CN1204770A - Method and device for determination disel oil grade and cetane number - Google Patents

Abstract

A device for measuring the grade number and cetane value of diesel oil is composed of capacitance-type sensor, capacitance/frequency converter and microprocessor. Its measuring method features that based on statistical rule a relational expression between the relative dielectric constant and the parameters including grade number (condensation point), relative density, middle boiling point, refractiveyindex and average molecular weight is created, the relative dielectric constant is measured by sensor and then processed in microprocessor to obtain the relative parameters, and the grade number and cetane value of diesel oil are calculated by well known equation.

Description

Diesel number and cetane test method method and device

The present invention relates to the determination techniques of diesel quality, is to measure the label of diesel oil and the method and the device of cetane rating specifically.

The fuel fraction of diesel motor is heavier, wherein contains a large amount of macromolecule alkane, when atmospheric temperature is reduced to a certain degree, because the crystallization of wax loses flowability diesel oil, uses and transportation brings difficulty thereby give.Though the congealing point of diesel oil can not be represented its minimum serviceability temperature, just begin have wax crystallization to separate out when should be before congealing point 5～10 ℃, they will stop up the aperture of fuel filter, reduce fuel delivery, reduce the power of engine, can interrupt fuel feeding when serious, engine is quit work, but congealing point important taking out notes, transportation and take care of index beyond doubt.Therefore, the label of commercial Dissel oil with congealing point as the criteria for classifying, if measured the condensing temperature of diesel oil, just known the label of diesel oil.

Because the complicacy and the gold-plating journey of diesel component are very wide, existing conventional method is measured condensing temperature and is difficult to.The boundary that utilize to reduce method of temperature observation congealing point is very indeterminate, and observed deviation is bigger, and the equipment of this conventional determining method is outmoded, operates loaded down with trivial detailsly, and minute is longer.

The cetane rating of diesel oil is the condition name of the expression diesel fuel capability of antidetonance, is one of important indicator of evaluation diesel quality.Cetane rating influences the whole combustion process of diesel motor.In general, the diesel oil that cetane rating is high, its spontaneous ignition temperature is low, and the burning delay period is short, and burning is even, hot merit transformation efficiency height, the stable working of engine and fuel saving; Otherwise, low-cetane diesel oil, the heat that combustion process is sent is inhomogeneous, makes fuel consumption increase.If the cetane rating of diesel oil is low excessively, be difficult for very much oxidation, superoxide growing amount deficiency owing to spray into the fuel of cylinder at first, spontaneous combustion delays, so that the fuel that sprays into gathers too much, spontaneous combustion at the beginning, the growths of these fuel spontaneous combustion simultaneously build-ups of pressure are too fast, substantially exceed the pressure of normal combustion, cause pinking, the impact piston head sends the metal knock, make power descend damage parts.Yet, if diesel cetane-number is too high, then reduced fuel source on the one hand, on the other hand because the delay period of fuel is too short, when forming even combination gas as yet, just do not begin spontaneous combustion, so that the air supply is inadequate, incomplete combustion with air, row's over-emitting black exhaust tail gas, Fuel Consumption increases on the contrary.Thereby, use the just economical rationality of the suitable diesel oil of cetane rating.

The assay method of diesel cetane-number, be to utilize standard cetane pH-value determination pH machine, under standard test conditions, the detonation tendency of sample and the standard fuel (n-hexadecane and alpha-methyl-naphthalene or n-hexadecane and heptamethylnonane) of certain proportioning compared and measure out.Utilizing this method to measure cetane rating needs precision, valuable equipment and the technician of skilled operation, and consumes comparative fuel and oil plant to be measured, is an expensive experiment consuming time.In addition, though this method and mensuration machine through people update and perfect, it measures operating mode and measuring accuracy is improved constantly, because mensuration program and operation are quite complicated, the factor that influences measuring accuracy is various, thereby influences the reliability of actual measured results.

Along with science and technology development, domestic and international many R﹠D institutions are all in the physicochemical characteristics of research with diesel oil, and exploration is measured the new method of cetane rating or cetane rating is associated with other characterisitic parameters, and obtains the corresponding calculated formula.The computing formula that has been widely adopted has:

Cetane rating CV=29.26-0.1779 (t _a/ d ₂₀)+0.0059 (t _a/ d ₂₀) ²

T wherein _aFor the aniline point of oil product (℃)

t _a=0．163677×10 ^-4(t _c+273) ^2．29888×d ^-4．4018 ₂₀

t _cFor the mid-boiling point of oil product (℃)

d ₂₀Be the density (g/cm of oil product 20 ℃ the time ³)

In addition, can also be according to the density and the mid-boiling point calculated cetane index of diesel oil: $\mathrm{CI}=431.29-{1586.88d}_{20}+{730.97d}_{20}^2+{12.392d}_{20}^3+{0.0515d}_{20}^4-{0.554t}_c+{97.803\left({\log t}_c\right)}^2$

T wherein _cFor the mid-boiling point of oil product (℃)

d ₂₀Be the density (g/cm of oil product 20 ℃ the time ³)

Utilize above-mentioned formula to determine the cetane rating of diesel oil, comparatively economical, easy, but for measuring density d ₂₀(g/cm ³) and mid-boiling point t _c, (℃), still must be sent to oil sample to be measured in the laboratory that is equipped with instrumentation and calculate again after the mensuration.

The objective of the invention is to deficiency, a kind of both simple and quick assay method and instrument of measuring diesel number and cetane rating simultaneously is provided, to solve existing method and dress all deficiencies with equipment at prior art.

Fig. 1 is diesel number and cetane test method instrument structural representation; Fig. 2-a is annular concentric electrode capacitance formula sensor construction figure; Fig. 2-b is the annular concentric electrode capacitance formula sensor construction figure with temperature compensation performance; Fig. 3 is diesel number and cetane test method instrument circuit logic diagram; Fig. 4 is can be for a kind of example of the electronic-circuit diagram that adopts; Fig. 5 is the relative density of diesel oil in the time of 20 ℃ and the related function relation of relative dielectric constant; Fig. 6 is the related function relation of the mid-boiling point and the relative dielectric constant of diesel oil; Fig. 7 is the related function relation of the congealing point and the relative dielectric constant of diesel oil; Fig. 8 is the related function relation of the index of refraction and the relative dielectric constant of diesel oil; Fig. 9 is the related function relation of the mean molecular weight and the relative dielectric constant of diesel oil.

The present invention adopts take capacity-type sensing element as sensor, take relative dielectric constant as correlated variables, uses number The reason statistical law, the method for indirect determination diesel number, Cetane number and other physical parameters of petroleum distillate (is called for short The SW method). It is diesel oil and other petroleum distillate physical property and the parameter that a kind of electronic technology combines with statistic law The mensuration new method.

Diesel oil is the liquid mixture with electrical insulation properties, and low, the good fluidity of viscosity has been created advantage for using capacitance type sensor directly to measure its relative dielectric constant.

By theoretical electrical engineering as can be known, the electric capacity between parallel plate electrode is

C=ε ₀·ε _r·S／b

ε wherein ₀=8.85415 * 10 ^-12F/M is the specific inductive capacity of vacuum;

ε _rBe relative dielectric constant (ε in a vacuum _R0=1, ε in air _R0≈ 1)

S is the area of parallel plate electrode;

B is the spacing of parallel plate electrode.The aerial electric capacity of parallel plate electrode capacitance type sensor is

C ₀=ε ₀ε _R0The electric capacity of the same sensor of S/b in diesel oil is

C=ε ₀ε _rSo S/b has

C／C ₀=ε _r／ε _r0≈ε _r

So, the relative dielectric constant ε of diesel oil _RdThe capacitance C of capacitance C when approximating same sensor and being medium when being medium with the air with diesel oil ₀The ratio.To the diesel oil of same quality, this ratio is a constant.So, just can be by measuring the relative dielectric constant ε that the capacitor C value that immerses the capacitive transducer in the oil product to be measured obtains diesel oil to be measured _Rd

The relative dielectric constant of diesel oil distillate between 2.05～2.50, the diesel oil of different qualities, its relative dielectric constant ε _RdAlso inequality, and the relative dielectric constant ε of diesel oil _RdWith its other physical parameters, as density d ₂₀, mid-boiling point t _c, congealing point t _d, index of refraction n _D, mean molecular weight M etc. is relevant.Therefore, as long as find the funtcional relationship between these physical parameters and the relative dielectric constant, just can measure the relevant physical parameter of this diesel oil indirectly by measuring the relative dielectric constant of diesel oil, calculate cetane rating CV and cetane index CI behind aforementioned two formula of substitution.

Key of the present invention is exactly by the statistical study to a large amount of measured datas, has drawn the physical constant (d of diesel oil ₂₀, t _c, t _d, n _D, M) and relative dielectric constant between ε _RdFuntcional relationship: Y=f (ε _Rd)

Relative dielectric constant ε with diesel oil to be measured _RdHandle with above-mentioned funtcional relationship input microprocessor, directly show, read or print the label and the cetane rating of diesel oil to be measured by display with simulating signal or number.

Diesel number of the present invention and cetane test method instrument (Fig. 1) comprising: display 101, keyboard 102, in airtight enclosed shell 100, printed-wiring board (PWB) 103 is housed, battery 104 is equipped with in interior bottom, upper side has mini-printer interface 105 and the sensor 200 that links to each other with Active Interface 106 by shielding line 107.

Sensor 200 employing annular concentric electrode capacitance formula sensors (Fig. 2-a), mainly contain the ring electrode of being processed into by nonmagnetic material 201,2011,202,2021, all have 2～6 pores 203,2031,204,2041 on it, when measuring, be used for discharging the air in the inner chamber.If ring electrode 201,2011 connects positive pole, then ring electrode 202,2021 connects negative pole; Vice versa.The pole plate skeleton 205 that ring electrode 201,2011 is made by screw thread and identical material connects, and the insulation sleeve 206 that 202,2021 of ring electrodes are separated positive and negative pole plate by screw thread and being used to made from nylon (or teflon, bakelite, oil resistant plastics etc.) respectively links to each other with insulated connecting piece 207.In pole plate skeleton 205 top center one external handle that is screwed into as required or standard microwave plug 210 are arranged, and by center pit 208 introducings one lead A, this lead links to each other with ring electrode 202 by the hole 209 that is positioned at pole plate skeleton 205 and insulation sleeve 206 same positions, also links to each other with ring electrode 2021 simultaneously.

In order to eliminate since variation of temperature to the influence of test accuracy, sensor 200 also can adopt annular concentric electrode capacitance formula sensor with temperature compensation performance (Fig. 2-b).This sensor has annular concentric negative pole 211,2111 and the annular central electrode of being processed into by nonmagnetic material (positive pole) 212, all has 2～6 pores 213,2131,214 on it, is used for discharging the air in the inner chamber when measuring.The pole plate skeleton 215 that ring electrode 211,2111 is made by screw thread and identical material connects, 212 of ring electrodes by screw thread with make with nylon (or teflon, bakelite, oil resistant plastics etc.), the insulation sleeve 216 that is used to separate positive and negative pole plate is continuous.In pole plate skeleton 215 top center one external handle that is screwed into as required or standard microwave plug 220 are arranged.Two binding posts 2201,2202 on the standard microwave plug 220 and temperature sensor 217 are connected by lead, and another binding post is also linked to each other with ring electrode 212 by the hole 218 that is positioned at pole plate skeleton 215 and insulation sleeve 216 same positions by lead.

Logic diagram of circuit on the printed-wiring board (PWB) 103 as shown in Figure 3.After immersing capacitive transducer 200 in the oil sample to be measured, signal just is sent to electric capacity/frequency-conversion circuit 132 by sample circuit 131.Electric capacity/frequency-conversion circuit 132 is made up of non-steady-state oscillation circuit, and it can be the LC oscillatory circuit, and its oscillation frequency is $f_{\mathrm{LC}}=\frac{1}{2\mathrm{\π}\sqrt{\mathrm{LC}}}$ Also can be 555 time-base oscillation circuit, its oscillation frequency be $f_{555}=\frac{k}{(R_a+{2R}_b)C}$ Wherein k is a constant

Because C/C ₀=ε _r/ ε _R0=ε _rSo the increase of oil sample relative dielectric constant to be measured will cause the reduction of oscillation frequency, thereby electric capacity increases; Vice versa.Just can obtain the relative dielectric constant of diesel oil to be measured thus.Fig. 4 is can be for a kind of electronic circuit that adopts.

By regretional analysis, obtain the relative density d of diesel oil in the time of 20 ℃ to a large amount of measured datas ₂₀, mid-boiling point t _c, congealing point t _dWith aniline point t _aWith relative dielectric constant ε _RdAnd the relation of the related function between the octane number (referring to Fig. 5, Fig. 6, Fig. 7) is respectively:

And index of refraction n _d, mean molecular weight M and relative dielectric constant ε _RdBetween related function relation (Fig. 8, Fig. 9) be respectively:

So, according to the relative density d of this diesel oil ₂₀With mid-boiling point t _cCan get its aniline point (℃)

t _a=0．163677×10 ^-4(t _c+273) ^2．29888×d ^-4．4018 ₂₀

Relative density d with diesel oil ₂₀And aniline point t _aThe substitution formula:

CV=29.26-0.1779 (t _a/ d ₂₀)+0.0059 (t _a/ d ₂₀) ²Just can obtain the cetane rating of diesel oil to be measured; And with the relative density d of diesel oil ₂₀And mid-boiling point t _cThe substitution formula: $\mathrm{CI}=431.29-{1586.88d}_{20}+{730.97d}_{20}^2+{12.392d}_{20}^3+{0.0515d}_{20}^4-{0.554t}_c+{97.803\left({\log t}_c\right)}^2$ Can obtain the cetane index of diesel oil to be measured again.

To be stored in the microprocessor 133 by the operation program that above-mentioned each related function relation is write.After being sent to microprocessor 133 by the capacitance that obtains after electric capacity/frequency transformation, just can obtain label (congealing point) and the cetane rating and the cetane index of diesel oil, also can obtain the index of refraction n of diesel oil to be measured simultaneously through computing _dWith other important physical parameters such as mean molecular weight M.Then, will calculate the gained result by display interface device 134 and/or 135 outputs of mini-printer interface.In addition, also has keyboard interface 136.As needs, can increase temperature-compensation circuit 137 and computing machine interconnecting interface 138.

Claims (4)

1. one kind is utilized electronic technology and the diesel number that combines with statistic law and cetane test method method and device, it is characterized in that:

1. by immersing the relative dielectric constant ε that capacitance type sensor in the diesel oil to be measured records this diesel oil _Rd

2. with relative density, mid-boiling point, congealing point and correlation parameter-index of refraction and the mean molecular weight and the relative dielectric constant ε of diesel oil _RdBe associated, and obtain related function relation between them, be i.e. d ₂₀=f _d(ε _Rd), t _c=f _Tc(ε _Rd), t _d=f _Td(ε _Rd), n _D=f _n(ε _Rd), M=f _M(ε _Rd);

3. the congealing point temperature value of diesel oil to be measured just is its label, and its cetane rating is then earlier by relative density d ₂₀With mid-boiling point t _cObtain its aniline point $t_a=0.163677\×{10}^{-4}{(t_c+273)}^{2.29888}\×d_{20}^{-4.4018}$ Then according to the formula that has been widely adopted: CV=29.26-0.1779 (t _a/ d ₂₀)+0.0059 (t _a/ d ₂₀) ²Calculate.Relative density d with diesel oil ₂₀And mid-boiling point t _cThe substitution formula: $\mathrm{CI}=431.29-{1586.88d}_{20}+{730.97d}_{20}^2+{12.392d}_{20}^3+{0.0515d}_{20}^4-{0.554t}_c+{97.803\left({\log t}_c\right)}^2$ Also can obtain the cetane index of diesel oil to be measured.

4. with the relative dielectric constant ε of above-mentioned related function relation and gasoline to be measured, the value input microprocessor is handled, and result is shown with simulating signal or number by display.

2. the described capacitance type sensor of claim 1 is mainly made by nonmagnetic metal and the positive and negative pole plate of parallel discharging is formed.Positive and negative pole plate can be plate shaped parallel plate electrode, also can be the annular concentric pole plate or the pole plate of other shapes of parallel discharging at regular intervals.In order to eliminate the influence of temperature, can set up temperature sensor in the capacitance type sensor to gasoline relative dielectric constant to be measured.

3. the described relative dielectric constant measuring method of claim 1 is characterized in that: when capacitance type sensor immerses in the gasoline to be measured, produce a resonance frequency by non-steady-state oscillation circuit.This non-steady-state oscillation circuit can be the LC oscillatory circuit, and its oscillation frequency is $f_{\mathrm{LC}}=\frac{1}{2\mathrm{\π}\sqrt{\mathrm{LC}}}$ Also can be 555 time-base oscillation circuit, its oscillation frequency be $f_{555}=\frac{k}{(R_a+{2R}_b)C}$ So wherein k is a constant, the resonance frequency that is produced by non-steady-state oscillation circuit can convert capacitance C to by above-mentioned relation.By the C/C that concerns between electric capacity between the capacitance type sensor pole plate and the relative dielectric constant ₀=ε _r/ ε _R0≈ ε _rJust obtain the relative dielectric constant of gasoline to be measured.

4. the described related function of claim 1 concerns d ₂₀=f _d(ε _Rd), t _c=f _Tc(ε _Rd), t _d=f _Td(ε _Rd), n _D=f _n(ε _Rd), M=f _M(ε _Rd) be on the basis of a large amount of measured datas, the method for utilization regretional analysis obtains, because of rather than unique.

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