外文翻譯--一些中速柴油發(fā)動機研究的實驗經(jīng)驗

1、<p><b>　　中文4730字</b></p><p><b>　　譯 文</b></p><p>　　學 院： 機電與汽車學院 </p><p>　　專 業(yè)： 熱能與動力工程 </p><p>　　學 號：

2、 </p><p>　　姓 名： </p><p>　　指導教師： </p><p>　　2014年 5月 5日</p><p>　　一些中速柴油發(fā)動機研究的實驗經(jīng)驗</p><p>　　文摘: 這篇

3、文章的目的是探究一種中速發(fā)動機的一些實驗結(jié)果。這里事實上是進行了單缸共軌柴油機的研究, 這是研究的方向。其主要特征是氣體交換閥門調(diào)節(jié)時間系統(tǒng)是完全可調(diào)的電液系統(tǒng),利用發(fā)動機潤滑油在250帕時打開氣體交換閥門。此外這個引擎沒有渦輪增壓器, 但是一個單獨的空氣壓縮機供應系統(tǒng)可以改變進氣管空氣的狀況; 在引擎后部、有一個蝶狀的改變排氣背壓的管子。燃油系統(tǒng)是一種常見的軌道類型：軌道的壓力、 噴射時刻、噴射時間是開始完全可調(diào)。這些研究進行了所有的

4、EVE發(fā)動機可能性狀況研究: 不同的負載、管道壓力,開始噴射時刻和邊界條件都是可調(diào)的。此外，該實驗對氣體交換閥門的液壓系統(tǒng)的不同時間響應性能進行了檢測、評價。</p><p><b>　　介紹</b></p><p>　　由于相關(guān)部門日益嚴格的限制，高油價和減少排放控制帶來的挑戰(zhàn)成為內(nèi)燃機的發(fā)展必須面對的越來越富有挑戰(zhàn)性的課題。在這些方面，如何研究使得在配置最優(yōu)化基礎

5、上得到的完美結(jié)果成為了一種大挑戰(zhàn)。</p><p>　　極限引擎是一個四沖程單缸大孔徑中速研究的發(fā)動機，這種柴油機與Wärtsilä W20氣缸尺寸相似，它是由芬蘭的阿爾托大學的國際內(nèi)燃機研究小組設計的。引擎框架、曲軸和主要軸承能承受缸內(nèi)最大壓力為400 帕[1]。EVE有電液閥執(zhí)行機構(gòu)(EHVA) [2] 代替?zhèn)鹘y(tǒng)的凸輪軸機制，該系統(tǒng)允許改變高氣體交換的彈性閥參數(shù)。事實上，它可能改變開啟和關(guān)

6、閉時間的氣體交換閥，以及改變其最大氣門升程以及它們的開啟和關(guān)閉提升斜率。閥門執(zhí)行機構(gòu)受作用于潤滑系統(tǒng)的加壓油(250 bar)的控制.EVE連接有一個電動馬達，這樣可以運行在機動模式。燃油噴射系統(tǒng)是可調(diào)的共軌式軌道的壓力, 以及噴射時間和持續(xù)時間。根據(jù)邊界條件, 如進氣壓力、溫度以及排氣壓力，發(fā)動機可以被一個空氣供給體制和一個反饋壓力節(jié)流閥所控制，這樣就允許運行的渦輪增壓器具有無限配置的狀況下運行。迄今為止,除了提到的部件的數(shù)量外，同時

7、所有的壓力和溫度的輔助系統(tǒng)(LT水、HT水和潤滑油)都是遠程調(diào)節(jié)的。所有這些特點使本發(fā)動機的研究成為出色的研究平臺。</p><p>　　本文的研究重點是對EVE提出一些可以利用的可行性，不同的氣體交換配氣相位，噴霧參數(shù)和邊界條件都被測試。用先前的測試運行, 在那里分析比較已經(jīng)生產(chǎn)出的相應商業(yè)引擎,記錄下相應的負荷變化。</p><p>　　首要工作描述的是米勒的一個應用技術(shù)。米勒循環(huán)[3

8、]可以用來降低NOx: 它是通過適時改變閥門定時減少發(fā)動機的壓縮比的。</p><p>　　這可以通過在比較早的進氣行程的時候關(guān)閉進氣門 (EIVC)來實現(xiàn),可以通過在壓縮行程關(guān)閉進氣閥很晚(LIVC),也可以通過在進氣結(jié)束后的壓縮行程開啟簡要的排氣閥實現(xiàn)。本文使用第一種方法:事實上引用Ivc的氣門定時時非常接近上止點時刻, 關(guān)閉閥門等40多個CAD BBDC是很先進的。米勒技術(shù)首先被用在EVE上。根據(jù)以前的經(jīng)驗

9、(見例如[4 ~ 7),</p><p>　　一項新的策略在這里將展開討論。這些保持在氣缸的氣團時間與氣門的保持時間是一致的。質(zhì)量不能被測量，但是卻能得到一維模擬模型，在這項工作中用三種不同載荷進行試驗。</p><p>　　表1 EVE 規(guī)格</p><p>　　缸徑200mm 行程 280mm 連桿 610mm 排量8796 cc</p&g

10、t;<p>　　發(fā)動機轉(zhuǎn)速900r/min 理論壓縮比15.0 噴油器提示(米勒測試)8孔x 0.34毫米 噴油器提示(噴射試驗)×0.30毫米9洞 所用燃料LFO (43 MJ /公斤)</p><p><b>　　研究1:米勒測試</b></p><p>　　這些測試的主要目的是測試使發(fā)動機在不同的負荷下的閥門作用時間導

11、致的NOx很大的降低量。在實驗裝置中,具有流體模擬功能的發(fā)動機仿真已經(jīng)制作出來了，需要通過找到這些邊界條件來進行仿真。沿比較以前的W20也被制作出來了,作用 100%, 75% 和 50% 負載進行試驗。針對每種情況密封的空氣質(zhì)量也一直不斷沿著參考的時刻而變化。同時油耗一直不斷, 因為引擎額定功率視為平均有效值，并且油量在每一個測試中都是不變的。此外，充氣溫度和模擬渦輪增壓器的效率沒有改變。</p><p>&l

12、t;b>　　氣門定時</b></p><p>　　實驗對不同的一些氣門作用時刻進行了測試,以便驗證EHVA運行情況。除了IVC外所有的參數(shù)都保持不變。由于EHVA[2]的基礎上的液壓技術(shù)，正在作用的IVC升程的幅度的平滑誤差小于1mm. 雖然不同的進氣定時被設置，但事實上,在這兩個米勒測試周期內(nèi)其結(jié)果看起來幾乎相同, 因為這個原因, 進氣門的關(guān)閉可進行計算機模擬，而當升程是1毫米是,就叫做IVC

13、1。當提升進氣閥關(guān)閉后,被系統(tǒng)獲得的最大升程就減小了。因此, 對測試時間(視為IVC1)沒有比BBDC 42計算機輔助設計(CAD) 更先進的了。圖1給出了來自這三個時間的研究:</p><p>　　1。參考時間，有5 CAD BBDC的IVC1 和最大值為17.1的進氣升程;</p><p>　　2、高級計時，有35 CAD BBDC的IVC1 和最大值為16.5的進氣升程</p&

14、gt;<p>　　3。最先進的米勒計時,IVC1 42 CAD BBDC和最大進氣閥抬的15.8毫米。</p><p>　　排氣時間和IVO在每個運行頂點是恒定的；最大的排氣氣門升程為17.1毫米。排氣關(guān)閉和打開斜度是不變的：這是因為在EVE中，出于安全的原因，在每一個曲軸轉(zhuǎn)角中氣門和活塞距離保持大于或等于4毫米。</p><p>　　圖1——米勒測試：測試的氣門定時<

15、/p><p><b>　　仿真模型</b></p><p>　　仿真采用發(fā)動機仿真進行，一維的流體動力的程序用于預測發(fā)動機的性能。由于EVE系統(tǒng)沒有渦輪增壓器, 發(fā)動機仿真模型的一個基本用處就是找出發(fā)動機裝置使EVE邊界條件可以相當類似于一個真正的發(fā)動機。對渦輪增壓器的數(shù)學模型進行了模擬,分別模擬渦輪和壓縮機。該模型是需要找到充入的空氣壓力、排氣壓力;此外,負責設定空氣溫

16、度在每個試驗中是相同的。而用于計算壓縮機和渦輪動力吸入的大氣和廢氣壓力的方程式如下 [8]:</p><p>　　壓縮功率（KW） 壓縮效率 進氣流量 （kg/s）</p><p>　　進氣比熱[kJ /公斤K] 環(huán)境溫度[K] 空氣壓縮比</p><p>　　空氣比熱 汽輪功率[kW) 渦輪效率</p><

17、;p>　　尾氣流[公斤/ s]. 廢氣比熱[kJ /公斤K] </p><p>　　廢氣溫度[K] 尾氣膨脹率 廢氣比熱</p><p>　　這臺機器效率總TC效率為0.65。該值是根據(jù)以前的測試數(shù)據(jù)計算出的，在這項工作中，這是在每一個普通負載理想的平均估計效率。此外，另一個在計算模型的假設是:</p><p>　　?環(huán)境條件: 298 K

18、, 是1.005 kJ /kgk、是1.4。</p><p>　　?上游壓縮機壓力和下游渦輪壓力1bar;因此，和也是測試值空氣壓力、廢氣的排氣壓力,用帕作單位。</p><p>　　?壓縮機模型裝置設在進氣管的面前，而渦輪模型在汽車排氣管道靠近調(diào)節(jié)閥門處。當閥門定時改變時，控制裝置可以在發(fā)動機運作中得到相應流量運作情況。</p><p><b>　　特別

19、是:</b></p><p>　　o因為同樣數(shù)量的燃料注入，SOI被調(diào)整以便適應同樣的發(fā)動機功率匹配；</p><p>　　o進氣壓力也被調(diào)整，以便達到相同的收集到的氣體質(zhì)量；</p><p>　　o 根據(jù)施加的效率改變排氣壓力以平衡模擬TC；</p><p>　　模擬的結(jié)果繪出了如下面的圖所示。特別的,進氣管空氣壓力、泵氣損失和

20、噴射也被記錄了。</p><p>　　為了保持相同的空氣質(zhì)量在氣缸蓋內(nèi), 當進氣時間減少時充氣氣壓需要增加,也就是說IVC是先進的。在圖2中可以看出, 在高負載時他的數(shù)值超過了來自相關(guān)情況下的1.5帕。</p><p>　　圖2——米勒模擬結(jié)果：進氣壓力 圖3——米勒模擬結(jié)果：泵送平均有效壓力</p><p>　　圖四——米勒模擬結(jié)果：噴射時刻 圖5—米勒模擬

21、結(jié)果：指示的氮氧化物值</p><p><b>　　試驗結(jié)果</b></p><p>　　測量試驗進行了快速和慢速兩個試驗。下面的圖表有關(guān)工作的主要成果進行了說明。由于EVE具有比多缸發(fā)動機較高的機械損失[9], 結(jié)果也表明出來了這一點。在每一個測試負荷下NOx目標值均降低 了(圖5)。最好的結(jié)果來自部分荷載：事實上,50%的減少量是3.5克/千瓦時的ISNOx, 這

22、意味著40%的相應值，這是通過標準時間獲得的(圖6)。這些大幅降低實現(xiàn)是由于利用了早期的IVC(米勒技術(shù))和以后SOI技術(shù)。在之前的EVE運行測試中相比組合使用的相同時間米勒技術(shù)。</p><p>　　唯一可能延遲的是SOI會指示氮氧化物的減少相比較使用組合米勒技術(shù)在相同的時間內(nèi)，這僅僅使用的低速SOI能有效減少NOx 的產(chǎn)生。另一方面，實現(xiàn)同樣的功率輸出需要更多的燃料——即要求長時間噴射燃油。這樣導致的一個后果

23、是非常高的廢氣溫度以及可能導致的不穩(wěn)定燃燒。這些效果對整體經(jīng)濟的發(fā)動機而言太消極了，因此，其他方式——例如使用米勒循環(huán)——都必須經(jīng)過研究,就是為了讓它達到在實際應用的結(jié)果中可以接受。</p><p>　　Some Experimental Experience Gained With a Medium-Speed Diesel Research Engine</p><p>　　Abstr

24、act: The objective of this paper is to show some experimental results gained from a medium-speed research engine. The study is in fact carried out with a single-cylinder common rail diesel engine (EVE), which is used onl

25、y for research purposes. Its main feature is that the gas exchange valve timing is completely adjustable with an electro-hydraulic system that uses the engine lubrication oil at 250 bars to open the gas exchange valves.

26、In addition the engine does not have a turbocharger, bu</p><p>　　Two studies are described in this paper. The first is an application of the Miller technique, advancing the closure of the intake valve. The p

27、urpose of this work is a massive reduction of the NOx emission with no penalties in fuel consumption. The setup of the loads with Miller cycle is found with the help of a simulation model. The results show that high NOx

28、reduction is achievable with the used strategy at every run load but the greatest decrease occurs at partial load. The major drawback is t</p><p>　　INTRODUCTION</p><p>　　The development of the i

29、nternal combustion engines has to face more and more the challenging issues of lowering the fuel consumption because of high oil price and of emissions reduction, due to the increasingly stricter limits imposed by the r

30、egulating authorities. In these respects the possibility to optimize the engine operating parameters in order to find the most performing configurations is a big advantage.</p><p>　　The Extreme Value Engine

31、(EVE) is a four-stroke single-cylinder large bore medium-speed research engine. The engine has similar cylinder dimensions with Wärtsilä W20 engine and it is designed by the Internal Combustion Engine Research

32、Group of Aalto University in Finland. The engine frame, the crankshaft and the main bearings can withstand incylinder maximum pressure of 400 bar [1]. The EVE has electro-hydraulic valve actuators (EHVA) [2] instead of t

33、raditional camshaft mechanism. This system pe</p><p>　　The studies in this paper are focused to present some of the possibilities that can be exploited with EVE. Different gas exchange valve timing, injectio

34、n parameters and boundary conditions are tested.Using previous test runs, where the comparison with its corresponding commercial engine has been carried out, the reference loads are drafted out.</p><p>　　The

35、 first work described is an application of the Miller technique. The Miller cycle [3] is used to reduce NOx: it consists in a reduction of the effective engine compression ratio by opportunely changing the valve timing.

36、This can be achieved by closing the intake valve very early in the intake stroke (EIVC), by closing the intake valve very late in the compression stroke (LIVC), by opening briefly the exhaust valve after the intake closu

37、re in the compression stroke. In this paper the first met</p><p>　　Table 1 􀅆 EVE specifications</p><p>　　Cylinder Bore 200 mm Stroke 280 mm Connecting Rod 610 mm Swept Volume 8

38、796 cc </p><p>　　Engine Speed 900 rpm Nominal Compression Ratio 15.0 Injector tip (Miller test) 8 holes x 0.34 mm</p><p>　　Injector tip (Injection test) 9 holes x 0.30 mm

39、 Fuel used LFO (43 MJ/kg)</p><p>　　STUDY I: THE MILLER TESTS</p><p>　　The main purpose of these tests is a massive reduction of NOx using different valve timings at different en

40、gine loads. Before the experimental tests, the 1-D simulations with the fluid-dynamic code GT-Power have been carried out. These are needed to find the boundary conditions to be used in the runs.</p><p>　　Al

41、ong the comparison with W20 previously carried out, 100%, 75% and 50% load have been run. For each case the trapped air mass has been kept constant along the reference timing. Also the fuel consumption has been constant

42、because the engine power – considered as IMEP - and the fuel quantity are the same for every case. In addition, the charge air temperature and the efficiency of the simulated turbocharger have not been changed.</p>

43、<p>　　The Valve Timing</p><p>　　Several valve timings have been tested to validate the operation of EHVA. All the parameters are kept constant except the IVC. Due to the hydraulics of the EHVA [2], ad

44、vancing the IVC the slope of the lift becomes very flat at lifts lower than 1 mm. In fact in the two tested Miller cycles the IVC looks to be almost the same, although different intake timing is set. For this reason, the

45、 intake valve closing is considered as the CAD when the lift is 1 mm and it is called IVC1. When advancing the c</p><p>　　1. the reference timing, with IVC1 of 5 CAD</p><p>　　BBDC and maximum in

46、take valve lift of 17.1 mm;</p><p>　　2. an advanced timing, with IVC1 of 35 CAD BBDC and maximum intake valve lift of 16.5 mm;</p><p>　　3. the most advanced Miller timing, with IVC1 of 42 CAD B

47、BDC and maximum intake valve lift of 15.8 mm.</p><p>　　The exhaust timings and the IVO are constant for every run point; the maximum exhaust valve lift is 17.1 mm. The exhaust closing and the intake opening

48、slope are not constant: this is because in EVE, for safety reasons, the distance between the gas exchange valves and the piston is kept greater or equal to 4 mm at every crank angle.</p><p>　　The Simulation

49、Model</p><p>　　The simulations are carried out with GT-Power, a one-dimensional fluid-dynamic program used for predicting engine performance. Since the EVE system has not any turbocharger, the GT-Power simul

50、ation model is a fundamental tool to find out the engine set-up so that the EVE boundary conditions can be quite similar to a real engine’s. The turbocharger is simulated with a mathematical model that treats separately

51、the action of the compressor and of the turbine. This model is needed to find the charge</p><p>　　The machine efficiencies are so that the total TC efficiency is 0.65. This value is calculated from data of t

52、he previous tests and it is an average estimation of the efficiency at every load considered in this work. Furthermore, the other assumptions in the calculation model are:</p><p>　　?The ambient conditions:

53、is 298 K, , is 1.005 kJ/kg K, is 1.4.</p><p>　　?The upstream compressor pressure and the downstream turbine pressure are 1 bar;thereforeand represent also the values of the charge air pressure and of the ex

54、haust backpressure, expressed in bar.</p><p>　　? The compressor model is set before the intake pipe and the turbine’s model after the exhaust pipe nearby the regulating valve. The controls permit to find the

55、 engine set-up to use in the test runs when the valve timing is modified. In particular:</p><p>　　o the SOI is adjusted to match the same engine power, since the same amount of fuel is injected;</p>&

56、lt;p>　　o the charge air pressure is adjusted to achieve the same air trapped mass;</p><p>　　o the exhaust pressure is changed to balance the simulated TC along the imposed efficiency.</p><p>

57、　　The results of the simulations are plotted below. In particular, the intake charge air pressure, the pumping losses and the start of injection are reported.</p><p>　　To maintain the same air mass trapped i

58、n the cylinder, the charge air pressure needs to be increased when the intake duration is reduced, i.e. IVC is advanced. In figure 2 it can be seen that at high load its value is raised more than 1.5 bar from the referen

59、ce case.</p><p>　　The Test Results</p><p>　　Both fast and slow measurements have been taken during the tests. Here below the charts concerning the main outcomes of the work are illustrated. Sinc

60、e the EVE has higher mechanical losses than a multi-cylinder engine [9], the results are here referred to the indicated power. The aimed NOx reduction is achieved at every tested load (figure 5). The best results come fr