Measures for the sustainable development of concrete construction machinery

With the vigorous development of infrastructure construction in our country and the implementation of the Western development strategy, construction machinery in our country has seized a great opportunity for development. At the same time, the state has also strengthened its control over the protection of the ecological environment during development. For instance, the control of engine exhaust emissions and the noise control during the operation of construction machinery, etc.

The use of construction machinery must not harm the human living environment. This requirement has become an inevitable trend. This prompts us to enhance and improve the technical quality of concrete construction machinery. If one only focuses on reducing costs without simultaneously keeping their products up-to-date, it will ultimately affect the future of the products themselves.

We believe that the current sustainable development technologies for concrete construction machinery should mainly focus on: ① Energy conservation; ② Reduce pollution; ③ Improve performance; ④ Improve efficiency. This article mainly describes the aspects of energy conservation and pollution reduction.

Measures for energy conservation and improvement of engine exhaust pollution

Energy conservation not only brings great economic benefits to users, but also helps protect the Earth's resources and contributes to the sustainable development of human society. Energy conservation and pollution reduction are closely related. The process of energy, from its extraction, transportation, processing to its use, is the most polluting to the Earth's environment. The harmful substances in the exhaust gas emitted by diesel engines mainly include CO, HC, NOx, sulfur-containing compounds and carbon particles. The carbon particles emitted by a general diesel engine due to incomplete combustion are 30 to 40 times that of a gasoline engine.

At present, the state's control over the exhaust emissions of motor vehicles is gradually being promoted. All kinds of motor vehicles that do not meet the Euro II emission standards will not be allowed to enter big cities. In terms of reducing engine exhaust emissions, computer-controlled turbocharged intercooled diesel engines have unique advantages, such as the VOLVOFMl2 engine. The computer-controlled fuel injection system mainly consists of three parts: sensors, actuators and electrical control units. The electronic control unit is an engine computer or a central processing unit. There are several types of sensors, including intake air temperature and pressure sensors, load sensing sensors, and oil temperature and pressure sensors. The actuator is a single pump driven by an electromagnetic valve.

The signals sensed by various sensors are aggregated into the engine computer or central processing unit for comprehensive analysis, and then converted into control signals to control the optimal fuel injection volume, injection timing and intake volume of the diesel engine. Some electronically controlled diesel engines can also analyze the composition and content of the exhaust gas emitted after combustion. When the combustion is incomplete and black smoke is emitted in the exhaust, the diesel engine can immediately adjust the concentration of the diesel mixture and promptly eliminate this phenomenon.

This diesel engine, due to the adoption of worm gear turbocharging and intercooling technology, further purifies the exhaust gas produced by the primary combustion through secondary combustion in its exhaust gas recirculation system (EGR system), which also improves the energy utilization rate and significantly reduces the fuel consumption of the engine. This type of electronically controlled diesel engine can all meet the exhaust emission standards above Euro II. Another significant advantage of computer-controlled diesel engines is that their power output performance has been greatly enhanced. When the load rate of the diesel engine changes, the computer can immediately sense it and promptly adjust the output force of the diesel engine.

For engines without supercharging and intercooling, exhaust filters can be used to improve exhaust emissions. For instance, exhaust filters that use ceramic foam bodies and wall-flow ceramic honeycomb bodies, or those based on the electrostatic particle capture principle, have a good effect on capturing carbon particles in exhaust gas. The exhaust filter using zeolite as the adsorbent has a good effect on absorbing HC compounds in the exhaust gas. In addition, adding smoke suppressants to diesel and not using inferior diesel fuel containing heavy diesel components are both effective measures to improve combustion efficiency and reduce emissions.

Another approach is to appropriately limit the maximum power output of the engine. For instance, the lOPE diesel engine of the Isuzu CXZ81Q truck has achieved the Euro I emission standards by adopting this method.

Measures to reduce thermal pollution from engines and the entire machine

The thermal pollution generated by the vast number of various types of heat engines around the world is another significant factor in deteriorating the Earth's ecological environment and climate. The greenhouse effect it generates has led to the melting of glaciers, the rise of sea levels, climate variation, and the frequent occurrence of droughts and floods. The power machine, hydraulic circuit and certain actuating mechanisms of concrete construction machinery are all heat sources.

Therefore, reducing the thermal pollution caused by concrete construction machinery is also an issue that relevant manufacturers should pay attention to. At present, what can be achieved is that in the selection of engines, engines with high energy conversion rates and low heat consumption should be chosen as much as possible. In the design of mechanical moving parts (especially high-speed moving parts), friction should be minimized and lubrication enhanced as much as possible. In the design of hydraulic circuits, the resistance of pipeline flow should be reduced as much as possible to minimize heat generation. But the most fundamental improvement still awaits the advent of new types of power machines to replace the current heat engines.

Measures to reduce noise from concrete construction machinery

With the further deepening of national environmental protection control, environmental protection departments will gradually phase out backward construction machinery and construction methods that cause serious noise pollution. Therefore, further reducing the operating noise of concrete construction machinery is a problem that all concrete machinery manufacturers must pay attention to.

Excessive noise mainly causes damage to the human auditory system. According to the data, if a person is exposed to a noise environment of 85 decibels for a long time, it will cause hearing loss. Noise above 90 decibels can cause deafness or severe deafness. The short-term limit that the human ear can tolerate for strong noise is approximately 125 decibels. Sound frequencies below 500 Hertz are called low-frequency noise (such as the low-speed driving sounds of air compressors, cars and tractors), sound frequencies between 500 and 1000 Hertz are called medium-frequency noise, and sound frequencies above 1000 Hertz are called high-frequency noise. The human auditory domain is within the range of 20 to 20,000 Hertz, and it is most sensitive to sounds around 1,000 Hertz.

The noise generated by concrete construction machinery can be classified into the noise of the power machine (such as engines, motors, oil pumps, etc.) and the noise of the transmission and actuator. The following introduces several noise control measures respectively.

(1) Sound insulation and noise reduction technology: Sound insulation and noise reduction technology mainly uses sound insulation enclosures to isolate the sound source from the outside world. The sound insulation enclosure is generally lined with damping layers or damping coatings to enhance the sound insulation effect. For hot engines, to meet the requirements of heat dissipation and ventilation, there must be air inlets or exhaust ports. At this time, mufflers need to be installed on the air inlets and exhaust ports to maintain the sound insulation effect. This method can generally reduce noise by 15 to 30 decibels.

(2) Vibration isolation and noise reduction technology: Noise is often caused by the vibration of machines or fluids. Therefore, reducing vibration is a more fundamental method for noise reduction. The noise generated by the operation of the oil pump includes hydraulic noise and mechanical noise. Hydraulic noise is generated by cavities in the liquid and the periodic pulsation of pressure and flow when the liquid is discharged. Mechanical noise is caused by the imbalance of rotating parts, poor bearings and component resonance.

Generally, hydraulic noise is the main component of pump noise. It increases with the rise of pump speed, and the noise frequency also increases with the increase of pump speed. Improving the design of pumps and hydraulic systems is the fundamental way to reduce hydraulic noise. In addition, sound insulation enclosures can also be used. When the mechanical vibration generated by the power components and their supports is obvious, the application of vibration isolation and noise reduction technology can achieve remarkable results.

Generally, rubber vibration isolation pads (blocks), springs and cork are used as vibration isolation components. More advanced ones include gas-liquid vibration isolation methods such as oil-gas springs. The installation method also has a significant impact on the vibration isolation effect. For instance, the cab of a VOLVO truck is equipped with double spring vibration damping and lined with sound-absorbing materials, achieving a significant noise reduction effect inside the cab.

(3) Sound absorption and noise reduction technology: A technology that absorbs and attenuates the energy of sound waves. Sound-absorbing materials are generally porous sound-absorbing materials. In porous materials, 90% are tiny interconnected cavities. These micro-cavities exert viscous resistance and frictional effects on vibrating air molecules, converting the vibrational kinetic energy of the molecules into thermal energy and causing the attenuation of sound energy.

(4) Acoustic wave cancellation technology: The silencing system that adopts acoustic wave cancellation technology is composed of a set of acoustic wave detectors, information processors and acoustic wave synthesizers. The detector sends the data such as the intensity and direction of the noise it senses to the information processor. After analysis, the information processor instructions the acoustic wave synthesizer to generate an acoustic wave signal with the same amplitude as the noise wave but opposite vibration direction, thereby eliminating the noise. This technology has been applied in noise reduction for air conditioning systems in the UK, achieving a noise reduction effect of around 10 decibels.