"Taking reducing the rolling resistance of automobile tires as an example, this paper illustrates the influence of reducing the friction loss of various components on fuel consumption in the power transmission system of internal combustion engine vehicles. This paper mainly discusses the situation of reducing the friction loss of power transmission components of hybrid electric vehicle. Based on the standard gasoline passenger car in 2010, the impact of reducing the loss of power transmission components on the improvement of fuel consumption is predicted.
For reducing greenhouse gas emissions, reducing vehicle CO2 emissions has attracted people's attention as an important topic. If the combustion efficiency of the gasoline engine is increased from 35% to 40%, how much will the fuel economy of the vehicle be improved? If the rolling loss of tires is reduced by 10%, how much can fuel economy be improved? The first research association of the Japanese friction society, "investigation and Research on using automobile tribology to carry out energy saving prediction (2011-2013)" (hereinafter referred to as the Research Association), investigated the impact of reducing the loss of various components of the power train on improving fuel consumption. Based on the research results, this paper gives an example of reducing the rolling resistance of automobile tires to illustrate the impact of reducing the friction loss of various components on fuel consumption in the automobile power transmission system equipped with internal combustion engine. In addition, the hybrid electric vehicle (HEV), which is currently the mainstream environmental protection vehicle in Japan, also includes reducing the friction loss of HEV power train. In addition, in this paper, the loss of all parts related to power transmission, such as pump air loss of engine and rolling friction loss of tire, is treated as friction loss, while the air resistance of vehicle body is not listed as the reduction object and needs to be calculated separately.
2 improvement of fuel consumption to reduce tire rolling friction loss
All tire manufacturers are developing tires (environmentally friendly tires) to reduce the rolling friction loss during vehicle driving. If they can reduce the rolling friction loss of tires, they can reduce fuel consumption, but the effect is not clear. The Japan automobile tire association takes the improvement of fuel consumption when reducing the rolling friction loss of tires as the "contribution rate", and the values of this contribution rate are listed in Table 1. For example, when the contribution rate is 10%, if the tire rolling friction loss is reduced by 20%, the fuel consumption can be reduced by 2%. Table 1 shows the contribution rate that meets the driving conditions. The contribution rate will change with the different models and vehicle quality. Therefore, the range of this value is wide. On a flat road, the contribution rate of vehicles running at a uniform speed exceeds 20%.
Load rate of passenger cars and components in 2010
Considering the fuel consumption of passenger cars, it is necessary to determine the standard specifications of passenger cars. The Institute will take the specifications shown in Table 2 as the standard specifications of passenger cars in 2010. In terms of the standard passenger car specifications in Table 2 formulated by the Research Association, the fuel consumption value when driving on a flat road at a constant speed of 60 km / h is set to 100, and the load rate consumed by each component is estimated. Figure 1 shows the results. The theoretical mechanical output power of the engine is 30 kW (accounting for 40% of the fuel consumption of 100%), the exhaust and cooling losses account for 60%, and the mechanical output power accounts for 50%, that is, in the flat road driving of 60 km / h, the pure output power is 20%, and the friction loss in the engine is 20%. In its distribution details, the pump air loss accounts for the largest proportion. In the pure output power, the friction loss of transmission and differential device is 5%, 15% of the power is transmitted to the wheel, and the rolling friction loss of tire is the largest. In addition, the braking loss is the loss caused by the contact between the brake lining and the brake disc during driving, which is called drag (slip) resistance. Finally, there is 5% aerodynamic resistance, and all fuel energy is consumed.
Table 3 lists the fuel (energy) consumption load rate of each component of the power transmission. The rolling friction loss of tire accounts for 7.5%, and the load rate is the largest among the components of power transmission. As for the load rate, if the impact on fuel consumption is considered, the contribution rate is less than 7.5%, which is far lower than 20% ~ 25% required by Japan automobile tire Association. It can be inferred that it is affected by other effects.
4 report analysis
The research group takes the world's cars as the object, analyzes the actual driving with an average speed of 60km / h, and obtains the following conclusions on reducing fuel consumption:
(1) 33% of fuel energy is used to overcome friction loss in engine, transmission, tire and braking.
(2) the reduction of total friction loss (including air resistance of 5%) has an impact on fuel consumption with triple effect, and the same proportion is adopted to reduce exhaust loss and cooling loss.
(3) when driving at an average speed of 60 km / h, the fuel consumption of vehicles in 2020 can be reduced by 52% compared with that in 2010.
The analysis of the research group is to set the average driving speed from urban roads to expressways as 60 km / h, and the conclusion of the research group will show roughly the same load rate as that of the study as a flat road (35% in the study). It is noteworthy that the reduction of total friction loss, including air resistance, reduces exhaust and cooling losses in the same proportion (Fig. 1). If there is no significant change in combustion efficiency before and after reducing friction loss, it can be recognized as the maximum loss estimation. Therefore, it is assumed that it is an example of reducing friction loss suitable for tires. As can be seen from Figure 1, since the total friction loss is 40%, the tire friction loss accounts for 18.75% of the total friction loss, which is formed in the reduction proportion of the total friction loss (including air resistance). Exhaust and cooling losses are also reduced in the same proportion. However, as the largest loss estimate, it has not reached the loss rate of 20% ~ 25% approved by Japan automobile tire Association.
5 traceability effect
In the estimation of contribution rate, under the condition of reducing the rolling friction loss of tire, the friction loss of other power transmission components is set to remain unchanged, and the comparison is calculated. It is limited that the engine speed remains unchanged, and the friction loss of oil pump and clutch remains unchanged. However, in terms of gears, bearings and other components, if the rolling friction loss of the tire is reduced, the transmitted power is also reduced, and the friction loss will be reduced accordingly. Therefore, as shown in Figure 2, in order to investigate the impact of reducing the tire rolling loss by 10%, the loss of each component (component) is deducted from the loss of some parts (affected parts) upstream of the power transmission to calculate the final fuel consumption. Here, the indicated value is converted as fuel consumption. In addition, in the crankshaft bearing, the influence is reduced due to the high dependence on the speed. The calculation results show that the fuel consumption is reduced by 2.77% and the loss rate is 27.7%. In the value of Japan automobile tire Association, 20% of 20% ~ 25% (loss rate) is the loss rate value when driving at a constant speed on the expressway with large aerodynamic resistance. 25% is the loss rate set for the Research Association at a medium speed of about 60 km / h, and the above calculation is the maximum estimate. Therefore, the contribution rate of 27.7% is an idealized presumption, and the impact of the reduction of the loss of downstream components of the powertrain on the loss of upstream components is called the retrospective effect.
6 approximate actual driving fuel consumption
Figure 2 driving on a flat road at a speed of 60 km / h,
Due to the reduction of tire friction loss by 10%,
Improved fuel consumption (L / 100 km)
The driving distance of fuel is assumed to be 20 km (fuel consumption is 5 L per 100 km). As a 2010 passenger car with a displacement of 1.8 L, it breaks the Convention of practical experience and has good fuel economy. On the other hand, the fuel consumption under working conditions (such as ic08 working condition) stipulates complex acceleration and deceleration requirements, so it is difficult to estimate the fuel consumption by calculation. Therefore, the fuel consumption approximate to the actual driving is calculated using the following assumptions. As shown in Table 2, when a standard passenger car travels uphill at a constant speed of 60 km / h on a slope of 5 °, the acceleration at intersections is similar. On the contrary, the deceleration is similar when going up and down the same slope at the same constant speed. When the driving mileage is 100km, the proportion of uphill mileage is set to 30%, the proportion of driving mileage on flat roads at 60km / h is set to 40%, and the proportion of downhill mileage is set to 30%. It is assumed that this distribution is similar to the actual driving situation. When a vehicle with a displacement of 1.8 L drives uphill on a slope of 5 °, when the direct transmission is zero, it cannot maintain 60 km / h, and the vehicle will slide down.
In addition, when going downhill on a 5 ° slope, leaving the accelerator pedal will cause acceleration. Using this assumption to calculate the fuel consumption, it is necessary to estimate the increased friction loss when going uphill. Table 3 shows that based on the increase of load and engine speed of standard passenger cars, the proportion of friction loss when going uphill on the slope exceeding 5 ° estimated by the research society increases. Using this value and the pure work conversion value accumulated on a slope of 5 ° for 100 m continuously, the energy distribution in Figure 3 can be obtained. Pure work done by 2.2 l gasoline (calorific value) when the vehicle body with a curb weight of 1500 kg needs to be lifted up a slope of 5000 m. As the friction loss will also increase, the fuel consumption is 13.45 l per 100 km. Driving on a flat road is 5 L per 100 km. When going downhill, the fuel cut-off device is used. Since the fuel consumption is 0 l per 100 km, the fuel consumption approximate to the actual driving is equivalent to 16.6 km / L. as the fuel consumption of 1.8 L vehicles when driving safely in the suburbs in 2010, it is more appropriate, which is close to the fuel consumption value under jc08 working condition.
7 friction loss rate of each component
In Figure 1 and figure 3, the load rate of the tire is set to zero (the friction loss reduction rate is 100%). Considering the traceability effect, if the above approximate actual driving is calculated, the fuel consumption is 5.06 l per 100 km. As a result, according to the reduction rate of 6.03 l per 100 km before the tire loss is reduced by 16.1%, it becomes the friction loss rate of the tire similar to the actual driving. Since the contribution rate of driving under the working conditions in Table 1 is 10% ~ 20%, it is more appropriate. Table 3 shows the results of calculating the friction loss rate of various parts of power transmission by the same method. For example, the contribution rate of engine piston is 7.2%. If the friction loss is reduced by 30%, the fuel consumption is reduced by 2.16%. It is possible to approximate the actual driving. For example, table 3 can be used for simple calculation.
8. Reduce the friction loss to improve the fuel consumption of the vehicle
The research meeting conducted research and discussion, that is, compared with the 2010 vehicles in Table 2, the friction loss of various components of the power train can be reduced by 2020. Researchers from automobile parts manufacturers and automobile manufacturers who are members of the Research Association put forward the expected values in Table 3, which can be used not only as technical reference values, but also as values that can be realized in the market. Considering the triple effect of total friction loss and the retrospective effect of the Research Association, if the fuel consumption is calculated according to the loss reduction of various components shown in Table 3, the fuel consumption of vehicles on flat roads in 2020 will be 3.25 l per 100 km, and about 35% improvement in fuel economy can be obtained. In addition, with the fuel consumption on the ramp, the approximate actual fuel consumption of vehicles will become 4.30 l per 100 km in 2020, which improves the fuel economy by 29% compared with 6.04 l per 100 km in 2010. The Japanese government put forward a new target in the G7 regulation in 2015, which will reduce greenhouse gas emissions by 26% compared with 2013 by 2030. Although the years are different, for ordinary passenger cars, due to the progress of tribology technology, the goal of reducing greenhouse gas emissions can be achieved.
9 reduce the friction loss of HEV to improve fuel economy
When HEV vehicles are decelerating and driving downhill, braking regenerative power generation is used to recover the kinetic energy after acceleration and help the battery charge. When the engine combustion efficiency is low, motor assistance (providing auxiliary power for acceleration) is used to improve fuel economy. Here, according to the specifications listed in Table 2, it is considered to be an ideal HEV with only battery pack and motor. As for the above approximate actual driving, taking the high load condition as the representative, it is assumed that 50% of the potential energy is used for the power of the motor. However, this is using the electric vehicle (EV) motor to drive downhill. If the EV Motor is used to drive uphill, the power provided by the battery can reach half of the height on the uphill. It can not be completely determined because of the rolling loss of tires and aerodynamic resistance. It can still reach a height of about 1 / 4, which is consistent with the actual feeling of riding HEV. In addition, when driving on a flat road, the regenerative braking effect cannot be obtained. Therefore, the setting is the same as the fuel consumption of ordinary vehicles.
On the basis of such assumptions, the fuel consumption of HEV in 2010 and the fuel consumption of ordinary vehicles in 2020 with reduced friction loss are calculated compared with the ordinary vehicles in 2010 listed in Table 2. Moreover, when the ordinary vehicle is HEV, it is set to approximate the fuel consumption in actual driving, and the results are shown in Fig. 4. The HEV in 2020, which reduces friction loss, has calculated that its fuel economy has improved by 32% compared with that in 2010. In addition, in 2010, HEV reduced fuel consumption by 25% compared with ordinary vehicles. In this regard, by 2020, HEV will reduce fuel consumption by 28% compared with ordinary vehicles, and it can be expected that the difference will become larger. HEV has better friction reduction effect than ordinary vehicles because it uses the energy consumed in braking deceleration (including engine braking). If the aerodynamic loss is removed, the fuel is only used for the friction loss of power transmission. Reducing the friction loss is directly related to the improvement of fuel economy.
10 conclusion
Taking the effect of reducing tire rolling loss on the reduction of fuel consumption of passenger cars equipped with internal combustion engine as an example, the results of its inference method are studied, and the following conclusions are obtained:
(1) For the reduction rate of total friction loss including air resistance, considering the retroactive effect of reducing exhaust and cooling loss in the same proportion and reducing the loss of downstream components of power train on the loss of upstream components, it can be inferred that the loss reduction of each component has an impact on reducing fuel consumption.
(2) When driving at a constant speed of 60 km / h and set on a ramp with a gradient of 5 °, the proportion of uphill driving is 30%, the proportion of flat road driving is 40%, and the proportion of downhill driving is 30%, which is close to the practical fuel consumption level by simple calculation. In addition, in the approximate actual driving of ordinary passenger cars in 2010, the contribution rate of power transmission components to fuel consumption can be obtained.
(3) According to the prediction of the Research Association, the loss of various components of the power train is reduced. In terms of approximate actual driving, the fuel consumption of vehicles in 2020 is reduced by 29% compared with that in 2010.
(4) Due to the reduction of friction loss, the fuel consumption of HEV in 2020 is improved by 32% compared with that of HEV in 2010. It can be expected that the fuel consumption difference with general vehicles will become larger.
Based on the standard gasoline passenger vehicles in 2010, the forecast is
Our other product:
