Engine-in-the-Loop Testing for Evaluating Hybrid Propulsion Concepts and Transient Emissions - HMMWV Case Study

Abstract

This paper describes a test cell setup for concurrent running of a real engine and a vehicle system simulation, and its use for evaluating engine performance when integrated with a conventional and a hybrid electric driveline/vehicle. This engine-in-the-loop (EIL) system uses fast instruments and emission analyzers to investigate how critical in-vehicle transients affect engine system response and transient emissions. Main enablers of the work include the highly dynamic AC electric dynamometer with the accompanying computerized control system and the computationally efficient simulation of the driveline/vehicle system. The latter is developed through systematic energy-based proper modeling that tailors the virtual model to capture critical powertrain transients while running in real time. Coupling the real engine with the virtual driveline/vehicle offers a chance to easily modify vehicle parameters, and even study two different powertrain configurations. In particular, the paper describes the engine-in-the-loop study of a V8, 6L engine coupled to a virtual 4x4 HighMobility Multipurpose Wheeled Vehicle (HMMWV). The results shed light on critical transients in a conventional powertrain and their effect on NO x and soot emissions. Next, the conventional HMMWV powertrain is replaced with a parallel hybrid electric configuration and two power management strategies are examined. Comparison of the conventional and hybrid propulsion options provides detailed insight into fuel economyemissions tradeoffs at the vehicle level.

Hydraulic Hybrid Propulsion for Heavy Vehicles: Combining the Simulation and Engine-In-the-Loop Techniques to Maximize the Fuel Economy and Emission Benefits

“…The uncovered integration challenges and the solutions for development of the EIL setup for a conventional vehicle were described by Filipi et al in [12]. An extensive review of previous efforts by others related to HIL and EIL methodologies are also provided in [12], and in [13].…”

“…The model includes an engine torque map, a fuel controller with speed-governing functions and engine dynamics. The lookup table providing brake torque as a function of instantaneous engine speed and mass of fuel injected is generated from experimental data obtained in the W. E. Lay Automotive Laboratory at the University of Michigan using a fully instrumented Navistar V8 6L turbocharged diesel [12]. The diesel engine specifications are listed in the Appendix.…”

“…Unfortunately, simulating soot formation processes in a diesel engine is prohibitively slow in the context of systems work, since it requires coupling of sophisticated Computational Fluid Dynamics (CFD) models and chemical kinetics [17,18]. Therefore, we develop the Engine-In-theLoop capability to accurately characterize the influence of the SHHV system design and control on engine-out emissions, since running the engine in the test cell enables accurate real-time diagnostics of soot and NO x emissions [12]. In other words, the EIL is viewed as an additional methodology essential for the hybrid system development and analysis, rather than the tool for calibration of engine controller maps.…”

“…Our initial experience with the series HHV challenged the notion that running the engine at the "efficiency sweat spot" is the best for the vehicle fuel economy [11], therefore we investigate modulated State-Of-Charge (SOC) control as an alternative to the thermostatic, or "bang-bang" strategy. Finally, the Engine-In-the-Loop (EIL) facility [12] is brought into the fold to investigate the behavior of the real diesel engine system, including its external components and actuators, coupled to a virtual driveline/vehicle and assess the low-emission potential of the hydraulic hybrid. Further discussion about the role of EIL in developing the SHHV system is provided in the subsequent paragraph, followed by the outline of the paper.…”

Equivalent Consumption Minimization Strategy for the Control of Real Driving NOx Emissions of a Diesel Hybrid Electric Vehicle

“…However, the rate of change of the engine torque is limited by 100 N m/s in order to prevent the formation of excessive soot and NO x emissions during transients [23,31].…”