**一、中文论述题** **1. 讨论汽车新能源五大素质及分析方法** 汽车新能源的五大素质主要包括：技术成熟度、经济可行性、环境友好性、资源可持续性和社会接受度。以下是对这五大素质的分析方法： * **技术成熟度**：评估新能源技术的研发阶段、稳定性和可靠性。方法包括查阅相关技术研究报告、市场调研和行业报告，同时对比现有技术水平及未来发展趋势。 * **经济可行性**：分析新能源技术的成本效益，包括初始投资、运营成本、维护成本等。可采用成本效益分析、财务可行性研究和投资回报分析等工具进行评估。 * **环境友好性**：评估新能源技术对环境的影响，包括排放减少、能源消耗和生态效应等。方法包括环境影响评价、生命周期分析和碳排放计算等。 * **资源可持续性**：考察新能源技术的资源供应情况和长期可持续性。需要分析资源储量、开采效率和可再生性等因素。 * **社会接受度**：了解公众对新能源技术的接受程度，包括政策环境、市场需求和公众认知等。可通过市场调研、问卷调查和社交媒体分析等方式获取相关信息。 **2. 论述天然气汽油两用燃料发动机燃用天然气时动力性下降的原因** 天然气汽油两用燃料发动机在燃用天然气时动力性下降的原因主要有以下几点： * **热值差异**：天然气的热值低于汽油，因此在相同体积下，天然气提供的能量较少，导致发动机输出功率下降。 * **混合气浓度**：天然气与空气的混合比例需要精确控制，如果混合气浓度不合适，会影响燃烧效率，从而降低动力性。 * **点火系统**：天然气的燃点较高，需要更高的点火能量才能可靠点火。如果点火系统不能满足要求，可能导致燃烧不完全，影响动力性能。 * **燃烧效率**：天然气的燃烧速度较汽油慢，因此需要调整发动机参数以适应其燃烧特性。如果调整不当，会影响燃烧效率，导致动力性下降。 **二、英文论述题** **1. Discuss the reasons why the safety of natural gas vehicles is higher than gasoline vehicles.** The safety of natural gas vehicles (NGVs) is higher than gasoline vehicles due to several key factors. Firstly, the ignition temperature of natural gas is significantly higher, at over 650°C compared to approximately 427°C for gasoline. This higher ignition point reduces the likelihood of spontaneous combustion in case of an accident. Secondly, the flammability range of natural gas in air is narrower, between 5% and 15%, compared to 1% to 7% for gasoline. This reduced flammability range reduces the potential for fire or explosion under normal circumstances. Furthermore, natural gas, being lighter than air, quickly disperses into the atmosphere, making it difficult to accumulate in dangerous concentrations. Additionally, the storage tanks of NGVs are designed to withstand high pressures and are rigorously tested to ensure safety. These factors contribute to the overall higher safety of NGVs compared to gasoline vehicles. **2. Discuss the names and working principles of three powertrain types in natural gas vehicles in English.** Natural gas vehicles (NGVs) typically employ three main powertrain types: Compressed Natural Gas (CNG), Liquefied Natural Gas (LNG), and Bi-fuel systems. * **Compressed Natural Gas (CNG)**: In a CNG vehicle, natural gas is compressed and stored in high-pressure tanks mounted on the vehicle. When the engine requires fuel, the compressed gas is released through a regulator to reduce its pressure and then fed into the engine's fuel system. The engine is modified to burn natural gas efficiently, producing power for the vehicle. * **Liquefied Natural Gas (LNG)**: LNG vehicles utilize liquid natural gas, which is obtained by cooling and compressing natural gas to extremely low temperatures (-162°C). The liquefied gas is stored in cryogenic tanks on the vehicle. Before entering the engine, the LNG is warmed and converted back to a gaseous state. The engine is then supplied with the natural gas, which is burned to produce power. * **Bi-fuel Systems**: Bi-fuel systems allow the vehicle to operate on either gasoline or natural gas. These systems incorporate separate fuel tanks for each type of fuel and modify the engine to operate on both fuels. Depending on the vehicle's configuration, the driver can switch between fuels manually or automatically based on factors such as fuel availability and cost. The engine is designed to optimize combustion efficiency for both fuels, providing the flexibility to operate on either gasoline or natural gas while maintaining optimal power and performance.
