燃油量計算中的自動溫度補償(FueTC

1、 Measurement 24(1998103108Automatic temperature compensation in fuelvolume counting (FueTC E.Kayafas *,S.Katsikas,T.Patavalis,V.LoumosMultimedia Technology Laboratory,National Technical University of Athens,Department of Electrical and Computer Engineering,Division of Computer Science,Athens,GreeceA

2、bstractFueTC is an initiative aiming to solve inaccuracy problems,at fuel mass measurements.These problems are caused by the well-known phenomena of thermal contraction and expansion.All the parameters involved and the underlying physical processes are presented.A brief description of the systems ar

3、chitecture,some preliminary experimental measurements and a simple comparison to the theoretically calculated values are also presented.Concluding remarks and a brief discussion on future perspectives are also included in this paper.©1998Elsevier Science Ltd.All rights reserved.Keywords:Compens

4、ation;Fuel;Micro-controller design;Temperature measurement;Volume measurement1.Introductiondepartments,after loading with a known mass of fuel and transferring the whole contents of the department,when unsealed.The FueTC design is One of the basic problems in fuel transportation is the di culty in e

5、stimating accurately the fuel an attempt at a simple solution of this problem by using basic techniques.mass under non-constant temperatures.This inac-curacy originates from the well-known phenomena The FueTC is a project for the construction of an advanced fuel volume counter,which is devel-of ther

6、mal contraction and expansion that a ect liquid volume measurements 1,2.The volume of oped in the National Technical University of Athens (NTUAwith the assistance of fuel trans-a specic fuel mass changes proportionally to the temperature.Therefore,an accurate mass measure-port companies,who provided

7、 useful information.The designed apparatus,called FueTC,measures ment without the uncertainty of the volume quan-tity introduced at the transportation and delivery the volume and samples the temperature to calcu-late the exact fuel mass.It then converts the mass from the oil reneries to the market,w

8、ould be something o volume under a reference temperature.Currently,volume counters are used for measur-ing the fuel transfers and several techniques are used in order to protect the consumer 3.One of 2.Basic calculationsthese techniques is the sealing of fuel-wagonThe fuel volume variation

9、s as a function of *Corresponding author.E-mail:kayafascs.ntua.grtemperature are measured in terms of the physical0263-2241/98/$see front matter ©1998Elsevier Science Ltd.All rights reserved.PII:S0263-2241(9800040-2104 E.Kayafas et al./Measurement24(1998103108quantitydensity4,which is dened as

10、the fraction of fuel mass over its volume at a giventemperature.The S.I.unit of density is kg/l.density=mass/volume(kg/l.2.1.Density estimationThe density is a function of temperature.Theanalytical description of this function is not alwaysavailable,and often becomes complicated whenreal time measur

11、ements are required.This problemcan be skipped by using standard pre-calculatedFig.1.Description of the system.tables that map temperatures to density values fora given fuel type.The tables used for this purposeare those given by Saybolt5.It is sucient toconstruct a break-point table for every5°

12、;C incre-3.1.Embedded micro-controllermental temperature.The midpoints are linearlyinterpolated using the function of Eq.(1below:Our system,the FueTC,is based on the Intel80196-KD micro-controller.It is a16bit CHMOS density=a×temperature+b.(1micro-controller operating at20MHz,designedto handle

13、high-speed calculations and fast The constants a and b are specied in the tables.input/output operations.There is also an eight The density at15°C(60Fdenes the exact typechannel A/D converter.The microprocessor of petroleum6.receives and processes the input data in order tocompute the fuel volu

14、me under a reference temper-2.2.Volume estimation ature7.The input data are the reference temper-ature and the actual fuel temperature,the pulses The next step is fuel mass calculation,using produced by a volume counter,the type of fuel formula(1.Thenal step is to determine the and the K-factor of t

15、he specic volume counter. volume under dierent temperatures.The user denes some of the previous inputs,while The process described can be formulated as the rest are taken directly from the measuring follows:instruments(Fig.2.mass=volume(temperature A3.2.Description of system inputs×density(temp

16、erature AA short description of the system inputs is volume(temperature B=mass/densitygiven below.(temperature B.3.2.1.Power requirementsThe laboratory implementation of FueTC caneasily operate with a typical5V DC power source.3.Description of FueTC systemIt draws no more than500mA of current whenal

17、l the peripherals are operational(including a A common embedded micro-controller basedthermal printer.When some of the peripherals system was designed for the described apparatus are not in use,the power consumption can be kept (Fig.1.to a low100mA.It is expected that the production105E.Kayafas et a

18、l./Measurement24(19981031083.2.3.Measured temperature Temperature is measured with a sensor placedbefore theow meter.The fuel temperature isperiodically sampled during unload.The precisionof0.1°C is satisfactory for the needs of this applica-tion.It is estimated that even an accuracy of0.5°

19、;Cwould not signicantly aect the total fuel volumemeasurement(Fig..Reference temperatureThe total counted volume is reduced in thereference temperature,which can be set by theuser.FueTC is currently equipped with a16keykeypad for user input.Fig.2.Input signals.3.2.5.Type of fuelThe user,from

20、a list of pre-dened entries,selects the type of fuel.Alternatively,the user can version of FueTC will limit these requirementsmanually insert the characteristic fuel density at even further.15°C.There is also an option for using the APIgravity at60F in place of the density.Pulses from th

21、e volume counterThe FueTC can be used with any commonowmeter by reducing the fuelow into pulses. 3.2.6.K-factor constantCounting these pulses and using the K-factor con-This constant denes the exact number of pulses stant,the fuel volume is calculated.A pulse genera-received for1l of fuel.The K-fact

22、or S.I.unit is tor can be adapted on the pivot of anyow meter1/l.Its value depends on the specic type ofow in order to transform its rotations into pulses meter and pulse generator.The microprocessorcalculates the fuel volume by multiplying this (Fig.2. Fig.3.Discrepancies between standard and FueTC

23、 measurements.106 E.Kayafas et al./Measurement24(1998103108 Fig.4.Theoretical and measured values using FueTC.factor by the number of pulses received by the 3.3.2.Serial communication portA serial communication port(RS232has been ow meter.The precision of the fuel volumemeasurement is about103l,but

24、in general it included in the design in order to facilitate the depends on the specic K-factor magnitude.connection of FueTC with other digital devices The commonow meters often need re-calibra-(e.g.a computer.In this way,it is possible to tion due to wear.Therefore,the proportioncreate a computer r

25、ecord for post-process statistics between rotation and volume alters with time.from a large number of measurements performedby several FueTC devices.The advantages of such Modications to the mechanicalow meter can beavoided if a re-adjustment of the K-factor is set.a conguration are obvious.This pro

26、cedure is much easier and safer.Themodication of K-factor has been predicted inFueTC operation.The K-factor value is set using 4.Goals and advantagesa trimmer which is located inside the FueTCcaging,and it will be impossible for an ordinary The basic goals of the FueTC are ease of use, user to chang

27、e it without leaving any trace.reliability,compatibility and reasonable cost.4.1.Ease of use3.3.Description of the system outputsThe FueTC is designed to be easy to use.A help A short description of the system outputs isfacility is available at any time on the LCD. given below.4.2.Reliability3.3.1.L

28、CD and printerThe output peripherals of the FueTC are a A large number of tests under realistic condi-2×20dot matrix LCD display where all messagestions and with various types of fuel have been and measurement results are displayed and a ther-scheduled.These tests provide reliable measure-mal p

29、rinter for hard-copying the results.ments.The simplicity of the design guarantees the107E.Kayafas et al./Measurement24(1998103108 Fig.5.Discrepancies without temperature compensation for dierent types of fuel.advantage of a very robust system.Since the K-temperature compensation and FueTC at dierent

30、 factor can be secured against unauthorised adjust-temperatures is displayed in Fig.3.It is obvious ments,the system is suitable for purposes such as that the dierences are signicant.Fig.4presents customs control and governmental audits.the discrepancies between the theoretical valuesand the values

31、measured by the FueTC.These 4.3.Compatibilitydiscrepancies are due to temperature changesduring the measurement and cannot be estimated One of the basic advantages of the FueTC istheoretically.Fig.5shows the discrepancies that it can easily betted to any common type of between the measurements perfo

32、rmed by an old-ow meter already available in the market.Forstyle system without temperature compensation this settlement it is necessary to replace the and FueTC for dierent types of fuel.The dier-mechanical volume meter and add a simple pulseences are in proportion to the fuel density at15°C.

33、generator and a temperature sensor.As a result ofits compatibility,FueTC can be used in fuel-wagons,refuelling stations,ships and generally for 6.Future perspectivesall purposes where old-style meters are used.An interesting improvement would be the design 4.4.Low costof a new counter system with te

34、mperature compen-sation without aow meter.In this way,the use FueTC uses cheap and easily available compo-of a petrol pump could be avoided and there nents.This keeps the cost low.Also,the device is would be no lower limits for fuelow speed,as 100%solid state with no moving parts,which is athere are

35、 now.This can be realised by a design guarantee of remarkable reliability.that takes advantage of the Doppler phenomenon.The Doppler phenomenon is the changing of asignals frequency in proportion to the speed of 5.Experimental measurementsthe material in which the signal is transmitted.So,if we put

36、on a piece of pipe a signal transmitter The results of some laboratory experiments areand at least two receivers,we could estimate the presented.The discrepancies between the measure-ow of the fuel via the pipe by the change of the ments performed by an old-style system withoutsignals frequency.Then

37、 we could calculate the108 E. Kayafas et al. / Measurement 24 (1998 103108 fuels volume by knowing the dimensions of the pipe and its expansion factor. In this way, the use of a ow meter and a petrol pump would be avoided and there would be no limits for the fuels ow speed, as there are now. This improvement wou