Total pressure loss mechanism in a diesel engine turbocharger

Simulation tools are intensively used in the design stage of diesel engines due to their contributions to significant savings in cost and time for the engine development. Since most of DI diesel engines are turbocharged, it is of vital importance to hold a good understanding of turbine and compressor characteristic to predict the engine performance accurately. However, this data is often not available from turbocharger manufacturers, particularly for turbines. On available turbine maps the operating range of the turbine is constrained due to limitations of conventional turbocharger test benches. Operations with a wider range of turbocharger pressure ratios can be achieved by employing complex turbocharger test benches, which will also lead to higher costs including hardware and labour. An alternative solution is to develop numerical models for the turbocharger based on thermodynamics. In this thesis numerical models has been developed for predicting the performance of both the centrifugal compressors and turbines and they have been also validated using test cases, particularly for variable geometry turbines. Following detailed parametric studies, the turbocharger model has been validated against experimental data of a turbocharger with a variable geometry turbine. Results showed that the model was capable of predicting the characteristics maps of the turbocharger accurately, requiring a minimal amount of turbocharger geometric properties, experimental data and calibration parameters. Thus, by combing with the engine performance simulation software there is a highly potential for the numerical model developed in this work to become a useful tool for predicting engine performance and turbo matching calculations or diagnostic applications

Total pressure loss mechanism of centrifugal compressors

This paper describes the construction of the centrifugal compressor model and its validation with the experimental data. The compressor model in this paper uses One-dimensional (1D) thermo-fluid equations to analyse the compressor side of a turbocharger. Under a specified set of turbocharger geometry, atmospheric conditions, rotational speed, and fluid mass flow rate, the model can calculates the static and total temperatures, velocities, static and total pressures, pressure losses, and isentropic efficiencies for each compressor component. Instead of using lumped loss parameters, the compressor model includes established loss models found in the open literature. Not only in the impeller, the losses in the diffuser and the volute are modelled. With the model, it is possible for a parametric study on the effect of each loss mechanism on the performance, and which can aid the designer in justifying design decisions minimising the magnitude of the losses and thus positively influence the overall performance. The compressor model can also be applied to investigate the two stage Turbocharging or Variable Geometry Turbocharger (VGT) in the future

Turbocharger performance simulation with optimized 1D model

Turbocharging technique has played a critical role not only for improving automotive engine performance, but also for reducing fuel consumption and exhaust emissions both in Spark Ignition and Compression Ignition engines. In the research described in this paper, a 1D centrifugal compressor model has been developed for simulating turbocharger flow and performance. The model takes into account energy conservation and transfer which includes the losses determined from the compressor geometry. The losses including incident loss, friction loss, clearance loss, backward loss and volute loss were simulated by the thermodynamics model, rather than from the characteristic performance curves obtained experimentally. The proposed model was validated against experimental data and it showed simulating and experimental results are in very good agreement at three different rotational speeds, in particular near the surge line, though the deviation begins to increase as mass flow rate goes up. With current results, it has suggested the proposal is suitable for predicting the compressor performance curves such as outlet pressure, efficiency and losses for any centrifugal compressor. In addition, surge line obtained from the simulation result can be used to define stable operation range