A method for reducing exhaust pressure of vehicle compressed air powered engine
Compressed air powered engine is a type of zero-pollution engine, but its conversion efficiency is very low for its high pressure exhaust which causes much exergy loss. In this study, a control system was developed to reduce the exhaust pressure of vehicle compressed air powered engine. The control system is made up of a controller, a pressure sensor, a photoelectric encoder, an inlet solenoid valve, and an exhaust solenoid valve. The controller receives the pressure signal of compressed air in cylinder from the pressure sensor and receives crank angle signal from photoelectric encoder, calculates when the solenoid valves should be opened or closed, and passes control signals to the solenoid valves. The simulation results indicate that the exhaust pressure can be controlled to be near to surrounding pressure by using this control system, and the exergy loss in exhaust stage can be avoided.
Dynamic characteristics of in-cylinder flow field in air-powered engine
The working process of air-powered engine was simulated using renormalization group(RNG) k-e turbulence model to give a view of energy distribution of inlet compressed air.Simulation represented the change of in-cylinder flow field and the behaviors of major parameters changing with crank angle,e.g.,cylinder pressure,turbulence kinetic energy and work output.Calculation results show that the perplexing turbulence around the inlet valve during the inlet process and exhaust are two primary factors resulting in energy losses,corresponding to 15.39% and 27.21% of the total energy when the engine speed is 1 500 r/min.Optimizing the structure of cylinder and inlet port and reasonably organizing inlet flow are far more important to air-powered engine,which can obviously improve the dynamic and economic characteristics of the engine.
Techno-economic analysis of chemical looping combustion with humid air turbine power cycle
Abstract Power generation from fossil fuel-fired power plant is the largest single source of CO2 emission. CO2 emission contributes to climate change. On the other hand, renewable energy is hindered by complex constraints in dealing with large scale application and high price. Power generation from fossil fuels with CO2 capture is therefore necessary to meet the increasing energy demand, and reduce the emission of CO2. This paper presents a process simulation and economic analysis of the chemical looping combustion (CLC) integrated with humid air turbine (HAT) cycle for natural gas-fired power plant with CO2 capture. The study shows that the CLC–HAT including CO2 capture has a thermal efficiency of 57% at oxidizing temperature of 1200 °C and reducer inlet temperature of 530 °C. The economic evaluation shows that the 50 MWth plant with a projected lifetime of 30 years will have a payback period of 7 years and 6 years for conventional HAT and CLC–HAT cycles respectively. The analysis indicates that CLC–HAT process has a high potential to be commercialised.