Physical and Combustion Properties of Aviation Fuels

Let us consider some physical and combustion properties of aviation fuels. They are: heating value, volatility, octane number, specific gravity, viscosity, etc.

1. Heating value is the amount of heat obtained from combustion of one mole of fuel. Heating values of fuels are necessary for calculating the fuel requirements for a given engine.

2. Volatility is the ability of a liquid fuel to pass into vapour when heated. As petroleum fuels are made up of a large number of different hydrocarbons having different boiling points, volatility of a fuel is determined by several points: 1) bubble point; 2) ten per cent evaporation point (cold starting characteris­tic); 3) twenty to seventy per cent evaporation (warm-up characte­ristic); 4) dew point.

3. Octane number. All gasolines used in piston engines have a highly undesirable tendency to detonation. Detonation is a very rapid and uncontrolled burning of fuel which is accompanied by an abnormal pressure and temperature rise. This unde­sirable tendency, that is, detonation, is characterized by, octane number. The higher is the octane number, the less is the tendency of a gasoline to detonation.

4. Inhibitors. One of the methods to reduce detonation is to use fuel components high in isoparaffins, olefins and aromatic hydrocarbons. The other method is to add some inhibitor to the fuel. The most common inhibitor is tetraethyllead.

Exercise 9. Pick out Ukrainian equivalents to the following English words and word combinations.

to consider тетраетилсвинець

heating value точка роси

volatility питома вага

octane number швидкий

specific gravity леткість

viscosity розглядати

amount точка появи перших бульбашок

to obtain здатність

mole отримувати

ability точка кипіння

boiling point теплоутворююча здатність

to determine додавати

bubble point супроводжувати

dew point в’язкість

rapid октанове число

to accompany метод

inhibitor присадки

method грам-молекула

to add визначати

tetraethyllead кількість

Exercise 10. Answer the following questions.

1. What are physical and combustion properties of aviation fuels?

2. What is heating value?

3. What are heating values of fuels necessary for?

4. What is volatility?

5. How is volatility of a fuel determined?.

6. What is detonation?

7. What is octane number of a fuel determined by?

8. What is one of the methods to reduce detonation?

9. What is the most common inhibitor?

Exercise 11. Translate the following English terms.

Dew point, warm-up-characteristics, cold starting characteristics, bubble point, heating value, volatility, mole, vapour, boiling point, detonation.

Exercise 12. Complete the following sentences. Translate them.

1. The ability of the liquid fuel to pass into vapour is (леткість).

2. The amount of heat obtained from combustion of one mole of fuel is (теплоутворююча здатність).

3. Volatility of a fuel is determined by several points: (початком кипіння, характеристикою холодного запуску, характеристикою підігрівання, точкою роси).

4. The most cоmmon inhibitor is (тетраетилсвинець).

5. The substance which suppresses the tendency of a fuel to de­tonate is (інгібітор).

Exercise 13. Fill in the blanks with the proper words and word combinations.

(detonation, octane number, heating value, vapour, boiling points,

bubble point, cold starting characteristic, dew point).

1. All gasolines used in piston engines have a highly undesirable tendency to ________.

2. The physical and combustion characteristics of aviation fuels are heating value, volatility, specific gravity, viscosity and ________.

3. ________ is the amount of heat obtained from combustion of one mole of fuel.

4. The fuel will pass into ___________ when heated.

5. Different hydrocarbons of which a petroleum fuel is made have different _________.

6. ___________ is the lowest temperature at which the first bubble of vapour appear.

7. The second point is the temperature at which 10 per cent of the fuel passes to vapour, that is, the ten per cent evaporation point, which is also called ________.

8. The final temperature is _____________because at this temperature the vapours of the fuel start to condense.

Exercise 14. Translate the following sentences into English.

1. Фізико-хімічні властивості авіаційних палив – це теплоутворююча здатність, леткість, питома вага, в’язкість, октанове число.

2. Теплоутворююча здатність – це кількість тепла, отримана при згорянні однієї грам-молекули палива.

3. Леткість – це здатність рідкого палива перетворюватися на пару.

4. Різноманітні вуглеводні, з яких складається нафтове паливо, мають різні точки кипіння.

5. Леткість – одна з найбільш важливих властивостей палива.

6. Всі бензини, що використовуються в поршневих двигунах, мають вкрай небажану тенденцію до детонації.

7. Детонація – дуже швидкий і некерований процес згорання палива, який супроводжується сильним підвищенням тиску і температури.

8. Інгібітор чи присадок – це речовина, яка зменшує тенденцію палива до детонації.

9. Найбільш розповсюджений інгібітор – тетраетилсвинець.

Exercise 15. Translate the text in the written form.