NVH Optimization of Range Extender Engines by Electric Torque Profile Shaping
Range extender operation in an electric vehicle should be imperceptible to the driver from a noise/vibration standpoint. Rolling torque compensation allows virtually vibration-free range extender engine operation by utilizing a balanced counter-rotating inertia that is geared to the cranktrain. The combustion process results in engine torque fluctuations that could cause gear rattle in such a system due to a combination of torque reversal and lash in the geared connection. This brief paper addresses the problem of gear rattle in a rolling torque compensation system. First, a preloaded split gear is introduced as a potential mechanical solution to eliminate the clearance in the gear contact zone. In addition, an approach for a mechatronic solution involving active shaping of the generator torque is introduced. This methodology includes measurement of the combustion engine torque via cylinder pressure indication data, calculation of allowable torque limits, and the determination of a generator torque profile to address gear rattle. A multicriteria cost function is introduced to determine the optimal torque within the established constraints. Variations of the cost function are investigated with respect to their impact on efficiency and range extender acoustics.
A review of pivotal energy management strategies for extended range electric vehicles
Abstract To address the urgent environmental challenges of transportation related air pollution and energy shortage, hybrid electric vehicles (HEV) and battery electric vehicles (BEV) with potential for higher energy efficiency are gaining in popularity and gradually replacing those conventional vehicles. Extended range electric vehicle (EREV) is a subset of these new energy vehicles aiming to gain benefits of both HEVs and BEVs and provide a solution to reducing tailpipe emissions whilst providing satisfactory driving-range compared with tradition internal combustion engine (ICE) vehicle counterparts. This paper systematically introduces the current developments of EREV in terms of the powertrain structure, energy management and vehicle performance, while the two key focus areas of auxiliary power unit (APU) charging control and (hybrid) energy storage system ((H)ESS) power management. A case analysis on a typical EREV is presented to study the application potential. Comprehensive comparisons of popular APU control strategies and different energy storage dispositions are shared, several existing issues are also discussed in this paper. Furthermore, a general manufacturing cost analysis for different types of vehicles is presented, and the outlook of EREV for future research is presented.
Large eddy simulations of in-cylinder turbulence for internal combustion engines: A review
Abstract While engineering applications of the large eddy simulation (LES) technique are becoming a common reality in many branches of engineering and science, its application to engine flows has lagged behind due to the relatively more complex nature of both the flow and the geometry relevant to in-cylinder flows. In this paper a review of the limited number of LES applications to engine flows is given, and most significant results from these studies are presented. Also, the LES formulation appropriate for engine applications is briefly described, along with the main characteristics of in-cylinder flows. As expected, engine applications of LES are not of the so-called ‘high-fidelity’ type, but rather they employ formally second-order accurate numerical schemes in conjunction with finite volume formulation. The subgrid scale (SGS) models used are also kept as simple as possible, mostly using a variant of the Smagorinsky model. Nevertheless, this review reveals that even with relatively coarse grids, LES captures much more interesting features of in-cylinder flows, such as the large coherent vortical flow structures developed during the intake stroke. In the opinion of the present authors, a low-resolution LES provides a better solution than RANS (Reynolds averaged Navier-Stokes) with moderate grid resolution because the important features of flow dynamics cannot be reproduced in RANS due to the high level of non-physical diffusion. Of course, some overheads in computational costs must be paid for this benefit obtained from LES.