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Increasing fuel and electricity prices create high pressure to develop efficient external aerodynamics of road cars. At the same time, development cycles are getting shorter to meet changing customer preferences while physical testing capacities remain limited, creating a pressing need for fast and accurate turbulence models to predict aerodynamic performance. This paper introduces and discusses different turbulence modelling approaches beyond the well-known and established models used today in the industry. The RANS Lag Elliptic Blending (Lag EB) k − ϵ model, which enables highly accurate steady-state RANS, was chosen as the baseline approach. As a medium fidelity approach Scale-Resolving Hybrid (SRH) model was utilized, which modifies a RANS base model to produce a smooth transition between URANS and LES behavior. The Wall-Modelled LES (WMLES) method was chosen for high fidelity simulations.

The direct injection diesel engine is one of the most efficient thermal engines known to man. For this reason DI diesel engines are widely used for heavy-duty applications and especially for the propulsion of trucks. Even though the efficiency of these engines is currently at a high level there still exist possibilities for further improvement. One way to accomplish this is by increasing the injection timing which usually improves, depending on the operating conditions, the indicated efficiency of the engine. On the other hand advanced injection timing has a negative effect on peak pressure causing a serious increase of its value, a negative effect on NO emissions which are also seriously increased and a positive effect on Soot emissions which are reduced. In the present work a theoretical and experimental investigation is presented to determine the effect of more advanced injection timing on engine performance and pollutant emissions.

The present paper aims to discuss the quality characteristics of Jet Fuels used in the Greek market in comparison with fuels used in other countries and to evaluate jet fuels along with diesel and biodiesel on a diesel engine. To establish the quality characteristics for Jet Fuels of the Greek market, fuel samples were collected from the local refineries on a regular basis, thus monitoring the fuel quality fluctuation over time. JP8, along with diesel and biodiesel, were used alone and in mixtures on a single cylinder stationary diesel engine. Emissions and volumetric fuel consumption were measured under various loads.

The paper discusses the concept, design and final results from the ‘Ultra Boost for Economy’ collaborative project, which was part-funded by the Technology Strategy Board, the UK's innovation agency. The project comprised industry- and academia-wide expertise to demonstrate that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ such a concept in premium vehicles. In addition to achieving the torque curve of the Jaguar Land Rover naturally-aspirated 5.0 litre V8 engine (which included generating 25 bar BMEP at 1000 rpm), the main project target was to show that such a downsized engine could, in itself, provide a major proportion of a route towards a 35% reduction in vehicle tailpipe CO2 on the New European Drive Cycle, together with some vehicle-based modifications and the assumption of stop-start technology being used instead of hybridization.

In a turbocharged engine, preserving the maximum amount of exhaust pulse energy for turbine operation will result in improved low end torque and engine transient response. However, the exhaust flow entering the turbine is highly unsteady, and the presence of the turbine as a restriction in the exhaust flow results in a higher pressure at the cylinder exhaust ports and consequently poor scavenging. This leads to an increase in the amount of residual gas in the combustion chamber, compared to the naturally-aspirated equivalent, thereby increasing the tendency for engine knock. If the level of residual gas can be reduced and controlled, it should enable the engine to operate at a higher compression ratio, improving its thermal efficiency. This paper presents a method of turbocharger matching for reducing residual gas content in a turbocharged engine.

To reduce the fuel related logistic burden, NATO Armed Forces are advancing the use of a single fuel for both aircraft and ground equipment. To this end, F-34 is replacing distillate diesel fuel in many applications. Yet, unacceptable wear due to poor lubricity was illustrated by tests conducted with kerosene on High Frequency Reciprocating Rig. Therefore, HFRR tests were performed with fatty acid methyl esters of sunflower, palm, cotton-seed, tobacco-seed, olive, rape-seed and used frying oils, at volume concentrations from 0.05% to 0.6%. This study showed that the biodiesels used, produced a significant decrease in the wear scar diameter at concentrations of 0.2% to 0.4 %. Biodiesels derived from non-polyunsaturated oils, such as palm and olive gave better lubrication at certain concentrations.

Research and development studies regarding the internal combustion engines are, now more than ever, crucial in order to prevent a premature disposal for this application. An innovative technology is analyzed in this paper. The traditional slider-crank mechanism is replaced by a system of two ring-like elements crafted in such a way to transform the rotating motion of one element in the reciprocating motion of the other. This leads both to a less complex engine architecture and to the possibility to obtain a wide range of piston laws by changing the profile of the two cams. The relative motion of the cams is the peculiar feature of this engine and, due to this, alongside with the thermodynamic analysis, also the tribological aspects are investigated. 3D-CFD simulations are performed for several piston laws at different engine speeds to evaluate the cylinder pressure trace to be used as input data for the development of the tribological model.

In this work, a quasi-dimensional, multi-zone combustion model is analytically presented, for the prediction of performance and nitric oxide (NO) emissions of a homogeneous charge spark ignition (SI) engine, fueled with biogas-H2 blends of variable composition. The combustion model is incorporated into a closed cycle simulation code, which is also fully described. Combustion is modeled on the basis of turbulent entrainment theory and flame stretch concepts. In this context, the entrainment speed, by which unburned gas enters the flame region, is simulated by the turbulent burning velocity of a flamelet model. A flame stretch submodel is also included, in order to assess the flame response on the combined effects of curvature, turbulent strain and nonunity Lewis number mixture. As far as the burned gas is concerned, this is treated using a multi-zone thermodynamic formulation, to account for the spatial distribution of temperature and NO concentration inside the burned volume.

Mandated pollutant emission levels are shifting light-duty vehicles towards hybrid and electric powertrains. Heavy-duty applications, on the other hand, will continue to rely on internal combustion engines for the foreseeable future. Hence there remain clear environmental and economic reasons to further decrease IC engine emissions. Turbocharged diesels are the mainstay prime mover for heavy-duty vehicles and industrial machines, and transient performance is integral to maximizing productivity, while minimizing work cycle fuel consumption and CO2 emissions. 1D engine simulation tools are commonplace for “virtual” performance development, saving time and cost, and enabling product and emissions legislation cycles to be met. A known limitation however, is the predictive capability of the turbocharger turbine sub-model in these tools.

The objective of this work was the assessment of aliphatic amines and tertiary dialkyl-amides as lubrication additives or extenders, on ultra - low sulfur diesel fuels. In order to evaluate the influence of two types of nitrogen compounds on the lubrication properties of ultra - low sulfur diesel fuels, nine distillation fractions produced by atmospheric distillation of a hydrotreated diesel fuel, were used as the base fuels. Five aliphatic amines and two tertiary amides were used as lubricating additives at five different concentrations i.e. 0.5, 1.0, 2.0, 4.0 and 6.0% by volume, on the nine base fuels. Tribological experiments were carried out on the High frequency Reciprocating test Rig (HFRR). The wear results showed that only four of the five aliphatic amines used, provide satisfactory HFRR mean wear scar diameter (WS 1.4) of less than 460 microns, and at the concentration levels of 1-2% by volume. The concentration levels below 1 % by volume had no effect on the fuel lubricity.

Thermodynamic, dynamic and design parameters have a significant and often conflicting impact on the transient response of a compression ignition engine. Knowing the contribution of each parameter on transient operation could direct the designer to the appropriate measures for better engine performance. To this aim an explicit simulation program developed is used to study the performance of a turbocharged diesel engine operating under transient load conditions. The simulation developed, based on the filling and emptying approach, provides various innovations as follows: Detailed analysis of thermodynamic and dynamic differential equations, on a degree crank angle basis, accounting for the continuously changing nature of transient operation, analysis of transient mechanical friction, and also a detailed mathematical simulation of the fuel pump. Each equation in the model is solved separately for every cylinder of the 6-cylinder diesel engine considered.

Pollutant emissions and specifically NO and soot are one of the most important problems that engineers have to face when developing heavy duty DI diesel engines. Two main strategies exist as options for their control, reduction inside the engine cylinder using advanced combustion and fuel injection technologies and use of after-treatment systems. In the present work it is examined the use of EGR to control the formation of NO inside the cylinder of an engine with extremely high peak pressure. The work is applied on a single cylinder truck test engine developed under a project funded by the European Community focusing on the improvement of heavy duty DI diesel engine efficiency using increased injection timing. Use is made of a simulation model to predict the effect of more advanced injection timing on engine performance and emissions. The model has been modified to include the effect of EGR used to c ontrol the formation of NO which is considerably increased at high injection timings.

The transient operation of turbocharged diesel engines during turbocharger compressor surging is investigated through simulation. This form of compressor dynamic instability can generate large amplitude compressor mass flow and pressure rise oscillations, sometimes leading even to flow reversals, and may also induce severe torsional loading to the turbocharger shaft. A model predicting the dynamic behavior of the engine air-charging system when compressor surging occurs was developed in conjunction with a linearized quasi-steady diesel engine simulation code. This analysis possesses the advantage over the more detailed engine codes of basic simplicity, speed of calculation and no need of many engine and turbocharger components parameters given as input data. Emphasis is given to the correct modeling of the physics of the phenomena concerned. Transient operation runs, including critical cases for surging initiation, were applied for two similar six-cylinder diesel engines.

A comprehensive set of computational and experimental results for high- pressure diesel sprays are presented and discussed. The test cases investigated include injection of diesel into air under both atmospheric and high pressure/temperature chamber conditions, injection against pressurized and cross-flowing CF6 simulating respectively the density and flow conditions of a diesel engine at the time of injection, as well as injection into the piston bowl of both research and production turbocharged high-speed DI diesel engines. A variety of high-pressure injection systems and injector nozzles have been used including mechanical and electronic high-pressure pumps as well as common-rail systems connected to nozzles incorporating a varying number of holes with diameters ranging from conventional to micro-size.

The use of twin-scroll turbocharger turbine in automotive powertrain has been known for providing better transient performance over conventional single-scroll turbine. This has been accredited to the preservation of exhaust flow energy in the twin-scroll volute. In the current study, the performance comparison between a single and twin-scroll turbine has been made experimentally on a 1.5L passenger car gasoline engine. The uniqueness of the current study is that nearly identical engine hardware has been used for both the single and twin-scroll turbine volutes. This includes the intake and exhaust manifold geometry, turbocharger compressor, turbine rotor and volute scroll A/R variation trend over circumferential location. On top of that, the steady-state engine performance with both the volutes, has also been tuned to have matching brake torque.

The use of twin-scroll turbocharger turbines has gained popularity in recent years. The main reason is its capability of isolating and preserving pulsating exhaust flow from engine cylinders of adjacent firing order, hence enabling more efficient pulse turbocharging. Asymmetrical twin-scroll turbines have been used to realize high pressure exhaust gas recirculation (EGR) using only one scroll while designing the other scroll for optimal scavenging. This research is based on a production asymmetrical turbocharger turbine designed for a heavy duty truck engine of Daimler AG. Even though there are number of studies on symmetrical twin entry scroll performance, a comprehensive modeling tool for asymmetrical twin-scroll turbines is yet to be found. This is particularly true for a meanline model, which is often used during the turbine preliminary design stage.

In the Big Data era, the capability in statistical and probabilistic data characterization, data pattern identification, data modeling and analysis is critical to understand the data, to find the trends in the data, and to make better use of the data. In this paper the fundamental probability concepts and several commonly used probabilistic distribution functions, such as the Weibull for spectrum events and the Pareto for extreme/rare events, are described first. An event quadrant is subsequently established based on the commonality/rarity and impact/effect of the probabilistic events. Level of measurement, which is the key for quantitative measurement of the data, is also discussed based on the framework of probability. The damage density function, which is a measure of the relative damage contribution of each constituent is proposed. The new measure demonstrates its capability in distinguishing between the extreme/rare events and the spectrum events.

The Ahmed Body is one of the most widely studied bluff bodies used for automotive conceptual studies and Computational Fluid Dynamics - CFD software validation. With the advances of the computational processing capacity and improvement in cluster costs, high-fidelity turbulence models, such as Detached Eddies Simulation – DES and Large Eddies Simulation – LES, are becoming a reality for industrial cases, as studied by BUSCARIOLO et al. (2016) [4], evaluating DES models to automotive applications. This work presents a correlation study between a computational and physical model of an Ahmed Body with slant angle of 0 degree, also known as a squared back. Physical results are from a wind tunnel test, performed by STRACHAN et al. (2007) [11] considering moving ground and Reynolds number of 1.7M, based on the length of the body.

Simulation models are widely used from research engineers to investigate the combustion mechanism of DI diesel engines. These models can be used, as tools to either comprehend information provided by experimental data or to perform predictions and assist the development process. As widely recognized a valuable source of information for engine performance and emissions studies is the cylinder pressure trace. It can provide after processing information concerning the combustion rate of fuel injected inside the combustion chamber. Often it is also used to calibrate simulation models or even to derive correlations to represent the combustion rate of fuel inside the combustion chamber. The present research team has during the development process of a simulation model for the description of DI diesel engine performance and emissions realized that there exists a serious problem.

During the last years a great effort has been made by many NATO nations to move towards the use of one military fuel for all the land-based military aircraft, vehicles and equipment employed on the military arena. This idea is known to as the Single Fuel Concept (SFC). The fuel selected for the idea of SFC is the JP-8 (F-34) military aviation fuel which is based upon the civil jet fuel F-35 (Jet A-1) with the inclusion of military additives possessing anti-icing and lubricating properties. An extended experimental investigation has been conducted in the laboratory of Thermodynamic and Propulsion Systems at the Hellenic Air Force Academy. This investigation was conducted with the collaboration of the respective laboratories of National Technical University of Athens and Hellenic Naval Academy as well.