1、Direct Injection Systems The Next Decade in EngineTechnology Cornel Stan Professorof Engineering WestSaxon University ofZ ic!au#i$rary of CongressCataloging%in%Pu$lication Data Stan on the other handalve Control The charge ofthe cylinder with air during the scavenging is a determinating factor for t
2、he engine performances such as torque, specific fuel consumption and pollutant emission. $ts optimi ation for every load)speed range requires a fully variable valve control. This concerns the valve course, their opening duration, as well as the timing correlation between the opening ofe!haust and in
3、ta#e valves.Fig. 1.1 Overview of propulsion units, energy storage forms and energy conversion concepts applicable for vehicles Fig. 1.2 *eplacement ofthe fuel cell by a piston engine as a current generatorThere are different solutions of valve actuation: mechanically, with control by an electric mot
4、or, electromagnetically, hydraulically with electromagnetic control. (uch systems allow for e!ample a reduction of the specific fuel consumption in the range of 15%, respectively a torque increase up to 35%, as demonstrated by the recent results obtained by &O*(CHE and +O! reduction in combination w
5、ith the control of the catalytic conversion ofe!haust gas components s=b management ofthe heat transfer from the wor#ing fluid by adaptable control of the cooling circuit. The potential of down-si ing is demonstrated for e!ample by the decrease of specific fuel consumption with appro!imately 30%.Fig
6、. 1.3 Correlated control ofinternal mi!ture formation and combustion p=m-schematically Fig. 1.4 anagement ofthe thermodynamic process in a piston engine by modular functionsFle!ible Fuel Operation The limited availability of crude oil in the future, as well as the e!pected restrictions of CO2 emissi
7、on recommend the larger utili ation of regenerative fuels such as methanol, ethanol, oils or ethers. On the other hand, the infrastructure conditions favor more the use ofvariable mi!tures, for e!ample gasoline ) ethanol ) methanol than parallel solutions. Correlated Functions The modular function o
8、f a direct injection system in the conte!t ofvariable valve control, turbo- or supercharging, variable compression ratio or variable control of the cooling circuit requires both a fully integration and a variable adaptation to the whole engine system. The favorable aspect of this configuration is th
9、e support of all these modular functions by an unique electronic management. The future utili ation forms of the internal combustion engines, as well as the modular configuration of such propulsion systems are the determining conditions for the e!pected development of direct injection systems for sp
10、ar#-ignition and compression-ignition engines.Chapter Two Potentials of Direct Injection Structure of Mixture The conversion of heat into work and their effects in terms of specific fuel consumption and exhaust gas composition is mainly determined by the combustion process The !uality of combustion
11、depends generally on the mixture formation mechanism between fuel and air“ the fuel droplet si#e and velocity$ the droplet distribution on the air within the combustion chamber$ the turbulence induced by the air and fuel flows$ or the fuel droplet impact on the walls of the combustion chamber affect
12、 the performances in both types of piston engines$ spark-ignited and compression-ignited as well In spark-ignition engines$ the initiation of chemical reactions is provoked by an external energy source& conse!uently$ their propagation in a flame front re!uires similar chemical and thermal conditions
13、 in any direction This means that a #one of stoichiometric fuel / air mixture cannot be interrupted by volumes of pure air or burned gas$ if the reaction must continue in a further mixture #one with same concentration but without spark plug Nevertheless$ #ones of fresh air or burned gas within the c
14、ombustion chamber are not disadvantageous if the mixture cloud remains continuous in some direction$ respectively if a contact of this mixture cloud with the spark source is allowed Such scenario corresponds to a part load charge Obviously$ for full load$ the full cylinder volume should be filled wi
15、th homogeneous mixture *oing from the imposed continuity of mixture properties in spark-ignition engines$ the most simple solution is to induce the already prepared mixture into the combustion chamber +p=m-+ using a manifold injection$ as an advanced dosage device after the long carburetor deploymen
16、t The fuel induction in a manifold tube has some basic advantages“ the steady and adaptable direction of both flows$ fuel and air$ a relatively long trajectory for droplet distribution without wall impact and +p=m-+ first of all +p=m-+ sufficient time of mixture formation between the consecutive scavenging events +p=m-+ especially in four stroke engines But the cylinder scavenging with the already formed mixture has intrinsic disadvantages in
