【作者】 孙跃国；

【导师】 袁兆成；

【作者基本信息】 吉林大学 ， 动力机械及工程， 2012， 博士

【摘要】 随着汽车工业的高速发展，对发动机技术的要求也越来越高。提高发动机的燃油利用率，从而提高发动机的经济性和动力性，一直是当前科研人员研究的核心问题。然而对于汽油发动机而言，由于汽油本身的燃烧特性和汽油发动机工作原理方面的限制，在提升汽油发动机性能的过程中，伴随而来的严重问题就是发动机的爆震，目前爆震问题已经变成了严重制约汽油发动机性能的突出问题。为了解决汽油发动机的爆震问题，首先要做的是精确地检测出发动机是否存在爆震，然后要做的是消除爆震。而最好是能精确地控制发动机工作于爆震与非爆震的临近状态，这样发动机的动力性和经济性才是最好的。以往所采用的爆震检测手段存在着精度差、造价高、寿命短、无法判断多缸机的爆震缸等问题。由于爆震检测手段的不足，大大限制了爆震控制系统的控制精度，也限制了汽油发动机性能的提高。本论文提出了采用火花塞离子流信号检测爆震的方法，该检测方法克服了其他爆震检测方法的不足，具有精度高、造价低、使用寿命长、可实现爆震的单缸检测等优点，为爆震检测方法提供了一个新的研究方向。在论文中，针对离子流信号的检测方法、离子流信号的影响因素、爆震强度与离子流信号的关系、哈尔小波在离子流信号识别爆震过程中的运用等问题，进行了深入细致的研究，并得出了相关的结论。在本论文中主要研究了以下几方面工作近年来虽然研究离子流的学者和团队较多，但是由于离子流的检测手段方面的限制，导致对于离子流信号的分析没能够更加深入地进行。要想检测出稳定可靠的离子流信号，首先必须要优化离子流的检测电路，控制离子流信号的幅度和信噪比在我们满意的范围之内，这也是后续信号分析的前提条件；再有，就是要在发动机上制造出我们所需要的、较为理想的、稳定的实验工况和实验条件，以便能够完成实验。这两项工作看似简单，实则是全部工作的基础，后面的全部工作都是在这一基础之上展开的。1、优化了离子流信号的采集电路，实现了离子流信号的低噪声采集。实验过程中所采集的离子流信号稳定，高压干扰小，离子流信号采集系统可以非常稳定地工作。在发动机相同工况的不同工作循环，离子流信号波形的重复性好，使得离子流信号的测量有了突破性的进展。2、研究了火花塞参数对于离子流信号的影响问题。火花塞作为发动机高压点火系统与离子流信号采集系统的交叉点，其参数变化对于离子流信号的影响问题变得很重要。论文中，对三种不同参数火花塞的离子流信号进行了对比研究，得出了相应的结论。3、研究了汽油辛烷值对离子流信号的影响问题。发动机采用不同辛烷值的汽油时，所测得的离子流信号也是不同的，在实验中，选用低辛烷值的燃油，引发发动机爆震，对于所测得的离子流信号进行了分析，得到了离子流信号在采用低辛烷值燃油时的幅度特性和幅度积分特性。4、研究了离子流信号检测电路不同偏置电压对于离子流信号的影响问题。在实际当中，我们必须弄清楚偏置电压对于离子流信号的影响问题，以便于控制离子流信号幅度，使之满足我们后续信号处理的要求。实验中，分别采用350V和700V两种偏置电压，在两种偏置电压条件下测得离子流信号，进行了对比分析。5、研究了不同爆震强度下的离子流幅度特征。本文的核心内容是利用离子流信号进行爆震的检测与控制，因此必须找到离子流信号与发动机爆震之间的关系。在发动机转速1800r/min条件下，分别在油门开度大约21%（扭矩大约70Nm）、油门开度大约20%（扭矩大约60Nm）、油门开度大约19%（扭矩大约50Nm）、油门开度大约18%（扭矩大约40Nm）四种负荷条件下，分别测量离子流信号。在信号分析过程中，为了便于进行爆震与非爆震情况下离子流信号的对比，首先要将气缸内条件相似的工作循环放在一起进行归类，为此进行了缸压的区段划分。在不同工况点，对缸压从4.5MPa到2MPa之间，以0.5MPa为一档进行区段划分。分别对于相同缸压区段内以及不同区段内的离子流信号，进行幅度特征的分析对比，并得到了相应的结论。6、将小波的分析方法引入到离子流信号的分析当中。小波是近年来新兴的信号分析方法，是傅里叶变换的发展和延伸。论文结合离子流信号的特点，对于离子流信号进行了小波分析，所得到的结论大大优于离子流信号幅度分析法所得到的结论。本论文的主要创新点1、离子流检测电路的优化离子流检测电路的优化问题一直是困扰研究人员的重大技术问题，几十千伏点火高压的隔离问题如果处理不好，会使得离子流信号无法采集，严重的甚至会烧毁仪器。在实验的过程中，这一问题得到了彻底的解决，使得所测得的离子流信号干扰很小，信噪比足够满足要求，信号的幅度也可以随心所欲地控制在我们满意的范围。2、深入地研究了外界因素对离子流信号的影响问题火花塞参数、燃油辛烷值、离子流检测电路的偏置电压等外界的参数，是影响离子流信号的重要因素，本文深入地探讨了这些外界因素对于离子流信号的影响问题。3、深入地研究了不同爆震强度下离子流信号幅度的变化规律问题论文提出了对于缸压进行区段划分的全新的观点，通过对于缸压的区段划分，进一步完成对离子流信号特征进行归类，论文详细地阐述了离子流信号幅度与爆震的关系问题。4、将小波的分析方法引入到离子流的分析过程当中将哈尔小波运用到了离子流信号的分析中，实践证明，小波的分析方法是一种非常好的信号分析手段，这将对今后离子流信号的分析产生巨大的推动作用。今后的工作展望在今后的工作中尚需要进一步充实和完善的方面主要有：1、进一步完善实验条件由于条件所限，本文所涉及的大部分内容，均是利用缸压传感器来代替火花塞进行实验和数据采集的。由于缸压传感器与普通火花塞存在一定的差别，所以测试结果必然存在一定的局限性。要克服这些局限性，最好的办法是在气缸盖打眼，单独安装缸压传感器，同时安装普通的火花塞以便发动机工作。这样，利用缸压传感器测量缸压的变化情况，利用普通火花塞点火并测量离子流信号，这样一来，应该会使得实验结果更加接近于真实情况。2、在更多的工况点进行离子流的测试为了推广使用，还应在更多的工况点测量和分析离子流，以使得实验结果更具有普遍性的规律。更多还原

【Abstract】 Along with the development of the car industry, the requirement to the enginetechnology becomes higher and higher. It is the core issue of the study to the scientificresearchers that how to improve the engine’s fuel efficiency and engine performance. Asfar as gasoline engine is concerned, because of the combustion characteristic of gasolineand characteristics of gasoline engine working principle, during the process ofimproving the engine performance which makes the question that the petrol engineknock has become both inevitable and the outstanding problems which at the same time,severely restricts the engine’s performance. In order to solve the problem of the gasolineengine detonation, the first thing to do is testing accurately whether the engine knocksor not, and then is eliminating the detonation. And the best thing is controlling thecritical state between knock and non knock when the engine is working, so the engineperformance and the fuel economy are in the best state. Past means of knockingdetection has the problem of poor precision, high costing, short life, and cannot judgemulti cylinder machine knock cylinder, etc. Because of the shortage of the detectionmeans, the precision of the knocking control system and the improvement of gasolineengine performance are being limited overall.This paper presents the method of knock detection by the spark plug ion flow,which overcomes the shortcomings of other methods, and has high precision, low cost,long service life, and able to realize the single cylinder test when knocking, andprovides a new direction to the development of knock detection. In the paper, we madefurther detailed research according to the detection method, the Influence factors of ionflow signal, the relationship between ion flow signal and engine detonation, and theapplication of wavelet in the ion flow signal analysis process, and then got the relativeconclusions.This paper mainly works in the following aspectsAlthough many scholars and teams involved in the study of ion flow method inrecent years, for the detection means of ion flow was restricted, leading to analysis ofthe ion flow signal has not been able to study further. In order to detect the stable andreliable ion flow signal, firstly, we should optimize the detection circuit of ion flow andcontrol the amplitude of a signal and signal to noise ratio in our satisfactory range, thisis also the precondition of the subsequent signal analysis. And then, we must create theideal, stability experiment conditions that we need in the engine, in order to collect theexperiment data. The work seems simple, it is the foundation of the whole research, andall the following studies base on this work.1. Optimize the signal acquisition circuit of the ion flow and realize the low noiseacquisition of ion flow signal. The signals that are collected in the experimental processare stable, little interference by high pressure and then the system of signal acquisitioncan work very steady. The repeatability of ion flow signal waveform is very good underdifferent engine working cycles, when the engines are in the same work condition,which make a breakthrough in the measurement of ion flow signal.2. Study the problem that the ion flow signal is affected by spark plug parameters. It is very critical that the ion flow affected by spark plug, which is the crossing part ofengine ignition system and ion flow signal acquisition system. In the paper, we drewconclusions by the comparative researching on the ion flow signal from three differentparameters of spark plugs.3. Study the problem of ion flow signal is affected by the value of octane. The ionflow signals are different when the engine using different octane rating of gasoline.When the engine detonation is caused, and then we study the ion flow signal that wecollected in the experiment, and got the range characteristics and range integralcharacter of ion flow signal when using gasoline of low octane rating.4. Study the problem of ion flow signal is affected by the change of offset voltagein the detection circuit of ion flow signal. We need to make it clear that the ion flowsignal is affected by the change of offset voltage thus to control the ion flow signalamplitude and make it meet the requirements of our follow up signal processes. Weanalyse the ion flow signal that is collected under350V and700V offset voltage in theexperiment contrastively and draw conclusions accordingly.5. Study the character of ion flow signal under different degrees of engine knockintensity. The core content of this article is the detection and controls of engine knockby ion flow signal, therefore, we must find out the relationship between the ion flowsignal and the engine detonation, when the engine speed gets1800r/min, we collect theion flow signal respectively when the engine knocks under the condition of21%Throttle Angle (torque about70Nm), of20%Throttle Angle(torque about60Nm),19%Throttle Angle(torque about50Nm),18%Throttle Angle(torque about40Nm).In theprocess of signal analysis, in order to contrast the ion flow signal under circumstancesof knocking and not knocking, we divide the cylinder pressure in sections andput the working cycle together of similar air condition in the cylinder. In differentdriving conditions and points, the segment division base on the cylinder pressure frommore than4MPa to2MPa with0.5MPa for step length. Analyze and contrast the ionflow signal amplitude characteristics respectively in the same section of the cylinderpressure and in different sections and then get the conclusions accordingly.6. Leading in the method of wavelet analysis to the analysis of ion flow signal. Themethod of wavelet analysis is the new method of signal analysis in recent years and thedevelopment and extension of Fourier transform. Combining the characteristic of ionflow signal, the article made wavelet analysis of ion flow signal and get the betterconclusions with the analysis of ion flow signal amplitude.The main innovation points of the paper1. Optimization of the ion flow measuring circuitIt is a important technical problem to the researchers that the optimization of theion flow signal detection circuit. If we cannot cope with the isolation of dozens of kvhigh ignition pressure, we will cannot acquire the data or even burn down theinstrument. In the course of experiment, this problem was thoroughly solved, theinterference to the signal is small, the signal to noise ratio (SNR) can meet therequirements, the signal amplitude can also freely control in the scope of oursatisfaction. 2. In depth study of the question effect of external factors in ion flow signalIt is the important factor to affect ion flow signal that the spark plug parameters,fuel octane, bias voltage of ion flow detection circuit and the other parameters of theoutside world, this paper discusses the influence of external factors in ion flow signalproblem.3. In depth study the question of change rule of ion flow signal amplitude underdifferent knock intensitiesThis thesis proposes the new viewpoint that divided the cylinder pressure intosections, even analyzing ion flow signal based on the division of classification, anddescripting the relationship between the rate of ion flow signal and the detonation indetail.4. Leading the method of wavelet analysis in the analysis process of the ion flowCombined with the characteristics of the ion flow signal, using Hal waveletanalysis in the analysis of ion flow, it has been found that the method of waveletanalysis is a kind of very good methods of signal analysis. It will promote the analysisof ion flow signal on a large scale in the future.The future work prospectsThe work that needs to be further enriched and perfected in this paper mainly is:1. Improve the experimental conditionsDue to the limit of the conditions, most content of this paper used the cylinderpressure sensor to replace the spark plugs doing experiment and data collection. Thereare certain differences between the cylinder pressure sensor and ordinary spark plug, sothe result must be limited. In order to overcome these limitations, the best way isdrilling in the cylinder, installing cylinder pressure sensor and common spark plugseparately. At the same time, installing the common spark plug so as to make the enginework. By using cylinder pressure sensor measuring cylinder pressure variations andcommon spark plug measuring ion flow signal, we could make the experimental resultsmore closer to the true conditon.2. Perform the ion flow test in more working points of the operation conditionIn order to promote the application, we should measure and analysis ion flow inmore working points, and make the experiment results own more universal rules.更多还原