圖4-3 火焰穩(wěn)定和總的氣流圖形
Fig. 4-3 Flame stabilizing and general airflow pattern.
13．在汽化方式中(圖4-5)，燃油從供油管噴入位于火焰筒內(nèi)部的汽化管中。這些汽化管將燃油折轉(zhuǎn)180度，并且，隨著它們被燃燒所加熱時(shí)，燃油汽化，然后流入火焰筒。主空氣流流過帶著燃油的汽化管，同時(shí)也流入火焰筒進(jìn)口段中的許多孔，形成空氣“風(fēng)扇’的作用，將火焰吹得向后傾斜。冷卻和稀釋空氣經(jīng)限流后進(jìn)入火焰筒，其方式與進(jìn)入霧化式火焰筒相似。
11．燃燒室的設(shè)計(jì)和加入燃油的方式可有很大變化。但是，用來 影響和維持燃燒的空氣流分布卻總是與描述的情形極其類似。
燃油供應(yīng)
12．燃油用二種不同方式之一供入空氣流中。最普通的是用噴嘴(第10章)將霧化良好的燃油噴入回旋的空氣流中。第二種方式是讓燃油預(yù)先汽化，然后進(jìn)入燃燒區(qū)。
Combustion chambers
圖4-4 幾種火焰筒冷卻方式
Fig. 4-4 Flame tube cooling methods.
11. The design of a combustion chamber and the method of adding the fuel may vary considerably, but the airflow distribution used to effect and maintain combustion is always very similar to that described.
FUEL SUPPLY
12.
Fuel is supplied to the airstream by one of two distinct methods. The most common is the injection of a fine atomized spray into the recirculating airstream through spray nozzles (Part 10). The second method is based on the pre-vaporization of the fuel before it enters the combustion zone.
13.
In the vaporizing method (fig.4-5) the fuel is sprayed from feed tubes into vaporizing tubes which are positioned inside the flame tube. These tubes turn the fuel through 180 degrees and, as they are heated by combustion, the fuel vaporizes before passing into the flame tube. The primary airflow passes down the vaporizing tubes with the fuel and also through holes in the flame tube entry section which provide 'fans' of air to sweep the flame rearwards. Cooling and dilution air is metered into
the flame tube in a manner similar to the atomizer flame tube.
TYPES OF COMBUSTION CHAMBER
14. There are three main types of combustion chamber in use for gas turbine engines. These are the multiple chamber, the tubo-annular chamber and the annular chamber.
Multiple combustion chamber
15.
This type of combustion chamber is used on centrifugal compressor engines and the earlier types of axial flow compressor engines. It is a direct development of the early type of Whittle combustion chamber. The major difference is that the Whittle chamber had a reverse flow as illustrated in fig. 4-6 but, as this created a considerable pressure loss, the straight-through multiple chamber was developed by Joseph Lucas Limited.
16.
The chambers are disposed around the engine (fig. 4-7) and compressor delivery air is directed by ducts to pass into the individual chambers. Each
蒸發(fā)式冷卻
多個(gè)單管燃燒室
15．這種燃燒室用于離心壓氣機(jī)發(fā)動(dòng)機(jī)和早期型別的軸流壓氣機(jī)發(fā)動(dòng)機(jī)中。它是早期型惠特爾(Whittie)燃燒室的直接發(fā)展。其主要區(qū)別是惠特爾燃燒室有回流。如圖4-6所示。但是，由于這造成相當(dāng)大的壓力損失，約瑟夫-盧卡斯公司便發(fā)展了這種通流多個(gè)單管燃燒室。
燃燒窒的類型
14．用于燃?xì)鉁u輪發(fā)動(dòng)機(jī)的燃燒室有三種主要類型。即多個(gè)單管燃燒室、環(huán)管形燃燒室和環(huán)形燃燒室。
16．這些燃燒室布置在發(fā)動(dòng)機(jī)周圍(圖4-7)，壓氣機(jī)出口空氣用管道引入一個(gè)個(gè)單獨(dú)的燃燒室中。每一燃燒室內(nèi)部均有一個(gè)火焰筒，圍繞它的是空氣機(jī)匣。空氣流入火焰筒的錐形進(jìn)口，并且流入火焰筒和外機(jī)匣之間的空間，其情形已如第6段所述。
17．單獨(dú)的火焰簡互相連接，這使所有火焰筒在同樣的壓力下工作，并且，使燃燒在發(fā)動(dòng)機(jī)起動(dòng)期間傳
遍所有火焰簡。
氣化管
二股氣流管
燃油供油管
渦輪導(dǎo)向器葉片
火焰筒
稀釋空氣孔
Combustion chambers
圖4-5 一種汽化式燃燒室
Fig. 4-5 A vaporizer combustion chamber.
chamber has an inner flame tube around which there 17. The separate flame tubes are all interconnect-is an air casing. The air passes through the flame ed. This allows each tube to operate at the same tube snout and also between the tube and the outer pressure and also allows combustion to propagate 漩渦葉片
空氣機(jī)匣
聯(lián)焰管
燃?xì)馀艢夤?br />
噴嘴
火焰筒
壓氣機(jī)出口
氣慮
冷卻空氣孔
短管
主燃燒區(qū)
casing as already described in para. 6. around the flame tubes during engine starting.
圖4-6 一種早期的惠特爾燃燒室
Fig. 4-6 An early Whittle combustion chamber.
環(huán)形燃燒室
19．這種燃燒室有一個(gè)火焰筒，其形狀完全是環(huán)形的，裝在內(nèi)外機(jī)匣之間(圖4-9)。流過火焰筒的氣流與已經(jīng)描述的情形類似，燃燒室前部向壓氣機(jī)敞開，而后端則連接渦輪導(dǎo)向器。
20.環(huán)形燃燒室的主要優(yōu)點(diǎn)是，就同一功率輸出而
言，燃燒室的長度只有同樣直徑的環(huán)管形系統(tǒng)長度的75％，大大節(jié)省了重量和生產(chǎn)成本。另一優(yōu)點(diǎn)是消除了各燃燒室之間的燃燒傳播問題。
21．與環(huán)管燃燒系統(tǒng)比較，與之相當(dāng)?shù)沫h(huán)形燃燒室的壁面積少得多，因而，防止火焰筒壁燒穿所要求的冷卻空氣量大約也少15％。冷卻空氣量的這一減少將燃燒效率(笫27段)提高，因此實(shí)際上消除了未燃燒的燃油，并將一氧化碳氧化成無毒的二氧化碳，從而減少了對(duì)空氣的污染。 中國航空網(wǎng) www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：勞斯萊斯噴氣引擎－中英(20)
