Co-surge in bi-turbo engines: Measurements, analysis and control

Abstract

In parallel turbocharged V-engines, with two separate air paths connected before the throttle, an oscillation in the flow can occur. If the compressor operates close to the surge line, typically during low speed and high load, and a disturbance alters the mass flow balance, the compressors can begin to alternately go into surge. This phenomenon is called co-surge and is unwanted due to high noise and risk for turbocharger destruction. Co-surge is measured on a test vehicle in a chassis dynamometer and the system analyzed and modeled using a mean value engine model. The investigation shows that the alternating compressor speeds have an important role in the prolonged oscillation. A reconstruction of the negative flow from measurements is made and compared to simulation results, showing similar amplitudes, and supports the model validation. A new co-surge detection algorithm is presented, suitable for a pair of sensors measuring either mass flow, boost pressure or turbo speed in the two air paths. Furthermore, a new controller is proposed that uses a model based feedforward for the throttle, together with wastegate actuation to force the compressor speeds together and improve balance at the recovery point. This has shown to be sufficient with moderate to high pressure ratios over the throttle, only for zero or very low pressure drop the use of bypass valves are necessary. The advantage of not opening the bypass valves is a smaller drop in boost pressure which also reduces the torque disturbance. The performance of the controller is evaluated both in simulation and in the test vehicle.

Analysis and characterization of a marine turbocharger’s unstable performance

“…6,7 The same applies for diesel particulate filters (DPF), which cause a pressure drop due flow blockage by soot accumulation over time. 8 Other configurations for NOx reduction with limited efficiency losses include combinations of exhaust gas recirculation (EGR) with sequential 9 and two-stage 10–12 turbocharging. In all of these cases, it was proved that compressor surge was a limiting factor in the design and optimization of these systems.…”

Effects of Pulsating Flow on Mass Flow Balance and Surge Margin in Parallel Turbocharged Engines

“…When the surging compressor recovers it can then push the other compressor into surge, resulting in a mass flow oscillation between the two compressors that alternately go into surge. This phenomena has been investigated in Thomasson and Eriksson (2014), that also shows how the main behavior of the cosurge oscillation can be captured by a Mean Value Engine Model (MVEM), without considering in-cycle variations.…”