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Combustion of stratified charge propane-air mixture with swirling flow in a constant-volume vessel
Eiji Tomita,Nobuyuki Kawahara,Atsushi Nishiyama,Sadami Yoshiyama,Yoshisuke Hamamoto 한국자동차공학회 2001 한국자동차공학회 Symposium Vol.- No.-
Direct injection spark ignition engines can achieve better thermal efficiency by applying stratified fuel concentration in the combustion chamber. The purpose of this study is to clarify the combustion in such inhomogeneous fuel concentration field. The combustion of inhomogeneous fuel concentration field in a cylindrical constant volume vessel was fundamentally investigated axisymmetrically. A swirling fuel-air mixture was produced in the vessel. A rich fuel concentration was formed near the center of the vessel by the injection of propane. The mixture was ignited at the center of the vessel. The experimental runs were done under various conditions at fuel distribution and swirl flow at the ignition timing. The fuel concentration distribution at the ignition timing was measured using laser-induced fluorescence. The gas flow field was obtained with a laser Doppler velocimeter in advance. The pressure history in the combustion chamber was analyzed to determine the combustion characteristics. Furthermore, a high-speed video camera was used to capture the flame development. The flame can propagate and the combustion occurs even in an ultra lean mixture of equivalence ratio of 0.3 in total. As the fuel concentration near the spark location approximates stoichiometric, flame propagation of the initial stage of the combustion becomes faster under an ultra lean mixture condition.<br/> <br/>
Nobuyuki Kawahara,Eiji Tomita 한국자동차공학회 2001 한국자동차공학회 Symposium Vol.- No.-
A fiber-optic heterodyne interferometry system was developed to obtain the temperature histories of an unburned mixture with high temporal resolution non-intrusively. In laser interferometry, the effective optical path length of the test beam changes with the gas density and corresponding changes of the refractive index. Therefore, the temperature history of an unburned gas can be determined from the pressure and phase shift of the heterodyne signal. A polarization-preserving fiber is used to deliver the lest beam to and from the test section, to improve the feasibility of the system as a sensor probe. The temperature of the unburned mixture in the end-gas region of a constant volume combustion chamber and in an engine cylinder was measured during flame propagation. The accuracy of the measurements and the feasibility of this system are discussed. The measurement accuracy of our system was sufficient to be applied to temperature history measurement of an unburned gas compressed by flame propagation in a constant-volume combustion chamber. The uncertainly of this method is within ±10 K. The resolution of the temperature measurement is approximately 0.5 K, and is dependent on both the sampling clock speed of the A/D converter and the length of the test section. This fiber-optic heterodyne interferometry system can also be used for other applications that require a transient temperature with a fast response time.<br/> <br/>
Evaluation of Nozzle Exit Model for Transient Spray in a Multi-hole DISI injector
( Nobuyuki Kawahara ),( Shuhei Takada ),( Eiji Tomita ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
The purpose of this study is to propose the nozzle exit model for transient fuel spray in a multi-hole injector for the direct injection spark ignition (DISI) engine. The primary spray breakup near the nozzle exit of DISI injector is important to understand the atomization process. In this research, the nozzle exit model was proposed to simulate fuel spray injection by using measured droplet diameter distributions. Using HiDense PDA system, it is possible to measure droplet diameter and velocity very close to the nozzle exit of the one hole in the multi-hole injector. Measured droplet diameter distributions can be approximated using by Rosin-Rammler distribution and log-normal distribution. Numerical simulation of spray behavior was carried out using proposed nozzle exit model as initial condition of the nozzle exit. GTT code was used for numerical simulation. The GTT code developed by Wakisaka et al. is based on a finite volume method with generalized curvilinear coordinates (Generalized Tank and Tube method). It employs efficient explicit/implicit algorithms and can easily be run on a personal computer. To analyze spray behavior, the modified wave breakup model derived from Reitz’s model was used for secondary spray break-up model. In different injection pressure (5 and 13MPa), the results of fuel spray simulation using droplet diameters distribution approximated by log-normal distribution corresponded to those of experiment in terms of penetration and droplet diameter along to the downstream. The calculated results of spray penetration and SMD showed good agreement with experimental results in two injection pressure conditions.