Designing camshaft of Mechanical Continuously Variable value Timing (CVVT) mchanism

Abstract

In Recent Years, Co2 Emission From Conventional Fuel Powered Vehicles Has Become The Major Contributor To The Overall Global Warming Effect Around The Planet. Also, Fuel Prices Have Risen Considerably Due To Several Factors One Of Which Is Attributed To Political Instability In Major Fuel Producing Nations. As A Result, Vehicle Manufacturers Have Made Several Attempts To Reduce The Fuel Consumption Of Their Engines Which Have Proven Very Effective. One Of The Measures Taken By Manufacturers Is The Development Of Variable Valve Timing (Vvt) Systems. However The Various Vvt Systems Have Their Own Shortcomings For The Ideal Engine Operation Which Are Briefly Explained In This Document. In This Study, Analysis, Optimization And Modification On Mechanical Continuously Variable Valve Timing (Cvvt) Camshaft Which Has Axially Varying Cam Profile Is Made, With The Aim Of Providing Empirical Relations For Designers And Students Interested In The System For Maximum Fuel Economy And Performance For Ic Engines At Any Specific Speed While Minimizing Co2 Emission Per Kw.Hr. The Analysis Is Performed Using A Computer Simulation Program Known As Engine Analyzer Pro V3.9. The Study Is Focused Only Towards Fuel Efficiency And Performance While Other Emission Analysis Such As Co, Hc And Nox Are Not Considered Due To Incapability Of Software At Hand. While Conducting The Study, Simulations Were Run At Different Engine Speeds By Tuning The Valve Opening And Closing Angles, And Lift To Get Values For Optimum Operation. The Tests Were Conducted On A Range Of Speeds From Idle To Maximum Speed With Intervals Of Constant Step And All The Optimum Values Were Recorded. Optimum Values Are Selected Based On Better Performance. Then, The Performance Of The Optimum Valve Timing Parameters Has Been Compared With The Performance Of The Original Camshaft. The Results Have Shown A Maximum Volumetric Efficiency Improvement Of 19% And Maximum Percent Improvement For Brake Torque Is Seen To Be 30.82% While Percent Improvements For Brake Power Are Exactly The Same As Brake Torque With Negligible Differences At Some Engine Speeds. Also A Maximum Improvement Of 8.5% Is Seen For Bsfc. As For Yearly Fuel Saving And Co2 Emission Reduction Per Vehicle, A Maximum Fuel Saving Of 96.47kg/Yr Is Achieved At 5500 Rpm, And A Maximum Co2 Emission Reduction Of 85.9kg/Yr At A Similar Engine Speed Of 5500 Rpm. However, Higher Percentages Of Fuel Savings And Co2 Emission Reductions Are Seen In The Range Between 2000 Rpm And 6000 Rpm. Afterwards, Based On The Finally Obtained Cam Profiles, The Camshaft Has Been Modeled In A Cad Program And A Suitable Operating Mechanism Has Been Proposed. Finally, Empirical Relations For Important Dimensions Have Been Formulated. Finally A Prototype Of The Cylinder Head Has Been Made From Wood, Cement And Plastics.