Elemental Study on Superadiabatic Engine Based on the Porous-Medium Combustion Technique
|School||Dalian University of Technology|
|Course||Power Machinery and Engineering|
|Keywords||Porous medium engine Super- adiabatic combustion Finite-time thermodynamics Porous media regenerative cycle Reaction kinetics Oxidation mechanism The seepage hole liquid fog Numerical Simulation|
With the rapid development of the world economy, energy and the environment has become a primary concern in today's world the two hot issues, car engine as the main source of energy consumption and environmental pollution has been widespread concern of researchers around the world, how to achieve efficient and clean-burning has become one of the most urgent task of the international engine sector. Engine technological innovation, the porous medium engine as a new engine based on the new concept of the superiority of its unique combustion, low emission, low noise by more and more attention. Through theoretical analysis and numerical simulation engine duty cycle and combustion characteristics of porous media, on the basis of the mechanism of experiments investigated the combustion characteristics of liquid fuel in porous media. Aimed at through theoretical and experimental research, in-depth understanding of the operating characteristics of the porous medium engine to promote the practical use of the porous medium engine. First of all, the conclusion in the the existing porous medium burner used in porous media engine, engine thermodynamic model of porous media, ideal for porous media engine cycle and irreversible cycle efficacy of characteristics and available energy loss to be analyzed. (1) the theory of classical thermodynamics as a guide, off, closed two of the engine is working cycle thermodynamic analysis of the system. From the theoretical analysis of the engine is the work process to discuss the ideal cycle performance parameters such as compression ratio, temperature extremes and other engine efficiency, cycle power analysis cycle exergy loss and porous media regenerative cycle with conventional engines Otto cycle, Diesel cycle for comparison. The results showed that the overall level of performance of the porous medium engine better than conventional engines, has the characteristics of high efficiency, cycle power. (2) using the method of finite-time thermodynamics closed porous media engine porous media back to the effect of thermal cycling characteristics. Considered separately under conditions of heat loss and the friction loss of the piston, the cycle functionality and efficiency of the relationship and the maximum power output efficiency boundaries deduced performance relationship, and gives a more detailed numerical results are discussed with the combustion, friction parameters related to the efficacy characteristics such that the thermodynamic cycle analysis closer to the actual process. This is of great significance to the assessment and improvement of the actual porous media engine performance. Secondly, based on the current international fashion and has been proven HCCI combustion model single-zone, multi-zone model for the porous dielectric characteristics of the engine, the establishment of single-zone model and the two-region model for porous media engine simulation. (1) based on the first law of thermodynamics, the application CHEMKIN chemical kinetics package SENKIN module combined with the zero-dimensional single-engine combustion zone model to simulate the n-heptane combustion process in porous media engine. By modify SENKIN program, join the heat transfer Woschni model, the porous medium heat transfer model and the heat release rate model, the establishment of the energy equation in porous media engine. Heat release rate model were used the alternative combustion law and n-heptane oxidation mechanism in two ways, the mechanism of the formation of nitrogen oxides in n-heptane oxidation mechanism. Calculated under a variety of conditions parameters porous media engine cylinder temperature, pressure variation, respectively, discussed the impact of the compression ratio, the porous medium temperature, body heat transfer coefficient and the excess air coefficient parameters of porous media engine combustion process. Through porous media engine with a conventional engine temperature, pressure variation, to prove that the porous medium to flatten the cylinder temperature and pressure changes. (2) consider the quality of each interval distribution and exchange, wall heat transfer, interval mass exchange factors, combined with the porous medium heat transfer model, the establishment of open, a closed porous media engine quasi-dimensional two-region model, its combustion process simulation. The program coupled chemical reaction dynamics calculation package CHEMKIN III, the mass exchange between the two districts Komninos-based multi-zone model to be simplified, wall heat transfer model for HCCI engine designed the improved Woschni model to different octane fuel, using a the skeleton reaction mechanism combustion process customized for the HCCI engine. Focused on the intake air temperature and pressure, the compression ratio, the excess air ratio and the porous medium initial temperature and other operating parameters of the porous medium engine performance. The results show that, due to the high temperature of the porous medium and its mixed gas preheating, and promote the vaporization of the liquid fuel and the combustion reaction occurs, the initial temperature and the compression ratio is an important factor to determine the compression ignition engine. Open PM engine, the manner and process of vaporization of the fuel oil has a greater impact on the mass of the cylinder fuel distribution; Closed PM engine, liquid fuel vaporization process entirely in the porous medium indoor without injector moment, load the impact of other operating parameters, valve open time to decide a mixture of steam and air, is an important factor to determine whether the fire in the porous medium. Finally, through the mechanism of Experimental study on liquid fuel combustion in porous media properties. In view of the high-speed engine transient conditions are not suitable for the observation and measurement of principle study, we designed porous media burners for liquid fuel, \principle experiment. Own design and Country bench including burners (quartz glass tube), the gas supply system, a fuel supply system, and a measurement system. The bench has the dual function of research in porous media gas combustion wave propagation and liquid combustion characteristics. Combustion of the porous medium through the fuel gas within the porous medium is preheated, the liquid fuel is then injected into the porous medium burner, combustion after vaporization. Discuss the mixed gas flow rate and the equivalent ratio of the combustion wave propagation velocity of the packed bed and the maximum temperature by the temperature distribution of the combustion zone of the thermocouple measurement.