Study on Correction Method of Internal Joint Operation Curve Based on Unsteady Flow

The turbocharger, a key component in a vehicle’s powertrain, results in insufficient accuracy if it does not fully consider the unsteady flow effects of the intake and exhaust systems. Based on the difference between the turbocharger’s actual operating performance with unsteady flow and the corresponding steady flow performance, unsteady flow correction concepts and correction methods for the compressor and turbine were put forward, and the correction of the internal joint operation curve was investigated. The results show that when unsteady correction coefficients were added to both ends of the turbocharger and the optimized structure was used at both ends, the original turbocharger’s surge margin was reduced by 4.6% to 11.8%, and that of the optimized turbocharger was reduced by 15.2% to 21.9% in the medium–low-speed range. Meanwhile, the unsteady flow energy utilization coefficient of the optimized turbocharger was more than 14.5% higher than that of the original turbocharger in the medium–low speed range, and the energy utilization advantage was obvious. It indicated that the optimized turbocharger was working earlier, and the engine’s medium–low-speed admission performance has been obviously improved. Therefore, compared with the steady curve, the corrected unsteady curve was closer to the actual engine performance.