森吉 泰生

In this research, simulation and experimental investigation of H2 emission formation and its influence during the post-oxidation phenomenon were conducted on a turbo-charged spark ignition engine. During the post-oxidation phenomenon phase, rich air-fuel ratio (A/F) is used inside the cylinder. This rich excursion gives rise to the production of H2 emission by various reactions inside the cylinder. It is expected that the generation of this H2 emission can play a key role in the actuation of the post-oxidation and its reaction rate if enough temperature and mixing strength are attained. It is predicted that when rich combustion inside the cylinder will take place, more carbon monoxide (CO)/ Total Hydro Carbon (THC)/ Hydrogen (H2) contents will arrive in the exhaust manifold. This H2 content facilitates in the production of OH radical which contributes to the post-oxidation reaction and in-turn can aid towards increasing the enthalpy. Through simulations, it was also investigated that higher H2 levels influences the ignition delay of the post-oxidation reaction significantly. In addition, the experimental investigation of H2 formation with different overlap and spatial distribution were also analyzed. It was noted that the H2 formation always came to be higher at high overlap (90 deg. overlap) due to significant scavenging in the exhaust manifold that leads in-cylinder mixture rich. Also, the H2 concentration firstly increases when we move from exhaust port to Turbocharger (TC) upstream. This is due to the inhomogeneity that occurred between exhaust port to TC upstream. Furthermore, as we move from TC upstream to TC downstream, the H2 level decreases due to the consumptions of H2 in post-oxidation reaction.

To increase thermal efficiency of internal combustion engines, dilution combustion systems, such as lean burn and exhaust gas recirculation systems, have been developed. These systems require spark-ignition coils generating large discharge current and discharge energy to achieve stable ignition under diluted mixture conditions. Several studies have clarified that larger discharge current increases spark-channel stretch and decreases the possibility of spark channel blow-off and misfire. However, these investigations do not mention the effect of larger discharge current and energy on the initial combustion period. The purpose of this study was to investigate the relation among dilution ratio, initial-combustion period, and coil specifications to clarify the control factor of the dilution limit. Four coils having different current profiles were evaluated under 2000 rpm and 6-bar net-indicated mean effective pressure under a diluted mixture condition through combustion-performance and in-cylinder optical-measurement tests on a single cylinder engine. The combustion-performance test results indicate a correlation between the dilution limit and initial combustion period. The in-cylinder optical-measurement test results indicate that the initial combustion period has a correlation with spark stretch before the 1st restrike and spark-stretch rate. These results also indicate that variation in the initial combustion period depends on the temporal flow velocity change during discharge and long initial-combustion-period cycles are caused at slow velocity during discharge.

Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors' previous study, lean burn limit could be extended slightly by low temperature plasma ignition while the power supply's performance with steep voltage rising with time (dV/dt), showed higher peak value of the rate of heat release and better indicated thermal efficiency. In this study, basic study of low temperature plasma ignition system was carried out to find out the reason of combustion enhancement. Moreover, the durability test of low temperature plasma plug was performed to check the wear resistance.

We developed an analytical method for the detection of nitric oxide (NO), nitrogen dioxides (NO ) and ozone (O ) simultaneously with high time resolution (1 s). The fast analytical method was applied for the observation at the Fuji mountain roadside at an altitude of 2300 m. We successfully observed the concentrations of NO and NO in emissions from each vehicle at a roadside, and the O concentration decreased due to the reaction with NO. Relative amounts of NO emissions and primary NO emission ratios of each vehicle driven on the road were estimated by the concentrations observed with high time resolution. 2 3 2 3 x 2

In this report, the effect of injection specification, such as droplet size, lengths of nozzle tip and spray angle, on the engine performance was investigated using a 1.2 L port fuel injection (PFI) four-cylinder gasoline engine. The experimental conditions were selected to cover the daily operating mode, including the cold start and catalyst heating process. The experiments were conducted by varying not only the injectors but also the injection timing which was shifted from the exhaust to intake stroke. The results were evaluated by the fuel consumption and exhaust gas emissions. When these tests were conducted on a production engine, a carefully designed tumble generator was installed at the intake port to enhance the intake air flow. As a result, the injection specifications showed a potential to obtain less fuel consumption and lower engine-out emissions was evaluated.

Cycle-to-cycle variation (CCV) of combustion in low load operation is a factor that may cause various problems in engine operation. Variable valve timing and variable ignition timing are commonly used as a means to reduce this variation. However, due to mountability and cost constraints, these methods are not feasible for use in motorcycle engines. Therefore, development of an engine with minimal CCV without utilizing complicated mechanisms or electronic control is required. CCV of combustion may be caused by fluctuations in in-cylinder flow, air-fuel mixture, temperature, residual gas and ignition energy. In this study, the relationship between CCV of combustion, in-cylinder flow fluctuation and air-fuel mixture fluctuation was the primary focus. In order to evaluate in-cylinder flow fluctuation, Time Resolved Particle Image Velocimetry (TR-PIV) technique was utilized. In addition, Planar Laser Induced Fluorescence (PLIF) technique was used to measure spatial distribution of the mixture. These two visualization techniques were used together to measure continuous combustion cycles. The fluctuation of net IMEP can be explained by the fluctuation of Turbulence Kinetic Energy (TKE) and fuel concentration. In most cycles, net IMEP was correlated with TKE. In the remaining cycles, net IMEP was correlated with fuel concentration. The contribution of each factor towards net IMEP is to be discussed. It has been also confirmed that TKE fluctuation is caused by fluctuation in the tumble vortex structure, as shown in the authors' previous study [2] [13].

Porous materials, which have large surface areas, have been used for heat storage. However, porous Si-SiC material, as heat storage medium to be applied to a turbocharged gasoline engine has not been investigated extensively. In this study, porous Si-SiC material was used in the upstream of the turbine as heat storage medium and a model was thereby developed for further study. Substrate surface area and substrate volume of Si-SiC were calculated for structure model calibration. Following these calculations and test results, the pressure loss and thermal model were validated. Results show that the weaken exhaust gas pulsation amplitude by porous Si-SiC leads to better turbine performance and BSFC in steady engine condition for a turbocharged gasoline engine. In addition, its transient operation response needs to be improved under transient engine conditions. Hence the possibility of improving the transient response is investigated with characteristics of porous Si-SiC material. It was observed that less time was required for the engine to reach the target torque in transient conditions.

The purpose of this paper is to find a way to extend the high load limit of homogeneous charge compression ignition (HCCI) combustion. A newly developed rapid compression and expansion machine (RCEM) was employed to reproduce the typical HCCI high load condition. The in-cylinder turbulence was created by the special piston which equipped with a flow guide plate. Meanwhile, the ambient temperature distribution in the cylinder was determined by the wall temperature controlling system which was controlled by the independent coolant passages. In addition, the numerical simulation by using large eddy method coupled with a detailed chemical reaction was conducted as well. The results show that HCCI mode is potential to be improved at high load condition in full consideration of in-cylinder temperature, flow, and turbulence.

本研究ではオイル添加剤の調整がLSPI発生頻度に与える影響を明確するため，Ca, Mg, Mo三種類の添加剤の組合せをベースに，各々の添加剤の量を2水準設定し，その組合せの計8種類の試作オイルを用意した．特にこれまでに報告例がない，IMEP 2.4MPaの超高負荷運転において，オイル添加剤がLSPI発生に与える影響を調査した．

ダウンサイジング過給エンジンの高負荷領域を拡大するため，低回転超高過給運転を試み，正味平均有効圧3MPaを1750rpmで達成した．また拡大した高負荷領域における燃費率を改善した．本研究のコンセプトと実験結果について述べる．

超高過給ダウンサイジングコンセプトを実現するため，低回転から高回転まで超高過給運転を可能とし，正のポンプ仕事を得ることでエンジン熱効率を改善することを狙って，システムの検討を行い，2段過給システムを試作した．検討内容と実験結果について報告する．

<p>Research on internal combustion engine using gaseous fuel is getting popular. In order to reduce exhaust gas emissions including CO₂, heavy oil is replaced by gas fuel, especially for ships and stationary generators. Demand of natural gas is rapidly increased due to the clean exhaust gas emissions and the price. Moreover, combustion study of hydrogen and ammonia is also getting active as both fuels can be made from green energy. In this article, combustion technologies using natural gas are mainly focused, such as abnormal combustion, ignition method, methane slip and combustion analogy. Many research papers are reviewed and discussion from both experimental and numerical viewpoints are briefly described.</p>

<p>It is required to reduce both the friction and lubricant oil consumption (LOC) in order to reduce CO₂ in internal combustion engines. In addition, as the requirement to reduce particulate number (PN) may be realized by reducing LOC, the relationship between LOC and PN should be examined. Elucidation of the mechanism of LOC belongs to a basic and applied field and a common subject, however, only the LOC is measured by the weight method in steady conditions and the mechanism is not clarified so far. Thereby, the relationship between LOC and PN was measured in a wide operation area including transient conditions using a production engine in this study.</p>

In this research, the improvement of mixing and pulsation in exhaust manifold with a design and implementation of bypass adapter at exhaust port were deeply investigated. This in-turn can improve the post-oxidation phenomena and hence emissions and engine performance could be enhanced. This research investigation includes 1-D, 3-D simulations and experimental validation on a 4-cylinder turbocharged spark ignition (SI) engine. Firstly, the 1-D and 3-D simulation models were developed and calibrated with the experimental results. Then, the simulations were used for the detailed investigation of mixing and pulsation in exhaust manifold with and without bypass adapter. Thereafter, experimental test for the post-oxidation were conducted with and without consideration of the bypass adapter and results were compared. From the simulation and experimental results, it was proven that by using bypass adapter at the exhaust port, the mixing of exhaust gas species was observed to be significantly improved to some extent. Also, the unbalance between exhaust port and turbocharger upstream gas species were reduced. This also reduced the exhaust gas pulsation. By the improvement of mixing between scavenged O and unburned gas species, the post-oxidation reaction was also noted to have improved and consequently the emissions and turbo-speed were found to be better that led to an improved IMEP and thermal efficiency of the engine. 2

The stochastic pre-ignition phenomenon plays a vital role to limit the further increasing BMEP for natural gas engines. In this study, the pre-ignition propensities were examined in a highly boosted premixed natural gas engine by various engine loads and air/fuel ratios, as well as different methane number (MN) altered by hydrogen addition. A proper pre-ignition evaluation method was proposed referring to intake temperature. Moreover, the limits of in-cylinder temperature and pressure for the onset of pre-ignition were estimated. The results show that both higher IMEP and richer mixture conditions readily lead to pre-ignition. The significant increases of pre-ignition frequency and heavy-knocking pre-ignition cycle present with lowering MN.

In this research, a novel methodology for the post-oxidation in a turbocharged spark ignition (SI) engine is proposed and investigated that can improve the emissions along with the reduction in turbo-lag. In this research, both simulation and experimental activities are performed. The 1-D simulation model was used for the identification of efficient scavenging. Thereafter, experimental validation tests for modeling and post oxidation were conducted on a 4-cylinder turbocharged SI engine. From the results, it was revealed that efficient scavenging and post-oxidation can be obtained at lower speed and higher load. The enthalpy in exhaust manifold increased due to the post-oxidation reaction which in turn increased the temperature and pressure of the exhaust gases and hence emissions reduced. Also, due to the increased enthalpy at turbine upstream, the turbocharger speed increased and as a consequence, reduction in the turbo-lag was observed. It was also noted that the post-oxidation is limited at higher load and overlap in an inline 4-cylinder engine due to the strong scavenging which increased the cooling effect in in-cylinder and exhaust manifold due to excess air.

Effects of measurement method, coolant temperature and fuel composition on soot emissions were examined by engine experiments. By reducing the pressure fluctuation in the sampling line, the measured soot emissions with better stability and reproducibility could be obtained. With lower coolant temperatures, larger soot emissions were yielded at much advanced fuel injection timings. Compared to gasoline, soot emissions with a blend fuel of normal heptane, isooctane and toluene were significantly decreased, suggesting the amounts of aromatic components (toluene or others) should be increased to obtain a representative fuel for the predictive model of particulate matter in SIDI engines.

Resistive particulate matter sensor (PMS) is a promising solution for the diagnosis of diesel/gasoline particulate filter (DPF/GPF) functionality. Frequently triggered regeneration of their sensing element, for cleaning the soot dendrites deposited on the surface, leads to experience high temperature and thermal stress and pose high risk of developing cracks in the electrodes or sensing substrate. A semiconductor with a dopant concentration of 100 ppm~10000 ppm is applied as a sensing element for PMS self-diagnosis. Upon cooling at air, the polarization doped-insulating layer in a resistive PMS starts to resume the electrical conductivity in the wake of experiencing high regeneration temperature, through the electron and hole directional mobility. At a temperature slightly lower than carbon equilibrium temperature of 600°C, the charge carriers' migration rate reaches the maximum value and then steps down to near zero with cooling of the sensing element due to the carrier thermal movement and polarization. On the other hand, during percolation/quiescent process, the charged soot dendrites appear to be anchored between the gap of electrodes, not well interconnected but rather standing independent of each other. No conductive path forms between electrodes, but the mobility of charge carrier between carbonaceous particulate matter and sensing element suddenly increases and then is kept constant (saturation drift current occurrence) until the first soot conductive path is formed. This article tries to figure out electron transferring pathways from amorphous carbon to the insulating layer doped by a defined dopant and to shed some light on the mechanism of choking phenomenon.

<p>The "Innovative Combustion Technology" program, a national project is established under the Cabinet Office, Government of Japan as a part of the" Cross-ministerial Strategic Innovation Promotion Program (SIP)". The "Gasoline Combustion Team" is one of teams of the "Innovative Combustion Technology" program.</p><p>The "Gasoline Combustion Team" is comprised of Keio University as a Leader university and 29 universities as a Cluster university. Upon agreement with the Japan Science and Technology Agency (JST), we have been conducting the research on the "Super-Lean Burn for Gasoline Engines" with a support of the Research Association of Automotive Internal Combustion Engines (AICE) under the strong industry, academia and government collaboration.</p><p>This paper introduces both scientific and technological approaches to innovative combustion technologies to realize the "Super- Lean Low Temperature Combustion", targeting a thermal efficiency of 50%.</p>

<p>The prechamber combustion characteristics were studied using a rapid compression and expansion machine (RCEM) to improve the efficiency of cogeneration natural gas engines. The torch flames generated by a prechamber were used to investigate the effect that a prechamber has on the main combustion. In our previous study, we observed the correlation between the torch flame and the main flame (which is a so-called "prechamber combustion") as well as the knocking phenomena for various prechamber configurations. In this study, in order to investigate the effects of engine size on prechamber combustion characteristics, large size RCEM were developed.</p>

<p>The prechamber combustion characteristics were studied using a rapid compression and expansion machine (RCEM) to improve the efficiency of cogeneration natural gas engines. The torch flames generated by a prechamber were used to investigate the effect that a prechamber has on the main combustion. In our previous study, we observed the correlation between the torch flame and the main flame (which is a so-called "prechamber combustion") as well as the knocking phenomena for various prechamber configurations. In this study, we have investigated the effect of prechamber combustion on main chamber combustion characteristics using a constant volume combustion chamber.</p>

<p>Real driving conditions change because of road, traffic environments, weather and driver's characteristics. These changes cause differences between real driving and regulations. To improve the differences, a real driving emission (RDE) regulation has been introduced and implemented in Europe for diesel passenger vehicles. Similar regulation is expected to be introduced in Japan from 2022. Since environmental conditions as mentioned above vary real-driving test results, the reproducibility of experiments is low. In order to figure out the variation, it is necessary to carry out a large number of tests which take a lot of time and cost. On the other hand, a prediction method using simulation model can efficiently evaluate the emissions reflecting various driving patterns and environmental conditions. In the authors' previous study, prediction methods of NOx emission were developed and verified using a diesel passenger car. However, the verification was carried out under equivalent environment conditions. In this study, the accuracy of measured and predicted data was confirmed by considering the environmental factor in the prediction model. In case of considering the environmental factor, the predictability of model was increased by comparing the previous model.</p>

直噴ガソリンエンジンのすす生成モデルの構築のための基礎データとして、エンジン実験におけるすす測定の安定化を試みた。測定位置や圧力変動低減のためチャンバーの有無などを変化させることで、すす排出挙動の異なる条件であってもすすの排出量と粒子数および粒径分布を安定かつ再現性よく測定することが可能となった。

導入が予定されているRDE試験は排出ガス規制である一方、同時に燃費の測定も可能である。その際に得られる燃費は、モード燃費や実燃費と比較してどのような水準となると見込まれるのか、直噴ターボガソリン車を用いてRDE試験法に準拠したコースを走行して比較を行い、とくに実燃費との関係について考察した。

ディーゼル機関の後燃え要因である噴霧先端の過濃混合気塊生成抑制のため，主燃料分割噴射の効果を調査した．分割によりメイン噴射量が低減しキャビティ内の過濃混合気塊生成が抑制されること，及びアフター噴射燃料は高温場で余剰空気と共に急速燃焼することで後燃えが低減し，熱効率向上要因となっていることが判明した．

火花点火機関の高希釈高過給化により，点火環境は厳しくなる一方である．スパークプラグでの放電路挙動と予混合気への点火性能の関係を明らかにすることが重要である．本研究では定容燃焼容器を用い，希釈流動場における放電と着火性の関係を調査した．各放電パラメータの着火性への寄与度は，流動強度により差異が確認された．

<p>Cycle-to-cycle variation (CCV) of in-cylinder flow occurs in internal combustion engines. It is necessary to analyze CCV of flow to separate averaged-flow (as low frequency / low wave number) from turbulence (as high frequency / high wave number), because an averaged flow varies from cycle to cycle. Two averaging methods are used for the extraction of mean component from instantaneous flow. One is temporal-averaging method, the other is spatial-averaging method. In the temporal -averaging method, a fluctuation of flow is captured at fixed point in Eulerian, turbulence is regarded as the high frequency component, and it is removed by a low pass filtering. In the spatial-averaging method, the turbulence in spatial arrangement of flow velocity is directly averaged by using vortex scale as a threshold (e.g. Moving-averaging filter and Gaussian-averaging filter). However, the temporal-averaging and the spatial-averaging have completely different characteristics. Therefore, it is necessary to clarify the difference of filtering characteristics in each averaging filter. In this study, comparisons of averaged flow patterns of temporal-average and spatial-average are carried out. Moreover, variable sized spatial filter which is based on Taylor's frozen-turbulence hypothesis is proposed. As a result, variable sized filtering is found close to the filter characteristic of the time average method.</p>

実路走行時におけるNOx排出量を予測するシミュレーションについて，著者らは既研究で，NOx低減触媒を装着していない車両で実路走行時の予測を可能とした．本研究では， NOx吸蔵還元触媒を装着した車両を対象に，簡易な予測モデルを検討し，実路走行時の排出量と比較・検証を行った.

The purpose of this paper is to find a way to extend the high load limit of homogeneous charge compression ignition (HCCI) combustion. This paper presents the effect of in-cylinder flow and stratified mixture on HCCI combustion by experiments and three-dimensional computer fluid dynamics coupled with a detailed chemical reaction calculation. The first study was conducted using a rapid compression and expansion machine (RCEM) equipped with a flow generation plate to create in-cylinder turbulent flow and with a control unit of in-cylinder wall temperature to create in-cylinder temperature distribution. The study assesses the effect of the turbulent flow and the temperature distribution on HCCI combustion. In the second study, the numerical simulation of HCCI combustion was conducted using large eddy simulation coupled with a detailed chemical reaction calculation. The study analyzes the interaction between in-cylinder turbulent flow and mixture distribution and HCCI combustion. The result shows that turbulent flow effects a change in the distribution of chemical species which is a trigger of combustion initiation.

<p>DI Gasoline engine tends to increase the particulate mass concentration in the case of cold start, warming-up process and high load condition. In this study, PM emission was investigated from cold start to warming-up stage. The engine coolant temperature is set to 8°C, 30°C and 80°C, and start of fuel injection is changed from -320 deg.ATDC and -90 deg.ATDC. The excess air ratio, the load (gross indicated mean effective pressure, Gross IMEP) and the combustion phase (CA 50) was adjusted to 1.0 and 0.7 MPa, ≈ 9 deg. ATDC, respectively. The fuel injection pressure was kept constant at 10 MPa. As a result, when the coolant temperature was changed to 8°C, 30°C and 80°C, it was found that the soot at the coolant temperature of 8°C increased. In addition, it was found that soot was less affected by coolant temperature from -300 deg. ATDC to -120 deg. ATDC. Soot tends to increase at the injection condition -320 deg. ATDC and -90 deg. ATDC where the piston top surface is approaching the injector. The soot increased because fuel adhered to the piston top surface and pool combustion occurred. Also at -90 deg.ATDC, soot formation from the rich region due to mixing failure is considered to be an influencing factor.</p>

今後乗用車に導入される可能性があるパワートレイン関連の新技術を導入した場合のWLTC走行時の燃費改善効果を予測するために，燃費シミュレーションツールに新たなモデルを導入し，その予測精度について実機を用いて検証を行った．次いで，このモード走行燃費シミュレーションコードを使って，各新技術の燃費改善効果を評価した．

火炎伝播の過程を観察する手法としてシュリーレン法が広く知られている．しかし火花放電による着火の場合，プラズマ形成や予熱による密度変化の影響で初期火炎の形状や大きさが判別できない．そこで本稿では可視域高速度カメラと赤外高速度カメラを用い，放電路と初期火炎の形成の様子を捉えることを試みた．

<p>To increase thermal efficiency of internal combustion engine, lean burn and EGR (Exhaust Gas Recirculation) system have been developed with spark ignition coils generating larger discharge current and discharge energy than current mass production coils. Several researches clarified that larger discharge current increases discharge channel extension and decreases possibility of discharge channel blow-off and possibility of misfire. However, these investigations don't mentioned effect of larger discharge current and energy on air-fuel ratio and combustion period. Then purpose of this research is to investigate relation among air-fuel ratio, combustion period and coil specification in order to clarify control factor of air-fuel ratio of lean burn. In this study, five coils having different current profiles were evaluated under 2000 rpm and 0.6 MPa NMEP (Net indicated Mean Effective Pressure) at lean mixture condition by combustion test and in-cylinder optical measurement test with research single cylinder engine. The combustion test results showed a correlation between lean limit air-fuel ratio and initial combustion period. Moreover, optical measurement test showed that initial combustion period has a correlation with discharge energy before 1st restrike and discharge channel extension rate and variation of initial combustion period under stable control condition doesn't depend on discharge current.</p>

<p>Cycle-to-cycle variation (CCV) of combustion is an important issue because it affects emissions and drivability. Improvement of CCV of combustion has been carried out using electronic controls (e.g. ignition timing, fuel injection and variable valve timing) in motor vehicle's engines. However, electronic devices are hardly used for motorcycle's engines because of limited space and cost. Therefore, the engine performance itself must be improved to reduce CCV of combustion in motorcycle. Though CCV of combustion is caused by CCV of in-cylinder flow pattern, fuel distribution, temperature and residual gas, and ignition energy, it is difficult to measure and analyze these factors. In this study, the simultaneous measurement of high-speed PIV and direct photographing of flame propagation was carried out. CCV of in-cylinder flow was evaluated as temporally-averaged flow that was obtained by instantaneous flow using low-pass filtering and cut-off frequency. As a result, in-cylinder temporally-averaged flow pattern fluctuated between individual cycles. Especially, the flow pattern on the surface of piston at BDC was different between the highest and the lowest cycle in IMEP. This difference is considered to be due to the location offset of tumble flow. Also the fluctuation of turbulence kinetic energy (TKE) is caused by tumble flow offset. TKE distribution near the spark plug at ignition timing affected the direction and speed of flame propagation.</p>

大気環境のさらなる改善のためにディーゼルエンジン排出ガスからの大幅なNOx低減が求められる中、弊社は平成28年排出ガス規制に適応したNOxの還元剤として軽油を用いる尿素フリーの後処理システム（DPR-II）を実用化した。本システムの排出ガス低減技術を発表する。

ディーゼル機関の後燃え低減による熱効率向上を目指し，市販のディーゼル機関の燃焼を紫外自発光撮影手法により可視化することで，後燃えの熱発生領域を調査した．三次元数値計算結果と共に考察した結果，後燃え期間中の熱発生は，噴霧火炎先端に形成された過濃混合気が滞留し，その外周部で発生している．

車両燃費シミュレーションではトランスミッション等のサブシステムをモデル化する必要がある．本研究は，実車での計測により車両燃費シミュレーションに必要なトランスミッション等のモデルを簡易に構築する手法を検討した．さらに，本シミュレーションを活用してタイヤ性能の違いが燃費に及ぼす影響を定量的に評価した．

<p>It is required to examine the characteristics of turbochargers for automobiles using one-dimensional simulation from the viewpoint of estimating total engine performance. In this study, a mathematical model to predict mechanical loss generated in a turbocharger is proposed. Friction works generated in a journal bearing and a thrust bearing are modeled, separately. As for the calculation of the friction work with the thrust bearing, the thrust force is calculated from the fluid force which is formulated analytically and calculated numerically based on one-dimensional flow taking account of relevant boundary conditions. According to the developed model, the friction work generated in a journal bearing is larger than that in a thrust bearing. Difference of thrust force and flow rate of oil has less impact on the friction works in a turbocharger. Finally, calculated total friction work based on the model proposed in the present study is compared with that obtained from the oil temperature method.</p>