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The ideal performance of a small engine requires changeable intake pipeline volume while engine speed varies, as been recognized in former study. However, an intake pipeline with changeable volume is tremendously difficult to achieve. This paper presents an innovative three-pipeline model by experimental design optimization to simulate a simple changeable volume pipeline. The primary goals contain the promotion of lower-speed torque, the fuel consumption; emissions of CO and HC are expected to reduce simultaneously. The optimum diameters, lengths of three pipelines, and the proper timing of switching three valves among lower speed pipe and higher speed pipe can be obtained by proposed integration method

This paper examines whether regional characteristics can have a significant impact on the engine sizes of the car fleet in Ireland. Disposable income is found to be the dominant factor in determining the purchase probabilities of car engine size, but in addition a combination of high population density and the availability of rail transport can reduce the demand for medium and large engine sized vehicles, as well as for new cars generally. Bus services, however, only serve as a substitute for small engine cars. Other funder Environmental Protection Agency

The Semi-Direct Injection (SDI) system has been shown to improve small engine efficiency and exhaust by utilizing a lean burn method. In order to better understand how to more readily utilize the control systems in SDI engine, the real-time operation of an SDI engine was modeled. A charging model was developed by using a filling-and-emptying model to simulate air exchange in an engine, including varying the intake manifold structure. A single-zone model was applied to a combustion model and the effects of air/fuel ratio and swirl ratio on combustion duration were also considered. The calculated results of the intake manifold pressure, heat release rate, and cylinder pressure were compared with the experimental data. The results of this study show that this modeling process approximates reality.

Since recently exhaust gas regulation for a non-road small engine as well as commercial vehicle engine has been enforced, a carburettor of a small engine should be replaced by an electronic fuel injection system. In this study, the spray characteristics of the 400cc gasoline small engine injector has been experimentally analyzed. Based on the experimental results, suitable injector for the small engine has been selected. Through the test rig measuring spray mass distribution, fuel distribution characteristics of 3 hole- and 6 hole-injector has been analyzed. Through the visualization equipment, injector spray angle, penetration length and spray width have been measured and analyzed. Considering spray characteristics and stability, 6 hole-injector is selected for the 400cc gasoline small engine.

One dimensional simulation model of an EFI small engine has been developed based on the commercial small engine. Newly developed simulation model has been evaluated comparing with the experimental results to check the validity. Simulation result shows very good agreement having margin of error of 3 percentage compared with experimental torque and power values. Also, to improve the small engine performance, the influence of the intake valve timing and duration on the engine performance has been analyzed using the simulation model.

The EFI small engine has been redesigned and manufactured based on a commercial small engine with a carburettor. Performance development of the EFI small engine has been conducted to optimize the operating conditions. Maximum torque and power were 12.56Ps and 25.4Nm, respectively, that were equivalent with carburettor type engine. Brake specific fuel consumption of the EFI small engine has been improved 17% on average compared with that of base small engine with a carburettor. By conducting KG2-6 mode test,HC+NOx was 7.46g/kWh that satisfied EPA Phase 3 regulation. THC has been reduced 41% on average, but NOx has been increased 3.5 times on average due to the improved thermal efficiency.

By the analysis and comparison of LPG motorcycle and LPG automobile, the similarities and differences of them are expounded. Based on the components and structure of LPG automobile fuel system, the LPG motorcycle gas phase positive pressure fuel system and LPG motorcycle liquid phase positive pressure fuel system are designed, and the advantages and disadvantages are analyzed and compared. The engine cylinder cover is enhanced and setted maze channels, so the liquid state LPG can be pre-heated using the remaind head of engine before enter the decompressor, the frozen of decompressor is solved effectively. The road trial and testing show that the LPG motorcycle liquid positive pressure fuel system is simple in structure, stabilize and reliable, the comprehensive performance can satisfied the demand of national standard.

Liquefied Petroleum Gas (LPG) has become an interesting topic in the automotive industry to develop the engines with clean emission characteristics. The usage of gasoline as a fuel to power up the vehicle will contribute to the heavy environmental problem. A single cylinder four-stroke spark ignition (SI) engine that fueled by LPG and gasoline are used to predict and analyze the combustion process in the cylinder. A zero dimensional models are most suitable analytical models for engine cycle simulation. The simulation program has been developed using MATLAB software by implementing a single-zone thermodynamic model. The first law of thermodynamics is applying into this model and Annand's model was used to compute the convection and radiation of heat transfer within the cylinder. The engine performance parameters computed including the in-cylinder pressure, gas temperature, net heat release, mass fraction burn, brake power, torque, indicated specific fuel consumption. Then, exhaust emission in the cylinder was predicted by the formation of emission model. The results of engine performance are compared between gasoline and LPG as a fuel. Results show LPG engine has contributed to the lower HC and NOx emissions compared to gasoline. It proved that the development of simulation program is useful to calculate the engine performance at different operating points.

The vacuum degree characteristics of venturi tube mixer are researched, and the factors affect the mixer vacuum degree and air-fuel ratio are analyzed. A new mixer is developed with the structural characteristics are the double channel and respectively control. The bench test and actual road test of the matching performance between the new designed mixer and LPG engine are conducted, and the test results show that the integrated matching performance is good, and possess the advantages of simple structure, convenient operation, reliable control. The mixer can control the air-fuel ratio simple and reasonable, so as to achieve good economy and emission performance under the premise of the LPG engine has adequate dynamic property, which according with the state development strategy of promoting low carbon economy.

This paper develops an intake two-pipeline model on a 125 cc single engine including the effects of engine torque (T), fuel consumption (FC) and both CO and HC emission. Those four performances in prescribed speed range were constructed by the response surface method. The formal design of experiment has been utilized to examine the significances and characteristics of interrelated parameters. A proposed engineering design optimization simultaneously treats four performances with weighting strategy so that the optimum two-pipeline diameters, lengths, and the appropriate timing of switching low-speed pipe to high-speed pipe can be obtained. The presented integration process of experimental design optimization offers an applicable process and technique for small engine and can apply to other mechanical product development.

To develop gasoline engine fuel pump, it is needed to measure the rotational speed of the pump. In general, because gasoline fuel pump is submerged in the fuel tank, it is difficult to measure the rotational speed directly. Currently, there are two popular methods measuring the rotational speed. One of them is using a piezoelectric accelerometer, and the other is using a current sensor. Originally, a piezoelectric accelerometer had been applied to measure the frequency of the motor vibration. A current sensor is measuring current frequency of the commutator slot. In this study, both the piezoelectric accelerometer and the current sensor have been applied on the fuel pump to calculate the rotational speed at the same time. As a result, the current sensor delivered highly accurate rotational speed information compared with that of the piezoelectric accelerometer. Especially, low rotational speed region, the current sensor shows very robust measuring characteristics. To measure the rotational speed within 1% error, the piezoelectric accelerometer needs to be set with less then 0.5Hz datum storage interval, and the current sensor needs to be set with less then 2.0Hz datum storage interval.

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To develop the small engine used for the wireless control helicopter, a very high power density source will be required. The rotary engine (RE) is advantageous in the points such as a volume of the engine, the exhaust gas emissions, and the vibrations. In this research, in order to develop the small RE, the design of the combustion chamber was reviewed. Additionally, the method of the surface treatment of the rotor housing was investigated by the friction wear test to enable the material substitution for aluminum matrix composites. The friction wear tests of composite materials, the Cr and Ni-plated material were conducted. As a result, the sample with the most excellent abrasion resistance was the composite material reinforced with Al2O3 fibers. The wear-loss of this composite material was 1/10 compared with the Ni-plated material. This composite material formed oil pockets between the fiber and the matrix, and a friction coefficient fell below 0.1. Then, the aluminum rotor housing reinforced partially by Al2O3 fiber was fabricated using a low-pressure infiltration method. The maximum power of the small RE (1 rotor, 30 cc) which built in this housing reached about 5 PS in the range from 13,000 to 15,000 rpm. The inside of the housing used composite materials was not damaged even after 30 hours. On the other hand, the flaking off part was observed on the inside part in the case with the housing used the Ni-plated material. Additionally, the output and the torque of the RE made of composite materials were higher than those of the Ni-plated material. This was considered because the friction coefficient of composite materials was lower than that of the Ni-plated material. Finally, the small unmanned helicopter equipped with RE succeeded in a stable flight.

Because of operating environment, the intake system of the small engine needs a serious design consideration. To capture oil particles from the blow-by gas, a grid of the intake system had been applied, but it has very low capturing efficiency and high manufacturing cost. To improve system performance, a new intake system has been developed using computational technique. The grid has been removed and the location of the blow-by hall has been re-designed. Total efficiency capturing oil particles has been improved about 5 times compared with that of previous model with the grid. By removing the grid, approximately 10% of the total manufacturing cast has been reduced. Key Words : Intake System, Small Engine, Engine Performance, Air Filter * 교신저자 : 박성영(sungyoung@kongju.ac.kr)접수일 09년 06월 24일 수정일 (1차 09년 10월 07일, 2차 09년 11월 04일) 게재확정일 09년 11월 12일 1. 서론 최근 들어 레져 및 이동의 편의성으로 인한 소형엔진의 사용이 보편화되고 있다. 소형엔진은 휴대 및 이동이 용이하도록 소형화 및 경량화가 주된 기술을 이루고 있으며, 저가의 기존기술을 사용하여 일상생활에 널리 보급되어 있다[1]. 공사 현장이나 실생활에서 널리 활용되는 소형엔진은 엔진이 운전되는 장소에서 먼지와 같은 이물질을 포함한 공기를 필수적으로 사용하게 된다. 따라서 엔진의 구동 및 운전 조건의 측면에서는 매우 열악한 환경에서 엔진이 작동되어야 한다. 이러한 소형엔진의 주 운전 조건을 고려해 볼 때 엔진으로 유입되는 흡입공기를 정화하는 흡기시스템은 엔진의 설계에서부터 고려되어야할 매우 중요한 설계인자이다[2]. 엔진의 흡기시스템은 연료의 연소를 위하여 엔진의 연소실에 공기를 공급하는 장치이다. 특히 소형엔진의 흡기시스템은 그 구조적인 단순화로 인하여 흡기필터를 포함한 흡기구가 엔진 흡기계의 대표적인 역할을 담당하고 있다. 소형엔진의 흡기 시스템은 공기의 흡입량에 직접적으로 관계되며, 흡입되는 공기는 연료의 분무성능에 영향을 미치게 된다.소형엔진의 흡기계 시스템은 케이스, 커버, 필터류 등으로 구성되며, 이들의 성능은 필터의 효율과 흡입되는 공기량에 따라 결정된다. 또한 흡기시스템에는 크랭크실로부터 유입되는 블로바이 가스에서 오일입자를 제거하는 장치가 설계되어있다. 이것은 그리드 또는 충돌판으로 구성되어 있다. 소형

Small, handheld two-stroke engines used for lawn and garden work (e.g., string trimmers, leaf blowers, etc.) can emit a variety of potentially toxic carbonaceous air pollutants. Yet, the emissions effluents from these machines go largely uncharacterized, constraining the proper development of human exposure estimates, emissions inventories, and climate and air quality models. This study samples and evaluates chemical pollutant emissions from the dynamometer testing of six small, handheld spark-ignition engines—model years 1998–2002. Four oil–gas blends were tested in each engine in duplicate. Emissions of carbon dioxide, carbon monoxide, and gas-phase hydrocarbons were predominant, and the PM emitted was organic matter primarily. An ANOVA model determined that engine type and control tier contributed significantly to emissions variations across all identified compound classes; whereas fuel blend was an insignificant variable accounting for

The small annular combustor of a micro gas turbine fueled with methane is investigated experimentally and numerically in order to improve the overall efficiency of the small engine. The CFD analysis of the combustor relies on a newly developed low-Reynolds number turbulent combustion model based on the Eddy Dissipation Concept (EDC) and provides important insight about the turbulent flow pattern, flame shape, position and optimal flame anchoring. For the experimental observation, a model combustor, representing 120 degrees of the original annular combustor, is fabricated, which enables us to visualize internal flow. The burning area in the combustion chamber moves to downstream with increase of air flow rate. At full-load, some fuel remains at the combustion chamber exit. Moreover, temperatures are measured and compared with the numerical simulations. The results shown here will form the basis for future optimization of the micro gas turbine with minimal or no increase in combustor pressure loss.

Small internal combustion engines, particularly those ranging in power from 1 kW to 10 kW, propel many remotely piloted aircraft (RPA) platforms that play an increasingly significant role in the Department of Defense. Efficiency of these engines is low compared to conventional scale engines and thermal losses are a significant contributor to total energy loss. Existing thermal energy loss models are based on data from much larger engines. Whether these loss models scale to the engine size class of interest, however, has yet to be established. The Small Engine Research Bench (SERB) was used to measure crank angle resolved gas temperature inside the combustion chamber of a small internal combustion engine (ICE). A 55 cc, twostroke, spark-ignition ICE was selected for this study. The engine was modified for optical analysis using sapphire rods 1.6 mm in diameter on opposite sides of the combustion chamber. The engine modification was found to have no measurable impact on indicated mean effective pressure or heat rejection through the cylinder. FTIR absorption thermometry was used to collect mid-infrared absorption spectra. The FTIR was allowed to scan continuously while simultaneously recording the scanning mirror position and crank angle associated with each data point, then data was re-sorted by crank angle. Measured spectra were compared with lines generated using CDSD-4000 and HITEMP line list databases. The line of best fit corresponded to the mean gas temperature through the combustion chamber. In this way temperature was determined as a function of crank angle for three operating conditions: 4,300, 6,000, and 7,500 revolutions per minute, all at wide open throttle. High cycle-to-cycle variation in the regions of combustion and gas exchange degraded temperature measurements at the affected crank angles. Future research will attempt to improve signal to noise in these measurements.

The present age of unmanned aerial vehicles demands small and highly efficient propulsion techniques. This is the motivation for the present work. The Advanced Propulsion Outreach Program sponsored by the Air Force Research Laboratory challenged teams at universities across the country to redesign components of the JetCat P90 gas turbine engine for improvements in efficiency, thrust, weight, and specific fuel consumption. The team at the University of Cincinnati was assigned the inlet/compressor section and elected to redesign the diffuser for an improvement in total pressure loss. Parametric design of turbomachinery components has been an area explored heavily at UC in recent years and this provided an opportunity to validate design capability. An automated optimization routine is paired with a parametric design tool. A multivariable optimization of the diffuser geometry led to a final design showing the potential for drastic performance improvements over the original JetCat diffuser. The final design will be tested in a full engine configuration at the Small Engine Research Laboratory (SERL) at Wright Patterson Air Force Base.

To fulfil actual customer demands, R&D departments have to solve a trade-off between increasing power and torque demands in agriculture engine applications and to install the whole engine in the existing small engine package environment. Based on the increasing size of agricultural holdings, combined with the demand to reduce operating costs as much as possible, this has led to a requirement for tractors with high power and high torque, but which remain compact, highly versatile and highly manoeuvrable. To achieve good tractor manoeuvrability, a very compact package is required. In particular the width of the engine which is limited by the steering lock. The main focus subsequently is on operating costs. Both require a high power density. In addition to these demands, there is a high service life expectation of at least 10,000 hours. As well as a need for high power density, the tractor must be capable of operating continuously under a wide range of conditions. In order to meet these demands, dual-stage turbo charging technology with intermediate charge air cooling has been chosen. The following article will describe the segment-specific demands and the engine technology, including the special challenges for the agricultural application. Later on the validation process for such a special application product will be described.

Small displacement, single cylinder engines with spark ignition are used as a low cost propulsion in many applications like scooters, motor cycles, small boats and handheld power tools. These engines follow two- or four-stroke principle and are usually realized with a carburetor. They represent an affordable and simple as well as durable propulsion technology, but concurrently their efficiency is low and emissions are high. Consequently, the share of these small engine applications of total emissions and fuel consumption is not negligible. Therefore, the demand to increase efficiency of these engines is rising and the development of suitable and cost efficient methods is required.

Poor or absent infrastructure for supplying energy for electric vehicles (EVs) and a short driving range prevent the widespread use of EVs in Japan. In this study, an inexpensive series hybrid system, consisting of an EV and a trailer-type engine generator (TEG), was developed to extend the driving range. A trailer and a gasoline operating engine generator, which can be supplied at common gas stations, were designed and manufactured. Several driving experiments to evaluate the performance of this new system were carried out. Considering the total weight of 1,900 kg and the small engine, the average fuel economy over 11 km/liter obtained in the experiment was notable. This series hybrid system achieved a better performance than the plug-in hybrid system which has been developed recently. The Japanese government agreed to register this TEG as a special-purpose vehicle for emergency power supply in July 2007.

Series hybrid Unmanned aerial vehicle(UAV) that is proposed in this paper performs Vertical take-off and landing(VTOL) using the battery and generator, and it applies the series hybrid system with combination of the small engine and generator when cruising flight. This system can be described as the next-generation system that can dramatically increase the UAV flight times. Also, UAV systems require a large energy at the time of VTOL to be conducted for a short time. Therefore, this paper designs Permanent Magnet Synchronous Generator (PMSG) having a high specific power considering VTOL through the FEA.

There is still significant improvement that can be made in terms of improving the fuel efficiency of modern internal combustion engines. Often times this decrease in fuel efficieny is a result of an incomplete combustion reaction. Incomplete combustion reactions may result from two main aspects during the combustion process: (1) incomplete vaporization of fuel before ignition, and (2) insuffient oxygen in the combustion environment. The work here aims to develop a novel system that maximizes fuel efficiency, while minimizing the effects of incomplete combustion. This was accomplished by incorporating ultrasonic vaporization techniques, inconjunction with an oxygen concentrator, into a small engine. The engine performance was compared between the conventional and enhanced systems.

A project dealing with small gas turbine engine inlet total pressure distortion testing was solved at the University of Defence. Within this project a new device for creation and measurement of the total pressure inlet distortion was designed. In the early stage of the project there was a need of significant amount of testing for evaluation of newly designed device, foundation of measurement methodology, testing of basic distortion screen designs and their affects. In order to save expanses for the jet engine operation for these initial tests it was replaced by a model device drawing air through the engine inlet. This paper describes design of the measurement device, its initial tests and lessons learned from this development. Difficulties encountered with substitution of the jet engine by standalone compressor are also presented.

The US Environmental Protection Agency (EPA) initiated the Small Engine Exposure Study (SEES) to evaluate potential exposures among users of small, gasoline-powered, non-road spark-ignition (SI) lawn and garden engines. Equipment tested included riding tractors, walk-behind lawn mowers, string trimmers, and chainsaws. Personal and background air quality measurements were collected on equipment operators for carbon monoxide (CO), particulate matteror=2.5 microm in aerodynamic diameter (PM(2.5)), volatile organic compounds (VOCs), and aldehydes. PM(2.5) measurements included continuous and integrated mass, elemental and organic carbon (EC/OC), and trace metals. Aldehyde measurements included speciation for formaldehyde and acetaldehyde. The results demonstrated that equipment operators can experience elevated exposures to CO, PM(2.5) and air toxics while operating these engines. Ten-second average CO personal exposures spanned over two orders of magnitude, with short-term concentrations exceeding 120 p.p.m. for some engine applications tested. PM(2.5) concentrations averaged over each engine test period also spanned two orders of magnitude. The results also suggest that health standards, such as the CO and PM(2.5) National Ambient Air Quality Standards (NAAQS), may be exceeded for certain equipment types under certain operating scenarios. Aldehyde measurements suggested exposures from primary engine emissions that exceed typical ambient concentrations, but do not exceed occupational health standards. Continuous exposure measurements illustrated the important role of the operator's activity and environmental conditions in affecting exposure levels.

After the great success of the application of the common rail system on the vehicles, it became very attractive to apply this new injection system on small engine, which has much industrial application. This work represents a comprehensive study on optimising the magnetic properties of the electro-injector used in off-road application. In this work analytical studies were implemented to simulate the solenoid actuator for the electro-injector, depend on the required quantities of the diesel oil. To reach our goal different models with different concepts were built-up to evaluate the best magnetic properties of the applied materials. Different types of steels were simulated, to achieve the better working force from the solenoid actuator. Different models were built-up by varying the material properties from one side and the working parameters such as the coil turn, current for a fixed gap between the armature and the back iron from the other side. Comprehensive structural modelling was carried out to secure and optimise the function ability of the electro-injector, in particular the interference fitting between different parts of this injector. The analytical study was carried out with the application of FEM using ANSYS 6.1 and Pro/Mech. programmes. As a result of this simulation, the magnetic characterization has been determined, by choosing the right steel for the best solenoid actuator application. The electro-injector parts were optimised. Finally, the experimental and analytical results both were in good agreement.

Mainly owing to the dwindling fossil oil resources and the environmental concerns of discharging greenhouse gases into the atmosphere, it is essential to find an alternative to kerosene for civil aviation. This paper covers the main effects on aero engines when changing to hydrogen fuel. Particularly, emission and performance issues are discussed, but some design matters are also covered. By simply changing to hydrogen, small engine performance gains may be obtained. The results of the calculations suggest that there is the potential to design a combustion system using hydrogen that produces less NOx emissions than any system using kerosene.

Conceptual design studies have been conducted for a propulsion system on an advanced transport aircraft, with the objective to define an engine/aircraft configuration that would be able to meet the NASA N+3 goal for fuel burn reduction at entry into service in 2035. The vehicle configuration is the MIT D8.6 airplane, which has two boundary layer ingesting engines located at the upper aft fuselage. The engine design space is high overall pressure ratio and high bypass ratio at relatively small thrust size and very small core engine physical size. Conventional turbofan engine architecture encounters significant challenges in high-OPR small engine design space associated with accommodation of a concentric fan drive shaft through the very small core and adverse effect of small core size on component efficiency. Conceptual design of an alternative engine architecture is defined based on a two-spool gas generator core that is mechanically uncoupled from the propulsor such that the fan drive shaft does not pass through the core.

Today the environmental issues are a lot on the agenda and the environmental awareness are more and more common. New laws and restrictions on engines emissions are enforced and the demand on the engines gets higher and tougher. This leads to the engine testing playing a more crucial part than ever. Engine tests are done using an engine dynamometer. The dynamometer loads the engine by, in many different ways, absorbing the power and torque generated by engine. The most important functions of a dyno are to convey the power from the engine to the dyno, to load the engine, to measure the power and torque generated by the engine and to remove the excess heat that is generated. Husqvarna is a Swedish company that produces garden and forest cutting tools, their most famous products are their chainsaws. Husqvarna does an extensive amount of engine testing, long time testing, functional testing and field testing. Some functional tests, such as start-ability after use is done in a climate chamber where the humidity and temperature can be set. Today, loading a chainsaw in -25 °C is a problem due to the fact that the most used dynamometer at Husqvarna is a water brake that freezes in minus degrees. This master thesis will answer the question on how to, for small engine, simulate the load that occurs during normal use of the engine and how to develop a dynamometer suitable for Husqvarna’s needs? The focus when developing the dynamometer will lie on solving the problem with minus degrees and having a good detachable coupling between the dyno and the chainsaw. The result is a hydraulic oil dynamometer. A hydraulic pump is attached to the guide bar and chainsaw using a detachable key way coupling and bearings. By controlling restriction of the flow in the hydraulic system the load can be controlled and also ultimately the RPM of the chainsaw. The hydraulic oil works fine in the minus degree as long as the right oil with the right viscosity range is used although a problem with the small chainsaws are that they are not reaching the full RPM in -25 °C. Mainly because of the backpressure created by the components in the system. This can be solved by minimizing the hydraulic systems total flow restriction. However this problem doesn’t affect the testing methods as long as the chainsaw easily can be disconnected and freed from the dynamometer and then be run to full RPM which the coupling between the pump and chainsaw enables.

The valve of a certain type of small engine often has the fault phenomenon of abnormal vibration noise and can't close under the specified pressure, which may cause the engine automatic stop because of valve incomplete close leading to fuel leakage during test and startup on the bench. By test study compared to imported valve with the same use function and test condition valve, and put forward the thinking of improving valve structure, compared no-improved valve to improved valve by adopting Fluent field simulation software. As a result, improved valve can restore close pressure of valve, restrain abnormal vibration noise phenomenon, and effectively compensate compression value of spring because of steel ball contacting position downward with valve casing.

This paper explores an infrequently encountered hazard associated with liquid fuel tanks on gasoline-powered equipment using non-vented fuel caps. Depending on the location of fuel reserve tanks, waste heat from the engine or other vehicle systems can warm the fuel during operation. In the event that the fuel cap is not vented and if the fuel is sufficiently heated, the liquid fuel may become superheated and pose a splash hazard if the fuel cap is suddenly removed. Accident reports often describe the ejection of liquid from the fuel tank opening as a geyser. This geyser is a transient, two-phase flow, vertical jet of flashing liquid. This could create a fire hazard as the geyser could result in splashing flammable liquid onto any bystanders. Many fuel tank systems are vented to ambient through the fuel tank cap and, in addition, may incorporate other features that contribute to pressure relief. Venting of the pressurized vapor inhibits the vapor-liquid mixture in the fuel tank from achieving thermodynamic equilibrium, thus preventing the formation of a superheated liquid. It has been empirically determined that flashing two-phase flow can be prevented by keeping the fuel tank pressure below 1.5 psig. However, if the cap is not vented or vents at a lesser rate than the rate of liquid vaporization, pressure in the tank can rise and the flammable liquid can become superheated. This phenomenon is explored here to facilitate a better understanding of how the hazard is created. The nature of the hazard is explained using thermodynamic concepts. The differences in behavior between a closed system and an open system are discussed and then illustrated through experimental results obtained from two sources: experiments with externally heated fuel containers and operation of a gasoline-powered riding lawn mower. The role of the vented fuel cap in preventing the geyser phenomenon is demonstrated.

This paper investigates abnormal combustion during the cranking phase of spark-ignition small engines, specifically the occurrence of backfire at the release of the starter motor during kickback. The research focusses on the influence of fuel composition, mainly in terms of ethanol percentage, on backfire occurrence. Interest in this abnormal combustion is growing due to the increased use of fuels with different chemicalphysical properties with respect to gasoline. Moreover, this issue will become even more topical due to the implementation of simple control and fuel supply systems on low cost-engines, which are widely used in developing countries. Experimentation was carried out in an optically accessible engine derived from a 4-stroke spark ignition engine for two-wheel vehicles. The test bench was instrumented and adapted in order to simulate the engine conditions that lead to anomalous ignition in the intake duct (backfire) during the reverse rotation of the engine (kickback). Two different test procedures were developed with the aim of promoting the ignition at the intake. Major engine parameters were measured, such as the incylinder pressure, the pressure at the exhaust and at the intake; in order to characterize the engine conditions and to monitor the ignition in the intake manifold. Furthermore, an optical investigation of the combustion chamber was performed using high spatial and temporal resolution measurements. Engine and optical data were correlated and the analysis allowed characterization of backfire during kick-back, enabling identification of the conditions that make backfire more probable and to observe the influence of fuel composition

Common core engine technology has been pursued by industry for decades due to the potential of reducing costs for design, development, and operation when applying the same core over a family of engines for multiple applications. This paper investigates the design space for a next-generation technology level common core (high pressure system) for multiple applications at each engine’s flight conditions and power requirements. To evaluate the feasibility of a common core between different applications, or market segments, three engine applications for a similar small engine power class were considered: a turboshaft helicopter, a regional turboprop commercial transport, and a regional turbofan commercial transport. To perform this design space exploration, the Numerical Propulsion System Simulation and Weight Analysis of Turbine Engines (WATE++) were used within a Multi-Design Point (MDP) framework. The MDP approach ensures that all design and offdesign requirements and constraints for a given engine are simultaneously met. Within MDP, this paper demonstrates how candidate cores can be evaluated concurrently for all three engine applications. This ensures the same core is implemented on each application and allows flexibility for exploring the common core design space, while providing an added degree of freedom in evaluating performance trade-offs. In order to determine how well the common core is suited across applications, the “ideal” cycle design is first selected for each engine independently. This paper discusses the trade-offs and decisions that must be made in order to select a “100% fully common” core while aiming to incur minimum performance penalties compared to independently designed engines. The results show significant penalties for a common core operated across multiple applications, which motivates future work to explore trade-offs for different levels of commonality, development cost, and robust design when selecting a common core for multiple engine applications.

A series HEV with a minimal or “light” ESS and a small engine is examined with the objective of maximizing fuel economy with little all-electric range. The motivation is the re-examination of assumptions about consumer adoption of electric vehicles, with the goal to consider lowest cost of ownership without compromising range. Lowest cost of ownership is indicated by maximizing fuel economy with a small energy storage system and a minimal displacement engine sized for average, rather than peak power. A minimal ESS is found via a parametric study for maximum fuel economy and empirically validated on a chassis dynamometer.

The simulation of a jet engine behavior is widely used in many different aspects of the engine development and maintenance. Achieving high quality jet engine control systems requires the iterative use of these simulations to virtually test the performance of the engine avoiding any possible damage on the real engine. Jet engine simulations involve the use of mathematical models which are complex and may not always be available. This paper introduces an approach based on Genetic Programming (GP) to model different parameters of a small engine for control design such as the Exhaust Gas Temperature (EGT). The GP approach has no knowledge of the characteristics of the engine. Instead, the model is found by the evolution of models based on past measurements of parameters such as the pump voltage. Once the model is obtained, it is used to predict the behaviour of the jet engine one step ahead. The proposed approach is successfully applied for the simulation of a Behotec j66 jet engine and the results are presented.

Benchmarks are defined, against which the performance of a given engine may be judged, with general indications for engine selection and aspects of design through which improvements may be sought. These are derived from published compilations of engine performance data obtained from suppliers around the world, which, if regularly refined and updated, will allow progress in small engine design to be systematically monitored and encouraged.

In this study, a model to simulate the dynamic operation of regenerative gas turbines is described and the transient behaviour of a small engine equipped with a stationary recuperator is presented. The mathematical model of each component consisted of unsteady one-dimensional governing equations and steady state component characteristics. The equation set derived was solved by using a fully implicit numerical method. A realistic control unit model for speed control was likewise introduced to simulate the operation of real engines. Special emphasis was given to the thermal inertia of the recuperator metal that governs the dynamic characteristics of the engine. The dynamic characteristics were examined for a couple of load change modes such as stepwise and periodic load variations. Characteristic transient responses were then investigated and the dependence of transient response on the frequency of load variation was demonstrated.

The new DK series engines are developed as the next generation of engines, with 5 common concepts: environmental protection, high output with smaller engine size, high efficiency, reduction in maintenance and running cost, and increase in reliability and durability.Other than the in-line 6 and 8 cylinder types, the DK-20 model comes with 3 and 5 cylinders, and the DK 26 model with a 5 cylinder type. Development of various cylinder number types within the same model allows the new DK series to cover a wide range of output with a small engine model lineup.With the development of 3DK-20, the low output range that had been covered by high revolution engine running on marine diesel oil can now be covered by engine running on heavy diesel oil. Also, when looking at parts around the piston area, a 3 cylinder engine effectively halves the parts number compared to 6 cylinder engines with the same output. This achieves great reduction inrunning cost and maintenance costs.The follwing will introduce the new DK series engines, with details on design, performance, and benefits.

The objective of this paper is the evaluation of the effect of the fuel properties and the comparison of a PFI and GDI injection system on the performances and on particle emission in a Spark Ignition engine. Experimental investigation was carried out in a small single cylinder engine for two wheel vehicles. The engine displacement was 250 cc. It was equipped with a prototype GDI head and also with an injector in the intake manifold. This makes it possible to run the engine both in GDI and PFI configurations. The engine was fuelled with neat gasoline and ethanol, and ethanol/gasoline blends at 10% v/v, 50% v/v and 85% v/v. The engine was equipped of a quartz pressure transducer that was flush-mounted in the region between intake and exhaust valves. Tests were carried out at 3000 rpm and 4000 rpm full load and two different lambda conditions. These engine points were chosen as representative of urban driving conditions. The gaseous emissions and particle concentration were measured at the exhaust by means of conventional instruments. Particle size distribution function was measured in the range from 5.6 nm to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS). The effect of ethanol blending on particle emission depends on engine configuration and ethanol percentage. A strong increase of particle emission for E50 was observed in PFI configuration. For GDI configuration a larger particle emissions with respect to gasoline fuel was measured for E10. Moreover, for blends fuelling, particle emissions decrease with the ethanol percentage.