The thermal efficiency of gasoline engines have improved greatly by using of variable valve actuation, direct gasoline injection system, etc. In diesel engines, the exhaust emission is becoming clean without decreasing thermal efficiency by using of common rail fuel injection system, high-boosting and high-EGR system and the after-treatment technology. The homogeneous charge compression ignition is bringing the revolution to the combustion of both engines. This paper describes the outline of key components technologies contribute to engine combustion.
Various methods of variable valve actuation mechanisms has been studied during the past decades until today, a simple phase shift mechanisms and cam robe switching mechanisms are commonly used and Variable Valve Lift & Duration (VVLD) was put into practical use in 2001. These technologies drastically expanded the degree of freedom in valve timing variation. In this paper, the principle of variable valve actuation mechanism, particularly of VVLD is explained by introducing some mass-produced and studied systems. In addition, “Exhaust Secondary Cam” mechanism, which an exhaust valve reopens at the beginning of the compression stroke, is introduced and its simulation and experiment results in several usages are shown for detail. Unlike fuel injection which controls local air-fuel mixture characteristics in the combustion chamber, a variable valve actuation system can control the cylinder average air-fuel mixture characteristics such as cylinder pressure, temperature, fuel density (opposite of mixture quantity) and oxygen density. Their impact on local combustion are not high, however they play an important roll on the overall combustion cycle performance. Combustion studies focused on how to take the advantages of variable valve timings are now expected to be performed widely.
Fuel injection system products are key parts of internal combustion engines in order to reduce exhaust emission and fuel consumption, which affect global environmental problems such as global warming and energy resources exhaustion. In this paper, we describe history and future trends on fuel injection system products for gasoline and diesel engines which were mainly developed and have been mainly developing by DENSO CORPORATON. We have many subjects to be solved for the global environmental problems, and need further evolution of the fuel injection system products with continuous developments.
Catalysts for the exhaust gas purification are a significant important parts for the automotive to achieve the emission reduction and the fuel consumption improvement for the global warming prevention and the environmental protection. In this paper, we describe the outline of the catalyst technology for the exhaust gas purification of the current state, and to touch about the trend in the future. The catalyst technology will be an important indispensable technology when the future for the automotive to accomplish continued development while solving environmental problems.
The aspects of partially premixed flame are briefly surveyed by reviewing the past studies and reports. Partially premixed flame, which propagates in a stratified mixture, is a key flame configuration to understand the turbulent combustion in practical appliances. The leading edge flame structure so called ‘edge flame’ or ‘triple flame,’ which is composed of rich/lean premixed flames and diffusion flame, is an important and dominant flame element controlling the propagation speed (and stability) of partially premixed flame. The fuel density gradient in the direction normal to flame propagation direction affects the shape and the effective propagation speed of the flame. The flame can be stabilized in a flow filed whose velocity is larger than the propagation speed of stoichiometric planar premixed flame, indicating that its effective propagation speed can be larger than the propagation speed of planar premixed flame. The large effective propagation speed results from the flow deceleration near the leading edge due to the flow divergence by thermal dilatation. Jet lifted flame is a typical fundamental flame configuration of partially premixed flame. The stabilization point of the flame is determined by the balance between the local burning velocity and the decelerated local flow speed in front of the leading edge flame. The modelling of partially premixed flame is still in progress. The effective use of DNS data of partially premixed flame is expected to contribute to the understanding and modelling.
Numerical simulations of stoicheiometric H2/O2 detonation in 90-degrees bent pipe were performed with a detailed chemical reaction model at initial pressure P0=0.1 MPa. The scales of pipe were changed two and three times similarly to understand the scale effects on propagation of detonation through the bent section. The results show that the scale effects are small except 2nd peak along the extrados under the present conditions as well as the shock wave propagating in the air-filled bent pipe reported by Edwards et al. As the detonation propagates through the bent section, the Mach reflection near the extrados appears twice and the transverse detonation is formed to collide on the intrados with maximum pressure of 6-8 PCJ. The cell effects on the total impulse are small though the propagation mechanism changes through the bent section. The detonations through the bent section are re-initiated without quenching and they are independent of the cell effects.
The purpose of this study is to clarify the mechanism of high-speed flame propagation along a vortex ring (the vortex bursting) by 3-D numerical simulation. In the 3-D visualization of vortex line and temperature distributions in the calculation domain, the helical vortex line was seen near the flame top. Furthermore, in the 1-D geometrical analysis along the vortex line, the peaks of curvature and torsion (the solitary waves like the vortex filament solitons) were observed at the locations of large temperature gradient (the flame zones), and these solitary waves and flame zones propagated together along the vortex line. Thus, it was found that the vortex filament solitons might play an important role in the mechanism of high-speed flame propagation along a vortex, and the results of this study proved the validity of the original idea of vortex driving mechanism proposed by Shinoda et al. (1993).
This paper evaluates the accuracy of author's combustion model that can be applied to the premixed and diffusion flames. The proposed united combustion model is based on the author's premixed combustion model and the effect of preferential diffusion is considered through the author's algebra model that evaluates fuel concentration variation on the flame with curvature. In this paper, a H2/N2 lifted flame in vitiated coflow conducted by Cabra was numerically simulated. Two simulations were performed, the one is with the proposed preferential diffusion model and the other is without that model. Both of them, calculated mixture fraction profiles were in good agreement with experimental data within x/D≦11 and were not within x/D≧14 because of overestimation of fuel diffusion. Comparing each result, it is indicated that the preferential diffusion model enhanced reaction speed, especially around the jet nozzle exit. However, the influence of overestimation of fuel diffusion is not negligible so that it is difficult to evaluate the superiority of the calculation with the author's preferential diffusion model. As a future works, more suitable analysis object should be simulated for evaluate the preferential diffusion effect quantitatively.