1、PT-159 Kinetic Energy Recovery Systems for Racing Cars Edited by Alberto Boretti Kinetic Energy Recovery Systems for Racing Cars Edited by Alberto Boretti PROGRESS IN TECHNOLOGY SERIES PROGRESS IN TECHNOLOGY SERIES In 2009, the Federation Internationale de lAutomobile (FIA) began allowing kinetic en
2、ergy recovery systems (KERS) to be used in Formula One (F1) competition. Still considered experimental, this technology is undergoing development in the racing world but has yet to become mainstream for production vehicles. The preface of this book details the theory behind the KERS concept. It desc
3、ribes how kinetic energy can be recovered, and the mechanical and electric systems for storing it. Flybrid systems are highlighted since they are the most popular KERS developed thus far. The KERS of two racing vehicles are pro led: the Dyson Lola LMP1 and Audi R18 e-tron quattro. Four SAE technical
4、 papers follow the preface and focus on the use of KERS technology in F1 racing. The rst paper examines the factors that in uence hybrid performance and enable optimization for di erent racing circuits. The second paper describes a Flybrid KERS designed for the 2009 F1 season. The third paper consid
5、ers the development of an electric KERS for the 2009 F1 season. The fourth paper presents the challenges and opportunities of the 2014 F1 engine and powertrain rules, particularly as they pertain to KERS. About the editor Alberto Boretti is presently an associate professor of mechanical engineering
6、at RMIT University, Australia. After he received his PhD in 1988, he was a senior researcher and project and team manager within the automotive industry for 17 years. He returned to academia as senior research fellow and then associate professor. He has been involved in many car racing engine projec
7、ts, mostly with Ferrari, Alfa Romeo, and Fiat Auto Corse, from F1 to Super Touring to Rally. He has also contributed to several motorcycle racing engine projects, from Moto GP to Superbike.Kinetic Energy Recovery Systems for Racing CarsOther SAE books of interest: Brake Design and Safety, Third Edit
8、ion By Rudolf Limpert (Product Code: R-398) Electric and Hybrid-Electric VehiclesBraking Systems and NVH Considerations By Ronald K. Jurgen (Product Code: PT-143/4) Engine Design Concepts for World Championship Grand Prix Motorcycles By Alberto Boretti (Product Code: PT-155) For more information or
9、to order a book, contact SAE International at 400 Commonwealth Drive, Warrendale, PA 15096-0001, USA; phone 877-606-7323 (U.S. and Canada only) or 724-776-4970 (outside U.S. and Canada); fax 724-776-0790; email CustomerServicesae.org; website http:/books.sae.org.Kinetic Energy Recovery Systems for R
10、acing Cars Edited by Alberto Boretti Warrendale, Pennsylvania, USA Copyright 2013 SAE International eISBN: 978-0-7680-8000-1400 Commonwealth Drive Warrendale, PA 15096-0001 USA E-mail: CustomerServicesae.org Phone: 877-606-7323 (inside USA and Canada)724-776-4970 (outside USA) Fax: 724-776-0790 Copy
11、right 2013 SAE International. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, distributed, or transmitted, in any form or by any means without the prior written permission of SAE International. For permission and licensing requests, contact SAE Permi
12、ssions, 400 Commonwealth Drive, Warrendale, PA 15096-0001 USA; e-mail: copyrightsae.org; phone: 724-772-4028; fax: 724-772-9765. ISBN 978-0-7680-7994-4 Library of Congress Catalog Number 2013934253 SAE Order Number PT-159 DOI 10.4271/PT-159 Information contained in this work has been obtained by SAE
13、 International from sources believed to be reliable. However, neither SAE International nor its authors guarantee the accuracy or completeness of any information published herein and neither SAE International nor its authors shall be responsible for any errors, omissions, or damages arising out of u
14、se of this information. This work is published with the understanding that SAE International and its authors are supplying information, but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be
15、sought. To purchase bulk quantities, please contact SAE Customer Service e-mail: CustomerServicesae.org phone: 877-606-7323 (inside USA and Canada) 724-776-4970 (outside USA) fax: 724-776-0790 Cover image: The Flybrid KERS for the Dyson Racing ALMS car. (Courtesy of Flybrid Automotive Limited) Visit
16、 the SAE Bookstore at books.sae.orgv Table of Contents Introduction 1 Friction and Regenerative Braking 1 Motorsport and Newtons Second Law 1 Recovery of Kinetic Energy 2 Flybrid Mechanical KERS 3 The Dyson Lola LMP1 Car with Flybrid KERS 5 The Audi R18 e-tron Quattro Le Mans 5 Overview of Four Pape
17、rs on KERS and F1 Racing 6 Papers 9 Cross, D., Optimization of Hybrid Kinetic Energy Recovery Systems (KERS) for Different Racing Circuits, SAE Technical Paper 2008-01-2956, 2008, doi:10.4271/2008-01-2956. 9 Cross, D. and Brockbank, C., Mechanical Hybrid System Comprising a Flywheel and CVT for Moto
18、rsport and Mainstream Automotive Applications, SAE Technical Paper 2009-01-1312, 2009, doi:10.4271/2009-01-1312. 17 Tamotsu Kawamura, Hirofumi Atarashi, and Takehiro Miyoshi, High Power Density Motor for Racing Use, SAE Technical Paper 2011-39-7221, 2011, doi:10.4271/2011-39-7221 29 Boretti, A., KER
19、S Braking for 2014 F1 Cars, SAE Technical Paper 2012-01-1802, 2012, doi:10.4271/2012-01-1802 35 About the Editor 49 1 Introduction Friction and Regenerative Braking While the propulsive power used to increase the speed of a vehicle is perceived as a positive energy transfer, the braking power spent
20、to reduce the speed of the vehicle is a source of frustration. The work done by the brakes is dissipated in heat, never to be recovered. There is no good reason why it shouldnt be otherwise. A device as simple in principle as the flywheel of a childs toy car may be applied in production vehicles to
21、recover the kinetic energy. In 2009, the Fdration Internationale de lAutomobile (FIA) decided to allow Kinetic Energy Recovery Systems (KERS). These devices came in many varieties for race cars, with the most promising storing the mechanical energy in a flywheel, but electric systems also received a
22、ttention. The systems gave drivers a bit more acceleration but were not very efficient at capturing deceleration energy and saved very little fuel, being used mostly as a strategic device with many limitations. KERS were dropped from Formula 1 during the 2010 season, but they were back again in 2011
23、. So far, this F1 technology has not made it onto a car for the rest of us. Fuel consumption could be reduced by 1520% for typical gasoline-powered passenger cars and 1015% for typical diesel-powered cars. The technology does need further research and development, and the research for racing cars, i
24、f properly addressed by rules, may help considerably. What are needed are less possible constraints to develop the KERS, as unfortunately experienced in the case of the novel F1 2014 rules, but very stringent fuel economy targets for a race. With mechanical energy being stored as mechanical energy b
25、efore it is used again, less than one-third of the braking energy is lost. The regenerative braking system that a present hybrid electric vehicle uses, in which mechanical energy is converted to electrical energy and then stored as chemical energy before making the reverse journey back to help power
26、 the car, only recovers around one-third of the braking energy. Energy management is going to play a significant role in the future of endurance racing, but with some changes to the sporting rules, Formula 1 might also benefit significantly to become more relevant to road cars development without pe
27、nalizing the sporting event. Motorsport and Newtons Second Law According to Newtons second law, a particle will accelerate when it is subjected to unbalanced forces. Kinetics is the study of the relations between unbalanced forces and the resulting changes in motion. Without losing too much in gener
28、alities, a racing car may be assimilated to a particle, and the kinetics of a racing car are described through the use of Newtons second law, F=ma, expressing the balance of all the forces that apply to the car F and the product of the mass m by the acceleration of the car a. The total force is the
29、sum of all the propulsive and resistance powers, the engine propulsive power P e , the kinetic energy recovery system propulsive power P k , the rolling resistance R r , the friction braking power R f , the aerodynamic resistance R a , the kinetic energy recovery system braking power R k , divided b
30、y the speed of the car v. If the previous equation is valid at any 2 time the car is covering a lap, then the integration over the lap time gives all the propulsive energy needed. In a standard powertrain with friction-only brakes, the racing over one lap is a sequence of propulsive engine and frict
31、ion braking power applications that produce sharp accelerations and even sharper decelerations. P eis the instantaneous power of the engine obtained by converting the fuel energy flow rate in the internal combustion engine (ICE). R fis the instantaneous braking power dissipating the kinetic energy o
32、f the car in heat. Therefore, in a standard powertrain without a KERS, the kinetic energy of the car, mv 2 , is generated by the engine delivering power over the acceleration time, but this kinetic energy is then dissipated in heat during the deceleration time. Clearly, if the kinetic energy of the
33、car could be stored some way during the deceleration and then used again in the following acceleration, this would translate to huge savings in the fuel consumed to cover one lap. This recovery of the kinetic energy is the common practice of hybrid vehicles and the main reason why hybrid cars consum
34、e much less fuel than conventional cars. The recovered kinetic energy is obviously a fraction of the energy stored during regenerative braking. To complicate the practical use of kinetic energy recovery systems in F1 racing, there are rules to define the energy transfer to and from the KERS. Recover
35、y of Kinetic Energy In the previous section, we applied Newtons second law to establish the instantaneous relationship between the net force acting on a racing car and the resulting acceleration of the car. A novel perspective that integrates the forces with respect to the displacement of the car ma
36、y be considered. Integration with respect to displacement leads to the equations of work and energy. If the work done by the force F during the displacement dr is defined as dU=Fdr, then the work done on a car of mass m moving along a path under the action of the force F is equal to the variation of
37、 kinetic energy: ) ( 2 1 2 1 2 2 2 1 v v m U =All hybrid cars currently on the market use electric KERS comprised of an electric motor/ generator and a traction battery. During braking, the electric generator connected to the driveline brakes the car, producing electric energy that is stored in the
38、battery. During acceleration, the battery returns the energy stored to the motor, supplementing the ICE power supply. This solution has advantages and disadvantages. The advantage is the opportunity to decouple the internal engine power supply from the electric motor power supply from the load deman
39、d, and the opportunity to use the recovered kinetic energy when more convenient, without any restriction on the storage time. The disadvantage is the conversion of mechanical energy to electric energy to chemical energy and then back to electric and mechanical energy, which is done with low efficien
40、cy and limits to the rates of charge and discharge of the battery.3 An alternative to the electric KERS is the mechanical KERS, for which a flywheel is connected to the driveline through a continuously variable transmission that spins up the flywheel during braking and slows it down during accelerat
41、ion. This system has the disadvantage of a limited storage time and the reduced flexibility in the coupling of the kinetic energy system with the load demand, but has significantly better round trip efficiency and an inherently higher power capability. The mechanical KERS has not been adopted so far
42、 in any passenger car offered on the market. In addition to mechanical and electric KERS, there is also the opportunity to design the system using hydraulic components, but this is done more often in heavy-duty vehicles and has not been considered so far in racing applications. The KERS may in theor
43、y permit a much sharper acceleration of the car, supplementing the ICE power supply. However, as in everything else of this world, there is a downfall. If a passenger car has to be slowed down during city driving, clearly this can be done through the KERS system. But it is not possible to slow down
44、an F1 car with the same power of todays friction brakes by using todays KERS alone; technical regulations pose further obstacles that add to the issues of vehicle stability and braking efficiency to limit the actual KERS usage. Presently, the KERS is used more for strategic purposes than for fuel sa
45、vings. The KERS is used as a limited torque boost to defend a position or to gain a position, and certainly not to save fuel, regenerating most of the braking energy in the energy deceleration event to be used in the subsequent acceleration. Flybrid Mechanical KERS The Flybrid KERS is certainly the
46、most popular F1 KERS developed so far. Figure 1 presents the original CVT-based Formula 1 KERS by Flybrid (courtesy of Flybrid Automotive Limited). The original Flybrid KERS was a small, lightweight device that was designed to meet the FIA regulations for the 2009 Formula 1 season. Key system featur
47、es were a flywheel made of steel and carbon fiber that rotated at over 60,000 rpm inside an evacuated chamber (the Fig. 1 The original CVT-based Formula 1 KERS by Flybrids. (Courtesy of Flybrid Automotive Limited)4 flywheel casing featured containment to avoid the escape of any debris in the unlikel
48、y event of a flywheel failure; the flywheel was connected to the transmission of the car on the output side of the gearbox via several fixed ratios), a clutch and a Continuously Variable Transmission (CVT), a 60-kW power transmission in either storage or recovery, 400 kJ of usable storage (after accounting for internal losses), a total system weight of 25 kg, and a total packaging volume of 13 L. The layout of the device was tailored to meet the customers requirement, resulting in a truly bespoke solution that f
