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Technical Paper

Optimising Engine Performance and Emissions Using Bayesian Techniques

Research and development (R&D) programmes to optimise engine performance and emissions involve a large number of experimental variables and the optimum solution will normally be a trade-off between several measured responses (e.g. fuel consumption, exhaust emissions and combustion noise). The increasing number of experimental variables and the search for smaller improvements make identification of optimum configurations and robust solutions more demanding. Empirical models are routinely used to explore the trade-offs and identify the optimum engine hardware build and parameter settings. The use of Bayesian methods enables prior engineering knowledge to be explicitly incorporated into the model generation process, which allows useful models to be developed at an earlier stage in the test programme. It also enables a sequential approach to experimental design to be adopted in which the ultimate engineering objectives can be more effectively taken into account.
Technical Paper

Evaluation of a Low Emissions Concept on a 50cc 2-Stroke Scooter Engine

A preliminary test bed evaluation of a potentially simple and low cost stratified charging concept is presented for small capacity 2-stroke scooter engines. The end development objectives of the concept are to reduce engine out hydrocarbon emissions and to improve fuel economy while providing engine fuelling by a simple carburettor type fuel metering device. Such a concept, when combined with a catalyst, could achieve significant vehicle emissions reductions with potentially improved catalyst durability. The results presented in this paper, from a preliminary test bed evaluation of the stratified charging concept using electronic fuel injection to provide the fuelling, have shown that engine out hydrocarbon emissions can be effectively reduced at medium to high load without a loss in wide open throttle torque.
Technical Paper

The Effect of Gasoline Composition on Stoichiometry and Exhaust Emissions

Six full range gasolines were tested in two engines (one with a catalyst) operated at 4 steady states. Engine-out regulated emissions responded to equivalence ratio, Φ, in the accepted manner. For both CO and NOx, there was a characteristic, single emissions response to changes in Φ. Changing fuel composition will primarily alter the production of these emissions by modifying the stoichiometric air/fuel ratio, projecting engine operation onto another part of the Φ response curve. These Φ effects, which are independent of engine design, also determine how operating conditions affect engine-out CO and NOx. Speciated hydrocarbon measurements at engine-out and tail-pipe confirm results seen in previous test-cycle based programmes.
Technical Paper

The Effect of Hydrocarbon Composition on Lean NOx Catalysis

The effect of pre-catalyst speciation on lean NOx catalysis was investigated using a chemically defined fuel matrix. Nine model fuels and a diesel fuel were injected into the exhaust stream of a medium duty diesel engine prior to a DeNOx catalyst. NOx conversions ranged from 9% at a mid speed and load test point to 43% at a higher load test point. On an absolute basis, model fuels produced up to 34% greater NOx conversions relative to diesel. Speciation revealed that, compared with low temperature test points, cracking and oxidation at peak torque significantly modified the auxiliary HC input to the catalyst. The quantity of ‘cracked’ derivatives of the auxiliary fuel, namely alkene and carbonyl species, correlated well with NOx conversions.
Technical Paper

Development Experience of a Poppet-Valved Two-Stroke Flagship Engine

The gasoline-fuelled direct injection poppet-valved two-stroke engine described in (1) has been built in single cylinder form and tested to evaluate the potential of this concept as a passenger car powerplant. Development of the combustion and scavenge system is described. Following development, the engine produced a specific power output of 90 kW/litre at 5000 rev/min, with a peak torque of 200 Nm/litre at 2000-2500 rev/min. HC emissions were maintained in the range 3-15 g/kWh over the majority of the engine operating range and NOx emissions in the load range used in the FTP drive cycle were less than 3 g/kWh. Part load fuel consumption under steady state conditions was 8% lower than for a stoichiometric four-stroke engine sized for equal power output.
Technical Paper

The Use of Constant Volume Sampler and Dilution Tunnel to Compare the Total Particulates from a Range of Automotive Engines

The development of a simple CVS particulate test and its application to various engine types is shown to quantify a number of problem areas. Research into the reduction of particulates in exhaust gases can be carried out more effectively by this technique than by the older optical methods. These investigations however lag far behind those into the better known gaseous emissions.
Technical Paper

Passenger Car Noise Control Measures and Their Effects on Fuel Economy, Weight and Cost

Various passenger car practical noise control measures are presented and discussed. Emphasis is placed on the noise control tradeoffs with fuel economy and weight. Both diesel and gasoline powered automobiles were considered. The diesel was of the indirect injection type and a conventional spark ignition engine constituted the gasoline powered type. The baseline vehicle maintained throughout the analysis was a 2750 lb inertia weight passenger car (2400 lb, 1100 kg kerb weight). Major findings are summarised for five noise control measures considered to be most likely incorporated into future vehicles. They include: a) reduced engine speed by 10 percent, b) engine sizing and configuration, c) combustion process, d) engine structures, shielding and enclosures, and e) gas flow. Summaries for each noise control measure contain data on achievable noise reductions, and the corresponding change in fuel economy, vehicle weight and cost.
Technical Paper

DETR/SMMT/ CONCAWE Particle Research Programme: Heavy Duty Results

The aim of this study was to investigate the changes in mass and number based heavy duty diesel engine particle emissions with respect to various test conditions, engine technologies and fuel specifications. Comparative particle size data and regulated particulate matter are presented from three heavy duty engines and three fuels. This paper describes results from the DETR/CONCAWE/SMMT Particle Research Programme. Three heavy duty diesel (HDD) engines representing Euro I, II and III technologies were tested with a range of fuels. These fuels included UK ultra low sulphur diesel (UK-ULSD), EN590 (EU2000) specification and Swedish Class I fuels. Continuing research suggests that when changes in regulated particulate mass emissions are compared to both individual mode and total cycle mass and number weighted particle size distributions there is often no significant correlation. In an attempt to provide further data in this area the following measurement methodology was adopted.
Technical Paper

DETR/SMMT/CONCAWE Particle Research Programme: Sampling and Measurement Experiences

This paper describes the observed effects of parameters such as tunnel dilution ratio, test procedures and measurement methods on particle emissions. Attention is drawn to the transient behavior of nanoparticles within real legislated cycle conditions using conventional dilution systems. The aim of the paper is to communicate the limitations of widely used measurement equipment to enable a more confident interpretation of the particle size data. The paper describes the information obtained during the DETR/CONCAWE/SMMT Particle Research Programme with regard to the sampling and measurement of particles emitted from light duty vehicles and heavy duty engines. Light duty vehicles were tested on gasoline, diesel and LPG, while heavy duty engines were tested on both diesel and compressed gaseous fuels. Two Scanning Mobility Particle Sizer (SMPS) instruments were employed in order to cover a measurement range from a lower limit of ∼7nm up to ∼710nm.
Technical Paper

Particle Measurement Programme (PMP):Particle Size and Number Emissions Before, During and After Regeneration Events of a Euro 4 DPF Equipped Light-Duty Diesel Vehicle.

By early 2007, all major manufacturers of light-duty diesel vehicles are marketing models equipped with diesel particulate filters (DPFs). However, there is still a lack of understanding of the particles emitted when the DPF undergoes regeneration. This paper focuses on measuring particle emissions of a representative light-duty diesel vehicle equipped with DPF and employing a fuel-borne catalyst (FBC) to aid regeneration. Particulate Matter (PM) and non-volatile particle number emissions are measured throughout testing according to the Particle Measurement Programme (PMP) proposals. In addition, an Engine Exhaust Particle Sizer (EEPS) connected directly to the CVS is used to give real time size distributions of both volatile and non-volatile particles. The paper focuses on particle emissions during regenerating New European Driving Cycles (NEDCs).
Technical Paper

Advanced Diesel Technology to Achieve Tier 2 Bin 5 Emissions Compliance in US Light-Duty Diesel Applications

Future growth of the US light-duty diesel market is highly dependent on achieving cost effective and robust emissions solutions. For this reason, ACTION (Advanced Combustion Technology to Improve engine-Out NOx) is being developed by Ricardo. This research is delivering reduced emissions through the application of Highly Premixed Cool Combustion (HPCC). NOx reduction is primarily achieved through the reduction of charge oxygen concentration, accomplished by reducing air/fuel ratio and increasing exhaust gas recirculation. This approach coupled with enhanced combustion system efficiency delivers a practical approach to meet future emissions compliance while minimizing aftertreatment requirement. The paper will examine key engine technology developments to deliver US Tier 2 Bin 5 emissions in Light Duty Diesel applications. In particular, Bin 5 emissions compliance will be possible in passenger car applications.
Technical Paper

Characterisation of the Soot Formation Processes in a High Pressure Combusting Diesel Fuel Spray

As part of an ongoing investigation, the influence of In Cylinder Pressure (ICP) and fuel injection pressure on the soot formation processes in a diesel fuel spray were studied. The work was performed using a rapid compression machine at ambient conditions representative of a modern High Speed Direct Injection diesel engine, and with fuel injection more representative of full load. Future tests will aim to consider the effects of pilot injections and EGR rates. The qualitative soot concentration was determined using the Laser Induced Incandescence (LII) technique both spatially and temporally at a range of test conditions. Peak soot concentration values were determined, from which a good correlation between soot concentration and injection pressure was observed. The peak soot concentration was found to correlate well with the velocity of the injected fuel jet.
Technical Paper

DETR/SMMT/CONCAWE Particulate Research Programme: Light Duty Results

The DETR/SMMT/CONCAWE Particulate Research Programme was designed to investigate the effects of vehicle/engine technology level, fuel specification and various operating conditions on emissions of particle mass, number and size. Results from the heavy duty part of the programme and details of the measuring protocols have already been published. This paper gives the results of the light duty study. This consisted of six vehicles and eight fuels covering gasoline, Diesel and LPG technologies. These six vehicles represented Euro II (1996) and Euro III (2000) technologies. Diesel fuels included EN590 (1996), EN590 (2000), UK ultra low sulphur Diesel (UK ULSD) and Swedish Class I Diesel, while gasoline fuels comprised EN228 (1996), EN228 (1999) and UK ultra low sulphur gasoline (UK ULSG).
Technical Paper

Stratified Scavenging Applied to a Small Capacity Two-Stroke Scooter for the Reduction of Fuel Consumption and Emissions

The advantages of high power to density ratio and low manufacturing costs of a two-stroke engine compared to a four-stroke unit make it currently the most widely used engine type for 50cc displacement 2-wheelers. This dominance is threatened by increasingly severe exhaust emissions legislation, forcing manufactures to develop their two-stroke engines to comply with the legislation. This paper describes a simple solution to reduce these harmful emissions in a cost effective manner, for a scooter application. The method of stratified scavenging is achieved by delivering the fuel into the rear transfer passage from a remote mechanical fuel metering device, operated by intake manifold pressure. Air only is delivered into the cylinder from the remaining transfer passages which are directed towards the rear transfer port, thus impeding the fuel from reaching the exhaust during the scavenging process.
Technical Paper

An Assessment of a Stratified Scavenging Process Applied to a Loop Scavenged Two-Stroke Engine

Stratified scavenging has been applied to two-stroke engines to improve fuel consumption and reduce exhaust emissions. To evaluation how this is achieved a stratified scavenging process was simulated using a three-gas single-cycle scavenging apparatus. The experiment simulated the fuel stream entering the rear transfer port of a five port cylinder and air streams entering the remaining ports. The scavenging efficiency and fuel trapping are calculated after the cycle by examining the cylinder contents. The design of the apparatus is particularly suited to investigating cylinder design changes during the prototype stage of engine development. A simulation of the stratified scavenging experiment using the Computational Fluid dynamics (CFD) code VECTIS, showed good correlation with measured results. The simulation provides a real insight into the cylinder flow behaviour of the separate fuel and air streams entering the cylinder.
Technical Paper

Emissions Performance of Pure Vegetable Oil in Two European Light Duty Vehicles

This programme involved the testing of two Euro II compliant diesel vehicles over the current European legislated drive cycle. The aim of the programme was to determine and compare the emissions of 100% virgin vegetable oil (VVO100) and a baseline UK marketplace Ultra Low Sulphur (ULSD) diesel fuel. A splash blend of 5% rapeseed methyl ester in ULSD (RME5) was also evaluated. Results of tests on RME5 showed that generally the effects on emissions compared to ULSD were small for regulated and most unregulated emissions. There was some evidence of a PM10 benefit for RME5 fuel. VVO100 showed large increases in HC (up to 250%) and CO emissions in both vehicles, as well as increases in polycyclic aromatic hydrocarbons (PAH), compared to ULSD. Effects on NOx and particulate were vehicle - specific.
Technical Paper

Lubricant Composition Impact on the Emissions from a European Heavy Duty Diesel Engine Equipped with a Diesel Particulate Filter

An Iveco Cursor 8 heavy-duty Diesel engine (7.8L, 6 cylinder) meeting Euro III emission regulations and equipped with a catalyst based passively regenerating Diesel particulate filter (CB-DPF) system, was used to investigate the impact of lubricant formulation on exhaust emissions. Measurements of both regulated and unregulated emissions were made during ESC and ETC cycles undertaken during a strictly controlled experimental protocol. Testing was carried out using ultra low sulphur, Swedish Class 1 Diesel fuel and a range of lubricant formulations. No significant effects of lubricant composition were observed on regulated gaseous emissions. However, the number of nucleation mode particles appeared to be both drive cycle and lubricant formulation dependent. Test methodology proved to be key; with engine, exhaust and dilution tunnel preconditioning and test order a major influence on ESC particle emissions.
Technical Paper

UK Particulate Measurement Programme (PMP): A Near US 2007 Approach to Heavy Duty Diesel Particulate Measurements - Comparison with the Standard European Method

This paper describes a practical approach used within the UK contribution to the UNECE PMP study in adopting some of the recommendations stated in the draft 2007 regulations for the measurement of particulate mass emissions from heavy-duty diesel engines in the US. This approach was named “2007PM” but the intention was to align rather than fully comply with the draft requirements for the US. In the PMP test work, four main changes were made to the standard European method of particulate emissions measurement (SPM). These were adopted as the 2007PM method. These were the application of a cyclone pre-classifier to 2007PM - with a 50% cut-size at 2.5μm, the use of a single 47mm filter rather than primary and back-up filters, close control of the filter face temperature to 47°C +/-5°C by heating of the dilution air and an increased filter face velocity. Measurements were predominantly made from aerosols generated by engines equipped with Diesel Particulate Filters (DPFs).
Technical Paper

Fuel and Lubricant Effects on Nucleation Mode Particle Emissions From a Euro III Light Duty Diesel Vehicle

The impact of lubricant sulphur and phosphorus levels on the formation of nucleation mode particles was explored in a light duty diesel vehicle operating over the New European Drive Cycle (NEDC). All measurements were undertaken using a Scanning Mobility Particle Sizer (SMPS), sampling from a conventional Constant Volume Sampler (CVS) system. Rigorous sampling system and vehicle conditioning procedures were applied to eliminate oil carry-over and nanoparticle artifact formation. An initial vehicle selection process was undertaken on vehicles representing three fuel injection strategies, namely; distributor pump, common rail and unit injector. The vehicles met Euro III specifications and were all equipped with oxidation catalysts. Idle and low load stability were key requirements, since these conditions are the most significant in terms of their propensity to generate nucleation mode particles.