# Design of a Solenoid Actuator for a Cylinder Valve in a Fuel Cell Vehicle
## 1 Introduction  
In recent years, growing concerns regarding environmental pollution have recently increased the demand for green vehicles. Green vehicles include electric vehicles, natural gas vehicles, fuel cell vehicles (FCV), and vehicles running on fuels such as a bio diesel or an ethanol blend. Fuel cell vehicles are driven by electric power made through electrochemical reactions between hydrogen and oxygen that generate water. These vehicles do not emit any contaminants such as CO\({}_{2}\), HC and NOx since the operation principles of fuel cells do not include any combustion reaction. These vehicles show very high energy conversion efficiency because they do not use any driving part that makes reciprocating motions, such as pistons in engines. However, to extend their range and secure their competitiveness against other fuels, the storage capacity of hydrogen gas needs to be increased by compressing it up to an ultra-high pressure of 700 bar [1,2].  
When storing and using fuel at ultra-high pressure, securing the safety of the cylinder and cylinder valves is very important. For the safety of the cylinder, a high-strength aluminum liner used as an internal vessel, was produced by extrusion and auto frettage processes and then laminated with carbon fiber on the outer wall [3]. The cylinder valve is the main component of the cylinder in the fuel control system of the FCV. It is composed of a manual manipulation device for opening and closing the flow path, a solenoid actuator, a temperature sensitized pressure relief device, and an overflow blocking device to secure safety against leakage and fire.  
Solenoid actuators are energy conversion devices that first convert electric input signals into electromagnetic energy through a coil and output mechanical kinetic energy to open and close the flowpath through a magnetic pole formed by a core and plunger [4]. Solenoid actuators have been widely used for their good performance of simple structure, fast response, energy conservation, economic feasibility, and favorable stability. As an emerging process in the automobile industry, electronic fuel injection systems of internal combustion engine are using solenoid actuators for reduction of fuel consumption and hazardous exhaust emissions [5,6]. There are growing demands for high frequency response, reduction of actuation forces, and strong anti-pollution capabilities of electro hydraulic control system [7,8].  
In the case of solenoid actuators, for the cylinder valve of the FCV has to work in an environment of ultra-high pressure and have reliability of motion for the fuel supply. Designing solenoid actuators for cylinder valve applications has been the focus of research recently, and it is one of the key technologies of FCV [9]. Solenoid actuator design requires the necessary maximum attractive force considering safety factors, magnetic flux density analysis, the shape of the solenoid actuator, and the calculation of the number of windings while considering temperature rises [10]. In the present study, a solenoid actuator was designed while considering mobility under ultra-high pressure conditions and temperature increase using heat transfer analysis and electromagnetic field analysis. Performance evaluation tests were also conducted to validate the actuator.