IT Technologies
-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.
Developed by : Dr. M K G Babu
Department: Center for Energy Studies
Contact:
Managing Director
Foundation for Innovation and Technology Transfer (FITT)
Indian Institute of Technology, Delhi
Hauz Khas, New Delhi-110016, INDIA
Tel : 91-011-26597167, 26857762, 26581013, 26597153
Fax : 91-011-26851169
E-mail : drkdpn@gmail.com
