Geoffrey Cunningham

An experimental investigation into the pressure drop for turbulent flow in 90° elbow bends:

Abstract The prediction of the pressure drop for turbulent single-phase fluid flow around sharp 90° bends is difficult owing to the complexity of the flow arising from frictional and separation effects. Several empirical equations exist, which accurately predict the pressure loss due to frictional effects. More recently, Crawford et al. [1] proposed an equation for the prediction of pressure loss due to separation of the flow. This work proposes a new composite equation for the prediction of pressure drop due to separation of the flow, which incorporates bends with ratio R/r < 2. A new composite equation is proposed to predict pressure losses over the Reynolds number range 4 × 103-3 × 105. The predictions from the new equation are within a range of −4 to +6 per cent of existing experimental data.

The Development of a Two-Dimensional Transient Catalyst Model for Direct Injection Two-Stroke Applications.

Abstract This paper describes the development of a two-dimensional transient catalyst model. Although designed primarily for two-stroke direct injection engines, the model is also applicable to four-stroke lean burn and diesel applications. The first section describes the geometries, properties and chemical processes simulated by the model and discusses the limitations and assumptions applied. A review of the modelling techniques adopted by other researchers is also included. The mathematical relationships which are used to represent the system are then described, together with the finite volume method used in the computer program. The need for a two-dimensional approach is explained and the methods used to model effects such as flow and temperature distribution are presented. The problems associated with developing surface reaction rates are discussed in detail and compared with published research. Validation and calibration of the model are achieved by comparing predictions with measurements from a flow reactor. While an extensive validation process, involving detailed measurements of gas composition and thermal gradients, has been completed, the analysis is too detailed for publication here and is the subject of a separate technical paper

An investigation of the flowfield through a variable geometry turbine stator with vane endwall clearance

Abstract Variable geometry turbines provide an extra degree of flexibility in air management in turbocharged engines. The pivoting stator vanes used to achieve the variable turbine geometry necessitate the inclusion of stator vane endwall clearances. The consequent leakage flow through the endwall clearances impacts the flow in the stator vane passages and an understanding of the impact of the leakage flow on stator loss is required. A numerical model of a typical variable geometry turbine was developed using the commercial CFX-10 computational fluid dynamics software, and validated using laser doppler velocimetry and static pressure measurements from a variable geometry turbine with stator vane endwall clearance. Two different stator vane positions were investigated, each at three different operating conditions representing different vane loadings. The vane endwall leakage was found to have a significant impact on the stator loss and on the uniformity of flow entering the turbine rotor. The leakage flow changed considerably at different vane positions and flow incidence at vane inlet was found to have a significant impact.

Design and Evaluation of the ELEVATE Two-Stroke Automotive Engine

ELEVATE (European Low Emission V4 Automotive Two-stroke Engine) was a research project part funded by the European Commission to design and develop a compact and efficient gasoline two-stroke automotive engine. Five partners were involved in the project, IFP (Institut Francais Du Parole) who were the project leaders, Lotus, Opcon (Autorotor and SEM), Politecnico di Milano and Queens University Belfast. The general project targets were to achieve Euro 3 emissions compliance without DeNOx catalisation, and a power output of 120 kW at 5000 rev/min with maximum torque of 250 Nm at 2000 rev/min. Specific targets were a 15% reduction in fuel consumption compared to its four-stroke counterpart and a size and weight advantage over the four-stroke diesel with significant reduction in particulate and NOx emissions. This paper describes the design philosophy of the engine as well as the application of the various partner technologies used. Incorporated in the design was an air assisted direct fuel injection system, IAPAC, (Injection Assistee Par Air Comprime) and a charge trapping valve system in the exhaust port. A dual delivery screw compressor for external scavenging supplied a high volume of low-pressure charge air and a low volume of higher-pressure air for the fuel injection system. A high-energy flexible ignition system was used and, at part load, a Controlled Auto Ignition (CAI) process was developed. Lessons learnt from the project, both advantages and associated problems, will be discussed, as well as results from testing. The actual engine tested was constrained by the financial and time limitations of a research funded project. A production version of the engine was partially designed using 3D CATIA. This will be shown and discussed also.

Application of a Generic Curriculum Change Management Process to Motivate and Excite Students

Abstract The School of Mechanical and Aerospace Engineering at Queen’s University Belfast is committed to enhancing the quality of student learning. A plan to implement curriculum change around this goal has been formulated and is already several years underway. A specific part of the plan involved instigating a first year introductory module to engage the students in the practice of their engineering discipline. The complicated nature of devising this type of module with regard to objectives, resources, timeframe and the number of students involved meant that a very systematic approach had to be adopted. This paper presents the simple but definitive change management process that facilitated the creation of a first year Introduction to Engineering module. The generic nature of this process is described and its application to other facets of curriculum change is discussed. Within this process the importance of collaboration to establish a forward momentum is emphasised. This enables academic staff to progress as a group and build curriculum development based on their own experiences, expertise and established practice.

Laser Doppler velocimetry measurements of flow within the cylinder of a motored tow-stroke cycle engine-comparison with some computational fluid dynamics predictions

Abstract This study was carried out to assess the ability of a computational fluid dynamics (CFD) code to predict the scavenging flow in the cylinder of a two-stroke cycle engine. Predictions were obtained from a CFD simulation of the flow within the cylinder. Due to the apparent sym-metry of the engine port layout, only half of the cylinder volume was modelled. Boundary conditions for the CFD model were obtained from experimentally measured pressure-time histories in the crankcase and exhaust. The two-stroke cycle engine was modified to allow laser Doppler velocimetry (LDV) measurements to be made of the in-cylinder flow. The engine was operated under motoring conditions at 500 r/min with a delivery ratio of 0.7. Although the engine scavenge port layout was geometrically symmetrical, an asymmetrical flow field was identified in the cylinder. As a result of this, a direct comparison of the in-cylinder LDV measured and CFD computed results was not possible. However, LDV and CFD results for the in-cylinder flow are presented to help highlight the dissimilarity between the measured and predicted flow fields. Two-dimensional LDV measurements were made in the cylinder at the transfer ports for a portion of the cycle. A comparison of these LDV measurements with CFD predictions of the in-cylinder velocities at the same locations showed that the CFD model could replicate reasonably well the general trend of the flow. The measured cylinder averaged turbulent kinetic energy was compared with that of the CFD model. The qualitative trend of the overall turbulence generating capacity of the engine was well replicated by the CFD model.

A Computational and Experimental Study of the Scavenging Flow in the Transfer Duct of a Motored Two-Stroke Cycle Engine

Abstract This study was carried out to assess the ability of a computational fluid dynamics (CFD) code to predict the scavenging flow in the transfer duct of a two-stroke cycle engine. A two-stroke cycle engine was modified to allow laser Doppler velocimetry (LDV) measurements to be made in one transfer duct. It was operated under motoring conditions at 500r/min with a delivery ratio of 0.7. Predictions were obtained from a dynamic CFD simulation of the flow within the cylinder, transfer duct and a portion of the exhaust duct. Boundary conditions for the CFD model were obtained from experimentally measured pressure-time histories in the crankcase and exhaust. A comparison of measured and predicted transfer duct axial velocities at various locations within the duct showed that the CFD model could replicate the general trend of the flow but not the details. From the LDV measurements and CFD predictions, velocity oscillations were observed between the end of crankcase blowdown and transfer port closing. A one-dimensional general engine simulation package was used to investigate the gas dynamic activity in the transfer duct. It was found that the observed oscillations were due to pressure wave reflections in the transfer duct. The general trend of the axial velocity profile in the transfer duct was well replicated by the one-dimensional simulation as were the exhaust and crankcase pressures.

Flowrate and heat transfer considerations for oxidation catalysts

This paper presents the results of a study into the effects of flowrate and heat transfer in oxidation catalysts. The analysis was performed using a validated two-dimensional catalyst model, which has been designed to predict the behaviour of an oxidation catalyst during transient warm-up and light-off conditions. It is only during the simulation of transient conditions that the true effects of changes to the flowrate and heat loss to the substrate and surrounding materials can be observed. In addition, the two-dimensional design of the model used allows the reaction intensities to be viewed throughout the catalyst and gives the opportunity to examine these effects in both the radial and axial directions. The study has shown that the heat loss from the upstream section of exhaust pipe not only reduces the rate of increase of the feed gas temperature but also removes heat from the outer edges of the catalyst and delays the onset of reactions in these areas. Consequently, the importance of insulating the upstream exhaust pipe and the catalyst housing is demonstrated. It is also shown that increasing the thermal conductivity of the substrate reduces the light-off temperature by transporting heat to the cooler regions more rapidly. Increasing the void fraction of the substrate also has a signiflcant effect on the light-off temperature as less heat is absorbed from the feed gas. Finally, it is shown that increasing the flowrate, or space velocity, of the gas increases the resulting light-off temperature. For the conditions simulated, it was seen that increasing the flowrate by one order of magnitude increased the light-off temperature by only 13 °C. However, emissions breakthrough was seen to occur at a space velocity around 164 000 h 1.

Development of Optimization Techniques for the Design of an Internal Combustion Engine Airbox

The geometrical design of the airbox for an internal combustion engine has a significant effect on the pressure loss in the entire inlet tract. Due to the location of the airbox, its size and shape is usually limited as a result of the proximity to other underbonnet features.The shape is also limited by manufacturing, assembly and NVH considerations. The complexity of the unsteady flow through the airbox and the constraints placed upon it by the available volume in the under-bonnet area make this a challenging design task. This paper reviews the current thinking on methods used to optimize Computational Fluids Dynamics (CFD) problems and how this would apply to the optimization of an airbox for an internal combustion engine. The paper then goes on to detail the findings of the initial validation work on the CFD method for predicting the pressure loss through an airbox. An optimization case study is then presented based on one of the models used for the validation.