MECCA Journal of Middle European Construction and Design of Cars

CRITICAL SHIFTING WINDOW IN SWITCHABLE ROCKER FINGER FOLLOWER

Petr Kohout, Jan Kindermann — Wed, 10 Nov 2021 00:00:00 +0100

A valvetrain including switchable rocker finger follower is capable of discrete switching between two modes (two cam profiles). The exact moment when switching occurs is called crossover point and this paper reviews the factors that cause the shift of the crossover point from its nominal design position. The range where crossover point can shift is called critical shifting window and its size and factors influencing it will be adressed.

RANGE EXTENDER ICE MULTI-PARAMETRIC MULTI-OBJECTIVE OPTIMIZATION

Mikuláš Adámek, Rastislav Toman — Wed, 10 Nov 2021 00:00:00 +0100

Range Extended Electric Vehicles (REEV) are still one of the suitable concepts for modern sustainable low emission vehicles. REEV is equipped with a small and lightweight unit, comprised usually of an internal combustion engine with an electric generator, and has thus the technical potential to overcome the main limitations of a pure electric vehicle – range anxiety, overall driving range, heating, and air-conditioning demands – using smaller battery: saving money, and raw materials. Even though several REx ICE concepts were designed in past, most of the available studies lack more complex design and optimization approach, not exploiting the advantageous single point operation of these engines. Resulting engine designs are usually rather conservative, not optimized for the best efficiency. This paper presents a multi-parametric and multi-objective optimization approach, that is applied on a REx ICE. Our optimization toolchain combines a parametric GT-Suite ICE simulation model, modeFRONTIER optimization software with various optimization strategies, and a parametric CAD model, that first provides some simulation model inputs, and second also serves for the final designs’ feasibility check.

The chosen ICE concept is a 90 degrees V-twin engine, four-stroke, spark-ignition, naturally aspirated, port injected, OHV engine. The optimization goal is to find the thermodynamic optima for three different design scenarios of our concept – three different engine displacements – addressing the compactness requirement of a REx ICE. The optimization results show great fuel efficiency potential by applying our optimization methodology, following the general trends in increasing ICE efficiency, and power for a naturally aspirated concept.

IN-CYLINDER FLOW CHARACTERIZATION USING VORTICITY BASED PARAMETERS

Petr Hatschbach, Oldřich Vítek, Radek Tichánek — Fri, 01 Jun 2018 00:00:00 +0200

The paper deals with intake swirling flow characterization in the cylinder of IC engine. The commonly used method based on the swirl resp. tumble number from angular momentum flux evaluation does not need to give the appropriate values in some cases. Typically, in the case of two intake ports, a counter-rotating swirl vortex pair is presented. However their summary angular momentum flux is zero a thus corresponding swirl number is zero too. In order to correctly quantify these cases, it is proposed to evaluate so called vorticity numbers, i.e. dimensionless numbers based on vorticity evaluation. Concrete results are evaluated from data obtained using 3-D CFD simulation in AVL FIRE code. Comparison of variously defined vorticity numbers with each other and with the vortex numbers is performed. A practical way of calculating the vorticity numbers was also suggested with regard to possible adverse effects of the velocity gradients at the cylinder wall.