How to model the opening and closing of valves?

[amare]

ok guys ! i need to edit this question ! I have an iris type of valve that is installed between the throttle valve and the intake manifold to restrict flow. the valve is to be fully closed and fully opende based on need. there is no partial opening something like that. what i need is the mathematical equations for the flow rate of air that come from the throttle valve and blocked by the iris valve so that there will not be flow to the intake manifold. i have equations for the mass flow rate of air that come from the throttle valve. but the air will be blocked by the iris valve if the iris valve is in a closed state. how do i drive expression for the air flow inthe intake manifold is zero and the engine will stop ? the attached images are fully open and fully closed conditions of the valve. you can have a look on the youtube link also...

 

[Asymptotic]

Can't help with the mathematical modeling, but you'll have to be very specific about the type of valve (ball valve, needle valve, gate valve, etc.). They all behave differently.

 

[jrmichler]

When you have two valves in series, you have to calculate the flow by considering the resistance to flow of both valves at the same time. This is easy if one of the valves is always fully open or fully closed. When the iris valve is fully open, the throttle valve controls the flow. When the iris valve is fully closed, it controls the flow (to zero).

Because you have two separate conditions, your model needs a separate equation for each condition.

 

[amare]

do you help me with the equations please?

When you have two valves in series, you have to calculate the flow by considering the resistance to flow of both valves at the same time. This is easy if one of the valves is always fully open or fully closed. When the iris valve is fully open, the throttle valve controls the flow. When the iris valve is fully closed, it controls the flow (to zero).

Because you have two separate conditions, your model needs a separate equation for each condition.

could you please help me with the equations? the throttle valve is always fully open and the iris valve is closed and opened based o condition. normally the problem is when the flow is restricted by the iris valve , the air flow to the manifold will be restricted and from the model of the manifold pressure i get a negative value... which i do not understand it...

 

[jrmichler]

I hope that you are in the Mechanical Engineering program at your university. If so, the equations by themselves will not make sense until you have had your class in fluid dynamics. After the class in fluid dynamics, you will know the equations. Much more importantly, you will understand them.

Spend some time thinking about the cases of iris valve fully open, and iris valve fully closed. What is the throttle valve doing in each case? Visualize the flow situation and do not even think about equations when you do this. You need to understand what is happening before you can properly apply an equation, or understand the results of the equation(s).

Hint: If the iris valve is closed, what is the flow through the throttle valve? What is the expression for that flow? Does the throttle valve have any effect on the flow when the iris valve is closed?