UWE Bristol Engineering showcase 2015
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Daniel Nicklin<br />
BEng (Hons) Mechanical <strong>Engineering</strong><br />
Project Supervisor<br />
Dr Rohitha Weerasinghe<br />
Formula Student V-Twin Engine Supercharger Feasibility<br />
Introduction<br />
Recently electric vehicles have begun to dominant<br />
due to the advancement of the technologies<br />
involved, but the majority are entered by<br />
established teams with a significant budget. Teams<br />
that have continued to enter combustion vehicles<br />
are moving towards smaller and lightweight<br />
overall packages in order to stay competitive. This<br />
trend has large emphasis on engine downsizing,<br />
with team favouring single and twin cylinder<br />
motorcycle engines over the traditional four<br />
cylinder.<br />
Self-Supercharging<br />
Teams over the past few years have produced<br />
innovative solutions for increasing power by either<br />
modifying existing off the shelf systems or even<br />
manufacture bespoke components. A novel<br />
approach to supercharging is possible by utilising<br />
one or more of the cylinders as a reciprocating<br />
piston pump, taking atmospheric air and<br />
compressing it before it enters the remaining<br />
combustion cylinders. This approach has been<br />
attempted on a variety of car and motorcycle<br />
engines with mixed results and is commonly<br />
known as “self-supercharging”.<br />
Initial Performance Calculations<br />
All components of the intake system have the<br />
ability to restrict the amount of air that an engine<br />
is able to induct. The effectiveness of the entire<br />
process is measured by n v , volumetric efficiency.<br />
η v<br />
=<br />
Actual mass flow rate<br />
Theoretical mass flow rate = 2 m a<br />
ρ a,i<br />
V d N<br />
This equation relates the measured actual mass<br />
flow rate to the potential theoretical mass flow<br />
rate. The volumetric efficiency of the standard<br />
combustion cylinder is typically be in the range of<br />
80 to 90 percent. However it is expected that the<br />
efficiency of the engine would increase to well<br />
over 100 percent due to the increase in inlet air<br />
mass flow rate generated by the piston pump.<br />
Variable Value Units<br />
Piston Pump VE 80%<br />
Stock Engine VE 90%<br />
Boosted Engine VE 160%<br />
Boost Gauge Pressure 125.42 kPa<br />
Power Output 75.48 kW<br />
Torque 90.10 Nm<br />
Initially for a simple model, an optimistic value of<br />
80% was chosen for the volumetric efficiency of<br />
the piston pump. If the engine can induct the<br />
charged air at the same rate that it is produced<br />
then its volumetric efficiency will increase to<br />
160%. This allowed for basic engine parameters<br />
such as the effective compression ratio and<br />
increase in power to then be calculated.<br />
Ricardo Simulation<br />
The piston pump section was simulated using the<br />
Ricardo software using a typical port flow<br />
development scenario. The operation of the piston<br />
pump was tested over a range of engine speeds<br />
and against varying pressure ratios. Initially the<br />
actuation of the valves was logical and simple, but<br />
later optimised based on cylinder filling theories.<br />
System Configuration<br />
The individual components with varying specific<br />
functions were all linked together to form a<br />
complete system, known as a powertrain.<br />
Project summary<br />
An investigation into the suitability of a selfsupercharger<br />
motorcycle engine for use in the<br />
Formula Student competition. Utilising a V-Twin<br />
motorcycle engine, a modification was made to the<br />
intake system so that one of the cylinders only<br />
compresses and moves intake air. It effectively act as<br />
a supercharger providing charged air to the now<br />
single combustion cylinder. With the increased<br />
airflow, especially at high engine speeds, the engine<br />
is theoretically able to burn more fuel and produce<br />
more power.<br />
Project Objectives<br />
• Research the fundamentals of combustion<br />
engines, focusing on the intake system and its<br />
components<br />
• Explore the benefits of a piston pump<br />
supercharger on a restricted engine<br />
• Test components of the intake system 1D<br />
simulations<br />
• Research valve timing for supercharged<br />
applications and make improvements<br />
• Design and evaluate an improved cylinder head for<br />
the supercharged cylinder<br />
• Model the entire system that would be suitable for<br />
use in the Formula Student competition<br />
Project Conclusion<br />
Through the use of computer based simulation and<br />
analysis, sections were tested and optimised based<br />
on generally accepted theories of fluid flow and<br />
dynamics. While the simulation of the system as a<br />
whole was unsuccessful, the piston pump and<br />
cylinder head arrangement were developed through<br />
optimisation of the valve timing. The technique of<br />
using one of an engine’s cylinder for forced induction<br />
is an interesting principle and provides great scope<br />
for further work.
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