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Viewing 1 to 30 of 520
2015-06-15
Technical Paper
2015-01-2253
Kimitoshi Tsuji, Katsuhiko Yamamoto
It is important for vehicle concept planning to estimate fuel economy and the influence of vehicle vibration in advance, on virtual engine specifications and a virtual vehicle frame. In this paper, I will show the power plant model with electrical starter, battery and alternator that can predict transient torque and combustion heat results. Also vibration result with the power plant model connected to vehicle inertia model will be shown. The power plant was 1.3L 4cyl NA. The discussed vehicle was small size and 1300kg. The power plant model was realized by energy based model using VHDL-AMS. Here, VHDL-AMS is modelling language stored in IEC international standard (IEC61691-6) and can realize multi physics on 1D simulation. The modeling language supports electrical, magnetic, thermal, mechanical, fluidic and compressive fluidic domain. The model was created in house by fully VHDL-AMS and validated on ANSYS SIMPLORER.
2015-04-14
Technical Paper
2015-01-0777
Yuya Abe, Akimitsu Sugiura, Kaori Doi, Masamichi Shibata, Nozomi Yokoo, Koichi Nakata
Abstract Improving the engine efficiency to respond to climate change and energy security issues is strongly required. In order to improve the engine efficiency, lower fuel consumption, and enhance engine performance, OEMs have been developing high compression ratio engines and downsized turbocharged engines. However, higher compression ratio and turbocharging cause cylinder pressure to increase, which in turn increases the demand voltage for ignition. To reduce the demand voltage, a new ignition system is developed that uses a high voltage Zener diode to maintain a constant output voltage. Maintaining a constant voltage higher than the static breakdown voltage helps limit the amount of overshoot produced during the spark event. This allows discharge to occur at a lower demand voltage than with conventional spark ignition systems. The results show that the maximum reduction in demand voltage is 3.5 kV when the engine is operated at 2800 rpm and 2.6 MPa break mean effective pressure.
2015-04-14
Technical Paper
2015-01-1169
Akira Yamashita, Masaaki Kondo, Sogo Goto, Nobuyuki Ogami
Abstract The new Toyota FCV “Mirai” has reduced the weight, size, and cost of the high-pressure hydrogen storage system while improving fueling performance. The four 70 MPa tanks used on the 2008 Toyota FCHV-adv were reduced to two new larger diameter tanks. The laminated structure of the tanks was optimized to reduce weight, and a high-strength low-cost carbon fiber material was newly developed and adopted. The size of the high-pressure valve was reduced by improving its structure and a high-pressure sensor from a conventional vehicle was modified for use in a high-pressure hydrogen atmosphere. These innovations helped to improve the weight of the whole storage system by approximately 15% in comparison with Toyota FCHV-adv, while reducing the number of component parts by half and substantially reducing cost. The time required to fuel the FCV was greatly reduced by chilling the filling gas temperature at the hydrogen filling station to −40°C (as per SAE J2601).
2015-04-14
Technical Paper
2015-01-1101
Jun Hakamagi, Tetsuya Kono, Ryoji Habuchi, Naoki Nishimura, Masahiro Tawara, Naoki Tamura
Abstract In response to increasing demands for measures to conserve the global environment and the introduction of more stringent CO2 emissions regulations around the world, the automotive industry is placing greater focus on reducing levels of CO2 through the development of fuel-efficient technologies. With the aim of improving fuel economy, a new continuously variable transmission (CVT) has been developed for 2.0-liter class vehicles. This new CVT features various technologies for improving fuel economy including a coaxial 2-discharge port oil pump system, wider ratio coverage, low-viscosity CVT fluid, and a flex start system. This CVT is also compatible with a stop and start (S&S) system that reduces fuel consumption by shutting off the engine while the vehicle is stopped. In addition, the development of the CVT improves driveability by setting both the driving force and engine speed independently.
2015-04-14
Journal Article
2015-01-1652
Yukikatsu Ozaki, Keisuke Sekiya
Abstract This research developed a new measurement technology for thermal analysis of the heat radiation from a hybrid transaxle case surface to the air and improved the heat radiation performance. This heat flux measurement technology provides the method to measure heat flux without wiring of sensors. The method does not have effects of wiring on the temperature field and the flow field unlike the conventional methods. Therefore, multipoint measurement of heat flux on the case surface was enabled, and the distribution of heat flux was quantified. To measure heat flux, thermal resistances made of plastic plates were attached to the case surface and the infrared thermography was used for the temperature measurement. The preliminary examination was performed to confirm the accuracy of the thermal evaluation through heat flux measurement. The oil in the transaxle was heated and the amount of heat radiation from the case surface was measured.
2015-04-14
Technical Paper
2015-01-1254
Daishi Takahashi, Koichi Nakata, Yasushi Yoshihara, Yukinori Ohta, Hiroyuki Nishiura
Abstract In recent years, enhancing engine thermal efficiency is strongly required. Since the maximum engine thermal efficiency is especially important for HVs, the technologies for improving engine thermal efficiency have been developed. The current gasoline engines for hybrid vehicles have Atkinson cycle with high expansion ratio and cooled exhaust gas recirculation (EGR) system. These technologies contribute to raise the brake engine thermal efficiency to more than 38%.In the near future the consumers demand will push the limit to 40% thermal efficiency. To enhance engine thermal efficiency, it is essential to improve the engine anti-knock quality and to decrease the engine cooling heat loss. To comply with improving the anti-knock quality and decreasing the cooling heat loss, it is known that the cooled EGR is an effective way.
2015-04-14
Technical Paper
2015-01-1268
Tomohiro Shinagawa, Masahito Kudo, Wataru Matsubara, Takashi Kawai
Abstract Toyota Motor Corporation is developing a series of engines belonging to its ESTEC (Economy with Superior Thermal Efficient Combustion) development concept. This paper describes the development of 8NR-FTS after the subsequent launch of the 2.0-liter DI Turbocharged 8AR-FTS. 8NR-FTS is a 1.2-liter inline 4-cylinder spark ignition downsized turbocharged direct injection (DI) gasoline engine. By following the same basic concepts as 8AR-FTS engine [1], the 8NR-FTS incorporates various fuel efficient technologies such as a cylinder head with an integrated exhaust manifold, the Atkinson cycle using the center-spooled variable valve timing with mid-position lock system (VVT-iW), and intensified in-cylinder turbulence to achieve high-speed combustion.
2015-04-14
Technical Paper
2015-01-1005
Masahide Miura, Yuki Aoki, Nobusuke Kabashima, Takahiko Fujiwara, Toshitaka Tanabe, Akira Morikawa, Hirotaka Ori, Hiroki Nihashi, Suguru Matsui
Abstract Countries and regions around the world are tightening emissions regulations in reaction to the increasing awareness of environmental conservation. At the same time, growing concerns about the depletion of raw materials as vehicle ownership continues to increase is prompting automakers to look for ways of decreasing the use of platinum-group metals (PGMs) in the exhaust systems. This research has developed a new catalyst with strong robustness against fluctuations in the exhaust gas and excellent nitrogen oxide (NOx) conversion performance. This catalyst incorporates rhodium (Rh) clusters with a particle size of several nanometers, and stabilized CeO2-ZrO2 solid-solution (CZ) with a pyrochlore crystal structure as a high-volume oxygen storage capacity (OSC) material with a slow O2 storage rate.
2014-10-13
Technical Paper
2014-01-2574
Tenghua Shieh, Kiyotaka Yamashita, Oana Nitulescu, Satoshi Hirano, Norio Inami, Hiroshi Moritani
Abstract This paper focuses on the fuel contribution to crankcase engine oil degradation in gasoline fueled engines in view of insoluble formation. The polymerization of degraded fuel is responsible for the formation of insoluble which is considered as a possible cause of low temperature sludge in severe vehicle operating conditions. The main objective of the study is to understand the mechanism of formation of partially oxidized compounds from fuel during the combustion process, before their accumulation in the crankcase oil. A numerical method has been established to calculate the formation of partially oxidized compounds in spark ignition engines directly, by using 3D CFD. To further enable the possibility of running a large number of simulations with a realistic turn-around time, a coupled approach of 3D CFD (with simplified chemical mechanism) and 0D Kinetics (with full chemical mechanism) is proposed here.
2014-10-13
Technical Paper
2014-01-2809
Kohei Yoshida, Yusuke Nozaki, Toshihiro Mori, Yuki Bisaiji, Yuki Haba, Kazuhiro Umemoto, Takao Fukuma
Abstract In this paper, a control strategy to switch NSR (NOx storage and reduction) function from standard DeNOx by rich combustion to DiAir (Diesel NOx After-treatment by Adsorbed Intermediate Reductants) and additional advantages to use HCI (Hydrocarbon Injector) during desulfation were introduced. Investigations under a transient cycle suggest that NOx conversion with DiAir is strongly affected by preliminary NOx storage condition in the NSR catalyst. To avoid NOx breakthrough just after starting HC dosing for DiAir, a rich operation to reduce stored NOx was shown to be important and high NOx conversion could be maintained using this control strategy under a transient cycle. Furthermore, by combining HCI and in-cylinder post injection, usage of rich condition for NSR DeSOx can be expand to wider engine speed and load area.
2014-10-13
Journal Article
2014-01-2627
Mitsuaki Ohtomo, Hiroshi Miyagawa, Makoto Koike, Nozomi Yokoo, Koichi Nakata
Abstract This paper presents the effects of a lubricant oil droplet on the start of combustion of a fuel-air mixture. Lubricant oil is thought to be a major source of low-speed pre-ignition in highly boosted spark ignition engines. However, the phenomenon has not yet been fully understood because its unpredictability and the complexity of the mixture in the engine cylinder make analysis difficult. In this study, a single oil droplet in a combustion cylinder was considered as a means of simplifying the phenomenon. The conditions under which a single oil droplet ignites earlier than the fuel-air mixture were investigated. Tests were conducted by using a rapid compression expansion machine. A single oil droplet was introduced into the cylinder through an injector developed for this study. The ignition and the flame propagation were observed through an optical window, using a high-speed video camera.
2014-10-13
Journal Article
2014-01-2767
Arij Ben Amara, Bertrand Lecointe, Nicolas Jeuland, Takuya Takahashi, Yutaka IIda, Hiromichi Hashimoto, Julien Bouilly
The stability of Diesel/Biodiesel blends can play an important role in deposits formation inside the fuel injection system (FIS). The impact of the stability of FAME/Diesel fuel blends on lacquer deposits formation and on the behavior and reliability of the FIS was investigated using blends of Rapeseed and Soybean methyl esters (RME, SME) and conventional Diesel fuel (volume fractions of RME and SME range from 0 to 20%v/v). Fuels were aged under accelerated conditions and tested on an injection test rig according to an operating cycle developed to provoke injector needle blocking. The soaking duration was found to affect injector fouling. A relationship between the injector fouling tendency and the fuel stability was established. Under current test condition, injectors fouling increased with fuel oxidation measured with Total-Acid-Number.
2014-10-13
Journal Article
2014-01-2785
Kosuke Fujimoto, Minoru Yamashita, Satoshi Hirano, Katsuyoshi Kato, Izumi Watanabe, Koki Ito
Abstract Gasoline engine downsizing combined with a turbocharger is one of the more effective approaches to improve fuel efficiency without sacrificing power performance. The benefit comes from lower pumping loss, lower mechanical friction due to ‘downsizing’ of the engine displacement and ‘down-speeding’ of the engine by using higher transmission gear ratios which is allowed by the higher engine torque at lower engine speeds. However abnormal combustion referred to as Low-Speed Pre-ignition (LSPI) is known to be able to occur in low-speed and high-torque conditions. It is a potential restriction to maximize the engine performance and its benefit, therefore prevention of LSPI is strongly desired for long-term durability of engine performance. According to recent technical reports, auto-ignition of an engine oil droplet in a combustion chamber is believed to be one of major contributing factors of LSPI and its formulations have a significant effect on LSPI frequency.
2014-04-01
Technical Paper
2014-01-1293
Gen Shibata, Hirooki Ushijima, Hideyuki Ogawa, Yushi Shibaike
Abstract When fuel is vaporized and mixed well with air in the cylinder of premixed diesel engines, the mixture auto-ignites in one burst resulting in strong combustion noise, and combustion noise reduction is necessary to achieve high load premixed diesel engine operation. In this paper, an engine noise analysis was conducted by engine tests and simulations. The engine employed in the experiments was a supercharged single cylinder DI diesel engine with a high pressure common rail fuel injection system. The engine noise was sampled by two microphones and the sampled engine noise was averaged and analyzed by an FFT sound analyzer. The engine was equipped with a pressure transducer and the combustion noise was calculated from the power spectrum of the FFT analysis of the in-cylinder pressure wave data from the cross power spectrum of the sound pressure of the engine noise.
2014-04-01
Technical Paper
2014-01-1728
Toshihiro Aoyama, Hideaki Takahara, Shinya Kuwabara, Hideki Miyata, Makoto Nakayashiki, Shinji Kasuga
Abstract In response to global demands for environmental conservation, the automotive industry is placing greater focus on the development of fuel-efficient technologies to help reduce global CO2 emissions. With the aim of simultaneously improving fuel economy and driveability, TOYOTA has developed a new continuously variable transmission (CVT) vehicles in North America equipped with a 1.8-liter engine [1]. This new CVT features various technologies for improving fuel economy, including: the world's first coaxial 2-discharge port oil pump system, wider ratio coverage, a flex start system, low-viscosity CVT fluid, and a higher final gear ratio. This paper outlines the configuration, characteristics, performance, and new technologies of this CVT.
2014-04-01
Technical Paper
2014-01-1730
Masahiro Tawara, Andrew Sata, Naoyuki Sakamoto, Toshiya Oishi, Shun Minaki, Motonori Kimura, Koshiro Kosaka
Abstract Toyota Motor Corporation developed a continuously variable transmission (CVT), unit K313, to satisfy the rising demand for improved fuel economy. This transmission was installed in the North American market Corolla for the 2014 model year. In this market, the driveability demands for automatic transmissions (AT) are very high. Additionally, the market is dominated by conventional AT with fixed gear ratios, leaving CVTs in the minority. In order to increase the volume and acceptance of CVTs in North America, excellent driveability had to be ensured. The key driveability advantage of CVTs is the ability to change gear ratio continuously without engaging or disengaging clutches. This allows for smooth driving without any shocks or gaps in drive force; however, it can also feel strange to drivers of conventional AT.
2014-04-01
Technical Paper
2014-01-1604
Yoshinori Otsuki, Kenji Takeda, Kazuhiko Haruta, Nobuhisa Mori
Abstract The particle number (PN) emission regulation has been implemented since 2011 in Europe. PN measurement procedure defined in ECE regulation No. 83 requires detecting only solid particles by eliminating volatile particles, the concentrations of which are highly influenced by dilution conditions, using a volatile particle remover (VPR). To measure PN concentration after the VPR, a particle number counter (PNC) which has detection threshold at a particle size of 23 nm is used, because most solid particles generated by automotive engines are considered to be larger than 23 nm. On the other hand, several studies have reported the existence of solid and volatile particles smaller than 23 nm in engine exhaust. This paper describes investigation into a measurement method for ultrafine PNCs with thresholds of below 23 nm and evaluation of the VPR performance for the particles in this size range.
2014-04-01
Technical Paper
2014-01-0679
Takashi Kubokura, Takahiro Uno, Nic Evans, Hiroshi Kuroda, Fuminori Shindo, Satoshi Nagahama
Abstract As the demand for improved fuel economy increases and new CO2 regulations have been issued, aerodynamic drag reduction has become more critical. One of the important factors to consider is cooling drag. One way to reduce cooling drag is to decrease the air flow volume through the front grille, but this has an undesirable impact on cooling performance as well as component heat load in the under-hood area. For this reason, cooling drag reduction methods while keeping reliability, cooling performance and component heat management were investigated in this study. At first, air flow volume reduction at high speed was studied, where aerodynamic drag has the greatest influence. For vehicles sold in the USA, cooling specification tends to be determined based on low speed, while towing or driving up mountain roads, and therefore, there may be extra cooling capacity under high speed conditions.
2014-04-01
Technical Paper
2014-01-1048
Hisao Hayashi, Masahiko Ishii
Abstract Waterborne 3-wet paint systems have been developed to reduce volatile organic compounds (VOCs) and CO2 on vehicle painting lines. However, only a small number of vehicles have adopted this system due to limitations in appearance quality (smoothness and gloss). Therefore, a waterborne 3-wet paint system with appearance quality equivalent to a conventional 3-coat 2-bake (3C2B) paint system is under development. This paper describes research for improving appearance quality. After analyzing the unevenness surface formation mechanism of a paint film, this was achieved by adopting base resins with a low glass transition point (Tg) to promote leveling, and reducing the melamine content of the paint to minimize contraction during baking.
2014-04-01
Technical Paper
2014-01-0057
Akihito Yamamoto, Haruhiko Sugai, Ryo Kanda, Shuuichi Buma
Abstract This paper reports the results of a study into a preview control that uses the displacement of the road surface in front of the vehicle to improve for front and rear actuator responsiveness delays, as well as delays due to calculation, communication, and the like. This study also examined the effect of a preview control using the eActive3 electric active suspension system, which is capable of controlling the roll, pitch, and warp modes of vehicle motion.
2014-04-01
Technical Paper
2014-01-0172
Edgar Yoshio Morales Teraoka, Shin Tanaka, Tsutomu Mochida
Abstract We develop a simulation tool which reproduces lane departure crashes for the purpose of estimating potential benefits of Lane Departure Warning (LDW) systems in the American traffic environment. Tools that allow a fast evaluation of active safety systems are useful to make better systems, more effective in the real world; however accuracy of the results is always an issue. Our proposed approach is based on developing a simulation tool that reproduces lane departure crashes, then adding the effect of the LDW to compare the cases with and without the safety system, and finally comparing the results of different settings of the safety system. Here, the accurate reproduction of the relevant crashes determines the reliability of the results. In this paper, we present the reproduction of the lane departure crashes occurred in American roads in one year, by using data distributions obtained from retrospective crash databases.
2014-04-01
Technical Paper
2014-01-0441
Takahiro Adachi, Takashi Yonekawa, Yoshitaka Fuwamoto, Shoji Ito, Katsuhiko Iwazaki, Sueharu Nagiri
Abstract The driving simulator (DS) developed by Toyota Motor Corporation simulates acceleration using translational (XY direction) and tilting motions. However, the driver of the DS may perceive a feeling of rotation generated by the tilting motion, which is not generated in an actual vehicle. If the driver perceives rotation, a vestibulo-ocular reflex (VOR) is generated that results in an unnecessary correction in the driver's gaze. This generates a conflict between the vestibular and visual sensations of the driver and causes motion sickness. Although such motion sickness can be alleviated by reducing the tilting motion of the DS, this has the effect of increasing the amount of XY motion, which has a limited range. Therefore, it is desirable to limit the reduction in the tilting motion of the DS to the specific timing and amount required to alleviate motion sickness. However, the timing and extent of the VOR has yet to be accurately identified.
2014-04-01
Technical Paper
2014-01-1192
Tetsu Yamada, Shouji Adachi, Koichi Nakata, Takashi Kurauchi, Isao Takagi
From the time the first Hybrid Vehicle (HV) was launched, 17 years have past, and HV vehicles have boosted the global CO2 reduction trend. In order to maximize their merit, many HV engines focused on the best fuel consumption value namely thermal efficiency. This was because HV systems can control the operating area of engine and get merit. However, considering climate change and energy issues, it is important to focus conventional vehicle as well as HV vehicle progress. The Atkinson cycle with a high compression ratio is the typical approach that HV engines use to enhance thermal efficiency. However, the drawback of the high compression ratio is a reduction of engine torque. Thermal efficiency at low load areas is relatively more important with conventional engines than with HV engines and how to overcome these issues is significantly important with conventional engines.
2014-04-01
Journal Article
2014-01-0655
Akihito Hosoi, Atsushi Morita, Naoto Suzuki
At the engine restart, when the temperature of the catalytic converter is low, additional fuel consumption would be required to warm up the catalyst for controlling exhaust emission.The aim of this study is to find a thermally optimal way to reduce fuel consumption for the catalyst warm up at the engine restart, by improving the thermal retention of the catalytic converter in the cool down process after the previous trip. To make analysis of the thermal flow around the catalytic converter, a 2-D thermal flow model was constructed using the thermal network method. This model simulates the following processes: 1) heat conduction between the substrate and the stainless steel case, 2) heat convection between the stainless steel case and the ambient air, 3) heat convection between the substrate and the gas inside the substrate, 4) heat generation due to chemical reactions.
2014-04-01
Journal Article
2014-01-1210
Shinichi Mitani, Susumu Hashimoto, Hiroshi Nomura, Rio Shimizu, Mutsumi Kanda
Abstract The advantages of gasoline direct-injection are intake air cooling due to fuel vaporization which reduces knocking, additional degrees of freedom in designing a stratified injection mixture, and capability for retarded ignition timing which shortens catalyst light-off time. Stratified mixture combustion designs often require complicated piston shapes which disturb the fluid flow in the cylinder, leading to power reduction, especially in turbocharged gasoline direct-injection engines. Our research replaced the conventional shell-type shallow cavity piston with a dog dish-type curved piston that includes a small lip to facilitate stratification and minimize flow disturbance. As a result, stable stratified combustion and increased power were both achieved.
2014-04-01
Journal Article
2014-01-1218
Yoshihiro Okada, Shigeki Miyashita, Yoshihiro Izumi, Yutaka Hayakawa
Abstract This paper analyzes low-speed pre-ignition (LSPI), a sudden pre-ignition phenomenon that occurs in downsized boosted gasoline engines in low engine speed high-load operation regions. This research visualized the in-cylinder state before the start of LSPI combustion and observed the behavior of particles, which are thought to be the ignition source. The research also analyzed pre-ignition by injecting deposit flakes and other combustible particulate substances into the combustion chamber. The analysis found that these particles require at least two combustion cycles to reach a glowing state that forms an ignition source. As a result, deposits peeling from combustion chamber walls were identified as a new mechanism causing pre-ignition. Additionally, results also suggested that the well-known phenomenon in which the LSPI frequency rises in accordance with greater oil dilution may also be explained by an increase in deposit generation.
2014-04-01
Journal Article
2014-01-1200
Randall D. Partridge, Walter Weissman, Takanori Ueda, Yoshihiro Iwashita, Paul Johnson, George Kellogg
ExxonMobil, Corning and Toyota have collaborated on an Onboard Separation System (OBS) to improve gasoline engine efficiency and performance. OBS is a membrane based process that separates gasoline into higher and lower octane fractions, allowing optimal use of fuel components based on engine requirements. The novel polymer-ceramic composite monolith membrane has been demonstrated to be stable to E10 gasoline, while typically providing 20% yield of ∼100 RON product when using RUL 92 RON gasoline. The OBS system makes use of wasted exhaust energy to effect the fuel separation and provides a simple and reliable means for managing the separated fuels that has been demonstrated using several generations of dual fuel test vehicles. Potential applications include downsizing to increase fuel economy by ∼10% while maintaining performance, and with turbocharging to improve knock resistance.
2014-04-01
Journal Article
2014-01-1662
Akihiro Honda, Motoichi Murakami, Yuichiro Kimura, Katsuhiro Ashihara, Shinichi Kato, Yuichiro Kajiki
Fuel efficiency improvement measures are focusing on both cold and hot conditions to help reduce CO2 emissions. Recent technological trends for improving fuel economy such as hybrid vehicles (HVs), engine start and stop systems, and variable valve systems feature expanded use of low-temperature engine operation regions. Under cold conditions (oil temperature: approximately 30°C), fuel consumption is roughly 20% greater than under hot conditions (80°C). The main cause of the increased friction under cold conditions is increased oil viscosity. This research used the motoring slipping method to measure the effect of an improved crankshaft bearing, which accounts for a high proportion of friction under cold conditions. First, the effect of clearance was investigated. Although increasing the clearance helped to decrease friction due to the oil wedge effect, greater oil leakage reduced the oil film temperature increase generated by the friction.
2014-04-01
Journal Article
2014-01-0598
Kenji Tadakuma, Takashi Sugiyama, Kazuhiro Maeda, Masashi Iyota, Masahiro Ohta, Yoshinao Komatsu
A new wind tunnel was developed and adopted by Toyota Motor Corporation in March 2013. This wind tunnel is equipped with a 5-belt rolling road system with a platform balance that enables the flow simulation under the floor and around the tires in on-road conditions. It also minimizes the characteristic pulsation that occurs in wind tunnels to enable the evaluation of unsteady aerodynamic performance aspects. This paper describes the technology developed for this new wind tunnel and its performance verification results. In addition, after verifying the stand-alone performance of the wind tunnel, a vehicle was placed in the tunnel to verify the utility of the wind tunnel performance. Tests simulated flow fields around the vehicle in on-road conditions and confirmed that the wind tunnel is capable of evaluating unsteady flows.
2013-10-14
Technical Paper
2013-01-2500
Norihiko Sumi, Satoshi Hirano, Kosuke Fujimoto, Takeshi Nakajima, Yosuke Kudo, Koki Ito
Due to increasing demands for further CO2 reduction and tighter exhaust emissions regulations, automakers are increasingly downsizing turbo-charged diesel engines by raising specific power, or adopting low-pressure loop exhaust gas recirculation (LPL-EGR) systems to improve the EGR rate. However, adopting a higher boost pressure to increase the specific power, or introducing hot exhaust gas before the turbocharger compressor with the LPL-EGR system creates higher gas temperatures in the compressor, which results in soot-containing deposits derived from the engine oil in the compressor. This phenomenon causes significant deterioration of turbocharger efficiency. Therefore, countermeasures such as restricting boost pressure or limiting EGR usage in the operational map are necessary to prevent engine performance deterioration. Increasing the gas temperature in the compressor while preventing deposit formation should enable further improvements in fuel consumption and engine power.
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