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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.

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.

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.

Zheng X.,Tsinghua University | Zhang Y.,Tsinghua University | Xing W.,National Key Laboratory of Diesel Engine Turbocharging Technology | Zhang J.,National Key Laboratory of Diesel Engine Turbocharging Technology
Journal of Turbomachinery | Year: 2011

Flow separation control was investigated on a compressor cascade using three types of fluidic-based excitations: steady suction, steady blowing, and synthetic jet. By solving unsteady Reynolds-averaged Navier-Stokes equations, the effect of excitation parameters (amplitude, angle, and location) on performance was addressed. The results show that the separated flow can be controlled by the fluidic-based actuators effectively and the time-averaged performance of the flow field can be improved remarkably. Generally, the improvement can be enhanced when the amplitude of excitation is increased. The optimal direction varies with each type of excitations and is related to physical mechanisms underlying the separation control. For two types of steady excitations, the most effective jet location is at a distance upstream of the time-averaged separation point and the synthetic jet is just at the separation point. © 2011 American Society of Mechanical Engineers.

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.

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.

Hu L.,Beijing Institute of Technology | Yang C.,Beijing Institute of Technology | Sun H.,Ford Motor Company | Zhang J.,National Key Laboratory of Diesel Engine Turbocharging Technology | Lai M.,Wayne State University
Chinese Journal of Mechanical Engineering (English Edition) | Year: 2011

Variable nozzle turbine (VNT) has become a popular variable geometry turbine (VGT) technology for the diesel engine application. Nozzle clearance, which can't be avoided on the hub and shroud side of the VNT turbine due to the pivoting stators, can lead to turbine performance deterioration. However, its mechanism is still not clear. In this paper, numerical investigation, which is validated by experiment, is carried out to study the mechanism of the nozzle clearance's effect on the turbine performance. Firstly, performance of the mixed flow turbine with fixed nozzle clearances tested on flow bench. Performance of the tested turbine with the same nozzle clearance is numerically simulated. The numerical result agrees well with the test data, which proves correct of the numerical method. Then the turbine performance with different nozzle clearances is numerically analyzed. The research showed that with nozzle clearance, flow loss in the nozzle increases at first and it reaches the maximum value when the clearance ratio is 5%. Flow at the exit of the nozzle becomes less uniform with nozzle clearance. The negative incidence angle of the rotor also increases with nozzle clearance and leads to more incidence angle loss in the rotor. The low energy fluid formed in the nozzle due to the nozzle clearance migrates from hub to shroud side in the rotor, which is another main reason for the rotor's performance degradation. The present research exposed the mechanism of the dramatically decrease of the turbine performance with nozzle clearance: (a) The loss associated with the nozzle leakage increases with the nozzle clearance; (b) The flow loss grows up quickly in the rotor due to the incidence angle loss and migration of the low energy fluid from hub to shroud side. ©2011 Chinese Journal of Mechanical Engineering.

Li D.,Beijing Institute of Technology | Yang C.,Beijing Institute of Technology | Zhao B.,Beijing Institute of Technology | Zhou M.,Bohai Shipbuilding Vocational College | And 2 more authors.
Journal of Thermal Science | Year: 2011

Assembling an axial rotor and a stator at centrifugal compressor upstream to build an axial-radial combined compressor could achieve high pressure ratio and efficiency by appropriate size augment. Then upstream potential flow and wake effect appear at centrifugal impeller inlet. In this paper, the axial-radial compressor is unsteadily simulated by three-dimensional Reynolds averaged Navier-Stokes equations with uniform and circumferential distorted total pressure inlet condition to investigate upstream effect on radial rotor. The results show that span-wise nonuniform total pressure distribution is generated and radial and circumferential combined distortion is formed at centrifugal rotor inlet. The upstream stator wake deflects to rotor rotation direction and decreases with blade span increases. Circumferential distortion causes different separated flow formations at different pitch positions. The tip leakage vortex is suppressed in centrifugal blade passages. Under distorted inlet condition, flow direction of centrifugal impeller leading edge upstream varies evidently near hub and shroud but varies slightly at mid-span. In addition, compressor stage inlet distortion produces remarkable effect on blade loading of centrifugal blade both along chordwise and pitchwise. © 2010 Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg.

Qi M.,Beijing University of Technology | Cao L.,Beijing University of Technology | Hu L.,National Key Laboratory of Diesel Engine Turbocharging Technology | Zhang J.,National Key Laboratory of Diesel Engine Turbocharging Technology
Institution of Mechanical Engineers - 10th International Conference on Turbochargers and Turbocharging | Year: 2012

Unsteady flow simulation on 150mm centrifugal compressor with impeller-vaneless diffuser-volute configuration is carried out. Pressure pulsations at observed points under both stationary and rotating frame are transformed into frequency domain to investigate the rotating and turbulent noise characteristics. Spectrum analysis results on observed points under stationary frame show that in centrifugal compressor with vaneless diffuser, dominating noise signals are related with the pressure pulsation at frequency of BPF, which is caused by the passing of each impeller blade. Noise signals at frequency of half BPF and odd order multiples can also be observed but with much weakened power, and as a result, their devotion to the overall noise level is trivial. Results also show that in the compressor investigated in current work, the main sources of rotating noise locate near the mid-streamwise region of impeller, with pressure pulsation amplitude reaches the level of 7.1kPa. Spectrum analysis on pressure pulsations captured under rotating frame clarifies that noise signals are dominated by wheel passing frequency, which are caused by the potential flow interaction between impeller and volute tongue. Meanwhile, pressure pulsation strength increases as the distance to volute tongue decreases, with maximum amplitude reaches about 5.1kPa near the exit of the impeller. Anyway, no sign of noise radiation outside of centrifugal compressor is captured for such kind of pulsation, hence, they do not contribute the compressor radiation noise. © The author(s) and/or their employer(s), 2012.

Wang Z.,National Key Laboratory of Diesel Engine Turbocharging Technology | Wang A.-N.,Shenyang Ligong University
IEEM2010 - IEEE International Conference on Industrial Engineering and Engineering Management | Year: 2010

The failure fate model of components based on the load-strength interference model is proposed, and the relationship between the failure rate of components and time in different cases is studied. The existing failure rate calculation methods of components are analyzed, and it is pointed out that these methods for calculating the failure rate of products are all based on the statistic analysis of fail data and can not reflect the relationship between the failure rate and the factors. Then, the failure rate model capable of embodying the effect of load and strength and its degradation is developed with the time-dependent load-strength interference. The results show that for the different combinations of load and strength, the failure rate curves of components are different and have the whole or partial characteristic of bathtub-shaped curve. The method proposed can present the relationship between the failure rate of components and the parameters of load and strength, and it can be used to calculate the failure rate of components accurately as long as the parameters of load, strength and the rule of strength degradation are known. Hence, it is more applicable for the reliability design and the lifecycle management of components. ©2010 IEEE.

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