Types of Fuel

Substances that generate heat and light with the burning are known as fuel. The matter used for burning is known as fuels.  There are three types of fuels-coal, oil, and natural gas. According to the physical condition of the fuels can be classified into three categories. These three categories are- solid, liquids, and gases. Most of the engines run on the liquid and gases. Some of the solid fuels engines are reported in history.

1. Solid fuel

A fuel, which is in a physical solid-state at atmospheric temperature, is called solid fuel. In old days, vehicles with external combustion used solid fuels. Examples of solid fuels are coal, charcoal, wood, etc.

Burning wood-Solid Fuel

2. Liquid fuel

A fuel, which is in a physical liquid state at room temperature, is called liquid fuel. Liquid fuel obtained from the crude oil. Most of the IC engines run on liquid fuel. The most additive used in a pre-mixed condition with the diesel. Handling with liquid fuels is quite easy to compare with gas fuels. There are two types of Liquid fuels. One who gets vaporized easily E.g. Petrol, alcohol, etc. This type of fuel used in the spark ignition based engine. The second types of liquid fuels are those who do not vaporize easily ex. Diesel, kerosene, etc. they are also known as the hydrocarbon because of the hydrogen and carbon atom.

Liquid Fuel

3. Gases fuel

A fuel, which exists in the gas state at atmospheric temperature, is called gas fuel. Many fuel gases are known as hydrocarbon (methane, propane). These fuels are best suited for the IC engine. Gases fuel has significant heat and light energy.  E.g. hydrogen, Coal gas, CNG, etc.

CNG Cylinder-Gas fuel

5 Advanced Engine Technology

There have been many improvements over the decades to increase the performance and decrease the emissions of the engine. Some of the technology has been listed below. 

1. Hybrid Vehicle

Hybrid vehicles are also known as the 'Hybrid Electric Vehicle' are popular for their higher efficiency, lower fuel cost and lower carbon dioxides. It uses both fuel and electricity. An internal combustion engine, electric motor, and batteries are combined to provide energy to the vehicle. They work in a harmony to make an efficient system. The internal combustion engine has two works. The first work is to provide the power to the motor and the second is to charge the battery. Electric motors are located in different places in the vehicle. They are connected to the transmission and driven wheels. Batteries are used to store energy. In hybrid vehicle battery charging from home or grid is not required because of the charging management system in the vehicle. All these different systems work together through the computer or series of computers. The control system decided from where the power is coming and going. Control system analysis a thousand times per second of the state of the charging system and figure out what the car has to do.

Main Parts of the Hybrid vehicle 

2. Direct Injection (DI)

Direct injection (DI) is the technology in which fuel is directly sprayed inside the combustion chamber of the engine. In port injection technology the fuel comes at the backside of the valve and then goes to the combustion chamber. DI technology combines with the electronic and does the great things which are not possible with the mechanical injection system. DI precisely spray the fuel and air inside the individual cylinder of the engine with the help of electronics. The quantity of the fuel is also measured and control by the electronic fuel injection. This new technology provides high torque, better fuel efficiency, and emission regulations. however, it increases the carbon deposits on the valves. The injector of the direct injection is expansive to the port injection because of the high temperature, high pressure, and high flow rate required with this injector.

3. Turbocharging

The history of the turbocharger is old. Earlier it was used a lot in sports cars. In today's time turbocharger is used to increase engine efficiency, reduce fuel consumption, and lower emissions. A turbocharger is a forced induction device that improves the performance and emissions of the engine. It is the process of forcing compressed air into the intake for combustion. The turbocharger is designed to rotate over 1 lac RPM. With a turbocharger introduced the exhaust gas from combustion turns the turbine wheel. This turbine wheel rotates the compressor wheel which is attached by a connecting shaft. This compressor sucks the more air and sends it to the combustion chamber. A turbocharger provides more fresh air to expand on combustion and produces more power. Fresh air makes human's lungs healthy in the same way highly compressed, highly hot and fresh air make the engine more powerful.

The 'supercharger ' is driven mechanically (belt, gear, etc.) by the engine. While there is no mechanical load on the engine through the turbocharger because the turbine is driven by exhaust gases.  

Working of turbocharger 

4. Cylinder Deactivation

Cylinder deactivation technology is also known as 'displacement on-demand' and fuel management system. This technology is used on big engines like 6 cylinders or 8 cylinders. In light-load driving situations such as on the highway. The cylinder deactivation engine shuts down 2 or 4 cylinders to save fuel. To do this engine control units continuously analyze the following parameters such as torque, engine speed, vehicle speed, gear engaged, etc. and send feedback to the engine valve for taking action. Electronic throttle is a part of the solution it manages change over RPM. Cylinder deactivation technology shuts off one, two, or four-cylinder when cruising to reduce fuel consumption and emissions. For example, if you are driving a V8 engine on the highway (low load condition). There is not much power and torque required on this cruising therefore engine automatically deactivates the 2 or 4 cylinders to save fuel and come back to activate condition seamlessly. It is quite clever technology.

5. Electric Vehicle (EV)

Electric vehicles (EV) are becoming popular nowadays. All-electric vehicles have an induction motor and inverter instead of an internal combustion engine. The vehicle uses a large traction battery pack to power the electric motor and must be plugged into charging stations. An electric vehicle does not contain the typical liquid fuel components such as fuel tanks, fuel pumps, etc. An electric vehicle does not emit any harmful emissions. But the production of electricity produces harmful gases to the atmosphere. However, EV directly produces zero emissions. The big drawback with EV is the battery and recharging stations. All over the world governments are trying to create proper infrastructure for EV in their country.  

Properties of diesel engine fuel

There are some desirable properties of the Compression Ignition engine for safety, convenience, and handling.

1.  Viscosity

Viscosity can be defined as the resistance to the flow of liquid due to internal friction among the various layer of liquid. The engine performance is affected by this important property of the fuel. When the fuel viscosity is low then the injection pump wear and power loss take place. If the viscosity is high then also filter blockage and excessive pump resistance take place.

2.  Cloud and Pourpoint

Cloud point is referred to the temperature at which the formation of wax cloud in the fuel. On the other hand pour point also refers to the temperature at which fuel losses its flow characteristics. The value of the pourpoint is always smaller than the cloud point. The value of the cloud point should be smaller so that less difficulty takes place in the winter season.

3.  Cetane number

We use the high cetane number fuel in the compression ignition engine to avoid knocking (occurs due to the delay period) in the engine. Cetane number is the manifestation of the burning characteristics of the diesel fuel. If the value of the cetane number is higher than the ignition characteristics of the fuel is good.

4. Engine deposits

It is the major problem in the engine. Carbon atoms are deposited on all parts of the engine. These deposits grow with high viscosity and low volatility. The sulfur molecules in the diesel fuel increase the corrosion and engine deposits. 

5. Volatility

Volatility influences the burning characteristics of the fuel. The fuel should be significantly volatile under the working range of temperature to produce high-quality blending and burning. The volatility quality of the diesel fuel influences the emission and smoke density of the exhaust. Highly volatile fuel helps in easy and quick starting of the engine.

6.  Flash and Fire point

The fire point is the smallest temperature at which fuel vapor will burn continuously for 5 seconds. Whereas flashpoint is also the lower temperature of the fuel but at this point, fuel gives off its vapor and ignites just for a moment. The flash and fire points indicate that we can handle the fuel below these points without any accident.

Emission Gases from Compression Ignition(CI) engine

Automobiles are an integral part of society. Human depended too much on it. As the population of India is increasing the number of automobiles also increases on the road. The more the vehicle on the road more would be the bad environment due to the dangerous gases like NO_x, CO₂, CO, HC, smoke, and PM.

Road Traffic 

The complete combustion of diesel in the combustion chamber emits only CO₂ and H₂O. But due to the some of the reasons (air-fuel ratio, fuel turbulence, combustion temperature, ignition timing, etc.) ideal combustion did not take place and emits dangerous gases like , CO₂, CO, HC, smoke, and PM (particulate matter). These gases are listed below.

Harmful Emission from Automobiles

1. Oxides of Nitrogen (NOx)

Oxides of nitrogen mostly created from the nitrogen in the air. The highest quantity of the NO_x is produced by the diesel engine. CI engine emits all three types of the oxides of nitrogen-N₂O (nitrous oxides), NO (Nitric oxides), and NO₂ (Nitrogen Oxides). All three gases are not suitable for a clean environment because they initiate the ozone depletion, acid rain, eye’s problem other harmful things.  High temperature and high pressure produce high nitrogen oxides by the diesel engine. Burning of plant material also leads to the higher oxides of the nitrogen from the engine. SCR (Selective Catalytic Reduction) and SNCR (Selective Non-Catalytic Reduction) method are used to remove the NO_x from the exhaust gases. The quantity of NO_x reduction can be done by the EGR (Exhaust gas recirculation) or by decreasing the combustion temperature.  One of the methods to reduce the NO_x from the diesel engine is fuel additives.

2. Carbon dioxides (CO₂)

CO₂ gas is responsible for the greenhouse effect and global warming. It does not directly affect the human being. Quantity of CO₂ is the deciding factor of the health of the earth. Fuel economy is one of the methods for reducing carbon dioxide. Efficiency comes into the frame with the fuel economy. By enhancing the efficiency of the engine we can reduce the quantity of the CO₂.

3. Carbon mono oxides (CO)

It is a colorless and toxic gas. Carbon mono oxides generated because of the incomplete combustion in the engine. High equivalence ratio with the richness of the air-fuel mixture, the carbon mono oxides are increases. CI engine emits less CO compare to the SI engine because of the lean air-fuel ratio. At the starting of the CI engine, high CO generated due to the rich mixture required for starting the engine. The amounts of CO in the human body stop the supply of oxygen to the lung. A catalytic converter is a good method for reducing carbon mono oxides from the exhaust gases. Another method of minimizing the CO is fuel additives.

4.  Hydrocarbon (HC)

Not burnt fuel particle and incomplete combustion cause to emit high hydrocarbon from the diesel engine. The low temperature was found near to the cylinder wall that causes a high-temperature zone at the center of the cylinder. Hydrocarbon emission is also caused by the leakage past the exhaust valve. Hydrocarbon is a big family of alkalis, alkaline, and aromatic. Usually, the hydrocarbons are generated at the low load condition on the engine. Quantities of the HC from the engine depending upon the type of fuel, engine design. Besides that irregular operating condition causes the high HC. Hydrocarbon is toxic and promotes dangerous diseases like cancer and irritation. The catalytic converter, fuel additive, and electronic fuel injection system have the capability to reduce the HC from exhaust gases.

5.  Smoke (soot) and Particulate Matter

Smoke is the solid and liquid particles of the exhaust gases. Excessively black smoke indicates the solid or carbon particle (soot) of the exhaust gases. White smoke emitted because of the presence of vaporized water and not burnt fuel particles. Blue smoke is generated due to the higher concentration of not burnt fuel particles.

Particulate Matter (PM) is the second-highest gas emission from the CI Engine. PM can be defined as “any matter other than water from the diesel engine exhaust”. 

5 affecting parameters for engine performance and emissions

Engine performance and emissions are alerted by engine design and operating parameters. Changing the engine design is a very complex and expansive task. Therefore change related to the operating parameters is famous. Some operating parameters are listed below. 

1.       Compression ratio

It is the ratio of maximum volume to the minimum volume of inside the cylinder. The high compression ratio promotes the proper burning of the fuel inside the combustion chamber. Therefore higher thermal efficiency is achieved by increasing the compression ratio.  High compression ratio also leads to unnecessary sound and noise in the engine which promotes the knocking in the engine.

2.        Injection pressure

It is the pressure at which fuel injected inside the combustion chamber. At the end of the compression stroke, the fuel is sprayed into the combustion chamber. These sprayed droplets vaporize due to the heat transfer from highly compressed air and air-fuel mixture. Increasing the injection pressure leads to small fine droplets of the fuel. Small fine fuel particles provide the proper mixing of fuel and air inside the engine. Higher injection pressure reduces the timing of the combustion process inside the cylinder. Performance, emission, and economy is dependent on the combustion process. 

3.        Engine load

Performance and exhaust emissions varied with the externally applied load on the engine. The engine speed decreases with a higher load on the engine. To overcome this problem more quantity of fuel is supplied in the engine.  For the stationary engines, the load is applied by the dynamometer such as the eddy current dynamometer, hydraulic dynamometer. Break power changes proportionally with the applied load. 

4.        Injection timing

Injection timing is the time at which fuel is injected inside the cylinder. This can be altered for producing more power and fuel efficiency. Sometimes changing the injection leads to higher smoke, high vibrations, and noise from the engine.

5.        Engine speed

Engine speed varies the ignition timing of the engine. Sometimes the peak temperature achieved at lower engine speed but this speed leads to more NO_x and detonation. To mitigate this problem, engine speed, and crank angle both varied to get optimum solutions.