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Technical Paper

Effects of Fuel Composition on D.I. Diesel Engine Particulates and Study of Oxygen-Enriched Diesel NO Formation

Diesel engines are used in heavy duty applications because of their high efficiency and reliability. However, their high diesel particulates and NOx emissions remain major concerns. An eight cylinder direct injection diesel engine was connected to a partial flow particulate sampling mini-dilution tunnel. Six different grades of diesel fuels were studied for their regular emissions as well as smoke and particulate emissions. Each fuel was tested at three engine speeds and full load. This paper presents the results of these tests which includes analysis of the effects of load, cetane number, 90% distillation temperature, and density for steady state conditions. A correlation was developed for converting smoke numbers in Hartridge Smoke Units (HSU) to the specific particulate emissions by evaluating results of all fuels tests. Another correlation was also developed for diesel particulates and NOx emissions trade-off.
Technical Paper

Concept Car - Life Cycle Energy Analysis

The Australian Concept Car was developed with support from a wide range of industry and government sectors. The estimated energy consumption over the vehicle life cycle is presented relative to a typical Australian Upper Medium Class car fleet. Several assumptions are made about the performance of the prototype car, when extrapolating it to a production counterpart for the comparison. Production methods are one area, covered by a survey of suppliers, and particularly in-service fuel use has had to be estimated using validated procedures. Uncertainties exist about the level of recycling at the end of the vehicles projected life after 225,000 km, leading to defined uncertainties. It is concluded that the concept car will have an energy reduction of 15-17.5% and the life cycle CO2 emissions will be reduced by a little less.
Technical Paper

Effects of a Wide Range of Drive Cycles on the Emissions from Vehicles of Three Levels of Technology

Exhaust emission tests were performed on a fleet of vehicles comprising a range of engine technology from leaded fuel control methods to closed loop three-way catalyst meeting 1992 U.S. standards but marketed in Australia. Each vehicle was tested to 5 different driving cycles including the FTP cycles and steady speed driving. Research had shown that for hot-start operation the major driving pattern parameters which influence fuel consumption and exhaust emissions are average speed and PKE (the positive acceleration kinetic energy per unit distance). Plots from analysis of micro-trip fuel use and emissions rates from the test cycles may be presented as contours in PKE. It follows that the micro trip emissions from a range of driving cycles including, regulated e.g. FTP city and unregulated e.g. LA-92, recently developed EPA cycles or from other cities e.g. Bangkok can be superimposed.
Technical Paper

Optimum Control of an S.I. Engine with a λ=5 Capability

HAJI (Hydrogen Assisted Jet Ignition) is an advanced combustion initiation system for otherwise standard S.I engines. It utilises the fluid mechanics of a turbulent, chemically active jet, combined with the reliability of spark igniting rich hydrogen mixtures. The result is an extremely robust ignition system, capable of developing power from an engine charged with air-fuel mixtures as lean as λ = 5. Experiments have been performed using a single cylinder engine operating on gasoline in the speed range of 600-1800 r/min. Data are presented in the form of maps which describe fuel efficiency, combustion stability and emissions with respect to load, speed, air-fuel ratio and throttle. The results are incorporated into a model of a known engine and vehicle and this is used to estimate performance over the Federal drive-cycle.
Technical Paper

Hydrocarbon Emissions from a HAJI Equipped Ultra-lean Burn SI Engine

Hydrogen Assisted Jet Ignition (HAJI) is a novel method of maintaining combustion stability during ultra-lean operation of conventional, homogeneously charged, SI engines. When operating with HAJI above λ=2, CO and NOx emissions fall to low levels while HC emissions rise to approximately double their stoichiometric value. HC emissions were investigated by operating a HAJI equipped, optically accessible, four-valve single cylinder engine at 600 r/min, wide open throttle (WOT), and from λ=1 to λ=2.4. A fast flame ionisation detector was used to collect real time hydrocarbon concentration data from behind one of the exhaust valves, inside the HAJI pre-chamber, and from near the combustion chamber wall. Flame images were also obtained. Exhaust port sampling shows that the HC concentration during blowdown and early exhaust is increased, but the concentration at the end of exhaust is decreased.
Technical Paper

A New Look at Oxygen Enrichment 1) The Diesel Engine

New concepts in oxygen enrichment of the inlet air have been examined in tests on two direct injection diesel engines, showing: significant reduction in particulate emissions (nearly 80% at full load), increased thermal efficiency if injection timing control is employed, substantial reductions in exhaust smoke under most conditions, ability to burn inferior quality fuels which is economically very attractive and achivement of turbo-charged levels of output with consequential benefits of increased power/mass and improved thermal efficiency. The replacement of an engine's turbocharger and intercooling system with a smaller turbocharger and polymeric membrane elements to supply the oxygen enriched stream should allow improved transient response. NOx emission remain a problem and can only be reduced to normally aspirated engine levels at some efficiency penalty.
Technical Paper

Giving Standard Diesel Fuels Premium Performance Using Oxygen-Enriched Air in Diesel Engines

Oxygen-enriched air supplied to a diesel engine has significant benefits in reducing the particulate emissions of all fuels tested. A Caterpillar 3208 direct injection diesel engine was modified to operate on a wide range of fuel grades including residual fuel oils with oxygen-enriched intake air. The paper focuses on four fuels, two fuels were regular automotive distillate fuels, the third was a low emission diesel fuel and the fourth fuel had high boiling point fractions. Comparison with less extensive work on residual fuel oil is also included. Smoke and particulates decrease by up to 94% at full load with 27% oxygen concentration. Performance with oxygen addition using regular fuels showed comparable smoke and particulates to a premium priced low emission fuel used specifically in underground mines.
Technical Paper

Factors Influencing Petrol Consumption as Determined from a Survey of the Australian Passenger Car Fleet

A survey of the on-road petrol consumption of Australian passenger cars provided data which has been analysed for effects on fuel consumption caused by features such as transmission type, vehicle inertia class, engine size, air conditioning presence and vehicle location. Results show that cars with automatic transmissions consistently have higher petrol consumption than manuals for all inertia classes - 15% higher in city conditions and 11% higher in highway conditions. There is also a penalty for automatic transmissions at most engine sizes, although the penalty is relatively larger for smaller engine capacities. Presence of air conditioning was found to increase petrol consumption by 13.5% on average, but the data did not allow the impact of frequency of use to be determined. Coastal driving conditions resulted in petrol consumption being 9.4% higher than for inland conditions, and cars driven in winter had 4.4% greater fuel consumption than cars driven in summer.
Technical Paper

Estimates of the Fuel Consumption and Exhaust Emissions of Light Trucks

A fleet of 17 utility, van and flat tray bodied trucks has been tested for fuel consumption and exhaust emissions over a range of drive cycles and steady state operating conditions. The influence of vehicle load on the results was included. For each vehicle the tractive force applied by the chassis dynamometer, on which testing was performed, was adjusted to match those found on the road using a new procedure. The fuel consumption results show a downward trend with model year (1.7% annum); about 30% higher petrol use compared with diesel; a cold start penalty of 3 L/100 km and over 2:1 variation for vehicles capable of identical transport task. Exhaust emissions from these rigid trucks were between 3 and 6 times greater than those of the passenger car fleet.
Technical Paper

Experimental and Computational Considerations of the Compression Ignition of Homogeneous Fuel-Oxidant Mixtures

The paper describes procedures for predicting the course of reaction and the onset of autoignition in homogeneous fuel-air mixtures, using detailed chemical kinetic data and considering hydrogen gas as a fuel. Experimental results from both a motored autoigniting engine and a pneumatically driven compression apparatus are then compared with computational predictions. It is shown that, depending on the reliability and completeness of the kinetic scheme employed, reasonably good agreement between computed and observed pressure development records can be obtained.
Technical Paper

Turbocharging for Fuel Efficiency

The arguments are given for the application of a 1.3 litre turbocharged spark ignition engine, as a substitute for a 2 litre normally aspirated engine as the power plant for a compact-sized car in the late 80’s. Three stages of the project leading to an optimised engine-turbocharger package are outlined. Achievement of Stage 1, leading to evaluation of a non-optimised configuration, will be reported. Description includes the use of a separately driven supercharger to define operating limits in the experimental variable matrix comprising compression ratio, boost pressure, EGR rate and spark retard at the knock limit. Computer programs for the optimising stages of the project are outlined. The current status of the project is reported, where, even at this early stage, fuel consumption reductions of 11-22% have been achieved under simulated urban driving conditions.
Technical Paper

Exploring the Charge Composition of SI Engine Lean Limits

In this paper the experimental performance of the lean limits is examined for two different types of engines the first a dedicated LPG high compression ratio 2-valve per cylinder engine (Ford of Australia MY 2001 AU Falcon) and the second a gasoline moderate compression 4-valve per cylinder variant of the same engine (Ford of Australia MY 2006 BF Falcon). The in-cylinder composition at the lean limit over a range of steady state operating conditions is estimated using a quasi-dimensional model. This makes it possible to take into account the effects of both residual fraction and fresh charge diluents (EGR and excess air) that allow the exploration of a modeled lean limit performance [1, 2]. The results are compared to the predictions from a model for combustion variability applied to the quasi-dimensional model operating in optimization mode.
Technical Paper

The Always Lean Burn Spark Ignition (ALSI) Engine – Its Performance and Emissions

This paper is based on extensive experimental research with lean burn, high compression ratio engines using LPG, CNG and gasoline fuels. It also builds on recent experience with highly boosted spark ignition gasoline and LPG engines and single cylinder engine research used for model calibration. The final experimental foundation is an evaluation of jet assisted ignition that generally allows a lean mixture shift of more than one unit in lambda with consequential benefits of improved thermal efficiency and close to zero NOx. The capability of an ultra lean burn spark ignition engine is described. The concept is operation at air-fuel ratios similar to the diesel engine but with essentially homogenous charge, although some stratification may be desirable. To achieve high thermal efficiency this engine has optimized compression ratio but with variable valve timing which enables reduction in the effective compression ratio when desirable.
Technical Paper

Lean Burn Performance of a Natural Gas Fuelled, Port Injected, Spark Ignition Engine

This paper presents a study of the performance of a lean burn, natural gas-fuelled, naturally aspirated, spark ignition engine for an E class vehicle. Engine performance and exhaust emissions (NO, CO, and UHC) data are first discussed. An energy balance of the engine operating at different loads and air-fuel ratios is then presented, and used to explain why engine efficiency varies with air-fuel ratio. Finally, the hot start drive cycle CO2e (CO2 equivalent) emissions are estimated for a vehicle with this engine. This shows a potential for significant reduction in vehicle greenhouse gas emissions compared to an equivalent gasoline-fuelled vehicle.
Technical Paper

Hydrogen as a Fuel in SI Engines - Towards Best Efficiency for Car Applications

The goal of hydrogen engine research is to achieve highest possible efficiency with low NOx emissions. This is necessary for the hydrogen car to remain competitive with the ever-improving efficiency of conventional fuel's use, to take advantage of the increased availability of hydrogen distribution for fuel cells and to achieve better range than battery electric vehicles. This paper examines the special problems of hydrogen engine combustion and ways to improve efficiency. Central to this are the effects of compression ratio (CR) and lambda (excess air ratio) and ignition system. The results demonstrate highest indicated thermal efficiency at ultra lean condition of lambda ≻ 2 and with central ignition. This need for this lean mixture is partly explained by the higher heat transfer losses.
Technical Paper

Optimization of All SI Engine Combustion Control and Related Events for Efficiency

There are two parts to achieving the optimization reported here. The development of an engine simulation model and an optimization algorithm. The engine performance is evaluated using a quasi-dimensional engine combustion model with sub models to incorporate friction, heat losses and abnormal combustion, that is knocking. After extensive search and development a new Particle Swarm Optimizer (PSO), has been developed. Optimization includes, for the first time, the search of discontinuous design variables. The input variables considered for this investigation are manifold air pressure, air-fuel ratio, spark timing, compression ratio, valve timing events including valve open duration, maximum valve lift and engine speed. This enables the identification of the maximum thermal efficiency at a given power output at any engine operating speed.
Technical Paper

The Systematic Evaluation of Twelve LP Gas Fuels for Emissions and Fuel Consumption

The effects on bi-fuel car exhaust emissions, fuel consumption and acceleration performance of a range of LPG fuels has been determined. The LPGs tested included those representing natural gas condensate and oil refineries' products to include a spectrum of C3:C4 and paraffiinic:olefinic mixtures. The overall conclusions are that exhaust emissions from the gaseous fuels for the three-way catalyst equipped cars tested were lower than for gasoline. For all the LPGs, CO2 equivalent emissions are reduced by 7% to 10% or more compared with gasoline. The cars' acceleration performance indicates that there was no sacrifice in acceleration times to various speeds, with any gaseous fuel in these OEM developed cars.
Technical Paper

Instantaneous Multi-Point versus Single-Point Measurement of Exhaust Port Hydrocarbons of Ultra Lean Mixture

A fast flame ionisation detector (FID) is able to measure the hydrocarbon (HC) concentration at a single point in the exhaust port. However, when sampling is conducted near the plane of the exhaust valve, these measurements are not representative of the entire port cross-section. This paper describes a multi-point extension to a standard fast FID probe, enabling the instantaneous measurement of a more representative HC concentration near the plane of the exhaust valve. Construction and use of the multi-point probe is discussed, and results are compared with standard single-point measurements.
Technical Paper

Compression Ratio Effects on Performance, Efficiency, Emissions and Combustion in a Carbureted and PFI Small Engine

This paper compares the performance, efficiency, emissions and combustion parameters of a prototype two cylinder 430 cm3 engine which has been tested in a variety of normally aspirated (NA) modes with compression ratio (CR) variations. Experiments were completed using 98-RON pump gasoline with modes defined by alterations to the induction system, which included carburetion and port fuel injection (PFI). The results from this paper provide some insight into the CR effects for small NA spark ignition (SI) engines. This information provides future direction for the development of smaller engines as engine downsizing grows in popularity due to rising oil prices and recent carbon dioxide (CO2) emission regulations. Results are displayed in the engine speed, manifold absolute pressure (MAP) and CR domains, with engine speeds exceeding 10000 rev/min and CRs ranging from 9 to 13. Combustion analysis is also included, allowing mass fraction burn (MFB) comparison.
Technical Paper

Optimized Design of a Cyclic Variability Constrained Lean Limit SI Engine at Optimum NOx and Efficiency Using a PSO Algorithm

In recent times new tools have emerged to aid the optimization of engine design. The particle swarm optimizer, used here is one of these tools. However, applying it to the optimization of the S.I. engine for high efficiency and low NOx emission has shown the preference of ultra lean burn strategy combined with high compression ratios. For combined power, efficiency and emissions benefits, there are two restricting factors, limiting the applicability of this strategy, knocking and cyclic variability. In the ultra lean region, knocking is not an important issue but the variability is a major concern. This paper demonstrates the application of a variability model to limit the search domain for the optimization program. The results show that variability constrains the possible gains in fuel consumption and emission reduction, through optimizing cam phasing, mixture and spark timing. The fuel consumption gain is reduced by about 11% relative.