CNG公交客车燃料消耗量计算方法

Calculation method of fuel consumption on CNG bus

分析了CNG公交客车的燃料消耗量测试参数,确定了流量计的安装位置;基于安装位置的固定气压范围,考虑到驾驶节能技术水平与乘坐人数的影响,提出了CNG质量流量的计算方法;通过场地测试,验证了CNG质量流量与燃料温度、燃料压力之间的非线性关系,以及与环境温度、气瓶出口端压力的关系;通过运营测试,分析了CNG质量流量修正前后的差异,并验证了测试方案的可行性。研究结果表明:受测试气压的限制,流量计唯一的串接位置是减压阀的出口端与低压燃气滤清器之间,CNG经过减压阀后的出口压力基本稳定在0.80~0.95 MPa之间;在运营测试结果修正中,驾驶节能技术的影响最大,最大偏差可达4%,受测公交线路的驾驶节能技术水平有87.6%的相对值介于0.9~1.1,离散度较低;当环境温度升速为4.0~4.3℃·h^(-1)时,燃料温度的变化速度基本波动于±0.61℃·h^(-1)之间,证明了燃料温度对环境温度的变化不敏感;气瓶出口端压力与燃料压力没有必然联系,其数值的减小不会影响CNG质量流量的变化;在0.80~0.95 MPa的燃料压力下,测试位置的CNG当量密度基本稳定在6.1kg·m^(-3),连续测试30km后,CNG质量流量计算值与实测值误差小于5%;经对CNG质量流量修正后,3辆测试车CNG质量流量的变化幅度分别为1.88%、-4.04%和1.71%,因此,采用CNG质量流量计算CNG消耗量更为精确。

The test parameters of fuel consumption of CNG bus were analyzed, and the suitable installation location of CNG flowmeter was determinated. Based on a fixed pressure range of CNG at installation location, the influence of driving energy saving technology level and passenger number was considered, and a calculation method of CNG mass flow was put forward. Field test was carried out to verify the nonlinear relationship among the mass flow, temperature and pressure of CNG, in addition, the relationship among the mass flow, the ambient temperature and the outlet pressure of cylinder. Based on the operational test, the difference of CNG mass flows before and after correction was analyzed, and the feasibility of testing method was verified. Research result shows that because of the limit of tested CNG pressure, the unique position ofCNG flowmeter is fixed between the outlet of pressure reducing valve and hypobaric gas filter, and CNG pressure decompresses to 0.80-0.95 MPa by pressure reducing valve. In the process of modifying operation test result, the driving energy saving technology level has greatest impact on the final test result of CNG mass flow, and the maximum tolerance may reach 4 %. 87.6 % of the relative values for the driving factor are between 0.9 and 1. 1, which reflects lower dispersion. When the rising speed of ambient temperature is between 4. 0 ℃ · h-1 and 4. 3 ℃ · h-1, the variance ratio of CNG temperature ranges from --0.61 ℃ · h-1 to 0.61 ℃ ·h-1 , which verifies that the CNG temperature is insensitive to the ambient temperature. Precisely speaking, there is no necessary connection between CNG pressure and cylinder outlet pressure, and the decrease of cylinder outlet pressure does not interfere with CNG mass flow. Under the CNG pressure of 0.80-0.95 MPa, the CNG equivalent density at the testing position is stable at 6. 1 kg ·m a. After continuous testing about 30 km, the deviations are less than 5 % between the test result and computation result of CNG mass flow. After modifying CNG mass flow, the variations of CNG mass flows of 3 buses are 1.88%, -4.04% and 1.71%, respectively, so CNG mass flow can be used to accurately compute CNG consumption. 5 tabs, 10 figs, 26 refs.