Oskar Leufvén

Time to surge concept and surge control for acceleration performance

Surge is a dangerous instability that can occur in compressors. It is avoided using a valve that reduces the compressor pressure. The control of this valve is important for the compressor safety bu ...

Scalable Component-Based Modeling for Optimizing Engines with Supercharging, E-Boost and Turbocompound Concepts

Downsizing and turbocharging is a proven technology for fuel consumption reduction in vehicles. To further improve the performance, electrified components in the turbocharger arrangements have been ...

Wastegate Actuator Modeling and Model-Based Boost Pressure Control

The torque response of an engine is important for driver acceptance. For turbocharged spark ignited (TCSI) engines this is tightly connected to the boost pressure control, which is usually achieved ...

Surge and Choke Capable Compressor Model

A compressor model is developed. It is capable of representing mass flow and pressure characteristic for three different regions: surge, normal operation as well as for when the compressor acts as ...

Measurement, analysis and modeling of centrifugal compressor flow for low pressure ratios

Increasingly stringent emission legislation combined with consumer performance demands has driven the development of downsized engines with complex turbocharger arrangements. To handle the complexity, model-based methods have become a standard tool, and these methods need models that are capable of describing all operating modes of the systems. The models should also be easily parametrized and enable extrapolation. Both single- and multi-stage turbo systems can operate with a pressure drop over their compressors, both stationary and transient. The focus here is to develop models that can describe centrifugal compressors that operate in both normal region and restriction region from standstill to maximum speed. The modeling results rely on an analysis of 305 automotive compressor maps, whereof five contain measured restriction operation and two contain measured standstill characteristic. A standstill compressor is shown to choke at a pressure ratio of approximately 0.5, and the corresponding choking corrected mass flow being approximately 50% of the compressor maximum flow capacity. Both choking pressure ratio and flow are then shown to increase with corrected speed, and the choking pressure ratio is shown to occur at pressure ratios larger than unity for higher speeds. Simple empirical models are proposed and shown to be able to describe high flow and pressure ratios down to choking conditions well. A novel compressor flow model is proposed and validated to capture the high flow asymptote well, for speeds from standstill up to maximum.

Engine Test Bench Turbo Mapping

A method for determining turbocharger performance on installations in an engine test bench is developed and investigated. The focus is on the mapping of compressor performance but some attention is ...

Investigation of compressor correction quantities for automotive applications

Turbo performance is represented using maps, measured for one set of inlet conditions. Corrections are then applied to scale the performance to other inlet conditions. A turbo compressor for automotive applications experiences large variations in inlet conditions, and the use of two-stage charging increases these variations. The variations are the motivation for analysing the correction quantities and their validity. A novel surge-avoidance strategy is found in the correction equations, where the result is that a reduction in inlet pressure can increase the surge margin of eight studied maps. The method for investigating the applicability of the strategy is general. An experimental analysis of the applicability of the commonly used correction factors, used when estimating compressor performance for varying inlet conditions, is presented. A set of experimental measurements from an engine test cell and from a gas stand shows a small but clearly measurable trend, with decreasing compressor pressure ratio for decreasing compressor inlet pressure. A method is developed, enabling measurements to be analysed with modified corrections. An adjusted shaft speed correction quantity is proposed, also incorporating the inlet pressure in the shaft speed correction. The resulting decrease in high-altitude engine performance, due to compressor limitations, is quantified and shows a reduction in altitude of 200–600 m, for when engine torque has to be reduced due to limited compressor operation.

Model-Based Boost Pressure Control with System Voltage Disturbance Rejection

Actuation systems for automotive boost control incorporate a vacuum tank and PWM controlled vacuum valves to increase the boosting system flexibility. Physical models for the actuator system are co ...