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Recently, it has been reported that the LNG vehicle in Anhui Province was first opened to private enterprises. Soon, the big trucks from Hefei to Hangzhou could be settled with "one breath." "Oil to gas" is not new in the field of cars, especially taxis, but the industry has not paid much attention to the "oil to gas" of commercial vehicles.
With gasoline and diesel prices rising steadily, natural gas vehicles are increasingly showing their unique advantages in terms of fuel economy. Many small gasoline vehicles and even large passenger cars and trucks also carry out "oil-to-gas" changes in their engines in an attempt to reduce energy costs.
What principle is based on the "oil to gas" engine? After the engine has been changed from gas to gas, it can only be operated with gas power. Can it be used in both fuel and gas mode? Does the engine face safety problems after the engine has been changed to oil? Has the engine "oil to gas" project been approved by the relevant government agencies? Can the "oil-to-gas" vehicles be subject to annual reviews like traditional gasoline and diesel vehicles, and what are the differences between the annual review and traditional power-driven vehicles?
With these questions, the reporter made an unannounced visit to a number of domestic gas stations and conversion companies that operate the “oil to gas†project.
"Oil to gas" CNG, LNG double parallel
During the interview, the reporter learned that the current “oil to gas†market has mainly been converted into two modes of CNG and LNG. CNG conversion is mainly targeted at light gasoline vehicles such as taxis and private cars. LNG conversion is mainly targeted at trucks. Heavy-duty diesel cars.
The CNG vehicle is converted from a stereotyped gasoline vehicle. In the case of retaining the original vehicle fuel supply system, a “compressed natural gas device for CNG vehicles†is added. The conversion part consists of three systems: a natural gas system, a natural gas supply system, and an oil-gas fuel conversion system. The natural gas system is mainly composed of inflation valves, high pressure globe valves, natural gas cylinders, high-pressure pipelines, high pressure joints, pressure gauges, pressure sensors, and gas quantity indicators. The natural gas supply system consists of natural gas high-pressure solenoid valves, three-stage combined pressure reducing valves, and mixing. And other components; oil and gas fuel conversion system consists of three oil and gas transfer switch, ignition time converter, gasoline solenoid valve and other components. Vehicles modified with CNG can operate in both fuel and gas modes.
There are two ways to modify LNG
The LNG conversion program for heavy-duty diesel vehicles is further subdivided into two modes, which can be converted to the simple gas mode or modified to the form that both fuel and gas modes can be used.
The first type of method is that the original diesel engine is basically unchanged in structure, modified according to the electric ignition method, that is, working according to the working principle of the gasoline engine (the Otto cycle), removing all the fuel systems of the original diesel engine, and reducing the compression ratio to the amount that the natural gas can bear. Value (higher than gasoline engine, generally 8 to 10:1). In addition to the components of the natural gas fuel system - gas cylinders, pressure reducing valves, mixers, etc., an electric ignition system must be added to become a single-fuel vehicle that burns only natural gas. This conversion method is relatively simple, the technology is more mature, but can no longer work with diesel, and the engine power loss is relatively large, only about 65% to 70% of the original diesel engine. The second method is that the fuel system of the original diesel engine is not changed. In addition to the same natural gas fuel system as above, the general compression ratio does not need to be changed. After the engine cylinder sucks in the mixture of air and natural gas, a small amount of diesel is injected from the original diesel injector for ignition. After diesel ignition, the combustible mixture of natural gas and air is ignited to work. This is a dual-fuel natural gas engine.
The reporter made an unannounced visit to a natural gas vehicle refitting plant near the Zhongjing filling station in Nanyang, Henan province, and learned that the main refitted model of the refitting plant was a heavy-duty semi-trailer tractor. According to the manager of the plant, the manager of the remodeling plant, he can either replace the entire fuel engine and convert it into a gas engine, or add an air circuit on the basis of the original fuel engine, and convert the original diesel engine into fuel and gas. Both models can use dual-fuel engines. According to him, the first modification program requires the addition of a new gas engine. The cost of the engine is about 60,000 to 70,000 yuan. The overall conversion, plus the cost of the modification of the working hours and a single gas cylinder is about 120,000 yuan. Yuan around. The second modification program only needs to make some changes to the original engine, and it can be operated with natural gas bottles. The price of a single natural gas bottle is around 30,000 yuan. If two natural gas bottles are added, the overall cost is 70,000 yuan. about. When the reporter stated that he used his own truck to pull coal from Pingdingshan, Henan, to Wuhan, the person in charge of the conversion plant stated that the reporter’s truck needed to use two natural gas cylinders. The individual gas cylinders had a cruising range of about 400 km, and two natural gas gases were installed. The bottle can ensure that the vehicle has sufficient air supply to and from Pingdingshan and Wuhan. If the funds are not adequate, the second cylinder can be paid in installments for a period of one year. The reporter continued to ask whether the capital advancement party for this installment payment is the bank or the retrofitting factory. If the retrofitting plant advances the funds, whoever bears the credit for the customer, the person in charge of the retrofitting plant will not support the explicit answer.
Changzhou Yikong Automobile Electronics Co., Ltd. operates a major business is the LNG natural gas modification of heavy-duty diesel vehicles. According to the company’s Mr. Zhuang’s introduction, the company is currently only able to retrofit the diesel engine, increase the gas path, and convert the diesel engine into a dual-fuel engine. The reason why the company did not completely replace the diesel engine with the gas engine business is because the company believes that the dual-fuel engine has more advantages than the gas engine and that it is relatively inexpensive in terms of conversion costs. The dual-fuel engine's market operation mode is also relatively mature. According to the person in charge of the company, compared to pure gas engines or diesel engines, the advantages of dual-fuel engines are mainly reflected in the simpler and more convenient modification, and no need to carry out the transformation of engine core components such as pistons, cylinder liners, and cylinder heads; The fuel engine maintains the characteristics of high compression ratio, compression ignition, and high efficiency of the diesel engine. At the same time, the power, torque and other power indicators are equivalent to that of the diesel engine; when the supply is insufficient, the diesel engine can be flexibly switched to the diesel engine working mode, and the pure gas Compared with the engine, it has higher thermal efficiency and adaptability. The person in charge of the company stated that using dual-fuel engines, the cost per kilometer is about 1 yuan, and heavy trucks that have been using three to four years are most suitable for LNG natural gas conversion, which can save energy costs.
Need to regulate the market order
In view of the safety problems that vehicles may face after natural gas conversion, the reporter learned during the interview that the main problem for CNG-modified vehicles is the safety of CNG cylinders. It is reported that the internal pressure of CNG cylinders is relatively high, usually reaching 20 MPa. If compressed natural gas tanks are defective in terms of compressive strength, or when vehicle operations are facing unexpected situations, it is easy to turn compressed natural gas tanks into a time bomb. . To ensure the safety of CNG modified vehicles, qualified manufacturers must produce gas cylinders and regular inspections should be performed on the cylinders. Compared with CNG cylinders, LNG cylinders store natural gas at a low temperature of minus 162 degrees Celsius. The cylinder pressure is less than 2 MPa. Under low temperature and pressure storage conditions, the cylinder safety factor is higher, but in the event of an emergency LNG leakage may also cause an explosion.
The more important issue facing the “oil to gas†market is the absence and dislocation of government management. According to Mr. Zhuang, the company's “oil to gas†business is currently concentrated in some cities in Shaanxi, Shanghai, Inner Mongolia, Hainan, and Hubei. The reason why these areas are concentrated is because the relevant departments of these places have already liberalized the “oil to gas†market. The reporter stated that his vehicle is a license in Beijing. Mr. Zhuang said that the company does not have an “oil-to-gas†business in Beijing and that if it wants to carry out “oil-to-gas†activities, it can only go to the aforementioned areas and it will Some special handlers. When the reporter asked whether the vehicle could be properly examined in the future, Mr. Zhuang said that the annual review must also pass through some special channels and may have to pay a few hundred yuan more each year.
The “oil-to-gas†business has blossomed, but the relevant government departments in many localities have not issued normative management measures for “oil-to-gas†projects for vehicles. Even if regulations are issued, due to the differences in local policies, the annual review of refitted vehicles will face new challenges. The problem caused the user to be indifferent when performing "oil to gas". Some users simply use some special channels to carry out "oil-to-gas" operations on vehicles, and the safety problems faced by this approach are obvious. The absence and dislocation of government management will not only make it impossible for the potential oil-to-gas market to be released, but will also cause significant safety hazards in the future because of illegal and unregulated “oil-to-gas†projects.
August 05, 2021