Let’s talk about CNG vehicles

Thread Content

1. Overview of CNG vehicles: To reduce pollution, developed countries around the world attach great importance to the development of low-pollution (green) vehicles. In China, the development of such green vehicles has started with vehicle modification technologies, specifically those related to converting gasoline vehicles into vehicles that use compressed natural gas (CNG) as fuel. This technology involves adding a CNG fuel supply system to existing gasoline vehicles, which mainly includes components such as gas cylinders, pressure reducing regulators (or vapor regulators), mixers, and fuel conversion devices. The compressed natural gas in the cylinder is reduced to negative pressure by a pressure reduction device and supplied to the car engine; the conversion between natural gas fuel and gasoline fuel is achieved through a fuel conversion device. Modified dual-fuel vehicles still require gasoline as a starting fuel, with this amount accounting for about 20% of the total fuel used; the remainder is natural gas. 2. Characteristics of CNG vehicles: The difference between CNG vehicles and conventional gasoline vehicles lies in their fuel supply system, which is a specialized device. The fuel supply system is closely related to the performance of CNG vehicles, while the method of storing natural gas at high pressure in these vehicles (CNG, or natural gas, is stored at 20–25 MPa) is the most important factor affecting the safety of CNG vehicles. Using compressed natural gas as vehicle fuel is a mature technology; vehicles powered by natural gas perform better than those using conventional gasoline or similar fuels. Thanks to the high octane rating of natural gas (130), the compression ratio of engines can be increased to 12:1. Therefore, under normal circumstances, natural gas vehicles have better performance than LPG vehicles. Car engines that run on natural gas have a long lifespan and low maintenance costs. Because compressed natural gas burns cleanly, produces less pollution, and results in less wear on parts. However, the weight of the gas cylinder for compressing natural gas is generally 6 times that of a gasoline tank, increasing the vehicle’s overall weight. When cars run on natural gas, hydrocarbons produced are reduced by 50% to 80% compared to when using gasoline, and nitrogen oxide emissions are also lower than those with gasoline. 3. Advantages of CNG vehicles: 1. Reduction in vehicle exhaust pollution. 60% of air pollutants come from vehicle exhaust; by using natural gas as fuel, hydroxides in vehicle exhaust can be reduced by 72%, carbon monoxide by 97%, nitrogen oxides by 39%, carbon dioxide by 24%, and sulfur dioxide by 90%. Noise levels are also reduced by 40%, and these vehicles contain no benzene or lead. Taking the natural gas vehicles developed in Shanghai, China, as an example, their use eliminates lead emissions; carbon monoxide emissions are reduced by 60%, and hydrocarbon emissions are cut by 90%. 2. Energy savings bring significant economic benefits. When a medium-sized vehicle switches from using gasoline to natural gas, it consumes 16.3 cubic meters of gas per 100 kilometers, which is equivalent to 16 kilograms of gasoline. At the local prices of 1.4 yuan per cubic meter for CNG and 6.0 yuan per cubic meter for gasoline, if a vehicle travels 70,000 kilometers per year, it can save approximately 9 tons of fuel over that period, resulting in cost savings of 56,602 yuan. 3. The vehicle has better power performance and an extended engine lifespan. “Green fuel” has a higher calorific value than gasoline; it burns in the engine cylinders in gaseous form, mixing with air. This allows for a more complete, uniform, and stable combustion compared to gasoline, which mixes with air in a misty form. As a result, it not only improves the engine’s thermal efficiency and the vehicle’s power performance, but it also causes less damage to the engine cylinder walls. It does not dilute the engine lubricant, thereby extending the interval between oil changes. 4. Safe for storage and transportation, and easy to use. Since \"green fuel\" is a lightweight gas with a high ignition point, its danger level is much lower than that of gasoline at normal temperatures. Therefore, the technical equipment required for storage, canning, transportation, and use is relatively simple. If a car catches fire in an accident, the gas cylinder heats up and the internal pressure increases; at that point, the pressure release valve will release gas in a controlled manner to allow it to burn. Since this release process helps lower the temperature of the gas cylinder, an explosion does not occur. 4. CNG vehicle conversion: The cost for converting a vehicle ranges from 4,500 to 8,000 yuan per vehicle, and the conversion can be completed within 4 hours. The investment in conversion can be recovered within 1 to 2 years, depending on the distance traveled. This post was last edited by johncom on 2009-4-10 17:07]