Hybrid Vehicle Propulsion: Solution of AKTU Question Paper

Propulsion for Hybrid Vehicles: The AKTU Approach Question Paper is a comprehensive resource for B.Tech students looking for answers to test questions about the propulsion of hybrid vehicles. Planning for exams and understanding crucial subjects are aided.

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Important Questions For Hybrid Vehicle Propulsion:
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Section A: Short Question Hybrid Vehicle Propulsion

a. What do you mean by hybrid vehicle ?  

Ans. A hybrid vehicle is one that employs two or more distinct forms of power, such as submarines that surface with diesel and sink with batteries. 

b. Write four advantages of electric vehicle over conventional vehicle.  

Ans. Advantages of electric vehicle are as follows :  

• 1. Mechanically simpler. 
• 2. Running cost per kilometre is extremely cheap. 
• 3. Zero emission vehicle. 
• 4. They are very quiet in operation. 

c. What is meant by propulsion ? 

Ans. The action or process of pushing or pulling to drive an item is referred to as propulsion. A propulsion system is made up of a mechanical power source and a propulsor.

d. What do you mean by plug-in hybrid electric vehicle ?

Ans. A plug-in hybrid electric vehicle (PHEV) is a hybrid electric vehicle with a battery pack that can be recharged outside by plugging a charging cable into an electric power source, as well as internally by its on-board internal combustion engine-powered generator.

e. What is non-electric traction system?  

Ans. A non-electric traction system is a traction system that does not require electrical energy at any stage of vehicle movement.

f. Briefly describe hybridization of different energy storage devices. 

Ans. The hybridization of energy storage is the process of combining two or more energy storages so that the advantages of each may be maximised and the downsides can be offset by others.

g. What is induction motor drive ?  

Ans. Among commutatorless motor drives, induction motor drives are the most mature technology. When compared to DC motor drives, AC induction motor drives have several advantages, including light weight, compact volume, low cost, and high efficiency. These benefits are especially essential for EV and HEV applications.

h. What do you mean by energy storage ?

Ans. Energy storage systems are a collection of methods and technologies for storing energy. The stored energy can be used to perform valuable operations at a later time.

i. What is battery-based energy storage ? 

Ans. A battery energy storage system (BESS) is an electrochemical device that charges (or gathers) energy from the grid or a power plant and then discharges that energy when electricity or other grid services are required.

j. Enumerate environmental advantages of hybrid electric vehicle. 

Ans. One of the most significant advantages of hybrid vehicles is that they consume less gasoline than traditional vehicles, resulting in lower emissions. When driven efficiently, this makes them greener, cleaner, and better for the environment.

Section B: Previous Aktu Questions of Hybrid Vehicle Propulsion

a. Enlist the different transmission characteristics of conventional vehicle.

Ans. Transmission characteristics encompass all of the systems used to convey engine power to propel the vehicle forward. There are two basic types of transmission for automobile applications they are :
a. Manual Transmission :  

• 1. Manual gear transmission consists of a clutch, gearbox, final drive. and drive shaft as shown in Fig. The final drive has a constant gear reduction ratio or a differential gear ratio.

• 2. This ratio is determined by the frequent practise of requiring direct drive (non-reducing) in the gearbox to be in the highest gear.
• 3. The gearbox offers gear reduction ratios ranging from three to five for passenger automobiles and more for big commercial vehicles driven by petrol or diesel engines.
• 4. The highest gear ratio is determined by the vehicle’s maximum speed requirement (i.e., the smallest ratio). The gear ratio of the lowest gear, on the other hand, is decided by the necessity of the maximum tractive effort or gradeability.
• 5. Ratios between them should be spaced in such a way that they will provide the tractive effort-speed characteristics as close to the ideal as possible, as shown in Fig. 

• 6. In the first iteration, gear ratios between the highest and the lowest gear may be selected in such a way that the engine can operate in the same speed range for all the gears.  

b. Hydrodynamic Transmission :

• 1. Hydrodynamic gearboxes, which are extensively employed in passenger cars, use fluid to convey power in the form of torque and speed.
• 2. They are made up of a torque converter and an automatic gearbox. As shown in Fig. the torque converter is made up of at least three rotational elements: the impeller (pump), the turbine, and the reactor.

• 3. The impeller is attached to the engine shaft, and the turbine is connected to the converter’s output shaft, which is coupled to the multispeed gearbox’s input shaft.
• 4. The reactor is connected to the external housing in order to give a response to the fluid circulating in the converter.
• 5. The reactor’s job is to allow the turbine to generate an output torque greater than the converter’s input torque, resulting in torque multiplication.
• 6. The reactor is commonly mounted on a free wheel, so that when the starting phase is over and the turbine speed approaches that of the pump, the reactor is free to rotate.
• 7. The major advantages of hydrodynamic transmission are as follows: 
  • i. When properly matched, the engine will not stall. 
  • ii. It provides flexible coupling between the engine and the driven wheels 
  • iii. Together with a suitably selected multispeed gearbox, it provides torque-speed characteristics that approach the ideal.  
• 8. The major disadvantages of hydrodynamic transmission are its low efficiency in a stop-go driving pattern and its complex construction. 

b. Enumerate vehicle performance parameters. Explain any one in brief. 

Ans. A vehicle performance depends upon the following parameters :

a. Gradeability :  

• 1. Gradeability is commonly described as the slope (or grade angle) that a vehicle can overcome at a given constant speed, such as 100 km/h (60 mph).
• 2. Gradeability is typically defined for big commercial vehicles or off-road vehicles as the maximum grade or grade angle over the whole speed range.
• 3. When the vehicle drives on a road with relative small grade and constant speed, the tractive effort and resistance equilibrium can be written as

is called the performance factor. 

4. While the vehicle drives on a road with a large grade, the gradeability of the vehicle can be calculated as, 

b. Maximum Speed of a Vehicle : 

1. A vehicle’s maximum speed is defined as the consistent cruising speed that it can achieve with full power plant load on a flat road.

2. The maximum speed of a vehicle is determined by the balance of the vehicle’s tractive effort and resistance, or by the maximum speed of the power plant and gearbox gear ratios.

3. The tractive effort and resistance equilibrium can be expressed as 

4. This equation indicates that the vehicle reaches its maximum speed when the tractive effort, represented by the left-hand-side term in (1.10.5), equals the resistance, represented by the right-hand-side terms

c. Acceleration :

1. The acceleration performance of a vehicle is usually described by its acceleration time and the distance covered from zero speed to a certain high speed (zero to 96 km/h or 60 mph, for example) on level ground. 

2. The acceleration of the vehicle is given as 

Where    δ = The mass factor. 

3. Considering the equivalent mass increase due to the angular moments of the rotating components. The mass factor can be written as, 

Where I_w is the total angular moment of the wheels and I is the total angular moment of the rotating components associated with the power plant. 

4. Calculation of the mass factor, δ, requires knowing the values of the mass moments of inertia of all the rotating parts. In the case where these values are not known, the mass factor, δ, for a passenger car would be estimated using the following empirical relation,

Where δ₁ represents the second term on the right-hand side of equation (1.10.8), with a reasonable estimate value of 0.04, and δ₂ represents the effect of the power plant-associated rotating parts, and has a reasonable estimate value of 0.0025.

c. Compare different HEV control strategies.  

Ans. 

d. What are different energy storage techniques used in hybrid electric vehicles ?

Ans.

• 1. Energy storage systems are a collection of methods and technologies for storing energy. The stored energy can be used to perform valuable operations at a later time.
• 2. Energy can be obtained in a variety of forms, such as radiation, chemical, gravitational potential, electrical potential, electricity, raised temperature, latent heat, and kinetic.
• 3. There are several techniques and technologies for storing different types of energy. Energy storage technology is often chosen based on application, economics, system integration, and resource availability.
• 4. Energy storage systems are also involved in transforming energy from difficult-to-store forms to more handy or affordable forms.
• 5. Five key energy storage technologies are as follows : 
  • i. Electrochemical energy storage 
  • ii. Chemical energy storage 
  • iii. Thermal energy storage
  • iv. Mechanical energy storage  
  • v. Electrical energy storage 
• 6. The choice of energy storage system technology is interleaved with vehicle tractive effort for the customer usage pattern anticipated.  

e. Explain the working of parallel hybrid electric vehicle drive with block diagram of different component.  

Ans. A. Parallel Hybrid Topology :

• 1. These are the most prevalent hybrids. The wheels of the car can be powered in three ways: directly by the engine, by the electric motor alone, or by both power sources working in tandem.
• 2. In a parallel hybrid electric car, a single electric motor and an internal combustion engine are mounted to provide power to the wheels in tandem.
• 3. Because the engine and electric motor are mechanically coupled to the drive shaft, they can propel the vehicle by the engine alone, the motor alone, or both together.
• 4. The electric motor can be used as a generator to charge the energy storage devices (battery or ultra capacitors by regeneration braking or by extra power from the engine.

• 5. Because the engine is linked to the wheels by mechanical coupling, this form of hybrid is quite efficient on the highway.
• 6. Furthermore, a parallel hybrid vehicle only requires two propulsion components – an engine and an electric motor – making the system incredibly compact.
• 7. As a result, a parallel hybrid contains fewer components than a series hybrid, making the system more cost effective.
• 8. The battery is large enough to run the electric motor for up to 200 kilometres.

B. Applications : 

• 1. Toyota Prius is the most widely known example. 
• 2. Toyota also uses this system in the Yaris and Auris hatchbacks and Prius+ MPV hybrids, while cars from Audi, BMW, Citroen, Land Rover, Lexus, Mercedes-Benz, Peugeot, Porsche and Volkswagen work on the same basis.

Section 3 : Most asked Questions In Hybrid Vehicle Propulsion

a. Explain in detail the history of hybrid and electric vehicles. 

Ans. The history of hybrid and electric vehicles is as follows :

• i. 1839: Robert Anderson of Aberdeen, Scotland built the first electric vehicle. 
• ii. 1886: Historical records indicate that an electric-powered taxicab, using a battery with 28 cells and a small electric motor, was introduced in England. 
• iii. 1888: Immisch & Company built a four-passenger carriage powered by a one-horsepower motor and 24-cell battery for the Sultan of the Ottoman Empire. In the same year, Magnus Volk in Brighton, England made a three-wheeled electric car. 
• iv. 1890: Jacob Lohner, a coach builder in Vienna, Austria, foresaw the need for an electric vehicle that would be less noisy than the new gas powered cars. He commissioned a design for an electric vehicle from Austro-Hungarian engineer Ferdinand Porsche. 
• v. 1900: Porsche displayed his hybrid automobile at the 1900 Paris Exhibition. A petrol engine powered a generator, which in turn powered a tiny series of motors. The electric engine was employed to boost the car’s performance. 
• vi. 1915 : 
  • 1. Woods Motor Vehicles developed the dual power hybrid vehicle, the market’s second hybrid vehicle. Rather than merging the two power sources to produce a single output of power, the dual power used an electric battery motor to power the engine at low speeds (less than 25 km/h) and the petrol engine to propel the vehicle from these low speeds to its maximum speed of 55 km/h.
  • 2. Woods designed the parallel hybrid after Porsche invented the series hybrid.
• vii. 1960: Victor Wouk’s contributions to the development of various hybrid designs earned him the moniker “Godfather of the Hybrid.” He even converted a Buick Skylark from petrol to hybrid in 1976. 
• viii. 1978: Modern hybrid cars rely on the regenerative braking system. When a standard combustion engine car brakes, a lot of power is lost because it dissipates into the atmosphere as heat. 
• ix. 1997: The Audi Duo was the first European hybrid car put into mass production and hybrid production and consumer take up has continued to go from strength to strength over the decades.  
• x. 2000: The Toyota Prius and Honda Insight were the first mass-market hybrids to hit the market in the United States, with dozens more following suit over the next decade. The Honda Insight and Toyota Prius were two of the first mainstream hybrid electric vehicles, and both are still in production.

b. Explain social and environmental importance of hybrid and electric vehicles. 

Ans.

• 1. The social and environmental repercussions of electric and hybrid vehicles include effects on mobility and travel, the functioning of the energy supply system, the consumption of petroleum and other fuels, air pollution, and traffic noise.
• 2. It is estimated that electric vehicles can replace up to 80% of typical yearly vehicle kilometres. If overnight recharging of electric vehicles is encouraged, electricity supply networks will not need to expand capacity and will benefit from load levelling.
• 3. Although petroleum use for transportation will decrease, the benefits will vary depending on the type of fuel utilised to create recharge electricity.
• 4. The fuel mix used by power plants also has an impact on air pollution, because reductions in vehicle emissions are accompanied by increases in power plant emissions.
• 5. Traffic noise improvements are modest, with 10% electrification of light cars resulting in a 13% reduction in traffic noise impacts.
• 6. The economics and environmental impact associated with use of an electric car depends significantly on the source of the electricity : 
  • i. When electricity is generated from renewable sources, the electric automobile outperforms the hybrid vehicle.
  • ii. If the electricity is created using fossil fuels, the electric car is only competitive if it is generated on-board.
  • iii. If the power is generated with a gas turbine engine connected to a high-capacity battery and electric motor with an efficiency of 50-60%, the electric automobile is superior in many ways.
• 7. Hybrid and electric vehicles play a critical role in reducing global greenhouse gas emissions, with transport estimated to contribute to 14 % of CO₂ produced annually.

Section 4 : Hybrid Drive Train in Hybrid Vehicle Propulsion

a. Explain and compare various hybrid drive train topologies in detail.

Ans. Various hybrid drive train topologies are as follows :

• i. Series Hybrid Topology : 
  • 1. Because the power sources are connected in series, the series hybrid nomenclature was coined.
  • 2. In a series design, only the electric motor powered by a battery or generator drives the wheels.
  • 3. There is no connection between the internal combustion engine and the drive.
  • 4. The engine never drives the vehicle; instead, it generates energy for the electric motor.
  • 5. To drive the generator and charge the storage batteries, the internal combustion engine is kept at its most efficient and low-emission operating conditions.
  • 6. As a result, the electric motor transmits all of the energy required to move the vehicle to the drive shaft.
  • 7. This hybrid is also known as a range extender hybrid.
• ii. Parallel Hybrid Topology :
  • 1. These are the most prevalent hybrids. The wheels of the car can be powered in three ways: directly by the engine, by the electric motor alone, or by both power sources working in tandem.
  • 2. In a parallel hybrid electric car, a single electric motor and an internal combustion engine are mounted to provide power to the wheels in tandem.
  • 3. Because the engine and electric motor are mechanically coupled to the drive shaft, they can propel the vehicle by the engine alone, the motor alone, or both together.
  • 4. The electric motor can be utilised as a generator to charge energy storage devices (battery or ultra capacitors) through regeneration braking or additional engine power.
  • 5. Because the engine is linked to the wheels by mechanical coupling, this form of hybrid is quite efficient on the highway.
  • 6. Furthermore, a parallel hybrid vehicle only requires two propulsion components – an engine and an electric motor – making the system incredibly compact.
  • 7. As a result, a parallel hybrid contains fewer components than a series hybrid, making the system more cost effective.
  • 8. The battery is big enough that the electric motor can power the car for up to 200 kms.  
• iii. Split Power Hybrid Topology :
  • 1. Split-hybrid provides the benefits of both systems but is more expensive and difficult.
  • 2. The gearbox (planetary gear system) divides engine power into two parts, one of which is supplied directly to the drive and the other is turned into electrical energy by an alternator and stored in the high-voltage (HV) battery.
  • 3. Both the electric motor and the internal combustion engine can offer power to the car at the same time.
  • 4. It is also feasible to use solely electricity.

b. Explain electric traction systems and their advantages in detail. 

Ans. A. Electric Traction System : 

• 1. The traction system in which driving force is achieved from electric motors for its location is called electric traction.  
• 2. Following are requirements of electric traction system : 
  • i. The maximum tractive effort should be used at the start in order to achieve quick acceleration.
  • ii. Equipment should be able to resist short-term overloads.
  • iii. Braking should be done in such a way that the brake shoes wear as little as feasible, and energy should be regenerated and returned to the supply as much as possible throughout the braking period.
  • iv. Simple speed control.
  • v. The equipment necessary should be minimal, efficient, and inexpensive to purchase and maintain.
• 3. Three main types of electric traction systems are :
  • i. DC electric traction system, 
  • ii. AC electric traction system, and 
  • iii. Composite system.  

B. Advantages of Electric Traction : 

• 1. It is the cleanest and healthiest traction system when compared to all other systems.
• 2. It can be placed into service without wasting time.
• 3. The maintenance and operating costs are relatively inexpensive.
• 4. Electric traction is most cost-effective in high-traffic locations, especially if electrical energy is inexpensive.
• 5. Vibrations are reduced in electrically powered vehicles because the torque exerted by the electric motor is continuous.
• 6. There are no problems during the period of abrupt and temporary overloading since the system is capable of taking additional energy from the supply network.

C. Disadvantages of Electric Traction :  

• 1. High initial expenditure is involved for power system, if electric traction is involved. 
• 2. Failure of power supply for a few minutes paralyses the whole system. 
• 3. Additional equipment required for regeneration adds to the overall cost.

Section 5 : Electric Vehicles In Hybrid Vehicle Propulsion

a. Explain the working of the different electric components used in hybrid electric vehicles. 

Ans. Major components of an electric vehicle are shown in Fig. and are discussed below :

• i. Power Pack (Battery) :
  • 1. Electric car manufacturers employ three types of rechargeable batteries. There are lead-acid batteries, nickel metal hydride (NiMH) batteries, and
  • 2. These weighty batteries take up a lot of room.
  • 3. The vehicle’s limited range and relatively low maximum speed are operational issues.
  • 4. At the moment, the key advantage of lead-acid batteries is their established technology, which is widely accepted in the automotive industry.
• ii. Motor :  
  • 1. The high-torque electric motor is the primary mover in an electric vehicle.
  • 2. The motor is responsible for converting the energy stored in the power pack into mechanical motion.
  • 3. The electric motor’s high torque enables speedy acceleration.
  • 4. The power from the motor is transmitted straight to the wheels or via the trans axle, which propels the vehicle.
  • 5. During braking, the motor serves as a generator and recharges the batteries (regenerative braking).
  • 6. The type of drive motor is one of several options. The fundamental option is to use an AC or a DC motor.
  • 7. The AC motor has several control advantages, but the DC supplied by the batteries must be converted using an inverter.
  • 8. For smaller vehicles, a DC shunt winding motor rated at around 50 kW is a popular choice, although AC motors are expected to become the most popular.
• iii. Charger : 
  • 1. Charger is a battery charging device.  
  • 2. Chargers get electricity from outside sources, such as the utility grid or solar power plants. 
  • 3. AC power is converted to DC power, which is then stored in the battery.
  • 4. The output of the smart charger is connected to the power pack, ensuring that optimal current and voltage are maintained at all times.
• iv. Controller :
  • 1. EVs have a computerised motor controller.
  • 2. The electric vehicle controller is the electronics package that runs between the batteries and the motor to control the speed and acceleration of the electric vehicle, much like a carburettor does in a gasoline-powered vehicle.
  • 3. This regulates the flow of energy from the power pack to the motor in direct connection to accelerator pressure.
  • 4. It ensures precise speed control and efficient energy utilisation in both forward and reverse directions.
  • 5. Voltage and amperage ranges are used to rate speed controllers.
• v. DC/DC Converter : 
  • 1. To recharge the auxiliary battery, the DC/DC converter converts DC power from an on-board 200-800 V high voltage battery into lower DC voltage.
  • 2. In an electric car, a 12 V auxiliary battery is typically used to power all 12 V accessories such as lights, wiper and window motors, pumps, horns, and so on.
  • 3. EVs lack an alternator to keep the battery charged.
  • 4. If the DC/DC converter fails at night or the battery pack drops below the converter’s low voltage shut-off, the auxiliary battery will have enough charge to get the car home.

b. What do you mean by hybridization of different energy storage devices ?  

Ans.

• 1. Energy storage hybridization is the process of combining two or more energy storages so that the advantages of one may be maximised and the downsides can be offset by others.
• 2. For example, combining a chemical battery and an ultracapacitor can overcome the poor specific power of electrochemical batteries and the low specific energy of ultracapacitors, resulting in high specific energy and high specific power.
• 3. The hybridised energy storage is made up of two primary energy storages: one with a high specific energy and one with a high specific power.
• 4. The basic operation of this system is illustrated in Figure.  In high power demand operations, such as acceleration and hill climbing, both basic energy storages deliver their power to the load as shown in Fig.(a). 

• 5. In low power demand operations, such as constant speed cruising, the high specific energy storage will send its power to the load and charge the high specific power storage to restore the charge lost during high power demand operations, as shown in Fig (b).
• 6. During regenerative braking operations, the high specific power storage absorbs the majority of the peak power, while the high specific energy storage absorbs only a portion of it.
• 7. As a result, the entire system would be significantly lighter and smaller in weight and size than if only one of them was the energy storage.

Section 6 : Energy Storage System In Hybrid Vehicle Propulsion

a. Explain the process of fuel cell-based energy storage. 

Ans.

• 1. The fuel cell can be utilised to store energy by combining it with a fuel generating device to form a Regenerative Fuel Cell (RFC) system.
• 2. RFC can convert electrical energy to a storable fuel, which can subsequently be used in a fuel cell reaction to generate electricity as needed.
• 3. The most prevalent varieties of RFCs employ hydrogen as the energy storage medium, which is created through water electrolysis.
• 4. RFC system uses the H₂O cycle as the energy storage medium. 
• 5. Water is decomposed electrolytically into hydrogen and oxygen.  
• 6. The hydrogen is stored, whilst the oxygen can be either stored or released to the atmosphere.
• 7. When electricity is required, simply supply hydrogen to the fuel cell, and electrical power is produced.
• 8. This method assures that the fuel cell is always supplied with pure, fuel cell compatible hydrogen that is compressed and ready for use.
• 9. The only inputs needed are power, makeup water, and air for reactant and cooling.

b. Analyse flywheel based energy storage system. 

Ans.

• 1. A flywheel is an energy storage device similar to a battery, except that instead of storing energy chemically, it stores it in kinetic form in a rotating disc.
• 2. Normally, an electric motor accelerates the rotor (charging process) and decelerates it when the motor is switched to generating operation (discharging).
• 3. This flywheel energy system, which is made up of composite rotors spinning at thousands of rpm on frictionless magnetic bearings, may power an EV generator. The amount of energy stored in flywheels grows quadratically with the spinning speed of the rotor.
• 4. The gyroscopic effect is eliminated by having two adjacent wheels counterrotate at the same speed on a stationary shaft. By suspending the wheels in vacuum, friction is decreased to varying values.
• 5. The importance of energy storage with flywheel is to reduce the loss of mechanical energy, namely the loss of kinetic energy that consists of air friction resistance and rotary resistance.

• 6. Flywheel energy storage systems (FESS) are classified into two types based on how they reduce energy loss. They include low-speed flywheel systems and high-speed flywheel systems.
• 7. The first reduces air friction by increasing the mass of the flywheel, while the second reduces the air pressure in the flywheel’s operating environment.

Section 7 : Energy Management Strategies In Hybrid Vehicle Propulsion

a. What are the different energy management strategies used in hybrid and electric vehicles ?

Ans. Different energy management strategies used in hybrid and electric vehicle are as follows:  

A. Rule Based: The rule based strategies consist of following sub categories : 

• i. Fuzzy Based: The fuzzy based control strategies are of three types :  
  • 1. Predictive,
  • 2. Adaptive, and 
  • 3. Conventional. 
• ii. Deterministic Control: The deterministic controllers are sub divided into :
  • 1. State machine, 
  • 2. Power follower, and
  • 3. Thermostat control. 

B. Optimization Based: The optimization based strategies are following types : 

• i. Global Optimization: The global optimization methods are :  
  • 1. Linear programming methods, 
  • 2. Dynamic programming, 
  • 3. Dynamic programming, 
  • 4. Genetic algorithms. 
• ii. Real Time Optimization: The real time optimization techniques are of following types : 
  • 1. EFC minimization, 
  • 2. Robust control, and
  • 3. Model predictive. 

b. Compare different energy management strategies and write implementation issues of energy management strategies. 

Ans. Comparison : 

B. Implement Issues of Energy Management Strategies :

• 1. The energy management matrix.
• 2. Developing a strategic approach. 
• 3. Organisation’s energy policy. 
• 4. Taking responsibility for energy management
• 5. Motivating staff to save energy. 
• 6. Monitoring energy use. 
• 7. Lack of documented standards/enforcement.  
• 8. System overrides. 
• 9. Sensor location.  
• 10. Nuisance alarms.