Automotive Systems Engineering - Assignment Example

Name Tutor Course Date Part 1 Section One a) Internal Gas Flows – 800 Internal gas flows of an engine is measured using an apparatus called a bench. The device enables the testing of the internal aerodynamic qualities of a particular engine and related to wind channels. It is used majorly for carrying out tests on exhaust ports of cylinder heads in internal combustion engines. Design of Apparatus The apparatus needed for the experiment are as shown: Test pressure manometer Metering elements Burner Test plenum Pump Design of Air pump The air pump used in the experiment should have the capacity to deliver the air volume that is needed at the required pressure. Pump pressure capacity – 2.5 to 7 kilopascals. The pressure developed should cover for the test pressure as well as all the other system pressure. However, any pump that can deliver the required pressure difference as well as volume flow can be used. Design of metering element Several metering elements exist and generally all the types can deliver similar accuracy. Since the test is considered as commercial, orifice plates would be the best due to their simple construction and their ability to provide multiple flow ranges. EXPERIMENT Fundamentals of experiment setup The test piece is always attached in series with a pump and a measuring element. Air is then pumped throughout the whole system. Therefore, all the air going through the metering element has to go through the test piece too. Measurement of airflow is done at two points; across the metering element and across the test piece. Measurement of pressure across the test piece is accomplished by the u-tube manometer placed in the set up. The apparatus were set up as shown below in Fig 1.1 Fig 1.1 Experimental setup DATA COLECTION Before the experiment, basic measurement of the apparatus dimension is done. Such measurements include: the depth of the adaptor, the diameter of the adaptor, the overall diameter of the valve and the seat angles for valves with angles 30°, 45° and 60°. Volume of air passing through the port is measures at intervals of time and the values obtained expressed in cubic meters per second or per minute (M3/s). Valve is measured in actual dimension preferably in millimeters. The value can alternatively be expressed as a ration of Lift to characteristic diameter. The ration in engine normally takes values between 0.05 and 0.30Using the values of seat angle values and their corresponding w values for the various tubes used in the experiments. Using the dimensions of the figures shown below, the following data is obtained. Seat Angle W 60° 1.32 45° 3.65 30° 6.25 Table 1.1 Values of seat angles with respective values of w The parameters of the engine used in the experiments were as follows: Depth of adaptor 90.5mm Diameter of adaptor 83.5mm Overall diameter of valve 32.0mm Interpretation of results Interpretation of data obtained from the experiment is done by either suing numerical analysis of graphical analysis. However, numerical analysis as well as graphical analysis will be carried out in this case in for the learner to make comparison. Numerical analysis Numerical analysis involves the mathematical calculation and interpretation of the results obtained. a) Mean gas velocity across the annulus Using the following gas flow equation V (m/s) = L.N/30000(D/d)2………………………………………(I) For convenience purposes, the speed is converted into Revolutions per second. N (rps) = N/60 And substituting the value of N (rps) into equation (I) for the various revolutions, we obtain the following results. i. 1500 RP/M Revolutions per second N = 1500/60 = 25 rps V (m/s) = 90.5 x 10-3 x 25/ [30000(83.5/32)²] m/s, therefore the velocity in m/s is given as, V = 4.43 x 10-7 m/s ii. 2500 RP/M Revolutions per second N =2500/60 rps = 41.67 rps V (m/s) = 90.5 x 10-3 x 41.67/ [30000(83.5/32)²] m/s therefore the velocity in m/s is given as, V = 1.85 x 10-5 m/s iii. 3500 RP/M Revolutions per second N =3500/60 rps = 58.33 rps V (m/s) = 90.5 x 10-3 x 58.33/ [30000(83.5/32)²] m/s therefore the velocity in m/s is given as, V = 2.585 x 10-5 m/s iv. 4000 RP/M Revolutions per second N =4000/60 rps = 66.67 rps V (m/s) = 90.5 x 10-3 x 66.67/ [30000(83.5/32)²] m/s therefore the velocity in m/s is given as, V = 2.95 x 10-5 m/s Graphical analysis Using the mean gas velocity values calculated and tabulated in table 1.2, a graphical representation of the data can be obtained by drawing a line graph as shown below. Shape and flow area The graphical representation of the shape and position of the flow area are as shown. Conclusion From the values of mean gas velocity calculated, it was found that the mean gas velocity through the annulus increased as the speed of engine rotation increased. Therefore, the engine rotation is directly proportional to the mean gas velocity. It therefore means that, an increase in the speed of the engine has an effect on the torque experienced by the engine. Areas of optimization Optimization of the torque of the engine is very important in engine design. It determines the acceleration capacity of an engine. Volumetric efficiency is another field that requires major optimization. Optimization of volumetric efficiency determines the torque output. The seat angle valves are two way pistons with pneumatically actuated valves and are majorly used for gases, steam liquids and other fluids. However its piston design is of a very unique nature. It has the ability to retract the plug far away from the path way. Part 1 (b) Literature review Optimization of an internal combustion engine The rising cost of petroleum based fuels and the strict environmental regulations that restricts the amount of exhaust emissions allowed into the atmosphere have increased the need for an alternative fuel in automobile engines. Evidently, vehicles using natural gas as fuel have a higher potential to achieving higher thermal efficiency, less knocking chances and minimized carbon emissions. Research work indicates that when the pressure drop is decreased, air freely moves to the engine (Ahmadi, 2007). This therefore, means that, more air and fuel mixture gets into the engine and this generates more power and efficiency in the engine. There is a big pressure difference between guided vane air intake system and the non-guided vane pressure intake system. Analysis of the two systems has shown that, the pressure system without the guided vane experiences pressure losses along the intake right back walls of AIS. Analysis in the AIS with guided vane reveals that pressure loss experienced by AIS is reduced. Investigations on the runners have revealed that, increase in length of a runner to over twenty percent of the initial value, volumetric efficiency increases drastically. Optimization of an internal combustion engine tract is a process that a lot of attention and care during the design stage of the engine. It requires the design to be made specifically for maximum torque. The objective of optimization is, therefore, achieved when a flat torque curve is obtained when a range of RPM values are plotted as shown below. It has been estimated by experiments that proper improvements of the guided vanes has improved the overall pressure drop by approximately twelve percent for speeds of up to seven thousands rotations per minute (7000Rpm) (Pai, D.B, and P.V.F, 2011). Use of more guided vanes on critical points have been proved to improve the performance of the system even further. Optimization of volumetric analysis is another powerful method of evaluating an intake manifold performance. When analysis is done by use of both steady and unsteady simultaneous results suggest improvement of the performance of manifold. Design and optimization can therefore be achieved by using 3-D simulation which is one of the most powerful tools for such purposes. This therefore means that such a model cannot be employed in the calculations as oposed to accuracy since at high speeds, it is considered eronious especially at higher speeds During development of engines, there some issues that are put into consideration.Such include, fuel consumption by the engine and the provision for improvement of the engine. In order for the engine developers to improve the performance of the engine, a very critical consideration is the increase of the combustion efficiency of the engine within the cylinder chamber. This therefore necesitates for analysis of the mass flow rate and the swirl strength. Under normal circumstances, swirl strenght is achieved by applying a system of port deactivators into the manifold intake. This is done within the cylinder chamber both in low speed range and medium speed range. The swirl helps in in improving the fuel’s mixing effect together with the air within the cylinder chamber. With the application of the system of port de-activate, the volumetric efficiency of the system worsens because of the decrease in the mass flow rate. For CNG fueled engines, most of their engines are not yet optimized (Safari and A, 2007). Therefore, optimization of such engines requires some special modification such as ensuring a high compression ratio in the engine. Advanced ignition timing also goes a long way to ensuring an optimized perfomance of CNG fueled engines. Other conditions used in such optimization include modifications in supercharge or even turbo charge conditions, suitable air fuel ration as well as effective intake valve close timing. Research work has indicated that the initial design of the intake manifulds did not have the capabilities to check and regulate the increase in pressure waves.the manifolds do not provide a uniform air distribution to all the cylinders (Erjavec, 2010). Such engines potrayed emmision of large quantities of smoke and thus rendered the perfomance of the engine as poor. Development of optimized Intake manifolds were achieved by use of CFD software. The manifold is then experimentally tested by observing over seventy six parcent mass fraction of air for all the runners at speeds of 1800rpm. Further experiments on the air pressure inside the runners has revealed that the flow of air for the optimized intake manifold has increased. In roder to test the adequate design a manifold, two manifold shapes are used where the first one is an un-specified design while the other one is designed with consideration of the accoustic wave filling concept (Vaughan and G.J., 2010). In first design of the manifold, the results from the experimental proceedures carried out reveal that manifold mixture velocity is approximately 70m/s and decrease below 16m/s. however, in the second manifold, mixture velocity passing through the valve is found to be approximately 81m/s and the decrease recorded is less than 25m/s. The difference between the two design so of the manifold reveals the difference in the manifolds geometry has a greater influence in mixture velocity. A velocity discontinuity is noticed in the runner belong to the second manifold. Such velocity discontinuities is thought to have originated from the various dead zones present in the geometry of the runner. Experiments to determine the influence of intake manifold on the engine perfomance revealed that, in the optimized manifolds, air ratio as well as specific consumption of fuel are improved by twenty eight parcent and ten parcent respectively. Conclusion The primary use of the intake manifold is to equally distribute combustion mixture to all of the intake ports in the cylinder heads. The most effective intake manifold has the ability to uncertain even distribution of flow to the piston valves.even distribution helps in optimizing the perfomance and even the efficiency of the engine. The inlet manifold design has a great impact on the volumetric efficiency of an engine. Therefore, unequal distribution of air will always result in less volumetric efficiency in the engine. Uneven air distribution leads to less volumetric efficiency, increased fuel consumption as well as eminent powerloss. Therefore, efforts to design intake manifolds to ensure even distribution of air and fuel mixture and consequently increase velocity and volumetric efficiency are currently ongoing. Such effort will ensure the design of the most optimized engined with very high perfomance. Section 2 Chasis analytical design Considering the chais design shown below: And the chasys information given below Mass of the vehicle = 1519.4 Kg Wheel base (L)(LWB) = 2.315m Height of centre of gravity (h) = 0.285m Height of centre of draft force (H) = 0.7m Air density (ρ) = 1.225kg/m3 Velocity of the car (V) = 120km/h Projected frontal area (A) = 1.29m2 Coeffiecient of lift (CL) = 0.6 Coefficient od drag (CD) = 0.31 Coefficient of pitching moment (CPM) = 0.04 Coefficient of rolling moment (CRM) = 0.020 Coefficient of yawing moment (CYM) = 0.180 Coefficient of side force (CS) = 0.02 From the above information, the following analytical calculations can be done: a) Pitch moments The pitch moments can be calculated from the following expression. ………………..(ii) i) The pitch moment across each wheel is given by: Pitch moment = ½ x ρ x V2 x CPM x LWB Fro purposes of convinienccy, the velocity of the car is converted to M/S Therefore Speed (V) = (120Km/hr x 1000)/3600 Therefore speed = 33.33m/s Pitch moments = ½ x 1.225kg/m3 x (33.33m/s)2 x 0.04 x 2.315m Pitch moments = 63.0194 Kg.m2 ii) Pitch moments across the axle: Pitch moment = ½ x ρ x V2 x h x CPM Therefore pitch moment = ½ x 1.225 x 33.332 x 0.285 x 0.04 Pitch moments = 7.7567 Kg.m2 Pitching moments affects the rotation of the trailer while turning. Therefore during the design of the chasis, consideration should be taken to make wheels that can accommodate the pitching moments of the chasis. b) Rolling moments i) Rolling moments due to each wheel Rolling moments is given by the expression shown below: Therefore subtituting the given parameters: Rolling moment = ½ x 1.225 x 33.332 x 1.29 x 0.020 x 2.315 Thus Rolling moment = 40.639 Kg.m2 ii) Rolling moments due to the axle The rolling moment due to the axle is give by the following expression Rolling moment = ½ x ρ x v2 x A x CRM x h By subtituting the parameters given in the expression, we find that: Rolling momment = ½ x 1.225 x 33.332 x 1.29 x 0.020 x 0.285 Rolling momment = 5.003 Kg.m2 The rolling moments of the chasis obtained means that, the appropriate steering offset should be considered to counterract the effect of the rolling forces. c) Yawing moments i) Yawing moments due to each wheel The yawing moments due to each wheel is given by the expression shown below. Therefore, by subtituting the given parameters into the equation, we get: Yawing moments = ½ x 1.225 x 33.332 x 1.29 x 0.180 x 2.315 Yawing momments = 365.7547 Kg.m2 ii) Yawing moments due to the axle The yawing moments due to the axle is given by the expression shown: Yawing moment = ½ x ρ x v2 x A x CYM x h Therefore, by subtituting the parameters, the calculated value of yawing moment is found to be; Yawing moment = ½ x 1.225 x 33.332 x 1.29 x 0.180 x 0.285 Yawing moments = 45.028 Kg.m2 The yawing moments on the wheels cen be reduced by using two separate ABS systems at the front axle. This will ensure that at the worst condition, the wheels does not lock due to braking force or decrease of yawing moment. Generic chasis forces The generic chasis forces can be calculated as follows. i) Drag Drag is give by the following expression: Subtituting the parameters given, the value of drag on the chasis is found as follows; Drag = ½ x 1.225 x 33.332 x 1.29 x 0.31 Drag = 272.10 N Increase in drag force can result in stability during high speeds therefore, this effect must be put into consideration during design of the chasis. ii) Lift lift is calculated using the following expression; Therefore Lift = ½ x 1.225 x 33.332 x 1.29 x 0.6 Lift = 526.64 N The values of lift force is related to the generation of draft force and the two must always be considered during design to ensure stability of the chasis. iii) Side force The side force is found by use of the equation shown below. Thus side force = ½ x 1.225 x33.332 x 1.29 x 0.6 x 0.02 Side force = 10.5 N The amount of side force developed depends on the amount of side slip of the chasis. Therefore, during design, the required or the most appropriate side force may be obtained by using the most effective side angle. iv) Pitching moments The pitching moments for the chasis will be given by Pitching moment = ½ x ρ x V2 x A x CPM x H Pitching momment = ½ x 1.225 x 33.332 x 1.29 x 0.04 x 0.7 Pitching momment = 24.577 Kg.m2 v) Rolling momments The rolling momments for the chassis can be calculated as, Rolling momments = ½ x ρ x V2 x A x CRM x H Rolling momments = ½ x 1.225 x 33.332 x 1.29 x 0.020 x 0.7 Rolling momments = 12.288 Kg.m2 vi) Yawing momments Yawing momments = ½ x ρ x V2 x A x CYM x H Yawing moments = ½ x 1.225 x 33.332 x 0.18 x 0.7 Yawing moments = 85.73 Kg.m2 vii) Drag powerloss Drag powerloss = 272.10 x 33.33 Drag powerloss = 9,069.093 Joules or 9.069 Kilo Watts The amount of drag force experienced by the chasis determines the amount of powerloss due to drag force. viii) Down force Down force = 272.10 x 0.285 Down force = 77.55 N The heigh of centre f gravity, or generally the heigh of the vehicle determines the down force experienced. The down force on the other hand determines the stability of the chasis. Therefore during design, both measurements must be put into considerations. References Top of Form Bottom of Form Top of Form Bottom of Form Top of Form Bottom of Form Top of Form Bottom of Form Top of Form Bottom of Form Top of Form Bottom of Form Ahmadi, Mahdi. Intake, Exhaust and Valve Timing Design Using Single and Multi Objective Genetic Algorithm. Warrendale, Pa: SAE International, 2007. Print. Erjavec, Jack. Automotive Technology: A Systems Approach. Australia: Delmar Cengage Learning, 2010. Print. Pai, D.B, H.S Singh, and P.V.F Muhammed. "Simulation Based Approach for Optimization of Intake Manifold." Sae Technical Papers. (2011). Print. Safari, M, M Ghamari, and A Nasiritosi. Intake Manifold Optimization by Using 3-D Cfd Analysis. Madison, Wis: SAE International, 2003. Print. Vaughan, A, and G.J Delagrammatikas. "Variable Runner Length Intake Manifold Design: an Interim Progress Report." Sae Technical Papers. (2010). Print. Read More