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Technical Paper

Observation of the Effect of Swirl on Flame Propagation and the Derived Heat Release and Mass Burning Rates

A high speed research engine has optical access to over 80% of the combustion chamber volume through a piston with a quartz window. The engine has been used to study the effect of swirl on the spark-ignited combustion by means of high speed photography and analysis of combustion-time data. Results over the speed, swirl and mixture strength range show the flame travel derived from the pressure to agree with the measured flame travel to within 3% on average. Turbulent to laminar flame speed ratios as high as 45 occur under high swirl conditions. However it was not possible to find a predictive model which could explain the turbulent flame speed in terms of engine design variables.
Technical Paper

Turbocharging for the Fuel Efficient Urban Car

The arguments are given for the use of a 1.3 litre turbocharged spark ignition engine as a substitute for a 2 litre normally aspirated engine for late-80's compact cars. Descriptions of the three stages leading to an optimised engine-turbocharger package are described, together with details of the prototype TC engine manufacture and testing including supercharger tests to define operating limits. An outline of the optimising computer program is given, together with examples of computed camshaft designs giving significantly improved performance at low engine speeds. Some experimental results are given, including those of in-car testing which showed fuel consumption reductions of 12-22% over urban driving cycles.
Technical Paper

Spatial and Temporal Temperature Distributions in a Spark Ignition Engine Piston at WOT

Two coupled finite element analysis (FEA) programs were written to determine the transient and steady state temperature distribution in a spark ignition engine piston. The programs estimated the temperatures at each crank angle degree (CAD) through warm-up to thermal steady state. A commercial FEA code was used to combine the steady state temperature distribution with the mechanical loads to find the stress response at each CAD for one complete cycle. The first FEA program was a very fast and robust non-linear thermal code to estimate spatial and time resolved heat flux from the combustion chamber to the aluminum alloy piston crown. This model applied the energy conservation equation to the near wall gas and includes the effects of turbulence, a propagating heat source, and a quench layer allowing estimates of local, instantaneous near-wall temperature gradients and the resulting heat fluxes.
Technical Paper

Highly Turbocharging a Flow Restricted Two Cylinder Small Engine - Turbocharger Development

This paper describes the turbocharger development of a restricted 430 cm3 odd firing two cylinder engine. The downsized test engine used for development was specifically designed and configured for Formula SAE, SAE's student Formula race-car competition. A well recognised problem in turbocharging Formula SAE engines arises from the rules, which dictate that the throttle and air intake restrictor must be on the suction side of the compressor. As a consequence of upstream throttling, oil from the compressor side seal assembly is drawn into the inlet manifold. The development process used to solve the oil consumption issue for a Garrett GT-12 turbocharger is outlined, together with cooling and control issues. The development methodology used to achieve high pressure ratio turbocharging is discussed, along with exhaust manifold development and operating limitations. This includes experimental and modeling results for both pulse and constant pressure type turbocharging.
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

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.
Journal Article

A Comparative Study of a Spark Ignition Engine Running on Hydrogen, Synthesis Gas and Natural Gas

This paper presents an experimental, numerical and theoretical study of the performance of the same spark ignition engine running on four different gaseous fuels: hydrogen, two synthesis gases and natural gas. Measurements of the brake thermal efficiency, the combustion variability, the engine out emissions and the indicated, pumping and friction mean effective pressures are first presented, with particular interest placed on the lean burn performance. Combustion analysis is then undertaken, with the crank angle resolved in-cylinder turbulence and the flame propagation plotted on the so-called ‘Bradley diagram’ for turbulent premixed combustion. The loci of the combustion events on the Bradley diagram are then used to explain the observed, relative performance of the engine running on these four fuels.
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

HAJI Operation in a Hydrogen-Only Mode for Emission Control at Cold Start

The HAJI (Hydrogen Assisted Jet Ignition) system for S.I. engines utilises direct injection of small amounts of hydrogen to enhance the combustion of a variety of automotive fuels. Although not the primary purpose of HAJI, the hardware, once in place, also lends itself to the possibility of hydrogen-only running during a cold start. Cold-start simulations have been performed using a single cylinder engine. Results are presented, comparing hydrogen-only tests with standard HAJI operation and normal spark-ignition operation. HAJI and spark ignition tests were carried out with gasoline as the main-chamber fuel. Emission levels and combustion stability characteristics were recorded as the engine warmed up. The differences between the various fueling/ignition scenarios are presented and the implications for possible automotive applications are discussed in light of current and proposed emissions legislation.
Technical Paper

An Optical and Numerical Characterization of Directly Injected Compressed Natural Gas Jet Development at Engine-Relevant Conditions

Compressed natural gas (CNG) is an attractive, alternative fuel for spark-ignited (SI), internal combustion (IC) engines due to its high octane rating, and low energy-specific CO2 emissions compared with gasoline. Directly-injected (DI) CNG in SI engines has the potential to dramatically decrease vehicles’ carbon emissions; however, optimization of DI CNG fueling systems requires a thorough understanding of the behavior of CNG jets in an engine environment. This paper therefore presents an experimental and modeling study of DI gaseous jets, using methane as a surrogate for CNG. Experiments are conducted in a non-reacting, constant volume chamber (CVC) using prototype injector hardware at conditions relevant to modern DI engines. The schlieren imaging technique is employed to investigate how the extent of methane jets is impacted by changing thermodynamic conditions in the fuel rail and chamber.
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

Parametric Investigations into Combustion of Seed Oils in a Diesel Engine

A thermodynamic model has been employed to study the effect of changing injection timing, spray angle, fuel density, fuel viscosity, chemical reaction rate constants and air entrainment on the combustion performance of seed oils and their methyl esters in an open chamber diesel engine. It is shown that the most important valuables affecting the performance are fuel density and fuel viscosity. It is deduced that modification of these physical properties can lead to substantial improvement in the combustion performance of the seed oils.
Technical Paper

Development of a 430cc Constant Power Engine for FSAE Competition

This paper describes the design and development of an engine with constant power for SAE's student Formula race-car competition, allowing the avoidance of gear shifting for much of the Autocross event. To achieve constant power for over 50% of the speed range, turbocharging was adopted with a boost pressure ratio of 2.8 at mid-range speeds and applied to an engine capacity of 430 cc. This engine was specifically designed and configured for the purpose, being a twin cylinder in-line arrangement with double overhead camshafts. Most of the engine components were specially cast or machined from billets. The capacity was selected to minimise frictional losses and thus increase delivered power along with dry sump lubrication and a three speed gear box. The engine manifolds and plenums were designed using a CAE application and proved to be well suited to the task resulting in excellent agreement between predicted and actual performance.
Technical Paper

Why Liquid Phase LPG Port Injection has Superior Power and Efficiency to Gas Phase Port Injection

This paper reports comparative results for liquid phase versus gaseous phase port injection in a single cylinder engine. It follows previous research in a multi-cylinder engine where liquid phase was found to have advantages over gas phase at most operating conditions. Significant variations in cylinder to cylinder mixture distribution were found for both phases and leading to uncertainty in the findings. The uncertainty was avoided in this paper as in the engine used, a high speed Waukesha ASTM CFR, identical manifold conditions could be assured and MBT spark found for each fuel supply system over a wide range of mixtures. These were extended to lean burn conditions where gaseous fuelling in the multi-cylinder engine had been reported to be at least an equal performer to liquid phase. The experimental data confirm the power and efficiency advantages of liquid phase injection over gas phase injection and carburetion in multi-cylinder engine tests.
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.
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

Optimizing the Design of the Air Flow Orifice or Restrictor for Race Car Applications

Several race car competitions seek to limit engine power through a rule that requires all of the engine combustion air passes through a hole of prescribed diameter. As the approach and departure wall shapes to this hole, usually termed orifice or restrictor are not prescribed, there is opportunity for innovation in these shapes to obtain maximum flow and therefore power. This paper reports measurements made for a range of restrictor types including venturis with conical inlets and outlets of various angles and the application of slotted throats of the ‘Dall tube’ type. Although normal venturis have been optimized as subsonic flow measuring devices with minimum pressure losses, at the limit the flow in the throat is sonic and the down stream shocks associated with flow transition from sub-sonic to sonic are best handled with sudden angular changes and the boundary layer minimized by the corner slots between the convergent and divergent cones.
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

Design and Development of a Gasketless Cylinder Head / Block Interface for an Open Deck, Multi Cylinder, Highly Turbocharged Small Engine

This paper describes the design and development of a gasketless interface, which was used successfully to couple an aluminium cylinder head to an open deck design cylinder block. The cylinder block was manufactured from aluminium, featuring shrink fit dry cast iron liners. Extensive CAE modelling was employed to implement the gasketless interface and thus avoid using a conventional metal or fiber based cylinder head gasket. The engine was specifically designed and configured for the purpose, being a 430 cm3, highly turbocharged (TC) twin cylinder in-line arrangement with double overhead camshafts and four valves per cylinder. Most of the engine components were specially cast or machined from billets. The new design removed the conventional head gasket and relied on the correct amount of face pressure generated by interference between the cylinder head and block to seal the interface. This had advantages in improving the structural integrity of the weak open deck design.
Technical Paper

Highly Turbocharging a Restricted, Odd Fire, Two Cylinder Small Engine - Design, Lubrication, Tuning and Control

This paper describes the mechanical component design, lubrication, tuning and control aspects of a restricted, odd fire, highly turbocharged (TC) engine for Formula SAE competition. The engine was specifically designed and configured for the purpose, being a twin cylinder inline arrangement with double overhead camshafts and four valves per cylinder. Most of the engine components were specially cast or machined from billets. A detailed theoretical analysis was completed to determine engine specifications and operating conditions. Results from the analysis indicated a new engine design was necessary to sustain highly TC operation. Dry sump lubrication was implemented after initial oil surge problems were found with the wet sump system during vehicle testing. The design and development of the system is outlined, together with brake performance effects for the varying systems.