In general, in addition to power other than electricity, the other is a vehicle internal combustion engine. Therefore, "hybrid" is often referred to as "oil-electric hybrid."
First, the basic working principle of hybrid vehicles
Compared with pure electric vehicles and fuel cell vehicles (and simple solar vehicles ), it can be said that hybrids use a less radical "moderate approach."
All of its energy is ultimately derived from on-board fuel, which is converted from mechanical to mechanical by conventional thermodynamic processes.
That is to say, the energy efficiency of the hybrid vehicle will not be higher than the optimal thermal efficiency of the vehicle internal combustion engine.
The basic starting point for energy saving and emission reduction is to optimize the working range of the engine.
(It can be analogous to a continuously variable transmission. The continuously variable transmission can find the operating point with the lowest fuel consumption rate at a certain power, and the hybrid can control the engine at the most economical point in the entire characteristic map.)
For example, the most economical operating point of the engine is: n = 2000 rpm, Pe = 40 Kw.
When the vehicle is lightly loaded, for example, only 20 Kw of power is required. At this point, the engine is still operating at the most economical point, output 40Kw power; the excess 20Kw is recovered by the electrical system and stored in the battery. (Or the engine is completely shut down, working solely from the electrical system.)
The coordination of the speed and the speed of the vehicle is achieved by the transmission ratio of the drive train, so many HEVs are equipped with a continuously variable transmission.
When the vehicle load is large, for example, 60 Kw of power is required. At this point, the engine is still operating at the most economical point, output 40Kw power; less than 20Kw is provided by the electric system, the battery is discharged externally. (Or the engine is completely shut down, working solely from the electrical system.)
The specific reasons why hybrid technology can improve fuel economy and emissions can be found in Chapter 2, Section 5 of Automotive Theory.
At the current state of the art, compared with conventional power vehicles, the fuel consumption of hybrid vehicles can be reduced by about half, and the level of pollutants discharged is reduced more.
Second, the type of technology
Hybrid vehicles are divided into series, parallel and hybrid according to different combinations of "oil" and "electric". The more common ones are the first two.
(1) The so-called "series" is the engine-generator-motor-vehicle transmission...lined in a line. Between the generator and the motor is a battery port that is controlled by the controller. Basic energy flow:
1 The engine works at the most economical point, and the chemical energy of the fuel is converted into mechanical energy by the internal combustion engine (or the engine is turned off, and the battery is completely powered);
2 drives the generator to be fully converted into electrical energy;
3 If the amount of power generation is insufficient, it is replenished by the battery; if the amount of power generation exceeds the demand, the excess is stored in the battery;
4 The electric energy is transferred to the motor after being adjusted by the battery, and is converted into mechanical energy again;
5 mechanical energy drives the vehicle transmission system to provide drive wheel driving force...
Since all energy is subjected to power-electrical repeated conversion, the efficiency is poor; and due to the serial arrangement, all powertrains must meet the maximum power requirements of the vehicle, and the volume and quality are difficult to control.
However, the tandem scheme has no direct connection between the engine and the drive wheels. The engine work is not affected by the driving environment and the driver's intention. It is easy to control at the ideal working point, and the whole control system is simpler (relative parallel and hybrid).
At present, the efficiency of a series hybrid vehicle is acceptable if a more efficient generator and motor are selected.
(2) The so-called "parallel" means that both "oil" and "electricity" can drive the car alone. Its core electrical system is a motor under the control of the controller, which can act as a motor or generator in a timely manner.
1 The engine works at the most economical point, and the chemical energy of the fuel is converted into mechanical energy by the internal combustion engine (or the engine is turned off, and the battery is completely powered);
2 If the power is insufficient, the battery is discharged, the motor outputs mechanical work externally, and the mechanical work is combined with the mechanical work from the internal combustion engine under the coordination of the power synthesis device to jointly drive the vehicle; if the engine power is excessive, the power synthesizing device will partially power Assigned to the motor, the motor generates electricity and stores the remaining energy;
3 mechanical power output from the power synthesis device drives the vehicle...
Obviously, the parallel solution is more complicated, and the engine is mechanically connected to the drive wheel, which requires higher controllers.
But its biggest advantage is its high efficiency. A large portion of the drive wheel output power comes directly from the engine without the need for a power-electric conversion. In addition, since the power of the internal combustion engine and the electric motor are added to meet the driving demand, their respective rated powers can be much smaller than the power demand of the whole vehicle, and can be miniaturized and lightened, which is necessary for many small vehicles. of.
(3) There is also a kind of "mixed". In theory, its overall performance is the best; but the system composition is very large, the transmission layout is very difficult, and the requirements for the control system are also very high. Not much to introduce here.
Third, the characteristics
The advantages of hybrid technology include:
(1) The powertrains used are all inherited from the prior art, and there are not many equipment that need to be completely redeveloped.
(2) Since all energy sources are essentially derived from on-board fuel, the contribution of fuel economy and emissions can be accurately quantified.
(3) It is currently the only technology that can recover braking energy (partial).
(4) The battery technology requirements are relatively low.
(5) Use ordinary gas stations.
The main problems are:
(1) Not completely rid of dependence on fossil fuels. This is the most deadly flaw, so hybrid technology is generally considered to be just a transition before the popularity of fuel cell vehicles.
(2) Among all electric vehicle technologies, the control system is the most complex. The requirements for controller hardware and software levels and on-board signal communication are very high. (Therefore, there is a difference between the performance of an actual hybrid vehicle and the simulation calculation.)
(3) Since the working conditions of each power unit are frequently switched, there is a problem in their life. Moreover, a large number of transient working processes have a certain negative impact on fuel consumption and emissions.
(4) The development of high-efficiency, low-emission internal combustion engines specifically for hybrid vehicles needs to be accelerated.
(5) High R&D and manufacturing costs.
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