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... simulation based iterative method was used to select the optimal intake valve timing along with careful matching of the turbocharger since the turbocharger matching and the intake valve timing affect each other. The system configuration is shown in Figure 3. DUAL-STAGE TURBOCHARGER WITH VGT -In a conventional dual-stage turbocharging system with fixed geometry turbines at both high and low pressure stage, it is desirable to have a small high pressure turbocharger in order to improve system transient response to sudden changes in speed and load [14]. ...

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Citations

... The VGT systems are also considered to be a key enabler in the EGR system for "heavy-duty (HD)" diesel engines [77]. The main problems associated with the noise level have been mitigated by a combination of improved mechanical, technological innovations, higher injection pressure, and multiple injections [78]. Zheng et al. [79] found that the expansion ratio, pressure ratio, intercooler, and turbine bypass mainly affected engine efficiency, pumping loss, and boost pressure. ...
... One obvious benefit is the high intake manifold pressures and the corresponding BMEP, the prerequisite for engine downsizing and down-speeding and lessening pumping losses [86]. Other advantages are that the transient performance is improved because a smaller turbocharger is selected as a high-pressure turbocharger [78], and the two turbochargers can cooperate under low load [87]. The disadvantage of this type is the turbo lag, especially large turbochargers, which take time to spool up and provide a useful boost. ...
... The hybrid boosting system with the VGT shows the best performance in both steady-state and transient conditions and fuel economy. The electrical compressor hybrid system demonstrates excellent performance under steady-state conditions but poor performance due to insufficient electrical power in transient conditions [78]. Figure 6 shows the comparison between various boosting systems and engine baseline in terms of engine thermal efficiency. ...
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Improving thermal efficiency and reducing carbon emissions are the permanent themes for internal combustion (IC) engines. In the past decades, various advanced strategies have been proposed to achieve higher efficiency and cleaner combustion with the increasingly stringent fuel economy and emission regulations. This article reviews the recent progress in the improvement of thermal efficiency of IC engines and provides a comprehensive summary of the latest research on thermal efficiency from aspects of thermodynamic cycles, gas exchange systems, advanced combustion strategies, and thermal and energy management. Meanwhile, the remaining challenges in different modules are also discussed. It shows that with the development of advanced technologies, it is highly positive to achieve 55% and even over 60% in effective thermal efficiency for IC engines. However, different technologies such as hybrid thermal cycles, variable intake systems, extreme condition combustion (manifesting low temperature, high pressure, and lean burning), and effective thermal and energy management are suggested to be closely integrated into the whole powertrains with highly developed electrification and intelligence.
... For the automobile application, the turbocharging system was designed to increase the low-speed torque and broaden the steady operation range. Therefore, in order to achieve more torque output of engine and to maximize the boost pressure, the RTS system was employed and its highpressure turbocharger and low pressure one was operated in series mode [6][7][8][9]. Ralf Buchwald et al. [10] adopted two-stage turbocharging system in a 4-cylinders diesel engine with EGR (Exhaust Gas Recirculation) system. The results of their researches showed that, by using the RTS system, the engine could obtain much higher torque output in the lowspeed operation, while the boost pressure was steadily kept in a high level in medium-and high-speed operation conditions. ...
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The regulated two-stage (RTS) turbocharging system is considered to be one of most effective measures to meet the requirements of the higher power density and the higher speed of automobile and marine diesel engines. However, the turbocharger matching and boost pressure control becomes significantly complex due to the engine operating conditions changed frequently. The engine test bench was built up to investigate the effects of several control strategies on the dynamic performance of the diesel engine with the RTS system. For the transient state four different control strategies, the open-loop control, the conventional PID control, the variable-parameter PID control, and the fuzzy control were employed. The experimental results show that the designed fuzzy control strategy has the best dynamic performance and the stability for both the transient loading process with constant speed and the transient marine operating conditions. Under the transient loading process and constant speed, the response time of the fuzzy control strategy is 0.3s faster than that of the variable-parameter PID control, and 2.8s faster than that of the open-loop control strategy. Under the transient marine operating conditions, the response time of the fuzzy control strategy is reduced by 0.9s than that of the variable-parameter PID control, and 5.2s reduced than that of the open-loop control strategy.
... Generally, series two-stage turbocharger can provide higher overall isentropic efficiency, higher low-end torque, faster transient response and better thermal efficiency when compared with single-stage turbocharger [7,8,9]. A waste-gate turbocharger is widely accepted as the HP stage which limits boost pressure by bypassing turbine flow, and this allows using smaller HP-turbine to maximize low speed performance and to prevent choking and over-boosting compared to free floating turbocharger [10][11]. However, by replacing the fixed geometry turbines with a VGT which typically has larger flowing capacity as the vane opens, the bypass valve can be effectively eliminated as the boost can be controlled by adjusting the vane position of VGT. ...
... Today, the most common applications of two-stage series turbocharging are to be found in large trucks as well as industrial/marine engines operating in the medium-speed range. In a typical two-stage series turbo configuration, the first unit is the low-pressure (LP) fitted upstream of the (usually smaller) HP one, with an aftercooler and, possibly, an intercooler between the two compressors (Choi et al., 2006;Winkler and Ångström, 2008;Lee et al., 2009). The efficiency advantage of turbocharging compared to naturally aspirated operation is amplified in the case of the two-stage configuration, as the elevated boost pressure offers the ability for even greater fuel savings (higher degree of down-sizing, better mechanical efficiency, operation of the two-stage units at regions with higher efficiency) (Galindo et al., 2010), whereas the increased air-supply accommodates higher EGR rates. ...
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... An interesting proposition is represented by a two stage supercharging system, that may be of two main types: two serially connected turbochargers, or a mechanical supercharger coupled with a turbocharger [5][6][7][8][9][10]. In the last case, it is possible to drive the supercharger by means of an electric motor. ...
... Therefore, the total displacement must be reduced from 3.8 to 3.0 L, while delivering the same brake power of 510 HP (382 kW) at 7000 rpm, and the same maximum brake torque of 650 Nm at 2000 rpm. The last target implies that maximum brake mean effective pressure varies from less than 22 bar to more than 27, a quite challenging goal considering the current production engines [1][2][3][4][5][6][7][8][9][10]. ...
... Crank-angle-resolved engine models solve equations by resolving the crank angle and provide finer details on the progress of each variable within a combustion cycle. They range from multi-dimensional computational fluid dynamics (CFD) models [1][2][3][4][5] to zero-dimensional filling and emptying models [6][7][8][9] depending on the spatial resolution. These models are suitable for investigating physical phenomena that vary substantially within each combustion cycle. ...
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... Characterisation of internal combustion engine with a zerodimensional model could provide information on turbochargers and engine interaction. Lee et al. [16] analysed various two stage boosting technologies in a diesel engine under transient conditions. The complete vehicle model showed that the combination of a variable and a fixed geometry turbochargers was able to achieve best transient performance as shown in figure 1. Galindo et al. [17] investigated a two stage turbocharging system using a zero-dimensional model and it was found that lowering gas exhaust temperature and compressor efficiency could cause negative effects on powertrain thermal efficiency. ...
... Comparison of two stage boosting technologies in vehicle acceleration from 0 to 60 mph[16]. ...
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The adoption of two stage serial turbochargers in combination with internal combustion engines can improve the overall efficiency of powertrain systems. In conjunction with the increase of engine volumetric efficiency, two stage boosting technologies are capable of increasing torque and pedal response of small displacement engines. In two stage serial turbocharges, a high pressure (HP) and a low pressure (LP) turbocharger are connected by a series of ducts. The former can increase charge pressure for low air mass flow typical of low engine speed. The latter has a bigger size and can cooperate with higher mass flows. In serial configuration, turbochargers are packaged in a way that the exhaust gases access the LP turbine after exiting the HP turbine. On the induction side, fresh air is compressed sequentially by LP and HP compressors. By-pass valves and waste-gated turbines are often included in two stage boosting systems in order to regulate turbochargers operations. One-dimensional modelling approaches are considered for investigating the integration of boosting systems with internal combustion engines. In this scenario, turbocharger behaviour are input in the powertrain models through previously measured compressor and turbine maps in turbocharger gas stands. However, this procedure does not capture all the effects that occur on engine application such as heat transfer, friction and flow motion that influence the turbochargers operations. This is of particular importance for two stage serial turbochargers where the LP compressor may induce a swirling motion to the flow at the entry of the HP compressor. In addition, flow non-uniformities caused by bends between the two compressors can make the HP compressor perform differently. In this paper, a review of the available literature containing approaches to quantify the effects of heat transfer on turbocharger efficiency and the flow influence in the prediction of two stage serial turbochargers performance is explored.
... It is time consuming and more suitable for the second stage of turbocharging system design process. Another approach using a zero dimension engine model is proposed by Lee et al. [9]. This approach is also not convenient to study the influence of different component parameters on engine performance, since it also need compressor and turbine maps. ...
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As the result of increasingly strict emission regulations and demand of fuel reduction, current light and medium duty engines are being highly boosted with complex two-stage turbocharging systems. The purpose of this work is to investigate the influence of two-stage turbocharging system parameters on the engine performance and the optimization of these parameters. An analytical pre-design model of the series two-stage turbocharging system for an internal combustion engine was developed, which builds the relationship between total pressure ratio, total expansion ratio and other two-stage turbocharging system parameters. Considering total expansion ratio as a function of expansion ratio between HP and LP turbine, minimum total expansion ratio can be determined using this model. The ratio of total pressure ratio to total expansion ratio, engine brake thermal efficiency and total heat exchange of coolers are considered as the parameters for engine performance evaluation. Influence of two-stage turbocharging system parameters, such as efficiency of compressors and turbines, cooling water temperature, cooler efficiency, pressure loss of coolers, EGR rate and bypass gas rate of wastegate, etc., on engine performance was analyzed respectively. Results show that the performance of a two-stage turbocharging engine is impacted mainly by LP turbocharger efficiency, intercooler performance and air filter performance.
... It is time consuming and more suitable for the second stage of turbocharging system design process. Another approach using a zero dimension engine model is proposed by Lee et al. [9]. This approach is also not convenient to study the influence of different component parameters on engine performance, since it also need compressor and turbine maps. ...
Data
Full-text available
As the result of increasingly strict emission regulations and demand of fuel reduction, current light and medium duty engines are being highly boosted with complex two-stage turbocharging systems. The purpose of this work is to investigate the influence of two-stage turbocharging system parameters on the engine performance and the optimization of these parameters. An analytical pre-design model of the series two-stage turbocharging system for an internal combustion engine was developed, which builds the relationship between total pressure ratio, total expansion ratio and other two-stage turbocharging system parameters. Considering total expansion ratio as a function of expansion ratio between HP and LP turbine, minimum total expansion ratio can be determined using this model. The ratio of total pressure ratio to total expansion ratio, engine brake thermal efficiency and total heat exchange of coolers are considered as the parameters for engine performance evaluation. Influence of two-stage turbocharging system parameters, such as efficiency of compressors and turbines, cooling water temperature, cooler efficiency, pressure loss of coolers, EGR rate and bypass gas rate of wastegate, etc., on engine performance was analyzed respectively. Results show that the performance of a two-stage turbocharging engine is impacted mainly by LP turbocharger efficiency, intercooler performance and air filter performance. INTRODUCTION Downsizing the ICE by turbocharging technology is one of the most cost-effective technologies to improve the fuel efficiency and reduce CO 2 and NO X emissions of internal