Experimental Investigation into the Free-Air Cooling of Air-Cooled Cylinders

This paper describes an experimental investigation into the surface heat transfer coefficient of finned metal cylinders in a free air stream. Eight cast aluminium alloy cylinders were tested with four different fin pitches and five different fin lengths. The cylinders and their fins were designed to be representative of those found on a motorcycle engine. Each electrically heated cylinder was mounted in a wind tunnel and subjected to a range of air speeds between 2 and 20 m/s. The surface heat transfer coefficient, h, was found primarily to be a function of the air speed and the fin separation, with fin length having a lesser effect. The coefficient increases with airspeed and as the fins are separated or shortened. It was also noted that a limiting value of coefficient exists, influenced only by airspeed. Above the limiting value the surface heat transfer could not be increased by further separation of the fins or reduction in their length.

Experimental investigation into the temperature and heat transfer distribution around air-cooled cylinders

This paper describes an experimental investigation into the surface heat transfer coefficient of finned metal cylinders in a free air stream. Ten cylinders were tested with four different fin pitches and five different fin lengths. The cylinders and their fins were designed to be representative of those found on a motorcycle engine with an external cylinder diameter of 100 mm and fin lengths of 10 to 50 mm. The fins of each cylinder were gravity die cast in aluminum allow. Each cylinder was electrically heated and mounted in a wind tunnel which subjected it to a range of air speeds between 2 and 20 m/s. The surface heat transfer coefficient, h, was found primarily to be a function of the air speed and the fin separation, with fin length having a lesser effect. In addition to the determination of an overall heat transfer coefficient, the distribution of cooling around the circumference of each cylinder was also studied. Not surprisingly, the cooling was found to be greatest on the front of the cylinder, which was the side first impinged by the air stream. The cooling of the rear of the cylinder was better than might have been expected and this is quantified.

A Theoretical and Experimental Study of Resonance in a High Performance Engine Intake System: Part 1

The unsteady gas dynamic phenomena in engine intake systems of the type found in racecars have been examined. In particular, the resonant tuning effects, including cylinder-to-cylinder power variations, which can occur as a result of the interaction between an engine and its airbox have been considered. Frequency analysis of the output from a Virtual 4-Stroke 1D engine simulation was used to characterise the forcing function applied by an engine to an airbox. A separate computational frequency sweeping technique, which employed the CFD package FLUENT, was used to determine the natural frequencies of virtual airboxes in isolation from an engine. Using this technique, an airbox with a natural frequency at 75 Hz was designed for a Yamaha R6 4-cylinder motorcycle engine. The existence of an airbox natural frequency at 75 Hz was subsequently confirmed by an experimental frequency sweeping technique carried out on the engine test bed. A coupled 1D/3D analysis which employed the engine simulation package Virtual 4-Stroke and the CFD package FLUENT, was used to model the combined engine and airbox system. The coupled 1D/3D analysis predicted a 75 Hz resonance of the airbox at an engine speed of 9000 rpm. This frequency was the induction frequency for a single cylinder. An airbox was fabricated and tested on the engine. Static pressure was recorded at a grid of points in the airbox as the engine was swept through a speed range of 3000 to 10000 rpm. The measured engine speed corresponding to resonance in the airbox agreed well with the predicted values. There was also good correlation between the amplitude and phase of the pressure traces recorded within the airbox and the 1D/3D predictions.

Improving the Fuel Economy of a Tuned 600cc FSAE Engine

To maintain its relevance, motorsport cannot be exempt from
the trend of increasing fuel economy. This bears obvious
competitive benefits as well, either in decreasing the
frequency of pit stops or the mass of fuel carried. Given the
increased points weighting of fuel economy for the Formula
Student (FS) competition, a complete analysis was performed
on the Queen's Formula Racing 600cc motorcycle engine in
preparation for the 2011 competition.
The criteria for such high performance fuel economy differ to
a degree from most mass transportation counterparts and were
divided into three distinct regimes; full load, part load and no
load conditions.
Full load positions naturally demand maximum torque for
performance but that does not imply that fuel savings cannot
be made whilst preserving this. The point at which maximum
torque is produced with minimum air -fuel ratio, Leanest
mixture for Best Torque (LBT), was therefore sought and
mapped for full load.
At part load, torque is less of a concern, and maintaining a
sustainable engine temperature and transient response become
more important. With decreasing AFR, engine temperatures
can rise dramatically so temperatures were measured close to
the exhaust port for a wide range of air-fuel ratios.
Competition track data was analysed to highlight key part load
operating regions and these were mapped according to
measured safe temperature limits. Torque response to a step
throttle change was also measured to ensure suitable engine
transient performance was maintained.
At no load conditions, with low engine speed only idle
conditions need to be satisfied. In the situation where the
engine is still at high speed without load, the engine is being
motored and no fuel is required. An overrun fuel cut was
employed to reflect this giving significant fuel savings. The
effect on torque and engine pickup was measured.
Modifications were also made to the fuel injector location to
improve fuel mixing and evaporation at this lower air flow
condition.
These mapping regimes were implemented and tested using
fully transient lap simulations using competition track data
and a four quadrant AC engine dynamometer. The experiment
indicated a reduction in fuel consumption for 22 laps of the FS
track from 5.08litres to 3.67litres, around 27% in total. The
actual fuel used at the 2011 competition was 3.6 litres while
placing 8th in the endurance event, further validating the
benefits of these mapping regimes.