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A number of studies have been carried out examining the impact of biodiesel blend ratio on vehicle performance and emissions, however there is relatively little data available on the interaction between blend ratio and reduced ambient temperatures over the New European Drive Cycle (NEDC). This study examines the effects of increasing the blend ratio of Rapeseed Methyl Ester (RME) on the NEDC fuel consumption and tailpipe emissions of a vehicle equipped with a 2.0 litre common rail diesel engine, tested on a chassis dynamometer at ambient temperatures of 25, 10 & −5°C. This study found that under low temperature ambient conditions increasing blend ratios had a significant detrimental effect on vehicle particulate emissions reversing the benefits observed at higher ambient temperatures. Blend ratio was found to have minimal impact on hydrocarbon emissions regardless of ambient temperature while carbon monoxide and NOx emissions were found to increase by up to 20% and 5.5% respectively.

A study has been undertaken to demonstrate the use and potential benefits of actively controlled coolant jets in a vehicle. Results have shown that active control of cooling jets has the potential to regulate the temperature of thermally critical areas of the cylinder head, in this case the exhaust valve bridge. In addition the temperature gradient across the head from the exhaust valves to the inlet valves is directly influenced. These capabilities offer improved control of the combustion process and enhanced durability. Furthermore the system allows heat to be rejected at much lower overall coolant flow rates than with a conventional arrangement. The technique relies on an adequate supply of coolant at a lower temperature than that within the engine and on the availability of a suitable measurement technology within the thermally critical region. Unlike passive precision cooling the active jets allow optimization of the cooling at all engine speed / load points.

An experimental investigation, using a Design of Experiments approach, has sought to quantify the potential CO2 savings that could be made by the electrification of certain mechanical devices as part of the Front End Auxiliary Drive (FEAD) on a 2.4 litre DI diesel engine. The experiments considered the electrification of the cooling fan; power assisted steering system, and the vacuum pump. A number of different build configurations have been evaluated on a dynamic testbed over the New European Drive Cycle (NEDC). The overall conclusion is that the move towards electrification of the devices listed would result in a 6-7% saving in CO2 over the NEDC. These benefits however, need to be considered alongside other issues such as increased on-cost, more control complexity and reliability implications of adopting electrically driven devices.

This paper describes the results of an investigation into alternative control strategies for diesel engines equipped with Exhaust Gas Recirculation (EGR) and Variable Geometry Turbocharging (VGT). The objectives of the research were to improve the engine aircharge performance during transient manoeuvres, thus bringing benefits for fuel economy, exhaust emissions and engine transient performance. Two of the investigated areas are detailed in this paper; The coordinated control of the EGR-VGT systems to improve transient airflow at low-speed, low-load operation Transient VGT control using exhaust pressure feedback A simple and effective method for coordinating the EGR-VGT system is demonstrated to improve airflow response to tip-ins and tip-outs. The exhaust pressure feedback method is shown to overcome difficulties in the transient control of VGT systems, offering improved engine torque response and reduced transient backpressure.

The measurement of vehicle modal emissions is technically challenging due to the major issue of determining exhaust gas mass flow rate and ensuring that it is synchronous with the emission measurement of that corresponding ‘slug’ of exhaust gas. This is very evident when attempting to measure small passive NOx catalyst conversion efficiencies. This paper highlights alignment issues with regard to the variation of time delays associated with engine and vehicle events and the CO2 tracer method for determining exhaust gas flows.

An experimental study has been carried out to assess the capability of injecting vaporised fuel into the exhaust gas of a diesel engine to achieve elevated outlet temperatures from an oxidation catalyst for the thermal regeneration of particulate filters. Termed catalytic combustion and passive in nature, controlled experiments have proved the concept with the limitation on catalyst outlet temperature being dictated by the material limits of the exhaust system and the availability of oxygen.

A proof-of-concept study has been undertaken to demonstrate the use and potential benefits of actively controlled coolant jets in an IC engine cooling gallery simulator. Results have shown that substantial reductions in coolant volumes are possible and that the control of the liquid/metal surface temperature can be achieved within +/- 0.2°C in response to transient heat flux conditions.

Time-alignment sensitivity studies have been carried out to assess the accuracy of instantaneous mass NOx emissions on a chassis rolls dynamometer. The work is part of a larger project aimed at measuring passive NOx catalyst conversion efficiencies. Instantaneous NOx emissions are examined in relation to the NEDC vehicle speed trace at multi sampling points, and phase and time alignment issues are highlighted and discussed. It has been found that a small mismatch of the vehicle speed trace to the instantaneous mass of emissions of ± 2 seconds can lead to results indicating that the conversion efficiency is anywhere between 0-20%. Finally, examples are presented showing the difficulties of attempting to adjust the time alignment of raw emissions data.

Closed and recycle diesel engine systems have been developed for use on board conventional manned military and commercial submarines. This type of power system is now being considered for unmanned Autonomous Underwater Vehicle (AUV) applications. However, with a simple recycle system, the recirculated carbon dioxide rich combustion products can be expected to have an adverse effect on engine performance. Recent developments in this field have been concerned with producing synthetic atmospheres whose properties match those of free air so enabling the non air performance at least to match that of the normally aspirated unit. This philosophy has resulted in bulky and complicated exhaust gas management systems. The possibility of a diesel engine operating on a carbon dioxide/oxygen atmosphere whilst still retaining acceptable engine operating performance would therefore seem to require further examination.

Non-air-breathing diesel engine systems have, and continue to be developed for underwater applications. When the engine is operated in such an environment the intake oxidant mixture consists of a combination of oxygen and recycled exhaust gas. The latter will contain combustion gaseous products and may also include additional inert diluents. Since its initial conception in the late nineteenth century, a major problem encountered in the operation of the recycle diesel engine has been the detrimental effect of the recirculated exhaust carbon dioxide upon the engine's performance. To avoid this problem exhaust gas scrubbing systems have been developed to remove the carbon dioxide from the exhaust gases. In addition, inert gases such as argon and helium have been added to the non-air mixture to improve its thermodynamic and transport properties and hence engine performance.

Many Diesel engine development programs concentrate almost exclusively on steady state investigations to benchmark an engines performance. In reality, the inter-action of an engine's sub-systems under transient evaluation is very different from that evident during steady state evaluation. The transient operation of a complete engine system is complex, and collecting test data is very demanding, requiring sophisticated facilities for both control and measurement. This paper highlights the essential characteristics of a Diesel engine when undertaking testbed transient manouevres. Results from simple transient sequences typical of on-road operation are presented. The tests demonstrate how transient behaviour of the engine deviates greatly from the steady state optimum settings used to control the engine.

The use of variable geometry turbocharging (VGT) as an aid to performance enhancement has been the subject of much interest for use in high-speed, light-duty automotive diesel applications in recent times (4). One of the key benefits anticipated is the improved transient response possible with such a device over the conventional fixed geometry turbine with wastegate. The transient responses of two different types of variable geometry turbocharger have been investigated on a dynamic engine test bed. To demonstrate the effect of the turbocharger on the entire system a series of step changes in engine load at constant engine speed were carried out with the turbocharger and exhaust gas recirculation (EGR) systems under the control of the engine management microprocessor. Results are presented which compare the different performance and emissions characteristics of the devices. Some control issues are discussed with a view to improving the transient response of both types.

The findings presented in this paper are part of a long term project aimed at raising the science of heat transfer in internal combustion engine cooling galleries. Initial work has been undertaken by the authors and an experimental facility is able to simulate different sizes of coolant passages. External heat is applied and data for the forced convective, nucleate boiling and transition or critical heat flux (CHF) regimes has been obtained. The results highlighted in this paper attempt to quantify the effects of cooling passage surface roughness on the nucleate boiling regime. Tests have been conducted using aluminium test pieces with surface finishes described as smooth, intermediate and as-cast. It has been found that the as-cast surface increases the heat flux density in the nucleate boiling region over that of the smooth and intermediate surfaces.

Although successful “precision cooled” prototype engines have been demonstrated, the design of most mainstream coolant jackets has evolved only cautiously, and lacked this major change in approach. The achievements and potential of precision cooling are reviewed, along with an extension into nucleate boiling based heat transfer. It is demonstrated that ideas for advanced “external” cooling systems with low flowrates are in fact extremely compatible with the “internal” precision engine cooling philosophy, and in combination promise even larger benefits.