Abstract
Despite the public debate nowadays on the future of Internal Combustion Engines (ICE), which is impeding their development, one limitation towards further optimization of ICE in terms of fuel consumption and emissions can be seen in the current approach and more specifically in the transient engine operation and its control. The main drawbacks in the current approach source from: 1) complex structure of mechanization including sensors and actuators, 2) low time resolution and accuracy of sensing (cost driven), 3) complex Electronic Control Unit (ECU)-software architecture associated with huge calibration effort and 4) recently, funded research due to unsecure business model of ICE is becoming less. To overcome these difficulties unexploited potential should be utilized. Some of this potential lies in cycle-by-cycle and cylinder-by-cylinder accurate fuel and air control, and in the development of physical based virtual sensors with high time resolution and accuracy. One of the main motivations for this study was to develop a measurement technique that enables crank-angle resolved air mass flow rate measurements during engine operation in a dynamometer test cell. The measurement principle is quite simple and is based on gauging the dynamic pressure in both the intake and exhaust duct at the closest possible positions to the valves. To fulfill these requirements aerodynamic probes have been developed and manufactured utilizing 3D printing. The probes have been integrated in special developed flanges, which correspond exactly to the shape of the air channels in the cylinder head of the engine. Hence, they can be mounted either in front of the valves at the intake or behind the valves at the exhaust duct. Results at different engine operating conditions have been obtained, analyzed and correlated to other sensors like air-flow meter. Those post-processed results can be further used to validate 1-D gas exchange models, or 3-D Computational Fluid Dynamics (CFD) port flow models. The ultimate scope of these measurements is to calibrate fast physical-based gas exchange models that can be directly used in the engine control framework on an embedded system.
Highlights
A detailed understanding of the flow structure and turbulence generation within the cylinder of an ICE has been the focus of countless research projects and publications over the last few decades
Implementation of the aerodynamic probes at the TH Nuremberg research engine allows a high-resolution data acquisition of the dynamic pressure, in the intake duct of the engine and enables the calculation of the flow velocity. Aerodynamic probes for both the intake and exhaust ducts have been developed and applied, only the intake duct has been considered in the present study
A novel aerodynamic probe has been developed in cooperation with the probe manufacturer Vectoflow GmbH and applied on a research engine at TH Nuremberg
Summary
A detailed understanding of the flow structure and turbulence generation within the cylinder of an ICE has been the focus of countless research projects and publications over the last few decades. [(Haworth, 1999), (Celik et al, 2001)] As engine flows are inherently 3D, the ability to resolve the complete flow structure becomes increasingly important to analyze instantaneous turbulent flow phenomena and validate turbulent models Such capabilities are anticipated to provide further insight into the study of turbulence and CCV as well as build more predictive models describing the engine flow [(Pope, 2015)]. It enables the sharing of boundary data between 1D and 3D models in a single or multi-domain system This way the in-cylinder process is resolved using more detailed CFD simulation of 3D flows and is coupled to a 1D gas exchange model to account for time varying boundary conditions in the intake duct. There is a limited chance to evaluate crank-angle-based flow velocities and turbulence in the intake duct and the mass flow rate through the intake and exhaust valves during the opening period [(Lomas, 2011), (Westerweel et al, 2013), (Jainski et al, 2013), (Hwang et al, 2007), (Desantes, et al, 2010)]
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