引擎排氣管原理與概論(2行程汽油)

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How a tuned pipe works

排氣管的運作原理
In the 1950's an engineer by the name of Walter Kaadan was consulted by motorcycle racers asking him to help them squeeze more power and speed out of their motorcycles.
一位名叫瓦特卡登的工程師,於1950年代成為賽車手們諮詢如何幫助他們的賽車擁有更強的爆發力及速度的對象.
After some experimentation, he found that the 2-stroke engines in motorcycles were affected by its exahaust characteristics. He found that by varying the length of straight exhaust pipes, the performance also changed accordingly. After further experimentation, he found that a divergent cone instead of a straight pipe worked better, and this heralded the arrival of the 2-stroke tuned pipe.
在許多的實驗後,他發現二行程引擎是受到它的排氣特性.在多種不同長度的排氣管下,會有不同的表現. 在更進一步的實驗下,他發現以圓錐體來替代直筒排氣管表現更佳,然而這也預知著二行程引擎來臨的時刻.
Tuned Pipe Principles
排氣管原理
The basic principle of the tune pipe is making use of the moving air masses in the exhaust to assist in the scavenging (the process whereby the exhaust gases are removed and replaced with unburnt mixture) of a 2-stroke engine.
排氣管的基本原理是運用大量的流動空氣進氣來促進排出廢氣(它的過程是籍著排出汽體來分離及取代未燃的混合氣)此為二行程引擎原理．
Each time the exhaust port of a 2-stroke cylinder is uncovered, exhaust gases rush out of the opening and through the exhaust pipe. This causes a high pressure wave to radiate out of the pipe towards the exhaust opening.
在每次排氣時二行程引擎的氣缸是未覆蓋的,排出的氣體會快速通過排氣管. 這是因為上方壓波朝向排氣開口射出氣管.

However, the momentum of this moving mass of air also creates a low pressure wave that follows behind it. If this is carefully timed, this low pressure wave can be used to suck in the fresh fuel/air mixture from the transfer ports.
但是,這大量流動氣體的衝力也會製造一個下方壓波並跟隨著上方壓波. 在此時下方壓波能由transger port活塞吸入新鮮的燃料/空氣混合.
This process repeats itself at the same frequency at which the engine is running and thus, if the exhaust pipe can be made to resonate at the operating RPM of the engine, this will improve the engine's efficiency.
因此這重覆的自我進氣壓縮過程在相同頻率的引擎運轉下,如果排氣管可使引擎的每分鐘轉數產生共振,那這將提升引擎的效能.
It must be noted that at a low (lower than the resonant frequency) RPM range, this low pressure pulse would return too soon, bouncing back out exhaust port. The converse is true for an RPM range higher than the pipe's resonant frequency, whereby the low pressure pulse returns too late such that the exhaust port is closed.
這裡必須注意的是,一個低轉數範圍(低於共振的頻率),這樣的下壓縮會快速的衝回,跳躍出排氣口. 而反向的每分鐘轉數範圍高於氣管共振頻率,則會使下壓縮很慢速的衝回以致關閉.
It should be noted that the length of the pipe is what determines the operating characteristics of the pipe and this is independent of the engine's capacity.
應該注意的是,一個排氣管的長度將決定引擎運轉的特色,而且它是不受引擎cc數所支配.

The Divergent Cone Pipe
外擴的圓錐氣管
he next stage in the development of the tuned pipe consisted of adding a divergent cone instead of a fixed diameter pipe. This had the effect of lengthening the duration of the low pressure pulse, however it was not as strong as that of a fixed diameter pipe. As the low pressure pulse was stretched to a longer time frame, this gave it a higher chance of finding the exhaust port open. The pressure was still sufficient to suck the exhaust out and a new charge into the cylinder. Hence, the power band was somewhat broadened as the engine could work over a wider range of RPM's.
下一步的發展是由增加一個外擴的圓錐形氣管來代替一個固定直徑排氣管.這會延長下壓縮的過程,但是它不會像固定直徑排氣管般強勁.因為下壓縮會延伸振幅,此時會給與更高的機率促使氣孔打開. 這壓力仍足夠排氣以及新的衝力進入氣缸. 因此,動力聚集是某種程度的擴大,就像引擎能運轉超越每分鐘最大的轉數的範圍.
The Twin Cone Tuned Pipe
雙圓錐氣管
There is a problem in the design of the divergent cone tuned pipe. At low RPM's the stretched out low pressure pulse created by the divergent cone arrived at the exhaust port early and it not only manages to scavenge all the exhaust gases but also sucks some fresh charge out of the cylinder via the exhaust port.
外擴的圓錐形氣管在設計上有一個問題.在低轉數的向外延伸下壓縮,是籍由製造外擴圓錐提早到達排氣口,而且它不只是管理所有廢氣的排出,也是吸進新鮮混合氣衝出氣缸的通道.

At this point, a second convergent cone was added after the divergent cone. When designed properly, this convergent cone the initial positive pressure pulse back to the exhaust port thereby pushing the fresh charge back into the cylinder just before the exhaust port closes. This in effect acts like a supercharger with no moving parts and it improves the engine's performance significantly.
在此之下,再加上一個漸縮圓錐於外擴圓錐之後. 當擁有精確的設計,這圓錐的開頭正面壓縮回氣口,因此促使新鮮混合氣在氣口關閉前衝回進入氣缸. 這個實行中扮演了如同一個沒有移動氣口的增壓器並且提升了引擎的表現.
Stinger

The stinger section of the tuned exhaust acts as a bleed valve, allowing exhaust gases to escape. This is usually acheived by a pipe connected to the end of the convergent cone. In some pipe designs, the convergent cone opens to a second chamber and the stinger pipe is connected to this chamber.

Stinger在諧和管中扮演著如同氣閥的角色,准許排氣.這通常是在氣管連接漸縮圓錐的尾端.在某些氣管的設計中,這個漸縮圓錐打開第二氣室以及stinger氣管得已連接此氣室.

The stinger also affects the performance characteristics of the engine by controlling the amount of back pressure within the tuned pipe. The increased pressure helps as the pressure waves travel at the speed of sound and the speed of sound increases in a dense medium.
這stinger也影響了引擎控制大量回壓至諧和管內的表現特性.這個增壓幫助了像是,壓力波的聲音傳導,也增加了聲音密集的傳導.
This helps as when the engine RPM increases the pressure within the exhaust created by the stinger also increase due to the larger anount of exhaust gases generated. This allows the pressure waves to travel faster and the overall exhaust timing is improved over a larger range of RPM's, hence the power band of the engine is broadened.
這也幫助了, 當引擎的轉速增加壓力在排氣之中,因為大量的排氣因此被生產.這使得壓波傳導更快並且全部的排氣時間也提升超越一個更大的轉速範圍,因此這能量的聚集是被擴大的.

  

  

[ 本帖最後由 dvd30370 於 2006年9月29日 11:21 AM 編輯 ]

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