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BACKGROUND Powertrain developers have suggested that slip at the vehicle tire and chassis dynamometer contact point for US06 emissions testing causes unmanageable variability. In order to counteract slip, some developers have been requesting their vehicles be strapped down tighter. Strapping a vehicle down tighter may lead to unrepresentatively low fuel economy and high emissions (many tests are run FTP/Hwy/US06 consecutively). EXPERIMENT A study was developed to investigate the effects of dynamometer roll surface roughness and vehicle restraint strap tension on fuel economy, emissions, and the amount of wheel slip. In addition, a correlation may be established between wheel slip and fuel economy and emissions. A three factor, two-level, full factorial design with three replicates was planned. The factors were dynamometer surface roughness, vehicle, and strap tension.

The amount of electrical power required for future aircraft is increasing significantly. In this paper, a comprehensive model of a drive shaft with multiple degrees of freedom was developed and integrated to detailed engine and electrical network models to study the impact of higher electrical loads. The overall system model is composed of the engine, shafts, gearbox, and the electric network. The Dynamic Dual Spool High Bypass JT9D engine was chosen for this study. The engine was modeled using NASA’s T-MATS (Toolbox for the Modeling and Analysis of Thermodynamic Systems) software. In the electrical side, one generator was connected to the Low Pressure (LP) shaft and the other to the High Pressure (HP) shaft. A modified model of the shafts between the engine and the accessory gearbox was created.

The aim of current research on internal combustion engines is to further reduce exhaust gas pollutant emissions while simultaneously lowering carbon dioxide emissions in order to limit the greenhouse effect. Due to the restricted potential for reducing CO2 (carbon dioxide) emissions when using fossil fuels, an extensive defossilisation of the transport sector is necessary. Investigations of future propulsion systems should therefore not focus solely on further development of the prime mover, but also on the energy carrier which is used. In this context, fuels from renewable energy sources are of particular interest, e.g. paraffinic diesel fuels such as hydrogenated vegetable oil (HVO) or potentially entirely synthetic fuels like POMDME (polyoxymethylene dimethyl ether, short: OME) as well as blends of such fuels.

This work presents a numerical study of the Spray A (n-dodecane) characteristics using Eulerian and Lagrangian models in a finite-volume framework. The standard k-ε turbulence model was applied for the spray simulations. For Eulerian simulations, the X-ray measured injector geometries from the Engine Combustion Network (ECN) were employed. The High-Resolution Interface Capturing (HRIC) scheme coupled with a cavitation model was utilized to track the fluid-gas interface. Simulations under both the cool and hot ambient conditions were performed. The effects of various grid sizes, turbulence constants, nozzle geometries, and initial gas volume within the injector sac on the modeling results were evaluated. As indicated by the Eulerian simulation results, no cavitation was observed for the Spray A injector; a minimum mesh size of 15.6 μm could achieve a reasonably convergent criterion; the nominal nozzle geometry predicted similar results to the X-ray measured nozzle geometry.

The morphology of the internal flow of Spray C was numerically investigated using an Eulerian volume-of-fluid (VOF) method in the finite-volume framework. The injector geometry available in the Engine Combustion Network (ECN) was employed, and the simulations were performed under the ambient condition at 900 K and 60 bar. The simulation data were analyzed for three important events: the initial nozzle opening, steady injection, and nozzle closing. First, projected densities on XY and XZ planes are computed radially at four axial locations. Projected density at 2 mm is compared with available experimental results, which show similar results. Then, the mass flow rate is found to match the reported experimental results and the virtually generated values from CMT using an appropriate discharge coefficient. An investigation on the appropriate discharge coefficient is performed and found that Cd = 0.63 ± 0.02 is acceptable for Spray C.

The original contribution of this paper in this field of research is the successful thermodynamical modelling of a complex geometry of a Diesel Engine utilizing the Method of Characteristics. For this purpose, a 16 cylinder, ‘V’ type, turbocharged, 4 ported (2-intake, 2-exhaust) High Speed Marine Diesel Engine was tested at 1900 rpm. For the analytical investigation, one dimensional, time dependant gas flow throughout the inlet and exhaust manifolds of a Marine Diesel Engine is shown to be successfully modelled by the non homentropic gas flow theory. In order to model the four ports on a cylinder, the narrow passages towards the ports inside the cylinder head are considered as a couple of short ducts connected to each other through a junction. Analytical and experimental results are compared with the gas pressure variations at the middle of the inlet pipes before cylinders and in the corresponding cylinders.

Today, high performance race car efficiency is based on a very fine equilibrium between aerodynamic efficiency, engine performance, and chassis behaviour. In particular, from the engine point of view, one way to increase the performance is to increase its volumetric efficiency. The aim of this paper is to present the application of the Large Eddy Simulation (LES) approach for the fluid dynamic analysis of a high performance race car airbox geometry. For a naturally aspired engine, the fluid dynamic optimisation of the airbox geometry means to optimise the energy conversion (from dynamic to static pressure) inside the airbox itself, therefore to increase the flow energy on the engine trumpet sections. The LES approach seems to be the best candidate to investigate such a flow since flow unsteadiness are expected to affect airbox efficiency in terms of pressure recovery. The airbox simulations were performed by using the commercial CFD code Fluent v6.3.

The two-stroke SI engine remains the dominant concept for handheld power tools. Its main advantages are a good power-to-weight ratio, simple mechanical design and low production costs. Because of these reasons, the two-stroke SI engine will remain the dominant engine in such applications for the foreseeable future. Increasingly stringent exhaust emission laws, in conjunction with the drive for more efficiency, have made new scavenging and combustion processes necessary. The main foci are to reduce raw emissions of unburned hydrocarbons via intelligent guidance of the fresh air-fuel mixture and to improve performance to reduce specific emissions. The flow velocity in the electrode gap of the spark plug is of great interest for the ignition of the air-fuel-mixture and the early combustion phase of all kinds of SI engines. In these investigations, the flow velocity in the spark plug gap of a two-stroke gasoline engine with stratified scavenging was measured under various conditions.

This paper presents an investigation of a Volvo Direct Injection Spark Ignition (DISI) engine, where the fuel distribution and the in-cylinder flow field have been mapped by the use of laser techniques in an engine with optical access. Along with the experimental work, CFD-modelling of flow and fuel distribution has been performed. Laser Induced Fluorescence (LIF) visualisation of the fuel distribution in a DI-engine has been performed using an endoscopic detection system. Due to the complex piston crown geometry it was not possible to monitor the critical area around the sparkplug with conventional, through the piston, detection. Therefore, an endoscope inserted in the spark plug hole was used. This approach gave an unrestricted view over the desired area. In addition, the in-cylinder flow fields have been monitored by Particle Image Velocimetry (PIV) through cylinder and piston. The results from both the LIF and the PIV measurements have been compared with CFD-modelling at Volvo.

Results of experiments performed on a direct-injection two-stroke engine using an air-assisted injector are presented. Pressure measurements in both the engine cylinder and injector body coupled with backlit photographs of the spray provide a qualitative understanding of the spray dynamics from the oscillating poppet system. The temporal evolution of the spatial distribution of both liquid and vapor fuel were measured within the cylinder using the Exciplex technique with a new dopant which is suitable for tracing gasoline. However, a temperature dependence of the vapor phase fluorescence was found that limits the direct quantitative interpretation of the images. Investigation of a number of realizations of the vapor field at a time typical of ignition for a stratified-charge engine shows a high degree of cycle to cycle variability with some cycles exhibiting a high level of charge stratification.

The influence of the bulk in-cylinder flow on the spray evolution, evaporation, fuel-air mixing and subsequent flame propagation has been studied in an optical SIDI engine. Quantitative LIF imaging of equivalence ratios was used to characterize the mixture formation and the influence of the local equivalence ratio at the time of spark on the flame propagation. Two extreme bulk flow conditions - high and low swirl - were investigated and pronounced differences in mixture homogeneity and flame propagation were found and characterized.

For scavenging the combustion chamber during the gas exchange, a temporary positive pressure gradient between the intake and the exhaust is required. On a single-scroll turbocharged four cylinder engine, the positive pressure gradient is not realized by the spatial separation of the exhaust manifold (twin-scroll), but by the use of suitable short exhaust valve opening times. In order to avoid any influence of the following firing cylinder onto the ongoing scavenging process, the valve opening time has to be shorter than 180 °CA. Such a short valve opening time has both, a strong influence on the gas exchange at the low-end torque and at the maximum engine power. This paper analyzes a phenomenon, which occurs due to short exhaust valve opening durations and late valve timings: A repeated compression of the burned cylinder charge after the bottom dead center, referred to as “recompression” in this paper.

At flex fuel technology introduction in the Brazilian market, new technical issues came-up due to ethanol chemical reaction with component materials developed only for gasoline aging. One of these items was the gel formation at fuel system. This gel flows through the fuel systems and clogs the fuel filters. And, as final result, the fuel pump is lost due to overpressure working condition. To implement solutions against this way of failure, it was necessary to understand gel formation mechanism in laboratory level. In this investigation, many boundary conditions were changed and analyzed in order to identify contribution of each factor during gel formation process. As result, it was possible to implement a laboratory gel formation test for fuel filters, not depending any more from field tests and allowing test repeatability to develop an improved fuel filter.

The paper reports an investigation into the HCCI/CAI combustion process in a single cylinder optical engine. The auto-ignition and combustion processes of primary reference fuels were studied using the two-dimensional PLIF technique as well as heat release analyses. The formaldehyde formed during the low-temperature reactions of HCCI/CAI combustion was visualized by a PLIF system. The formaldehyde was excited by a Nd:YAG laser pumped tunable dye laser at 355nm wavelength and detected by a gated ICCD camera. Both temporal and spatial distributions of formaldehyde were measured during the auto-ignition processes of different primary reference fuels. The results have shown that the formation of formaldehyde and its subsequent disappearance were closely related to the start of the low temperature and high temperature heat release processes, respectively. The formation of formaldehyde was more affected by the charge temperature than by the fuel concentration.

A capillary pumped two-phase ammonia heat transport loop, developed at Lavochkin Assoc., Moscow, was tested under laboratory conditions at ERNO, Bremen. The tubular capillary pump evaporator contains a sintered Nickel powder body with a small pore size of 1. 5 μm. The line diameter of the vapour and the liquid line is only 6 mm and 4 mm, respectively, allowing an easy accomodation to any architecture in the filled state. The objective of the test was to determine the heat transport performance of the loop under different orientations w.r.t. gravity under steady state and transient, in particular priming load conditions. The tests have demonstrated a large heat transport performance of more than 1100 W in a vertical orientation, where the evaporator was located 2 m (!) above the condenser. The priming ability appears to depend on the load timeline as well as on the orientation.

This paper reports on research works of helical inlet ports applied in direct injection diesel engines. It is widely recognised that swirl is transferred to air current before it leaves the valve, but according to these experiments reported here, air current moves directly into cylinder after leaving the valve and then a great deal of effective swirl or angular momentum is generated in cylinder. Experimental results in this paper are obtained mainly by means of a simple macroscopic trace visualisation technique, which will do well to future engine design and development.

In the “high-pressure-dual-fuel” (HPDF) combustion process, natural gas is directly injected into the combustion chamber with high pressure at the end of the compression stroke, and burned in a diffusion flame similar to conventional diesel combustion. As natural gas does not self-ignite when injected into hot air, a small amount of diesel fuel is injected directly before the gas injection to provide an ignition source for the gas jets. The HPDF combustion process has the potential to substantially reduce methane slip compared to today’s state of the art premixed lean burn gas engines, and furthermore, phenomena like knocking or misfire can be avoided completely. In this paper, the influences of in-cylinder air density and swirl motion on HPDF combustion is studied via high-speed recordings in a fully optically accessible 4.8 Liter single-cylinder research engine.

The “Two-Drive-Transmission with Range-Extender” (called DE-REX) is an innovative hybrid powertrain concept using two electric motors and an internal combustion engine. The two electric motors are permanent magnet synchronous motors with a maximum power of 48 kW each. As combustion engine a 3 cylinder, turbocharged engine with a power of 65 kW is used. The aggregates are coupled to a transmission whose layout is characterized by consisting of two parallel 2-speed sub-transmissions. This layout offers a high flexibility and enables both parallel and series hybrid driving. The hybrid control unit (HCU) has to select the optimal driving mode and power distribution between the aggregates in regard to in some extend competing objectives like efficiency, emissions or driving comfort. In particular, the operation of the internal combustion engine with only two gear ratios is challenging.

State of the art high-pressure fuel injectors offer the ability to inject multiple times per cycle, and can reach very low fuel amounts per injection event. This behaviour allows the application of pilot injections in diesel engine applications or dual fuel engines. In both diesel and dual fuel engines, the amount of pilot fuel affects the engine efficiency. The understanding of the underlying ignition mechanism of the pilot fuel is required to optimize injection parameters and the engines’ fuel consumption. The present work focuses on the differences of ignition mechanisms between long and short injections. The investigation has been performed numerically, using CFD with a well-proven combustion model. The setup used employs a well characterized single orifice injector, injecting into a high temperature, pressurized environment with a composition of 15% oxygen.

Auto-ignition in Diesel engines, occurring essentially under non-premixed and partially premixed conditions, is considerably different to homogeneous ignition. In order to study the relevant chemistry--mixing interactions, it is assumed that the ignition of Diesel fuel can be described by using the single component model fuel n-heptane. Starting from a detailed chemical reaction scheme with about 1000 elementary reactions among 168 chemical components, a skeletal mechanism consisting of 98 reactions and 40 components is derived, which is still capable of describing the auto-ignition process under Diesel engine conditions and concentrations of NO, relevant intermediate components. Introducing steady state assumptions for intermediate species which are consumed rapidly leads to a reduced 14-step mechanism. The mechanism is validated with auto-ignition delay times from shock tube experiments by Adomeit for different temperatures, pressures, and equivalence ratios.