随着世界环境污染的日益严重和能源危机的不断加剧

随着世界环境污染的日益严重和能源危机的不断加剧，发动机的燃烧性能和尾气排放逐渐成为人们研究的重点，使用燃烧率高、环境污染小的发动机也就逐渐为各国政府和专业人士所极力倡导。改善燃烧室内的火焰燃烧过程和采用新型的代用燃料或燃料添加剂则是解决以上问题的常用办法。作为一种新型的稀薄燃烧方式, GDI 发动机综合了压燃式发动机与点燃式发动机的优点,通过燃油的缸内直接喷射、可变喷油定时和控制缸内的气流运动等方式实现了缸内的稀薄燃烧,使发动机无论在燃油经济性还是在降低排放等方面都表现出比PFI(port fuel injection) 发动机更大的发展潜力。GDI 发动机节能减排的目标主要是通过分层稀薄燃烧实现的，而燃油效率和尾气排放数量又主要受缸内混合气浓度等因素的影响。随着科学技术的不断发展，稀薄燃烧技术已经逐渐成为提高发动机燃油性能的重要手段。

GDI发动机稀薄燃烧技术有多种分类形式。如依据喷射形式上差异可以分为缸内直喷和气道喷射稀薄燃烧，依据发动机气缸内涡流的形式可以分为纵向和轴向分层稀薄。GDI发动机稀薄燃烧技术主要涵盖了稀薄燃烧、缸内气流控制、喷射点控制、喷雾及其压力控制等。GDI 发动机在设计喷油器的位置时考虑了多方面的因素，为了便于混合气浓度的合理分布，喷油器被安置在了燃烧室的内部，能够有效避免其他因素对混合气综合质量的不利影响，提高泵气的利用效率，从而更容易达到稀薄燃烧的目的，这对提高GDI 的经济效益、降低尾气排放也是非常有利的。

GDI发动机具有很好的工作稳定性和负荷性能，同时低温起动性能得到了明显改善，能实现分层燃烧，燃油经济性大大提高，其油耗可达到涡轮增压直喷(TDI)柴油机的水平，且省略了涡轮增压装置，省却了复杂的高压喷射系统。GDI发动机能用稀燃技术，空燃比可高达40：1，甚至最高可达100：1，使得功率和转矩均高于传统汽油机，油耗、噪声及二氧化碳的排放量都较低，GDI发动机工作的均匀性、瞬时反映性、起动性等均比传统汽油发动机有较大的改进。因此各国汽车生产企业都在大力开发这种技术先进、性能优异的GDI发动机。

作为一种新型的燃烧方式, GDI发动机对解决能源危机和环境污染会起到很大的作用。同任何一项新兴技术一样,目前尚处于发展阶段的GDI还有很多缺点和不足,但是随着研究的深入和一些相关技术的发展, 尤其是分层稀薄燃烧技术的研究和推广， GDI 发动机促进经济效益和社会效益的提高，有利于发动机的长远发展与进步，并且将来很有可能取代EFI发动机。

With the increasingly serious environmental pollution and intensified energy crisis, the combustion engine performance and exhaust emission has become the focus of research, the use of high combustion rate, less environmental pollution of the engine also gradually for governments and professionals advocated. Improvement of combustion flame combustion process and the new alternative fuel or fuel additive is the commonly used method to solve the above problems. As a new type of lean combustion model, GDI engine has the advantages of compression ignition engine and ignition engine, through the inner cylinder direct injection, variable injection timing and control cylinder air motion in cylinder and other ways to achieve lean combustion, so that the engine has greater development potential and aspects of performance than PFI (port fuel injection) engine either in fuel economy or in reducing emissions. GDI engine realized energy-saving emission reduction target is mainly through stratified thin combustion, and the fuel efficiency and emission amount is mainly affected by the gas mixture concentration in the cylinder and other factors. With the development of science and technology, lean combustion technology has gradually become the important means of improving engine performance.

The GDI engine lean combustion technology has several kinds of classification. If according to jet form differences can be divided into Disi and airway injection lean burn, on the basis of engine cylinder vortex forms can be divided into longitudinal stratification and axial stratification. The GDI engine lean combustion technology mainly covers the lean combustion, cylinder flow control; spray point control, spray and injection pressure control. We has consided many factors, when designing the injector position of The GDI engine, in order to facilitate the mixture concentration distribution, the injector is placed in the interior of the combustion chamber, which can effectively avoid the other factors on mixed gas comprehensive quality adverse effects, improve pumping efficiency, thereby making it easier to achieve lean burn objective, the economic benefit, reduce exhaust emissions is very favorable.

The GDI engine has good working stability and load performance, at the same time the cold starting performance is improved evidently, can realize stratified combustion, fuel economy is greatly improved, the oil consumption can reach the level of diesel engine with turbocharged direct injection ( TDI ), and omission the turbocharger, obviates the complex high pressure injection system. The GDI engine use lean combustion technology, the air-fuel ratio can be as high as40:1, or even up to 100: 1, which makes the power and torque were higher than those of the traditional gasoline engine, fuel consumption, noise and emissions are much lower, GDI engine has greatly improved working uniformity, instantaneous reflective, starting performance than the traditional gasoline engine. So most automobile manufacturers in developing the advanced excellent performance GDI engine.