Determination of fuel density.
Density of kerosene depending on temperature
A table is given of the density values of liquid kerosene grade T-1 depending on temperature. The density of kerosene is given in the dimension kg/m 3 at various temperatures in the range from 20 to 270°C.
The density of this is determined by the composition and quality of production of its individual batches during oil refining. It increases with increasing content of heavy hydrocarbons in its composition.
The density of kerosene of different brands and different molecular weights may differ by 5...10%. For example, the density of aviation kerosene TS-1 at 20°C is 780 kg/m 3 , TS-2 is 766 kg/m 3 , aviation kerosene T-6 is 841 kg/m 3 , the density of RT fuel is 778 kg/m 3 . The density of T-1 kerosene at a temperature of 20°C is 819 kg/m 3 or 819 g/l, The density of lighting kerosene is 840 kg/m3.
When this fuel is heated, its density decreases due to an increase in volume due to thermal expansion. For example, at a temperature of 270°C, the density of T-1 kerosene becomes equal to 618 kg/m3.
Kerosene is similar to other types of fuel. For example, diesel fuel has a density of about 860 kg/m3, gasoline - from 680 to 800 kg/m3. If we compare the density of kerosene and water, the density of this fuel will be less. When kerosene gets into water, it will form an oily film on its surface.
| t, °С | ρ, kg/m 3 | t, °С | ρ, kg/m 3 | t, °С | ρ, kg/m 3 |
|---|---|---|---|---|---|
| 20 | 819 | 110 | 759 | 200 | 685 |
| 30 | 814 | 120 | 751 | 210 | 676 |
| 40 | 808 | 130 | 744 | 220 | 668 |
| 50 | 801 | 140 | 736 | 230 | 658 |
| 60 | 795 | 150 | 728 | 240 | 649 |
| 70 | 788 | 160 | 720 | 250 | 638 |
| 80 | 781 | 170 | 711 | 260 | 628 |
| 90 | 774 | 180 | 703 | 265 | 623 |
| 100 | 766 | 190 | 694 | 270 | 618 |
Specific heat capacity of kerosene at different temperatures
The table shows the specific heat capacity of kerosene at various temperatures. The heat capacity of kerosene is indicated in the temperature range from 20...270°C. The value of the specific (mass) heat capacity of kerosene is determined by its composition, that is, the content of aromatic and paraffin hydrocarbons. The less paraffins and olefins there are in kerosene, the lower its heat capacity.
The specific heat capacity of kerosene depends on temperature - it increases when the fuel is heated. The dependence of heat capacity on temperature is nonlinear. At room temperature, its specific heat capacity is 2000 J/(kg K). At high temperatures, the value of this thermophysical property of kerosene can reach 3300 J/(kg K).
In addition, the heat capacity of kerosene also depends on pressure. As pressure increases, it decreases; at high temperatures, the effect of pressure increases. It should be noted that the dependence of the heat capacity of kerosene on pressure is not linear.
| t, °С | C p , J/(kg K) | t, °С | C p , J/(kg K) | t, °С | C p , J/(kg K) |
|---|---|---|---|---|---|
| 20 | 2000 | 110 | 2430 | 200 | 2890 |
| 30 | 2040 | 120 | 2480 | 210 | 2940 |
| 40 | 2090 | 130 | 2530 | 220 | 3000 |
| 50 | 2140 | 140 | 2580 | 230 | 3050 |
| 60 | 2180 | 150 | 2630 | 240 | 3110 |
| 70 | 2230 | 160 | 2680 | 250 | 3160 |
| 80 | 2280 | 170 | 2730 | 260 | 3210 |
| 90 | 2330 | 180 | 2790 | 265 | 3235 |
| 100 | 2380 | 190 | 2840 | 270 | 3260 |
Kerosene viscosity depending on temperature
A table of dynamic values is given. μ and kinematic ν kerosene viscosity at positive and negative temperatures in the range from -50 to 300°C. The viscosity of kerosene is determined by the number and size of associates of hydrocarbon molecules in its composition. The scale of such molecular bonds directly depends on the temperature of the fuel. At low temperatures they are quite numerous and large in size, which makes kerosene noticeably viscous under these conditions.
At room temperature, the dynamic viscosity of kerosene is 0.00149 Pa s. The kinematic viscosity of kerosene at a temperature of 20°C is 1.819·10 -6 m 2 /s. As the temperature of this fuel increases, its viscosity decreases. The kinematic viscosity coefficient has a lower rate of decrease than the dynamic one, since the density of kerosene also changes with temperature. For example, when kerosene is heated from 20 to 200 degrees, its dynamic viscosity decreases by 5.7 times, and kinematic viscosity by 4.8.
| t, °С | μ·10 3 , Pa·s | ν·10 6, m 2 /s | t, °С | μ·10 3 , Pa·s | ν·10 6, m 2 /s |
|---|---|---|---|---|---|
| -50 | 11,5 | 14,14 | 40 | 1,08 | 1,337 |
| -45 | 9,04 | — | 60 | 0,832 | 1,047 |
| -40 | 7,26 | 8,59 | 80 | 0,664 | 0,85 |
| -35 | 5,96 | — | 100 | 0,545 | 0,711 |
| -30 | 4,98 | 5,75 | 120 | 0,457 | 0,61 |
| -25 | 4,22 | — | 140 | 0,39 | 0,53 |
| -20 | 3,62 | 4,131 | 160 | 0,338 | 0,469 |
| -15 | 3,14 | — | 180 | 0,296 | 0,421 |
| -10 | 2,75 | 3,12 | 200 | 0,262 | 0,382 |
| -5 | 2,42 | — | 220 | 0,234 | 0,35 |
| 0 | 2,15 | 2,61 | 240 | 0,211 | 0,325 |
| 5 | 1,92 | — | 260 | 0,191 | 0,304 |
| 10 | 1,73 | — | 280 | 0,174 | — |
| 20 | 1,49 | 1,819 | 300 | 0,159 | — |
Note: the values of kinematic viscosity of kerosene in the table were obtained by calculation using the value of dynamic viscosity and density.
Any liquid has its own unique properties and characteristics. In physics, it is customary to consider a number of phenomena that are associated with these specific characteristics.
Liquids are usually divided into two main categories:
- drip or low compressible;
- gaseous or compressible.
Figure 2. Calculation of liquid density. Author24 - online exchange of student works
These classes of liquids have fundamental differences between themselves. Thus, droplet liquids differ significantly from gaseous ones. They have a certain volume. Its value will not change under the influence of any external forces. In the gaseous state, liquids can occupy all the volume they have. Also, a similar class of liquid can significantly change its own volume if it is influenced by certain external forces.
Liquids of any type have three properties that they cannot part with:
- density;
- viscosity;
- surface tension force.
These properties can influence numerous laws of their movement, so they are of primary importance in the process of studying and applying knowledge in practice.
Concept of liquid density
The mass contained in a unit volume is called the density of the liquid. If you progressively increase the pressure unit, the volume of water will tend to decrease from its original value. The difference in values is approximately 1 in 20,000. The volumetric compression ratio for other droplet liquids will have the same order of numbers. As a rule, in practice it is found that no significant changes in pressure occur, so it is customary not to use the compressibility of water in practice when calculating specific gravity and density as a function of pressure.
Figure 3. Densities of various liquids. Author24 - online exchange of student works
To calculate liquid density, the concept of temperature expansion for droplet liquids is introduced. It is characterized by the coefficient of thermal expansion, which expresses the increase in liquid volume with an increase in temperature by 10 degrees Celsius.
Thus, a density indicator for a particular liquid is formed. It is usually taken into account at different atmospheric pressure and temperature indicators. Above is a table that shows the densities of the main types of liquids.
Density of water
The most common and familiar liquid to humans is water. Let's consider the main characteristics of the density and viscosity of this substance. The density of water under natural conditions will be 1000 kg/m3. This indicator is used for distilled water. For sea water, the density value is slightly higher - 1030 kg/m3. This value is not finite and is closely related to temperature. Ideal indicators can be recorded at a temperature of about 4 degrees Celsius. If you make calculations over boiling water at a temperature of 100 degrees, then the density will decrease quite significantly and will be approximately 958 kg/m3. It has been established that usually in the process of heating any liquids, their density decreases.
The density of water is also quite close to a number of common foods. It can be compared to wine, vinegar solution, skim milk, cream, sour cream. Some types of products have higher densities. However, there are many food and beverage products that can be significantly inferior to classic water. Among them are usually alcohols, as well as petroleum products, including fuel oil, kerosene and gasoline.
If it is necessary to calculate the density of some gases, then the equations of state of ideal gases are used. This is necessary in cases where the behavior of real gases differs significantly from the behavior of ideal gases and the liquefaction process does not occur.
The volume of a gas usually depends on pressure and temperature. Pressure differences that cause significant changes in gas density occur when moving at high speeds. Typically, incompressible gas manifests itself at speeds that exceed one hundred meters per second. The ratio of the fluid speed to the speed of sound is calculated. This makes it possible to correlate many indicators when confirming the density of a particular substance.
Viscosity of liquids
Another property of any liquid is viscosity. This is a state of fluid that is capable of resisting shear or other external forces. It is known that real liquids have similar properties. It is defined as internal friction during the relative movement of liquid particles located nearby.
There are not only easily mobile liquids, but also more viscous substances. The first group usually includes air and water. In heavy oils, resistance occurs at a different level. Viscosity can be characterized by the degree of fluidity of a liquid. This process is also called the mobility of its particles, and it depends on the density of the substance. The viscosity of liquids in laboratory conditions is determined by viscometers. If the viscosity of a liquid largely depends only on the applied temperature, then it is customary to distinguish between several basic parameters of substances. As the temperature increases, the viscosity of the droplet liquid tends to decrease. The viscosity of a gaseous liquid under similar conditions only increases.
The force of internal friction in liquids arises when the gradient speed is proportional to the area of the layers that carry out the friction. In this case, friction in liquids is usually distinguished from the process of friction in other solid bodies. In solids, the friction force will depend on the normal pressure, and not on the area of the rubbing surfaces.
Anomalous and ideal liquids
There are two types of liquids based on their internal characteristics:
- abnormal fluids;
- ideal liquids.
Definition 1
Anomalous liquids are those liquids that do not obey Newton's law of viscosity. Such liquids are capable of starting to move after the moment of shear stress when passing the minimum threshold. This process is also called initial shear stress. These fluids cannot move under small stresses and experience elastic deformation.
Ideal liquids include an imaginary liquid that is not subject to any compression or deformation, that is, it lacks the property of viscosity. To calculate it, it is necessary to introduce certain correction factors.
A table is provided of the density of liquids at various temperatures and atmospheric pressure for the most common liquids. The density values in the table correspond to the indicated temperatures; data interpolation is allowed.
Many substances are capable of being in a liquid state. Liquids are substances of various origins and compositions that have fluidity; they are capable of changing their shape under the influence of certain forces. The density of a liquid is the ratio of the mass of a liquid to the volume it occupies.
Let's look at examples of the density of some liquids. The first substance that comes to mind when you hear the word “liquid” is water. And this is not at all accidental, because water is the most common substance on the planet, and therefore it can be taken as an ideal.
Equal to 1000 kg/m 3 for distilled and 1030 kg/m 3 for sea water. Since this value is closely related to temperature, it is worth noting that this “ideal” value was obtained at +3.7°C. The density of boiling water will be slightly less - it is equal to 958.4 kg/m 3 at 100°C. When liquids are heated, their density usually decreases.
The density of water is similar in value to various food products. These are products such as: vinegar solution, wine, 20% cream and 30% sour cream. Some products turn out to be denser, for example, egg yolk - its density is 1042 kg/m3. The following are denser than water: pineapple juice - 1084 kg/m3, grape juice - up to 1361 kg/m3, orange juice - 1043 kg/m3, Coca-Cola and beer - 1030 kg/m3.
Many substances are less dense than water. For example, alcohols are much lighter than water. So the density is 789 kg/m3, butyl - 810 kg/m3, methyl - 793 kg/m3 (at 20°C). Certain types of fuel and oil have even lower density values: oil - 730-940 kg/m3, gasoline - 680-800 kg/m3. The density of kerosene is about 800 kg/m3, - 879 kg/m3, fuel oil - up to 990 kg/m3.
| Liquid | Temperature, °C |
Liquid density, kg/m 3 |
|---|---|---|
| Aniline | 0…20…40…60…80…100…140…180 | 1037…1023…1007…990…972…952…914…878 |
| (GOST 159-52) | -60…-40…0…20…40…80…120 | 1143…1129…1102…1089…1076…1048…1011 |
| Acetone C3H6O | 0…20 | 813…791 |
| Chicken egg white | 20 | 1042 |
| 20 | 680-800 | |
| 7…20…40…60 | 910…879…858…836 | |
| Bromine | 20 | 3120 |
| Water | 0…4…20…60…100…150…200…250…370 | 999,9…1000…998,2…983,2…958,4…917…863…799…450,5 |
| Sea water | 20 | 1010-1050 |
| Water is heavy | 10…20…50…100…150…200…250 | 1106…1105…1096…1063…1017…957…881 |
| Vodka | 0…20…40…60…80 | 949…935…920…903…888 |
| Fortified wine | 20 | 1025 |
| Dry wine | 20 | 993 |
| Gas oil | 20…60…100…160…200…260…300 | 848…826…801…761…733…688…656 |
| 20…60…100…160…200…240 | 1260…1239…1207…1143…1090…1025 | |
| GTF (coolant) | 27…127…227…327 | 980…880…800…750 |
| Dauterm | 20…50…100…150…200 | 1060…1036…995…953…912 |
| Chicken egg yolk | 20 | 1029 |
| Carborane | 27 | 1000 |
| 20 | 802-840 | |
| Nitric acid HNO 3 (100%) | -10…0…10…20…30…40…50 | 1567…1549…1531…1513…1495…1477…1459 |
| Palmitic acid C 16 H 32 O 2 (conc.) | 62 | 853 |
| Sulfuric acid H 2 SO 4 (conc.) | 20 | 1830 |
| Hydrochloric acid HCl (20%) | 20 | 1100 |
| Acetic acid CH 3 COOH (conc.) | 20 | 1049 |
| Cognac | 20 | 952 |
| Creosote | 15 | 1040-1100 |
| 37 | 1050-1062 | |
| Xylene C 8 H 10 | 20 | 880 |
| Copper sulfate (10%) | 20 | 1107 |
| Copper sulfate (20%) | 20 | 1230 |
| Cherry liqueur | 20 | 1105 |
| Fuel oil | 20 | 890-990 |
| Peanut butter | 15 | 911-926 |
| Machine oil | 20 | 890-920 |
| Motor oil T | 20 | 917 |
| Olive oil | 15 | 914-919 |
| (refined) | -20…20…60…100…150 | 947…926…898…871…836 |
| Honey (dehydrated) | 20 | 1621 |
| Methyl acetate CH 3 COOCH 3 | 25 | 927 |
| 20 | 1030 | |
| Condensed milk with sugar | 20 | 1290-1310 |
| Naphthalene | 230…250…270…300…320 | 865…850…835…812…794 |
| Oil | 20 | 730-940 |
| Drying oil | 20 | 930-950 |
| Tomato paste | 20 | 1110 |
| Boiled molasses | 20 | 1460 |
| Starch syrup | 20 | 1433 |
| A PUB | 20…80…120…200…260…340…400 | 990…961…939…883…837…769…710 |
| Beer | 20 | 1008-1030 |
| PMS-100 | 20…60…80…100…120…160…180…200 | 967…934…917…901…884…850…834…817 |
| PES-5 | 20…60…80…100…120…160…180…200 | 998…971…957…943…929…902…888…874 |
| Applesauce | 0 | 1056 |
| (10%) | 20 | 1071 |
| A solution of table salt in water (20%) | 20 | 1148 |
| Sugar solution in water (saturated) | 0…20…40…60…80…100 | 1314…1333…1353…1378…1405…1436 |
| Mercury | 0…20…100…200…300…400 | 13596…13546…13350…13310…12880…12700 |
| Carbon disulfide | 0 | 1293 |
| Silicone (diethylpolysiloxane) | 0…20…60…100…160…200…260…300 | 971…956…928…900…856…825…779…744 |
| Apple syrup | 20 | 1613 |
| Turpentine | 20 | 870 |
| (fat content 30-83%) | 20 | 939-1000 |
| Resin | 80 | 1200 |
| Coal tar | 20 | 1050-1250 |
| Orange juice | 15 | 1043 |
| Grape juice | 20 | 1056-1361 |
| Grapefruit juice | 15 | 1062 |
| Tomato juice | 20 | 1030-1141 |
| Apple juice | 20 | 1030-1312 |
| Amyl alcohol | 20 | 814 |
| Butyl alcohol | 20 | 810 |
| Isobutyl alcohol | 20 | 801 |
| Isopropyl alcohol | 20 | 785 |
| Methyl alcohol | 20 | 793 |
| Propyl alcohol | 20 | 804 |
| Ethyl alcohol C 2 H 5 OH | 0…20…40…80…100…150…200 | 806…789…772…735…716…649…557 |
| Sodium-potassium alloy (25%Na) | 20…100…200…300…500…700 | 872…852…828…803…753…704 |
| Lead-bismuth alloy (45%Pb) | 130…200…300…400…500..600…700 | 10570…10490…10360…10240…10120..10000…9880 |
| liquid | 20 | 1350-1530 |
| Whey | 20 | 1027 |
| Tetracresyloxysilane (CH 3 C 6 H 4 O) 4 Si | 10…20…60…100…160…200…260…300…350 | 1135…1128…1097…1064…1019…987…936…902…858 |
| Tetrachlorobiphenyl C 12 H 6 Cl 4 (arochlor) | 30…60…150…250…300 | 1440…1410…1320…1220…1170 |
| 0…20…50…80…100…140 | 886…867…839…810…790…744 | |
| Diesel fuel | 20…40…60…80…100 | 879…865…852…838…825 |
| Carburetor fuel | 20 | 768 |
| Motor fuel | 20 | 911 |
| RT fuel | 836…821…792…778…764…749…720…692…677…648 | |
| Fuel T-1 | -60…-40…0…20…40…60…100…140…160…200 | 867…853…824…819…808…795…766…736…720…685 |
| T-2 fuel | -60…-40…0…20…40…60…100…140…160…200 | 824…810…781…766…752…745…709…680…665…637 |
| T-6 fuel | -60…-40…0…20…40…60…100…140…160…200 | 898…883…855…841…827…813…784…756…742…713 |
| T-8 fuel | -60…-40…0…20…40…60…100…140…160…200 | 847…833…804…789…775…761…732…703…689…660 |
| Fuel TS-1 | -60…-40…0…20…40…60…100…140…160…200 | 837…823…794…780…765…751…722…693…879…650 |
| Carbon tetrachloride (CTC) | 20 | 1595 |
| Urothopine C 6 H 12 N 2 | 27 | 1330 |
| Fluorobenzene | 20 | 1024 |
| Chlorobenzene | 20 | 1066 |
| Ethyl acetate | 20 | 901 |
| Ethyl bromide | 20 | 1430 |
| Ethyl iodide | 20 | 1933 |
| Ethyl chloride | 0 | 921 |
| Ether | 0…20 | 736…720 |
| Harpius Ether | 27 | 1100 |
Low density indicators are characterized by such liquids as: turpentine 870 kg/m 3,
One of the three aggregate states of existence of substances is liquid. Liquid particles are located very compactly, which determines their high density (the densities of some liquids are given in Table 1) and low compressibility compared to gases. The structure and internal structure of liquids are characterized by an ordered arrangement of particles. Due to the relatively high mobility of liquid particles, their ordering is limited to small islands (aggregates or clusters), the latter being randomly oriented relative to each other and part of the space between them remains unfilled with matter. These formations are unstable, the connections in them are constantly destroyed and re-emerged. In this case, an exchange of particles occurs between neighboring clusters. Thus, from a structural point of view, a liquid is characterized by the presence of a labile (mobile) equilibrium, due to the relative freedom of movement of particles. The formation of labile aggregates in liquids is observed even at temperatures much higher than the crystallization temperature. With decreasing temperature, the stability of such aggregates increases and near the crystallization temperature, liquids have a quasicrystalline structure, i.e. the number of aggregates increases, they become larger in size and begin to be oriented relative to each other in a certain way.
Table 1. Densities of some liquids.
Liquids are isotropic, i.e. their physical properties are the same in different directions. With any effort, no matter how small, liquids easily change their shape, which manifests itself in fluidity. Naturally, fluidity (or its inverse value - viscosity) for different liquids varies within wide limits. There are liquids that have a very high viscosity (for example, some bitumens), as a result of which, when a sudden load is applied - an impact - they collapse like solids. At the same time, a gradual and continuous increase in load makes it possible to detect fluidity in them.
Examples of problem solving
EXAMPLE 1
| Exercise | Calculate the volume of water and the mass of sodium chloride NaCl that will be required to prepare 250 ml of a 0.7 M solution. Take the density of the solution equal to 1 g/cm3. What is the mass fraction of sodium chloride in this solution? |
| Solution | A molar concentration of a solution equal to 0.7 M indicates that 1000 ml of solution contains 0.7 mol of salt. Then, you can find out the amount of salt substance in 250 ml of this solution: n(NaCl) = V solution (NaCl) × C M (NaCl); n(NaCl) = 250 × 0.7 / 1000 = 0.175 mol. Let's find the mass of 0.175 mol sodium chloride: M(NaCl) = Ar(Na) + Ar(Cl) = 23 + 35.5 = 58.5 g/mol. m(NaCl) = n(NaCl) × M(NaCl); m(NaCl) = 0.175 × 58.5 = 10.2375 g. Let's calculate the mass of water required to obtain 250 ml of 0.7 M sodium chloride solution: r = m solution / V; m solution = V ×r = 250 × 1 = 250 g. m(H 2 O) = 250 - 10.2375 = 239.7625 g. |
| Answer | The mass of water is 239.7625 g, the volume is the same value, since the density of water is 1 g/cm 3. |
EXAMPLE 2
| Exercise | Calculate the volume of water and mass of potassium nitrate KNO 3 that will be required to prepare 150 ml of a 0.5 M solution. Take the density of the solution equal to 1 g/cm3. What is the mass fraction of potassium nitrate in such a solution? |
| Solution | A molar concentration of a solution equal to 0.5 M indicates that 1000 ml of solution contains 0.7 mol of salt. Then, you can find out the amount of salt in 150 ml of this solution: n(KNO 3) = V solution (KNO 3) × C M (KNO 3); n(KNO 3) = 150 × 0.5 / 1000 = 0.075 mol. Let's find the mass of 0.075 mol of potassium nitrate: M(KNO 3) = Ar(K) + Ar(N) + 3×Ar(O) = 39 + 14 + 3×16 = 53 + 48 = 154 g/mol. m(KNO 3) = n(KNO 3) × M(KNO 3); m(KNO 3) = 0.075 × 154 = 11.55 g. Let's calculate the mass of water required to obtain 150 ml of a 0.5 M solution of potassium nitrate: r = m solution / V; m solution = V ×r = 150 × 1 = 150 g. m(H 2 O) = m solution - m(NaCl); m(H 2 O) = 150 - 11.55 = 138.45 g. |
| Answer | The mass of water is 138.45 g, the volume is the same value, since the density of water is 1 g/cm3. |
Goals of work:
give students an idea of the methodology for determining the density of petroleum products;
teach students to take into account the density value when accounting for the consumption of fuel and lubricants.
Under fuel densityρ understand its mass per unit volume. The density dimension in SI units is expressed in kg/m3. The density of petroleum products depends on temperature, i.e., as it increases, the density decreases, and as it decreases, it increases. Density can be measured at any temperature, but the measurement result necessarily results in a temperature of +20 °C, which is taken as the standard when assessing the density of fuels and oils.
Reduction of the measured density to density at a standard temperature of +20 °C is carried out according to the formula
ρ 20 = ρ t + γ(t + 20),
Where ρ - fuel density at test temperature, kg/m 3 ; γ - average temperature correction, kg/m 3 -deg (Table 2); t- temperature at which the fuel density was measured, °C.
The values of corrections for density are given in table. 2.
table 2
Average temperature corrections for the density of petroleum products
|
Petroleum products |
Options |
|
|
Measured density of petroleum products ρ t kg/m 3 |
Temperature correction per 1 °C γ , kg/m 3 |
|
|
Diesel fuel | ||
Reporting on studied petroleum products
Accounting for petroleum products at oil depots, fuel and lubricant warehouses for motor vehicles, mechanization bases and gas stations, as well as wholesale purchase and transportation of fuel and lubricants are carried out in mass units, i.e., income is carried out in weight units - kilograms and tons (kg, t), and consumption is taken into account in volumetric units - liters (l).
Consequently, the accounting and reporting system, as well as calculations when drawing up supply requests, must provide for the transfer of quantities from mass units to volume units and vice versa. In addition, control of the presence of fuel residues in the tanks of gas stations (gas stations), their retail sale and dispensing when refueling vehicle tanks, their consumption rates are also established and produced in volumetric units, i.e. in liters (l).
Because of this, it is necessary to convert from mass units to volume units and vice versa, for which you need to know the density of the received and supplied petroleum products.
Recalculation is carried out as follows: amount of gasoline in mass units, kg G t = V t ρ t,
Where V t- amount of gasoline in volumetric units, l; ρ t- density of gasoline at the same temperature, kg/l.
With reverse calculation and the same notation V t = G t / ρ t.
Thus, absolute density of a substance is the amount of mass contained in a unit volume. It has the dimension kg/m 3 in the SI system.
Measuring density using oil densimeters
At warehouses and gas stations, the density of petroleum products is measured using oil densimeter(hydrometer), which is a hollow glass float with ballast at the bottom and a thin glass tube on top, which contains a density scale. The measuring kit includes densimeters with different density scale limits, allowing you to practically determine the density of all types of fuel and oils (Fig. 3-4).
Densimeters are calibrated in g/cm3, therefore, to express the density of the product in the SI system, it is necessary to recalculate the resulting measurement result by multiplying by 1000.
Rice. 4. Determination of gasoline density A - aerometer: 1 - thermometer scale; 2 - density scale (p, g/cm2); b - oil densimeter: 1 - oil densimeter
Rice. 3. Device for determining the density of petroleum products: 1 - glass cylinder; 2 - oil densimeter; 3 - tested oil product; 4 - thermometer
Devices and materials - oil densimeter, glass cylinder
The order of work.
1) pour the test fuel into a clean glass cylinder with a capacity of 250 ml and a diameter of 50 ml;
2) allow the fuel to settle until air bubbles are released so that it takes on the temperature of the surrounding air;
3) select an oil densimeter with the appropriate scale division, kg/m 3, and measurement limit:
for gasoline - 690-750; for diesel fuels - 820-860;
for kerosene - 780-820; for oils - 830-910;
4) take a clean and dry oil densimeter by the upper part and slowly immerse it in the test product so that it does not touch the cylinder walls;
5) after the oil densimeter stops oscillating, take readings on the density scale along the upper edge of the meniscus (in this case, the observer’s eye should be at the level of the liquid meniscus);
6) take a reading of the test temperature t using a thermometer soldered into the oil densimeter. The reading on the densimeter scale gives the fuel density ρ t at test temperature t.
7) bring the measured density to the standard value p 20, i.e. to density at a temperature of +20 ° C, taking into account the temperature correction according to table. 3.
The values of corrections for density are given in table. 3. The density of gasoline is not standardized by the standard, however, along with other physical and chemical indicators, it characterizes the quality of petroleum products;
Table 3
Table of full temperature corrections for the density of petroleum products
|
Measured |
Correction for |
Measured |
Correction for |
|
density, kg/m 3 |
1°C, kg/m 3 |
density, kg/m 3 |
1°C, kg/m 3 |
8) when determining the density of petroleum products with a densimeter that have a viscosity at 50 °C of more than 200 cSt, the immersion of the densimeter occurs very slowly, so such petroleum products are mixed with an equal volume of kerosene, the density of which is measured in advance. Stir the oil products until completely homogeneous and determine the density of the mixture in the same way as indicated earlier.
The density of a viscous petroleum product is calculated using the formula:
where p I is the density of the mixture; p II - kerosene density.
If the density of kerosene and the mixture was determined at different temperatures, then the densities are recalculated, brought to the same temperature values, and only after that the values p I and p II are substituted into the formula.
