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Radial flow Variable Nozzle Turbine (VNT) enables better matching between the turbocharger and engine. At partial loading or low-end engine operating points, the nozzle vane opening of the VNT is decreased to achieve higher turbine efficiency and transient response, which is a benefit for engine fuel consumption and emission. However, under certain small nozzle opening conditions (such as nozzle brake and low-end operating points), strong shock waves and strong nozzle clearance flow are generated. Consequently, strong rotor-stator interaction between turbine nozzle and impeller is the key factor of the impeller high cycle fatigue and failure. In present paper, flow visualization experiment is carried out on a linear turbine nozzle. The turbine nozzle is designed to have single-sided clearance, and the Schlieren visualization method is used to describe the formation and development process of clearance flow and shock wave under different clearance and expansion ratio configurations.

The low cycle fatigue experiment is extensively used to test the reliability and durability of turbocharger. Low cycle fatigue test is mainly the switching between high and low speed. As the result of the experiment, the fatigue life is shorter as the difference between high and low speed becomes greater. In the traditional low cycle fatigue test, a large air compressor is needed to drive the turbocharger under different operating conditions, which consume large amounts of electric power. This paper presents a new experiment device which has double chambers and double turbochargers. This device can be self-circulating, without the large air compressor, to realize high and low speed switching on the premise of not exceeding the limitation of turbine entry temperature. First, a detailed model is established in GT-Power and self-circulation test data has been used to validate the model.

A boost system with an auxiliary gas turbine used to recover diesel engine power at plateau conditions is proposed. System matching calculation, preliminary design, and performance simulation of the compressor with double parameter output are presented, as well as the preliminary design, flow simulation, and combustion process of the combustion chamber. Results show that the new system has better recovery performance and higher fuel economy potential than the simple charging scheme. For future research work, possible improvements and development direction are recommended.

Performances of a centrifugal turbocharger compressor are investigated and validated in this paper. Based on the validation results, numerical optimizations are performed using ANN and CFD methods. Different impeller geometry with free parameters controlling stacking laws, end-wall, blade sectional camber curves and corresponding performances are used as input layer of ANN in the optimization, while adiabatic total-to-total efficiency and total pressure ratio are used as output layer of the optimization cycle. With this method, the performances of the compressor investigated in this paper are improved notably.