今年初，吉?jiǎng)P恩航宇(GKN Aerospace)公司表示,已經(jīng)向一個(gè)大型研究項(xiàng)目交付了公司研發(fā)的機(jī)翼元件。該項(xiàng)目會(huì)在一架測(cè)試飛機(jī)的機(jī)翼上進(jìn)行試驗(yàn)，測(cè)試與測(cè)量自然層流(NLF)設(shè)計(jì)的優(yōu)勢(shì)。據(jù)悉，歐洲的清潔天空(Clean Sky)智能固定翼飛機(jī)（Smart Fixed Wing Aircraft，下簡(jiǎn)稱SWFA）計(jì)劃旨在通過減少飛行阻力，降低下一代飛機(jī)的燃料消耗和尾氣排放。該大型計(jì)劃的經(jīng)費(fèi)50%來自歐盟，也同時(shí)獲得了多方的參與和支持，吉?jiǎng)P恩參與的歐洲突破性層流翼驗(yàn)證機(jī)（Breakthrough Laminar Aircraft Demonstrator in Europe，下簡(jiǎn)稱BLADE）項(xiàng)目也是該計(jì)劃的一部分。
吉?jiǎng)P恩航宇公司高級(jí)工程技術(shù)副總裁Russ Dunn表示，“通過SFWA計(jì)劃下的BLADE項(xiàng)目，我們可以推進(jìn)有潛力的創(chuàng)新技術(shù)、概念和功能，進(jìn)一步提升飛機(jī)的燃料經(jīng)濟(jì)性。”
吉?jiǎng)P恩航宇公司提供的關(guān)鍵機(jī)翼前緣總成和上蓋，目前已經(jīng)用于空客(Airbus)A340試飛機(jī)右翼的NLF翼截面。由于采用了全新的設(shè)計(jì)方法和創(chuàng)新制造技術(shù)，吉?jiǎng)P恩得以提供一種具有超高耐受性的特殊表面，從而達(dá)到NLF級(jí)別的性能表現(xiàn)。
在2017年的飛行試驗(yàn)中，該翼截面將承擔(dān)測(cè)試NLF機(jī)翼結(jié)構(gòu)性能與特點(diǎn)的任務(wù)，從而協(xié)助驗(yàn)證預(yù)期可以取得的經(jīng)濟(jì)和環(huán)境效益：根據(jù)預(yù)測(cè)，采用NLF機(jī)翼可以將飛機(jī)的飛行風(fēng)阻降低8%，燃油經(jīng)濟(jì)性提升大約5%。
“無論能夠帶來多少空氣動(dòng)力學(xué)優(yōu)勢(shì)，設(shè)計(jì)與制造NLF機(jī)翼的關(guān)鍵挑戰(zhàn)仍在于嚴(yán)格控制機(jī)翼的表面。”Dunn表示，“消除機(jī)翼表面的突起、縫隙、粗糙、不平整處，以及緊固件的接頭至關(guān)重要，因?yàn)檫@些都會(huì)讓飛機(jī)落入更加傳統(tǒng)的‘湍流(turbulent flow)’性能級(jí)別。吉?jiǎng)P恩航宇的團(tuán)隊(duì)曾利用民用飛機(jī)項(xiàng)目中的結(jié)構(gòu)設(shè)計(jì)和研發(fā)流程，打造了一批整合式共固化(co-cured)復(fù)合上蓋，以及具有超高耐受性的機(jī)翼前緣表面。結(jié)果，我們的第一批零部件質(zhì)量非常高，已經(jīng)交付給飛行測(cè)試項(xiàng)目使用。”
幾年前，為了基于地面演示（ground based demonstrator，簡(jiǎn)稱GBD）而研發(fā)的機(jī)翼是一款面積為4.5 m x 1 m的機(jī)翼前緣。該前緣連接在部分機(jī)翼翼盒(partial wing box)之上，非常具有代表性。這種前緣設(shè)計(jì)可以將機(jī)翼分為兩個(gè)區(qū)域，允許吉?jiǎng)P恩的工程師探索兩種截然不同的設(shè)計(jì)哲學(xué)。
其中，“基礎(chǔ)”部分采用了常見于絕大多數(shù)金屬前緣的傳統(tǒng)設(shè)計(jì)，即為翼肋增加了一層整體復(fù)合皮。而“創(chuàng)新”部分則采用了更加激進(jìn)的設(shè)計(jì)，從而解決基礎(chǔ)設(shè)計(jì)不能達(dá)到NLF級(jí)耐受性需求的問題。本部分采用了一款輕質(zhì)前緣夾板，結(jié)合使用了電熱機(jī)翼除冰保護(hù)(wing ice protection)技術(shù)、防腐蝕涂層，以及沒有采用緊固件的外表面。
在Krueger創(chuàng)新設(shè)計(jì)中，團(tuán)隊(duì)還采用了增材制造工藝，打造機(jī)翼支撐結(jié)構(gòu)，替代基礎(chǔ)設(shè)計(jì)中的鋁制翼肋。這樣一來，僅需三根翼肋就能完成支撐前緣壁板的任務(wù)，分別為一根中央翼肋和二根端部翼肋。這樣的設(shè)計(jì)能夠確保機(jī)翼前緣可以在任何正常工作溫度下，保持合理的空氣動(dòng)力學(xué)性能。與基礎(chǔ)部分相比，創(chuàng)新部分使用的元件和緊固件數(shù)量更少，因此質(zhì)量也更輕，可以極大地提高能效。
本項(xiàng)目由吉?jiǎng)P恩航宇的3個(gè)英國(guó)技術(shù)中心合作完成，分別為英國(guó)國(guó)家復(fù)合材料中心(National Composites Center)、位于盧頓的吉?jiǎng)P恩航宇，以及位于布里斯托爾的吉?jiǎng)P恩航宇增材制造中心。
作者：Jean L. Broge
來源：SAE 《航空航天工程》雜志
翻譯：SAE 上海辦公室
Innovative GKN wing structure contributes to Clean Sky next-gen aircraft
GKN Aerospace announced in January that it has delivered wing components as part of a major research program to test and measure the benefits of natural laminar flow (NLF) designs during trials on the wing of a flight test aircraft. The Breakthrough Laminar Aircraft Demonstrator in Europe (BLADE) project is part of the Clean Sky Smart Fixed Wing Aircraft (SWFA) program, an extensive, 50% European Union-funded, multi-partner activity aimed at lowering fuel consumption and emissions by reducing drag on next-generation.
“The SFWA BLADE program is allowing us to progress innovative technologies, concepts and capabilities with the potential to bring about a step change in aircraft fuel consumption,” said Russ Dunn, Senior Vice President, Engineering and Technology at GKN Aerospace.
GKN Aerospace has delivered the critical leading edge assemblies and upper covers that form part of the NLF wing section on the starboard wing of the Airbus A340 flight test aircraft. These structures offer NLF levels of performance through the adoption, by GKN Aerospace, of a totally new design approach and the application of novel manufacturing technologies that deliver the ultra-high tolerances and exceptional surface finish required.
During flight tests, taking place in 2017, this wing section will be used to test the performance characteristics of NLF wing architecture, helping prove predicted economic and environmental benefits: An NLF wing is expected to reduce wing drag by 8% and improve fuel consumption by approaching 5%.
“The key challenge with designing and manufacturing an NLF wing, with the many aerodynamic benefits that promises, stems from the need to tightly control the wing surface,” said Dunn.“It is vital to eliminate features such as steps, gaps, surface roughness and waviness or fastener heads as these all lead to more traditional ‘turbulent flow’ performance levels. The GKN Aerospace team has created these integrated, co-cured composite upper covers and very high tolerance leading edge surfaces using the same structured design and development process applied in commercial aircraft programs. As a result, our first part was of very high quality and has been delivered for the flight test program.”
The ground based demonstrator (GBD) of the wing developed a couple years ago was a 4.5 m x 1 m section of flight-representative wing leading edge attached to a partial wing box assembly. The leading edge accommodated a Krueger flap in two sections, which allowed GKN engineers to investigate two very different design philosophies.
The first "baseline" section applied a monolithic composite skin to the traditional rib design seen on the majority of metallic leading edges today. The second "innovative" section applied a more radical design to address issues experienced meeting NLF tolerances with the baseline design. This section comprised a lightweight leading edge sandwich panel incorporating electro-thermal wing ice protection technology with an integrated erosion shield and fastener-free outer surface.
Additive manufacturing processes were used to create a novel support structure for the Krueger mechanism, replacing the aluminum ribs in the baseline design. This allowed the leading edge panel to be supported by just three composite ribs: a single central rib and two closing ribs. These maintain the correct leading edge aerodynamic profile over the complete range of operating temperatures. The innovative section had a lower component and fastener count, was significantly lighter, and had greatly improved performance predictions compared to the baseline section.
The overall project was a collaboration between three GKN Aerospace technology centres in the U.K.: a team at the U.K.’s National Composites Center, at GKN Aerospace in Luton, and at the GKN Aerospace additive manufacturing center in Bristol.
Author: Jean L. Broge
Source: SAE Aerospace Engineering Magazine
吉?jiǎng)P恩航宇的創(chuàng)新機(jī)翼前緣總成，已交付給空客的清潔藍(lán)天BLADE項(xiàng)目。
Clean Sky的SFWA項(xiàng)目中生產(chǎn)的創(chuàng)新機(jī)翼前緣復(fù)合夾板，圖為地面展示階段的產(chǎn)品。