Introduction to Energy Systems: Fuels & Combustion

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Questions and Answers

What is the term used for the minimum amount of air required for the complete combustion of fuel?

Excess air

Stoichiometric air (correct)

Combustion air

Deficiency of air

Which of the following is true regarding excess air in combustion?

It is expressed as a percentage of the stoichiometric amount. (correct)

It is equivalent to a deficiency of air.

It leads to complete combustion without any fuel remaining.

It is always detrimental to combustion efficiency.

How does the adiabatic flame temperature compare to the temperature in practical combustion devices?

It is similar to the practical temperature.

It is always equal to the ambient temperature.

It is usually higher than the practical temperature.

It is considerably lower than the practical temperature. (correct)

What do the terms 'higher heating value' and 'lower heating value' refer to?

Gross calorific value and net calorific value, respectively. Signup and view all the answers

What is indicated by the air-fuel ratio in combustion processes?

The relationship between air and fuel quantities in combustion. Signup and view all the answers

What type of coal is primarily used in the iron and steel industry?

Coking coal Signup and view all the answers

Which of the following accurately describes sour crude oil?

Oil with high sulphur content Signup and view all the answers

What is the main component of natural gas?

CH4 (methane) Signup and view all the answers

Which statement about combustion reactions is true?

All combustible components are burned to completion in complete combustion Signup and view all the answers

What primarily determines the heating value of natural gas?

The chemical composition Signup and view all the answers

What is the air-fuel ratio formula used in combustion processes?

AF = mair / mfuel Signup and view all the answers

How are gases separated during the distillation process in refineries?

Based on their molecular weight Signup and view all the answers

Which type of combustion reaction produces unburned fuel or components?

Incomplete combustion Signup and view all the answers

How is the alkane formula of crude oil hydrocarbons described?

CnH2n+2 Signup and view all the answers

Which of the following describes wet gas in relation to natural gas?

It is a mixture of hydrocarbon gases and impurities Signup and view all the answers

Study Notes

Introduction to Energy Systems - Fuels and Combustion

This course, MECE3260U, is an introduction to energy systems, focusing on fuels and combustion.
The professor is Dr. Ibrahim Dincer, a professor of Mechanical Engineering at OntarioTech University.

Fuels and Combustion - Outline

Historical Perspectives
Impacts of Fossil Fuels
- Coal
- Crude oil
- Natural Gas
Fuels Combustion
Thermodynamic Analysis
Closing Points

Fossil Fuel Era

Fossil fuels are a significant source of energy.
The use of fossil fuels began significantly with the Industrial Revolution.
A graph displays the global primary energy consumption through the years.
Different fuels like coal, oil, and natural gas have seen different adoption rates over time.
The consumption rate of fossil fuels increased rapidly from the 1800s to the 1900s.

Historical Perspective on Fossil Fuels

Fossil fuels formed hundreds of millions of years ago, during the Carboniferous Period (360-286 million years ago).
Fossil fuel usage started with the Industrial Revolution (1760-1840).

Challenges with Fossil Fuels

Global CO2 emissions by world region are shown in a graph.
Emissions have significantly increased since the mid-1800s.
Various regions like China, India, and the United States show high emission rates, particularly in the past few decades

Heating Values

Higher Heating Value (HHV) or Gross Calorific Value (GCV) is measured by bringing combustion products to the pre-combustion temperature.
Lower Heating Value (LHV) or Net Calorific Value (NCV) subtracts the heat of vaporization of water in the products.
The given values in the table of MJ/kg show higher and lower heating values for different fuels.

How Coal Was Formed

Coal formed from dead plants buried underground millions of years ago and subjected to heat and pressure.
Coal varies in quality and heating value (ranks), ranging from lignite to anthracite.
Coal is primarily used for electricity generation and industrial processes, such as iron and steel production.

Crude Oil

Crude oil is a complex mixture of hydrocarbons.
Different fractions of hydrocarbons are separated via distillation at various boiling points in refineries.
A table presents the quantities of different fractions in a barrel of crude oil.

Natural Gas

Natural gas primarily consists of methane (CH4), but also contains other hydrocarbons, gases, and impurities.
Sources include sedimentary rocks (wet or dry, associated/non-associated).
Natural gas composition variation varies by deposit type.

Fuels and Combustion - Introduction

Combustion is a chemical reaction releasing a large amount of energy.
Dry air (79% N2, 21% O2) is commonly used for oxidation.
Combustion reactions are often illustrated depicting reactants and products. The mass balance is not conserved for the number of moles during a combustion reaction.
Fuels are materials that release thermal energy when burned.
Hydrocarbon fuels (mostly hydrogen and carbon) are common.

Theoretical and Actual Combustion Processes

Complete combustion consumes all fuel and components.
Incomplete combustion produces unburned fuel or materials such as carbon (C), hydrogen (H2), carbon monoxide (CO), or hydroxyl (OH).
Stoichiometric air is the minimum needed to burn fuel completely.
Theoretical air involves complete combustion with stoichiometric air.
Methane (CH4) is used as an example to show the complete combustion equation.

Excess and Deficiency of Air

Excess air represents the amount greater than stoichiometric for a reaction.
Deficiency of air is an amount less than stoichiometric air.
These values are often expressed as percentages of the ideal (stoichiometric) amount.

Enthalpy of Formation and Enthalpy of Combustion

The change in enthalpy during a chemical reaction is dependent on the energy state of the system.
Important properties include higher heating values (HHV) and lower heating values (LHV).

Thermodynamic Analysis of Combustion

The equations introduced here are essential for a detailed thermodynamic analysis of a combustion chamber.
The analysis focuses on heat and work transfer, and mass within the system.

Adiabatic Flame Temperature

Temperature of products at maximum in a closed system without heat loss.
Maximum temperatures in combustion devices are typically lower than the adiabatic value due to incomplete combustion, heat loss and dissociation of combustion gases at high temperatures.

Summary of Fuel Combustion Analysis

A summary of different combustion analysis methods (open, closed and adiabatic systems) is provided.
The relationships between energy, enthalpy, entropy, and exergy during different systems of combustion.

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Description

Explore the fundamentals of energy systems, focusing specifically on fuels and combustion in this quiz. Learn about the historical perspectives of fossil fuels, their impacts, and thermodynamic analysis. Perfect for those studying energy engineering or related fields.