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Semelhante a KERS ( Kinetic Energy Recovery system)
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KERS ( Kinetic Energy Recovery system)
- 3. 1.0. WHAT IS KERS? KERS is an acronym which stand for ‘Kinetic Energy Recovery System’. It is based on a simple principle of physics that is the law of conservation of energy which states that “energy can neither be created nor destroyed but instead can be continuously converted into different forms”. This device uses the kinetic energy generated from braking which normally goes waste in the form of heat energy. Instead this energy is stored in reservoirs (like flywheel, batteries) which can be used for later acceleration and thereby increasing the fuel efficiency. 2.0. KERS IN F1 RACING KERS made its first debut in 2009 as a driver aid designed to help both overtaking and defending position. At the push of a button, the driver can access a boost of 80 horsepower for 6.7 seconds a lap, releasing it in one go or at different points around the circuit. Vodafone McLaren Mercedes became the first team to win an F1 using a KERS equipped car when Lewis Hamilton won the Hungarian Grand Prix on July 26, 2009. The samefirmwasthefirsttodevelopF1KERSin1998,but neverracedwiththesystem until 2009. Although the use of KERS was legal in 2010 F1 racing event, many teams refused the usage of KERS due to additional weight of the batteries and motors. However, the new rules by FIA in the 2011 F1 season have increased the weight limit from 20kg to 640kg which encouraged other teams to use the KERS in their F1 cars. Since 2014, the power capacity of the KERS units were increased from 60 kilowatts (80 bhp) to 120 kilowatts (160 bhp). This was introduced to balance the sport's move from 2.4 litre V8 engines to 1.6 litre V6 TURBO engines. “Fuel efficiency is the biggest driving factor in the way road cars are being mapped out. It's something F1 needs to be part of.” - James Allison Technical Director in Lotus F1 team
- 4. Fig. 1: First car which is equipped with KERS and won the 2009 F1 season. 3.0. TYPES OF KERS Fig.2 is the schematic diagram of the types of KERS and the types are explained in detail in the following sections. KERS MECHANICAL •1) Flywheel 2) CVT Module ELECTRONIC •1) EGU 2) PCU 3) Battery Fig.2: Types of KERS
- 5. 4.0. ELECTRONIC KERS The use of motor-generator unit incorporated in the car’s transmission which converts mechanical energy into electrical energy. Once the energy has been harnessed, it is stored in batteryandit is released when required. The main components involved inthe whole system are discussed as follows. 4.1. MGU (Motor-Generator Unit) A motor-generator unit consists of a motor and a generator coupled together. The single unit will have rotor coils of the motor and generator wound around the single rotor and both the coils share the same outer field coils and magnets. Basically the MGU works in two modes. Firstly, the MGU creates power for the batteries while the car is braking. Secondly, the MGU will return the power from the batteries to add power directly to the engine, when the button is deployed which located at the steering wheel. MGU-K(where the ‘K’ stands for kinetic) is the latest usedMGU which works like an up rated version of the previous KERS, converting kinetic energy generated under braking into electricity (rather than it escaping as heat). It also acts as a motor under acceleration, returning up to 120kW power to the drivetrain from the Energy Store. MGU-H (where the ‘h’ stands for heat) is an energy recovery system connected to the turbocharger of the engine and converts heat energy from exhaust gases into electrical energy. The energy can then be used to power the MGU-K (and thus returned to the drivetrain) or be retained in the ES for subsequent use. Fig.3: MGU from Magneti Marelli
- 6. 4.2. Power Control Unit (PCU) This unit is used in KERS to serve two purposes that is to invert and controlling of switching of current from the batteries to the MGU and to monitor the status of the individualcellswithinthebattery.Thepowercontrollerisconnectedbetweentheultra- capacitor pack and the motor/generator, and controls the power flow between the two. Control is likely to be integrated into the engine ECU. The power controller require significant cooling and it can be mounted in the radiator duct cowling with fins sticking up into the air flow in the duct. Fig.4. Layout of power control unit 4.3. Super-capacitors They are an alternative for batteries due to reason that batteries tends heats up because of storage of high current and also electrical short circuits. Therefore, the FIA framed a rule to use super capacitors which are generally of 20- litre in volume. Fig.5: Super-capacitors used in KERS
- 7. 4.4. Buttons associated with KERS on F1 steering wheel Fig.6: Buttons associated with KERS The driver gets access to activate KERS ON/OFF and to select KERS modes. It gives the driver an easier access than for searching for the button which can cause distractions during a race and also might be fatal. 4.5. Working Principle of Electronic KERS The working of KERS are based on two cycle i.e. ‘charge cycle ‘and ‘boost cycle’. As the brakes are applied by the driver the MGU spins to generate electric current. The PCU sends this current or guides the current to a storage unit which can be a Li-ion Batteries or Super capacitors. The batteries or super capacitors stores this electric energy for later use when required. This cycle is known as charge cycle. BMW F1 racing were the first team to use super capacitor instead of Li-ion batteries.
- 8. Now, the driver when overtaking or to defend can access this stored energy by a press of a button located on the steering wheel. The PCU realizes this input and releases the charge from the battery pack to the KERS unit (MGU) and boosts the engine for few seconds. This cycle is known as boost cycle. The diagram above shows the location of the components of KERS in a F1 car. The energythatitcanstoreisabout400kJperlap,duringboostthepowerdeliveredisequal to 80 bhp in 6.7 seconds. Fig.7: Working Principle of Electronic KERS Fig.8: Location of KERS
- 9. 5.0. MECHANICAL KERS The concept of transferring the vehicle’s kinetic energy using flywheel energy storage was postulated in by Richard Feynman in 1950. The mechanical KERS has a flywheel as storage device which replaces the batteries, a transmission system (CVT Module) to transfer the power to the driveline which replaces the MGU as in Electronic type. The flywheel used in F1 cars are made up of thin filaments of carbon fiber wound around a steel hub. The mass is generally 30kg and runs at speed of 30,000rpm and above. This is achieved based on the principle mentioned below. The equation for the energy stored in a flywheel reads as follows: 𝐸 = 1 2 𝐼𝜔2 Where ‘E’ is the energy (Joules); ‘I’ is the inertia of the flywheel (kgm2 ), and ‘ω’ is the angular velocity (rad/sec) of the flywheel. The equation for the inertia of a flywheel is: 𝐼 = 1 2 𝑚(𝑟1 2 − 𝑟2 2 ) Where ‘m’ is the mass of the flywheel; ‘r1’ and ‘r2’ are the inner and outer radius of the flywheel respectively. Combining above two equations, we get: 𝐸 = 1 2 𝑚(𝑟1 2 − 𝑟2 2 )𝜔2 From above equation, flywheel's energy is proportional to its mass, and proportional to the square of its rotational speed or angular velocity. In other words, by doubling the mass, the energy stored is also doubled, and by doubling the speed, the energy stored is quadrupled. Thus by increasing the speed of the flywheel it will be possible to reduce the mass and size of it, to a level where its weight is insignificant while analyzing fuel efficiency. To cope up the continuous change in speed ratio between flywheel and road- wheels, a CVT Module is used and it is managed by electro-hydraulic control.
- 10. The efficiency of Electronic KERS is less compared to mechanical KERS due to reason that in electronic type there are losses associated with conversion of energy during power transfer to the driveline. Williams F1 team was the pioneers of mechanical KERS and called the system as Flybrid System. Fig.9: Layout of Mechanical KERS Fig.10: Cut-section of Flywheel Module
- 11. 6.0. PROS AND CONS OF KERS It reduces the harmful COx emission and environmental friendly system. It enhances performance of the vehicle, the performance of the car could be improved by the estimated 0.3 second per lap. It has high power capability as it can store more energy and deliver the same. Reduces the engine size in terms of cc. It has a longer operating life. It can last for around 250,000 kms. The electric energy are stored in batteries which will often heat up, if a person touch the battery there are high chance of that person getting electrocuted which will prove fatal. It adds on weight around 35kg which is more compare to the car as a whole which will hinder the location of weight of ballast which is usually below the C.G of the vehicle ,it has to be relocated if KERS are fitted. KERS are having many potential hazards due to its electrical parts during a racing or after, mechanics wear gloves in order to protect them from KERS. Only one KERS system is installed for only one braking system. If the KERS is installed in between the differential and the wheel the torque applied to each wheel must be the same. Fig.10: A rubber glove on a Renault F1 mechanic to protect from KERS
- 12. 7.0. FUTURE SCOPE OF KERS Some passenger carmanufacturershavetalked about using aKERS implementation in their cars. Volvo, usually an industry leader in innovation, have already built a development mule of their flagship S60 with a mechanical KERS implementation. The KERS implementation is actually lighter and smaller than the components needed to make a gas-electric hybrid system and tests suggest they would exhibit similar fuel consumptions. Engineers at MIT have also implemented an electric bicycle which makesuseofKERSwhichcostslesstoproducethanatypicalelectricbicycleandhence could lead to lower costs. Some of the production carmakers who adopted the principle of KERS and installed in their cars are as follows: Honda Civic Hybrid Ford Escape Hybrid Jaguar XF sedan Porsche 918 RSR variant Inconclusion,KERSisatechnologyofthepresentaswellasforthefuturedueto reason that it is environmentally friendly, reduces emissions, increase efficiency and is highly customizable and modifiable. Adoption of the KERS may permit regenerative braking and energy downsizing as a means of improving efficiency and thereby reducing fuel consumption and CO2 emissions.
- 13. 8.0. BIBLIOGRAPHY Websites: “Kinetic Energy systems in F1” by Aditya Sarkar, June 1, 2016 < http://large.stanford.edu/courses/2015/ph240/sarkar1/> <https://www.formula1.com/en/championship/inside-f1/understanding-f1- racing/Energy_Recovery_Systems.html> <https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system> <https://www.slideshare.net/harshgupta161/kinetic-energy-recovery- system-kers> <https://www.racecar-engineering.com/articles/f1-essentials-how-kers- works/> <https://www.bbc.com/sport/formula1/20496330> <https://newatlas.com/formula-one-kers/11324/> <https://www.motorsport.com/in/general/news/kers-curse-or- blessing/2858656/> Google Images. Journals: Thomas Mathews et.al. , “Flywheel Based Kinetic Energy Recovery Systems (KERS) Integrated In Vehicles”, International Journal of Engineering Science and Technology (IJEST).