FUEL AND COMBUSTION

May 6 • General • 2406 Views • 3 Comments on FUEL AND COMBUSTION

FUEL AND COMBUSTION

RELATIONSHIP BETWEEN KNOCKING AND STRUCTURE OF HYDROCARBON IN FUEL AND COMBUSTION

The relationship between knocking and the structure of the hydrocarbons in gasoline is summarized in the following general rules. :-

• Branched alkanes and cycloalkanes burn more evenly than straight-chain alkanes.
• Short alkanes (C4H10) burn more evenly than long alkanes (C7H16).
• Alkenes burn more evenly than alkanes.
• Aromatic hydrocarbons burn more evenly than cycloalkanes.
• The most commonly used measure of a gasoline’s ability to burn without knocking is its octane number.

OCTANE NUMBER:-

Octane numbers compare a gasoline’s tendency to knock against the tendency of a blend of two hydrocarbons heptane and 2,2,4-trimethylpentane, or isooctane to knock. Heptane (C7H16) is a long, straight-chain alkane, which burns unevenly and produces a great deal of knocking. Highly branched alkanes such as 2,2,4-trimethylpentane are more resistant to knocking. Gasolines that match a blend of 87% isooctane and 13% heptane are given an octane number of 87.
There are three ways of reporting octane numbers.

• Measurements made at high speed and high temperature are reported as motor octane numbers.
• Measurements taken under relatively mild engine conditions are known as research octane numbers.
• The road-index octane numbers reported on gasoline pumps are an average of these two.

Road-index octane numbers for a few pure hydrocarbons are given in the table below.

• ·         Hydrocarbon Octane Numbers

Q.1 what is the relationship between knocking and structure of hydrocarbons?

ANS/

The relationship between knocking and the structure of the hydrocarbons in gasoline is summarized in the following general rules. :-

• Branched alkanes and cycloalkanes burn more evenly than straight-chain alkanes.
• Short alkanes (C₄H₁₀) burn more evenly than long alkanes (C₇H₁₆).
• Alkenes burn more evenly than alkanes.
• Aromatic hydrocarbons burn more evenly than cycloalkanes.
• The most commonly used measure of a gasoline’s ability to burn without knocking is its octane number.

Q.2/what do u mean by OCTANE NUMBER?

ANS/

• Octane numbers compare a gasoline’s tendency to knock against the tendency of a blend of two hydrocarbons heptane and 2,2,4-trimethylpentane, or isooctane to knock. Heptane (C₇H₁₆) is a long, straight-chain alkane, which burns unevenly and produces a great deal of knocking. Highly branched alkanes such as 2,2,4-trimethylpentane are more resistant to knocking. Gasolines that match a blend of 87% isooctane and 13% heptane are given an octane number of 87.
• ·There are three ways of reporting octane numbers.

1. Measurements made at high speed and high temperature are reported as motor octane numbers.
2. Measurements taken under relatively mild engine conditions are known as research octane numbers. The road-index octane numbers reported on gasoline pumps are an average of these two.

Q3/explain hydrocarbon octane numbers?

ANS/  Hydrocarbon Octane Numbers

Q/What is the relationship between Knocking and structure of hydrocarbons?

AN

The relationship between knocking and the structure of the hydrocarbons in gasoline is summarized in the following general rules. :-

• Branched alkanes and cycloalkanes burn more evenly than straight-chain alkanes.
• Short alkanes (C₄H₁₀) burn more evenly than long alkanes (C₇H₁₆).
• Alkenes burn more evenly than alkanes.
• Aromatic hydrocarbons burn more evenly than cycloalkanes.
• The most commonly used measure of a gasoline’s ability to burn without knocking is its octane number.

Q/what is Octane number?

ANS/Octane numbers compare a gasoline’s tendency to knock against the tendency of a blend of two hydrocarbons heptane and 2,2,4-trimethylpentane, or isooctane to knock. Heptane (C₇H₁₆) is a long, straight-chain alkane, which burns unevenly and produces a great deal of knocking. Highly branched alkanes such as 2,2,4-trimethylpentane are more resistant to knocking. Gasolines that match a blend of 87% isooctane and 13% heptane are given an octane number of 87.

Q3/what are ways of Reporting octane number?

ANS/

1. Measurements made at high speed and high temperature are reported as motor octane numbers.
2. Measurements taken under relatively mild engine conditions are known as research octane numbers. The road-index octane numbers reported on gasoline pumps are an average of these two.
3. Road-index octane numbers for a few pure hydrocarbons are given in the table below.

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