Design Optimization Of Air Intake System (AIS) Of 1.6L .

Proceedings of the International MultiConference of Engineers and Computer Scientists 2010 Vol II,IMECS 2010, March 17 - 19, 2010, Hong KongDesign Optimization of Air Intake System (AIS)of 1.6L Engine by Adding Guide VaneD.Ramasamy, Zamri.M, S. Mahendran, S.VijayanAbstract—Air intake system and filter play major role ingetting good quality air into automobile engine. It improves thecombustion efficiency and also reduces air pollution. This paperfocuses on optimizing the geometry of an intake system inautomobile industry to reduce the pressure drop and enhancethe filter utilization area by adding guide vane. 3D viscousComputational Fluid Dynamics (CFD) analysis was carried outfor an existing model to understand the flow behavior throughthe intake system, air filter geometry and ducting. Resultsobtained from CFD analysis of the existing model showed goodimprovement. Based on existing model CFD results,geometrical changes like guide vane placement in inlet plenumof the filter, optimization of mesh size, removal of contraction inclean pipe of intake system etc are carried out, to improve theflow characteristics. The CFD analysis of the optimized modelwas again carried out and the results showed goodimprovement in flow behavior. By using 3D CFD analysis,optimal design of the intake system for an automobile engine isachieved with considerable reduction in development time andcost.Index Terms—Air intake system, CFD, optimization,Automobile Engine.I. INTRODUCTIONThe main function of an air intake system is to supply theengine with clean air with correct amount for the required airto burn in the manifold chamber. The intake system of anengine has three main functions. Its first and usually mostidentifiable function is to provide a method of filtering the airto ensure that the engine receives clean air free of debris. Twoother characteristics that are of importance to the engineersdesigning the intake system are its flow and acousticperformance. The flow efficiency of the intake system has adirect impact on the power the engine is able to deliver. Theacoustic performance is important because governmentregulations dictate the maximum air mass flow level thatvehicles can make during a pass-by test. The speed of airgenerated by the intake system can be a significantcontributor to this pass-by filter and separated flow. It may benoted that since the loss pressure from the intake ducttowards atmosphere, this paper assumes the inlet is at theintake manifold and air filter duct and the outlet is atatmosphere or environmental pressure [1] [2].Manuscript received October 12, 2009. This work was supported in partby Universiti Malaysia Pahang.D. Ramasamy, S. Mahendran, Zamri.M and S.Vijayan is with Faculty ofMechanical Engineering, Universiti Malaysia Pahang, 26300 Pekan, Pahang,Malaysia (phone: 609-4242221 Fax: 609-4242202; e-mail:deva@ump.edu.my).ISBN: 978-988-18210-4-1ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online)To increase the performance of the Proton Waja,(Malaysian National car) combustion, it is required for theair to be as clean as possible in order for the engine to beas efficient as possible. Hence the air must in some waybe “cleaned” before it enters the combustion chamber. Thesystem that cleans the air and guides it into the cylindersis called an Air Intake System (AIS). The AIS may bedivided into three main parts: an inlet and intake sectionin which the incoming “dirty” air is guided into, afilter-box section where a filter is located that cleans thepolluted air and hinders soot and other particles fromentering the cylinders, and an inlet to the engine where theclean air is guided to the cylinders. Air enters the filterthrough dirty pipe and inlet side plenum, which guides theflow uniformly through the filter media. Optimum utilizationof filter can significantly reduce the cost of filterreplacements frequently and keep the filter in use for longertime. To optimize intake system and filter duct area,understanding of flows and pressure drop through the systemis essential. Computational Fluid Dynamics (CFD) isconsidered to be the most cost effective solution for flowanalysis of intake system along with filter media. This paperfocuses on the optimization of the 1.6L engine air intakesystem and, with and without guide vane placement on thefilter duct media by CFD analysis results.The geometry of the intake’s optimum performance isrelated to what is generally well known as a loss coefficient,typically identified by K , which represents the fraction ofthe dynamic head lost in the duct. This loss can be easilycorrected or compensated for by proper design of the inletduct [3]. Another phenomena is the s-duct flow, the flow insuch as diffusing s-ducts Fig. 1is complex in nature due toeffects arising from the offset between the intake plane andengine face plane. As the flow moves on through the duct itwould perhaps be expected that a similar motion in theopposite sense be initiated at the second bend. However bythis stage the low energy flow is largely on the outside wallrelative to the second bend and is not driven backcircumferentially [4].One of the most significant drawbacks of such geometry isthe appearance of a separated boundary layer located in thecurve, which causes decrease of the total pressure of the gasentering the system. Moreover, the strong curve isresponsible for the development of a secondary flowcomposing of counter rotating vortices and responsible forflow distortions. Both aspects significantly degrade theperformance of the system. Consequently, it is highlydesirable to avoid the boundary layer separation [5].IMECS 2010

Proceedings of the International MultiConference of Engineers and Computer Scientists 2010 Vol II,IMECS 2010, March 17 - 19, 2010, Hong KongConsidering the CFD analysis a CAD model is developed andmimicking the actual parts in the AIS. Fig. 4 shows theexploded view of the AIS in CAD.Fig. 1 Diffusing s-ducts with guide vane [4]A research shows that the design of guide vanes for use inexpanding bends was investigated both experimentally andnumerically. The primary application in mind is the use ofexpanding corners in wind-tunnels for the purpose ofconstructing compact circuits with low losses. Theexperimental results demonstrated that a suitably designedguide vanes give very low losses and retained flow qualityeven for quite substantial expansion ratios [6].Fig. 4 CAD model of AISII. MODELINGFig. 2 and Fig. 3 shows the model of intake system andfilter. In order to save the CFD computational time and cost,trivial geometric details that are not important from fluid flowpoint of view, such as fillets, blends stiffeners and steps areavoided in the model. All the above-mentioned, so called acleaned geometry was obtained from solid model. Themodeled AIS is assumed to be driven under standardenvironmental condition neglecting altitude changes.CFD is a computerized method that is widely used in thecar industry to study e.g. the aerodynamics of a car andcombustion processes but is also applicable in otherindustries such as the nuclear power and pharmaceuticalindustry. It divides the computational domain into smallcontrol volumes, known as cells and in these cells all theequations that described the flow field of interest aresolved and explanation about flow around the car body.Together with predetermined values at the boundaries orinitial conditions the equations in the cells are solved [7] [8].Fig. 2 Existing model of AIS proton Waja 1.6III. METHODOLOGYAir was used as fluid media, which was assumed to be steadyand incompressible. High Reynolds number k-ε turbulencemodel was used in the CFD model. CFD generally solvesfluid motion by solving the Navier-Stokes equation of mass,momentum and energy equation. The three equations can bewritten in the conservation form as follows: ρ ( ρu k ) 0 t x k ρui (ρuiuk τ ik ) P Si y xk xi (ρE ) ((ρE P )u k qk τ ik ui ) S k u k QH y x k(1)(2)(3)where u is the fluid velocity, ρ is the fluid density, Si is amass-distributed external force per unit mass, E is the totalenergy per unit mass, QH is a heat source per unit volume,τ ik is the viscous shear stress tensor and qi is the diffusiveheat flux.This turbulence model is widely used in industrialapplications. The equations of mass and momentum weresolved using SIMPLE algorithm to get velocity and pressurein the fluid domain. The assumption of an isotropicturbulence field used in this turbulence model was valid forthe current application. The near-wall cell thickness wascalculated to satisfy the logarithmic law of the wall boundary.Other fluid properties were taken as constants. Filter bedmedia of intake system were modeled as porous media usingcoefficients. For porous media, it is assumed that, within thevolume containing the distributed resistance, there exists alocal balance everywhere between pressure and resistanceforces such that the porosity were defined as 85%. Fig. 5shows the CFD model of the AIS system.Fig. 3 AIS located under the bonnet of Waja 1.6ISBN: 978-988-18210-4-1ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online)IMECS 2010

Proceedings of the International MultiConference of Engineers and Computer Scientists 2010 Vol II,IMECS 2010, March 17 - 19, 2010, Hong KongWhere,ܸ is the required engine air flowrate, mଷ / secη is the engine volumetric efficiency (assumed 85% fornormal engine specification)N is engine speed, rpmDiis engine displacement, mଷFig. 5 AIS in CFD modelIt is evident that from the optimal design of engine intakeextensions that the intake, when incorporated as an integralpart, would not be of conventional design but contains thenecessary inlet air vanes to approach optimum air flow. Theactual bend and internal vane settings would be optimizedusing computer software to obtain the maximum uniformflow and minimize the value of KL. The most commonmethod used to determine these head losses or pressure dropsis to specify the loss coefficient, K which is defined as [23]:ଶ ܭ ℎ . మ ௱ భఘ మమ(4)A guide-vane section was designed with the aim ofminimizing the pressure drop for flow in a 90-deg corner. Acentral part of the design process was to use potential flowcalculations in order to obtain vane geometry such that thevelocity distribution on the suction side replicates that of achosen single airfoil at the angle of attack for maximumlift/drag in a straight free stream. The choice was based onproven good drag characteristics at low Reynolds numbers.For the design of the pressure-side velocity, distributionadvantage of the expansion in the middle part of the cascadewas taken to obtain a high pressure coefficient on thepressure side, as compared to the single airfoil case [9]. Fig. 5shows the guide vane design implemented in the AIS as thepaper examines the flow in a diffusing shaped Proton Wajaair intake using computational fluid dynamics (CFD)simulations.Fig. 6 Mesh analysis for AIS with guide vaneFig. 7 Mesh analysis for AIS without guide vaneThe mesh analysis shows top view of the AIS. The analysis isto do the improvement on the existing model as in Fig. 6.After the improvement was the done to capture the flowinside the system, the mesh of the final CFD analysis of theAIS is as in Fig. 7. The improvement mesh captures moreaccurately the presence of air at the guide vane wall surface.IV. RESULTSThe results are compared for condition of no guide vaneand with the guide vane attached. The first being the pressuredrop as shown in Table 1.Fig. 5 Placement of guide vane in optimized designThe air flowrate required, Vୟ can be calculated fromequation below for the particular engine speed if the enginedisplacement is known.ܸ ఎೇ ே ଶ(݉ଷ / )ݏ ISBN: 978-988-18210-4-1ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online)(5)IMECS 2010