【導(dǎo)讀】結(jié)其故障原因及排除。隨著世界科學(xué)技術(shù)的迅猛發(fā)展，人們對汽車的舒適性、安全性、可靠性的要求不斷提高，空調(diào)系統(tǒng)已成為現(xiàn)代汽車的標(biāo)準(zhǔn)裝置。級進(jìn)口汽車已采用微型計算機(jī)控制的自動空調(diào)。此外，為適應(yīng)環(huán)保要求，新型的R134a制冷劑。正在逐漸取代R12制冷劑。冷的故障原因，并加以分析診斷，最后故障排除及做出總結(jié)。帕薩特B5是德國大眾汽車公司的帕薩特品牌轎車的第五代車型。2020年，上海大眾汽車。開發(fā)的，將原型的B5加長100mm，寬大的體形讓帕薩特更適合于國內(nèi)的商務(wù)車市場。轎車中的高端產(chǎn)品。上海大眾還對帕薩特B5進(jìn)行大的改進(jìn)，并取了一個別名：領(lǐng)馭。帕薩特的前懸掛采用四連桿獨(dú)立式懸掛，后懸掛采用復(fù)合扭轉(zhuǎn)梁式半獨(dú)立懸掛。以為乘車人員提供舒適的乘車環(huán)境，降低駕駛員的疲勞強(qiáng)度，提高行車安全。利用熱從溫度較高區(qū)域流至溫度較低區(qū)域的特性。

　　

【正文】 es. One must rely on engineering judgment and experience. In this paper, we develop a theory to estimate the impact of defeaturing on engineering analysis in an automated fashion. In particular, we focus on problems where the features being suppressed are cutouts of arbitrary shape and size within the body. Two mathematical concepts, namely adjoint formulation and monotonicity analysis, are bined into a unifying theory to address both selfequilibrating and nonselfequilibrating features. Numerical examples involving 2nd order scalar partial differential equations are provided to substantiate the theory. The remainder of the paper is anized as follows. In Section 2, we summarize prior work on defeaturing. In Section 3, we address defeaturing induced analysis errors, and discuss the proposed methodology. Results from numerical experiments are provided in Section 4. A byproduct of the proposed work on rapid design exploration is discussed in Section 5. Finally, conclusions and open issues are discussed in Section 6. 2. Prior work The defeaturing process can be categorized into three phases: Identification: what features should one suppress? Suppression: how does one suppress the feature in an automated and geometrically consistent manner? Analysis: what is the consequence of the suppression? 32 The first phase has received extensive attention in the literature. For example, the size and relative location of a feature is often used as a metric in identification [2,6]. In addition, physically meaningful ?mechanical criterion/heuristics‘ have also been proposed for identifying such features [1,7]. To automate the geometric process of defeaturing, the authors in [8] develop a set of geometric rules, while the authors in [9] use face clustering strategy and the authors in [10] use plane splitting techniques. Indeed, automated geometric defeaturing has matured to a point where mercial defeaturing /healing packages are now available [11,12]. But note that these mercial packages provide a purely geometric solution to the problem... they must be used with care since there are no guarantees on the ensuing analysis errors. In addition, open geometric issues remain and are being addressed [13]. The focus of this paper is on the third phase, namely, post defeaturing analysis, ., to develop a systematic methodology through which defeaturing induced errors can be puted. We should mention here the related work on reanalysis. The objective of reanalysis is to swiftly pute the response of a modified system by using previous simulations. One of the key developments in reanalysis is the famous Sherman–Morrison and Woodbury formula [14] that allows the swift putation of the inverse of a perturbed stiffness matrix。 other variations of this based on Krylov subspace techniques have been proposed [15–17]. Such reanalysis techniques are particularly effective when the objective is to analyze two designs that share similar mesh structure, and stiffness matrices. Unfortunately, the process of 幾何分析 can result in a dramatic change in the mesh structure and stiffness matrices, making reanalysis techniques less relevant. A related problem that is not addressed in this paper is that of local–global analysis [13], where the objective is to solve the local field around the defeatured region after the global defeatured problem has been solved. An implicit assumption in local–global analysis is that the feature being suppressed is selfequilibrating. 3. Proposed methodology . Problem statement We restrict our attention in this paper to engineering problems involving a scalar field u governed by a generic 2nd order partial differential equation (PDE): .).( fauuc ????? A large class of engineering problems, such as thermal, fluid and magostatic problems, may be reduced to the above form. As an illustrative example, consider a thermal problem over the 2D heatblock assembly Ω illustrated in Fig. 2. The assembly receives heat Q from a coil placed beneath the region identified as Ωcoil. A semiconductor device is seated at Ωdevice. The two regions belong to Ω and have the same material properties as the rest of Ω. In the ensuing discussion, a quantity of particular interest will be the weighted temperature Tdevice within Ωdevice (see Eq. (2) below). A slot, identified as Ωslot in Fig. 2, will be suppressed, and its effect on Tdevice will be studied. The boundary of the slot will be denoted by Γslot while the rest of the boundary will be denoted by Γ. The boundary temperature on Γ is assumed to be zero. Two possible boundary conditions on Γslot are considered: (a) fixed heat source, ., (k? rT).?n = q, or (b) fixed temperature, ., T = Tslot. The two cases will lead to two different results for defeaturing induced error estimation. 33 Fig. 2. A 2D heat block assembly. Formally,let T (x, y) be the unknown temperature field and k the thermal conductivity. Then, the thermal problem may be stated through the Poisson equation [18]: )1()().)((00).(?????????????????????????????s l c ts l c ts l c tc o i lc o i lTTboronqhkaonTinininQTkBCP D E Given the field T (x, y), the quantity of interest is: )2(),(),(????? ?? ??? d e v i c edycTyxHTC om pu t e d e v i c e where H(x, y) is some weighting kernel. Now consider the defeatured problem where the slot is suppressed prior to analysis, resulting in the simplified geometry illustrated in Fig. 3. Fig. 3. A defeatured 2D heat block assembly. We now have a different boundary value problem, governing a different scalar field t (x, y): )3(ΩΓo n 0t ΩΩ0 in ΩQ). ( kBCP D E c o i ls l o tc o i l????? ? ??? ?????? int )4(),(),(??? ?? ??? d e v i d ed e v i c e dyxtyxHtC o m p u t e Observe that the slot boundary condition for t (x, y) has disappeared since the slot does not exis