1、AUTOMOTIVE INTERNATIONAL PROGRESS IN TECHNOLOGY SERIES Concepts in Turbocharging for Improved Efficiency and Emissions Reduction Mehrdad Zangeneh Concepts in Turbocharging for Improved Efficiency and Emissions Reduction PT-156_book.indb 1 9/18/14 10:41 AMOther SAE books of interest: Automotive 2030N
2、orth America By Bruce Morey (Product Code: T-127) Design of Racing and High-Performance Engines 2004-2013 By Douglas Fehan (Product Code: PT-157) Introduction to Internal Combustion Engines, 4th Edition By Richard Stone (Product Code: R-391) For more information or to order a book, contact: SAE INTE
3、RNATIONAl 400 Commonwealth Drive Warrendale, PA 15096 Phone: +1.877.606.7323 (U.S. and Canada only) or +1.724.776.4970 (outside U.S. and Canada) Fax: +1.724.776.0790 Email: CustomerServicesae.org Website: books.sae.org PT-156_book.indb 2 9/18/14 10:41 AMConcepts in Turbocharging for Improved Efficie
4、ncy and Emissions Reduction Edited by Mehrdad Zangeneh Warrendale, Pennsylvania, USA PT-156_book.indb 3 9/18/14 10:41 AM Copyright 2015 SAE International eISBN : 978-0-7680-8149-7 Copyright 2015 SAE International. All rights reserved. No part of this publication may be reproduced, stored in a retrie
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6、: +1-724-772-9765. Library of Congress Catalog Number 2014947146 SAE Order Number PT-156 DOI 10.4271/PT-156 Information contained in this work has been obtained by SAE International from sources believed to be reliable. However, neither SAE International nor its authors guarantee the accuracy or com
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9、lk quantities, please contact SAE Customer Service e-mail: CustomerServicesae.org phone: +1.877.606.7323 (inside USA and Canada) +1.724.776.4970 (outside USA) fax: +1.724.776.0790 Visit the SAE Bookstore at books.sae.org 400 Commonwealth Drive Warrendale, PA 15096 E-mail: CustomerServicesae.org Phon
10、e: +1.877.606.7323 (inside USA and Canada)+1.724.776.4970 (outside USA) Fax: +1.724.776.0790 PT-156_book.indb 4 9/18/14 10:41 AMv Table of Contents Introduction . vii Two-Stage Turbocharging Challenges for Increased Efficiency through Gasoline Engine Downsizing2009-01-1053 1 Variable Geometry Compre
11、ssors The Potential of Variable Compressor Geometry for Highly Boosted Gasoline Engines2011-01-0376 19 Turbocharging of Downsized Gasoline DI Engines with 2 and 3 Cylinders2011-24-0138 .33 Variable Geometry Diffuser of Turbocharger Compressor for Passenger Vehicles2003-01-0051 .49 Unconventional Com
12、pressor Configurations Parametric Studies of the Impact of Turbocharging on Gasoline Engine Downsizing2009-01-1472 57 Electrically Assisted Turbocharging Coordinated Electric Supercharging and Turbo-Generation for a Diesel Engine2010-01-122869 About the Editor 81 PT-156_book.indb 5 9/18/14 10:41 AMP
13、T-156_book.indb 6 9/18/14 10:41 AMvii Introduction The legislative requirements to reduce the CO 2emissions from cars in Europefor example, by the European Commission setting a target to reduce CO 2emissions to 130 g/km for new 2012 vehicles with an inertia class of 1372 kg and a target of 95 g/km f
14、or similar inertia class by 2020 have resulted in significant efforts by car manufacturers to explore various methods of reducing emissions from gasoline engines. Similar targets have been implemented worldwide, including regulations to continuously reduce vehicle average fleet fuel consumption in t
15、he United States over the next decade. One of the most effective means of achieving this reduction is by reducing the cylinder stroke or downsizing the engine. Typically, 40% downsizing can result in about 20% reduction in fuel consumption. The full load torque of the original engine can only be rec
16、overed in the downsized engine by boosting the engine. However, a boosted downsized engine can match the torque of an original engine at medium and high-speed conditions, but there can be a definite torque deficit at low speeds due to the limitations on the turbocharger flow range. To improve the dr
17、ivability of highly downsized engines, new concepts in turbocharging of gasoline engines need to be developed. In this book, a number of the options currently being explored will be highlighted. The main topics to be considered are two-stage turbocharging, compressor range extension methodologies, u
18、nconventional compressor configurations, and electrically assisted turbocharging. Two-Stage Turbocharging This has been a major area of work not only in gasoline engine applications but in heavy-duty diesel and larger marine diesel turbocharging. The paper by Fraser et al. (2009-01-1053) explores so
19、me of the requirements of downsized gasoline engines and shows detailed test results for the torque produced by a downsized engine of 1.2 liters as against a 2.0-liter TGDI baseline engine with different boosting schemes. The results show that the two- stage turbocharger consisting of larger LP turb
20、ocharger for high speed, and smaller HP turbocharger for low speed, with a bypass valve can come very close to the torque characteristics of the original engine. Problems with the two-stage system are the increased costs and the complexity of the systemhence, the interest to explore other possible o
21、ptions for increasing low-speed torque of downsized engines. Variable Geometry Compressors Most standard turbochargers employ a type of recirculating casing treatment for the compressor, which helps to extend its stable operating range, especially at higher speeds. This type of casing treatment or p
22、orted shroud is generally well understood but does not usually increase the compressor stable operating range at low speeds and hence does not provide the necessary enhancements for improving the low-speed torque as required for downsized engines. Variable geometry compressor configurations either w
23、ith a variable geometry inlet guide vane or variable geometry vaned diffuser may help to increase the low-speed torque of single-stage turbochargers. In paper 2011-01-0376, a method is presented to model the effect of including a variable geometry inlet guide vane (IGV) to a centrifugal compressor i
24、n a gasoline engine by using 1D models. The paper also investigates the effect of the pre-swirl device on the axial thrust and bearing design. The method presented is limited to relatively small variation of inlet guide vanes, but still some improvement in low-speed torque is observed. In paper 2011
25、-24-0138, variable geometry IGVs are used for a highly downsized 0.9-liter engine with two- and three-cylinder configurations. The vane setting angles of the IGV are optimized for different speeds by setting the IGV at angles of up to 60 degrees for low engine speeds, and as a result, the low engine
26、 torque can match the torque on the original engine. Another possibility to improve the low-speed torque of single-stage turbochargers is to use a variable geometry vaned diffuser. This is discussed in paper 2003- 01-0051. Unconventional Compressor Configurations A different approach to meet the req
27、uirement to improve low-speed torque of downsized engines is proposed in paper 2009-01-1472. In this paper, a parallel flow back- to-back centrifugal compressor is coupled with a single variable geometry turbine. By using the back-to-back compressor configuration, the compressor tip radius can be re
28、duced and the turbocharger can be run at higher speeds and relatively higher U/C ratios. It is shown that this approach can also improve the low-speed engine torque of downsized engines. Electrically Assisted Turbocharging In paper 2010-01-1228, a decoupled electrically assisted turbo-generator and
29、supercharger system is proposed for diesel engine application that can also provide high torque at low-speed conditions for downsized gasoline engines. All of the preceding approaches to solve the problem of low torque at low speeds for highly downsized engines have their own respective pros and con
30、s and are the subjects of current intensive research. But clearly, engine manufacturers have to develop cost-effective means of boosting highly downsized engines if they are to meet the 2020 requirements for reduction in CO 2emissions. PT-156_book.indb 7 9/18/14 10:41 AMPT-156_book.indb 8 9/18/14 10
31、:41 AM1 ABSTRACT In order to achieve the required future CO 2reduction targets significant further development of both gasoline and diesel engines is required. One of the main methods to achieve this with the gasoline engine in the short to medium term is through the application of engine downsizing
32、, which has resulted in numerous downsized engines already being brought to production. It is, however, considered that there is still significant further CO 2reduction potential through continued development of this technology. This paper considers the future development of gasoline engine downsizi
33、ng in the short to medium term and the various technologies that can be applied to further increase the efficiency of operation. As such this paper covers, among other areas, fundamental engine layout and design, alternative boosting systems, methods of increasing part load efficiency and vehicle mo
34、delling, and uses analysis tools and engine test results to show the benefits achievable. INTRODUCTION It is well known that reducing carbon dioxide (CO 2 ) emissions has been the main driver in passenger vehicle powertrain technology over recent years, and it is expected that this is going to conti
35、nue. In recent time this has largely been driven by evolving emissions legislation and taxation strategies, however increasing public awareness about the impact of global warming and the rising cost of crude oil can also be seen to be shaping consumer choices for low fuel consumption vehicles. Europ
36、ean Union (EU) fleet fuel economy data has shown that over the past 14 years there has been a continual reduction in drive cycle CO 2emissions, largely through developments in diesel engine technology and increased diesel sales 1. In addition in the UK there has been an increase in sales of smaller
37、vehicles, with inherently better fuel economy. In order to meet future global emissions goals, in the short to medium term it will be necessary for significant further development of the gasoline engine. Recent studies into the development of future powertrains and the potential improvements in fuel
38、 economy that can be achieved, report that spark ignition engines have more potential improvement than compression ignition engines, and predict that the relative advantage of diesel over gasoline engines is going to be reduced 2-4. In recent years a range of different technologies have been develop
39、ed for gasoline engine fuel economy improvement, with the most significant being: Gasoline direct injection (GDI) (Homogenous and stratified lean) Exhaust gas recirculation (EGR) Variable valvetrains (camshaft phasing, profile switching, variable lift and duration systems) Controlled auto ignition (
40、CAI) or homogeneous charge compression ignition (HCCI) Gasoline engine downsizing Friction reduction 2009-01-1053 Neil Fraser, Hugh Blaxill, Grant Lumsden and Mike Bassett MAHLE Powertrain Ltd Challenges for Increased Efficiency through Gasoline Engine Downsizing Copyright 200 SAE International 9 SA
41、E Int. J. Engines | Volume 2 | Issue 1 PT-156_book.indb 1 9/18/14 10:41 AM2Of these, gasoline engine downsizing has been shown to have the most immediate potential for fuel economy improvement. This has lead to numerous turbocharged engines being introduced into production, initially in Europe, but
42、now also in the US, with claims of drive cycle fuel economy improvement between 10 and 17% 5-7. Significant research work is continuing in this area with the aim of further fuel economy improvements through either direct efficiency improvements or increased degrees of engine downsizing 8-13. Figure
43、1 shows the performance levels achieved by GDI and port fuel injection (PFI) downsize engines currently in production. In comparison the current status of the MAHLE Downsize Demonstrator engine 14 is shown with an additional curve showing further development potential as an indication of what is ach
44、ievable with increased levels of downsizing. Figure 1: Gasoline downsize engine full load performance The main technical challenges to being able to realize the further development of downsized engines are: Combustion limitations Increased propensity to knock leads to reduced compression ratio and r
45、etarded spark timing, hence lower efficiency Steady state low speed torque With increased downsizing, low speed BMEP requirement increases to maintain acceptable performance Transient performance Transient response needs to be maintained with increased low speed torque requirement Engine geometry/la
46、yout As engine capacity falls below 1 litre, bore size and/or cylinder number will require re-optimization Part load fuel economy As downsizing continues the fuel economy gains inherently reduce, measures will need to be taken to mitigate this This paper looks at the development of gasoline engine d
47、ownsizing in the short to medium term with regard to more widespread application of the technology and to the possibility of further efficiency improvements. COMBUSTION SYSTEM DIRECT INJECTION As engine specific output is increased the issue of knocking combustion takes on greater significance, requ
48、iring the compression ratio to be reduced in order to maintain acceptable combustion phasing at all load. As the compression ratio is reduced so is the indicated efficiency at part load leading to an increase in part load brake specific fuel consumption (BSFC). In order to achieve the best improveme
49、nt in fuel economy the compression ratio needs to be maintained as high as possible. This requirement has led to the widespread introduction of direct injection to turbocharged engines. Injecting the fuel directly into the combustion chamber, as opposed to the port, reduces the charge temperature in cylinder through the latent heat of vaporisation of the fuel. This has the combined effect of both increasing charge density, and hence volumetric efficiency, and also moving the knock limit of the combustion system. As a consequence it
