Research On The Variable Valve System For Hybrid Pneumatic-Internal Combustion Engine

Aiming to improve the total energy efficiency, a concept of hybrid pneumatic-internal combustion engine is proposed to combine the merits of air powered engine and internal combustion engine. Although owning many aspects of advantages, the hybrid concept is still in its infancy and a lot of issues remain unsolved yet. It has a variety of operating modes. A variable valve system is designed and manufactured, in order to switch among multiple working modes of the concept engine.Currently, researches relevant with variable valve technology focus mainly on traditional internal combustion engine, while specific variable valve technologies for pneumatic-internal combustion hybrid engine are rarely seen. In this paper, different working forms of pneumatic-internal combustion hybrid are introduced, which are followed by the analyses of valve control strategies under four key operating modes. Taking low-speed condition of hybrid pneumatic mode as an example, an electro-hydraulic driven variable valve prototype is designed based on the simulation of pneumatic mode among different pneumatic-internal combustion hybrid operating modes with various timing and lift parameters. Moreover, variable valve control system is developed on NI-Compact RIO platform. Finally, the experimental analysis of electro-hydraulic driven variable valve is conducted preliminarily. Results show that:though there is dynamic response delay of valve lift, by regulating the opening and duration of electromagnetic valves, the optimal lift and timing strategy of the engine valve can be achieved to meet the needs of the pneumatic mode of the hybrid engine concept.Contents of this article are showed as follows:1. Based on the thermodynamic theories, mathematical model of the pneumatic-mode of pneumatic-internal combustion hybrid system is built. The impact of different valve parameters on the performance of the hybrid system pneumatic mode is simulated.2. According to the simulation results, design goals for variable valve to meet pneumatic mode are determined with a maximum speed1200r/min, intake duration angle180℃CA, and maximum valve lift5mm. Without using any return springs, an electro-hydraulic driven variable valve strategy is identified through analysis and comparison.3. According to the overall scheme of variable valve, mechanical actuator, hydraulic system and control system of the variable valve are designed and developed. Tests on the solenoid valve control method are conducted, and the optimal control parameters are settled.4. A variable valve test bench is set up and preliminary experiments are carried out to test the response performance of the variable valve system including the different inlet pressures and valve control signals. The test results indicate that the performance of the variable valve is qualified to meet the design requirements and common speed range requirements of pneumatic mode.