Simulation of Jacket Cooling of a Liner of Four Cylinder Diesel Engine for Genset Application

Transcription

1 Simulation of Jacket Cooling of a Liner of Four Cylinder Diesel Engine for Genset Application #1 Mr. Ankit P. Shingare, #2 Prof. Nilesh B. Totla #1 Mr. Ankit P. Shingare, MIT Academy of Engineering, Savitribai Phule Pune University, Pune, Maharashtra, India #2 Prof. Nilesh B. Totla, MIT Academy of Engineering, Savitribai Phule Pune University, Pune, Maharashtra, India Abstract With increasing computational power of modern computers, multi-dimensional Computational Fluid Dynamics (CFD) has found more and more applications in diesel engine research, design and development. Various successful applications have proven the reliability of using multi-dimensional CFD tools to assist in diesel engine research, design and development. By using CFD tools effectively it is easy to predict and analyses various details that are technically difficult like in cylinder process of diesel combustion, temperature and pressure contours, emission, coolant etc prior to experimental tests to reduce the number of investigated parameters as well as time and thus costs. A multidimensional model was created and analysis of combustion and coolant was done using FLUENT, ANSYS 14.1 package and the 2D geometry was modelled and meshed using ICEM.A full scale diesel engine has been imported in to the CFD tool to analyze the temperature distribution of coolant throughout the cooling channels. The fluent approach solver has been adopted to solve the energy equations along with the realizable k-ɛ two-layer turbulence model to find out accordance with the available theoretical and experimental results. The input values are collected from combustion analysis of same engine and from available documents, too. The main objective of the analysis was to reduce the temperature gradient along liner from coolant side which would bring more uniform cooling, reduction of liner distortion and reduction of liner pitting. Keywords:CI engine heat transfer, Coolant temperature, Steady state heat transfer, CFD, Segregated approach. 1. Introduction Computational Fluid Dynamics (CFD) is the use of computer-based simulation to analysis systems involving fluid flow, heat transfer and associated phenomena such as chemical reaction. A numerical model is first constructed using a set of mathematical equations that describe the flow. These equations are then solved using a computer program in order to obtain the flow variables throughout the flow domain. Since the advent of the digital computer, CFD has received extensive attention and has been widely used to study various aspects of fluid dynamics. The development and application of CFD have undergone considerable growth, and as a result it has become a powerful tool in the design and analysis of engineering and other processes. In the early 1980s, computers became sufficiently powerful for general-purpose CFD software to become available. 1.2 CFD Procedure All commercial CFD packages involve sophisticated user interfaces to input parameters and to examine the results. Hence all the codes consist of three main elements: Pre-processor Solver Post-processor 1. Pre-processingis the input of a flow problem to a CFD program by means of an operator friendly interface and the subsequent transformation of this input into a form suitable for use by the solver. The steps involved in this are: Definition of geometry. Grid generation. Selection of the phenomena or system to be modelled. Definition of fluid properties. Boundary conditions specification. 2. Solver involves the following steps: Approximation of the unknown flow variables by means of simple functions. Discretization by substitution of the approximations into the governing flow equations. Solution of algebraic equations.

2 3. Post-processor- All the leading CFD packages are equipped with versatile data visualization Tools. These include: - Domain geometry and grid display Vector plots Line and shaded contour plots Color postscript output The mathematical modelling of a flow problem is achieved basically through three steps: Developing the governing equations describing the flow Discretization of the governing equations solving the resulting numerical equations. 1.3 Governing Equations: Unsteady state 3-D equation of continuity: - Where ρ is the fluid density, t is time, and u is velocity. Momentum equation: - Where P is pressure, μ is fluid viscosity, x is the coordinate and the subscript indicates The Cartesian coordinates. Energy equation: Where k is the thermal conductivity, T is the temperature, is the dissipation term and S is the source term. 2. Literature Review The project aims at finding the optimum characteristic of the coolant using CFD analysis. In this project an attempt has been made to study the variations in the properties of the coolant mixture by varying their composition. During literature review in one of the case study found some of the similar examples in those literature materials quite similar to the analysisin my project. Reduced fuel consumption and improved efficiency are always the primary area of consideration in internal combustion engine design sector. They were generally done by building prototypes and testing them. But this traditional process always had several limitations. They were time consuming, cost consuming and also a prototype made for a single purpose didn't had the complete versatility of using the same for other purpose. This difficulty can be overcome by using CFD studies. With the increasing advancement in computational power of modern computers, CFD has found its application in diesel combustion. This is now widely used by many automobile industries not only for design and analysis of engine but also for the whole vehicle analysis. Of the many types of models for engine combustion process, multidimensional computational fluid dynamics (CFD) models is gaining momentum due to its capability to predict the gas flow patterns, fuel spray structure, coolant behavior in the heat exchanger systems [1]. The basic approach of in-cylinder diesel combustion models is typically compressible turbulent flow. Apart from the complexity of turbulent model, the high pressure spray and resulting spray penetration, evaporation, and involvement of multiphase, multicomponent nature only increases its complexity. Even then the nature of fluid is still governed by the basic equations including continuity (mass conservation), momentum (Navier-Stokes equation), energy and turbulence (k-ε model) equations [4]. Of the three combustion modelling (thermodynamic, multidimensional and phenomenological modelling), the software uses multidimensional. In the above analysis CFD analysis has been done using k -ε model. The CFD analysis is done using three models like Spalart Allmaras, Standard k ε, RNG k ε, Realizable k ε, Standard k ω, SST k ω and Reynolds Stress [3].Out of the above models Realizable k ε is most relevant for the analysis of this project. As explained earlier the CFD analysis in the above example was quite useful for this project analysis [1]. By considering above information,we found that CFD analysis is suitable for present work. In one of the literature studied a full scale SI engine had been imported in to the CFD tool to analyse the temperature distribution of coolant throughout the cooling channels. The main objective of the analysis was to observe the coolant temperature distribution inside the cooling jacket when the engine is turned off. The steady state simulation shows that though the average coolant outlet temperature is found within the acceptable limit of cooling system operation principle, there is a large temperature gradient in fluid thermal boundary layers within cross section and overall jacket path. The analysis demands that there should be some special arrangement of maintaining the fluid flow inside the cooling jacket even after the engine is turned off to avoid further loss of the engine body due to high temperature accumulation inside the cooling jacket and fluid in it [2]. Similarly, IC engine is an important prime mover used in various fields mainly in automotive and power generation. In early days of IC engine development, power output and efficiency were the main focus of researchers. Heat in commercial diesel engine has to travel through engine components leading to increase in its temperature. This percentage of heat loss through engine cooling varies according to various engine and cooling system parameters. In this study, for one single head of diesel engine, three-dimensional coolant flow inside cooling water jacket is simulated using 3D CFD software. Some estimating study is developed, including whether cooling water system capacity for

3 cylinder head is good enough or not, the distribution of coolant to cylinder is even or not and so on. Finally, some advices are put forward, which can provide gist for optimizing the diesel engine. The methodology presented in this paper is based on CFD and validation is done experimentation in which sensor were used. The CFD analyses constitute the first step of the proposed modelling strategy. Two different aspect are investigated in detail: i) the fluid-dynamic behaviour of the cooling circuit is firstly analysed and optimized aiming at improving the cooling efficiency ii) the point-wise fluid/solid heat transfer is then evaluated. In particular, benefits on the overall predicting capability brought in by the adoption of a proper phase-change model are highlighted by means of a preliminary comparison with a simplified model and by a subsequent validation of the methodology against experimental measurements of the temperature distribution within the engine head. Thus in present study 4-cylinder, 4-stroke 4-valve, turbo after-cooled, high pressure diesel engine is selected. Initially geometrical layout will be studied in terms of flow and heat transfer analysis by using CFD as a tool. The parametric study of an IC engine cooling jacket will be carried out using experimentations and results will be used to comment on effectiveness of selected parameters and optimizing these parameters by using statistical methods [2]. Similar methodology is adopted in this work. 3. Objectives and Scope The set objectives of the project can be enumerated as follows, i) Achievement of uniformity in jacket cooling. ii) Reduction of liner distortion. For above points, determination of interdependence of process parameters on cylinder liner temperature gradient from coolant side is done by experimentation. Here process parameters that are taken for research includes: heat flux going to cylinder liner, flow velocity of coolant, coolant mixture fraction.i.e. = iii) Reduction of liner pitting phenomenon iv) Compare the temperature gradient of 45 different readings of coolant mixture and obtained the minimum of them for getting maximum coolant rate. The selected engine Is-Engine -125 KVA Genset application, 4-cylinder diesel engine Sr.No. Parameter Value 1. Crank radius 65 mm 2 Connecting rod 207 mm 3 Bore diameter 105 mm 3. Stroke 130 mm Table 1.Engine Parameter 4. Coolant gallery 4.1 Estimation of properties of selected coolant mixture fractions: Sr. No % Glycol % Water Table 2. The selected coolant mixture fractions Table 3, Table 4 and Table 5 The above selected coolant mixture fractions were sent to Laboratory for determination of thermal properties. The details of properties are: Sr. No Mixture Density at Density Density at fraction 27.6 C 93 C 78 C % % (kg/m Water Glycol 3 ) (kg/m 3 ) (kg/m 3 ) Table 3. Density of coolant mixture fractions

4 Sr. Mixture Dynamic Dynamic Dynamic No fraction viscosity viscosity atviscosity at 27.6 deg. 93 deg.78 deg. % % Water Glycol centipoises centipoises centipoises Table 4.Viscosity of coolant mixture fractions Sr.No. Mixture Specific Specific Specific fraction heat at heat at heat at % % 27.6 Deg 93 Deg 78Deg Water Glycol (kj/kg (kj/kg (kj/kg K) K) K) Table 5.Specific Heat of coolant mixture fractions Sr.No. Mixture Mass flow rate in kg/sec fraction % % 40 LPM 37.5 LPM 35 LPM Water Glycol Sr.No. Parameter Value/Details 1 Crank Shaft speed 1500 RPM 2 Crank rotation period Crank radius 65mm 4 Connecting rod length 207 mm 5 Bore 105 mm 6 Stroke 130 mm Table 7. Engine specification GEOMETRY PREPARATION As the piston and combustion chamber space is symmetrical about axis, hence sector geometry of the combustion space was decided to be drafted. Fig.1 Catia drawing of combustion chamber MESHING Geometry was imported in the mesh modular.here both structured and unstructured meshes are used. Structured mesh is quadrilateral and hexagonal shape. Unstructured mesh is triangular 5. CFD ANALYSIS Table 6.Various Mass Flow Rate Calculated 5.1 Combustion Analysis The inbuilt ICE system of ANSYS workbench has been employed for combustion simulation. The In-Cylinder Combustion Simulation type is used here. Combustion simulation involves simulation of the power stroke during the engine cycle, starting from closing of valves to the end of the compression stroke. Fig.2 Meshing of combustion chamber FLUENT SOLVER Fluent is solver used for analysis of combustion chamber. Fluent is finite volume based solver.

5 Sr.No. Type of input Details/Values/Selection 1 Solution Type Combustion Simulation Geometry Preparation Solution. 2 Simulation type Sector Simulation 3 Initialization(Yes/No) Yes 4 Report Mesh Allowed (Allowed /Not allowed) 5 Model Selection K- (k-epsilon)model. 6 Data sampling Yes. allowed(yes/no) 7 Auto save type Crank angle 8 Auto save frequency Every 10 crank angle. 9 No. of crank angle to 180 run. 10 Swirl no. 2.1 Table 8. Boundary Condition CFD POST-Results Meshing Fig.4 Catia drawing of coolant half view Drafted geometry was imported in the mesh modular. Here both structured and unstructured meshes are used. Structured mesh is quadrilateral and hexagonal shape. Unstructured mesh is triangular. [Fig.2] Fig.5 mesh of coolant geometry Fig.3 At 360 crank angle Temperature distribution 5.2 Coolant Gallery Analysis As the GENSET engine have four-cylinder piston arrangement and having coolant gallery which is symmetrical to every cylinder, our main motive is to calculate the temperature variation at single cylinder through which our coolant is entering coolant space which is symmetrical about axis. For this the sector geometry of the coolant space was decided to be drafted.here the coolant space is drafted. It consists liner part at one side and coolant wall at another side. Included angle is of [Fig.1] Fluent Solver Boundary Condition for Coolant flow simulation are as follows

6 Sr.No. Type of input Details/Values/Selection 1 Solution SIMPLE Method 2 Spatial Second Order Discretization 3 Inside temp Combustion result 4 Inlet Mass flow rate 5 Outlet Pressure outlet Fig mixture fraction for 35 LPM 6. Model K-epsilon (2 eq.) Selection Realizable 7. Energy On Equation Table 9. Boundary Condition 6. Results and discussion All calculated values are observed in CFD post processing.results of liner with different flow rate having different mixture fraction is obtained and the fluent solver diagrams are shown below. Fig mixture fraction for 30 LPM Fig mixture fraction for 45 LPM Fig mixture fraction for 40 LPM Various graphs are obtained for above results. The graphs having x-axis as temperature in K and y-axis as length of linear in mm X-axis-1 unit=5 K Y-axis-1 unit=5 mm Blue line represents mixture flow rate Red line represents mixture flow rate Yellow line represents mixture flow rate Fig mixture fraction for 37.5 LPM

7 Fig.11 Graph of 35LPM for different mixture fraction Fig.15 Graph of 45 LPM for different mixture fraction Conclusion The analysis of combustion temp is carried out by using CFD tool. The obtained results are used as input value for further coolant flow analysis. Fig.12 Graph of 37.5LPM for different mixture fraction Fig.13 Graph of 40 LPM for different mixture fraction Fig.14 Graph of 30 LPM for different mixture fraction The Analysis work carried out in this study and the conclusion made from above discussed are as follow Analysis of three different mixture fraction has been done with five different LPM. Hence total fifteen ANSYS simulation diagrams and five graphs are obtained. Theabove graphs are represented the maximum temperature in mixture fraction and lesser in mixture fraction In graph 30 LPM the maximum temperature obtained is389 K and minimum temperature obtained is 326 K. In graph 35 LPM the maximum temperature obtained is K and minimum temperature obtained is K. In graph 37.5 LPM the maximum temperature obtained is K and minimum temperature obtained is K. In graph 40 LPM the maximum temperature obtained is K and minimum temperature obtained is K. In graph 45 LPM the maximum temperature obtained is379 K and minimum temperature obtained is K. It is observed that the temperature from gas side of the liner to the coolant side of the liner decreases to certain level after coolant gallery the temperature also reduces. Because the coolant mixture used i.e. water glycol take heat from liner coolant side and liberated outside. The material used cast iron for liner also transfers heat. The model used k-epsilon standard is good for convergence and to capture thermal boundary layer inside the coolant gallery. Grid independence is used for better accuracy.

8 At TDC after combustion at 364 degrees we get the maximum temperature inside the combustion chamber which we propagate along the liner in a vertical direction. The obtained temperature value along liner is simulated in ANSYS CFD. References [1.] Journal of Engineering Research and Applications (IJERA) ISSN: Vol. 3, Issue 4, Jul-Aug 2013, pp [2.] Amit V. Paratwar, D.B Hulwan / International Journal of Engineering Research and Applications (IJERA) ISSN: Vol. 3, Issue 4, Jul-Aug 2013, pp [3.] Allen, D., Hnatczuk, W., Lasecki, M. and Chalgren, R Advanced thermal management for military application Air Condition, Heating, Lighting and Ventilating. Defense technical information center. [4.] Piccione, R. and Sergio., B Engine rapid shutdown: Experimental investigation on the cooling system transient response. ASME Journal of Engineering for Gas Turbines and Power 132 (7): [5.] Rohsenow, W.M. and Griffith, P Correlation of maximum heat flux data for boiling of saturated liquids, Technical report (Massachusetts Institute of Technology, Heat Transfer Laboratory). [6.] Ariz Ahmad,(2014), Analysis of Combustion Chambers in Internal Combustion Engine,Gobal Science and Technology Journal, Vol 2, No 1,PP [7.] john J. Truhana,JunQu b, Peter J. Blaub,(2005), A rig test to measure friction and wear of heavy duty diesel engine piston rings and cylinder liners using realistic lubricants,tribologyinternational,vol 38, PP [8.] DivyanshuPurohit, Pragya Mishra, VishwanathBanska Flow Simulation of an I.C. Engine in FLUENT, ANSYS14.0 International Journal of Engineering Research and Applications International Conference on Emerging Trends in Mechanical and Electrical Engineering(ICETMEE),13th- 14th March [9.] Tutorial Manual Guide, Combustion Engine ANSYS Mesh Tutorial. [10.] Gataowski, J.A., 'Evaluation of a Selectively Cooled Single Cylinder 0.5L Diesel Engine", SAE, Paper , USA, 1990.