采用常规直列式喷油泵的直喷式柴油机通常配有一个回路式低压燃油系统。低压系统中的燃油流量通常是当时燃油消耗量的若干倍,甚至在发动机全负荷的情况下也如此。燃油过量供应的目的是适当地冷却喷油泵以及冲走喷油泵柱塞在喷射结束阶段产生的各种气态成分。基于低能耗要求和现代化发动机监视系统的需要,对当前燃油消耗率进行在线测量愈来愈重要。然而,由于低压燃油系统的回路式特点,这项任务很艰巨。当前燃油流量不得不以喷油泵进油管和回油管中两个同时发生的燃油流量测值的差值形式来确定。通过对这一差值测量误差传播的详细分析,会发现供油流量与消耗流量之比对测量有显著影响。为了获得满意的测量精度,供油管和回油管的单独测量必须达到非常高的要求。本文将提出一种能够满足这些要求的容积式流量计的方案。除此之外,为控制这种差值测量的棘手的误差传播,还必须考虑更多的参量。一个重要的影响因素是由于喷油泵的损失导致的燃油温度升高。温度的不同会伴随着供油管和回油管中燃油密度的变化。本文将详细说明密度差造成的影响,并给出补偿方法。除此之外,在低压燃油系统中,喷油泵柱塞的运动会产生一种特殊方式的压力波动。这些压力型式包括高压峰值和真空,这些现象可以通过喷油泵柱塞一个工作循环的描述加以解释。因此,需要针对这些压力型式寻找一些方法,在负压时测出逆流,在出现高压峰值时避免机械过载。本文将会提出一个方法,用来控制压力波动引发的这些后果。最后,本文将介绍在实际应用中得出的各种测试结果。本文的油耗测量系统的读数与精确测量(大量间断性测定或油箱容量的长期测定)数据对比说明,只要适当考虑低压燃油系统的特殊条件,精确的实时燃油消耗测量是可行的。 Direct injection diesel engines with conventional in-line injection pumps are usually equipped with a loop low pressure fuel system. Fuel flow in low-pressure systems is usually several times the current fuel consumption, even at full engine load. The purpose of overfull fuel supply is to properly cool the fuel injection pump and to flush away the various gaseous components produced by the fuel injection plunger at the end of the injection. Based on the demand of low energy consumption and the demand of modern engine monitoring system, it is more and more important to measure the current fuel consumption rate on-line. However, this task is arduous due to the looping nature of the low-pressure fuel system. The current fuel flow has to be determined as the difference between two simultaneous fuel flow measurements in the fuel injection pipe and the return pipe. A detailed analysis of the spread of this difference measurement error shows that the ratio of fuel flow to consumption flow has a significant effect on the measurement. In order to obtain satisfactory measurement accuracy, the separate measurement of the supply and return lines must meet very high requirements. This article presents a solution to a volumetric flowmeter that meets these requirements. In addition, more parameters must be considered in order to control the tricky error propagation of this difference measurement. An important factor is the increase in fuel temperature due to fuel pump losses. The difference in temperature is accompanied by changes in the fuel density in the supply and return lines. This article will detail the impact of density differences, and give compensation methods. In addition, in low-pressure fuel systems, the movement of the fuel injection pump plunger creates a special mode of pressure fluctuations. These pressure patterns include high pressure peaks and vacuum, which can be explained by a duty cycle of the fuel injection pump plunger. Therefore, there is a need to find ways to address these pressure patterns to detect counter-flow at negative pressure and to avoid mechanical overload in the event of high pressure peaks. This article will propose a way to control these consequences of stress fluctuations. Finally, this article will introduce the various test results obtained in practical applications. A comparison of the readings of the fuel consumption measurement system of this paper with those of an accurate measurement (a large number of intermittent measurements or long-term determination of tank capacity) shows that accurate real-time fuel consumption measurements are feasible as long as proper consideration is given to the specific conditions of a low pressure fuel system.