each parameter in the range of its possible change are determined by the presence of it in the mathematical model of the engine, the influence of a specific parameter on the thrust Р and specific consumption С _е , the degree of influence of this parameter on fuel consumption g, the required accuracy of determining fuel consumption g.

2) The resulting array of nodal values of fuel consumption can be refined by the results of flight tests of aircraft. For this:

2.1) Calculate, according to well-known aeromechanical formulas, the required thrust for a steady-state flight mode, characterized by altitude H and speed V (under MCA-ΔT = 0), the thrust of one engine (P _mass ) corresponding to the actual weight of the aircraft G _la :

wherein q - velocity head, q = f _{4 (V, H) = ρ h} · V ^2/2;

i _dv is the number of engines;

S is the wing area of the aircraft;

Cx is the drag coefficient of aircraft determined by the airplane’s polar obtained in flight tests Cx = f (Cy) for the corresponding value of the coefficient of lift Sy;

ρ _h - air density at a height of N.

In horizontal flight mode:

where α is the angle of attack of the aircraft, determined by the dependence Su = f ₅ (α) obtained in flight tests;

φ is the angle of the engine,

G _la - the weight of the aircraft, which is equal to

where G _beg is the weight of the aircraft without fuel and cargo;

G _top - current fuel supply;

G _gr - the weight of the goods.

2.2) Using dependence (6), it is determined under the conditions of ISA, i.e. at ΔT = 0, the required engine operation mode, Dr _loss (N, V) as a function of N and V for the ΔN, G _air values recorded during the flight, corresponding to the required thrust, and then the estimated fuel consumption is calculated from (7):

2.3) Using _calc g (H, V) and the values of costs derived from flight testing and given to _{whether the} (H, V) ISA g conditions are corrected array nodal consumption values calculated by formula (8) as follows:

On an airplane, as a rule, measurement of power and air withdrawals for aircraft needs is not provided, therefore, it is necessary to calculate, according to formula (8), several arrays of nodal values of fuel consumption corresponding to various combinations of turning on / off aircraft systems that are consumers of power and air from the engine. These combinations are selected from the whole set of combinations possible in the operation of the aircraft, based on the following considerations:

a) Each of the selected combinations assumes the availability of selections necessary for the operation of those aircraft systems, the use of which is provided throughout the flight for normal operation of the aircraft.

b) Those combinations of switching on (off) interdependent aircraft systems that do not ensure the normal operation of these systems are excluded from the number of combinations selected.

c) Based on the analysis of the data obtained during the calculation of the arrays of nodal values of fuel consumption, a possible combination of those combinations of turning on (off) aircraft systems is made for which the values of the costs do not differ significantly.

When determining fuel consumption in flight, based on the analysis of the current scheme of switching on (off) aircraft systems, automated selection of nodal values of fuel consumption from a number of pre-formed according to the above algorithm is performed.

For example, an array of nodal expenditure values may include sets of elements corresponding to:

- the consumption of power and air flow from the engine by aircraft systems operating throughout the flight, and the disconnected state of consumers who do not work continuously;

- the consumption of power and air flow from the engine by aircraft systems operating throughout the flight plus the inclusion of an anti-icing system (PIC),

- the consumption of power and air flow from the engine by aircraft systems operating throughout the flight plus the inclusion of an air conditioning system (SC),

- the consumption of power and air flow from the engine by aircraft systems operating throughout the flight plus the inclusion of PIC and SC, and so on.

The method can be implemented using a system that contains a set of sensors that measure flight parameters and engine parameters, the outputs of which are connected to the inputs of the calculator, which also includes a storage device and a timer and an output connected to an indicator. An array of nodal values of fuel consumption, adjusted according to the results of flight tests g _cor. . In the process of the system’s operation, the calculator provides continuous real-time calculation of the current fuel consumption corresponding to the current readings of the mentioned sensors by interpolating the nodal values of fuel consumption by array elements and calculating the fuel supply value for the aircraft, which is then fed to the indicator.

As a system calculator, an integrated on-board computer can be used, for example, BTsVM-90 (developed by GUP OKB Elektroavtomatika, St. Petersburg) or EIV-7000 (developed by Rockwell-Collins, USA). Both of these computers incorporate memory devices and timers and have high reliability and sufficient speed to perform real-time calculations.

The system includes sensors that determine flight speed and altitude, air temperature sensors, engine speed or torque sensors on engine shafts. As sensors that determine the speed and altitude of the flight, navigation sensors can be used.

The system also contains discrete fuel level sensors and fuel density sensors installed in the fuel tanks. Their outputs are connected to the inputs of the calculator. These sensors are intended for correction according to the formula (5) of the calculated fuel reserve. At the same time, reference sensors record moments when the fuel level corresponds to the height at which the corresponding sensor is installed. Fuel density sensors are designed to determine the mass of fuel by its volume, determined by reference sensors.

Claims (6)

1. The method of determining the fuel supply on an aircraft (LA), according to which the fuel supply is determined at a reference time and at the time following the control time, the current fuel consumption per unit time is determined, the amount of spent fuel is calculated as an integral of the current fuel consumption per unit time from the reference point in time to the current point in time, determine the fuel supply at the current point in time as the difference between the value of the fuel reserve at the control point in time and calculates the actual amount of fuel consumed and display the fuel supply by means of indicators, characterized in that at the following time points the current flight parameters and the operation parameters of the aircraft power plant are measured and the current fuel consumption per unit time is determined using a pre-prepared array, the elements of which are the values of fuel consumption per unit time for sets of nodal values of flight parameters and operation parameters of the aircraft power plant, about uschestvlyaya interpolation parameters when the measured values differ from the node values. 2. The method according to claim 1, characterized in that the fuel supply readings are corrected by the signals of the reference discrete sensors of the fuel level installed in the fuel tanks, while the moment when the fuel level reaches the installation level of the reference sensor is taken as a control point in time. 3. The method according to any one of claims 1 and 2, characterized in that as the measured flight parameters use the speed of the aircraft, flight altitude and the deviation of the temperature of the outside air from the temperature at the measured flight altitude in the international standard atmosphere. 4. The method according to any one of claims 1 to 3, characterized in that one of the following parameters is used as the measured parameter of the power plant operation: torque on the engine shaft, or the number of revolutions of the engine rotor, or the number of revolutions of the screw (for a turboprop engine) , or the temperature of the gases behind the engine turbine. 5. The method according to claim 4, characterized in that as the measured parameters of the power plant, additionally use the value of the power take-off from the engine for the needs of the aircraft and the value of the air take-off for the needs of the aircraft. 6. The method according to any one of claims 1 to 5, characterized in that the fuel supply is determined in another way, during the flight of the aircraft, the operability of the equipment that implements the other method is monitored and its readings are recorded, the failure time of the aforementioned is used as a control moment equipment, and the fuel supply at a reference time is determined by its indications before the moment of failure.

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