在SAE 2017高效內(nèi)燃發(fā)動機(jī)研討會（2017 SAE High-Efficiency IC Engines Symposium）上，美國環(huán)保署輕型汽車與小型發(fā)動機(jī)中心（Light-Duty Vehicle and Small-Engine Center）主任Michael Olechiw告訴在場觀眾，盡管特朗普政府已經(jīng)表示有意回調(diào)奧巴馬總統(tǒng)在2012年出臺的雄心勃勃的公司平均燃料經(jīng)濟(jì)性標(biāo)準(zhǔn)（CAFE），且很多汽車制造商也突然“拋棄”了在過去5年中一直遵循的產(chǎn)品研發(fā)指導(dǎo)方針。然而，隨著直噴燃料系統(tǒng)和高級變速器等“主流”動力系統(tǒng)的迅猛發(fā)展，汽車制造商很有可能在2025年前真正實(shí)現(xiàn)54.4 mpg（3.4L/100 km）的燃料經(jīng)濟(jì)性目標(biāo)。
盡管，汽車行業(yè)主要游說團(tuán)體曾表示，汽車廠商為實(shí)現(xiàn)2025年CAFE標(biāo)準(zhǔn)所需付出的成本“非常驚人”。不過，Olechiw向在場消費(fèi)者展示了環(huán)保署的最新成本評估結(jié)果：對于2021到2025型號年的車型來說，采用“非常傳統(tǒng)的技術(shù)”實(shí)現(xiàn)2025年CAFE目標(biāo)的成本僅為每車825美元。他補(bǔ)充說，與此同時(shí)，選擇達(dá)到CAFE標(biāo)準(zhǔn)的車型還能幫消費(fèi)者節(jié)省大約1650美元的燃料支出，相當(dāng)于成本的2倍。
Olechiw表示，目前，美國市場中近50%的輕型車均采用了直噴系統(tǒng)，其中馬自達(dá)品牌車型的直噴系統(tǒng)配備率高達(dá)100%，其他6家大型制造商的配備率也達(dá)到了75%以上。此外，目前美國市場中采用7速以上變速器的車型占新車型總數(shù)的20%；CVT系統(tǒng)的配備率也差不多在20%上下。
Olechiw承認(rèn)，盡管目前全美僅有5%的車型達(dá)到了2025年CAFE標(biāo)準(zhǔn)（且這些車型均為混動汽車或全電動汽車），但他并不認(rèn)為消費(fèi)者對重型卡車和跨界車的購買偏好，一定會讓54.5mpg的終極燃料經(jīng)濟(jì)性目標(biāo)成為泡影。根據(jù)環(huán)保署的規(guī)定，較大車型本身就允許比小型車排放更多尾氣。環(huán)保署對目前的進(jìn)展感到滿意：“到目前為止，一切都在按計(jì)劃進(jìn)行。”Olechiw介紹道。
排放“額度”
Olechiw表示，自CAFE標(biāo)準(zhǔn)實(shí)施以來，汽車廠商已經(jīng)累計(jì)了大約280兆克的排放額度。他解釋說，廠商所有面向美國市場的車型每行駛1英里減少CO2排放80克可以換來1兆克額度。這樣看來，這些廠商已經(jīng)累計(jì)了足夠額度，可以滿足最初幾年的合規(guī)要求。
此外，Olechiw還肯定了CAFE標(biāo)準(zhǔn)在基礎(chǔ)發(fā)動機(jī)能效持續(xù)明顯優(yōu)化方面發(fā)揮的重要作用。2008年，美國環(huán)保署表示，汽油發(fā)動機(jī)的峰值熱效率約為34%；到2016年，隨著直噴系統(tǒng)等技術(shù)的不斷普及，這一數(shù)字已經(jīng)提升至36%。Olechiw表示，目前采用了全部或大部分最新能效技術(shù)的小型渦輪增壓發(fā)動機(jī)可以取得大約38%的熱效率。
Olechiw說，今年3月初，特朗普政府組建的新環(huán)保署表示將重新審視2025年CAFE標(biāo)準(zhǔn)（原本已寫入相關(guān)法律），并在2018年前給出最終決定。
Although the Trump Administration has indicated intent to roll back the ambitious light-vehicle fuel-economy standards initiated by President Obama in 2012—and many automakers suddenly have reversed their advocacy of the guidelines that shaped product-development plans for the past half-decade—Michael Olechiw, director of the U.S. Environmental Protection Agency’s Light-Duty Vehicle and Small-Engine Center, told attendees at the SAE’s 2017 High-Efficiency IC Engine Symposium in Detroit that swiftly “mainstreaming” powertrain advances such as direct fuel injection and advanced transmissions are bringing automakers the kind of fuel-economy gains that make attainable the goal of fleet-average fuel economy of 54.4 mpg (3.4L/100 km) by 2025.
Moreover, while the auto industry’s primary lobbying group called the potential cost to comply with the 2025 regulations “staggering,” Olechiw presented the EPA’s most recent estimate of the cost to consumers: about $825 per vehicle in the 2021-25 model years—using “very much conventional technologies.” Meantime, he added, consumers would reap a fuel-cost savings equivalent to double the cost: about $1,650.
Olechiw said direct fuel injection (DI) now is fitted to nearly 50% of all new light vehicles sold in the U.S., with automakers such as Mazda at 100% and six other OEMs with 75% or more of their engines fitted with DI. And vehicles with transmissions with at least seven forward speeds now account for about 20% of all new models; the number is similar for continuously variable transmissions (CVTs).
Although admitting that only about 5% of current models would comply with the 2025 CAFE regulations (and all of them are hybrid-electric or full-electric), Olechiw dispelled the notion that the marked consumer shift to heavier trucks and crossover models will make it impossible to attain the final goal of 54.5 mpg. The regulations’ “footprint”-based structure allows larger, heavier models to emit relatively more than smaller vehicles and the EPA is satisfied with the results: “So far, the program has been working just as designed,” he said.
Emissions credits to go around
As validation, Olechiw said there currently are about 280 megagrams of credits that automakers have generated since the start of the phase-in period. A megagram is equivalent to about 80 g of CO2 reduction per mile for the entire U.S. vehicle fleet and there are sufficient “banked” credits, he said, to bring the U.S. fleet into compliance for several years.
He also tacitly gives credit to the CAFE regulations for fostering a consistent and distinct advance in fundamental engine efficiency. In 2008, the EPA said gasoline-engine peak thermal efficiency was about 34%; by 2016, with the increasing penetration of DI and other advances, thermal efficiency rose to 36%. Now, Olechiw said, downsized and turbocharged engines incorporating all or most of the latest efficiency-enhancing technologies have reached about 38% efficiency.
Olechiw said that in early March the new Trump Administration’s EPA concluded it will review the 2025 regulations (an action originally provided for in the law) and will by issue its Final Determination regarding the standards by 2018.
Author: Bill Visnic
Source: SAE Automotive Engineering Magazine
美國環(huán)保署認(rèn)為，一些創(chuàng)新節(jié)能技術(shù)將為全美車輛燃料經(jīng)濟(jì)性的提升做出貢獻(xiàn)，比如這款福特10速自動變速器（圖片來源：福特）。