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Wang W.,Shanghai JiaoTong University | Lu Z.,Shanghai JiaoTong University | Deng K.,Shanghai JiaoTong University | Qu S.,National Key Laboratory of Diesel Engine Turbocharging Technology
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2015

Junction flow loss is one of the sources of flow losses in many engineering pipe systems. An experimental study was carried out in order to investigate the combining steady pressure loss coefficients at 45° T-junctions with three area ratios between lateral branch and main duct. Extensive measurement data were obtained at a wide range of Mach number (0.1-0.6) and mass flow rate ratios using air as the tested fluid. Comparative analysis of the results includes the pressure difference in the two flow paths of the junction, the effect of Mach number in common branch due to gas compressibility, as well as the loss coefficients with various geometry condition. The following conclusion is drawn: the total pressure loss coefficient (K) was mainly dependent on the Mach number (M3), mass flow rate ratio (q), and area ratio (a), while almost independent on Reynolds number. The results provide reference for the research of junction flow and can be valuable in the correction of the boundary condition in one-dimensional simulation models. © 2014 Institution of Mechanical Engineers. Source


Liu Y.B.,Tsinghua University | Liu Y.B.,Academy of Armored force Engineering | Zhuge W.L.,Tsinghua University | Zhang Y.J.,Tsinghua University | Zhang S.Y.,National Key Laboratory of Diesel Engine Turbocharging Technology
IOP Conference Series: Materials Science and Engineering | Year: 2016

To reach the goal of energy conservation and emission reduction, high intake pressure is needed to meet the demand of high power density and high EGR rate for internal combustion engine. Present power density of diesel engine has reached 90KW/L and intake pressure ratio needed is over 5. Two-stage turbocharging system is an effective way to realize high compression ratio. Because turbocharging system compression work derives from exhaust gas energy. Efficiency of exhaust gas energy influenced by design and matching of turbine system is important to performance of high supercharging engine. Conventional turbine system is assembled by single-stage turbocharger turbines and turbine matching is based on turbine MAP measured on test rig. Flow between turbine system is assumed uniform and value of outlet physical quantities of turbine are regarded as the same as ambient value. However, there are three-dimension flow field distortion and outlet physical quantities value change which will influence performance of turbine system as were demonstrated by some studies. For engine equipped with two-stage turbocharging system, optimization of turbine system design will increase efficiency of exhaust gas energy and thereby increase engine power density. However flow interaction of turbine system will change flow in turbine and influence turbine performance. To recognize the interaction characteristics between high pressure turbine and low pressure turbine, flow in turbine system is modeled and simulated numerically. The calculation results suggested that static pressure field at inlet to low pressure turbine increases back pressure of high pressure turbine, however efficiency of high pressure turbine changes little; distorted velocity field at outlet to high pressure turbine results in swirl at inlet to low pressure turbine. Clockwise swirl results in large negative angle of attack at inlet to rotor which causes flow loss in turbine impeller passages and decreases turbine efficiency. However negative angle of attack decreases when inlet swirl is anti-clockwise and efficiency of low pressure turbine can be increased by 3% compared to inlet condition of clockwise swirl. Consequently flow simulation and analysis are able to aid in figuring out interaction mechanism of turbine system and optimizing turbine system design. Source


Wang S.-M.,Shanghai JiaoTong University | Zhu J.,Shanghai JiaoTong University | Deng K.-Y.,Shanghai JiaoTong University | Cui Y.,Shanghai JiaoTong University | Xing W.-D.,National Key Laboratory of Diesel Engine Turbocharging Technology
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering | Year: 2011

A variable-geometry exhaust manifold (VGEM) turbocharging system can realize a switch between two charging modes by use of a controllable valve, and it can give a good performance at both high-speed operation and low-speed operation. In this paper, a new idea about the VGEM turbocharging system for a six-cylinder diesel engine is proposed, and preliminary experiments on this are carried out. Experiments on the two cases when the controllable valve is closed or is open respectively are performed using two different exhaust manifolds. The steady state experimental results indicate that the turbocharging system works as a pulse turbocharging system and the pulse energy can be utilized fully when the controllable valve is closed at low-speed operation; the turbocharging system works as a semiconstantpressure turbocharging system and the pumping loss can be reduced fully when the controllable valve is open at high-speed operation. The transient experimental results indicate that the transient performance of the pulse turbocharging system is better than that of the semiconstant-pressure turbocharging system. © Authors 2011. Source


Zhang Y.,Tsinghua University | Chen T.,Tsinghua University | Zhuge W.,Tsinghua University | Zhang S.,National Key Laboratory of Diesel Engine Turbocharging Technology | Xu J.,CAS Institute of Engineering Thermophysics
Science China Technological Sciences | Year: 2010

Turbocharging technology is today considered as a promising way for internal combustion engine energy saving and CO2 reduction. Turbocharger design is a major challenge for turbocharged engine performance improvement. The turbocharger designer must draw upon the information of engine operation conditions, and an appropriate link between the engine requirements and design features must be carefully developed to generate the most suitable design recommendation. The objective of this research is to develop a turbocharger design approach for better turbocharger matching to an internal combustion engine. The development of the approach is based on the concept of turbocharger design and interaction links between engine cycle requirements and design parameter values. A turbocharger through flow model is then used to generate the design alternatives. This integrated method has been applied with success to a gasoline engine turbocharger assembly. © 2010 Science in China Press and Springer Berlin Heidelberg. Source


Zhang Y.J.,Tsinghua University | Chen L.,Tsinghua University | Zhuge W.L.,Tsinghua University | Zhang S.Y.,National Key Laboratory of Diesel Engine Turbocharging Technology
Science China Technological Sciences | Year: 2011

Recovery of heat energy from internal combustion engine exhaust will achieve significant road transportation CO2 reduction. Turbocharging and turbogenerating are most commonly used technologies to recover engine exhaust heat energy. Engine exhaust pulse flow can significantly affect the turbine performance of turbocharging and turbogenerating systems, and it is necessary to consider the pulse flow effects in turbine design and performance analysis. An investigation was carried out by numerical simulation on the mixed flow turbine pulse flow performance and flow fields. Results showed that the variations of the turbine efficiency and flowfiled under pulsating flow conditions demonstrate significant unsteady effects. The effect of blade leading edge sweep on turbine pulse flow performance was studied. It is shown that increasing of the leading edge sweep angle can improve the turbine average instantaneous efficiency by about 2 percent under pulsating flow conditions. © Science China Press and Springer-Verlag Berlin Heidelberg 2011. Source

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