Browsing by Author "Harrison, M. F."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Open Access Design and investigation of a diesel engine operated on pilot ignited LPG(Cranfield University, 2009-03) Theodoridis, Eudoxios; Harrison, M. F.This thesis explores the idea of igniting LPG in a compression ignition diesel engine using pilot diesel injection as spark ignition medium. The main advancement in using this technology on current diesel engines is the establishment of a better balance between NOx and PM emissions without losing too much of the CO2 benefits of diesel. With the advent of common rail diesel engines, it is now possible to get control of pilot diesel injection and make the LPG and diesel control systems work together. Combined diesel and LPG operation is a new subject for engine research, so the thesis moves on to consider the results from detailed engine simulation studies that explore the potential benefits of the mix. Subsequent simulations of a modern four cylinder dCi engine suggest that with closer control over the pilot diesel injection, diesel like performance can be obtained, hopefully with less emissions than currently expected from diesel only operation. A single cylinder variable compression ratio research engine was developed to explore diesel /LPG dual fuel operation. A second generation common rail injection rig was also developed for the engine and for fuel spray characterisation. Engine experiments proved the concept of using a modest charge of pilot injected diesel for igniting a larger dose of port injected LPG. The experimental work results suggest that combining diesel common rail injection technology with the state of the art LPG injection systems, it is possible to establish a better balance between NOx/ PM emissions without losing too much of the CO2 benefits from the diesel operation.Item Open Access Development of a liquid-phase LPG MPI conversion system(2004-10) Vuorenkoski, Anni Kaisa; Jermy, Mark; Harrison, M. F.For decades Liquefied Petroleum Gas (LPG) has been considered as one o f the most prominent alternative fuels to petrol. LPG typically consists of propane, butane and propylene, but also smaller quantities o f methane and ethane. LPG has a low price compared to petrol, the potential o f low emissions and has indigenous availability. It possesses approximately the same energy density, on a gravimetric basis, as petrol, vaporises easily, mixes readily with air, is resistant to auto-ignition, has wide flammability limits and a good laminar burning speed. Therefore it is also possible to achieve an acceptable efficiency and power from a spark ignition engine run with LPG. The state-of-the-art LPG systems used in spark-ignition engines are either mono-fuel systems, where the vehicle is solely operated using LPG, or bi-fuel vehicles, capable o f using either petrol or LPG. The objectives o f this work were to develop an aftermarket conversion bi-fuel LPG system, which would improve the efficiency o f the engine during LPG operation, with further improvements in the mixture preparation and control, the methods for LPG fuelling calibration and the methods to prevent premature vaporisation in the fuel rail. An additional objective o f this study was to investigate the performance and combustion o f LPG in a non-optimised spark-ignition engine. A prototype system was developed and demonstrated in a 4-cylinder research engine. This novel system uses a liquid LPG injection system, in contrast to the conventional vapour injection systems used in aftermarket LPG bi-fuel conversions. A significant improvement in engine power output was shown, as well as an improvement in mixture control. An optical diagnostics method was applied in order to study the mixture preparation using two alternative LPG fuel injection configurations. The results from both the mixture formation study and the engine experiments showed that the charge cooling effect can be used to improve the efficiency o f a non-optimised bifuel engine. It was also shown that from the mixture control point o f view, injecting the fuel directly to the manifold gives a significant advantage over systems where the fuel is injected to the manifold through coupling pipes. This novel LPG system also uses a fuel pressurising method that improves the fuel system performance in extreme conditions. In addition, a control method to prevent the premature vaporisation of the LPG fuel in the fuel supply line was developed. The method comprises an optical sensor which can detect migrating vapour bubbles in addition to complete phase changes in the fuel line. It was noticed during validation o f the sensor that vaporisation in the fuel rail starts in local hot spots, before the global saturation conditions in the fuel rail are met. This work has demonstrated the potential o f using non-optimised LPG systems in bifuel vehicles. However, the final validation o f the novel control system requires extensive testing on a fleet of test vehicles, and this was not possible within the scope of the work.Item Open Access A hybrid boundary for the prediction of intake wave dynamics in IC engines(Elsevier, 2004-02) Harrison, M. F.; Perez Arenas, R.This paper concerns the calculation of wave dynamics in the intake systems of naturally aspirated internal combustion (I.C.) engines. In particular it presents a method for improving the boundary conditions required to solve the one-dimensional Euler equations that are commonly used to describe the wave dynamics in time and space. A number of conclusions are reached in this work. The first relates to the quasi-steady state inflow boundary specified in terms of ingoing and outgoing characteristics that is commonly adopted for engine simulation. This is correctly specified by using the pair of primitive variables pressure (p) and density (ρ) but will be unrealistic at frequencies above a Hemholtz number of 0.1 as only stagnation values po, ρo are used. For the case of I.C. engine intake simulations this sets a maximum frequency of around 300Hz. Above that frequency the results obtained will become increasingly unrealistic. Secondly, a hybrid time and frequency domain boundary has been developed and tested against linear acoustic theory. This agrees well with results obtained using a quasi-steady state boundary at low frequencies (Helmholtz number less than 0.1) and should remain realistic at higher frequencies in the range of Helmholtz number 0.1 - 1.84. Thirdly, the cyclic nature of the operation of the IC engine has been exploited to make use of the inverse Fourier transform to develop an analytical hybrid boundary that functions for non-sinusoidal waves in ducts. The method is self starting, does not rely on iterations over complete cycles and is entirely analytical and therefore is an improvement over earlier hybrid boundaries.Item Open Access Intake acoustics of naturally aspirated racing engines(Cranfield University, 2006-04) Dolinar, A; Harrison, M. F.The intake system is one of the components on the internal combustion engine most linked with the achievement of the high volumetric efficiency required of naturally aspirated engines. High performance racing engine intake systems have unusual geometry with separate intake pipes (often known as intake trumpets) housed in a common airbox. These intake trumpets are short pipes that are sometimes cylindrical but often conical. The flow within the intake system is very unsteady with high frequency wave action taking place. A carefully developed intake trumpet can use the wave action to tune the engine and therefore increase the performance distinctly. The intake tuning is strongly dependent on the acoustic properties of the intake system. Two important parameters are the pressure wave reflection coefficient at the open inflow end of the intake pipe (to tune the engine effectively) and the acoustic length of the intake pipe (to tune the engine at the appropriate engine speed). Acoustic measurements show that the open inflow end reflection coefficient decreases with inflow but increases with external (coaxial) flow. CFD calculations show that the vena contract a which gets created at the open inflow to the pipe disappears with coaxial flow. A conical inflow shape decreases the reflection coefficient at certain frequencies and influences the phase angle of the acoustic waves. One dimensional prediction models for the wave transfer inside these conical intake pipes are validated against acoustic measurement results. 4 The airbox decreases the reflection coefficient distinctly due to three dimensional resonances inside the airbox and limits the use of one dimensional prediction models, but the acoustic length can still be predicted accurately. Fuelling inside the intake pipe decreases the speed of sound by 10% and thus increases the acoustic pipe length. Therefore it influences the engine tuning and needs be considered when developing intake systems. A new acoustic measurement method is introduced which allows the measurement of the acoustic pipe length within the conical part of the intake pipe. Finally, the time varying nature of the intake flow and intake acoustics is explored on a running racing engine by means of hot-wire and pressure measurements and shows the influence of intake acoustics on the fluctuating intake airflow velocity especially during the period when the intake valves are closed.Item Open Access A linear acoustic model for intake wave dynamics in IC engines(Elsevier, 2004-01-06) Harrison, M. F.; Stanev, P. T.In this paper, a linear acoustic model is described that has proven useful in obtaining a better understanding of the nature of acoustic wave dynamics in the intake system of an internal combustion (IC) engine. The model described has been developed alongside a set of measurements made on a Ricardo E6 single cylinder research engine. The simplified linear acoustic model reported here produces a calculation of the pressure time-history in the port of an IC engine that agrees fairly well with measured data obtained on the engine fitted with a simple intake system. The model has proved useful in identifying the role of pipe resonance in the intake process and has led to the development of a simple hypothesis to explain the structure of the intake pressure time history: the early stages of the intake process are governed by the instantaneous values of the piston velocity and the open area under the valve. Thereafter resonant wave action dominates the process. The depth of the early depression caused by the moving piston governs the intensity of the wave action that follows. A pressure ratio across the valve that is favourable to inflow is maintained and maximised when the open period of the valve is such to allow at least, but no more than, one complete oscillation of the pressure at its resonant frequency to occur whilst the valve is open.Item Open Access A linear acoustic model for multi-cylinder IC engine intake manifolds including the effects of the intake throttle(Elsevier, 2004-12) Harrison, M. F.; Rubio Unzueta P. L.; De Soto, I.This paper presents a linear acoustic model of a multi-cylinder intake manifold that can be used as part of a hybrid time/frequency domain method to calculate the intake wave dynamics of practical naturally aspirated engines. The method allows the user to construct a model of almost any manifold of complex geometry. The model is constructed as an assemblage of sub-models: (i) A model for a straight pipe with both ends open and through-flow. (ii) A model for an expansion chamber consisting of three lengths of pipe laid end-to-end: a narrow bore pipe expanding into a wide bore pipe contracting into a narrower bore pipe once more. (iii) A model of a side-branch, which includes a model for a straight pipe with one end closed and a model for the three way junction that joins the side-branch to a length of flow pipe. (iv) A model for an expansion with two (or more) side-branches, which combines the sub-models (i, ii, iii) into a multi-way (n-way) junction model. (v) A model for an intake throttle. Good agreement with measurement has been found for each sub-model when bench-tested in isolation and encouraging agreement has been found when many sub-models are used together to model a complex intake manifold on a running engine.Item Unknown Measurement and analysis of rally car dynamics at high attitude angles(Cranfield University, 2006-05) Croft-White, Michael; Harrison, M. F.; Greenhalgh, Douglas A.This research aims to investigate the nature of high β-angle cornering as seen in rallying and in particular the World Rally Championship. This is achieved through a combination of sensor development, on-car measurement and vehicle dynamic simulation. Through the development of novel β-angle measurement technology it has become possible to measure and study vehicle attitude dynamics on loose gravel surfaces. Using this sensor, an understanding of how a rally driver uses the dynamics of the vehicle and surface to maximise performance has been obtained. By combining the new data stream with accepted vehicle dynamic theory, the tyres have been considered and general trends in gravel tyre performance unveiled. Through feedback, these trends have been implemented as a means of tuning a dynamic model to improve realism and permit an analysis of cornering trends in rally cars. Active control systems have been considered that could implement more sophisticated algorithms based on this understanding and potentially use the new sensor information as an input signal. A case study which explores such a possibility is included.Item Unknown Measurement and analysis of rally car dynamics at high attitude angles(Cranfield University, 2006-05) Croft-White, Michael; Harrison, M. F.; Greenhalgh, Douglas A.This research aims to investigate the nature of high β-angle cornering as seen in rallying and in particular the World Rally Championship. This is achieved through a combination of sensor development, on-car measurement and vehicle dynamic simulation. Through the development of novel β-angle measurement technology it has become possible to measure and study vehicle attitude dynamics on loose gravel surfaces. Using this sensor, an understanding of how a rally driver uses the dynamics of the vehicle and surface to maximise performance has been obtained. By combining the new data stream with accepted vehicle dynamic theory, the tyres have been considered and general trends in gravel tyre performance unveiled. Through feedback, these trends have been implemented as a means of tuning a dynamic model to improve realism and permit an analysis of cornering trends in rally cars. Active control systems have been considered that could implement more sophisticated algorithms based on this understanding and potentially use the new sensor information as an input signal. A case study which explores such a possibility is included.Item Unknown Predictive engineering processes for motorcycle dynamics(Cranfield University, 2004-04) Styles, M. J.; Sharp, Robin S.; Harrison, M. F.This study is an investigation into the use of computer aided handling and stability analysis for motorcycles. In particular it considers Triumph Motorcycles Ltd., delving into Triumph's background, their strategy and the likelihood of them using virtual techniques for stability and handling analysis. Additionally, this work reviews current knowledge of motorcycle dynamics analysis and builds on it. A novel way of studying the steering feel has been developed by analysing the response of the steer torque equation for the Sharp 1971 [1] and 1994 [2] models. The individual contributors to this equation are identified and the important ones are investigated further. One conclusion of this study is that in reduced cornering and camber conditions the steer angle of the motorcycle, for a given steering input torque, increases when compared to standard operating conditions. The steer angle also increases further as the speed increases. An update to a previous motorcycle model [3] has been made by revising the parameter set, so that it is more applicable to a modem sports motorcycle. The rider model and relaxation length description have also been improved upon. The results show that the new motorcycle has been made more manoeuvrable by the alterations to the parameters. An optimal preview steering control system for cars [4] has been taken, improved upon and used with the newly developed motorcycle model discussed above. The results from this novel work allow a designer to alter parameters and see how this affects the motorcycles steering demands, path following, etc. It was shown that an increase in the front wheel inertia makes the motorcycle feel like the steering is heavier, and an increase in the front wheel radius and wheelbase make the steering feel lighter. Future work into non-linear analysis is recommended and improved rider and tyre modelling is also desired.