SRI VIDYA COLLEGE OF ENGINEERING & TECHNOLOGY DEPARTMENT OF MECHANICAL ENGINEERING
ME6602 - AUTOMOBILE ENGINEERING Question Bank
UNIT- 5 ALTERNATIVE ENERGY SOURCES
PART - A
1. List the advantages of hydrogen fuel used in automobiles.
o It can be manufactured from water through electrolysis process
o It does not contain carbon. Hence, CO and unburned HC emissions are not present
o The flame speed is highest. Hence it results in high thermal efficiency
o It has wide ignition limits.
2. What is a hybrid vehicle?
A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors.
3. What is a fuel cell?
A fuel cell is an electrochemical device that converts a source fuel into an electrical current and water. It generates electricity inside a cell through reactions between a fuel and an oxidant, triggered in the presence of an electrolyte.
4. Define detonation and pre-ignition.
The abnormal combustion occurring in IC engines is called as detonation. This results in sudden rate of pressure rise, abnormal heat release, heavy vibrations of the engine and loud noise operation. The ignition of the air-fuel mixture before the introduction of the spark in the combustion chamber is called as pre-ignition.
5. What are the advantages of an electric car? o No emissions from an electric car
It does not depend upon the availability fossil fuels 6. State the advantages of fuel cell.
o Higher efficiency than diesel or gas engines. o Quiet operation.
o Fuel cells can eliminate pollution problems
o Don’t need conventional fuels such as oil or gas and can therefore reduce economic dependence on oil producing countries, creating greater energy security for the user nation.
o The maintenance of fuel cells is simple since there are few moving parts in the system.
7. What are the types of fuel cell?
o Proton exchange membrane fuel cell
o Alkaline fuel cell
o Phosphoric acid fuel cell o Direct methanol fuel cell o Solid oxide fuel cell
o Molten carbonate fuel cell
8. What are the alternative fuels?
Alcohols, Hydrogen, Natural Gas, CNG, LNG, LPG, Bio Gas, Producer Gas, Coke oven Gas, Water Gas, Gasohol, Biodiesel
9. What are the various properties of gaseous fuel? Advantages
Gaseous fuels due to erase and flexibility of their applications possess the following advantages over solid or liquid fuels:
(a) They can be conveyed easily through pipelines to the actual place of need, thereby eliminating manual labour in transportation.
(b) They can be lighted at ease.
(c) They have high heat contents and hence help us in having higher temperatures.
(d) They can be pre-heated by the heat of hot waste gases, thereby affecting economy in heat.
(e) Their combustion can readily by controlled for change in demand like oxidizing or reducing atmosphere, length flame, temperature, etc.
(f) They are clean in use.
(g) They do not require any special burner.
(h) They burn without any shoot, or smoke and ashes.
(i) They are free from impurities found in solid and liquid fuels.
Disadvantages
(a) Very large storage tanks are needed.
(b) They are highly inflammable, so chances of fire hazards in their use is high
10. What is CNG?
Compressed Natural Gas. It is typically stored in a tank at a pressure of 3,000 to 3,600 pounds per square inch
11. . What is BIO- DIESEL? State its advantages.
Biodiesel is a non-petroleum based diesel fuel which consists of the mono alkyl esters of long chain fatty acids derived from vegetable oil and animal fats.
Advantages
o Domestically produced from non-petroleum, renewable resources
o Can be used in most diesel engines, especially newer ones
o Less air pollutants (other than nitrogen oxides)
o Less greenhouse gas emissions (e.g., B20 reduces CO2 by 15%)
o Biodegradable
o Non-toxic
o Safer to handle
12. What are advantages of LPG over conventional fuels?
o LPG contains less carbon than petrol
o LPG mixes with air at all temperatures
o In multi cylinder engines, a uniform mixture can be supplied to all cylinders o Since the vapour in the form of vapour, no crankcase dilution
o Automobile engines can use propane if they use high compression ratio. o LPG has better antiknock characteristics
o Running on LPG produces fuel saving cost of about 50% o The engine will have 50% longer life.
13. What are the disadvantages of using alcohol as an alternative fuel?
o A larger quantity of fuel is required to produce a specified power output. For example, in an automobile, more fuel is required for each mile driven.
o Low boiling points and high vapor pressures of methyl and ethyl alcohol indicate that vapor lock could be a serious problem, particularly at high
altitudes on warm summer days.
o The relatively high latent heats of methyl and ethyl alcohol cause problems in mixing these alcohols with air and transporting them through the intake manifold of the engine. Heating the intake manifold may be necessary in cold
weather or before the engine reaches operating temperatures.
o Without external heat to more completely vaporize the fuel, the engine may be difficult to start and sluggish for a considerable time after starting.
o All of the alcohols are soluble in water, but butyl alcohol is relatively insoluble compared to methyl and ethyl alcohol. Less engine power is produced as the water content of an alcohol increases. Further, vapor lock, fuel mixing and starting problems increase with water.
14. Define flame speed.
The speed at which flame travels inside the combustion chamber is called as flame speed. The unit is m/s
15. List out the various forms of natural gas.
oNatural Gas (NG)
oCompressed Natural Gas (CNG)
oLiquefied Natural Gas (LNG) 16. Write down the components of LPG equipment.
o Converter
o Mixer
o Gas Injector
17. Write down the parts of a fuel cell. o Anode
o Cathode
o Electrol
yte o Fuel
18. What are the properties of CNG? o Colourless
o Odourless
o Lighter than air
o Non - toxic
19. What are the two types of LPG used for automotive-engine fuel? o Propane based LPG
o Butane based LPG
20. What are the main components of electric and hybrid vehicles? o Gasoline engine
o Fuel tank
o Generator
o Electric motor
o Battery
o Transmission elements
21. What are the advantages of fuel cell? o The only by product from the fuel cell is either water or CO2, which can be safely disposed. o It is compact in size o As long as there is a supply of fuel, there will be generation of electricity.
22. What are the advantages of Gasohol?
Gasohol – It is the mixture of 10 % Ethanol + 90 % unleaded gasoline
o 10 % fuel savings in terms of consumption of petrol
o Less emissions than conventional petrol fuelled vehicles
PART-B
1. How bio diesel is produced? Explain and its usage in automobiles.
ANSWER:
Biodiesel is made through a chemical process called transesterification whereby the glycerin is separated from the fat or vegetable oil. The process leaves behind two products -- methyl esters (the chemical name forbiodiesel) and glycerin (a valuable byproduct usually sold to be used in soaps and other products).
The key elements of the regulatory control are as follows:
(a) Motor vehicle biodiesel specifications (Sections 2, 10 and Schedule 3)
Motor vehicle biodiesel includes pure biodiesel and biodiesel blends that are blended from pure biodiesel and motor vehicle diesel and their respective specifications are
(i) pure biodiesel that is supplied or sold for motor vehicle use has to comply with the specifications as stipulated in Schedule 3 of the Regulation. The specifications are in general comparable with European Union standard EN14214; and
(ii) biodiesel blends that are supplied or sold for motor vehicle use must be blended from pure biodiesel and motor vehicle diesel, the specification of which is stipulated in Schedule 1 of the Regulation (i.e. Euro V standard for motor vehicle diesel).
(b) Labelling requirements (Sections 11, 12 and Schedule 4)
(i) a label (sample given below) is required for selling the motor vehicle biodiesel with biodiesel content over 5%; and
(ii) the biodiesel content in the motor vehicle biodiesel expressed in percentage should not deviate from the percentage of biodiesel content indicated on the label by more than one percent (For example, a motor vehicle biodiesel with its biodiesel content of 15% specified on the label should have its biodiesel content between 14% and 16%, both inclusive).
2. Explain the operation of hydrogen fueled vehicle with neat sketch.
ANSWER:
A hydrogen vehicle is a vehicle that uses hydrogenas its onboard fuel for motive power.
... The power plants of such vehicles convert the chemical energy of hydrogen to mechanical energy either by burninghydrogen in an internal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to run electric motors.
WORKING:
Hydrogen fuel cell vehicles combine the range and refueling of conventional cars with the recreational and environmental benefits of driving on electricity.
Refueling a fuel cell vehicle is comparable to refueling a conventional car or truck; pressurized hydrogen is sold at hydrogen refueling stations, taking less than 10 minutes to fill current models. Some leases may cover the cost of refueling entirely. Once filled, the driving ranges of a fuel cell vehicle vary, but are similar to the ranges of gasoline or diesel-only vehicles (200-300 miles). Compared with battery-electric vehicles—which recharge their batteries by plugging in—the combination of fast, centralized refueling and longer driving ranges make fuel cells particularly appropriate for larger vehicles with long-distance requirements, or for drivers who lack plug-in access at home.
Like other EVs, fuel cell cars and trucks can employ idle-off, which shuts down the fuel cell at stop signs or in traffic. In certain driving modes, regenerative braking is used to capture lost energy and charge the battery.
3. Explain the working principle of fuel cell with neat sketch.
ANSWER:
A fuel cell is an electrochemical device that produces electricity without combustion by combining hydrogen and oxygen to produce water and heat.
Working Principle
A fuel cell is a device that uses hydrogen (or hydrogen-rich fuel) and oxygen to create electricity by an electrochemical process.
A single fuel cell consists of an electrolyte sandwiched between two thin electrodes (a porous anode and cathode) Hydrogen, or a hydrogen-rich fuel, is fed to the anode where a catalyst separates hydrogen's negatively charged electrons from positively charged ions (protons) At the cathode, oxygen combines with electrons and, in some cases, with species such as protons or water, resulting in water or hydroxide ions, respectively.
The electrons from the anode side of the cell cannot pass through the membrane to the positively charged cathode; they must travel around it via an electrical circuit to reach the other side of the cell.
This movement of electrons is an electrical current. The amount of power produced by a fuel cell depends upon several factors, such as fuel cell type, cell size, the temperature at which it operates, and the pressure at which the gases are supplied to the cell Still, a single fuel cell produces enough electricity for only the smallest applications.
Therefore, individual fuel cells are typically combined in series into a fuel cell stack. A typical fuel cell stack may consist of hundreds of fuel cells. Fuel cells are classified primarily by the kind of electrolyte they employ. This determines the kind of chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors.
4. Discuss the operation of an LPG propelled vehicle with neat sketch.
ANSWER:
WORKING:
The process of converting a car to run on propane is fairly demanding and requires a good knowledge of automotive systems in general to accomplish.* Several companies offer kits that include all the needed parts to perform the conversion. Those without the necessary know-how should try to find a local mechanic with experience in LP-gas conversions to get the job done. Although propane is very safe as an automotive fuel, if the system is not installed correctly, there can be safety problems.
The first step is choosing a tank. Most conversions are dual-fuel conversions, meaning you won't be replacing your old fuel system, you'll simply be adding a second. As a result, the propane tank will take up some of the storage space in your car, usually in the trunk.
A solenoid valve (LPG valve in the above diagram) must be installed on the fuel line in between the tank and the engine. This valve cuts the flow of LP gas when the car is running on gasoline and when the engine is shut off. It also has a filter built in that removes any dirt that may be in the fuel.
The next major component is called a regulator, also referred to as a vaporizer. This device performs one of the functions that a carburetor handles in a gasoline engine - it uses heat from the car's cooling fluids to vaporize the propane into gas form. Another safety check occurs at the regulator, as well. It includes an electronic circuit that cuts the flow of gas if the engine stops or stalls. The regulator is usually smaller than a regular carburetor, so finding space for it in the engine compartment shouldn't be a problem.
5. Explain the concept of hybrid vehicles with neat sketch.
ANSWER:
WORKING:
In mild hybrid cars, the electrical motor is used only when additional power is needed. The conventional engine is used to provide most of the power. The electrical motor alone cannot operate the vehicle. Whenever power is needed the electric motor acts as a side- kick to the conventional engine. Some vehicles that carry this concept is the Honda Civic and Insight.
In a full hybrid car, the electrical energy is used while the car needs less power. The gasoline energy is used when the car needs less power. Thus at lower speeds the battery drives the vehicle and at higher speed the gasoline drives the vehicle. This technology has been used in cars like Toyota Prius and Ford Escape.
Both of them though have a little different mode of operation provide the same amount of efficiency.
Advantages Of Hybrid Cars
Very less pollution. Better mileage. More reliable and comfortable.
Disadvantages Of Hybrid Cars
The initial cost will be very high – higher than other cars. Since a lot of batteries will be needed, the car will be very heavy.