Structural Design and Numerical Analysis of the Electric Explosion

Valve for Quick-opening Marine Gas Cylinder

Rufeng Deng

, Yufeng Li

and Daizong Xiao

The 713 Research Institute of CSIC, Fuhua Street, Zhengzhou City, China

Keywords: Marine cylinder, the electric explosion valve, mechanical linkage, quick opening.

Abstract: To meet functional requirements of the electric explosion valve for quick-opening marine gas cylinder, a

quick, reliable and safe opening mechanism is designed, which is driven by electric explosion pressure. The

structures of electric explosion cavity and over-pressure exhaust are designed respectively to assure the fast

sex and security. The article analyses detonation pressure of squib start. The mechanics calculation and

strength check are conducted to the electric explosion valve

opening and closing. Finally, stress conditions

of the safety diaphragm are simulated and analyzed. The results indicated that the designed the electric

explosion valve of

quick-opening marine gas cylinders responds rapidly and stable performance that can

address the needs of the security, reliable and fast input for naval ship fire fighting system, rationality of the

mechanism design of the electric explosion valve is confirmed. It has much more practical value in

engineering.

1 INTRODUCTION

The electric explosion valve is the key component of

naval ship sprinkler system as a control valve and

plays a role in controlling gas in the system. After

research, it found that the universal electric

explosion valve is bulky, complex, slow response

and poor stability naval ship fire fighting system,

and it's difficult to meet the requirement of rapid

opening of pneumatic valves and other equipment in

special places such as ammunition depots and oil

depots, which affects the performance of the whole

spray system seriously. In this paper, a kind of the

electric explosion valve of quick-opening marine gas

cylinders is designed, which uses detonation

pressure caused by the electric explosion valve

detonation. Then the mechanism can be opened fast

by mechanical linkage between the components. It

characterize by its simple structure, small volume,

fast reaction speed, high reliability, etc.

2 FUNCTIONAL REQUIREMENTS

ANALYSIS

The marine cylinder is used to store compressed air

and provide a driving gas source for pneumatic

valve opening. The electric explosion valve can

realize starting control and media isolation of marine

cylinder. As an isolation valve, the electric explosion

valve is the key component of marine cylinder,

which is normally close on standby. Once request

signal is received, the electric explosion valve will

be detonated instantaneously, driving the valve body

to open. At this point, compressed air in the cylinder

discharge rapidly under the high voltage, achieving

the function of fast gas supply about marine

cylinder. The electric explosion valve is the key

component of the spray system , which directly

influence the vitality of naval vessel and various

high-risk places.

3 QUICKLY OPEN THE

ELECTRIC EXPLOSION

VALVE FOR MARINE GAS

CYLINDER

3.1 The Electric Squib

In general, marine cylinders are located in

equipment tanks or ship corridors, therefore, reliable

remote control is required when opening, so it is

necessary to provide the opening power. we adopt

ignition that is electric detonator in accordance of a

small footprint, fast opening speed, secure and

requirements. It has the characteristic by small

volume, light weight, great power and high

adaptability to circumstance.

On duty, once request signal is received, the

electric explosive valve will be detonated

instantaneously. The high-temperature and high-

pressure air produced by detonation with rapid

pressure rise. The electric explosion valve opens

mechanically under the action of the detonation

pressure of the electric detonator. Ignition timing of

the electric detonator tube can reach millisecond,

characterized by quick, powerful and small scope of

action. It can not only meet the need of quick

opening , but also ensure the safety and reliability of

use.

Figure 1: The structure diagram of electric tube.

3.2 Mechanism Design

According to the functional requirements and

characteristics of the electric detonation tube, the

electric explosion valve of quick-opening marine gas

cylinders is designed, which is mainly composed of

electric explosion cavity, safety diaphragm, piston,

crank, rotating shaft, pressure arm, valve core, etc,

as shown in Figure 2.

Figure 2: The schematic diagram of electric valve device.

(1) Electric explosion cavity

The electric explosion cavity is designed on the

electric explosion valve, and the effective isolation

was realized between the electric detonation

chamber and the valve body cavity. To ensure that

the gas flow into the piston cavity while the

explosion debris is isolated by the angle design

between the electric explosion cavity and the piston

bore. The electric detonation tube is installed on the

electric detonation chamber to ensure the rapidity of

the electric explosion valve.

Safety diaphragm

In order to prevent the cylinder from cracking

due to high pressure, over-pressure exhaust structure

is designed, the main principle of which is to install

the safety diaphragm in the over-pressure exhaust

structure. To ensure the cylinder intact and the

personal security, the safety diaphragm will burst

automatically, releasing the gas in the cylinder,

when pressure in the Marine cylinder exceeds the set

pressure value of 13MPa~15MPa.The design of

safety diaphragm realizes the security features of the

electric explosion valve. The schematic diagram of

the over pressure exhaust structure is shown in

Figure 3.

Figure 3: The diagram of over pressure exhaust structure.

3.3 Operating Principle

There are three types of working conditions: closing,

opening and inflating.

safety

(1) Closed state

Because the marine cylinder will supply the air

source for the pneumatic valve only when spraying,

the electric explosion valve is normally closed. In

the initial state, the detonator tube is not activated.

The crankshaft is driven to rotate, so that the shaft is

locked with the pressure arm, and then the pressure

bar is manually turned. At this point, the valve core

is pushed down and the vent is closed, so that the

valve is closed, as shown in Figure 4.

Figure 4: The diagram of electric valve closed state.

(2) On state

In case of danger, the electric explosion valve

should be opened reliably when the marine cylinder

needs to provide air source. At this point, the

detonator explodes when an electrical signal is

received. The resulting explosive pressure pushes

the piston up and the piston rod hits the crank. The

crank turns the shaft, forcing the shaft to separate

from the buckle of the press arm. The compression

force on the valve core is released, and the pressure

arm rotates, causing the pressure bar to turn over.

Meanwhile, the valve core moves up rapidly under

the action of spring force, the valve opens, and the

compressed air is sent out. The opening linkage

design of the electric explosion cavity, the spring

structure and the electric explosion valve mechanism

realizes the fast and reliable opening of the Marine

rapid opening gas cylinder electric explosion valve.

In addition to the electric detonation drive, Marine

quick-opening valve of cylinder can also be

manually opened by turning crank, as shown in

Figure 5.

open

Figure 5: The diagram of electric valve open state.

(3) Plenum

The marine gas cylinder needs to be refilled by

use or other reasons, which causes drop in pressure.

By Rotating the hand wheel, drive the needle valve

stem and make the needle valve center move to the

right. Finally, needle valve is open and the air vent is

connected to the cylinder(as shown in Figure 6). The

cylinder is filled with compressed air from air vent

by the ship's air source. The needle valve will be

closed when the pressure in the cylinder reaches the

set value. At this point, the ship's cylinder is in

normal standby.

Figure 6: The diagram of electric valve inflatable state.

4 NUMERICAL ANALYSIS

4.1 Analysis of Detonation Pressure

During Explosion of Electric

Detonator

The electric detonation tube contains detonators,

transition agents and main charge agents, including

C, H, N, O and other elements. Chemical reaction

equation of explosives:

abcd 2 2 2

11 11 11

CHNO cN bHO ( d b)CO (a d b)

22 24 24

→+ +− +−+

(1)

The explosive pressure of ammunition is related

to charge density, ammunition composition and

calculate reaction. Engineering calculation formulas

of detonation pressure:

Formula of explosive detonation velocity is as

follows.

Type: Pj is explosive pressure, GPa; ρ0 is

ammunition composition, g/cm3; D is detonation

velocity, km/s; φ is property value of ammunition;

N is the amount of gas produced per gram of

explosive, mol/g; M is the average molar mass of the

gas component of the explosive, mol/g; Q is the heat

of chemical reaction per unit of explosive, J/g.

Including:

48 4 56 64

cdb

ab c d

++ +

(5)

56 88 8

cdb

+−

(6)

120.9 197.7( )

12 14 16

bdbH

ab c d

+−+Δ

++ +

(7)

Type: △ Hf is the production enthalpy of

explosives, J/g.

Figure 7: The relationship between blast velocity and

powder density of TNT ammunition.

Figure 8: The relationship between blast pressure and

powder density of TNT explosive.

It can be seen from the above that explosive

property is closely related to charge density. As long

as charge density of explosives is mastered,

detonation speed and pressure of electric detonator

can be determined accurately.

4.2 Force Analysis and Strength Check

of Electric Explosion Valve

Mechanism

(1) Closed state

The electric explosion valve is closed when the

marine gas cylinder is on standby. At this point , the

valve body is balanced by the friction of the CAM

bite between the shaft and the pressure arm, as

shown in Figure 9.

Figure 9: Force analysis of pressure arm.

The force exerted by the valve core on the

pressure arm:

=+FFF

xt h

(8)

P1.558.

ϕρ

(2)

D=1.01 ( 1 1.3 )

ϕρ

(3)

(4)

=PF

tql

(9)

=Fkx

(10)

Type: Fx is the force of the valve core on the

pressure arm, kN; Ft is the force of air pressure on

the valve body, kN; Fh is the force of spring on the

valve core, kN; Pq is the pressure of the gas in the

cylinder, MPa; S1 is the area of action of gas on

valve body, m2; k is the spring coefficient, kg/mm; x

is the spring compression amount, mm.

By analyzing bearing condition of arm under the

closed state of the electric explosion valve, we find

force of the shaft on the pressure arm using the lever

principle.

L=FFL××

xxzz

(11)

Type: Fz is force of the rotating shaft on the

pressure arm, kN; Lx is distance from Fx to the

fulcrum, mm; Lz is distance from Fz to the fulcrum,

mm.

(2) On state

When the electric detonator receives a certain

current signal, the electric detonator ignites and

explodes, breaking the balance. By overcoming the

friction between the rotating shaft and the pressure

arm, the pressure arm rotates and the pressure arm is

separated from the rotating shaft. At this point, the

valve core can overcome the gravity of itself and the

pressure arm and the pressure bar and moves up

rapidly under the action of spring elastic force and

gas pressure in the cylinder. Results the compressed

air in the gas cylinder flows out through the valve

body outlet.

a. Force analysis

Since the crank is connected with the shaft by

solid state, they can be regarded as a whole, so the

crank bearing is the shaft bearing, as shown in

Figure 10.

Figure 10: Force analysis of the axis and crank.

L=F LF ××

kkf f

(12)

=F'F

(13)

Type: Fk is the opening force required for the

rotation of the rotating shaft, kN; Lk is the distance

from Fk to the fulcrum, m; Ff is the static friction

between the rotating shaft and the pressure arm; Lf

is the distance from Ff to the fulcrum point; F'z Is

the force exerted by the pressure arm on the rotating

shaft; μ is the friction coefficient between the axis

of rotation and the pressure arm.

Between the axis of rotation and the pressure arm

is the force and the reaction force.

F=F'

(14)

Through equations (11), (12) and (13), the

opening force

required for the rotation of the

rotating shaft can be obtained.

F=P

(15)

Type:

is the area of action of electric detonator

explosion on piston.

When the explosion pressure is greater than the

of the opening force, the electric explosion valve can

be opened quickly in linkage.

Strength check

The strengths of crankshaft and spindle are

checked because they bear the maximum stress at

the moment of explosion pressure. Crankshaft and

spindle are stainless steel with the following

characteristic parameters:

a) Elastic modulus: E=2.06 * 1011Pa;

b) Poisson's ratio: u=0.3;

c) Yield strength: σs≥ 540MPa.

According to the conditions above, finite element

modeling is carried out for cranks and spindle. The

model size is in mm and the stress is in Pa, as shown

in Figure 11.

Figure 11: Finite element model of crank and shaft.

The forces of crankshaft and spindle are

analyzed, when a certain explosion pressure is

applied. The strengths of crankshaft and spindle can

meet the demand when the force of crankshaft is not

greater than its yield strength, so it is reasonable.

The detonation pressure of the electric detonator

tube is about 15MPa, which imposes a constraint on

the contact surface of the rotating shaft and the

pressure arm. At the same time, 15MPa detonation

pressure is applied to the contact point between

crank and piston rod, as shown in Figure 12.

Figure 12: Pressure distribution of crank and spindle.

As you can see from the figure above, the

maximum stress value of crankshaft and spindle is

413MPa, which less than yield strength. The results

demonstrate that it meets the requirements of design .

4.3 Simulation Analysis of the Safety

Diaphragm

The safety of the safety diaphragm is determined by

blasting under certain pressure. Blasting can be

realized when pressure is greater than tensile

strength.

In order to ensure that the gas pressure can be

discharged safely between 13MPa to 15MPa, the

appropriate safety diaphragm needs to be selected.

The pressure resistance of the safety diaphragm is

related to its materials and thickness. Here, the

material of the safety diaphragm is tin bronze, and

its characteristic parameters are as follows.

a) Elastic modulus: E=1.24 * 1011Pa;

b) Poisson's ratio: u=0.34;

c) Tensile strength: σb= 700-800MPa.

According to the conditions above, finite element

modeling and force analysis are carried out for the

safety diaphragm.The model size is in mm and the

stress is in Pa. As the thickness of the safety

diaphragm is only 0.1 mm, shell element PLANE63

is adopted. One side of the safety diaphragm is

restrained from contact with the pressure ring, and

different forces are applied on the other side, as

shown in Figure 13.

a)12MPa.

b) 13MPa.

c) 15MPa.

Figure 13: Pressure distribution under different pressure of

the safety diaphragm.

As you can see from the figure above, the contact

part between the safety diaphragm and the pressure

ring has the maximum force. At 12MPa, the

maximum stress is 680MPa, less than σb, then the

safety diaphragm does not burst; At 13MPa, the

maximum stress is 736MPa. Within the range of

tensile strength, so it may be blasting; At 15MPa, the

maximum stress is 849MPa, more than σb, which

satisfies the blasting condition.

5 CONCLUSIONS

The electric explosion valve for quick-opening

marine gas cylinder is one of the important parts of

spray system. In this paper the following

conclusions are made through mechanism design

and numerical analysis:

(1) The mechanism is designed with electric

explosion chamber and over-pressure exhaust

structure. By means of electric detonation tube drive,

spring structure, lever principle and mechanical

linkage, the electric detonation valve can be. Some

features including reliable closed, security

inflatable and rapid opening quickly are

implemented.

(2) It is proved that the characteristics of the

electric explosion valve are simple structure, little

volume, quick response and high reliability through

numerical analysis of the closed and open state of

the valve mechanism, and strength check of

crankshaft and spindle with the maximum force..

(3) The safety of the valve is verified through the

finite element simulation analysis of the force of the

safety diaphragm. At the same time, the electric

explosion is a more practical marine mechanism and

recycled.

(4) The electric explosion valve for quick-

opening marine gas cylinder can be applied to

marine compressed air cylinder. In addition, the

method of mechanism design and numerical analysis

can also be applied to the design of valve body

structure on marine cylinders such as inert gas,

corrosive gas and various liquids.

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