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Road safety is one of the major concerns for automated vehicles. In order for these vehicles to interact safely and efficiently with the other road participants, the behavior of the automated vehicles should be carefully designed. Liu and Tomizuka proposed the Robustly-safe Automated Driving system (ROAD) which prevents or minimizes occurrences of collisions of the automated vehicle with other road participants while maintaining efficiency. In this paper, a set of design principles are elaborated as an extension of the previous work, including robust perception and cognition algorithms for environment monitoring and high level decision making and low level control algorithms for safe maneuvering of the automated vehicle.

Gasoline direct injection engines can greatly improve the fuel economy, but the idea mixture distribution cannot be easily controlled. In this paper, the linearized instability sheet atomization (LISA) and large eddy simulation (LES) implemented into KIVA-3V code were used to study the gasoline hollow cone spray process for gasoline direct injection (GDI) in a constant volume vessel. The three-dimensional results show that the LISA model can effectively simulate the gasoline hollow cone spray and obtain the string structure compared to the experiment data. And the velocity interpolation method can reduce the grid dependency of spray simulation. Using dense grid (about 8 million cells) in LES and RANS all can obtain the good spray tip penetration and width. Unlike diesel spray, for gasoline spray there are not big difference between the results using LES and RANS. In additional the ambient pressure significantly influence the gasoline spray shape.

In this work, large eddy simulation (LES) with a K-equation subgrid turbulent kinetic energy model is implemented into the CFD code KIVA3V to study the features of liquid fuel spray and combustion using gradually varying grid in a constant volume chamber. The characteristic time-scale combustion model (CTC) incorporating a turbulent timescale is adopted to predict the combustion process and the SHELL auto-ignition model is used to predict auto-ignition. Combustion is also simulated using Parallel Detailed Chemistry with Lu's n-heptane reduced mechanism (58 species), which has been added into the KIVA3V-LES code. The computational results are compared with Sandia experimental data for non-reacting and reacting cases. As a result, LES can capture the complex structure of the spray and temperature distribution as well as the trend of ignition delay and flame lift-off length variations. Better results are obtained using the Parallel Detailed Chemistry than the CTC model.

Robust control of combustion phasing in Homogenous Charge Compression Ignition (HCCI) engines is a well-recognized challenge limiting the automotive industry for exploiting HCCI benefits in mass production vehicles. Real-time model-based control of combustion phasing is the key to tackle this daunting challenge. In this paper, a new control oriented model is developed for predicting HCCI combustion phasing over a range of engine operation. The model is validated against the experimental data from a single cylinder Ricardo engine. A model-based integral state feedback controller is designed to control HCCI combustion phasing by modulating the ratio of two Primary Reference Fuels (PRFs). The controller's performance is compared with a manually tuned proportional integral controller.

This study presents the development of a new HCCI simulation methodology. The proposed method is based on the sequential coupling of CFD analysis prior to autoignition, followed by multi-zone chemical kinetics analysis of the combustion process during the closed valve period. The methodology is divided into three steps: 1) a 1-zone chemical kinetic model (Chemkin Pro) is used to determine either the intake conditions at IVC to achieve a desired ignition timing or the ignition timing corresponding with given IVC conditions, 2) the ignition timing and IVC conditions are used as input parameters in a CFD model (Fluent 6.3) to calculate the charge temperature profile and mass distribution prior to autoignition, and 3) the temperature profile and mass distribution are fed into a multi-zone chemical kinetic model (Chemkin Pro) to determine the main combustion characteristics.

Accelerated market penetration of plug-in electric vehicles (PEVs) is presently restricted by the high cost of batteries. Deployment of grid-connected energy storage, which could increase the reliability, efficiency, and cleanliness of the grid, is similarly inhibited by the cost of batteries. Research, development, and manufacturing are underway to reduce cost by lowering material costs, enhance process efficiencies, and increase production volumes. Another approach under consideration is to recover a fraction of the battery cost after the battery has been retired from vehicular service via reuse in other applications, where it may still have sufficient performance to meet the requirements of other energy-storage applications.

This paper presents a large eddy simulation study of the liquid spray mixing with hot ambient gas in a constant volume vessel under engine-like conditions with the injection pressure of 1500 bar, ambient density 22.8 kg/m₃, ambient temperature of 900 K and an injector nozzle of 0.09 mm. The simulation results are compared with the experiments carried out by Pickett et al., under similar conditions. Under modern direct injection diesel engine conditions, it has been argued that the liquid core region is small and the droplets after atomization are fine so that the process of spray evaporation and mixing with the air is controlled by the heat and mass transfer between the ambient hot gas and central fuel flow. To examine this hypothesis a simple spray breakup model is tested in the present LES simulation. The simulations are performed using an open source compressible flow solver, in OpenFOAM.

Material flammability is an important factor in determining the pressure and composition (fraction of oxygen and nitrogen) of the atmosphere in the habitable volume of exploration vehicles and habitats. The method chosen in this work to quantify the flammability of a material is by its ease of ignition. The ignition delay time was defined as the time it takes a combustible material to ignite after it has been exposed to an external heat flux. Previous work in the Forced Ignition and Spread Test (FIST) apparatus has shown that the ignition delay in the currently proposed space exploration atmosphere (approximately 58.6 kPa and 32% oxygen concentration) is reduced by 27% compared to the standard atmosphere used in the Space Shuttle and Space Station.

The paper describes a novel method for calculating the residual gas fraction and the trapping efficiency in a 2 stroke engine. Assuming one dimensional compressible flow through the inlet and exhaust ports, the method estimates the instantaneous mass flowing in and out from the combustion chamber; later the residual gas fraction and trapping efficiency are estimated combining together the perfect displacement and perfect mixing scavenging models. It is assumed that when the intake port opens, the fresh mixture is pushing out the burned charge without any mixing and after a multiple of the time needed for the largest eddy to perform one rotation, the two gasses are instantly mixed up together and expelled. The result is a very simple algorithm that does not require much computational time and is able to estimate with high level of precision the trapping efficiency and the residual gas fraction in 2 stroke engines.

It has been known from multi-zone simulations that HCCI combustion can be significantly affected by temperature stratification of the in-cylinder gas. With the same combustion timing (i.e. crank angles at 50% heat release, denoted as CA50), large temperature stratification tends to prolong the combustion duration and lower down the in-cylinder pressure-rise-rate. With low pressure-rise-rate HCCI engines can be operated at high load, therefore it is of practical importance to look into more details about how temperature stratification affects the auto-ignition process. It has been realized that multi-zone simulations can not account for the effects of spatial structures of the stratified temperature field, i.e. how the size of the hot and cold spots in the temperature field could affect the auto-ignition process. This question is investigated in the present work by large eddy simulation (LES) method which is capable of resolving the in-cylinder turbulence field in space and time.

Nowadays for small-scale power generation there are electrochemical batteries and mini engines. Many efforts have been done for improving the power density of the batteries but unfortunately the value of 1 MJ/kg seems to be asymptotic. If the energy source is an organic fuel which has an energy density of around 29 MJ/kg with a minimum overall efficiency of only 3.5%, this device would surpass the batteries. This paper is the fifth of a series of publications aimed to study the HCCI combustion process in the milli domain at high engine speed in order to design and develop VIMPA, Vibrating Microengine for Low Power Generation and Microsystems Actuation. Previous studies ranged from general characterization of the HCCI combustion process by using metal and optical engines, to more specific topics for instance the influence of the boundary layer and quenching distance on the quality of the combustion.

Power supply systems play a very important role in applications of everyday life. Mainly, for low power generation, there are two ways of producing energy: electrochemical batteries and small engines. In the last few years many improvements have been carried out in order to obtain lighter batteries with longer duration but unfortunately the energy density of 1 MJ/kg seems to be an asymptotic value. If the energy source is an organic fuel with an energy density of around 29 MJ/kg and a minimum overall efficiency of only 3.5%, this device can surpass the batteries. Nowadays the most efficient combustion process is HCCI combustion which is able to combine high energy conversion efficiency and low emission levels with a very low fuel consumption. In this paper, an investigation has been carried out concerning the effects of the compression ratio on the performance and emissions of a mini, Vd = 4.11 [cm3], HCCI engine fueled with diethyl ether.

In HCCI you do not have the same control of the combustion like in SI and Diesel engines. Controlling the start of a combustion event is a difficult task and requires feedback from previous cycles. This feedback can be retrieved from ion current measurements. By applying a voltage over the spark gap, ions will lead a current and a signal that represents the combustion in the cylinder will be retrieved. Voltages of 450 V were used. The paper describes a new method to enhance the combustion phasing from the Ion current trace in HCCI engines. The method is using the knowledge of how the signal should look. This is known due to the fact that the shape of the ion current signal is similar from cycle to cycle. This new observation is shown in the paper. Also the correlation between the ion current and CA50 was studied. Later the signals have been used for combustion feedback.

Power supply systems play a very important role in everyday life applications. There are mainly two ways of producing energy for low power generation: electrochemical batteries and small engines. In the last few years, many improvements have been carried out in order to obtain lighter batteries with longer durations but unfortunately the energy density of 1 MJ/kg seems to be an asymptotic value. An energy source constituted of an organic fuel with an energy density around 29 MJ/kg and a minimum overall efficiency of only 3.5% could surpass batteries. Nowadays, the most efficient combustion process is HCCI combustion which has the ability to combine a high energy conversion efficiency with low emission levels and a very low fuel consumption. The present paper describes an investigation carried out on a modified model airplane engine, on how a pure HCCI combustion behaves in a small volume, Vd = 4.11 cm3, at very high engine speeds (up to 17,500 [rpm]).

Nowadays the power supplying systems have a fundamental importance for all small and portable devices. For low power applications, there are two main ways for producing power: electrochemical batteries and mini engines. Even though in recent years many developments have been carried out in improving the design of batteries, the energy density of 1MJ/kg seems to be an asymptotic value. If the energy source is a hydrocarbon fuel, whose energy density is 46 MJ/kg, with an overall efficiency of only 2.5 % it is possible to surpass the electrochemical batteries. On the other hand, having a mini engine, as energy source, implies three main problems: vibrations, noise and emissions. A light (230 g) model airplane engine with a displacement volume of 4.11 cm3 and a geometrical compression ratio of 13.91 has been studied. The work carried out in this paper can be divided basically in three parts.

The main benefit of HCCI engines compared to SI engines is improved fuel economy. The drawback is the diluted combustion with a substantially smaller operating range if not some kind of supercharging is used. The reasons for the higher brake efficiency in HCCI engines can be summarized in lower pumping losses and higher thermodynamic efficiency, due to higher compression ratio and higher ratio of specific heats if air is used as dilution. In the low load operating range, where HCCI today is mainly used, other parameters as friction losses, and cooling losses have a large impact on the achieved brake efficiency. To initiate the auto ignition of the in-cylinder charge a certain temperature and pressure have to be reached for a specific fuel. In an engine with high in-cylinder cooling losses the initial charge temperature before compression has to be higher than on an engine with less heat transfer.

Autoignition of a homogeneous mixture is very sensitive to operating conditions, therefore fast control is necessary for reliable operation. There exists several means to control the combustion phasing of an Homogeneous Charge Compression Ignition (HCCI) engine, but most of the presented controlled HCCI result has been performed with single-input single-output controllers. In order to fully operate an HCCI engine several output variables need to be controlled simultaneously, for example, load, combustion phasing, cylinder pressure and emissions. As these output variables have an effect on each other, the controller should be of a structure which includes the cross-couplings between the output variables. A Model Predictive Control (MPC) controller is proposed as a solution to the problem of load-torque control with simultaneous minimization of the fuel consumption and emissions, while satisfying the constraints on cylinder pressure.

Heavy trucks contribute significantly to the overall air pollution, especially NOx and PM emissions. Models to predict the emissions from heavy trucks in real world on road conditions are therefore of great interest. Most such models are based on data achieved from stationary measurements, i.e. engine maps. This type of “quasi stationary” models could also be of interest in other applications where emission models of low complexity are desired, such as engine control and simulation and control of exhaust aftertreatment systems. In this paper, results from quasi stationary calculations of fuel consumption, CO, HC, NOx and PM emissions are compared with time resolved measurements of the corresponding quantities. Measurement data from three Euro 3-class engines is used. The differences are discussed in terms of the conditions during transients and correction models for quasi stationary calculations are presented. Simply using engine maps without transient correction is not sufficient.

In this paper the combustion chamber wall temperature was measured by the use of thermographic phosphor. The temperature was monitored over a large time window covering a load transient. Wall temperature measurement provide helpful information in all engines. This temperature is for example needed when calculating heat losses to the walls. Most important is however the effect of the wall temperature on combustion. The walls can not heat up instantaneously and the slowly increasing wall temperature following a load transient will affect the combustion events sucseeding the transient. The HCCI combustion process is, due to its dependence on chemical kinetics more sensitive to wall temperature than Otto or Diesel engines. In depth knowledge about transient wall temperature could increase the understanding of transient HCCI control. A “black box” state space model was derived which is useful when predicting transient wall temperature.

A five-cylinder diesel engine, converted to a single cylinder operated optical engine is run in Homogeneous Charge Compression Ignition (HCCI) mode. A blend of iso-octane and n-heptane is used as fuel. An experimental study of the horizontal boundary layer between the main combustion and the non-reacting surface of the combustion chamber is conducted as a function of speed, load, swirl and injection strategy. The combustion behaviour is monitored by chemiluminescence measurements. For all cases an interval from -10 to 16 crank angles after top dead center (CAD ATDC) in steps of one CAD are studied. One image-intensified camera observes the boundary layer up close from the side through a quartz cylinder liner while a second camera has a more global view from below to see more large scale structure of the combustion. The averaged chemiluminescence intensity from the HCCI combustion is seen to scale well with the rate of heat release.