Browse Topic: Carburetors
As climate change drives the exploration into new and alternative fuels, biodiesel has emerged as a promising alternative to traditional diesel fuel. To further increase the viability of biodiesel, a unique system at the University of Kansas utilizes glycerin, the primary byproduct of biodiesel production, for power generation. This system converts glycerin into a hydrogen-rich gas (syngas) that is sent to an engine-generator system in one continuous flow process. The current setup allows for running the engine-generator system on pure propane, reformed propane, or reformed glycerin, with each fuel serving a unique purpose. This paper discusses upgrades in pure propane operation that serves the intent of preheating the engine prior to syngas operation and establishing the baseline energy requirement for fueling the system. The current upgrade to the fuel system incorporates an Electric Fuel Valve (EFV) as a replacement for a gaseous propane carburetor, providing the ability for Air-to-Fuel Ratio (AFR) adjustment of the engine at different generator loads. The use of EFV in a continuous fuel additive manner provides a solution to the carburetor’s inherent disadvantage: maintaining a constant AFR. Hence, this upgrade allows the system to adjust more accurately to different engine operating conditions and other unique fuels to be potentially tested (e.g., natural gas and biogas). Moreover, spark timing optimization accompanies the new fuel control in order to enhance engine performance and maximize fuel economy. Finally, in-cylinder pressure traces and associated performance parameters are reviewed and discussed in order to analyze the operation of the new EFV-based system.
Every year, large numbers of two wheelers are sold in India and other Asian countries. A majority of these engines still tend to be carbureted due to cost and fuel quality issues. As an alternative to the carburetor, port fuel injectors (PFI) have started being introduced in the last few years for small two wheeler vehicles. Although PFI systems offer better metering of fuel and better transient response compared to carbureted systems, they are more expensive and require more power to pressurize the fuel. More importantly, wall film formation is observed in both the technologies, which reduces the effectiveness of the PFI system. Hence, a new technology is proposed which includes a PFI system along with an ultrasonic atomizer. The purpose of the proposed system is to improve the transient response and hence improve the fuel economy of gasoline engines and lower the emissions especially under cold conditions. The proposed concept was tested standalone on a laboratory setup. A transparent duct of square section was fabricated and fuel was injected in it. High speed schlieren imaging was done to qualitatively visualize the vapor concentration in the proposed system compared to a conventional port fuel injection system. Mass measurement of the fuel atomized was done to quantitatively characterize the proposed system. The proposed system was found to be better than the existing conventional PFI system. It has metering capability like PFI with potentially better transient response at a similar cost.
High specific fuel consumption and pollutant emissions are the main drawbacks of the small crankcase-scavenged two-stroke engine. The symmetrical port timing combined with a carburetor or an indirect injection system leads to a lower scavenging efficiency than a four-stroke engine and to the short-circuit of fresh air-fuel mixture. The use of fuel supply systems as the indirect injection and the carburetor is the standard solution for small two-stroke engine equipment, due to the necessity of reducing the complexity, weight, overall dimensions and costs. This paper presents the results of a detailed study on the application of an innovative Low Pressure Direct Injection system (LPDI) on an existing 300 cm3 cylinder formerly equipped with a carburetor. The proposed solution is characterized by two injectors working at 5 bar of injection pressure. The injection nozzles are located in the liner wall at the opposite side of the exhaust port, with the axes oriented towards the piston at the BDC (Bottom Dead Center). The injectors are positioned above all of the cylinder ports in order to have an injection timing independent from the ports timing. The only constraint to the injection timing is related to the piston motion, with great benefits in terms of short-circuit reduction in all of the engine operating conditions. Numerical and experimental activity was carried out in order to identify the best injector configuration and to assess the system performance. The results of the experimental study are reported here. Standard low cost components from the automotive market were used, without a significant increase of weight. The benefits of the innovative two-stroke LPDI engine were evaluated at the test bench and compared with the performance of the configurations equipped with the carburetor and the indirect injection system. Once the position of the injectors inside the cylinder was defined, the development of the system at the test bench was focused primarily on the definition of the best injection timing, also taking advantage of the numerical results of the CFD analysis. The experimental setup and the fine-tuning methodology are discussed in detail. The goal was to reach the best thermodynamic efficiency and the lowest pollutant emissions of the LPDI system while ensuring the same engine power with respect to the other two configurations, without increasing the manufacturing costs.
High specific fuel consumption and pollutant emissions are the main drawbacks of the small crankcase-scavenged two-stroke engine. The symmetrical port timing combined with a carburetor or an indirect injection system leads to a lower scavenging efficiency than a four-stroke engine and to the short-circuit of fresh air-fuel mixture. The use of fuel supply systems as the indirect injection and the carburetor is the standard solution for small two-stroke engine equipment, due to the necessity of reducing the complexity, weight, overall dimensions and costs. This paper presents the results of a detailed study on the application of an innovative Low Pressure Direct Injection system (LPDI) on an existing 300 cm3 cylinder formerly equipped with a carburetor. The proposed solution is characterized by two injectors working at 5 bar of injection pressure. The injection nozzles are located in the liner wall at the opposite side of the exhaust port, with the axes oriented towards the piston at the BDC (Bottom Dead Center). The injectors are positioned above all of the cylinder ports in order to have an injection timing independent from the ports timing. The only constraint to the injection timing is related to the piston motion, with great benefits in terms of short-circuit reduction in all of the engine operating conditions. Numerical and experimental activity was carried out in order to identify the best injector configuration and to assess the system performance. The results of the preliminary 3-D CFD study are here reported. The best positioning of the injectors was determined at the operating condition of maximum power by means of a sensitivity analysis of the circumferential position and spray orientation. The performance comparison was evaluated in terms of fuel short-circuit and spray vaporization. The optimized configuration was also verified at lower revolution speeds and partial loads showing a great potential for all of the working conditions. The experiments on a real prototype on the test bench confirmed the predictions showing significant improvements in comparison with the original configuration.
Emerging markets like India is very cost sensitive for small engines like motorcycle. Capacitive discharge Ignition (CDI) with carburetor is popular low cost solution with good engine performance. CDI system accumulates charge inside the ignition capacitor, until a point at which a signal allows to release discharge of the stored charge to the spark plug through high tension coil. This paper will focus on single spark digital two teeth DC CDI solution and below design challenges with two sparks. 1 Higher power dissipation in step up fly back converter 2 Need higher CPU speed, flash size and restrictions on engine map profile for advance angles This paper will elaborate above problems and their solutions with test results for optimizing solution cost and achieve performance. Solutions include, exploring 8 bit microcontroller peripherals usage and smart software to boost MCU performance for engine dynamic conditions and to achieve lower losses in flyback converter.
In India, for two-wheeler application, carburettor is the preferred fuel supply system for majority of the market, owing to its simplicity and low cost. With the regulations becoming stringent, carburettor internal structure requires modification. One of the important parameters is the venturi shape, which controls the air-fuel mixture supply to the engine. Venturi shape plays an important role in deciding the transient performance characteristics. In this study, a CFD analysis has been carried out to predict the pressure and velocity at the venture of the carburettor. Four different cross sections namely, circular, oval, trapezoidal and double D venturi shapes were selected. The geometric model of the carburettor was created and mesh refinements were carried out in critical regions. At part open throttle, CFD prediction of airflow rate with Trapezoidal venturi shape was found higher when compared to other venturi shapes. In actual vehicle trials, it was found that this venturi shape has a better acceleration time of 5% (0∼60 km) compared to circular shape. At wide open throttle, CFD predicted airflow rate with circular venturi shape was found better than other venturi shapes due to lesser restriction. In actual vehicle trials, this type of venturi cross section yielded 4% more power than the trapezoidal venturi carburetors. Finally it is concluded that oval shape is a good compromise for an optimum performance.
In racing world regardless of two-wheeled vehicle (motorcycle) or four-wheeled vehicle, vehicle setting is performed in accordance with various race conditions. From the age of carburetor till even now ECU is used, vehicle setting executes as well and plays an important role. Changeover to electronic control makes vehicle control more precise; meanwhile, vehicle control technique to become complicated is occurring every day. Therefore, whenever a new competition vehicle is developed, tool required for vehicle setting is also necessary to be updated according to vehicle control technique implemented. Setting-method till now is that, all information required for vehicle setting is packaged in tool, thereby tool and vehicle have always been a combination of 1-to-1. Consequently, in manufacturer's vehicle development, tool development / update becomes a burden and leads to increment of development costs. Furthermore, when purchasing a new vehicle in order to participate racing, user needs to update tool simultaneously, tool-buying expense and approaching effort also become a burden. This research has explored setting-method without need of frequent tool update, aiming to solve the problems caused by current setting-method and obtain flexibility with increasing complexity of vehicle control. Configuration that classifies vehicle setting information into common term information and vehicle control dependence information is adopted, i.e., common term information is kept on tool side as template, and vehicle control dependence information is kept on ECU side as profile. At the first time connecting tool with vehicle, vehicle model information and all setting data for editing are read from prescribed profile of ECU; setting data edit screens are built from prescribed template of tool, and operated as database afterwards. From next time, tool is selectable from database by vehicle model information. Data-setting configuration using prescribed template and profile has been put into practical use for competition motorcycles; as a result, that a single tool can deal with multiple ECU equipped not only in same vehicle, but also in different category vehicle, has been realized. Technical contents and substantiation results have been firstly summarized in this paper.
Meeting future legislative targets for SI engines by means of low cost technologies is a big challenge for engineers. Despite the use of simple and cost efficient components these engines have to fulfill customer requirements in terms of power and fuel economy, representing the most important selling arguments. Without the possibility of integrating modern technologies like fuel injection systems for mixture preparation instead of simple carburetors, it is very complex to find viable solutions that enable the achievement of these targets. A main key to improve emission behavior, fuel economy and performance on carbureted engines is to get an insight in the mixture preparation process, especially under transient conditions. Therefore, the Institute for Internal Combustion Engines and Thermodynamics of Graz University of Technology together with AVL Germany investigated possibilities to measure the fuel mass flow with a flexible, quick responding device that does not influence the carburetor itself. Comparisons of different fuel flow measurement tools on several engine applications were done to find out which one delivers the information required for advanced carburetor setup tasks in the best possible way. This should serve as a basis for future mixture preparation development on the test bench and especially for in-field optimization.
Based on the fuel consumption analysis methods published on last year's SETC [1], we compared fuel economies of a typical 125cc production motorcycle equipped with either electronic (port) fuel injection (EFI/PFI) engine management system (EMS) or constant vacuum carburetor (Carb). In addition to earlier discussed PFI results, stationary engine map measurements of fuel consumption on an engine dynamometer (dyno) were conducted for the Carb engine. The powerful development tool of fuel consumption test cycle simulation uses these stationary engine dyno results to calculate fuel consumption of real transient vehicle operation. Here it was employed to assess economy of both fuel system configurations under different driving conditions. Besides the Indian Driving Cycle (IDC) and the World Motorcycle Test Cycle (WMTC), we investigated real world drive patterns typical for emerging markets in terms of a Bangalore urban cycle and a Malaysian suburban cycle. The results reveal a considerable influence up to 50% of the drive pattern on fuel consumption of both PFI and Carb. We found real urban driving fuel economy to range between soft IDC and demanding WMTC. Comparing fuel systems across the real world drive patterns, the Carb showed 12 to 17% higher fuel consumption than the PFI at colder engine temperature. However, the fuel economy disadvantage diminished for hot engine. To validate the test cycle simulation results, we conducted transient vehicle measurements of fuel consumption on the chassis dyno, for both vehicle configurations and selected urban drive patterns. These measurements confirmed that a) real world driving takes place at rather cold engine temperatures, and b) fuel economy benefit of PFI relevant for the majority of 2-wheeler end customers is really between 7 and 18%. Thus, the Carb in real world driving is not able to benefit from its theoretical lean combustion thermal efficiency potential.
The 912 engine is a well known 4-cylinder horizontally opposed 4-stroke liquid-/air-cooled aircraft engine. The 912 family has a strong track record: 40 000 engines sold / 25 000 still in operation / 5 million flight hours annually. 88% of all light aircraft OEMs use Rotax engines. The 912iS is an evolution of the Rotax 912ULS carbureted engine. The “i” stands for electronic fuel injection which has been developed according to flight standards, providing a better fuel efficiency over the current 912ULS of more than 20% and in a range of 38% to 70% compared to other competitive engines in the light sport, ultra-light aircraft and the general aviation industry. BRP engineers have incorporated several technology enhancements. The fully redundant digital Engine Control Unit (ECU) offers a computer based electronic diagnostic system which makes it easier to diagnose and service the engine. The modern fuel system consists of two fuel rails and two injectors per cylinder, pressure regulator and a return line. Redundant Sensors monitor air box vacuum, exhaust gas temperature, ambient air pressure, inlet air temperature, coolant temperature and throttle position. The injection system ensures optimal fuel and air mixture at any altitude for longer flight range and lower operating costs. This makes the engine more environmentally friendly due to lower CO2 emission levels. Other advantages for the pilots are no manual choke, no carburetor icing, and no requirement for synchronising carburetors. The three-year development period included more than 10,000 hours on the test bench and 700 test hours in the air to ensure 2,000 hours time between overhauls (TBO); the same TBO as the 912 engine. At 63,6kg (140, 2 lbs), the Rotax 912 iS engine delivers the best power-to-weight ratio in its category.
This SAE Recommended Practice covers all carburetors and throttle bodies used on permanently installed gasoline marine engines.
Small combustion Engines equipped with a conventional carburetor system have the disadvantage of incomplete combustion in different load ranges because of a sub optimal air fuel ratio. The results are harmful exhausts, high fuel consumption and a low degree of efficiency. Based on this problem VEMAC has invented the patented Piezoelectric Controlled Carburetor (PCC). A small piezo bending actuator in front of the fuel jet allows controlling the fuel flow through the jet according to the desired air-fuel-ratio (AFR) and the engine performance. To control the piezo bending actuator and process the data of the incoming sensor signals an engine control unit (ECU), with modular software architecture for different applications was developed. This paper describes the working principle of the PCC technology and presents the most up-to-date development and test results. The clear benefits of the PCC system with less fuel consumption and exhaust emissions compared to conventional carburetors to meet next level emission regulations are shown. The paper demonstrates that these benefits are achievable with a simple and cheap alternative to injection systems and discusses the advantages also in comparison to other electronic controlled carburetion systems, which were published in the last few years.
Currently, a majority of the ‘gasoline’ sold at the pumps in the United States is a nominal blend of 90% gasoline and 10% ethanol. This mixture is commonly referred to as E10. This paper reports on a study conducted to determine the effects of E10 on the fuel system performance of vintage automobiles. The study focused on the potential degradation in performance of the carburetors and fuel pumps due to exposure to E10. Six fuel systems were selected for study including the 1948 Flathead Ford, 1958 Volkswagen Beetle, 1962 Ford Falcon, 1969 Chevrolet Bel Air and 1970 Chrysler New Yorker. The components tested were either rebuilt original equipment or new aftermarket replacement parts, depending on availability. Although the components tested were not all original equipment parts, they represent a reasonable sample of the types of parts likely to be found in vintage vehicles currently on the road. The fuel system components were tested under both dynamic and static conditions. The dynamic tests were designed to study the operational performance of the components. For dynamic testing, two sets of components were acquired for each model fuel system. The components were assembled in test rigs that mimicked their operation in a vehicle. One set was tested using straight pump-grade gasoline (E0) and the other set was tested using pump-grade E10. The systems were operated for 1600 to 2400 hours at a 25 percent duty cycle. In addition to the run hours, the fuel systems were allowed to sit idle and exposed to fuel for an additional 2600 hours between run cycles, for a total exposure time of 4200 hours. Periodically the fuel pump flow rates and pressure heads were measured. All systems were found to be performing normally throughout the test period. After completion of the testing each component was disassembled and examined for signs of material damage. The most common observation was staining and tarnishing. Nothing was found that would suggest the imminent failure of a part. The static exposure tests were designed to identify material damage caused by alternately wetting and drying the components. These tests were conducted on a third set of components which were cut into sections and periodically sprayed with either E0 or E10. The periodic exposure, a 5 minute soaked followed by a 55 minute dry time exposure in air, was intended to accelerate potential swelling/shrinking problems with seals/gaskets and corrosion problems on metals. After 3000 hours of exposure minor changes were noted, but nothing that would suggest imminent failure of a part.
Today in developing countries, carburetors are mainly used in small engines for motorcycle application. Carburetor takes more time for the mixture preparation process, hence the response of the vehicle is sluggish for the rider. To overcome this problem is fuel injection system. The purpose of this work is to study the transient response of a gasoline fuel injection motorcycle engine with different injection parameters. The analysis of the flow is conducted using the commercial CFD software. The simulated results are also compared with the stand start acceleration test results done on the motorcycle, which shows 11% improvement than carbureted vehicle.
Carbureted small displacement motorcycles are the most common form of road transport in Asia. Small displacement motorcycles have historically been low-cost and low-tech. In order to achieve the best overall performance, economy and emissions, a more sophisticated fuel injection system is required. To address the fuel consumption and emissions of existing “legacy” vehicles, we have developed an Electronic Fuel Injection (EFI) retrofit for common small motorcycles in Asia. The system leverages existing components as much as possible allowing focus on integration into the host vehicle and overall system tuning. This paper details the overall system design, modeling, component selection and system tuning of a 120 cc single cylinder four stroke EFI retrofit kit. The target vehicle is tested on dynamometer with stock carburetor settings, and with the EFI kit. The EFI system reduces fuel consumption by approximately 10%, HC emissions by 55%, CO emissions by 96% while doubling the NOx emissions and matching the carbureted system's power.
A construction of the technology concerning fuel consumption improvement is an important problem not only for the four-wheeled vehicle but also for the motorcycle in recent years when petroleum resources are depleted rapidly. Yamaha originally developed a new fuel injection system (YMJET-FI) and applied the system to a single cylinder, water-cooled and small-displacement engine. In this paper, we would introduce the results of improving the fuel economy with keeping high performance. Improvements were noted in three matters, namely, in the lower load range, 1.Strengthening of in-cylinder flow, 2.Atomization of fuel spray, and 3.Reduction of wall film quantity. As a result of the combustion improvement by this system and the optimization of the engine performance, the developed model (the prototype model) with this system was able to improve the fuel consumption by 22% on the test cycle of ECE R40-01 compared with the production model with a carburetor as reference, while maintaining high performance.
Looking at the market for 2-wheelers driven by small capacity four stroke engines, it turns out that the legislation for exhaust emissions is mostly combined with a regulation of vehicle speed. Most of the vehicles in this category are still driven by engines equipped with carburetors which, unlike fuel injection systems, do not give the possibility to cut off fuel metering when high speed is achieved. When a carburetor is applied with a simple ignition unit, a reduction of spark advance is the only way to ensure correct vehicle speed, but there are a lot of disadvantages in terms of exhaust emissions and fuel economy coming up with this method of engine power restriction. This leads to the idea of using exhaust gas recirculation (EGR) to reduce engine power when necessary.
In the handheld industry the carburetor controlled 2-stroke engine is still the mostly used power source. The current carburetor as a fixed geometric and hydraulic system is not capable of compensating varying fuel specifications. Electronic engine management systems offer the adjustment of varying ambient conditions and fuel qualities. State of the art systems of common vehicle applications use various sensors and actuators which increase the complexity and the costs of the engine. A smart alternative is an engine control based upon processing of already existing information in a small handheld engine. This paper presents the concept, the configuration and the design parameters of such a system.
Future exhaust emission targets and increasing customer demands call for the implementation of enhanced engine technologies, as well known from automotive applications, into small capacity engine categories. Especially the applied engineering solutions in the market of motor vehicles driven by engines up to 50 cm3 displacement have been significantly changed in the last years. Beside low cost technologies (air cooled two stroke or four stroke engines with carburetor), enhanced mixture preparation and exhaust gas after treatment systems come to use. Highly technological two stroke engines are equipped with direct fuel injection systems in combination with efficient exhaust gas after treatment methods; in four stroke engine applications intake port fuel injection systems in combination with oxidation catalysts or 3-way catalytic conversion are established on the market. Several applications of new and innovative technologies have already been worked out in research programs and presented at several SETC conferences (please refer to the following papers: SETC 2006-32-0065 [1], SETC 2005-32-0098 [2] and [3] for the two stroke engines and SETC 2006-01-0404 [4], 2004-01-2105 [5] for four stroke engines). These technologies are now available in a pre-serial production status or as prototype engines.
Small two-wheel vehicles have secured a solid position as a major means of transport in many countries in the world. Meanwhile, more stringent emissions standards, typically EURO-3, are expected to be introduced in various countries by 2006. This calls for the shift of fuel supply systems for small two-wheel vehicles from carburetors, the present mainstay, to more precision, highly controllable electronic fuel injection systems. However, conventional fuel injection systems require various functional components including a fuel pump, regulator and injectors. Particularly, the need for location of the fuel pump within the fuel tank will present layout problems to small two-wheel vehicles that have a relatively limited tank capacity. Moreover, the fuel pump must continue to run at all times to hold fuel at a high pressure for supply to the injectors. Consequently, much consumption current is required. To overcome all these problems, a discharge pump type fuel injection system has been developed that can efficiently handle atmospheric pressure fuel as do carburetors, as well as provide precision control over fuel injection comparable to conventional fuel injection systems.
With the increasing requirements of environmental conservation in recent years, reduced exhaust emissions and increased fuel-efficiency are in high demand for smaller size motorcycles popular in the Asian region. In order to meet such demand, the optimum design of the fuel supply system is the most effective method. In the carburetor, the core component of the fuel supply system used on a majority of current models, a 25% improvement in the accuracy of air-fuel ratio fluctuation, as well as a 15% reduction in size, have been achieved in comparison with past models. On the other hand, in fuel injection systems, the use of which is gradually expanding, it is essential that the components be highly functional with high performance, while at the same time being of a compact size. In regards to the injector, optimum spray form and a 30% reduction in size have been realized by utilizing injection simulation techniques. As for the fuel pump, a unit capable of operating with an electrical current of less than 1 amp has been developed by optimizing the design of the pump rotor. For the throttle body, the number of sensor components has been reduced by 21 while at the same time stable control at minute airflow volumes has also been achieved. In regards to the ECU, with the use of integrated-function custom IC components and high-density surface mounting, both a reduction in size and also an increase in possible function range have been realized. As a result of these activities, system components to constitute a fuel injection system easily installed in and suitable for the wide range of engine frames and engine characteristics of small size engines have been developed.
TCT - Total Combustion Technology is technology designed to enable small SI four-stroke and two-stroke engines to meet current and proposed emission standards that pertain to small engines. This paper outlines the technology, the testing equipment, and the results from tests comparing TCT to original carburetors on two different engines. The comparison shows clearly that emissions can be reduced substantially by TCT. The MLC (Mechanical Lambda Control) feature of TCT allows the emission profile of the engine to be matched to the application in each case.
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