摘 要

自进入21世纪以来，受蒸汽时代以及内燃机时代的影响，能源枯竭、全球变暖、两极冰雪融化以及极端气候、山林大火等问题越来越尖锐，全球的所有物种以及各个区域都受到了人类活动的影响。目前空气中的绝大部分是来自汽车，而且空气中的颗粒物，等等污染成分也大多是化石燃料燃烧的问题，因此寻找新的绿色的可再生替代能源目前看来是解决这些问题的绝佳途径。鉴于以上种种，我们基于燃烧学以及热动力学的角度，通过台架实验与仿真模拟相结合的方法，来研究生物柴油/乙醇混合燃料在柴油机燃烧时的燃烧特性与排放特性，以及不同的乙醇掺入比例对于混合燃料的燃烧特性和排放特性的影响。研究的结果表明：（1）对于燃烧方面，随着EGR率的增长，发动机的缸压、放热率的峰值以及有效热效率等指数都有所下降，燃油消耗率变大，燃料的滞燃期以及燃烧持续期都有所延长；而对于排放方面，NO的排放量随EGR的增大而降低，HC以及1，3-丁二烯、乙醛等的排放量却随着EGR率的增大而升高；对于颗粒物而言，大粒径的颗粒物的数量会随着EGR率的增大有所增加，小粒径的颗粒物数量却下降了很多；（2）同E0相比较，E10和E20的缸压以及放热率的峰值和发动机的有效热效率都增大了很多。

首先，本文基于台架试验，以E0、E10、E20为燃料，分别探索了不同的EGR率工况下三者的燃烧特性和排放特性都发生了怎样的变化。结果显示，随着EG率的增加，燃料燃烧的缸压、温度、放热率和热效率等都有所下降，燃油消耗率升高，HC的排放降低，但是它们的1，3-丁二烯、乙醛等非常规排放物的排放量却增大了，另外颗粒物的粒径向着小粒径的方向靠拢，大粒径颗粒物在不断减少，但颗粒物总体数量呈减少趋势。此外，整体而言，乙醇的掺入在整体上会明显改善生物柴油在发动机内燃烧时的燃烧特性和排放特性。同E0相比较，燃用E10时，缸内的压力、温度和放热率的峰值都比较高，CO排放减少，但由于温度和含氧量的增大，NO排放发生了增加。

其次，本文通过AVL-FIRE软件对于三种燃料的燃烧进行了仿真模拟，结果表明：相对于E0而言，E10的变化十分明显，而E20由于燃烧比较复杂，因此不做过多赘述，燃用E10时，缸内的压力、温度和放热率的峰值都比较高，CO排放减少，但NO排放增加，引入EGR之后，缸内进入大量高比热容组分，缸内的温度和氧气浓度降低，压力和放热率峰值也会有所降低，而且由于氧气减少的的缘故，CO和soot的排放增加，但NO的排放降低。

本文主要是通过台架试验与软件仿真模拟相结合的手段，对发动机燃用不同掺混比例的生物柴油/乙醇混合燃料在不同的EGR的工况下的燃烧特性以及排放特性做了探索，为生物柴油/乙醇混合燃料在实际生活中应用提供了理论支持。

关键词：生物柴油，乙醇，掺混燃料，EGR，燃烧，排放，仿真模拟

Abstract

Since the beginning of the 21st century, due to the influence of the steam era and the era of internal combustion engines, energy depletion, global warming, melting of polar ice and snow, extreme climates, and forest fires have become increasingly acute. All species and regions in the world have been affected by human activities.At present, most of the air comes from cars, and the particulate matter in the air, etc., are also mostly fossil fuel burning problems, so looking for new green renewable alternative energy sources currently seems to be an excellent solution to these problems way.In view of the above, from the perspective of combustion and thermodynamics, we use a combination of bench experiments and simulation to study the combustion characteristics and emission characteristics of diesel / ethanol mixed fuels during diesel engine combustion and different ethanol The influence of the blending ratio on the combustion characteristics and emission characteristics of the mixed fuel. The results of the study show that: (1) For combustion, with the increase of the EGR rate, the engine cylinder pressure, the peak heat release rate and the effective thermal efficiency index have decreased, the fuel consumption rate has become larger, and the fuel stagnation period And the duration of combustion has been extended; while for emissions, the amount of NO decreases with the increase of EGR, but the amount of HC, 1,3-butadiene, acetaldehyde etc. increases with the increase of EGR rate For particles, the number of particles with large particle size will increase with the increase of EGR rate, but the number of particles with small particle size will drop a lot; (2) Compared with E0, E10 and E20 The cylinder pressure and the peak heat release rate and the effective thermal efficiency of the engine have increased a lot.

First, based on the bench test, using E0, E10, and E20 as fuel, we explored how the combustion characteristics and emission characteristics of the three have changed under different EGR rate conditions.The results show that as the EG rate increases, the cylinder pressure, temperature, heat release rate, and thermal efficiency of fuel combustion all decrease, the fuel consumption rate increases, and HC emissions decrease, but the amount of unconventional emissions such as 1,3-butadiene and acetaldehyde has increased. In addition, the particle size of the particles is moving closer to the direction of the small particle size. The particle size of the large particle size is continually decreasing, but the overall number of particles is decreasing. In addition, overall, the incorporation of ethanol will significantly improve the combustion characteristics and emission characteristics of diesel when it is burned in the engine. Compared with E0, when E10 is used, the peak pressure, temperature, and heat release rate in the cylinder are relatively high, and CO emissions are reduced, but due to the increase in temperature and oxygen content, NO emissions have increased.

Secondly, the simulation of the combustion of the three fuels through the AVL-FIRE software shows that: compared with E0, the change of E10 is very obvious, and E20 is not complicated to repeat because it is more complicated to burn. At E10, the peak pressure, temperature, and heat release rate in the cylinder are relatively high, CO emissions are reduced, but NO emissions are increased. After introducing EGR, a large number of high specific heat components are introduced into the cylinder, and the temperature and oxygen concentration in the cylinder decrease The peak pressure and heat release rate will also be reduced, and due to the reduction of oxygen, CO and soot emissions increase, but NO emissions decrease.

In this paper, through the combination of bench test and software simulation, the combustion characteristics and emission characteristics of the engine with different blending ratios of diesel / ethanol blended fuel under different EGR conditions are explored. The diesel / ethanol blended fuels provide theoretical support in practical applications.

Key Words:Diesel ;Ethanol; Blended fuel;EGR;combustion;emission;Simulation

目录

第1章绪论 2

1.1课题研究的背景和意义 2

1.2国内外研究现状 3

1.3生物柴油与乙醇以及二者的掺混燃料的特性介绍 4

1.3.1生物柴油 4

1.3.2乙醇 6

1.3.3生物柴油与乙醇掺混燃料的特性 7