Robert Andrew Wade

Noise at the mid to high flow range of a turbocharger compressor

The acoustic and performance characteristics of an automotive centrifugal compressor are studied on a steady-flow turbocharger test bench, with the intention of identifying operating regions associated with flow noise within the compressor and connected ducting. Near choke, discrete tones including rotor-order frequency and its harmonics (bladepass) are observed. As the flow rate is reduced, the current compressor exhibited a broadband elevation of noise in the 4-12 kHz band, which was evident both in the upstream compressor duct and external sound pressure level (SPL) measurement locations. At all rotational speeds studied here, the total SPL in this frequency range demonstrates a strong dependence on the incidence angle of the incoming flow with the blades at the inducer of the impeller. When the incidence angle is further increased (mass flow rate is decreased) beyond a critical value, the temperature near the inducer tips increases sharply, suggesting local flow reversal, and the total SPL in the 4-12 kHz range suddenly reduces.

Effect of inlet vanes on centrifugal compressor acoustics and performance

The effect of inlet guide vanes (IGVs) on the acoustic and performance characteristics of an automotive centrifugal compressor is studied on a steady-flow turbocharger experimental facility. Broadband noise accompanying flow separation occurs as the flow rate of the compressor is reduced and the incidence angle of the flow relative to the leading edge of the inducer blades increases. The addition of IGVs upstream of the inducer imparts a tangential (swirl) velocity component in the same direction of impeller rotation, which improves the incidence angle particularly at low to mid-flow rates. In the present study, experimental data is compared for three compressor inlet geometries, including a no-swirl baseline along with two different IGV configurations. IGVs were shown to slightly improve the surge line at the highest rotational speed considered in this study, while compromising the maximum flow rate at all rotational speeds. In the high-flow range, IGVs are observed to increase compressor inlet noise levels over a wide frequency range. At the more common low to mid-flow range, however, broadband whoosh noise is reduced with the addition of IGVs in the 5-12 kHz band.

Simulation of surge in the air induction system of turbocharged internal combustion engines

A computational approach has been developed to accurately predict compression system surge instabilities within the induction system of turbocharged internal combustion engines by employing one-dimensional, nonlinear gas dynamics. This capability was first developed for a compression system installed on a turbocharger gas stand, in order to isolate the surge physics from the airborne pulsations of engine and simplify the ducting geometry. Findings fromthe turbocharger stand study were then utilized to create a new model of a twin, parallel turbocharged engine. Extensive development was carried out to accurately characterize the wave dynamics within key induction system components in terms of transmission loss and flow losses for the individual compressor inlet and outlet ducts. The engine was instrumented to obtain time-resolved measurements for model validation during surge instabilities, and simulation results agree well with the experimental data, in terms of both the amplitude and frequency. The present quasi-one-dimensional approach relaxes many of the assumptions inherent to earlier lumped parameter surge models; therefore, it provides the flexibility to model advanced boosting systems with multiple turbochargers and complex ducting geometry.

A case study of vehicle cooling system optimisation through system engineering

A case study of system engineering applied to resolving system integration issues on a vehicle cooling system is presented. Organisational learning that led to programme changes before project completion impeded the new product development process. Mutually exclusive requirements inhibited the system integration process and could have forced the water pump, heater core, and radiator to operate in conditions known to lead to failure. The challenges faced in correcting the system included working with independent organisation structures, tight programme timing, and changing evaluation methodology. The system engineering tools of the Parameter Diagram and Limit Diagram helped guide decisions on the programme. The application of system engineering principles led to organisational learning that improved the capability and confidence of the entire organisation. The Chief Engineer guided the team to prevent design iteration and look at improved subsystem requirements. An optimised design solution was found, which satisfied all subsystems and established a robust cooling system design. The V-Sequence model of system engineering is important for managing complex layered systems, but it requires Chief Engineer intervention to resolve integration issues and ensure timeliness of the programme.