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The fulfillment of the aggravated demands on future small-size High-Speed Direct Injection (HSDI) Diesel engines requires next to the optimization of the injection system and the combustion chamber also the generation of an optimal in-cylinder swirl charge motion. To evaluate different port concepts for modern HSDI Diesel engines, usually quantities as the in-cylinder swirl ratio and the flow coefficient are determined, which are measured on a steady-state flow test bench. It has been shown that different valve lift strategies nominally lead to similar swirl levels. However, significant differences in combustion behavior and engine-out emissions give rise to the assumption that local differences in the in-cylinder flow structure caused by different valve lift strategies have noticeable impact. In this study an additional criterion, the homogeneity of the swirl flow, is introduced and a new approach for a quantitative assessment of swirl flow pattern is presented.

Electromechanical valve trains in camless engines enable virtually fully variable valve timing that offers large potential for both part load fuel economy and high low end torque. Based upon the principle of a spring-mass-oscillator, the actuator stores the energy to open and close the valves in springs. However, the motion of the valves and the electromechanical actuation suffers from parasitic losses, such as friction and ohmic resistance. Besides eddy current losses, gas forces obviously play a further important role in the control of exhaust valve opening especially at high engine speeds and loads. Based on engine test bench data, computational simulations (3D CFD, gas exchange process and electromechanical system) are carried out to analyze the effects of exhaust valve gas forces on the dynamic motion of valve and actuator. The modeling approach and results of this investigation are discussed in this paper.

A broad variety of new technologies for improving fuel economy is currently under development or investigation. The general statement is that always a compromise between fuel economy benefit and engine oncost has to be found. This paper describes a new way for improving fuel economy based on existing technologies used in a refined way. It is shown that with very simple and robust measures on the intake and exhaust ports and on the valve train mechanism 2 valve and 4 valve engines can show a significant improvement in fuel consumption without having a great cost penalty for production. The basic system consists of a single cam phaser and a special port arrangement on a 2 valve engine with a single camshaft operated at stoichiometric air/fuel ratio utilizing internal EGR and a reverse “Miller-Cycle”. Variable charge motion is generated using a shared flow through the intake and the exhaust port by varying cam timing.

The main goal in the development of new automobile SI engines is to significantly reduce fuel consumption. To this end both, variable valve actuation and direct gasoline injection, are being pursued as new engine concepts. Both approaches appear to offer approximately the same potential to reduce fuel consumption. The development so far is creating the impression of two competing technical concepts with no obvious way to combine them [1]. The two engine concepts, however, can be combined, although it is often objected that their combination would only yield marginal additional potential. That is true to the extent that the advantages of dethrottling offered by both of the concepts can only be counted once in terms of overall potential. But there is a number of additional effects to be taken into account. This Paper represents an analysis of the individual potential of the two approaches as well as an estimation of their combined potential.

A computational study of the flow in intake port geometries has been performed. Three different intake port geometries, namely two combined tangential and helical ports and one quiescent port were analyzed. Each of these cases was calculated for different valve lifts and the results were compared with available measurements. The focus of this paper is on the performance assessment of the variable resolution Partial-Averaged Navier-Stokes (PANS) method. Calculations have been also performed with the Reynolds-averaged Navier-Stokes (RANS) model, which is presently a state-of-the-art approach for this application in the industry. Besides the averaged integral values like a discharge coefficient and a swirl coefficient, the predicted velocity magnitude fields at the measured cross sections of the ports are compared due to available Particle Image Velocimetry (PIV) measurements.

A series calculation methodology from the injector nozzle internal flow to the in-cylinder fuel spray and mixture formation in a diesel engine was developed. The present method was applied to a valve covered orifice (VCO) nozzle with the recent common rail injector system. The nozzle internal flow calculation using an Eulerian three-fluid model and a cavitation model was performed. The needle valve movement during the injection period was taken into account in this calculation. Inside the nozzle hole, cavitation appears at the nozzle hole inlet edge, and the cavitation region separates into two regions due to a secondary flow in the cross section, and it is distributed to the nozzle exit. Unsteady change of the secondary flow caused by needle movement affects the cavitation distribution in the nozzle hole, and the spread angle of the velocity vector at the nozzle exit.

Due to the future application of combustion engines in small and hybrid vehicles, the demand for high efficiency with low mass and compact engine design is of prime importance. The diesel engine, with its outstanding thermal efficiency, is a well suited candidate for such applications. In order to realize these targets, future diesel engines will need to have increasingly higher specific output combined with increased power to weight ratios. This is therefore driving the need for new designs of 3 and/or 4 cylinder, small bore engines of low displacement, sub 1.5l. Recent work on combustion development, has shown that combustion systems, ports, valves and injector sizes are available for bore sizes down to 65 mm.