Today to discuss with you a lot of car owners are very concerned about the topic, that is, the car's fuel consumption. For car fuel consumption, the Internet over the article about oil-saving overwhelming, the benevolence of the benevolent insight, some older drivers also have their own experience, but I I feel they did not talk about the core issue of fuel consumption, that is, how the car's fuel consumption is generated, the decision of the core factors of car fuel consumption is below Xiaobian to tell you.
When it comes to the fuel consumption of a car, one must first understand the principle that energy is conserved, that energy does not disappear in the air, it can not be derived from the air, it can only be transformed from one form to another. The car is essentially an energy Conversion of machinery is the chemical energy of the fuel into mechanical energy, and then driving the car driving the car need to have a driving force, the driving force is generated by the fuel conversion of mechanical energy.Therefore, the essence of car fuel consumption is the car on the mechanical energy The need to point out is that all the sources of energy on the car are generated by the combustion of fuel, including the use of air conditioning, heating, audio, lighting, etc. Therefore, the more the electronic configuration of the car, the more frequent the use of the car The higher fuel consumption.
Because the car's energy conversion must follow the law of conservation of energy, when you enjoy the comfort to consume a certain amount of energy, this energy is bound to be generated by the fuel combustion, so the car's fuel consumption naturally high.
The level of fuel consumption is essentially the amount of energy conversion, so the fuel conversion efficiency, the demand for automotive energy, will directly affect the level of fuel consumption.
Thermal efficiency of the engine
During the conversion of fuel chemical energy into mechanical energy, only a part of the chemical energy generated by the combustion of the fuel is converted into mechanical energy, and most of the chemical energy is lost. This conversion rate is generally referred to as the thermal efficiency of the engine. The higher the thermal efficiency, The lower the fuel consumption.Now the gasoline engine thermal efficiency is generally between 35% ~ 40%, diesel engine efficiency is higher, generally between 38% ~ 45% .Therefore, with the displacement of gasoline engine and diesel engine, diesel engine More fuel-efficient is the reason.
It is a very difficult task to increase the thermal efficiency of the engine, and from the moment when the engine was born to the present one hundred years, the thermal efficiency has only risen from the initial 20% to more than 30% now, especially in these years , The thermal efficiency of the engine has reached a bottleneck, every one percentage point increase is a huge improvement.
The mechanical efficiency of the engine and the mechanical efficiency of the transmission system
The mechanical energy generated by the combustion of fuel can not be used to drive the car, but also a part of it can be lost.The internal friction (mainly the friction between the piston ring and the cylinder wall) during the operation of the engine consumes a part of energy and drives various accessories such as a generator, Air-conditioning compressors, pumps, etc. also consume a certain amount of energy. This is the mechanical efficiency of the engine. The higher the efficiency, the lower the fuel consumption of the car. This efficiency is mainly related to the structure of the engine and the oil viscosity. In general, High oil will reduce the mechanical efficiency of the engine.
Engine output power, to pass through the transmission system can be passed to the wheels, this process will have the same energy loss, which is the mechanical efficiency of the drive system.Generally, the drive of the front drive is more direct, so the transmission efficiency is higher.And then the drive as a result of transmission The existence of the shaft, the transmission efficiency to be lower.For transmission, manual transmission transmission efficiency up to 95%; and automatic transmission due to the presence of hydraulic torque converter, the transmission efficiency is generally about 80% (Now up to 89%); dual clutch transmission transmission efficiency is generally about 90%, so the most fuel-efficient models must be the first manual gear, and then drive the automatic transmission is the highest fuel consumption.
The mechanical energy obtained from the engine when the car is traveling is mainly used to overcome the various resistances encountered in driving. Specifically, it has rolling resistance, acceleration resistance, hillside resistance and air resistance. The factors that affect these resistances are described below.
Rolling resistance
Rolling resistance is a general term for energy loss caused by the interaction and mutual deformation between the two when the wheel rolls on the road.
The main reason for the rolling resistance is the deformation of the tire and the road surface.
The structure of the tire has a great influence on the rolling resistance. The radial resistance of the radial tire is 20% -30% less than that of the bias tire. The higher the tire pressure, the smaller the rolling resistance. The better the conditions of the road are, the smaller the rolling resistance is. The larger the tire deformation, the greater the rolling resistance.
air resistance
The air resistance of a car refers to the component force of the air force in the driving direction when the car is driving in a straight line. There are mainly the following types: pressure resistance, induced resistance, interference resistance, internal circulation resistance and frictional resistance. Among them, The pressure resistance, which accounts for about 55% to 65% of the air resistance, is generated when the car is moving forward through the air medium and the air in the front of the car is compressed and the pressure acting on the front of the car is increased. Department of the formation of eddy current area to produce negative pressure, so that the role of the rear of the car to reduce the pressure.This pressure difference before and after the formation of pressure resistance, it has a great relationship with the body shape, such as the front and rear shape, windshield Angle, etc. have an impact on the general drag coefficient of the smaller models, the smaller the pressure resistance, the lower the fuel consumption.
Road resistance
When driving on a ramp, the gravitational force along the road shows the gradient resistance of the car.It is clear that it is mainly related to the weight of the car.The heavier the car, the greater the slope, the greater the force to be overcome. The car The higher the fuel consumption.
Accelerate resistance
When the car accelerates, there is an inertia force that is the acceleration resistance of the car.According to the momentum theorem, the larger the car quality, the greater the acceleration, the greater the resistance.Therefore, the heavier the car, the faster the acceleration, the fuel consumption is also The higher.
To sum up the above statement, the core factors that affect vehicle fuel consumption are the following:
1, the thermal efficiency of the engine.
2, engine and transmission system of mechanical efficiency
3, the resistance of the car
In general, the thermal efficiency of the engine, the mechanical efficiency of the car is designed at the factory when the car is designed, there is no way to change the driving resistance of the car is that we can control the factors that affect the maximum driving resistance of the car is the weight of the car, Just reduce the weight of the car, the car's fuel consumption will have a significant decline.This is also the car many companies spare no effort to carry out the most fundamental reason for vehicle weight.
