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In recent years, improvements in the fuel economy and exhaust emission performance of internal combustion engines have been increasingly required by regulatory agencies. One of the salient concerns regarding general purpose engines is the larger amount of CO emissions with which they are associated, compared with CO emissions from automobile engines. To reduce CO and other exhaust emissions while maintaining high fuel efficiency, the optimization of total engine system, including various design parameters, is essential. In the engine system optimization process, cycle simulation using 0-D and 1-D engine models are highly useful. To define an optimum design, the model used for the cycle simulation must be capable of predicting the effects of various parameters on the engine performance. In this study, a model for predicting the performance of a general purpose SI (Spark Ignited) engine is developed based on the commercially available engine simulation software, GT-POWER.

Advanced Vehicle Technologies (AVT), a Ballarat Australia based company, has developed the World's first diesel to 100% LPG conversion for heavy haul trucks. There is no diesel required or utilized on the trucks. The engine is converted with minimal changes into a spark ignition engine with equivalent power and torque of the diesel. The patented technology is now deployed in 2 Mercedes Actros trucks. The power output in engine dynamometer testing exceeds that of the diesel (in excess of 370 kW power and 2700 Nm torque). In on-road application the power curve is matched to the diesel specifications to avoid potential downstream power-train stress. Testing at the Department of Transport Energy & Infrastructure, Regency Park, SA have shown the Euro 3 truck converted to LPG is between Euro 4 and Euro 5 NOx levels, CO2 levels 10% better than diesel on DT80 test and about even with diesel on CUEDC tests.

The characteristics of the combustion process in an improved design of a novel spark ignition engine studied by means of Computational Fluid Dynamics are presented. The engine is designed to work at low average combustion temperatures to achieve very low NOx emissions. The engine is a two-stroke, two piston in-line engine. The main combustion occurs in four combustion pre-chambers that have an annular shape with a nozzle on the side facing the cylinder. Fuel is directly injected into the pre-chambers by using high-pressure fuel injectors. A progressive burning process is expected to keep the flame inside the pre-chambers while the fast ejection of combustion products should produce effective mixing with the cold air in the cylinder. This fast dilution should guarantee a temperature drop of the combustion products thus reducing the formation of NOx via a thermal path.

Homogeneous Charge Compression Ignition (HCCI) is good method to be higher efficiency and to reduce NOx emission and particular matter together than conventional SI combustion engine. But HCCI depends on chemical reaction of fuel and air mixture. So controlling of ignition timing is difficult, and HCCI is high THC and CO emissions because temperature can't reach the enough temperature to reduce those. In this study, we investigated factor for auto ignition timing and combustion completion on n-Butane/Air mixture by a two-stroke HCCI engine. Auto Ignition temperature are known to be decided by fuel(1), for n-Butane, the temperature was 1150±30K. And as we researched combustion completion from In-cylinder gas temperature, increasing In-cylinder gas temperature caused high combustion efficiency and low THC, CO emissions.

The cooperative road tests carried out during 1941 have added considerable information and experience to that already existing on the subject of road detonation testing. Extensive data were obtained on the fuel requirements of the 1940 and 1941 models of the three most popular cars. Corresponding data were obtained on the knocking characteristics of current gasolines representing the bulk of the sales volume in various parts of the United States. On account of large variations in octane-number requirement among different cars of the same make - due to differences in ignition timing, combustion-chamber deposit, and other causes - and on account of variations in commercial gasolines, it has been necessary to use statistical methods of analysis in the appraisal of fuel and engine relationships. These methods of analysis have been applied in a number of ways, and have proved very useful.

The conversion design strategy, and emissions and performance results for a dedicated propane, vapour injected, 1995 Dodge Dakota truck are reported. Data is obtained from the University of Waterloo entry in the 1997 Propane Vehicle Challenge. A key feature of the design strategy is its focus on testing and emissions while preserving low engine speed power for drivability. Major changes to the Dakota truck included the following: installation of a custom shaped fuel tank, inclusion of a fuel temperature control module, addition of a vaporizer and a fuel delivery metering unit, installation of a custom vapour distribution manifold, addition of an equivalence ratio electronic controller, inclusion of a wide range oxygen sensor, addition of an exhaust gas recirculation cooler and installation of thermal insulation on the exhaust system. A competition provided natural gas catalyst was used.

As part of the 1997 Propane Vehicle Challenge, a team of twelve UTEP students converted a 1996 Dodge Grand Caravan with a 3.3 L V6 engine to dedicated Liquefied Petroleum Gas (LPG) operation according to the 1997 Propane Vehicle Challenge (PVC) competition rules (16). The 1997 UTEP team developed an LPG liquid phase port fuel injection (LPP-FI) system for the minivan. The UTEP design strategy combines simplicity and sound engineering practices with the effective use of heat resistant materials to maintain the LPG in the liquid phase at temperatures encountered in the fuel delivery system. The team identified two options for fuel storage with in-tank fuel pumps. The competition vehicle incorporates a five-manifold eight inch diameter Sleegers Engineering LPG tank fitted with a Walbro LPTS in-tank pump system, providing a calculated range of 310 city miles and 438 highway miles.

Abstract In recent years, lean-burn gasoline Spark-Ignition (SI) engines have been a major subject of investigations. With this solution, in fact, it is possible to simultaneously reduce NOx raw emissions and fuel consumption due to decreased heat losses, higher thermodynamic efficiency, and enhanced knock resistance. However, the real applicability of this technique is strongly limited by the increase in cyclic variation and the occurrence of misfire, which are typical for the combustion of homogeneous lean air/fuel mixtures. The employment of a Pre-Chamber (PC), in which the combustion begins before proceeding in the main combustion chamber, has already shown the capability of significantly extending the lean-burn limit. In this work, the potential of an ultralean PC SI engine for a decisive improvement of the thermal efficiency is presented by means of numerical and experimental analyses.

The paper presents a combined experimental and numerical investigation of a small unit displacement two-stroke SI engine operated with gasoline and Natural Gas (CNG). A detailed multi-cycle 3D-CFD analysis of the scavenging process is at first performed in order to accurately characterize the engine behavior in terms of scavenging patterns and efficiency. Detailed CFD analyses are used to accurately model the complex set of physical and chemical processes and to properly estimate the fluid-dynamic behavior of the engine, where boundary conditions are provided by a in-house developed 1D model of the whole engine. It is in fact widely recognized that for two-stroke crankcase scavenged, carbureted engines the scavenging patterns (fuel short-circuiting, residual gas distribution, pointwise lambda field, etc.) plays a fundamental role on both of engine performance and tailpipe emissions.

The paper presents a 1D-3D numerical model to simulate the scavenging and combustion processes in a small-size spark-ignition two-stroke engine. The engine is crankcase scavenged and can be operated with both gasoline and Natural Gas (NG). The analysis is performed with a modified version of the KIVA3V code, coupled to an in-house developed 1D model. A time-step based, two-way coupled procedure is fully described and validated against a reference test. Then, a 1D-3D simulation of the whole two-stroke engine is carried out in different operating conditions, for both gasoline and NG fuelling. Results are compared with experimental data including instantaneous pressure signals in the crankcase, in the cylinder and in the exhaust pipe. The procedure allows to characterize the scavenging process and quantify the fresh mixture short-circuiting, as well as to analyze the development of the NG combustion process for a diluted mixture, typically occurring in a two-stroke engine.

A novel diagnostic technique named a “Tracer-Producing LIF technique” which enables 2-dimensional measurement of an internal EGR within an engine cylinder, has been developed. The main feature of this technique is the utilization of a fuel additive that does not itself emit an LIF signal by irradiation of UV-light but whose combustion products radiate strong LIF emissions by UV-light irradiation. Internal EGR behaviors can be measured by observing LIF images that are excited by a UV-laser sheet. Firstly, principles of this technique were confirmed and fuel additives were selected. Then, the “Tracer-Producing LIF technique” was applied to an optically accessible single-cylinder gasoline engine in which the entire pent-roof area can be observed from the side of the engine. The internal EGR behaviors were measured through the entire engine cycle, from intake to exhaust.

A three-dimensional model for premixed- charge naturally-aspirated rotary engine combustion is used to identify combustion chamber geometries that could lead to increased indicated efficiency for a lean (equivalence ratio =0.75) natural gas/air mixture. Computations were made at two rpms (1800 and 3600) and two loads (approximately 345 Kpa and 620 Kpa indicated mean effective pressure). Six configurations were studied. The configuration that gave the highest indicated efficiency has a leading pocket with a leading deep recess, two spark plugs located circumferentially on the symmetry plane (one after the minor axis and the other before), a compression ratio of 9.5, and an anti-quench feature on the trailing flank.

Three-dimensional transient simulation was performed and an autoignition model was implemented to predict knock occurrence and autoignition site in a heavy-duty liquefied petroleum gas (LPG) engine. A flame area evolution (FAE) premixed combustion model was applied to simulate flame propagation. Engine experiments using a single-cylinder research engine were performed to calibrate the reduced kinetic model and to verify the result of this modeling. A pressure transducer and a head-gasket type ion-probe circuit board were installed to detect knock occurrence, flame arrival angle, and autoignition site. The simulation result shows good agreement with engine experiments. It also provides much information about in-cylinder phenomena and some ways to reduce knocking tendency. This knock simulation can be used as a development tool of engine design.

GHP which, is the heat pump system for an air conditioning, is directly driven the compressor by a small gas engine. The NOx was reduced 70% less than a conventional gas engine with improvement of thermal efficiency. The combustion chamber shape using strong squish flow is improved in order that the pattern of a heat release is changed to be suitable. Because the relation between NOx and the thermal efficiency is the trade off relation, the air fuel ratio and the ignition timing must be precisely controlled. Detecting the change of the Pi variation calculated from the engine speed variation can control the air fuel ratio.

Many applications of liquefied petroleum gas (LPG) to commercial vehicles have used their corresponding diesel engine counterparts for their basic architecture. Here a review is made of the application to commercial vehicle operation of a robust 4 L, light-duty, 6-cylinder in-line engine produced by Ford Australia on a unique long-term production line. Since 2000 it has had a dedicated LPG pick-up truck and cab-chassis variant. A sequence of research programs has focused on optimizing this engine for low carbon dioxide (CO₂) emissions. Best results (from steady state engine maps) suggest reductions in CO₂ emissions of over 30% are possible in New European Drive Cycle (NEDC) light-duty tests compared with the base gasoline engine counterpart. This has been achieved through increasing compression ratio to 12, running lean burn (to λ = 1.6) and careful study (through CFD and bench tests) of the injected LPG-air mixing system.

In Sports Motorcycles category, fuel injection systems have been employed more popularly in recent years, and we have been also developing motorcycles introducing fuel injection systems in the category of 600cc - 1400cc displacement. Sports Motorcycles need to be controlled in a wide range from idling to over 10000rpm. Better throttle response, high power and low fuel consumption are also required. Therefore, adding to optimizations of inlet system layout, fuel injection amount, injection timing and ignition timing, the authors have applied to some models electric control devices such as SDTV (Dual Throttle Valve System) that controls intake air amount with secondary throttle valve located upstream of primary throttle valve and SET (Exhaust Tuning System) that controls exhaust pressure by opening angle of an exhaust valve installed in an exhaust pipe to improve the torque characteristics.

Active prechamber combustion systems for SI engines represent a feasible and effective solution in reducing fuel consumption and pollutant emissions for both marine and ground heavy-duty engines. However, reliable and low-cost numerical approaches need to be developed to support and speed-up their industrial design considering their geometry complexity and the involved multiple flow length scales. This work presents a CFD methodology based on the RANS approach for the simulation of active prechamber spark-ignition engines. To reduce the computational time, the gas exchange process is computed only in the prechamber region to correctly describe the flow and mixture distributions, while the whole cylinder geometry is considered only for the power-cycle (compression, combustion and expansion). Outside the prechamber the in-cylinder flow field at IVC is estimated from the measured swirl ratio.