Search Results

1D codes are nowadays commonly used to investigate a turbocharged ICE performance, turbo-matching and transient response. The turbocharger is usually described in terms of experimentally derived characteristic maps. The latter are commonly measured using the compressor as a brake for the turbine, under steady “hot gas” tests. This approach causes some drawbacks: each iso-speed is commonly limited to a narrow pressure ratio and mass flow rate range, while a wider operating domain is experienced on the engine; the turbine thermal conditions realized on the test rig may strongly differ from the coupled-to-engine operation; a “conventional” net turbine efficiency is really measured, since it includes the effects of the heat exchange on the compressor side, together with bearing friction and windage losses.

Turbocharged DISI engines with four cylinders have established in the market and provide a performance comparable to larger six-cylinder engines in the smaller compartment of a four-cylinder engine. In the Japanese market, also turbo gasoline engines with 500 - 660 cm₃ displacement have a long tradition in Kei-Cars. However, those engines show a lower specific performance as would be required for propelling typical small or compact vehicles in Europe. Recently, two-cylinder turbo engines have come to market, which are found attractive with respect to sound, package, and also enable low vehicle fuel consumption in NEDC test. The paper presents a turbocharger layout study on 2- and 3-cylinder engines. It discusses the influence of cylinder displacement volume on the sizing of turbines and compressors, and how specific flow phenomena in the turbine can be captured in the simulation model.

In the present paper, a recently developed centrifugal compressor model is briefly summarized. It provides a refined geometrical schematization of the device, especially of the impeller, starting from a reduced set of linear and angular dimensions. A geometrical module reproduces the 3D geometry of the impeller and furnishes the data employed to solve the 1D flow equations inside the rotating and stationary ducts constituting the complete device. The 1D compressor model allows to predict the performance maps (pressure ratio and efficiency) with good accuracy, once the tuning of a number of parameters is realized to characterize various flow losses and heat exchange. To overcome the limitations related to the model tuning, unknown parameters are selected with reference to 5 different devices employing an optimization procedure (modeFRONTIER™).