Search Results

Analysis of pressure pulsations in ducts is an active research field within the automotive industry. The fluid dynamics and the wave transmission properties of internal combustion (IC) engine intake and exhaust systems contribute to the energy efficiency of the engines and are hence important for the final amount of CO₂ that is emitted from the vehicles. Sound waves, originating from the pressure pulses caused by the in- and outflow at the engine valves, are transmitted through the intake and exhaust system and are an important cause of noise pollution from road traffic at low speeds. Reliable prediction methods are of major importance to enable effective optimization of gas exchange systems. The use of nonlinear one-dimensional (1D) gas dynamics simulation software packages is widespread within the automotive industry. These time-domain codes are mainly used to predict engine performance parameters such as output torque and power but can also give estimates of radiated orifice noise.

Non-linear 1-D CFD time domain prediction codes are used to calculate the performance of the gas exchange process for IC-engines. These softwares give time-varying pressures and velocities in the exhaust and intake systems. They could therefore in principle be used to predict radiated orifice noise. However, the accuracy is not sufficient for them to be used as a virtual design tool. More accurate results might be provided by dividing the problem into a source domain and a transmission domain and use linear 3-D frequency domain codes to describe the transmission part. Radiated shell noise and frequency dependent damping could also be included in the frequency domain models. The simplest source model used in the low frequency plane wave range for simulation of dominating engine harmonics is the linear time invariant 1-port model. This acoustic source data is usually obtained from experimental tests where the multi-load methods and especially the two-load method are most commonly used.

Turbochargers are common parts of a modern automotive engine. This paper presents an overview of the recent studies performed in the competence center for gas exchange studies at KTH on the sound transmission in turbochargers. The compressor and turbine of the turbochargers are treated as acoustic 2-ports and the scattering matrix for these devices are determined. A unique experimental facility established in the competence center for gas exchange research at KTH has been utilized to study the turbochargers at a variety of operating conditions systematically selected from compressor and turbine charts. A description of the experimental procedures to determine the acoustic 2-port data including techniques implemented to improve the quality of the results is presented. Results from a number of experiments on various modern automotive turbochargers including a unit with variable turbine geometry (VTG) are included.