CN113212726A

CN113212726A - Application of propane as airship buoyancy gas flame retardant, airship buoyancy gas and airship

Info

Publication number: CN113212726A
Application number: CN202110533737.XA
Authority: CN
Inventors: 王金华; 代鸿超; 蔡骁; 赵浩然; 黄佐华
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2021-05-17
Filing date: 2021-05-17
Publication date: 2021-08-06

Abstract

The invention relates to the field of combustion science, provides a propane flame retardant for airship buoyancy lift gas, provides a blending amount of 2-5%, and in the range, hydrogen and propane are blended to be used as airship buoyancy lift gas, so that the combustible range is obviously reduced, and the safety is greatly improved. And the density of the mixed gas as buoyancy lifting gas is equivalent to or even smaller than that of helium, and the hydrogen safety and the buoyancy can reach the optimal balance effect within the range.

Description

Application of propane as airship buoyancy gas flame retardant, airship buoyancy gas and airship

Technical Field

The invention belongs to the technical field of combustion science, relates to fuel suitable for aircrafts using buoyancy-rising gas such as airship and the like, and particularly relates to application of propane as a fire retardant of the buoyancy-rising gas of the airship, the buoyancy-rising gas of the airship and the airship.

Background

The airship plays an important role in various application scenes such as high-altitude monitoring, air transportation, air operation and the like. The buoyancy gas in the airship air bag is firstly hydrogen, but hydrogen is active, the combustible limit is wide, especially the rich combustion limit is high (about 75%), namely once the air bag leaks air, the hydrogen concentration is lower than the hydrogen concentration and can explode when encountering open fire (about 0.02mJ), and then helium with stable properties is used as the buoyancy gas, but the helium resource in China is short, and the preparation cost is high. With the wide popularization of hydrogen as a carbon-free clean fuel in recent years, hydrogen has an endless preparation source and a price advantage far lower than that of helium, people try to add a flame retardant into hydrogen to reduce the rich combustion limit of mixed gas and reduce the explosion risk when an air bag leaks, so that hydrogen is used as reliable buoyancy lift gas for airship flight again. At present, as for combustible gases, one of the commonly used flame retardants is a diluent gas such as N2, Ar, etc.; the other is non-flammable halogenated hydrocarbon, which means that hydrogen atoms in the alkane are partially replaced by halogen atoms, and includes halogenated hydrocarbon with bromine atom, halogenated hydrocarbon with chlorine atom, halogenated hydrocarbon with fluorine atom and the like; the other is a combustible unsaturated hydrocarbon gas, typically isobutylene, propylene, ethylene, and the like. The diluent gas is used as a flame retardant, and the gas is prevented from burning through the effects of dilution, isolation and cooling, but the range of the flammable limit of hydrogen is not reduced, and the density of the mixture is reduced; the non-flammable halogenated hydrocarbon is to replace hydrogen atoms in alkane with halogen atoms, and comprises halogenated hydrocarbon with bromine atoms, halogenated hydrocarbon with chlorine atoms, chlorinated hydrocarbon with fluorine atoms and the like, but the flame retardant has certain chemical corrosivity on materials such as rubber and metal, and the halogenated hydrocarbon with bromine and chlorine atoms can destroy the ozone layer, and is forbidden at present.

Disclosure of Invention

In order to overcome the disadvantages of the prior art, the invention aims to add propane serving as a flame retardant into the buoyancy gas, and the propane serving as the flame retardant is added into the buoyancy gas, so that the buoyancy conditions of aircrafts such as airship and the like are met without reducing the flammability limit range, and the buoyancy gas is not corrosive and does not destroy the ozone layer.

In order to achieve the purpose, the invention adopts the technical scheme that:

the propane is used as a flame retardant for the buoyancy lift gas of the airship.

The airship buoyancy gas consists of hydrogen and propane, wherein the propane is mixed in an amount of 2-5% in terms of molar content.

The mixing amount of the propane is 4.7 percent

The hydrogen and propane are premixed prior to filling the airship.

The invention further claims an airship using the airship to float gas.

Compared with the prior art, the invention has the beneficial effects that:

1. under the condition of not reducing the density of the uplifted gas, the propane is added as a flame retardant to reduce the rich combustion limit of the mixed gas and reduce the deflagration pressure of the hydrogen, thereby controlling and reducing the combustible range and the explosion danger of the hydrogen. The explosion limit of propane is only 2.1% -9.5%, and the combustion speed is much lower than that of hydrogen.

2. The invention carries out flammability limit test experiments and explosion pressure test experiments on the hydrogen and propane flame retardant blended gas, provides the optimal blending range of propane as the hydrogen flame retardant, directly blends the hydrogen flame retardant blended gas with the hydrogen flame retardant blended gas in a proportion of 2-5 percent for use, and the mixed gas has buoyancy equivalent to that of helium. The amount of air required for the mixed gas containing 4.7% propane to leak to reach the combustion limit is much higher than that of pure hydrogen, which shows that the combustion risk of the buoyancy lift gas of the airship can be greatly reduced by adding a small amount of propane as a flame retardant.

Drawings

FIG. 1 is a diagram showing the change of flammability limit of a mixture of propane and hydrogen mixed according to the present invention under normal temperature and pressure at an equivalence ratio of 1.

FIG. 2 is a graph showing the variation of flammability limits of different gas mixtures according to the present invention.

FIG. 3 is a graph of the ratio of air content to mixture content required for combustion to occur as a function of mixture density in accordance with the present invention.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the drawings and examples.

According to the invention, propane is used as a buoyancy lifting gas flame retardant for the airship, and in terms of a flame-retardant explosion suppression mechanism, the propane is mainly used as the flame retardant to eliminate active free radicals such as H, O, OH and the like, so that the overall reaction rate is reduced, and the flame-retardant explosion suppression effect is achieved.

In addition, since the combustion rate and flammability limit of propane are much lower than that of hydrogen, the risk of adding propane to the fuel mixture as a flame retardant is necessarily reduced with increasing flame retardant content, but considering that propane has a higher density than hydrogen, it is necessary to ensure that the density of the mixture is equal to or less than that of helium. Therefore, the optimum blending range is evaluated from both the combustible limit and the density of the mixture. The experimental analysis of the propane flame retardant from these two basic parameters is carried out using a constant volume bomb. After the flame retardant is added, the mixing ratio of the density of the mixed gas to the helium gas phase and the like is 4.7 percent, namely when the content of the propane is lower than 4.7 percent, the density of the mixed gas is lower than that of the helium gas, and the rising performance is better.

The invention is further illustrated by the following experimental results:

the flame retardant component is propane, the purity of propane and hydrogen used in the experiment is 99.99%, the molar content of the propane is 0%, 1.5%, 3%, 5%, 7%, 9% and 11%, and the experiment adopts a cylindrical constant-volume combustion bomb with an inner cavity length of 307mm and a diameter of 345mm as an explosion container to test the combustible limit change of the mixed gas. Before the experiment, a combustion bomb cavity is vacuumized, then air is respectively introduced according to the proportion of propane, hydrogen, oxygen and nitrogen, the air distribution temperature is kept at 303K, after the air distribution is finished, the combustion bomb is kept still and mixed for 10 minutes, an ignition synchronizer is adopted to realize electrode ignition, a high-speed camera and a pressure sensor are respectively adopted to record the propagation image and pressure of combustion, and the flammability is judged by flame propagation and pressure rise. The specific fire judgment standard is that the fire core can smoothly spread throughout the entire bomb-holding cavity and can acquire obvious pressure rise. And (5) carrying out 10 times of repeated experiments under each working condition, and if the mixed gas still does not burn, judging that the mixed gas under the working condition can not burn under normal temperature and normal pressure. As is evident from FIG. 1, the addition of a small amount of propane greatly reduces the rich limit, which has been reduced to about 50% with only 5% addition, thereby greatly reducing the flammability limit range, but with increasing addition, the flammability limit reduction also decreases. It is also evident from fig. 2 that: along with the increase of the proportion of the propane, the density of the mixed gas rises, and the density of the mixed gas can be ensured to be lower than that of helium only by keeping the content of the propane to be lower than 4.7 percent, so that the buoyancy effect of the mixed gas cannot be influenced. The combustible limit and the mixed gas density of the mixed gas are comprehensively considered, an ideal comprehensive effect can be achieved when the molar content of propane serving as a flame retardant in the mixed gas is 2% -5%, and the more ideal content value is 4.7%, so that the combustible range of the mixed gas can be obviously reduced, and the safety is greatly improved. And the density of the mixed gas mixed with the flame retardant as buoyancy gas is equivalent to or even smaller than that of helium. The range enables the safety and the buoyancy of the hydrogen to achieve the optimal balance effect.

As can be seen from fig. 3, when a 4.7% propane mixture leaks at normal temperature and pressure, combustion occurs only when the air content is 1.6 times the initial mixture content and an open flame is encountered; when hydrogen leaks, the air content is only 0.32 times of the hydrogen content, and combustion occurs, namely, the risk of combustion of the mixed gas can be greatly reduced by adding propane as a flame retardant.

When hydrogen is used as the airship buoyant gas and propane is used as the buoyant gas flame retardant, the airship can operate at room temperature, slightly negative pressure and in air (about 21% oxygen and 79% nitrogen) with narrower flammability limit and lower danger, the buoyant gas has higher economical efficiency because the buoyant gas mainly adopts hydrogen which is easy to prepare, and when the additive amount of propane added as the flame retardant is not more than 4.7%, the airship has larger buoyancy than the airship filled with helium under the same volume of the filled gas.

Claims

1. The propane is used as a flame retardant for the buoyancy lift gas of the airship.

2. The airship buoyancy gas is characterized by being formed by mixing hydrogen and propane, wherein the mixing amount of the propane is 2-5% in terms of molar content.

3. The airship uplift gas according to claim 2, wherein the propane is blended in an amount of 4.7%.

4. The airship uplift gas according to claim 2, wherein the hydrogen and propane are premixed before filling the airship.

5. An airship for buoyant lift of gas using the airship of claim 2.