Computational and Experimental Investigations on the Design Development and Testing of a Variable Valve Timing Engine

Introduction

A vehicle fitted with a spark ignition engine mostly operate under part load conditions in urban areas. In view of higher level of residual gases and pumping losses at part load operation, the fuel consumption is considerably higher than full load conditions. One method of improving the fuel economy under part load condition is to employ a variable valve timing (VVT) concept. This concept regulates the flow of charge into the engine by varying the duration of intake valve operating instead of throttle valve. VVT engine significantly reduces the gasoline consumption under part load conditions and thereby improves overall engine performance. In this direction the following investigations have been carried out. A comprehensive review of literature on different variable valve timing mechanisms has been under taken. A comprehensive computer simulation model was developed for predicting the performance of a single cylinder spark ignition engine at different engine operating conditions. The model after validating with the experimental data was used to arrive at the optimum duration and lift of intake valve which was used in the design of a 3 dimensional cam. for preliminary investigations, three cam profiles were designed which had different valve timings and lifts, The performance of the engine has been studied under early intake valve closing with these three can profiles. Different designs for phase shifting and variable valve timing and lift have been studied and this was followed by the design and development of an ingenious VVT mechanism. Comprehensive experimental investigation have been carried out with conventional and VVT engines at different engine speeds, load and idling conditions. In the case of conventional engine, throttle position has been varied, whilst in VVT engine the throttle position was fixed at wide open throttle (WOT) position. The intake valve timing and lift have been optimized for VVT engine and compared with the optimized value of conventional engine. These experimental investigations have highlighted the salient features in terms of its performance and emissions characteristics of the newly developed VVT engine as compared to the conventional engine. The overall results indicate that operating the engine under VVT mode significantly improves the engine power, fuel economy and emission characteristics.

Salient features

FA new mechanism developed for varying the valve timing lift and duration of intake value. The implement of this mechanism on a single cylinder spark ignition engine has led to a significant improvement in the over all engine performance under part load condition.

Prospective Users

Automobile companies

Keywords

VVT(Variable Valve timing) 3-D cam design, WOT (Wide open throttle)

Type of Technology

Software, model

Status of IPR Protection

Copyright taken.

Developed by : Dr. M K G Babu
Department: Center for Energy Studies

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Indian Institute of Technology, Delhi
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