Search Results

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.

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.

An adaptive air fuel ratio (AFR) control system has been implemented on a modern high performance fuel injected four cylinder engine. A pressure transducer in the combustion chamber is used to measure the indicated mean effective pressure (IMEP) for efficiency and cyclic variability feedback. The controller tunes the relative AFR, λ, in the range λ = 1 to λ = 1.5, to maximise the thermal efficiency in real time. The system adaptively accounts for changes in operating conditions such as ambient temperatures and user demands. The IMEP feedback allows the closed loop control system to update every few revolutions with short tune in times in the order of seconds. Open and closed loop test results are presented, demonstrating the incremental efficiency gains over fixed or mapped AFR control. The system continually adjusts the fuelling for maximum efficiency given its constraints and provides a basis for optimisation of future lean burn technologies.

This paper presents a combined experimental and numerical method for analysing energy flows within a spark ignition engine. Engine dynamometer data is combined with physical models of in-cylinder convection and the engine's thermal impedances, allowing closure of the First Law of Thermodynamics over the entire engine system. In contrast to almost all previous works, the coolant and metal temperatures are not assumed constant, but rather are outputs from this approach. This method is therefore expected to be most useful for lean burn engines, whose temperatures should depart most from normal experience. As an example of this method, the effects of normalised air-fuel ratio (λ), compression ratio and combustion chamber geometry are examined using a hydrogen-fueled engine operating from λ = 1.5 to λ = 6. This shows large variations in the in-cylinder wall temperatures and heat transfer with respect to λ.

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.

This paper studies autoignition characteristics and HCCI engine combustion of ketone fuels, which are important constituents of recently discovered fungi-derived biofuels. Two ketone compounds, 2,4-dimethyl-3-pentanone (DMPN) and cyclopentanone (CPN), are systematically investigated in the Sandia HCCI engine, and the results are compared with conventional gasoline and neat ethanol. It is found that CPN has the lowest autoignition reactivity of all the biofuels and gasoline blends tested in this HCCI engine. The combustion timing of CPN is also the most sensitive to intake-temperature (Tin) variations, and it is almost insensitive to intake-pressure (Pin) variations. These characteristics and the overall HCCI performance of CPN are similar to those of ethanol. In contrast, DMPN shows multi-faceted autoignition characteristics. On the one hand, DMPN has strong temperature-sensitivity, even at boosted Pin, which is similar to the low-reactivity ethanol and CPN.

This paper compares the performance of a small two cylinder, 430 cm3 engine which has been tested in a variety of normally aspirated (NA) and forced induction modes on 98-RON pump gasoline. These modes are defined by variations in the induction system and associated compression ratio (CR) alterations needed to avoid knock and maximize volumetric efficiency (ηVOL). These modes included: (A) NA with carburetion (B) NA with port fuel injection (PFI) (C) Mildly Supercharged (SC) with PFI (D) Highly Turbocharged (TC) with PFI The results have significant relevance in defining the limitations for small downsized spark ignition (SI) engines, with power increases needed via intake boosting to compensate for the reduced swept volume. Performance is compared in the varying modes with comparisons of brake mean effective pressure (BMEP), brake power, ηVOL, brake specific fuel consumption (BSFC) and brake thermal efficiency (ηTH).

The gaseous fuels, hydrogen and methane, are fuels that will likely be in adequate supply when crude oil sourced liquid fuels are scarce. These gases may he used directly in engines, which may need modification or could be used as feed stocks for liquid fuel synthesis. The energy efficiency of using methane and hydrogen in dedicated engines is compared with liquid fuelled engines. Hydrogen gives 6 3% improved efficiency and Methane 39% in city driving and Methane gives slightly improved power but Hydrogen fuel causes a 25% power loss compared with petrol. The storage of Methane in compressed or liquid form and Hydrogen in metal hydrides are compared. The overall efficiency of these gaseous fuel systems are compared, and fuel synthesis is included.

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.

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.

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.

Direct Injection (DI) is believed to be one of the key strategies for maximizing the thermal efficiency of Spark Ignition (SI) engines and meet the ever-tightening emissions regulations. This paper explores the use of Liquefied Petroleum Gas (LPG) liquid phase fuel in a 1.5 liter SI four cylinder gasoline engine with double over head camshafts, four valves per cylinder, and centrally located DI injector. The DI injector is a high pressure, fast actuating injector enabling precise multiple injections of the finely atomized fuel sprays. With DI technology, the injection timing can be set to avoid fuel bypassing the engine during valve overlap into the exhaust system prior to combustion. The fuel vaporization associated with DI reduces combustion chamber and charge temperatures, thereby reducing the tendency for knocking. Fuel atomization quality supports an efficient combustion process.

The hydrogen assisted jet ignition system (HAJI) replaces the spark plug of an Otto cycle engine and consists of a very small pre-chamber into which a hydrogen injector and spark plug are installed. The HAJI system allows stable combustion of very lean main-chamber hydrocarbon mixtures, leading to improved thermal efficiency and very much reduced NOx emissions. The current investigation focuses on the application of HAJI to a modern pent-roof, four valve per cylinder automotive engine. The development of a new hydrogen injection system and HAJI pre-chamber based on proprietary gasoline and diesel injectors is described. Results from injector and engine performance testing are presented in detail.

Non-reacting spray behaviors of the Engine Combustion Network “Spray G” gasoline fuel injector were investigated at flash and non-flash boiling conditions in an optically accessible single cylinder engine and a constant volume spray chamber. High-speed Mie-scattering imaging was used to determine transient liquid-phase spray penetration distances and observe general spray behaviors. The standardized “G2” and “G3” test conditions recommended by the Engine Combustion Network were matched in this work and the fuel was pure iso-octane. Results from the constant volume chamber represented the zero (stationary piston) engine speed condition and single cylinder engine speeds ranged from 300 to 2,000 RPM. As expected, the present results indicated the general spray behaviors differed significantly between the spray chamber and engine. The differences must be thoughtfully considered when applying spray chamber results to guide spray model development for engine applications.

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.

This paper presents experimental and computational results obtained on an in line, six cylinder, naturally aspirated, gasoline engine. Steady state measurements were first collected for a wide range of cam and spark timings versus throttle position and engine speed at part and full load. Simulations were performed by using an engine thermo-fluid model. The model was validated with measured steady state air and fuel flow rates and indicated and brake mean effective pressures. The model provides satisfactory accuracy and demonstrates the ability of the approach to produce fairly accurate steady state maps of BMEP and BSFC. However, results show that three major areas still need development especially at low loads, namely combustion, heat transfer and friction modeling, impacting respectively on IMEP and FMEP computations. Satisfactory measurement of small IMEP and derivation of FMEP at low loads is also a major issue.

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.

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.

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.

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.