沃爾沃通過使用壓縮空氣，提高全新D5柴油發(fā)動機的扭矩，并消除“延遲”。沃爾沃的工程師駕駛一輛搭載D5發(fā)動機的V90休旅車，在西班牙南部進行了一段路程漫長，而且經(jīng)常路況苛刻的試駕。事實上，正如沃爾沃的工程師在試駕中向《汽車工程雜志》所展示的那樣，這種技術(shù)相對簡單，但卻非常高效。
沃爾沃將這款采用了大量專利技術(shù)的創(chuàng)新柴油送氣系統(tǒng)稱為“PowerPulse”，該技術(shù)可以替代搭配電驅(qū)動渦輪增壓器或超級增壓器的48V混動系統(tǒng)。系統(tǒng)能夠在發(fā)動機轉(zhuǎn)速較低時，迅速驅(qū)動渦輪轉(zhuǎn)動，并且成本低廉。
為了研發(fā)PowerPulse，沃爾沃的動力總成工程師總共花了三年多的時間，這一技術(shù)的關(guān)鍵路徑與D5發(fā)動機相同。據(jù)稱，這款2.0升4缸直噴柴油發(fā)動機可以輸出173 kW（232 hp）的動力和480N·m（354 lb·ft）的扭矩。此外，公司還有一款未采用PowerPulse技術(shù)的D4發(fā)動機。這款D4發(fā)動機功率較低，可以輸出140 kW（188 hp）的動力和400N·m（295 lb·ft）的扭矩。
一個簡單緊湊的系統(tǒng)
在行駛過程中，PowerPulse技術(shù)的作用非常明顯，它可以協(xié)助V90休旅車實現(xiàn)7.2秒內(nèi)由靜止加速至100km/h (62 mph)。以V90的功率輸出水平和1817kg（4006 lb）的整備質(zhì)量來看，這樣的表現(xiàn)還算敏捷，但稱不上異常出色。V90休旅車采用了一款8速愛信（Aisin）自動變速器，沒有手動擋版本。
沃爾沃動力總成項目經(jīng)理Fredrik Ulmhage表示，PowerPulse完全是一款沃爾沃自主研發(fā)的產(chǎn)品。“其他公司都沒有這種技術(shù)。”Ulmhage斷言，“公司計劃推廣4缸柴油發(fā)動機（我們也有汽油發(fā)動機發(fā)展計劃），但必須先解決渦輪延遲的問題，也就是在廢氣產(chǎn)生壓強之前，先讓渦輪轉(zhuǎn)起來。”
Ulmhage解釋說，“因此，簡單來說，我們就是在駕駛員踩下油門的同時，將壓縮空氣推入車輛的排氣歧管，渦輪在幾毫秒之內(nèi)就可以開始加速轉(zhuǎn)動。”
這個過程可以連續(xù)進行2次，中間幾乎沒有停頓。但是，如果需要連續(xù)3次送氣（這種可能性非常低），系統(tǒng)則需要幾秒時間準備壓縮空氣。系統(tǒng)中存在一個小型壓縮機，能夠以12 bar（174 psi）的壓強將空氣擠進一個2.0L的氣箱內(nèi)，而系統(tǒng)的動作則由一個電磁閥控制。
沃爾沃D5發(fā)動機搭配了兩個尺寸分別為38 mm和53 mm的博格華納(BorgWarner)渦輪增壓器，這兩個增壓器按順序依次進行運轉(zhuǎn)。據(jù)沃爾沃的工程師稱，該系統(tǒng)可在0.3秒內(nèi)從怠速狀態(tài)加速至150,000 rpm的峰值轉(zhuǎn)速。Ulmhage指出，“與其他友商的6缸柴油發(fā)動機相比，我們的新4缸發(fā)動機在最初50~60米都處領(lǐng)先地位。”他同時確認，沃爾沃 XC90 SUV將采用PowerPulse技術(shù)。此外，PowerPulse還有可能配備在更多新車型上。
PowerPulse系統(tǒng)重約10kg（22 lb），完全可以安裝在位于發(fā)動機蓋下的頭燈底座后方。為了減輕壓力罐的重量，沃爾沃的工程師正在研究各種可能使用在這里的輕質(zhì)材料。
為了提高汽油發(fā)動機的能效，使之達到與柴油發(fā)動機類似的水平，沃爾沃開展了一系列以提升混合動力能效為重點的優(yōu)先技術(shù)項目。
據(jù)悉，沃爾沃即將推出一款3缸汽油發(fā)動機，預計額定輸出功率超過130 kW (174 hp)。這款發(fā)動機將配備在一些功率較小的沃爾沃車型上。與柴油機相比，這款3缸汽油發(fā)動機不僅可以帶來出色的能效，而且成本也更低，原因在于為了達到排放標準，而不得不在柴油發(fā)動機上采用更多的發(fā)動機控制手段和后處理系統(tǒng)，而汽油發(fā)動機這方面的需求較低。
除了V90，沃爾沃還將推出一款新的汽油機車型——S90 T6轎車，這也體現(xiàn)了沃爾沃與梅賽德斯-奔馳（Mercedes-Benz）和奧迪（Audi）一決高下的決心。V90和S90 T6這兩個車型均采用了沃爾沃的可擴展整車平臺架構(gòu)，XC90也是如此。
福特沃爾沃vs.吉利沃爾沃
沃爾沃的產(chǎn)品經(jīng)理Lars Lagström表示，如今，沃爾沃已經(jīng)擁有了一個可以滿足汽車架構(gòu)和底盤動力需求，帶來一流駕乘體驗的平臺?，F(xiàn)在，公司開始將目光轉(zhuǎn)向NVH（噪聲、振動和不平順性）特性和其他細節(jié)的改善。Lagström將吉利沃爾沃和過去的福特沃爾沃進行了比較，他提到，福特掌管沃爾沃的時候永遠都在“控制預算”，并且“對待所有事情都目光短淺”，Lagström還說：“福特永遠也無法理解沃爾沃。”
沃爾沃開展了一系列重點研發(fā)項目，其中包括一款內(nèi)部研發(fā)的獨立后懸掛系統(tǒng)。正是憑借這款懸掛系統(tǒng)，V90才能輕松征服公路駕駛環(huán)境，甚至連一些極具挑戰(zhàn)性的彎道也不在話下。除了懸掛，內(nèi)飾設(shè)計也是沃爾沃的另一個亮點，這要得益于公司內(nèi)飾設(shè)計副總裁Robin Page（他在2013年前服務于賓利）。當你坐進這輛新款柴油休旅車的那一刻，車輛的內(nèi)飾設(shè)計一定會讓你眼前一亮。V90可以提供560到1526 升的超大儲物空間，但由于巧妙利用了地板下的位置，這款車的外形并未受到影響，仍然非常有型。V90的空氣動力學性能表現(xiàn)也相當不錯，車輛的風阻系數(shù)最低可達0.30 Cd。
隨著自動駕駛技術(shù)的不斷發(fā)展，沃爾沃V90和S90均具備領(lǐng)航輔助（Pilot Assist）功能和自適應巡航控制（Adaptive Cruise Control）功能。在有道路標記的車道內(nèi)，這兩款車可以在時速不超過130 km/ h (81 mph)的情況下，進行一系列半自動駕駛操作，包括轉(zhuǎn)向、加速和制動。但值得注意的是，這還并不是一個全自動駕駛系統(tǒng)。
作者：Stuart Birch
來源：SAE《汽車工程》雜志
翻譯：SAE 中國辦公室
Volvo bets on new PowerPulse, not 48V, for turbodiesel boost assist
Volvo is using a blast of compressed air to boost torque delivery and exorcise turbo "lag" of its new D5 diesel engine. It's a comparatively simple technology solution that works very effectively, as company engineers demonstrated to Automotive Engineering on a lengthy and often demanding test drive of the D5-powered V90 station wagon in southern Spain.
Volvo has dubbed the novel, heavily patented diesel air-delivery system "PowerPulse." It serves as a cost-effective alternative to using a 48-V hybrid system with electrically-driven turbocharger or supercharger to rapidly spin up turbines at low engine revs.
Volvo powertrain engineers spent more than three years developing PowerPulse, on the same critical path as the D5 engine. The 2.0-L 4-cylinder direct injected diesel delivers a claimed 173 kW (232 hp) and 480 N·m (354 lb·ft). A lower-powered D4 version producing 140 kW (188 hp) and 400 N·m (295 lb·ft) without PowerPulse also is available.
A simple, compact system
On the road PowerPulse literally blows into action, helping the V90 wagon accelerate from standing start to 100 km/h (62 mph) in 7.2 s which, bearing in mind the car’s power output and 1817-kg (4006-lb) curb weight, is brisk but not exceptional. The car’s automatic transmission is an 8-speed Aisin. No manual gearbox is offered.
Powertrain Program Manager Fredrik Ulmhage said the PowerPulse system was conceived entirely in-house. “No one else has it," he asserted. "We have a 4-cylinder diesel strategy (as we have for our gasoline engines) and decided we needed to deal with any turbo lag, getting the turbo running before exhaust pressure built.
"So basically, we push compressed air into the exhaust manifold as the driver pushes the accelerator pedal and within milliseconds the turbo spools up,” Ulmhage explained.
This can happen twice consecutively, with virtually no pause between applications. If a third rapidly-required consecutive step-off is needed (regarded as an extremely rare likelihood), it would take a couple of seconds for the system to re-charge to provide a further pulse. A small compressor squeezes air into a 2.0 L tank at a pressure of 12 bar (174 psi), with a magnetic valve controlling the action phase of the system.
Volvo's D5 engine is configured with two BorgWarner turbo machines sized 38 mm and 53 mm, respectively and operating sequentially. Engineers claim the system reaches its peak 150,000 rpm from idle in 0.3 s. “When we matched the system against competitors’ 6-cylinder diesel engines from stationary, our new 4-cylinder was ahead of them for up to 50 to 60 meters,” noted Ulmhage. He confirmed that Volvo's XC90 SUV will also be offered with PowerPulse. And the system is likely to be fitted to other upcoming models.
The PowerPulse system adds about 10kg (22 lb) to the base diesel engine. It fits into a convenient underhood space behind a headlamp housing. Volvo engineers are investigating lightweight materials that could be used to reduce mass of the pressure tank.
Volvo has a series of high-priority technology programs with the emphasis on hybrid efficiency and is aiming to take gasoline powertrains much closer to diesel fuel consumption potential.
A 3-cylinder gasoline engine is in the pipeline with a rated output expected to exceed 130 kW (174 hp). It will be used to power smaller Volvo models, bringing not only performance efficiency but also reduced unit cost compared to diesels, the cost of which rises as more engine controls and aftertreatment are incorporated to meet emission regulations.
The V90 is joined by the new gasoline-engine S90 T6 sedan (http://articles.sae.org/14568/), paired as part of Volvo’s determined bid compete with Mercedes-Benz and Audi. Both vehicles are underpinned by the company’s Scalable Product Architecture (http://articles.sae.org/12739/), as is the XC90.
Contrasting Geely and Ford
Finally possessing a platform the delivers the structure and chassis dynamics necessary to deliver premium-class ride quality, Volvo development engineers are now focusing on NVH and other details, stated Product Manager Lars Lagström. He contrasted the company's Geely ownership to the years under Ford, when "there were always squeezed budgets" and "it was short-term everything." Ford, Lagström noted, "never understood Volvo."
Key initiatives have included in-house development of the independent rear suspension that helps the V90 deliver a poised ride on motorways or challenging curves. Interior design is another priority, with the impact of Vice President of Interior Design Robin Page (with Bentley until 2013) immediately evident when you step inside the new diesel wagon. It offers 560 to 1526 L (20 to 54 ft3) of maximum luggage volume including underfloor storage while avoiding any hint of utilitarian styling. Aerodynamics of the V90 models achieve a best of 0.30 Cd.
With the approach of the age of autonomous driving, the V90 and S90 offer Pilot Assist and adaptive cruise control, which team to provide semi-autonomous operation of steering, accelerator and brakes within lane markings at speeds up to 130 km/ h (81 mph). But it is not a fully hands-off system.
Author: Stuart Birch
Source: SAE Automotive Engineering Magazine
沃爾沃4缸D5柴油發(fā)動機采用的PowerPulse（圖為壓縮機和壓力罐）系統(tǒng)重約10公斤，緊貼著安裝在V90休旅車的頭燈后方。
沃爾沃的PowerPulse系統(tǒng)可以利用壓縮空氣，推動柴油發(fā)動機的渦輪增壓器從怠速狀態(tài)開始加速運轉(zhuǎn)。該系統(tǒng)也將使用在XC90及更多其它即將推出的車型上。
PowerPulse與友商產(chǎn)品Step-off性能的對比，沃爾沃并未透露友商的具體名稱。
全新沃爾沃V90旅行車的尾部傾斜，給人一種賞心悅目的美感，但與之前版本相比，這種設(shè)計略微減少了車輛的儲物空間。
圖為沃爾沃V90旅行車的車身結(jié)構(gòu)材料構(gòu)成。