Sequential Turbocharging System Research Articles

Discussion on the application of sequential turbocharging technology on trawlers

To improve the performance needs of trawlers under the varying load and speed conditions of free-running and trawling operations, this article employs sequential turbocharging technology. By fitting the experimental curves of basic turbocharging and conventional turbocharging (two turbochargers), we obtained the universal characteristic curve of sequential turbocharging. Further, the propeller characteristic curves and load characteristic curves of trawlers under free-running and trawling operations were integrated. The analysis results show that the sequential turbocharging system increases the torque of trawlers by about 20% in the low-speed range; switching to two turbochargers in free-running mode reduces fuel consumption by ∼17.5 g/Wh; switching to basic turbocharging during trawling operations decreases fuel consumption by about 13.9 g/Wh. This study is not only beneficial for the economy of ships but also provides guidance for further improvements in engine mechanics, potentially attracting the interest of readers in the main engine manufacturing field.

Research on thermal-structural coupling and structural optimization of switching valve in booster system

Turbocharging technology is the second milestone in the development of internal combustion engine, which has become an inseparable part of engine technology and has a significant impact on the power and economy of internal combustion engine. The switching valve is a key component in the sequential turbocharging system, which plays a key role in realizing the energy distribution of the parallel turbocharger, the pressure ratio with different engine conditions, the flow regulation and the matching of the full working conditions. In order to explore the influence of different driving torque, gas pressure and temperature on the switching valve of the pressurization system, the steady-state statics and thermal-structural coupling simulation of the switching valve at room temperature were carried out by ANSYS Workbench software. Based on the central composite design method and Kriging method, the size combination and multi-objective response surface optimization model of 15 groups of switching valve design variables are obtained. Under the same conditions, the multi-objective genetic algorithm is used for simulation calculation. The results show that the deformation of the switching valve mainly occurs on the valve plate and the valve shaft under different driving torque and temperature, and it is symmetrically distributed. The distribution of deformation, stress, contact pressure and friction stress of the switching valve under different driving torques are the same. With the increase of driving torque and temperature, the deformation, stress, contact pressure and friction stress of the switching valve increase gradually, and the temperature effect is the most obvious. Compared with the original design size, the optimized structure size can effectively reduce the contact pressure of the switching valve and significantly improve the service life of the switching valve.

Experimental investigation of combustion characteristics analysis and optimization during the turbocharging mode switching process of diesel engine with advanced turbocharging system

Multi-turbocharger system is one of the major enablers of modern diesel engine performance. To meet the boosting requirements under different operating conditions is the difficulty. The two-stage sequential turbocharging (TSST) system creates the flexibility to select the turbocharging mode so that the engine benefits from efficiency and power density. However, the critical issue at hand is the unstable running, or even worse, misfire, of the engine caused by the abrupt air path shifts during the turbocharging mode switching process. Therefore, the control of the switching process is an indispensable procedure to apply the TSST system. The previous studies mainly focused on turbocharging system parameters. The combustion characteristics during switching process have been underestimated. The combustion process is influenced by the fuel and charging variations during the transient process, and it is unique compared with the steady state. In this paper, the experiments of TSST system switching process were carried out to investigate the transient combustion characteristics, formation mechanism of its fluctuation, and optimal control. The experimental results indicate that the combustion present fluctuation during the direct switching process. The main features are the generation and extinction of premixed combustion, combining the degradation and recovery of mixing-controlled combustion. The cycle history of heat-release center (CA50) presents a 3-phase fluctuation of moving backward from 9.7°CA to11.2°CA, then forward to 6.2°CA, and finally backward to 10.7°CA. The boost pressure trough is the primary factor contributing to incomplete combustion. The lowest gross indicated efficiency of 33.9 % happened at the lowest air-fuel ratio cycle. Based on the corresponding results, the substantial improvement in combustion can be ensured by regulating the switch valves in air path. When the intake switch valve opens 0.9 s later than the exhaust switch valve, the system exhibits minimal parameter fluctuations and the quickest recovery capacity. The coefficients of variation for IMEPg and CA50 are 2.7 % and 4.6 %, respectively, guaranteeing at least 39.7 % fuel conversion efficiency and only 17 cycles to reach the steady state.

Effects on the transient energy distribution of turbocharging mode switching for marine diesel engines

Nowadays, the high-power density and high efficiency of marine diesel engines make the requirements of high boost pressure and wide-range intake flow increased. In this study, a two-stage sequential turbocharging (TSST) system is presented as a method for increasing the power density and broadening the efficient working range of diesel engines. Through experimental and analysis methods, the relationships of intake and exhaust energy migration and exhaust energy distribution in the turbocharging mode switching process of the TSST system are investigated, and the optimal control strategy for the switching valves is obtained. The experimental results show that the optimized valve control strategy can achieve a reasonable distribution and efficient utilization of exhaust energy during the switching process. More specifically, the boost pressure error function is only 0.0003 kPa2·s, the engine speed fluctuation amplitude is less than 6 r/min, and the speed transition time is less than 8 s. A smooth switching between the turbocharging modes of the TSST system is achieved, exhaust energy loss is minimized, and the fuel economy and power performance of marine diesel engines over the entire range of operating conditions are effectively improved.

Setup and Control of a Two-Stage Turbocharged Gasoline Engine with Low Pressure EGR in a Prototype Vehicle

Abstract In order to cope with the strict emission standards for vehicles with internal combustion engines, new and innovative air path concepts with e.g. combined turbocharging and exhaust gas recirculation (EGR) are in the focus of research and the industry. Intensive simulative investigations of different concepts usually build the basis for determining which alternatives are promising and should be pursued. The concepts need to be tested and validated under conditions being as realistic as possible. Therefore, engines with the desired air and EGR path layouts are set up on test benches and tested under laboratory conditions. With the real-driving emission (RDE) legislation, it is crucial to test new air path concepts also during real driving on the road. Thus, demonstrator vehicles need to be developed. This paper presents the setup of a prototype demonstrator vehicle with an innovative air path concept for gasoline engines. The engine is equipped with a two stage sequential turbocharging system and a low pressure EGR path. As turbocharged gasoline engines have an increased specific power output, engines can be downsized for increased efficiencies. By using an EGR system, the increased in-cylinder temperatures of turbocharged engines during high load operation can be lowered, reducing the knock tendency and the exhaust gas temperature. The more and more complex air path concepts pose great demands on the process control which needs to handle nonlinear, cross-coupled multiple-input and multiple-output systems with dead times during transient operation. The setup of the vehicle with actuators, sensors and measurement technology as well as a possible control concept will be presented in detail.

Thermodynamic analysis of the turbocharged marine two-stroke engine cycle with different scavenging air control technologies

Scavenging air control has been recognized as a practical approach to optimizing the marine two-stroke engine performance under off-design conditions. This paper aims at providing a comprehensive comparison of different tuning technologies from thermodynamic perspectives. A new theoretical model for the marine two-stroke diesel engine is first built with all assumptions of an air-standard cycle relaxed. Thermodynamic characteristics of the two-stroke engine cycle integrating the turbocharged scavenging process are then studied, followed by parametric studies of different scavenging air control methods. The results show that there exists an optimal exhaust valve closing timing to minimize the so-called “Miller loss” with the high-pressure tuning. Despite similar fuel saving potential of 2.5 g/kWh is observed at low to medium loads, the high-pressure tuning is superior to the exhaust gas bypass tuning because of a lower engine thermal load. The power turbine bypass appears to be the best solution when the engine frequently operates at loads higher than 60%, while the sequential turbocharging system shows better performance at engine loads lower than 50%. Thus, factors including the engine thermal and mechanical limitations, ship’s operational profile, cost and package should be considered for selecting the optimal scavenging tuning method in a practical case.

New ABB Sequential Turbocharging System — Fuel Savings for Large Two-stroke Engines

New ABB Sequential Turbocharging System — Fuel Savings for Large Two-stroke Engines

Development and validation of a marine sequential turbocharging diesel engine combustion model based on double Wiebe function and partial least squares method

Developing an accurate combustion model for a Sequential Turbocharging diesel engine is an efficient way to reduce the time consumption and the expensive experiment costs in the process of determining the control strategy of a Sequential Turbocharging system. In this paper, 142 operations of a marine diesel engine with two Sequential Turbocharging systems are used for this research. A novel method is proposed to calculate the initial values and limit bounds of the Wiebe parameters, and the use of this method could effectively avoid the occurrence of impossible solutions or multiple solutions caused by only using nonlinear least square fitting. The calculated Wiebe parameters could achieve a high level of accuracy that the mean value of the determination coefficient between the simulated and experimental heat release rate profiles is 0.98 for all the operations, and they are accurate enough for developing the combustion model. The partial least square regression is first imposed to relate the Wiebe parameters to the operating conditions. For the ability to solve the multiple correlations among the operating conditions, the prediction performance of the combustion model developed by partial least square regression is much higher than that by least square regression. The mean absolute percentage errors of the brake specific fuel consumption and maximum in-cylinder pressure simulated by the model are 0.284% and 1.39%, respectively. The model could accurately predict the engine performance and is sufficient to make the reasonable control strategies for the different Sequential Turbocharging systems.

An approximate matching method for a parallel sequential turbocharging system

A theoretical study on matching a parallel sequential turbocharging system and a diesel engine is conducted. The relationship between the turbocharging system and the engine is represented through expressions for the geometry-equivalent areas of the turbine nozzle and the engine parameters, which are derived on the basis of the thermodynamics equations, and the mass and energy conservation of the turbocharging engine system. The feasible range of the geometry-equivalent areas of the turbine nozzle for a given engine operation condition is determined by the limits of the engine and the turbochargers. The number of sequential turbocharging system phases is determined by the feasible range of geometry-equivalent areas of the turbine nozzle, and the switching boundaries are calculated for the engine’s best performance. The matching method is applied to design the sequential turbocharging system for a six-cylinder diesel engine. The results prove that the number of phases and the switching boundary are accurately estimated by this model. The relative error in the pressure ratio between the results obtained by this matching method and those determined by the validated GT-Power model is less than 6.4%. It is helpful for sequential turbocharging preliminary selection and for providing a foundation for a further matching method.

Simulations of the diesel engine performance with a two-stage sequential turbocharging system at different altitudes

The turbocharging system of a six-cylinder diesel engine is analysed. It shows that the original single-stage turbocharger cannot meet the requirement that the engine should maintain a certain power output at different altitudes owing to the significant differences in the air density. A two-stage sequential turbocharging system is proposed, and the specific parameters of this turbocharging system are determined on the basis of the required power recovery of this engine. The engine performances at different altitudes with this two-stage sequential turbocharging system are simulated. The results show that, through switching between single-stage turbocharging and two-stage turbocharging, the engine power output can remain the same as that at sea level up to 2000 m and it can be recovered to 80% at 5500 m.

Development of a Three-Phase Sequential Turbocharging System with Two Unequal-Size Turbochargers

A three-phase sequential turbocharging system with two unequal-size turbochargers is developed to improve the fuel economy performance and reduce the smoke emission of the automotive diesel engine, and it has wider range of application than the current two-phase sequential turbocharging system. The steady matching method of the turbochargers and engine and the steady switching boundary are presented. The experimental results show that this system is effective to improve the engine performance especially at the low speed and high load. The maximum reductions of BSFC and smoke opacity are 7.1% and 70.9%. The optimized switching strategies of the valves are investigated, and the surge of the compressor in the switching process is avoided. The switching strategies in the accelerating process are optimized, and the acceleration time from 900 r/min and 2100 r/min at constant torque is reduced by approximately 20%.

Theoretical Calculation and Experimental Research on Sequential Turbocharging of a Marine Diesel Engine

The paper introduces the working principle of the sequential turbo-charging (STC) system of multi-turbocharger. To improve low-load performance and operating economy of the 234V12 diesel engine, a STC system of multi-turbocharger for the diesel engine was designed. Theoretical calculation and experimental research was done on this improved marine diesel engine. Then, a 3-phase STC system is presented by analyzing and comparing the test result and the switching boundary of this system is confirmed. The test results show that the low-load performance is improved obviously by use of multi-turbocharger STC system.

Experimental Study on the Three-phase Sequential Turbocharging System with Two Unequal Size Turbochargers

Experimental Study on the Three-phase Sequential Turbocharging System with Two Unequal Size Turbochargers

Grey Theory Approach to Sequential Turbocharged Diesel Engine

In order to ensure diesel engine operating reliably, need to forecast the performance parameters of diesel engine. Grey system theory, a method to research poor information and uncertain system, was approached to sequential turbocharged diesel engine. Grey forecast model of boost pressure of sequential turbocharged diesel engine was established. The precision of the forecast model was inspected by grey relation analysis, it is proved that the model has a good precision and is suitable to forecasting boost pressure. The relatively error of the forecast result is 2.5%. And it establishes the base for forecasting control and failure prediction of diesel engine sequential turbocharging system.