Optimization Study On Working Process And Key Components Of Air Powered Engine

Cars driven by compressed air or liquid nitrogen are one kind of novel concept vehicle. Due to its clean air exhaust and energy regenerated characters, presence of air powered cars is coincident with future car developing idea which including safety, comfort, conservation of energy, environment friendlyship, abundant fuel supply and so on. It's conceivable that wide application of air powered car would elaborate increasing environment and energy impacts brought by cars driven by internal combustion engine. Currently, achievements in field of air powered engine are nothing but simple modifications or fragmentary theories which resulted in direct viewing experiments and unilateral theories. Comparing with complicated combustion process of ICE, working process of air powered engine is much simple. But it's still a huge systemic project to develop and study air powered car. Only systematic project programming, scientific technique routine, drawing on wisdom of masses and racing against clock could be helpful to form integrated air automobile theory, achieve core technique and accelerate air automobile entering people's daily life.Considering low energy utility efficiency of air powered sample engine and there is no method to design air powered engine, this paper is dedicated to optimizing it basing on predecessors' instructive achievements. Main job consists of systematic thermocycle optimization and component optimization which are detailed in follow.Overview on developments of air powered engine and vehicle Researching routines and achievements in air powered engine of main researching institute are introduced. It's concluded that gas admission management system, pneumatic powering whole vehicle and lighting, optimization design methods study are 3 core techniques duration course of developing air automobile. It's also illustrated that air hybrid powering system is superior to other hybrid system. It's proposed that Teachings on air powered engine should follow routine turning from mechanic valve trains to intelligent variable valve timing system, from single stage single component cycle to multistage multi-component thermo cycle, from part optimization to system design and optimization.Feasibility study on developping air powered engine Feasibility study on application of air automobile is completed by analysis of real fuel energy density, circulation efficiency, dynamic and economic performance, driving cost, fuel production, safety and auxiliary constructions and so on. It's proved that air automobile is a practice green vehicle with huge application value.Experiment studies on air powered engine Through degree of freedom analysis, air engine system has 3 DOFs which are injection temperature, pressure and engine speed. A liquid nitrogen fueled air powered engine test bench is also built where impacts of free variables on engine dynamic and economic performance are tested. Then entropy analysis is enclosed in analyzing system efficiencies basing on experiment results, which make energy distributions and consuming status clear. Following optimizations are conducted base on results. Air propulsion system design based on thermodynamics model System design can be used to evaluate performance upper limit and provide data for parts design. To increase energy efficiency, a 4-stage liquid nitrogen-methane-ethylene-R134a isentropic Rankine power cycle is presented. Simulation results show that energy efficiency increases from 24 % in original single Rankine cycle to 60 %. And problem of frost building on external surface of heat exchanger is avoided in theory. A "benefit function" is built to represent performance of thermo system basing on thermo economics and fuzzy synthetical evaluation is incorperated to compare designed cycle to another high efficiency cycle "Braton cycle". It's showed that new designed cycle is better with little fluctuation when irreversible disturbance occurred. To determine injection parameters and engine parameters for fixed injection and discharge angle, an simplified process model, main charters of real working process is retained, is presented and one group of optimal parameters are gotten by specific work output, power, second law of thermodynamics objected multi objective optimization in Matlab optimization tools box. Real engine working process with variable valve time is modeled basing finite time thermodynamics and changeable mass thermodynamics and relationships of injection pressure, valve timing with engine performance and air consuming rate are presented. "On-line parameters tuning method" is proposed to realize VVT air engine parameters tuning realtime. Nondominated sorting genetic algorithm is modified and introdced as basis for air powered engine design. A group of design curves air presented in the paper.Schemes of optimization on key parts of air powered engine To eliminate affections of irreversibilities on system performances and reach its design goal, some optimizations must be done on key parts of air engine. In this paper, a procedure is programmed basing on functional optimization theory to optimize piston trajectory. Simulation results showed that there is 100 % more of specific work in resulted new trajectory than original piston trajectory. Furthermore, relations leading to high energy efficiency between vavle open and piston movement are given. In order to eliminate fraction of energy consuming in injection process and improve work output by utilizing nonuniform characters of cylinder flow field, cylinder flow field in variform intake ports and piston surfaces are presented by CFD software Fluent. It's shown that streamlined intake port and hemispherical piston surface lead to an evident increase in work output. Achievements in optimization on heat exchanger of liquid nitrogen propulsion system, isothermal expander and engine structure and so on, abundant optimization schemes are also introduced in the paper.Structure design and control algorithm design on valves with variable timing To realize VVT valve trains in air powered engine; an electro magnet powered valve is designed. Its structure and operation principle are specified in detail. Geometry of intake valve is designed on criteria that there is no supersonic flow appeared in inlet port. Parameters of electromagnet are designed according to equested valve responding time. And PWM voltage input driven circuit is also presented. Performance of designed electromagnet valve is evaluated in MATLAB/Simulink where realistic model is built and affection of input voltage and injection pressure on valve dynamic performance are also presented by model. In order to control valve reliable with disturbance and measure error existence, a close loop control system combining Lyapunov Redesign method with PID control method and an open loop control system basing on current measurement are built. Simulation procedure is then built to study and compare performances of close and open loop control system. Nonlinear absorbability analysis on electromagnet valve system is also conducted. It's proved that system with current as output is observable. One can evaluate all of system states by observing current, which offers a basis for state observer design.This paper develops onnotation of air automobile, makes research direction clear, resolves air powered engine technique into pieces and studies deeply into some sections. That not only arranges predecessors' achievements, but also lay down foundations for subsequent researching.