無(wú)論何時(shí)，新款發(fā)動(dòng)機(jī)的問(wèn)世一定是大新聞，而采用新的設(shè)計(jì)流程的新發(fā)動(dòng)機(jī)誕生，則更是重大新聞。美國(guó)萬(wàn)國(guó)卡車(chē)公司（International Truck）最近公布了旗下主要適用于重型8級(jí)卡車(chē)應(yīng)用的全新發(fā)動(dòng)機(jī)設(shè)計(jì)International A26。此外，萬(wàn)國(guó)卡車(chē)還同時(shí)介紹了公司的α發(fā)動(dòng)機(jī)研發(fā)項(xiàng)目。該項(xiàng)目召集了一小批精英人馬，專(zhuān)門(mén)致力于為發(fā)動(dòng)機(jī)研發(fā)提供新的方向。
萬(wàn)國(guó)卡車(chē)公司的先進(jìn)工程研發(fā)副總裁Darren Gosbee表示，“A26經(jīng)過(guò)全新設(shè)計(jì)，可以提供行業(yè)最領(lǐng)先的正常運(yùn)行時(shí)間、耐用性和可靠性。”具體來(lái)說(shuō)，這款12.4L的A26重型卡車(chē)發(fā)動(dòng)機(jī)采用了一款來(lái)自公司合作伙伴大眾汽車(chē)（Volkswagen Group）的MAN D26直列6缸曲軸箱，并圍繞D26采用了大量創(chuàng)新組件設(shè)計(jì)，可以?xún)?yōu)化A26的四項(xiàng)關(guān)鍵指標(biāo)：正常運(yùn)行時(shí)間、燃油效率、重量和NVH性能（噪音、振動(dòng)和不平順性）。
A26發(fā)動(dòng)機(jī)的重量?jī)H為2,299磅（1,043公斤），比納威司達(dá)（Navistar）的N13發(fā)動(dòng)機(jī)輕55磅（25公斤）；比傳統(tǒng)的15L大缸徑發(fā)動(dòng)機(jī)輕600到700磅（272到318公斤）。盡管重量有所減輕，但A26仍然可以輸出最高475 hp（354kW）的功率和1,750 lb·ft（2,373 N·m）的扭矩。
為了提供最長(zhǎng)的正常運(yùn)行時(shí)間，“簡(jiǎn)潔”一直是萬(wàn)國(guó)卡車(chē)公司的設(shè)計(jì)關(guān)注點(diǎn)之一。Gosbee表示，“A26可以說(shuō)是現(xiàn)代發(fā)動(dòng)機(jī)的極簡(jiǎn)設(shè)計(jì)代表，從設(shè)計(jì)、校準(zhǔn)到測(cè)試，我們?cè)谘邪l(fā)的每一個(gè)環(huán)節(jié)都時(shí)刻謹(jǐn)記要為客戶(hù)提供最長(zhǎng)的正常運(yùn)行時(shí)間。”此外，公司還采用了更大的活塞銷(xiāo)、連桿和襯套，從而實(shí)現(xiàn)更好的負(fù)載分配；更小的活塞冷卻噴流系統(tǒng)，可以提高油壓并將換油服務(wù)周期延長(zhǎng)至70,000英里（112,654公里）。
此外，A26的一些其他優(yōu)化也為這款發(fā)動(dòng)機(jī)帶來(lái)了5%的燃料經(jīng)濟(jì)性提升，包括博格華納（BorgWarner）的全新單級(jí)可變幾何形狀渦輪增壓器搭配一款簡(jiǎn)化空氣管理系統(tǒng)；博世（Bosch）的2,500-bar（36,259- psi）高壓共軌燃油系統(tǒng)和新款氣缸蓋加冷卻劑通道設(shè)計(jì)也有助于同時(shí)降低A26的燃耗和排放。
除了部件材料方面的選擇，簡(jiǎn)化設(shè)計(jì)還有助于保證A26發(fā)動(dòng)機(jī)“重量輕”的優(yōu)勢(shì)。具體來(lái)說(shuō)，萬(wàn)國(guó)卡車(chē)為這款A(yù)26發(fā)動(dòng)機(jī)采用了1款鈦材料壓縮機(jī)輪（而非原來(lái)的鋁制機(jī)輪），從而保證更長(zhǎng)的正常運(yùn)行時(shí)間并減輕重量。復(fù)合材料閥門(mén)和鋁制飛輪外殼也進(jìn)一步為A26降低了重量。
為了優(yōu)化NVH性能，A26還采用了全新的曲軸箱、獨(dú)立油盤(pán)及橡膠墊設(shè)計(jì)，以便吸收震動(dòng)。公司還決定放棄之前的11葉片設(shè)計(jì)，轉(zhuǎn)而采用了1款6葉風(fēng)扇，可以提供更加安靜的運(yùn)轉(zhuǎn)表現(xiàn)及更低的功耗。此外，A26的發(fā)動(dòng)機(jī)校準(zhǔn)也經(jīng)過(guò)專(zhuān)門(mén)編程，可以降低發(fā)動(dòng)機(jī)噪音。
皆可博車(chē)輛系統(tǒng)（Jacobs Vehicle Systems）與納威司達(dá)（Navistar）的工程師聯(lián)手為這款A(yù)26發(fā)動(dòng)機(jī)提供了一款原廠壓縮釋放式發(fā)動(dòng)機(jī)制動(dòng)器。雅各布斯公司表示，“通過(guò)采用這款全新可變幾何渦輪，A26發(fā)動(dòng)機(jī)在較低轉(zhuǎn)速和較高海拔地區(qū)的制動(dòng)性能取得了67%的提升。”此外，這款渦輪增壓器還可以減少所需降速檔位的數(shù)量，并提供更好的NVH性能。
α項(xiàng)目推動(dòng)研發(fā)加速進(jìn)行
作為萬(wàn)國(guó)卡車(chē)公司的全新發(fā)動(dòng)機(jī)研發(fā)計(jì)劃，α項(xiàng)目旨在從各個(gè)方面優(yōu)化公司的發(fā)動(dòng)機(jī)設(shè)計(jì)。卡車(chē)及零部件總裁Bill Kozek表示，“α項(xiàng)目已經(jīng)從根本上改變了我們的柴油發(fā)動(dòng)機(jī)設(shè)計(jì)。”具體來(lái)說(shuō)，α項(xiàng)目的參與團(tuán)隊(duì)人員安排非常精簡(jiǎn)，這可以保證更快的響應(yīng)和決策速度。此外，團(tuán)隊(duì)成員在進(jìn)行決定時(shí)還被賦予了更大的自主權(quán)，不僅要達(dá)到2017年的排放規(guī)定，還要從四項(xiàng)關(guān)鍵指標(biāo)入手，對(duì)發(fā)動(dòng)機(jī)產(chǎn)品進(jìn)行最全面的整體優(yōu)化。
α項(xiàng)目達(dá)成的共識(shí)之一是利用行業(yè)成熟技術(shù)，而非利用客戶(hù)來(lái)試驗(yàn)新的產(chǎn)品。重型發(fā)動(dòng)機(jī)產(chǎn)品線營(yíng)銷(xiāo)經(jīng)理Jim Nachtman簡(jiǎn)單表示，公司的策略是“留下最好的，優(yōu)化其他的。”A26的曲軸、主軸承和連桿軸承、EGR冷卻器與閥門(mén)、汽油和燃油濾清器、空氣壓縮機(jī)、飛輪外殼等多項(xiàng)其他部件均沿用了納威司達(dá)N13發(fā)動(dòng)機(jī)的設(shè)計(jì)。不過(guò)，為了將A26發(fā)動(dòng)機(jī)的壓縮比提升至18.5:1，許多往復(fù)式部件的設(shè)計(jì)均進(jìn)行了改變，比如連桿、活塞銷(xiāo)和活塞等。此外，為了優(yōu)化燃料經(jīng)濟(jì)性而不同時(shí)增加過(guò)多復(fù)雜度，公司決定采用一款速度較慢的單速水泵，而非變速泵設(shè)計(jì)。
α團(tuán)隊(duì)已經(jīng)對(duì)A26發(fā)動(dòng)機(jī)進(jìn)行了成千上萬(wàn)小時(shí)的測(cè)功器試驗(yàn)，各個(gè)發(fā)動(dòng)機(jī)轉(zhuǎn)速和各級(jí)別負(fù)載均有覆蓋。Kozek說(shuō)，“A26發(fā)動(dòng)機(jī)進(jìn)行了極端測(cè)試，B10壽命達(dá)到了前所未有的120萬(wàn)英里（192萬(wàn)公里）。”由于采用了熱疲勞性能更好的CGI-緊密石墨鑄鐵材料曲柄箱（相較于之前的傳統(tǒng)灰口鑄鐵材料），A26的極限工作溫度可低至-40°F(-40°C)。
A26發(fā)動(dòng)機(jī)將會(huì)首先搭載于萬(wàn)國(guó)LT系列卡車(chē)。萬(wàn)國(guó)卡車(chē)公司還將為A26提供為期2年的不限里程保修。A26發(fā)動(dòng)機(jī)是萬(wàn)國(guó)卡車(chē)公司新一代發(fā)動(dòng)機(jī)中的第一款，未來(lái)定將攜手α項(xiàng)目帶領(lǐng)公司走向一個(gè)新的開(kāi)始。
Any time a new engine is announced, it is major news. Pairing a new engine with a new approach to engine development is even bigger news. International Truck recently unveiled its all-new engine for the Class 8 market called the International A26. Along with that came news of an initiative called Project Alpha, which brought together a small team of powertrain engineers dedicated to a new perspective on engine development.
"The A26 was designed from the ground up to deliver industry-leading uptime, durability and reliability," said Darren Gosbee, vice president of advanced engineering. The 12.4-L A26 sources a MAN D26 inline 6-cylinder crankcase from their partnership with the Volkswagen Group and surrounds it with numerous all-new components to optimize four key criteria: uptime, fuel efficiency, weight and NVH (noise, vibration and harshness).
The engine weighs only 2299 lb (1043 kg), which is 55 lb (25 kg) less than the Navistar N13 engine it replaces and 600-700 lb (272-318 kg) lighter than traditional 15-L big bore engines. Despite the reduction in weight, the engine can still produce up to 475 hp (354 kW) and 1750 lb·ft (2373 N·m).
Simplicity was one of the focal points of the engine design to deliver maximum uptime. “The A26 is as simple as a modern engine can be, and we’ve built uptime into every part of the development process, from design to calibration to testing,” said Gosbee. Larger piston pins, connecting rods and bushings are used for better load distribution. Smaller piston cooling jets have increased oil pressure and help extend oil change service intervals up to 70,000 mi (112,654 km).
Other improvements across engine systems have helped deliver up to a 5% increase in fuel economy. The new BorgWarner single-stage variable geometry turbocharger leads off a simplified air management system. The Bosch 2500-bar (36,259-psi) high pressure common rail fuel system and new cylinder head with coolant passages that are 50% less restrictive help reduce both fuel consumption and emissions.
Simplification also helped lead to keeping the International A26 light weight, in addition to component material choices. A titanium compressor wheel was used instead of aluminum for improved fatigue life while continuing to reduce weight. Composite valve covers and an aluminum flywheel housing provided additional weight savings.
To improve NVH, the A26 has been given a new sculpted crankcase with an isolated oil pan and rubber gasket designed to absorb vibrations. A six-blade fan was decided over the previous eleven-blade, which allows for quieter operation in addition to reducing power consumption. The engine calibration is also programmed for reduced engine noise.
Jacobs Vehicle Systems collaborated with Navistar engineers to provide a factory-installed compression release engine brake for the A26 engine. “By leveraging the benefits of the new variable geometry turbo, the A26 engine brake performance increased up to 67% at lower engine speeds and higher altitudes,” according to Jacobs. Other stated benefits include a reduction in the need for downshifting and improved NVH.
Project Alpha initiative speeds development
All of these improvements were the goal of Project Alpha, a brand-new initiative by International for this engine’s development. “Project Alpha has fundamentally changed how we design diesel engines,” says Bill Kozek, president of Truck and Parts. The group was formed using fewer members to speed up and focus engine design decisions. They were also given more autonomy in their decision making to not only meet the 2017 emissions regulations but improve the overall product performance in those four key areas.
One of the mandates Project Alpha decided on was to leverage proven industry technologies over testing new ones on customers. “Keep the best and improve the rest,” was a mantra for Jim Nachtman, marketing manager of Heavy-Duty Product Line. The crankshaft, main and rod bearings, EGR cooler and valves, oil and fuel filters, air compressors and flywheel housing along with several other components were carried over from the Navistar N13 engine. However, many of the reciprocating components like the connecting rods, piston pins and pistons were replaced to increase the compression ratio up to 18.5:1. A slower, single-speed water pump was decided over a variable speed pump to improve the fuel economy without the complexity.
The Project Alpha team put the A26 engine through hundreds of thousands of hours of dynamometer testing at severe engine speeds and loads. “It’s been tested to extremes and meets a demanding B10 design life standard for an unprecedented 1.2 million miles,” said Kozek. The engine was temperature tested as low as -40°F (-40°C), which was aided by a switch to Compact Graphite Iron (CGI) for the crankcase which has better thermal fatigue than previous traditional gray iron.
The A26 will now be available in the International LT Series trucks. International is backing the engine with a two-year, unlimited mile warranty. It is the first of a new wave of engines for International trucks. The Project Alpha team and A26 engine are a new beginning for the brand.
Author: Matthew Borst
Source: SAE Automotive Engineering Magazine
萬(wàn)國(guó)卡車(chē)（International Truck）公司決定放棄之前的11葉片設(shè)計(jì)，轉(zhuǎn)而為這款A(yù)26發(fā)動(dòng)機(jī)搭配了1款6葉風(fēng)扇，可以實(shí)現(xiàn)更加安靜的運(yùn)行表現(xiàn)，及更低的功耗。
萬(wàn)國(guó)卡車(chē)A26發(fā)動(dòng)機(jī)采用了Jacobs(皆可博)的發(fā)動(dòng)機(jī)制動(dòng)系統(tǒng)。Jacobs (皆可博)和萬(wàn)國(guó)卡車(chē)通過(guò)為A26搭配一款新型可變幾何形狀渦輪，最高可將這款發(fā)動(dòng)機(jī)的低速運(yùn)轉(zhuǎn)制動(dòng)性能提升67%。
為了將壓縮比提升至18.5:1，A26發(fā)動(dòng)機(jī)的許多往復(fù)式部件均進(jìn)行了一些改變，比如連桿、活塞銷(xiāo)和活塞等。
A26發(fā)動(dòng)機(jī)將會(huì)首先搭載于萬(wàn)國(guó)LT系列卡車(chē)。