Lesson 1. Petrol and Diesel Engines汽油發動機機和柴油發動機 The explosive mixture of the petrol engine is provided by a carburettor, but in the case of the diesel engine the supply is effected by an injection or jerk pump which forces a shot of fuel into each cylinder in turn according to the correct firing sequence.翻譯：汽油發動機由一個化油器輸送可燃混合氣體，而柴油發動機，由一個噴射泵或柱塞式燃油泵實現燃油供應，此泵根據正確的點火順序把少量燃油依次壓入每個汽缸。 The pump is actuated from a camshaft and the amount injected for each power stroke is extremely small at maximum output, indeed it may be less than 0.1 cm2 , Moreover, this charge must be metered with great and constant accuracy even while it is being variably controlled to regulate power from idling to maximum. It will be realised that efficient and economical running is largely dependent upon the fuel pump.翻譯：通過凸輪軸驅動油泵。每個功率沖程的燃油噴射量在最大輸出功率時是非常微小的，實際上，可能小于0.1 cm2。而且，此燃油量雖然從怠速到最大速度要進行不同的控制調節，但此燃油量必須非常精確和穩定地進行測量。人們認識到有效和經濟的運行主要依靠燃油泵 Multi-cylinder engines are normally equipped with pumps in unit monobloc form incorporating a corresponding number of elements，having a common camshaft and control means but provided with individual adjustments for regulating their output and setting their timing . An equal quantity of fuel must be delivered by each element, which is calibrated separately to a predetermined rate of delivery. Timing of the start of injection in relation to engine crankshaft position must also be constant and equal on each element, the setting process is called phasing. Calibration and phasing are precision operations to be carried out only by skilled service mechanics who have the necessary specialised equipment.翻譯：多汽缸發動機一般情況下裝配整體式油泵，把相關的噴射單元組合成一體，共用凸輪軸和控制方式，但可單獨調整以調節各自功率輸出和設定各自的正時。 每個噴射單元必須輸送等量燃油,按照預定的輸送比率分別校準。 與發動機曲軸位置度相關的噴射開始時間在每個噴射單元也必須是恒定相等的。設定的過程被稱為調整相位。 校準和調整相位是精確的操作，只有熟練的服務機械師用必要的專用工具才能進行， A very important detail is that injection must cease cleanly and abruptly at the end of the delivery period without any trace of after-dribble from the injector; otherwise carbon deposits quickly form on the nozzle tip and excessive smoke will appear in the exhaust. The required condition is ensured by the special design of the pump delivery valves which provide for a very rapid collapse of pressure in the injector fuel pipes at the end of injection翻譯：一個非常重要的細節是燃油噴射必須在燃油輸送結束時干凈且突然地停止，從噴射泵上不留下任何后滲漏的痕跡。否則，在噴嘴尖上很快形成積碳，排氣管將冒濃煙。這種要求由專用（專門設計的）輸油泵輸送氣閥來保證，此氣閥可以在噴射結束時快速終止噴射泵燃油管的壓力。 At an early stage in the evolution of the high-speed diesel a variable timing device was introduced in the pump drive coupling, taking the form of a helically splined coupling by means of which the angular relation between driving and driven shafts could be varied by manual or automatic control. This device has always been a feature of Gardner engines where it is coupled to the accelerator control. In some makes of engine the helically splined coupling is not used and the angular displacement of the shafts is effected by centrifugally actuated devices of the swinging link or inclined plane type. The fitting of variable timing devices has been discarded by some manufacturers in favour of fixed timing, but in recent years the extensive adoption of the distributor type of fuel pump, which incorporates a simple variable timing device, has now brought this refinement into much more general use. 翻譯：在高速柴油機發展的早期，可變的正時裝置被引用到油泵驅動聯軸節上，采用螺旋式花鍵套管的形狀，驅動軸和從動軸之間的相對角度可以通過手動或自動控制進行改變。 此裝置是加德納發動機的一個特征，總是和加速器控制連接在一起。 在一些發動機的制造中，并不使用螺旋式花鍵套管，通過搖桿或斜面型的偏心操縱裝置，曲軸相位角起到同樣作用. 一些制造商放棄裝配可變正時裝置，而采用固定正時。但是，最近，裝配一個簡單可變正時器的分配器型的燃油泵廣泛采用，使這精致的附件獲得更普遍的使用。 From the above it will be realised that fundamental difference between petrol and diesel engines is that in the petrol engine the source of heat for igniting the charge, namely an electric spark, is generated outside the engine, and is taken, as it were, into the waiting charge at the required instant. In the diesel engine the source of heat for igniting the charge is created within the engine by compressing pure air to a degree that will initiate combustion and then injecting the fuel at the right time in relation to the movement of the crankshaft. It will have been gathered that apart from their auxiliary features, both classes of engine are of very similar construction. But as the diesel is called upon to withstand very much greater stresses due to higher pressures in the cylinders, it has to be of more substantial construction and is thus heavier.翻譯：通過以上描述，人們認識到汽油機和柴油機之間的基本差別是汽油機里，點燃混合氣體的（也就是一個電火花塞）熱源產生于發動機外面，在要求的瞬間，熱源被吸進等待的混合氣體里。 在柴油機里，點燃燃料熱源產生于發動機內部，把純凈的空氣壓縮到開始燃燒的程度，然后，在曲軸運動相連的準確時刻噴射燃油。 從收集的資料看，除了輔助的特點外，兩種的發動機結構非常相似。 但是。由于壓力更高，柴油機的汽缸里要求經受大得多的應力，所以，柴油機必須（擁有）更堅固的結構，因而，會增加起其重量。（其重量更重） By careful design and by taking full advantage of the most advanced metallurgical technique the power/weight ratio of the automotive diesel was substantially improved within the course of a very few years so that the weights of present-day engines do not appear to be capable of much further reduction翻譯：通過認真設計和完全利用最先進的冶金技術的優點，汽車柴油機的功率/重量比在最近幾年里有本質的改進，以致，現在發動機的重量似乎已經降到最低程度（似乎不能再減少）。 Lesson 2. The Four-stroke Cycle 四沖程循環Anyone familiar with the working of the ordinary petrol engine is aware that the motive power is produced by igniting above the piston in each cylinder a mixture of petrol vapour and air, the resultant combustion of which causes an expansion of gases exerting pressure on the top of the piston.By this means the heat released by the fuel is transformed into work, the reciprocating movement of the pistons being converted into rotary movement of a crankshaft by means of the connecting rods翻譯：熟悉普通汽油發動機原理的人知道，通過點燃每個汽缸里活塞上面汽油蒸氣和空氣混合氣體，混合氣體燃燒的結果使氣體膨脹，給活塞頂部施加壓力而產生動力。通過這種方式，燃料釋放的熱量被轉換成功。活塞的往復運動通過連桿被轉換成曲軸的旋轉運動。The four-stroke cycle is the operating sequence more commonly employed.It requires that each cylinder be provided with an inlet valve to admit a combustible mixture of petrol and air drawn by the suction of the engine from a mixing device known as the carburettor into the space above the piston, while there must also be an exhaust valve to control the outlet through which the residual products of combustion are ejected after they have done their work.四沖程循環是被普遍采用的工作順序。四沖程循環要求裝配一個進氣閥，允許把發動機從混合裝置也就是化油器上吸入的可燃的汽油和空氣混合氣體進入活塞上面的空間，同時，也必須有一個排氣閥，控制排出氣體，把燃燒的殘余物質在做完功后噴射出去。To describe the complete cycle as it occurs in any one cylinder it may be assumed that the piston is at the top of the stroke and that both the inlet and the exhaust valves are closed.As the piston descends the inlet opens so that charge of mixture can flow into the cylinder. This is called the suction(or induction)stroke, the charge flowing under the influence of external atmospheric pressure.Immediately after the piston has reached its lowest position and begins to rise again the inlet valve is closed so that the mixture can be compressed by the rising of the piston on the compression stroke As the piston once again approaches its topmost position an electric spark is caused to pass between the points of a sparking plug located in the top of the cylinder in a zone called the combustion chamber.The spark ignites the mixture and as both valves are closed during its combustion, there is a considerable pressure rise.As a result, the piston is forced back again down the cylinder, this movement being termed the expansion or power stroke翻譯：為了描述在任何一個汽缸里發生的完整的工作循環，可以假設活塞處于沖程的頂部，進氣閥和排氣閥關閉。隨著活塞下降，進氣閥打開，以便混合氣體燃料能流進汽缸。這過程被稱為進氣沖程（或感應沖程），燃料受外部大氣壓力的影響流動。在活塞已經到達最地位置后，活塞立即再次上升，進氣閥關閉，以便混合氣體被上升的活塞壓縮，稱為壓縮沖程。隨著活塞上升到接近最高位置，一個電火花被打著，從火花塞的頂尖穿過，火花塞位于被稱為燃燒室的區域的汽缸的頂部。火花點燃混合氣體，隨著兩個氣閥在燃燒時關閉，有巨大的壓力上升。結果，活塞再次被壓回汽缸，此運動被稱為膨脹沖程或動力沖程。Before the piston reaches its lowest point, the exhaust valve is opened, pressure is released, and as the piston again rises it sweeps the residual gas through the exhaust outlet, whence it is led through a silencer to the atmosphere; this is the exhaust stroke which completes the continuously repeated cycle.Thus it will be seen that there is one power stroke for every four strokes of the piston or two revolutions of the crankshaft在活塞達到最低點時，排氣閥打開，壓力釋放，隨著活塞再次上升，活塞把殘余氣體壓向排氣出口，這里，排出氣體經過一個消聲器被導進大氣；這是排氣沖程，完成不斷連續重復的循環。因而，可以看出活塞的每4個沖程或曲軸的兩轉有一個動力沖程。It should be noted that the size of the combustion chamber above the piston (known as the clearance space )is considerably smaller than that part of the cylinder in which the piston travels.Thus at the end of the compression stroke the explosive mixture is compressed to a pressure varying from about 5. 5 to 7kg/cm2(80 to 100 lbf/in2).By such compression the mixture is heated to some extent, resulting in better vaporisation of the fuel, and more intimate mixing of the vapor and air; it also enables the engine to work with higher thermal efficiency, to which further reference is made later.應該注意活塞上面燃燒室的大小（被人稱為間隙空間）比汽缸里活塞行程的那部分相對要小一些。因而，在壓縮沖程結束時，混合可燃氣體被壓縮到大約5.5-7 kg/cm2 (80 - 100 lbf/in2)的壓力。通過這種壓縮，混合氣體被加熱到一定程度，使燃料汽化更好，并使空氣和燃料汽的混合更精細，這也使發動機以更高的熱效率做功，后面文章會對熱效率作進一步的解釋。Incidentally, the ratio of the total volume of the cylinder above the piston when it is in its lowest position to that of the combustion or clearance space when it is at its highest position is known as the compression ratio and in modern commercial vehicle petrol engines varies from about 6:1 to 8:1順便提一下，活塞最低位置時汽缸的總容量和活塞最高位置汽缸燃燒時的容量或間隙空間的比率被稱為壓縮比。現代商用車的汽油發動機的壓縮比范圍從大約6:1到8:1。The operating cycle of the four-stroke diesel is identical in so far as the sequence of strokes is concerned but there is a major difference in principle.On the induction stroke only pure air is drawn into the cylinder through the inlet valve port.Then, because the clearance space is so much smaller than that in a corresponding petrol engine, the compression ratio is considerably higher, being not less than 12:1 and even in some engines as high as 21:1.The final pressure of the air charge at the end of the compression stroke may be 35kgf/cm2(500 1bf/in2)or more, with a corresponding temperature rise to not less than 1000F(538), which is sufficient to ignite finely atomized but non-volatile fuel oil without the assistance of an electric spark.4沖程柴油機的工作循環就沖程順序而言是相同的。但是原理上有一個重要的差別。在感應沖程，只有純凈的空氣通過進氣閥口吸進汽缸。那么，因為間隙空間比相應的汽油發動機的要小的多，其壓縮比相當高，不低于12:1，甚至有些發動機達到21:1。壓縮沖程結束時沖氣的最終壓力可能為35kgf/cm2(500 1bf/in2)或更高，隨著相應的溫度上升到至少1000F(538)，足以點燃精細霧化的但尚未揮發的燃油，無須電子火花塞的輔助。Just before the piston reaches the end of the compression stroke the fuel oil is injected into the combustion chamber through an injection nozzle, or sprayer, mounted on the cylinder head in much the same position as the sparking plug in a petrol engine.The pressure at which the fuel is injected must necessarily, of course, be higher than the combustion pressure , usually not less than 140 kgf/cm2(2000 1bf/in2).During injection the fuel is split up into finely divided particles, and the mixture of these with the air forms an explosive charge that is ignited by the heat of compression.在活塞到達壓縮沖程結束前，燃油通過一個噴射噴嘴或噴霧器被噴射入燃燒室，噴嘴或噴霧器安裝在缸蓋上，和汽油發動機上火花塞的位置完全相同。燃油噴射的壓力當然且必須比燃燒壓力高，通常至少達到140 公斤力/平方厘米kgf/cm2 (2000 磅力/平方英寸 1bf/in2)噴射時，燃油被碎成微小顆粒，這些顆粒和空氣的混合體形成爆炸（可燃）氣體，被壓縮的熱量點燃。Injection is continued for a short period, during which the piston passes its highest position and begins to descend on the power stroke.The expansion of combustion products only begins to have effect when the piston has passed the top of its stroke, and during the injection period the burning fuel maintains a more or less constant pressure somewhat above that of compression; When the fuel is cut off expansion of the gases continues, the pressure is falling as the piston descends.The overall effect on the piston is a more sustained pressure than that associated with the combustion process in a petrol engine.The effective part of the power stroke is concluded before the piston descends to its lowest point, and the cycle is completed when the exhausted gases are expelled by the rising piston.噴射持續很短的時間，此時活塞經過最高位置，開始下降到動力沖程。當活塞已經通過壓縮沖程的頂部時，燃燒物的膨脹才開始起作用，噴射期間，燃燒的燃油保持較穩定的壓力，稍微高于壓縮壓力；當燃油被切斷，氣體繼續膨脹，壓力隨活塞的下降而下降。對活塞的總的作用是與汽油發動機里和燃燒過程相關的壓力相比具有一個更穩定的壓力動力沖程的有效部分在活塞下降到最低點前結束，當廢氣被上升的活塞排出時，循環完成。To inject the fuel a special type of pump driven by the engine is employed, and this is a distinguishing feature of the diesel engine, just as the carburettor and the magneto or coil and distributor ignition apparatus distinguish the normal petrol engine.燃油的噴射靠使用一個由發動機帶動的專用型式的泵來實現的。這是柴油發動機一個明顯的特征。而化油器、磁發電機或線圈和分配器點燃裝置顯示出正常的汽油發動機的特點Lesson 3. Horsepower 馬力AN engine produces power only when a load is applied.When the engine first starts, the load applied is in the form of its own friction and compression.The resistance offered by various accessories also affects this initial load .an engine must drive a fan, generator, injection pump, water pump, perhaps a compressor too.All of these add to the load on an engine before you apply that toad at the output shaftWeve said that an engine produces power when a load is applied.What, exactly, is power? Power is the capacity of an engine to do work.WOEK is defined as moving an applied force through distance.POWER is work with the element of time added or how long it took to do the work.HORSEPOWER is the measure of power.One horsepower is a measurement of the force required to lift 33, 000 lbs a distance of one foot in one minute.只有給發動機增加負載時，發動機才發出功率。發動機第一次啟動時，增加的負載是自我摩擦和壓縮。各種附件施加的阻力也影響這初始的負載.發動機必須帶動風扇，發電機，噴射泵，水泵，或許也帶動一臺壓縮機。在你把負載加到輸出軸上之前，所有這些阻力都加在發動機的負載上。我們曾說只有給發動機增加負載時，發動機才發出功率。準確的說，什么是功率？功率是一臺發動機做功的能力。做功被定義為把一個作用力移動一定的距離。功率是單位時間內所做的功或花多長時間的做功。馬力是功率的單位。一馬力等于在一分鐘時間內提起33, 000磅的重量通過一英尺的距離所要求的力的大小。提起33, 000磅的重量在一分鐘時間內通過一英尺的距離時功率的計量單位Horsepower shows up in engine rating specs under several names .It may be listed on these specs as maximum, intermittent, continuous or gross horsepower.How do these terms differ.馬力在發動機標定值規格表中有不同的名稱。在標定值規格表中可能列為最大馬力，間隙馬力，連續馬力或總馬力這些術語有什么不同呢？Gross horsepower is a measure of the power units , produced by a bare engine, with no power drain caused by accessories.Manufacturers often use this measure to establish a base line when setting up engine ratings because this method eliminates the variables imposed by different accessories, which may or may not be used on that particular engine in actual service.總馬力是一臺沒有附件功率消耗的裸機的功率單位，制造商在設定發動機額定功率時經常使用此單位確定基準線。本方法可以消除不同附件產生的影響，在某一特定發動機的實際運用中，這些附件可能使用，可能不使用。Net or flywheel horsepower represents the power units produced by a fully-equipped engine at the output shaft or flywheel.凈功率或飛輪馬力是功率單位，表示一臺完全裝配的發動機在輸出軸或飛輪軸上輸出的功率Brake horsepower is another term you may come across while puzzling over an engine rating chart.This simply means the power, available at the output shaft for doing work and is the same as net horsepower .The term is a hold-over from the days when the brake horsepower was actually measured on a form of a brake device called a Prony brake.Today a dynamometer is the instrument most often used and now you know why some people still can a dynamometer a brakePerformance curves can be confusing.Knowing what each curve represents can do much to eliminate this confusionMaximum brake horsepower curve is the curve showing the highest horsepower that an engine will develop at any rpm within its range.Normally this curve is used for engines which must produce peak power for short periods of time or for special applications.制動馬力是你在研究發動機額定功率值圖表時會碰到的另一個專業術語。簡單的說，它就是做功時輸出軸能提供的功率，而且等同于凈功率。此術語是從過去沿用下來的，當時制動馬力在實際運用中用一個被稱作普龍尼制動閘的制動裝置進行測量。今天，測功機是最常用的設備，現在你知道為什么一些人仍然把測功機稱為制動閘（剎車）。性能曲線使人困惑。如果知道每條曲線代表的意思會非常有助于消除這種困惑。最大制動馬力曲線（極限外特性曲線）是表示一臺發動機在允許的每分鐘轉速范圍內發出的最高馬力曲線。正常情況下，此曲線用于發動機在短時間內或特殊用途中必須發出最高功率Intermittent brake horsepower curve is normally about 90% of the maximum and is the horsepower curve recommended or satisfactory operations under certain conditions of load and speed， usually variable load and speed conditions where top load and speed are only needed for short periods.“Intermittent” curves are the ones most often used for vehicular applications.間隙制動馬力曲線（瞬時外特性曲線）通常大約是最大馬力的90%，是在某負荷和速度條件下進行良好運行而推薦的馬力曲線，通常此條件是變化的負荷和速度條件，最大負荷和最高速度只在很短的時間內需要，間隙曲線是汽車運用中最常用的曲線。Continuous brake horsepower curves are about 80% of maximum and are the curves recommended for satisfactory continuous operation.A generator set is an example of an application in which the continuous brake horsepower curve might be usedDrawbar horsepower is a term commonly found in tractor engine ratings and is a measurement of the power developed at the tractors drawbar, Drawbar horsepower is found by measuring the horizontal drawbar pull and the exact tractor traveling speed持續制動馬力曲線大約是最大馬力的80%，是進行持續良好的運行而推薦的曲線，發電機組是使用持續制動馬力曲線的一個實例。牽引馬力是一個拖拉機發動機額定功率值里都能找到的一個專業術語，是拖拉機牽引所發出的的功率的功率單位。牽引馬力是通過測量水平牽引力和拖拉機實際行駛速度所求的。A unit of power in the U.S. Customary System, equal to 745.7 watts or 33,000 foot-pounds per minute.馬力美國習慣體系中的功率單位，相當于745.7瓦特或33,000英尺-磅分The power exerted by a horse in pulling.一匹馬在拉東西時使用的力量4.Torque and Fuel Consumption 力矩和燃油消耗The moment of a force;the measure of a forces tendency to produce torsion and rotation about an axis, equal to the vector product of the radius vector from the axis of rotation to the point of application of the force.轉矩，力矩一種測量產生扭轉和繞軸旋轉趨勢的力的單位，等于從旋轉軸到力作用點的旋轉矢量Weve already said that horsepower is a measure of an engines ability to produce power.Theres another term you should understand which influences an engines ability.Independent of horsepower, to do a specific job.This is torque.我們曾說馬力是一臺發動機產生動力的能力的測量單位。你應該了解另一個影響發動機做具體工作的能力、與馬力無關的專業術語。這就是力矩。Torque. When a force is applied at right angles to a radius of a wheel or to the end of a lever, it creates a twisting force called torque.Torque is measured in pound/in. or pound-ft.力矩. 當一個作用力與輪子的半徑或與杠桿的一端成直角時，他產生一個旋轉力，被稱為力矩。力矩用磅/英寸或