In order to deal with the pollution due to emissions, diesel oil shortage challenges, people developed a new type of engine with low energy consumption and low pollution characteristics, mainly including electric motor, fuel cell engine, air powered engine, hybrid engine, the hybrid compressed air and fuel engine has become a research hotspot. The author proposes a new hybrid compressed air and fuel engine concept, this hybrid engine can run on compressed air power mode and the internal combustion mode two mode, equipped with this hybrid engine vehicle is suitable for city traffic. In the start-up and low speed stage, compressed air is used as a power source, so that the engine runs in the compressed air power mode, which can play the characteristics of low speed, high torque and zero pollution emission of the compressed air power engine. Using the internal combustion engine mode at high speed or load can avoid the disadvantages of high energy consumption and harmful emissions at low speed, so that the engine can run near the best energy consumption and low pollution conditions.
1. gas tank valve 2. 3. heat exchanger 4. flow valve 5. solenoid valve 6. compressed air nozzle 7. intake valve 8. nozzle 9. electronically controlled fuel injection device 10. exhaust valve 11. cylinder 12. cylinder piston 13. crank hybrid engine schematic diagram based on the compressed air and the first law of thermodynamics numerical simulation of hybrid fuel engine the process on the application of the second law of thermodynamics, the working process of the project work in two modes: the national natural fund project supported by a Ford Foundation (50122115) (dashed line bounding part) simplified calculation assumes that the gas state in the cylinder is uniform, the cylinder pressure, temperature the same as refrigerant; the ideal gas heat, internal energy, enthalpy and other parameters are only related to the gas temperature and gas composition; the gas inflow or outflow cylinder shall prevail Steady flow; (4) the kinetic energy of the import and export gas is negligible.
The working process of the engine is the process of the change of the thermodynamic state of the gas under the 1.1 compressed air dynamic model, which can be used to compress the aerodynamic mode of the energy balance equation. According to the first law of thermodynamics, the energy conservation equation of the system can be obtained: the boundary heat transfer; Hi, hE and he are the specific enthalpy of intake, exhaust and compressed air respectively; MI, mE and m are: intake, exhaust and compressed air intake quality; 9 is the crankshaft angle. T is the temperature of the working fluid in the cylinder.
The instantaneous mass of gas entering and discharging cylinder is one dimensional isentropic adiabatic flow. The rate of change with the change of crankshaft angle is the area of opening. Pi is the gas pressure before inlet and outlet, P is the instantaneous density of gas before intake and exhaust port, and the flow function is small.
The second law of thermodynamics can be obtained by the exergy balance equations of compressed air power mode system: flow: Aw, is the power available energy; Aq wall heat transfer exergy; A system exergy; exergy loss caused by Ad is not reversible.
When <, the intake and exhaust is a supercritical flow: (1) the amount of energy available to the compressed air. The available air of compressed air at the inlet of compressed air has the available energy for the internal energy of the working fluid according to the usti formula. 18, the change of the working medium's entropy is derived from the ideal gas entropy equation, that is, the pressure and the environmental pressure.
Calculated by the formula of available energy per unit mass of compressed air in the air storage tank has the heat transfer can be written as a system and cylinder wall pressure.
(2) the available energy change of the intake inlet system is the average temperature of the heat transfer surface.
The 1.2 mode of internal combustion engine exergy balance equation and compressed air force model is similar, the energy conservation equation of an internal combustion engine mode system by the first law of Thermodynamics: (4) the variation of available energy for power piston (7) combustion fuel availability variation is determined by the formula: (5) to the wall heat transfer system the change of availability for specific entropy.
(3) from the exhaust system with available energy variation by the second law of thermodynamics can be obtained by the internal combustion mode system exergy balance equation of cylinder diameter (mm) 62 (mm) 66 piston stroke compression ratio of 8.7 inspiratory pressure (MPa) 0.10 (MPa) 0.11 exhaust pressure of compressed air inlet pressure (MPa) 3 pressure (MPa) 0.10 ambient temperature (IO293 mixture combustion percent.
The fuel exothermic rate dX/d can be simulated with the Weber generation heat release curve, and the calculation precision is sufficient. The empirical formula is as follows: the beginning angle.
The calculation of other available energy variations in the energy balance equation of an internal combustion engine mode can be found in the compressed air dynamic model.
2 work availability analysis of the mathematical model based on the first law of thermodynamics applied in the numerical simulation of transient temperature, pressure and gas quality in cylinder working process, application of the second law of thermodynamics of hybrid engine two working modes of analysis and calculation of volume availability. In urban traffic, the average speed is usually around 40km/h, and the engine speed is generally between 1500~1800r/min. Simulation of switching speed of two mode is set to 1500r/min, other simulation initial parameters are shown in table 1. Table 1 hybrid engine simulation of initial parameters of 2.1 compressed air dynamic model of exergy analysis of 180 DEG) is calculated as the starting point, at 355 degrees (i.e. compressed air intake advance angle is 5 degrees, to open the solenoid valve to the cylinder is injected into the compressed air in the closed solenoid valve, =445 degrees (i.e. compressed air intake duration angle is 90 degrees). The system can get a curve (,) which can change with the angle of the crankshaft when the speed is 1500r/min.