首页
登录
职称英语
Fire can be thought of as any combustion process intense enough to emit light
Fire can be thought of as any combustion process intense enough to emit light
游客
2023-09-13
25
管理
问题
Fire can be thought of as any combustion process intense enough to emit light. It may be a quietly burning flame or the brilliant flash of an explosion.
A typical combustion process is the burning of gasoline in an automobile engine. The vaporized fuel is mixed with air, compressed in the engine’s cylinder, and ignited by a spark. As the fuel flames up, the heat produced flows into the adjacent layer of unburned fuel and ignites it. In this way a zone of first spreads throughout the fuel mixture until the combustion wave.
The speed at which such a combustion wave travels through a fuel mixture is called the burning velocity of the mixture. The burning velocity of a gas such as methane quietly burning in air is only about one foot per second. By comparison, the burning velocity of more reactive combinations such as the rocket fuels, hydrogen and fluorine, can be hundreds of feet per second.
If the fuel flows at the same speed as the combustion wave, the result is a stationary flame, like the one in your kitchen gas burner. In the kitchen burner a jet of gas mixed with airflows from the openings in the head of the burner. If the velocity of the fuel mixture flowing from the opening is greater than its burning velocity, the flame blows out.
In jet engines speeding through the air at 500 to 600 miles per hour, the engine’s flame is sometimes blown out by the blast of air entering the combustion chamber at high speeds. Jet pilots call this condition "flameout."
Combustion can sometimes occur very slowly. A familiar example of slow combustion is the drying of ordinary oil based paint. In this chemical reaction, called oxidation, the oxygen in the air reacts with the drying oil in the paint to provide a tough film. The linseed oil molecules link together, forming an insoluble coating. Another example is the hardening, and cracking of rubber with age. One way to avoid this is to incorporate certain chemicals called inhibitors into the compound.
How can the chemical reaction involved in such a quiet process as the drying of paint also produce spectacular flames and explosions? The main difference between the two is the temperature at which they occur.
At lower temperatures the reaction must take place over a long time. The heat, which is slowly produced, is dissipated to the surroundings and does not speed up the reaction. When the heat produced ’by the low temperature reaction is retained instead of being dissipated, the system breaks into flame. This is the process that accounts for a major fire hazard, spontaneous combustion, as when oily rags suddenly burst into flame.
In a flame or explosion, the reactions are extremely fast. In many chemical processes, however, such a rapid oxidation process would be extremely destructive. [br] Rocker fuels are more explosive than methane gas because of ______.
选项
A、the temperature at which combustion takes place
B、the degree of oxidation accomplished by the combustion process
C、the presence of inhibitors
D、the great burning velocity
答案
D
解析
细节定位题。A:因为引致燃烧发生的温度;B:伴随着燃烧过程的氧化程度;C:因为加人了抑制剂;D:燃烧速度很高。第3段后两句是:The burning velocity of a gas such as methane quietly burning in air is only about one foot per second.By comparison,the burning velocity of more reactive combinations such as the rocket fuels,hydrogen and fluorine,can be hundreds Of feet per second.意思是:气体如甲烷在空气中的燃烧速度仅为每秒钟一英尺左右,而像火箭燃料、氢气和氟等的反应性更强的混合物的燃烧速度则是每秒钟数百英尺左右。因此,可以选出,D正确。
转载请注明原文地址:https://tihaiku.com/zcyy/3010995.html
相关试题推荐
【S1】[br]【S5】A、intensiveB、absorbedC、intenseD、concentratedC词义辨析题。intense意为“强
【S1】[br]【S7】在popular后加enough“形容词+enough+动词不定式”的固定结构常用于表示“……得足够……”,结合句意可知,应在pop
Culturalnormssocompletelysurroundpeople,sopermeatethoughtandaction,
______(她对伤疤很敏感)andthoughteveryonewasstaringather.Sheisverysensitivea
Runningaleverwasoncethoughttobetheprerogativeofwarm-bloodedcreat
Runningaleverwasoncethoughttobetheprerogativeofwarm-bloodedcreat
Runningaleverwasoncethoughttobetheprerogativeofwarm-bloodedcreat
PartyRandomThoughtsLastnight,press
PartyRandomThoughtsLastnight,press
PartyRandomThoughtsLastnight,press
随机试题
SummaryListentothepassage.Forquestions26-30,completethenotesusingno
Itcouldbearguedthathumanbeingsareaspeciesofanimal.However,theu
NationalSpellingBeeEveryyear,thebestyoung【T1】______fromaroundt
OnJuly16th,1993,theCathyExpertCorporationofBeijingsoldtotheSouth
下列水溶液不稳定可分解产生甲萘醌沉淀和亚硫酸氢钠的维生素是A.维生素A B.维
属于产褥感染的项目,正确的是A、产褥期病原体侵入全身任何组织、器宫和系统,造成的
属于组胺受体阻断药,并被用作镇静药或者麻醉辅助药的吩噻嗪衍生物是A.普罗吩胺
根据我国《行政许可法》《行政强制法》等相关法律法规,下列执法行为正确的是:A.周
甲公司为汽车生产企业,由于资金周转出现问题,遂与A银行订立借款合同,同时,双方签
RNA聚合酶Ⅱ(TFⅡ)中能与TATA盒直接结合的是 A、TFⅡA B、
最新回复
(
0
)