22．將空氣噴霧燃油噴嘴(第l0章)引入這種類型
的燃燒室大大改善了燃油為燃燒所做的準(zhǔn)備，因空氣會(huì)進(jìn)入靠近噴嘴處的燃油汽泡中，而這些泡都是過度富油的。這大大減輕了初始碳粒的形成。
環(huán)管形燃燒室
18．環(huán)管形燃燒室填補(bǔ)了從多個(gè)單管燃燒室過渡到環(huán)形燃燒室的空檔。多個(gè)火焰筒裝在一個(gè)共同的空氣機(jī)匣里(圖4-8)。氣流與已描述的情形相似。這種布局兼有多個(gè)單管燃燒室易于翻修和試驗(yàn)以及環(huán)形系統(tǒng)的緊湊性的優(yōu)點(diǎn)。
圖4-7 多個(gè)單管燃燒窒
Fig. 4-7 Multiple combustion chambers.
Tubo-annular combustion chamber
18. The tubo-annular combustion chamber bridges the evolutionary gap between the multiple and annular types. A number of flame tubes are fitted inside a common air casing (fig. 4-8). The airflow is similar to that already described. This arrangement combines the ease of overhaul and testing of the multiple system with the compactness of the annular system.
Annular combustion chamber
19. This type of combustion chamber consists of a single flame tube, completely annular in form, which is contained in an inner and outer casing (fig. 4-9). The airflow through the flame tube is similar to that already described, the chamber being open at the front to the compressor and at the rear to the turbine nozzles.
Combustion chambers
20.
The main advantage of the annular chamber is that, for the same power output, the length of the chamber is only 75 per cent of that of a tubo-annular system of the same diameter, resulting in consider-able saving of weight and production cost. Another advantage is the elimination of combustion propagation problems from chamber to chamber.
21.
In comparison with a tubo-annular combustion system, the wall area of a comparable annular chamber is much less; consequently the amount of cooling air required to prevent the burning of the flame tube wall is less, by approximately 15 per cent, This reduction in cooling air raises the combustion efficiency (para. 27) to virtually eliminate unburnt fuel, and oxidizes the carbon monoxide to non-toxic carbon dioxide, thus reducing air pollution.
22.
The introduction of the air spray type fuel spray nozzle (Part 10) to this type of combustion chamber
燃燒室性能
23.燃燒室必須能夠允許燃油在范圍廣泛的工作狀態(tài)有效地燃燒而不致產(chǎn)生巨大的壓力損失。此外，如果火焰熄滅了。它必須能夠重新點(diǎn)燃。在完成這些功能時(shí)，火焰筒和噴嘴霧化器部件必須在機(jī)械上是可靠的。
Combustion chambers
also greatly improves the preparation of fuel for combustion by aerating the over-rich pockets of fuel vapours close to the spray nozzle; this results in a large reduction in initial carbon formation.
COMBUSTION CHAMBER PERFORMANCE
23. A combustion chamber must be capable of allowing fuel to burn efficiently over a wide range of operating conditions without incurring a large pressure loss. In addition, if flame extinction occurs, then it must be possible to relight. In performing these functions, the flame tube and spray nozzle atomizer components must be mechanically reliable.
主空氣戽斗
24．燃?xì)鉁u輪發(fā)動(dòng)機(jī)按等壓循環(huán)工作，因而，燃燒過程的壓力損失必須保持在最低水平。在提供足夠的紊流和摻混時(shí)，總壓損失在燃燒室進(jìn)口空氣壓力的3～8％之間變化。
燃燒強(qiáng)度
25．由燃燒室或任何別的熱量發(fā)生裝置放出的熱量取決于燃燒區(qū)的容積。因而，為了獲得要求的高功率輸出，一個(gè)相當(dāng)小而緊湊的燃?xì)鉁u輪燃燒室必須以極高的放熱率放熱。
稀釋空氣孔
渦輪安裝邊
24. The gas turbine engine operates on a constant pressure cycle, therefore any loss of pressure during the process of combustion must be kept to a minimum. In providing adequate turbulence and mixing, a total pressure loss varying from about 3 to 8 per cent of the air pressure at entry to the chamber is incurred.
Combustion intensity
25. The heat released by a combustion chamber or any other heat generating unit is dependent on the volume of the combustion area. Thus, to obtain the required high power output, a comparatively small
圖4-8 環(huán)管形燃燒室
26．例如，在起飛狀態(tài)，一臺(tái)羅爾斯-羅伊斯公司的RB211-524發(fā)動(dòng)機(jī)每小時(shí)消耗20635磅燃油。這種燃油具有大約18550英國熱量單位／磅的熱值。因此，該燃燒室每秒釋放將近106300英國熱量單位的熱量。換言之，這種潛在的熱量消耗率相當(dāng)于大
約150000馬力。
圖4-9 環(huán)形燃燒室
Fig. 4-9 Annular combustion chamber.
and compact gas turbine combustion chamber must release heat at exceptionally high rates.
26. For example, at take-off conditions a Rolls-Royce RB211-524 engine will consume 20,635 lb. of fuel per hour. The fuel has a calorific value of approx-imately 18,550 British thermal units per lb., therefore the combustion chamber releases nearly 106,300 British thermal units per second. Expressed in
渦輪導(dǎo)向器葉片
燃燒室外機(jī)匣
Combustion chambers
another way this is an expenditure of potential heat
at a rate equivalent to approximately 150,000 horse-power.
Combustion efficiency
27. The combustion efficiency of most gas turbine
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