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The development of modern autonomous automotive technology depends heavily on the reliable performance of external sensors that are vulnerable to soiling. Existing active cleaning devices, such as washers and wipers, are relatively complex and expensive. Furthermore, little research has been done on alternative soiling mitigation strategies and devices for sensors. With the emerging trend of replacing side-mirrors with camera monitor systems, it is important for such systems to stay clean in adverse weather in order to provide critical navigation information. To meet this need, a passive aerodynamics-based cleaning device was investigated. A converging vent device was integrated into the side-camera housing and the subsequent degree of soiling was estimated at a wind speed of 20 m/s (72 km/h), representing urban and suburban driving speeds. The vent outlet height and outlet jet angle of the vent device were varied and the variants were compared to the non-vented reference model.

In this paper, we develop a methodology to enable the isolation of the heat release contribution of knocking combustion from flame-propagation combustion. We first address the empirical modeling of individual non-autoigniting combustion history using the Wiebe function, and subsequently apply this methodology to investigate the effect of autoignition on the heat release history of knocking cycles in a spark ignition (SI) engine. We start by re-visiting the Wiebe function, which is widely used to model empirically mass burned histories in SI engines. We propose a method to tune the parameters of the Wiebe function on a cycle-by-cycle basis, i.e., generating a different Wiebe to suitably fit the heat release history of each cycle. Using non-autoigniting cycles, we show that the Wiebe function can reliably simulate the heat release history of an entire cycle, if only data from the first portion of the cycle is used in the tuning process.

The objective of this study is to increase fundamental understanding of the effects of fuel composition and properties on low temperature combustion (LTC) and to identify major properties that could enable engine performance and emission improvements, especially under high load conditions. A series of experiments and computational simulations were conducted under LTC conditions using 67% EGR with 9.5% inlet O₂ concentration on a single-cylinder version of the General Motors Corporation 1.9L direct injection diesel engine. This research investigated the effects of Cetane number (CN), volatility and total aromatic content of diesel fuels on LTC operation. The values of CN, volatility, and total aromatic content studied were selected in a DOE (Design of Experiments) fashion with each variable having a base value as well as a lower and higher level. Timing sweeps were performed for all fuels at a lower load condition of 5.5 bar net IMEP at 2000 rpm using a single-pulse injection strategy.

The effects of changes in fuel spray cone angle, number of spray holes, nozzle hole area, nozzle tip protrusion, compression ratio, swirl level, and injection timing on Diesel combustion and emissions were investigated at three engine operating conditions using Taguchi design of experiment methods. The effects of changes in these design parameters on the ignition delay (ID), premixed combustion fraction (PCF), premixed combustion index (PCI), and diffusion combustion index (DCI) were examined along with their effects on particulates, NOx, hydrocarbons, and smoke emissions. The key design parameters affecting both the combustion process and the exhaust emissions were identified, and qualitative as well as quantitative relationships between the design parameters, combustion parameters, and exhaust emissions were established.

Increasingly stringent emission requirements for heavy-duty diesel engines stresses the importance of both engine design and diesel fuel quality. The Coordinating Research Council sponsored this test work to yield quantitative emission data and emission models to relate diesel fuel properties to emissions from modern heavy-duty diesel engines. Regulated and selected unregulated emissions from three engines were measured over the EPA transient test procedure using several fuels having controlled variation in three primary fuel properties: aromatics, volatility (as the 90 percent boiling point temperature), and sulfur. Models for transient composite emissions were obtained using multiple linear regression techniques, and changes to regulated emissions for selected changes in fuel properties were estimated from the models. Of the three primary fuel variables, aromatic content and volatility were significant for emissions of HC, CO, and NOx.

Fuel spray-wall interaction frequently occurs on intake manifold wall in the port fuel injection engine and on the piston in the direct injection engine, especially during the cold start. The heat transfer between the spray and wall is involved in this interaction process and influences the dynamics of the impinged spray which can further affect the engine performance. The physics of impact dynamics of a single droplet serves as a fundamental for better comprehension of spray impingement. In our previous studies, we have focused on diesel droplets, at ambient temperature, impinging on both heated and non-heated wall and found impinged droplet morphology differences. To understand the effect of heat transfer and thermophysical properties on dynamics of droplet-wall interaction better, droplet temperature variation was introduced in this study. Therefore, different conditions were framed to explore the impact of thermophysical properties of the droplet.

The effects of various injection timing of methanol on thermo-atmosphere combustion of methanol by port injection of dimethyl ether (DME) and direct injection of methanol were experimentally investigated. The experiment results show that, as injection timing is at 6 degree before TDC, the combustion process comprises three stages: low temperature heat release of DME, high temperature heat release of DME and diffusion combustion of methanol. As injection timing increases, premixed combustion proportion of methanol is increased and diffusion combustion proportion is decreased. As injection timing increases to 126 degree before TDC, diffusion combustion of methanol disappears. At this time, the combustion process shows typical two stages heat release of HCCI combustion. As injection timing increases, required DME rate is increased, combustion efficiency and indicated thermal efficiency all first increase and then decrease.

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.