I. Overview of the fuel economy of automobiles
The fuel economy of a car is one of the main features of a car. It refers to the ability of a car to complete a unit's transportation with minimal fuel consumption. To evaluate the amount of fuel consumed by a car traveling 100 kilometers, since the cost of fuel consumption in automobile transportation accounts for about 42% of the total cost, the increase in fuel economy means a decrease in the cost of transportation of automobiles and an increase in economic efficiency.
Since the fuel consumption of automobiles is related to many factors such as engine type, structural design, manufacturing process level, adjustment status, fuel quality, road conditions, traffic conditions, climate, driving technology, etc., the indicators of fuel economy are based on road tests or Test bench test results to assess, can also be estimated through theoretical analysis.
Vehicle fuel consumption test methods are generally divided into indoor tests and road tests according to different test conditions. The indoor test is a cyclical test of the automobile on a rotary drum test bench. Although there are many advantages, it is difficult to reflect the actual situation when the automobile is driving on the road, and it is less used in the actual automobile fuel economy experiment. Road tests are divided into non-control road tests, control road tests and road cycle tests according to the control procedures of various influencing factors. Uncontrolled road tests must be carried out in long-distance trials with large numbers of vehicles in order to obtain more accurate data. Although the test is very close to the actual situation, it is seldom used because it takes a long time and costs a lot. Control road tests are also rarely used due to the constraints of road conditions. Road cycle tests mean that vehicles are tested on prescribed roads in accordance with prescribed regulations, and that automobile throttle portals are used to fully accelerate accelerated fuel consumption tests, etc. Speed ​​fuel consumption test, multi-state fuel consumption test and average fuel consumption test under limited conditions. It has the advantages of short test time, simple test instruments, and good data reproducibility, so this method is widely used.
Second, automotive fuel economy index
(I) Evaluation indicators
The evaluation index is used to evaluate the fuel economy of various models. In China, the number of liters of fuel consumed by a car traveling 100 kilometers, ie, L 100km, is used as a unit of measure, and is denoted as Qs. The evaluation method is as follows: 1 Total mass 2 For 5-60t trucks, the evaluation index Qs takes the six fuel consumption Qv, which is Qs = Qv (L 100km).
2 For gasoline trucks with a total mass of 60 to 150 tons, the evaluation index Qs takes the weighted value of the fuel consumption Qv at six operating conditions and the constant speed fuel consumption Qc at a vehicle speed of 45 km h, ie, Qs=0. 5Qv+ 0. 5Qc (L 100km).
(II) Operating Fuel Consumption Indicators
When the car is in operation, the fuel economy indicator is the indicator of the operating fuel consumption. It is the control standard for the amount of fuel used by the transportation company to deliver the driver to complete a certain transport production task according to national, regional or corporate standards.
The calculation of operating fuel consumption is divided into different operating conditions according to different combinations of road and traffic conditions, ambient temperature, altitude, and number of loads.
Calculate the fuel consumption of the same operating conditions, and then add the fuel consumption of different operating conditions to obtain the total operating fuel consumption.
(III) Assessment Index
1 The assessment index of the fuel consumption of the vehicle produced by an automobile factory or a retrofit factory is the specific fuel consumption q.
Q= Qs GL 100KM Qs evaluation index of this model, L 100km G car standard total quality, t.
If q = qL is passed, qL is the national limit indicator.
2 The assessment index for the fuel consumption of transport enterprises: The Rs for comprehensive fuel consumption is used as the assessment index.
Rs=( TjQbj )( TjQsj ) 1 Type: The turnover amount of a model Tj completed in the assessment period, 100tkm The benchmark unit consumption of a Qbj company model, L 100km Qsj The national benchmarking unit consumption of a model, divided into one grade, two grades , L 100km.
Different levels of Qsj are substituted into the above formula, and if the requirements are satisfied, the corresponding level of assessment is passed.
Third, measures to improve the fuel economy of automobiles
It can be known from the equation of fuel consumption of automobiles that the fuel economy of automobiles depends mainly on the effective fuel consumption of the engine and the running resistance of the vehicle. All measures that contribute to the reduction of the effective fuel consumption of the engine and the reduction of the vehicle's running resistance can improve the fuel economy of the vehicle. Therefore, there are many ways to save fuel, mainly to analyze the measures to improve fuel economy in terms of structural design and use of technology.
(I) Improve fuel economy from structural design
1 Reasonably choose car engine. To select an engine with equivalent power, if the engine power used is too high, the load rate will decrease and the fuel economy will deteriorate. If the engine is too small, the power performance of the vehicle will be affected. To expand the selection of diesel engines. Diesel engine has higher thermal efficiency than gasoline engine, especially when the diesel engine's effective fuel consumption rate is about 20% lower than the gasoline engine's average of 45% under partial load, and the diesel engine has less pollution.
2 Optimize the structure of the engine. The application of new engine technologies to achieve timely control of automotive engines is an effective measure to improve the fuel economy and dynamics of automobiles. Increasing the compression ratio is an important measure for improving the fuel economy of gasoline engines, but it cannot increase too much, otherwise there will be phenomena of engine deflagration and surface ignition, and at the same time, the harmful substances in emissions will increase.
3 Use stratified fuel with a direct injection engine and a lean mixture. Improve the formation, distribution, and fueling of the mixture, create a mixture of suitable concentrations, improve fuel economy, and reduce emissions pollution.
4 uses closed cylinder technology. Closed-cylinder technology adopts the method of closing the intake and exhaust valves to stop the cylinders. It not only can increase the load rate, but also can reduce the pump loss and drive the loss of the valve mechanism. The fuel saving effect is obvious. This technology is often used in limousines. . Because these vehicles are particularly powerful in order to meet the maximum speed and acceleration time, most of the driving situations are that when the engine is under low load, the technology of closing the cylinder can reduce the number of cylinders to start working, so as to achieve the goal of fuel economy.
5 uses overdrive design. The purpose of gearbox design overspeed is mainly to save fuel, so overdrive is also called economical gear.
6 Reduce the car's service quality. Its main approach is to use computer optimization design; make full use of the strength of the material and improve the rigidity of the structure; use high-strength low-alloy steel, aluminum alloys, magnesium alloys, plastics, ceramics and various fiber reinforced materials to manufacture certain parts; improve the car Structure, Simplified Automotive Transportation System; FF Part Position (Front-engine front-wheel drive); High-reliability tires without equipment tires; Single-piece spring suspension; Load-carrying body; Air-cooled engine; Reduced body size; Add devices, etc.
7 Improve the streamlined shape of the car. Improve the appearance, reduce the coefficient of living air resistance, and reduce the power consumption of air resistance.
8 uses radial tires. This kind of special tire structure makes its rolling resistance coefficient smaller than that of common inclined tires, and the higher the speed difference is, the more effective the fuel saving effect is.
(II) Increasing fuel economy from the use of technology
For a certain vehicle model, it is generally possible to reduce the fuel consumption and improve the fuel economy of the vehicle by improving the technical condition of the automobile and improving the operational skill level of driving.
1 Keep the car's good gliding performance. Sliding performance is usually expressed in terms of coasting distance and coasting drag coefficient. The national standard GB3798 83 automobile overhaul engineering technology conditions: the car runs on a straight, dry and hard road with no load, the initial speed is 30km, the taxiing distance should not be less than 220 meters; when using the rally meter, it starts to pull the car. The pulling force should not exceed 1 4% of the vehicle's weight (ie no more than 0.0147). Keeping the car's good gliding performance, the function of the chassis consumption is small, and the fuel consumption will inevitably decline. This will enable the car to maintain a good fuel economy. On the contrary, the drive gear meshing clearance is too small, the bearings and the oil seal are too tight, and the front wheels Locating misalignment, low tire pressure, and too small a brake gap will all reduce glide performance, increase running resistance, and reduce fuel economy.
2 Keep the engine in a good technical condition. The engine technology is in good condition, not only makes the car have good dynamic performance, but also makes it have good fuel economy. To check and maintain a sufficiently high cylinder compression pressure at regular intervals, if the cylinder pressure is insufficient, not only the engine power decline but also the combustion speed will slow down, resulting in a decline in fuel economy. Maintaining the normal operating temperature of the engine, the 80 90 has the lowest fuel consumption, the highest torque and power, and the high or low water temperature has an impact on the fuel consumption of the engine. Keeping the fuel supply system working well provides an ideal economic mixture. Keep the ignition system in good condition. Ensure adequate spark energy. Proper ignition timings are all conducive to improving fuel economy.
3 Improve driving skills. Practice has proved that good driving technology can greatly reduce the fuel consumption of the car. Different levels of driving can drive the same type of car under the same conditions of use. The fuel consumption can differ by 22% 40%. To reduce the fuel consumption, in addition to Reasonably start, warm up, start and slow down during driving, maintain normal cooling water temperature, and use brakes safely and reasonably. It must be suitable for gear selection and speed. The rational use of the trailer transport method will increase the engine load rate, reduce the fuel consumption rate, and improve the fuel economy.
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