Development and Validation of an Ignition Model for SI Engines

In SI engines the ignition process strongly affects the combustion process. Its accurate modelling becomes a key issue for a design-oriented CFD simulation of the combustion process. Different approaches to simulate ignition have been proposed. The common base is decoupling the physics related to the very first ignition phase when a plasma is formed from that of the development of the flame kernel. The critical point of ignition models is related to the capability of representing the effect of ignition system characteristics, the criterion used for flame deposit and the initialisation of the combustion model. This paper aims to present and validates extensively an ignition model suited for CFD calculation of premixed combustion. The ignition model implemented in a customized version of the Kiva 3 code is coupled with ECFM Flamelet combustion model. The ignition model simulates the plasma/kernel expansion based on a lump evaluation of main ignition processes (i.e., breakdown, arc-phase and glow phase). A double switch criterion based on physical and numerical consideration is used to switch to the main combustion model. The Herweg and Maly experimental test case has been used to check the model capability. In particular, two different ignition systems having different amount of electrical energy released during spark discharge are considered. Comparisons with experimental results allowed testing the model with respect to its capability to reproduce the effects of mixture equivalence ratio, mean flow, turbulence and spark energy on flame kernel development as never done before in three-dimensional RANS CFD combustion modelling of premixed flames.

The Effect of Engine Exhaust Temperature Modulations on the Performance of Automotive Catalytic Converters

This paper presents a computational investigation of the effect of exhaust temperature modulations on an automotive catalytic converter. The objective is to develop a better fundamental understanding of the converter’s performance under transient driving conditions. Such an understanding will be beneficial in devising improved emission control methodologies. The study employs a single-channel based, one-dimensional, non-adiabatic model. The transient conditions are imposed by varying the exhaust gas temperature sinusoidally. The results show that temperature modulations cause a significant departure in the catalyst behavior from its steady behavior, and modulations have both favorable and harmful effects on pollutant conversion. The operating conditions and the modulating gas composition and flow rates (space velocity) have substantial influence on catalyst behavior.

Tumble Flow Measurements Using Three Different Methods and Its Effects on Fuel Economy and Emissions

In-cylinder flows such as tumble and swirl have an important role on the engine combustion efficiencies and emission formations. In particular, the tumble flow, which is dominant in-cylinder flow in current high performance gasoline engines, has an important effect on the fuel consumptions and exhaust emissions under part load conditions. Therefore, it is important to know the effect of the tumble ratio on the part load performance and optimize the tumble ratio of a gasoline engine for better fuel economy and exhaust emissions. First step in optimizing a tumble flow is to measure a tumble ratio accurately. In this research the tumble flow was measured, compared and correlated using three different measurement methods: steady flow rig, 2-Dimensional PIV, and 3-Dimensional PTV. Engine dynamometer test was performed to find out the effect of the tumble ratio on the part load performance. Dynamometer test results of high tumble ratio engine showed faster combustion speed, retarded MBT timing, higher exhaust emissions, and a better lean burn combustion stability. Lean limit of the baseline engine was expanded from A/F=18:1 to A/F=21:1 by increasing a tumble ratio using MTV.

Effects of Boost Pressure on Piston Lubrication of Diesel Engine

The state of piston lubrication-has been determined with reference to piston friction force measured by our developed single-cylinder supercharged small bore diesel engine with a boost pressure of up to 150kPa. The result is that the state of lubrication deteriorates markedly immediately before the compression top dead center due to increased boost pressure and immediately after the compression top dead center due to increased engine load. Moreover, the crankshaft offset, piston pin offset and multi-grade oil further deteriorate piston lubrication with a boost pressure.

Fuzzy Controller Without Feed-Forward for the Air System of a Diesel Engine

A new strategy based on a fuzzy multi-variable controller is proposed to regulate both the fresh airflow and the intake manifold pressure. The air system controller requires neither an internal model nor certain feed-forward maps. Taking only into account standard engine measurements, it is intrinsically robust and very easy to tune with respect to strategies proposed in literature. The results obtained with this controller are compared to those of current embedded controllers.

Advanced Elastohydrodynamic Analysis of Journal Bearings in IC Engines With a Multi-Body System Approach

This paper presents a rigorous analysis of the elastohydrodynamic (EHD) lubrication of journal bearings in internal combustion (IC) engines. The approach treats a set of radial slider (plain journal) bearings as a system or a subsystem. Thus, they can be simulated simultaneously, and hence the system effect is included. The analysis considers both the elasticity and dynamics of the connected parts such as the cylinder block (or main bearing walls), crankshaft and conrod. Both local vibration and global motion of these elastic parts are modelled by a multi-body system (MBS) approach. Hence, the EHD behaviour of engine bearings is simulated in a realistic manner.

Exhaust System Gas-Dynamics in Internal Combustion Engines

The sensitivity of engine performance to gas-dynamic phenomena in the exhaust system has been known for around 100 years but is still relatively poorly understood. The nonlinearity of the wave-propagation behaviour renders simple empirical approaches ineffective, even in a single-cylinder engine. The adoption of analytical tools such as engine-cycle-simulation codes has enabled greater understanding of the tuning mechanisms but for multi-cylinder engines has required the development of accurate models for pipe junctions. The present work examines the propagation of pressure waves through pipe junctions using shock-tube rigs in order to validate a computational model. Following this the effects of exhaust-system gas dynamics on engine performance are discussed using the results from an engine-cycle-simulation program based on the equations of one-dimensional compressible fluid flow.

An Experimental Analysis of Flow Through Annular Diffuser With and Without Struts

This paper presents the static pressure development and the effect of struts on the performance of an annular diffuser. A typical exhaust diffuser of an industrial gas turbine is annular with structural members, called struts, which extend radially from the inner to the outer annulus wall. An annular diffuser model, primarily intended for fundamental research, has been tested on a wind tunnel. Similar conditions that prevail in an industrial gas turbine have been generated in the diffuser. Measurements were made using a five holed Pitot probe. The research had been carried out to make a detailed investigation on the effect of struts and to advance computational and design tools for gas turbine exhaust diffusers.

DEVERT®: The DEUTZ Concept to Meet the Emission Level U.S. EPA Tier 3 and EU COM 3A for Non-Road Engines

From 2006 to 2008 depending on the power ratings, Deutz has to update its complete engine product portfolio of compact engines to meet the emission legislation U.S. EPA Tier 3 and EU COM 3A for applications of mobile nonroad machinery. This challenge covers air cooled, oil cooled and as well water cooled engines up to 500 kW. To provide the best solution for the customer with respect to engine price, fuel consumption, power rating and torque characteristics. Deutz will introduce a technology concept called DEVERT® — Deutz Variable Emissions Reduction Technology. In the wide range of industrial applications of construction machinery, agriculture, material handling, and others DEVERT® provides an optimised solution for every case. The technology approach of DEVERT® consists of injection systems like the mechanical unit pump system and the Deutz Common Rail (DCR®), 2 and 4 valve cylinder-heads, different solutions for internal and external exhaust gas recirculation, and also variable valve actuation. The focus of this paper is on the water-cooled, in-line engine families 2012 and 2013 with a displacement of 4 to 7 l. Based on the application of DEVERT® to these engine families the different technologies are explained by their functionality and their impact on emissions and performance. A short outlook of the emission legislation on future technologies is given. Here exhaust after-treatment will have a significant impact on the engine package with new challenges for the variety of applications.

Modeling of Variable Intake Valve Timing in SI Engine

In internal combustion engines valve events and timings are among the most important parameters which have a major influence on the engine’s operation and volumetric efficiency. By using camless valvetrain strategy, improvement in fuel economy as well as an increase in entering air charge is found throughout the engine map with the largest benefits arising from low speed operating conditions. The system offers a continuously variable and independent control of virtually all parameters of valve motion. This permits optimization of valve events for each operating condition without any compromise. In this paper we describe a phenomenological model for an unthrottled operation of a camless intake process of spark-ignited (SI) engine. Initially the cylinder breathing dynamics is modeled and results are validated with experimental data of a conventional engine with cam-driven valve profile during unthrottled operation. Then we determine the most optimized intake valve profile in order to have the most volumetric efficiency and proper operation for each operating condition based on the existing model and using numerical techniques.