汽车发动机多参量测试系统

Formaldehyde (CH2O) is an important intermediate species in combustion processes and it can through laserinduced fluorescence measurements be used for instantaneous flame front detection. The present study has focussed on the use of the third harmonic of a Nd:YAG laser at 355 nm as excitation wavelength for formaldehyde, and different dimethyl ether (C2H6O) flames were used as sources of formaldehyde in the experiments. The investigations included studies of the overlap between the laser profile and the absorption lines of formaldehyde, saturation effects and the potential occurrence of laser-induced photochemistry. The technique was applied for detection of formaldehyde in an internal combustion engine operated both as a spark ignition engine and as a homogenous charge compression ignition engine.

采用LaVision公司的高速相机和多参量数据采集和分析处理软件平台DaVis，对柴油JP-8喷雾的性能进行了测量分析。获得了喷雾的米氏散射和纹影成像数据。

采用LaVision公司特色的以DaVis软件平台为基础构成汽车发动机时间分辨多参两成像测试系统，研究了确定火花辅助压缩点火过程中燃烧可变性原因所需要的实验度量指标。

采用LaVision公司特色的以DaVis软件平台为基础构成的粒子成像测速（PIV）系统对直接喷射火花塞引燃（DISI）引擎进气道产生的流动不稳定性进行了测试和研究。

采用LaVision公司特色的以DaVis软件平台和高速相机为基础构成的喷雾高速成像诊断测量系统（SprayMaster）对喷雾导引火花塞引燃直接喷射发动机（SGSIDI）内部燃料混合，注入等过程进行了测试和研究。

采用LaVision公司特色的以DaVis软件平台为基础构成的喷雾成像测试（SprayMaster）系统对喷射导引燃烧系统中另外一种点火系统的热动力学潜能进行了研究。

采用LaVision公司特色的以DaVis软件平台为基础构成的粒子成像测速（PIV）和喷雾几何形态参数成像测试系统对燃料喷雾的形成和汽油燃料直接喷射（GDI）进行了测试和分析。

This paper deals with the experimental investigations of the in-cylinder tumble flows in an unfired internal combustion engine with a flat piston at the engine speeds ranging from 400 to 1000 rev/min., and also with the dome and dome-cavity pistons at an engine speed of 1000 rev/min., using particle image velocimetry. From the two-dimensional in-cylinder flow measurements, tumble flow analysis is carried out in the combustion space on a vertical plane passing through cylinder axis. To analyze the tumble flows, ensemble average velocity vectors are used and to characterize it, tumble ratio is estimated. From the results, generally, we have found that tumble ratio varies mainly with crank angle position. Also, at the end of compression stroke, average turbulent kinetic energy is more at higher engine speeds. We have also found that, at 330 crank angle position, flat piston shows an improvement of about 85 and 23% in tumble ratio, and about 24 and 2.5% in average turbulent kinetic energy compared to dome and dome-cavity pistons respectively.

Now-a-days, the stratified and direct injection spark ignition engines are becoming very popular because of their low fuel consumption and exhaust emissions. But, the challenges to them are the formation and control of the charge which is mainly dependent on the in-cylinder fluid flows. Today, an optical tool like particle image velocimetry (PIV) is extensively used for the in-cylinder fluid flow measurements. This paper deals with the experimental investigations of the in-cylinder fluid tumble flows in a motored internal combustion engine with a flat piston at different engine speeds during intake and compression strokes using PIV. The two-dimensional in-cylinder flow measurements and analysis of tumble flows have been carried out in the combustion space on a vertical plane at the cylinder axis. To analyze the fluid flows, ensemble average velocity vectors have been used. To characterize the tumble flow, tumble ratio has been estimated. From the results, it is found that the tumble ratio mainly varies with crank angle positions. At the end of compression stroke, maximum turbulent kinetic energy is more at higher engine speeds. Present study will be very useful in understanding the effect of engine speeds on the in-cylinder fluid tumble flows under real engine conditions.

In 1897 Rudolf Diesel (1858-1913) demonstrated a new type of internal combustion (i.c.) engine in which the high compression pressure of about 35 times the atmospheric pressure led to a sufficiently high temperature to cause the auto-ignition of kerosine. Ever since diesel engines remained popular owing to their relatively high efficiencies and their ability to combust a large variety of fuels predominantly containing heavier crude oil components (i.e., longer aliphatic hydrocarbon chains). The original engines were 4-stroke engines in which one complete engine cycle takes two revolutions of the crank shaft. The latter transforms the translational energy of the piston in the cylinder into more convenient rotational energy with respect to vehicle propulsion. As schematically depicted in figure 1.1, in the first stroke the piston moves downwards in the cylinder and ambient air is taken in above the piston (inlet stroke). In the second stroke the inlet valve is closed and the piston moves upwards compressing the intake air (compression stroke). Just before the piston reaches its Top Dead Centre (TDC) fuel is sprayed in the combustion chamber and combustion takes place driving the piston downwards again in the third stroke (expansion stroke). Finally, the exhaust valve opens and the piston moves upwards again in the fourth stroke (exhaust stroke) pushing the combustion gases out of the cylinder. In later years 2- stroke diesel engines were developed in which, by using the space of the crank case below the piston as well, the work usually done in four strokes is now performed by one revolution of the crank shaft. Around 1940 the first turbo-charging diesel engines were developed in which the energy contained in the exhaust gases is used to compress the intake air in order to boost the power of the engines.

The present work describes a new method which allows the spatially resolved quantitative determination of gaseous hydrocarbon densities in droplet laden flows. The technique is especially dedicated to a quantitative and linearly spatially resolved measurement of air/fuel ratio (λ-value) in direct injection Otto engines under stratified operation and by use of regular gasoline (Euro Super). The new method is based on spontaneous Raman scattering. It is applied to the investigation of the air/fuel ratio distribution inside and in the close surroundings of the spray cone of different DI-fuel injectors under stratified and homogeneous engine operation conditions. Both crank angle resolved snap shot and cyclical averaged measurements are presented. Simultaneously the planar gasoline distribution is detected by LIF of aromatic hydrocarbons which are native constituents of regular gasoline. It is shown, that the linear spatially resolved air/fuel distributions measured by means of LIF correlate well with the Raman data.

The effect on fuel consumption and emissions of switching from two-valve to single-valve EIVC operation in order to generate swirl intake structures in a four-valve, pent-roof gasoline direct injection (GDI) engine has been investigated. Mie imaging of the fuel spray propagation, along with PIV measurements of the intake flow field have been taken in an optical engine, and fuel economy and emissions measurements have been made on a thermodynamic engine with identical geometry and ancillary systems. The measurements show that fuel economy can be improved substantially when EIVC valve operation is employed, and results differ when only a single inlet valve is activated. Bulk swirl structures are generated in the engine cylinder which affect the atomisation and transportation of the fuel spray and engine performance. For fuel injection after the inlet valve closing point, the reduction in shear forces and mixing from the intake air structures is sufficient to cause engine misfires.

To achieve PCCI combustionwith limited heat release rates, the influence of charge stratification on combustion should be investigated. In this paper a method is presented to achieve and measure charge stratification. As a first attempt to investigate the mixing, we measure the in-cylinder velocities using particle image velocimetry (PIV). From these velocities the turbulence intensities are derived, which give an indication of the mixing of charge. First results indicate that the turbulence is homogeneous and that the swirl center shifts towards the center of the combustion chamber. Future measurements will also entail time resolved PIV measurements.

采用LaVision公司的增强型CCD相机对火焰喷射对象进行了测量。研究了喷嘴直径对火焰举升长度的影响。

采用LaVision公司的科研型CCD相机和智能成像系统，对酒精喷雾的几何参量进行了实时测量。和1维拉曼散射测量相结合，提供了对喷雾对象，多视角，多参量的测量和表征

A concept for dynamic mixture formation investigations of fuel/air mixtures is presented which can equally be applied to several other laser induced fluorescence (LIF) applications. Double-pulse LIF imaging was used to gain insight into dynamic mixture formation processes. The setup consists of a modified standard PIV setup. The ‘‘fuel/air ratio measurement by laser induced fluorescence (FARLIF)’’ approach is used for a quantification of the LIF images in order to obtain pairs of 2D fuel/air ratio maps. Two different evaluation concepts for LIF double pulse images are discussed. The first is based on the calculation of the temporal derivative field of the fuel/air ratio distribution. The result gives insight into the dynamic mixing process, showing where and how the mixture is changing locally. The second concept uses optical flow methods in order to estimate the motion of fluorescence (i.e., mixture) structures to gain insight into the dynamics, showing the distortion and the motion of the inhomogeneous mixture field.

1.The HARVEST Project 2.2D-2C PIV Measurements 3.NumericalComputation 4.Results 1.ComparisonsPIV / CFD 2.Characterizationof dynamicstall 5.Conclusions ---------------------------------------------------------- Objective:Convertcineticenergyof riversor of tidal flow Specificity:Vertical axis turbine, radial flux, new generationof Darrieusand Gorlovturbine

In this report we present the methodology we are using in the AMI group to compare optic flow estimation methods in the context of the FLUID Specific Targeted Research Project - Contract No 513633 founded by the CEE. The main goal of this report is to try to unify comparison criteria between the different parnerts in order to share information and conclusions. We think that it is one of the topics we have to address in Las Palmas Meeting December next. In order to describe the methodology we use, we divide it in five steps: 1. We choose a number of optic flow estimation methods 2. We choose an image sequence dataset to apply the methods. 3. We apply the methods and we store the results in a ASCII file using an standard format 4. We define a number of statistics to compare the methods (we use the ASCII files as basic information to compare). 5. We compute the statistics for each pair of methods and we generate tables with the information. To help result interpretation we use arrow images and in the case we know the optic flow groundtruth we generate image to provide the information about what method perform better in the different areas of the image. To illustrate this approach and to fit ideas we present the results of this approach in a particular image sequence provided by LaVision in sections from 1.1 to 1.4. Then, in section 2 we remark some of the difficulties we have found in our work, which should be discussed in order to be able to compare results provided by all the partners of the FLUID project.

To understand and optimize the combustion processes in new types of internal combustion engines, like gasoline direct-injection engines, non-intrusive laser-based diagnostics methods have proven to be versatile and important tools to measure combustion characteristics. Most engine developers already rely on optical methods in the development of new engines. To guarantee accurate and reliable results of optical measurements it is necessary to carefully evaluate and characterize these techniques under realistic conditions. In this work a variety of laser-based diagnostics techniques, mostly based on the tracer- LIF principle, have been evaluated for their applicability and limitations and have been applied to different spray systems – reaching from single droplets, over model sprays to fuel sprays in a firing test engine. The tracer-laser-induced-fluorescence (LIF) method is based on doping the fuel with a fluorescent substance whose fluorescence characteristics are used to measure various physical properties of the spray, such as temperature, droplet size, or droplet velocity. From these properties information about heat and mass-transfer mechanisms in the spray can be gained. However, the characteristics of the used tracers must be known in detail in order to guarantee useful and comparable results. Therefore, in this work various tracers were characterized in terms of their evaporation and temperaturedependent properties. The tracers Atto 680, Rhodamine 800 and Rhodamine B have further been tested for their applicability to realistic fuels.