Experimental and numerical investigation of the thermomechanical load on a turbine housing in a radial turbocharger

The fatigue life of turbine housing is an important index to measure the reliability of a radial turbocharger. The increase in turbine inlet temperatures in the last few years has resulted in a decrease in the fatigue life of turbine housing. A simulation method and experimental verification are required to predict the life of a turbine housing in the early design and development process precisely. The temperature field distribution of the turbine housing is calculated using the steady-state bidirectional coupled conjugate heat transfer method. Next, the temperature field results are considered as the boundary for calculating the turbine housing temperature and thermomechanical strain, and then, the thermomechanical strain of the turbine housing is determined. Infrared and digital image correlations are used to measure the turbine housing surface temperature and total thermomechanical strain. Compared to the numerical solution, the maximum temperature RMS (Root Mean Square) error of the monitoring point in the monitoring area is only 3.5%; the maximum strain RMS error reached 11%. Experimental results of temperature field test and strain measurement test show that the testing temperature and total strain results are approximately equal to the solution of the numerical simulation. Based on the comparison between the numerical calculation and experimental results, the numerical simulation and test results were found to be in good agreement. The experimental and simulation results of this method can be used as the temperature and strain (stress) boundaries for subsequent thermomechanical fatigue (TMF) simulation analysis of the turbine housing.

Efficiency Comparison of Hydro Turbines in a Micro Generator System from Free-flow Vortex

This study aimed to enhance a micro hydroelectric generator system driven by free-flow vortex and to compare efficiency of Propeller and Crossflow turbines. Series of turbines in each type were designed and tested at water-flowrate of 0.02 m3/s. The turbine housing has 1 meter in diameter and 0.5-meter height with 2 meters outlet drain at the bottom. The best efficiency extracted from Crossflow turbines with the same height (0.3 meter) but different in diameter (0.4, 0.5, 0.6, and 0.7 meter) and numbers of blade (12, 18, 24, 30, and 23) was from an 18 blades turbine at 23.01% of efficiency. The best efficiency extracted from Propeller turbines with 5 blades was from a 0.4-meter-high turbine with a diameter of 0.7 meter at 13.92% of efficiency. There were 12 Propeller turbines designed in this study. They were different in height (0.2, 0.3, and 0.4 meter) and, in each height, 0.4, 0.5, 0.6, and 0.7 of diameter was applied. The result revealed that Cross Flow turbine had more efficiency to the system than Propeller turbine (9.09%) at the water-flowrate of 0.02 m3/s

The Experimental Study of the Inner Insulated Turbocharger Turbine

For turbocharged diesel engine systems, emission reduction is the most significant challenge that manufacturers should overcome. In response to the emission reduction challenge most turbocharged diesel engine systems have adopted complex exhaust aftertreatment systems. Due to the current stringent emission regulation, exhaust aftertreatment system nowadays needs to discover new methods to increase its efficiency of pollution conversion. Increasing the inlet temperature of aftertreatment systems can help reduce the light-off time. Whilst most methods to do this involve increases in fuel consumption (retarded injection, engine throttling), insulating the turbocharger turbine to reduce heat loss does not have this drawback. This paper presents a simulation and experimental study the performance of a turbocharger with inner insulated turbine housing, compared with the standard turbocharger (same turbine wheel without inner insulation). Both turbochargers were tested on an engine gas stand test rig with a 2.2L prototype engine acting as an exhaust gas generator. In a steady state condition, the insulated turbocharger can achieve 5 to 14K higher turbine outlet temperature depending on the engine speed and load conditions. Three types of transient tests were implemented to investigate turbocharger turbine heat transfer performance. The test plan was designed to the engine warm up, step load transient, WLTC cycle and simplified RDE cycle. In the engine warm up test result, the temperature drops between the turbine inlet and outlet was reduced by 4K with the insulated turbine housing. In the results of step load transient test, the turbine with insulated turbine housing was observed to get only 4K temperature benefit but with 2kRPM higher turbocharger speed under the same turbocharger inlet and outlet boundary conditions. In the WLTC cycle test result, turbocharger average speed was increased by 0.8kRPM due to the increased enthalpy of the turbine with insulation, the turbine outlet temperature has an average 1.7K improvement. The experimental results were used to parameterise a simple, 1D, lumped capacitance model which could predict similar aerodynamic behaviour of the two turbines (turbine housing insulated and non-insulated). However, current model has less accuracy in highly transient process as the heat transfer coefficients are unchangeable in each process. The turbine outlet temperature got at most 10K error for the turbine with non-insulated housing and 13K error for the insulated one. The model was shown to over-estimate the benefits of the inner insulation for 1K in turbine outlet temperature.

Dimensionless quantification of small radial turbine transient performance

Turbochargers are inherently dynamic devices, comprising internal flow volumes, mechanical inertias and thermal masses. When operating under transient conditions within an engine system, these dynamics need to be better understood. In this paper, a new non-dimensional modelling approach to characterise the turbocharger is proposed. Two new dimensionless quantities are defined with respect to mechanical and thermal transient behaviour, which are used in conjunction with the Strouhal number for flow transients. The modelling approach is applied to a small wastegated turbocharger and validated against experimental results. The model is used to simulate the turbocharger mass flow rate, turbine housing temperature and shaft speed responses to different excitation frequencies for different sizes of turbine. The results highlight the influence of turbocharger size on the dynamic behaviour of the system, which is particularly marked for the turbine housing temperature. At certain frequency ranges, the system behaviour is quasi-steady, allowing modelling through static maps in these operating regions. Outside these ranges, however, transient elements play a more important role. The simulation study shows that the proposed dimensionless parameters can be used to normalise the influence of turbine size on the dynamic response characteristics of the system. The model and corresponding dimensionless parameters can be applied in future simulation studies as well as for turbocharger matching in industry.