Abstract: The factors affecting the fuel economy of truck cranes are analyzed from different working conditions, and the measures that can be taken to improve fuel economy are proposed from the perspective of design.
Keywords: fuel economy condition, truck crane
For a long time in the past, car crane manufacturers and users were not very concerned about fuel consumption, because the proportion of fuel consumption in the operating cost of the crane is small, and the profitability of the crane is good. At present, the competition for the crane crane hoisting business is becoming more and more fierce, the profitability is gradually decreasing, users are paying attention to fuel costs, and since oil is a non-renewable resource, the world oil price is rising rapidly, so research on truck cranes The fuel economy is not only responsible for the users, but also reflects the responsibility of the crane manufacturers to the society. The inevitable result is that they can have more users.
1 working condition analysis
The truck crane is a mobile working device that can travel at high speed on the highway. It has the typical working conditions of the car and the working equipment. At the same time, since most truck cranes share the chassis engine as the power source of the lifting device, it cannot be simple. Considering the fuel economy of the car and the working equipment, it is necessary to find a balance between the power performance and fuel consumption, as well as the power requirements and average fuel consumption at work.
2 driving state fuel economy analysis
The fuel economy evaluation index when the vehicle is in driving state is generally defined as the fuel consumption of 100 km of the vehicle under certain working conditions, that is, the fuel consumption per 100 km (unit: L/100 km). Among them, the constant-speed 100-kilometer fuel consumption is a commonly used relatively simple evaluation index, which refers to the fuel consumption of the car at the highest speed on a good road at a constant speed of 100 km under the rated load. However, the constant speed driving conditions can not fully reflect the actual operation of the car, especially in the driving conditions such as acceleration, deceleration and idle stop, which are frequently seen in urban areas. Therefore, countries have designated some typical cyclic test conditions. Simulate the actual vehicle operating conditions and evaluate the fuel economy of the corresponding driving conditions with its fuel consumption of 100 kilometers.
For the sake of simplicity, we usually use the fuel consumption of the car at constant speed of 100 km as the evaluation index. The calculation formula is: Q=CFb/η (where C is constant, F is driving resistance, b is fuel consumption rate, and η is efficiency)
From the design point of view, the following aspects affect the fuel economy of the truck crane driving state.
2.1 Engine fuel economy
As a main engine, the engine's fuel consumption rate should be considered when selecting the engine (see the engine's universal characteristic map, which is related to the engine's technology and manufacturing level).
2.2 gear position of the transmission system
Increasing gear positions increases the chances that the engine will be in an economical state of operation. For large-tonnage truck cranes, the transmission can have up to 10 to 16 gear positions, which can greatly improve fuel economy, but too many gear positions will make the transmission system too complicated and inconvenient to drive.
2.3 The minimum speed ratio of the transmission system
The truck crane travels at the highest gear in a lot of time, that is, it travels with the gear of the minimum speed ratio, and the minimum speed ratio is selected properly, which can obtain better power performance and good fuel economy.
2.4 Total size and total mass of truck cranes
The size and quality of the vehicle directly determine the various resistances during the driving of the vehicle, which largely determines the fuel economy of the vehicle. At the same time, in order to ensure the power performance of the vehicle, the engine with a larger displacement must be selected when the quality of the whole machine is increased, thereby greatly improving the fuel consumption.
2.5 car crane shape
At present, the maximum speed of truck cranes is constantly increasing. When the driving speed is greater than 50km/h, the influence of air resistance must be considered. Especially before the air resistance coefficient CD value drops to 0.25, lowering the CD value is an effective way to save fuel. Under highway cycling conditions, fuel economy performance increased by 10% after the CD value was reduced from 0.5 to 0.4.
2.6 tires for truck cranes
Truck cranes put various demands on tires. For fuel economy, it is now recognized that radial tires can save 6% to 8% of fuel compared to general bias tires.
3 operating status fuel economy analysis
For the sake of simplicity, we use the QY70 truck crane produced by a domestic company as a sample to analyze the fuel economy during lifting operations.
The crane travels and operates to share the engine. When driving, the power of the engine is transmitted to the tire-driven vehicle via the transmission shaft and the drive axle. When the crane is working, the power of the engine drives the hydraulic oil pump to provide the power of the working device. The specific parameters and output characteristics of the engine are as follows:
3.1 Engine main parameters
Model: WD615.46
Type: water-cooled, in-line, four-stroke supercharged medium-cooled diesel engine
Displacement: 9.726L
Rated maximum power: 266kW/2200r/min
Maximum output torque: 1480N.m/1400~1600r/min
3.2 The main parameters of the working device are
System pressure: 30MPa
Maximum flow: 135ml/r
Maximum power required for system operation: 105kW
It is assumed that the upper part is in the following theoretical working state: the engine maintains a uniform speed of 1500 rpm, and the system consumes 105 kW. According to the universal characteristic diagram of the engine, the maximum output power of the engine at this speed is 228kW, and the corresponding fuel consumption rate under this load is 490g/kW.h, then the fuel consumed for one hour of operation is 44100g equivalent to 55L (take the power of the engine) The output efficiency is 95%).
It can be seen from the above calculation that the engine load rate is very low (about 32%) due to the small power required to get on the train, resulting in an extremely high fuel consumption rate of the engine and high fuel consumption. Therefore, from the perspective of fuel economy, the matching scheme of this QY70 truck crane is unreasonable.
If we choose to use the independent engine on the train, for example, the TBD226II-4 (rated power 115kW) engine is used as the power source for the vehicle. By calculation, the fuel consumption for one hour under the same working condition is 22.66kg or 28L. Therefore, it can save 27L per hour under certain working conditions.
Through the above analysis, from the design point of view, the following aspects affect the fuel economy of the vehicle operating state:
(1) Selection of the engine. The fuel consumption rate of the engine depends on the technology and manufacturing level of the engine itself.
(2) The load rate of the engine. From the general characteristics of the engine, when the load rate of the engine is low, the fuel consumption rate is significantly increased. Therefore, from the perspective of fuel economy, it is necessary to use a low-power engine as much as possible to increase the load rate during work;
(3) The engine speed under regular working conditions. After the engine is determined, how to make the engine work at the economic speed as much as possible is the determining factor for improving fuel economy.
4 Conclusion
The fuel economy of truck cranes is a systematic project, which is influenced by many factors. From the design point of view: for the engine matching of small and medium tonnage truck cranes with a single engine, consider the small and medium tonnage cranes to move the working radius is small, does not exist Frequent long-distance transitions, when the vehicle is matched, more consideration should be given to the fuel economy during operation, that is, to reduce the specific power of the vehicle, not to pursue a higher maximum speed, and to increase the transmission system under highway driving conditions. The maximum total speed ratio and gearbox position achieve good acceleration performance and allow the engine to operate at economic speeds more often. At the same time, select the appropriate power take-off ratio to make the engine run at the economical speed of the crane.
For large-tonnage truck cranes with large total mass, it is difficult to find a balance between driving dynamics and fuel economy during operation. Therefore, it is possible to adopt a separate engine on board, and separately consider fuel economy from both driving and working conditions.
Of course, the above analysis is based on a mechanical speed control engine. When an electronically controlled engine is used, it is theoretically possible to adjust the output characteristics of the engine according to the actual operating conditions and through the program setting of the ECU, thereby achieving an ideal Fuel economy.
Keywords: fuel economy condition, truck crane
For a long time in the past, car crane manufacturers and users were not very concerned about fuel consumption, because the proportion of fuel consumption in the operating cost of the crane is small, and the profitability of the crane is good. At present, the competition for the crane crane hoisting business is becoming more and more fierce, the profitability is gradually decreasing, users are paying attention to fuel costs, and since oil is a non-renewable resource, the world oil price is rising rapidly, so research on truck cranes The fuel economy is not only responsible for the users, but also reflects the responsibility of the crane manufacturers to the society. The inevitable result is that they can have more users.
1 working condition analysis
The truck crane is a mobile working device that can travel at high speed on the highway. It has the typical working conditions of the car and the working equipment. At the same time, since most truck cranes share the chassis engine as the power source of the lifting device, it cannot be simple. Considering the fuel economy of the car and the working equipment, it is necessary to find a balance between the power performance and fuel consumption, as well as the power requirements and average fuel consumption at work.
2 driving state fuel economy analysis
The fuel economy evaluation index when the vehicle is in driving state is generally defined as the fuel consumption of 100 km of the vehicle under certain working conditions, that is, the fuel consumption per 100 km (unit: L/100 km). Among them, the constant-speed 100-kilometer fuel consumption is a commonly used relatively simple evaluation index, which refers to the fuel consumption of the car at the highest speed on a good road at a constant speed of 100 km under the rated load. However, the constant speed driving conditions can not fully reflect the actual operation of the car, especially in the driving conditions such as acceleration, deceleration and idle stop, which are frequently seen in urban areas. Therefore, countries have designated some typical cyclic test conditions. Simulate the actual vehicle operating conditions and evaluate the fuel economy of the corresponding driving conditions with its fuel consumption of 100 kilometers.
For the sake of simplicity, we usually use the fuel consumption of the car at constant speed of 100 km as the evaluation index. The calculation formula is: Q=CFb/η (where C is constant, F is driving resistance, b is fuel consumption rate, and η is efficiency)
From the design point of view, the following aspects affect the fuel economy of the truck crane driving state.
2.1 Engine fuel economy
As a main engine, the engine's fuel consumption rate should be considered when selecting the engine (see the engine's universal characteristic map, which is related to the engine's technology and manufacturing level).
2.2 gear position of the transmission system
Increasing gear positions increases the chances that the engine will be in an economical state of operation. For large-tonnage truck cranes, the transmission can have up to 10 to 16 gear positions, which can greatly improve fuel economy, but too many gear positions will make the transmission system too complicated and inconvenient to drive.
2.3 The minimum speed ratio of the transmission system
The truck crane travels at the highest gear in a lot of time, that is, it travels with the gear of the minimum speed ratio, and the minimum speed ratio is selected properly, which can obtain better power performance and good fuel economy.
2.4 Total size and total mass of truck cranes
The size and quality of the vehicle directly determine the various resistances during the driving of the vehicle, which largely determines the fuel economy of the vehicle. At the same time, in order to ensure the power performance of the vehicle, the engine with a larger displacement must be selected when the quality of the whole machine is increased, thereby greatly improving the fuel consumption.
2.5 car crane shape
At present, the maximum speed of truck cranes is constantly increasing. When the driving speed is greater than 50km/h, the influence of air resistance must be considered. Especially before the air resistance coefficient CD value drops to 0.25, lowering the CD value is an effective way to save fuel. Under highway cycling conditions, fuel economy performance increased by 10% after the CD value was reduced from 0.5 to 0.4.
2.6 tires for truck cranes
Truck cranes put various demands on tires. For fuel economy, it is now recognized that radial tires can save 6% to 8% of fuel compared to general bias tires.
3 operating status fuel economy analysis
For the sake of simplicity, we use the QY70 truck crane produced by a domestic company as a sample to analyze the fuel economy during lifting operations.
The crane travels and operates to share the engine. When driving, the power of the engine is transmitted to the tire-driven vehicle via the transmission shaft and the drive axle. When the crane is working, the power of the engine drives the hydraulic oil pump to provide the power of the working device. The specific parameters and output characteristics of the engine are as follows:
3.1 Engine main parameters
Model: WD615.46
Type: water-cooled, in-line, four-stroke supercharged medium-cooled diesel engine
Displacement: 9.726L
Rated maximum power: 266kW/2200r/min
Maximum output torque: 1480N.m/1400~1600r/min
3.2 The main parameters of the working device are
System pressure: 30MPa
Maximum flow: 135ml/r
Maximum power required for system operation: 105kW
It is assumed that the upper part is in the following theoretical working state: the engine maintains a uniform speed of 1500 rpm, and the system consumes 105 kW. According to the universal characteristic diagram of the engine, the maximum output power of the engine at this speed is 228kW, and the corresponding fuel consumption rate under this load is 490g/kW.h, then the fuel consumed for one hour of operation is 44100g equivalent to 55L (take the power of the engine) The output efficiency is 95%).
It can be seen from the above calculation that the engine load rate is very low (about 32%) due to the small power required to get on the train, resulting in an extremely high fuel consumption rate of the engine and high fuel consumption. Therefore, from the perspective of fuel economy, the matching scheme of this QY70 truck crane is unreasonable.
If we choose to use the independent engine on the train, for example, the TBD226II-4 (rated power 115kW) engine is used as the power source for the vehicle. By calculation, the fuel consumption for one hour under the same working condition is 22.66kg or 28L. Therefore, it can save 27L per hour under certain working conditions.
Through the above analysis, from the design point of view, the following aspects affect the fuel economy of the vehicle operating state:
(1) Selection of the engine. The fuel consumption rate of the engine depends on the technology and manufacturing level of the engine itself.
(2) The load rate of the engine. From the general characteristics of the engine, when the load rate of the engine is low, the fuel consumption rate is significantly increased. Therefore, from the perspective of fuel economy, it is necessary to use a low-power engine as much as possible to increase the load rate during work;
(3) The engine speed under regular working conditions. After the engine is determined, how to make the engine work at the economic speed as much as possible is the determining factor for improving fuel economy.
4 Conclusion
The fuel economy of truck cranes is a systematic project, which is influenced by many factors. From the design point of view: for the engine matching of small and medium tonnage truck cranes with a single engine, consider the small and medium tonnage cranes to move the working radius is small, does not exist Frequent long-distance transitions, when the vehicle is matched, more consideration should be given to the fuel economy during operation, that is, to reduce the specific power of the vehicle, not to pursue a higher maximum speed, and to increase the transmission system under highway driving conditions. The maximum total speed ratio and gearbox position achieve good acceleration performance and allow the engine to operate at economic speeds more often. At the same time, select the appropriate power take-off ratio to make the engine run at the economical speed of the crane.
For large-tonnage truck cranes with large total mass, it is difficult to find a balance between driving dynamics and fuel economy during operation. Therefore, it is possible to adopt a separate engine on board, and separately consider fuel economy from both driving and working conditions.
Of course, the above analysis is based on a mechanical speed control engine. When an electronically controlled engine is used, it is theoretically possible to adjust the output characteristics of the engine according to the actual operating conditions and through the program setting of the ECU, thereby achieving an ideal Fuel economy.
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