How to reduce internal combustion engine emissions

2022-08-09
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How to reduce internal combustion engine emissions

when manufacturers plan to enable mass-produced engines to achieve more stringent emission standards than the global emission rules in the next period, they need to find ways to reduce the waste and greenhouse gas emissions in the engine. In the long run, there may be solutions to effectively replace internal combustion (IC) engines in the future, but in the medium and short term, this goal can only be achieved by improving the efficiency of gasoline and diesel engines. Electrification of the auxiliary system helps to reduce the additional loss and hybrid performance of the powertrain and reduce emissions, but how should engine designers deal with the challenge of improving performance to reduce internal combustion engine emissions

at present, the global vehicle emission standards are becoming more and more stringent. Further reducing the emission of nitrogen oxide and particles may increase the cost of post-treatment. Some engine designers believe that the improvement of gasoline technology in the future will help to develop cheaper solutions and find more practical alternatives to light-weight diesel engines. Increasing emission limits may make engine designers no longer choose two-stroke cycle engines

however, the development trend of miniaturization of engine size has led many designers to reconsider the two-stroke design, although they are more familiar with the advantages and technical challenges of miniaturization of four stroke engines

designers hope to achieve the performance of larger engines through turbocharging or supercharging, which can also reduce fuel consumption and improve emission efficiency. Reducing the size of the engine will lead to an increase in cylinder pressure and temperature, and the crankshaft and bearing shells need to be increased, which will lead to increased friction - which in turn offsets the benefits of reducing the size of the engine

in addition, David hemming, engineering director of Prodrive, also pointed out the trouble of excessive oil supply under high load conditions. Due to the use of turbocharging, the intake pressure increases, and the compression ratio needs to be reduced. Before that, engine designers were helpless to solve the problem of increasingly low efficiency. The two-stroke engine and the four stroke engine with twice the power stroke will help to solve this low-speed torque problem

variable compression stroke and fuel

at the Geneva auto show last March, Lotus Engineering Company showed its omnivore two-stroke model, with unique variable compression ratio system (VCR), turbocharger and wet oil pan. Without valve mechanism, the VCR system can be operated up and down through a ball (including spark plug and oiler), eccentric cam and stepping motor installed on the cylinder head to achieve a compression ratio of 40:1. The project was set up by the UK Department of environment, food and agriculture (Defra) to design an engine that can use renewable energy (such as bioethanol) and gasoline as fuel

Jamie Turner, chief engineer of powertrain research and development of Lotus Engineering Company, said in an interview with international automotive engineering: now this company has completed the preliminary development of omnivore series fueled by gasoline and E85 ethanol, and some results are surprising. "For example, the hydrocarbon and carbon monoxide emissions of homogeneous charge compression ignition (HCCI) four stroke engines have increased. Basically, the hydrocarbons in the fuel will not be oxidized to carbon monoxide and carbon dioxide all the time, which is not the energy conversion process in the cylinder during internal combustion.

the early results of lotus omnivore variable compression two-stroke test surprised engineers.

"However, we have found that if we have the opportunity to squeeze further, a reaction force can be generated, which can greatly reduce the emissions of hydrocarbons, carbon monoxide and nitrogen oxides. Now it is generally believed that we can't choose - either the odd number of nitrogen oxides or the lower double number of nitrogen oxides, and the emissions of ethanol are much lower than those of gasoline. As for hydrocarbons, we can achieve the low emissions of four stroke engines using simple oxidation catalysts High volume. "

"Now, people have found that for homogeneous charge compression ignition engines, engine idling is the most difficult problem to solve. We need to deal with engine idling when the speed is 450rpm. Interestingly, if the exhaust gas temperature is taken as a standard to measure internal combustion efficiency, the exhaust gas temperature under this condition will reach 94 ° C - even a pot of water cannot be boiled. But the irony is: under this condition, we have to shut down the engine, Because the catalyst needs to be cooled. We can end idling, not to save fuel (which is also very limited), but to avoid exhaust gas post-treatment and prevent the engine from stalling. "

different strokes

ricardo also set up a 2/4sight project to study the performance of the two-stroke cycle. The electric equipment company also participated in this project. It developed a direct fuel injection system, advanced engine control system and Ma 2t4, which is very helpful to the valve mechanism conversion technology. Two British universities participated in the project - Brunel University was responsible for the testing and development of single cylinder engines, while Brighton University was responsible for the testing of multi cylinder engines and the analysis of internal combustion/cooling systems

ricardo adopts the traditional four valve valve valve mechanism with upper cam per cylinder, but it is refitted into a structure that can be converted between two-stroke and four stroke. In this sense, this engine can operate in two-stroke mode under high load and low speed, which is often encountered by engines with reduced size

"this solution is based on the basic two-stroke poppet valve developed by us about 15 years ago, and is committed to connecting the ventilation port to the engine and reducing residues," said Bob Gilchrist, chief engineer of technology and clean energy of Ricardo (UK)

now, engineers can install a 2/4sight 2.1-liter V6 gasoline engine into the car. It can be used as a small substitute for the 3.4-liter V8 engine. It adopts the extended range strategy, including a twin turbocharger and a supercharger driven by continuous variable transmission (CVT), which increases the range with variable transmission rate. "With this solution, you can get a two-stroke torque when you need it, or you can operate under four stroke conditions," Gilchrist explained

to achieve this goal, you must be able to switch between loops. Richardo adopts an electro-hydraulic valve mechanism, which can provide unlimited adjustment for valve timing, valve lifting and durability. The collected data will be used to define a mechanical valve mechanism, which will be loaded on the vehicle with 2/4sight and connected to the engine. By adopting this design, we hope to achieve variable valve timing, valve lifting and durability without infringing Honda VTEC patents

ricardo's 2/4sight R & D project is committed to the free conversion between two-stroke and four stroke,

at the same time, it overcomes some disadvantages caused by the reduction of engine size

(Honda is the originator of variable valve timing technology, and VTEC technology is the world's first patented technology in the field of variable valve timing. After decades of development and reform, Honda housekeeping technology has been upgraded to i-vtec, "I" means smart and intelligent. - editor's note)

the simulation test results so far show that compared with the 3.4-liter V8 engine, the 2.1-liter V6 engine adopts this design, It can reduce fuel consumption and carbon dioxide emissions by 27%, while maintaining the same power and torque output

"the purpose of developing this technology is to make the cost of gasoline engines cheaper than diesel engines, but in terms of reducing the cost of carbon dioxide, gasoline engines will still be higher than diesel engines," Gilchrist concluded

combat with friction

additional losses are the research and development focus of Ford engineers. After raising funds from the British technology strategy committee, Ford began to work with BP and Mahler power transmission to optimize the internal combustion engine to reduce additional losses. The goal is to reduce fuel consumption and carbon dioxide emissions by 5% to 10% through a series of projects. Engineers optimize the offset crankshaft in terms of lubricating oil, surface polishing and friction surface material effect, thermal micro treatment, reducing emissions and improving efficiency

"we are trying to reduce the internal friction of the engine - the friction between pistons, valve mechanisms and bearings," Ford project leader Andy scarisbr hopes to jointly promote the sustainable and healthy development of the polyurethane industry, ick told international automotive engineering. Ford and many other automobile manufacturers have independently researched and developed surface friction, surface materials, oil and oil additives, but scarisbrick believes that other companies have not seriously studied the combined effect of these factors. "From the perspective of the effect wavefront only, we have seen some directional results: some of the basic theories of the wavefront are not correct enough.

this work was completed by Imperial College London, and the result data will be used for the study of the wavefront diagram of lubricants and materials. Now the nine month experimental design has begun." I hope we can explore the way in which those factors interact, so as to optimize the whole system, " Scarisbrick said. He expects to eventually increase maximum efficiency by 4%

as long as it comes to thermal management, "we must pay attention to the thermal micro treatment inside the engine itself. For example, during the heating process, can we try to heat the area near the piston? This is where we hope the oil will play a different role. It will not work until the oil gets hot. It is very important to only heat the plug during the exhibition for three consecutive days, so we are looking for a solution." This project has made some research and development progress on eccentric crank, which directly affects the normal operation of safety barriers. "We have done some early development work, hoping to find other benefits that we haven't found before," scarisbrick said. These data results come from diesel engines, and it has been proved that the possible benefits will not be limited to fuel consumption

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