Common Rail Pump Research Articles

Coupled evolution process of lubrication and wear in piston-liner interface of high-pressure common rail pumps

As a pivotal frictional pair of piston pumps, the piston-liner interface is vulnerable to rapid wear in the face of severe environment, triggering a consequent contraction in the piston pump's service longevity. Based on statistical theory, a transient mixed lubrication model has been established in this work, which takes the surface roughness effect, thermal-elastic deformation, as well as the piston micro-movements into account. In conjunction with the wear calculation model, we propose a novel lubrication-wear coupling strategy for the piston-liner interface, enabling a nuanced exploration of the transient interdependency link between lubrication efficiency and wear characteristics. To underscore the robustness of our proposed model, a comparison is drawn with experimental results gleaned from established literature. This investigation not only provides insights into the progression of wear depth and lubrication efficiency throughout a given time frame. but also assesses the impact of varying operational parameters on wear depth Parametric studies reveal that the wear region predominantly occurs at the inlet and outlet positions of the liner. Furthermore, both working pressure and cam rotational speed significantly influence the interface's lubrication characteristics and wear behavior. Consequently, in piston systems operating under high-pressure and high-speed conditions, it is imperative to closely monitor wear patterns and consider the impact of thermal effects.

Experimental study on the transient supply consistency for a common rail pump based on impedance theory

Common rail (CR) fuel pumps are characterized by pulsating supply, and instantaneous flow ripple is the main reason for the variation in supply consistency. To analyze the transient supply consistency of CR pump, a test bench for transient supply performance was originally designed and established. The potential effects exerted by pump speed and operating pressure on the pressure ripple were obtained under different fuel metering valve (FMV) openings. On this basis, an approach for the calculation of instantaneous flow ripple was proposed by combining impedance theory and hydraulic transmission line method (TLM). Furthermore, the coefficient of variation (CoV) of flow ripple amplitude was applied to evaluate the cycle-to-cycle consistency in fuel supply process. The results show that the rotational speed together with the plunger number determines the frequency of flow ripple. The pump presents a greater flow ripple amplitude under high speed and low pressure conditions, which further leads to an intense pressure ripple. Besides, in most operating points, the CoV is around 0.15, indicating a good transient supply consistency. When the FMV is partially open, under the coupled effect of FMV operating frequency and plunger movements, the value of CoV shows an oscillating trend as a function of speed.

Analysis of Ball Check Valves with Conical and Spherical Seat Designs from Common-Rail Pumps

Common-rail fuel injection systems are still a good option for equipping new car models. The technology is well known, systems of this type are reliable and can be used on a wide variety of diesel and petrol engines. However, there is still room for improvement. The ball check valve, which is part of the common-rail pump, is designed to open and allow the compressed fluid to be sent to the high-pressure accumulator and close to not allow fuel to return to the compression chamber. The valves’ design directly influences the volumetric efficiency of the outlet flow and the robustness against high pressures that lead to low performance and short service life of the fuel injection systems. This paper aims to compare two ball check valves with conical and spherical seat designs. The analysis is based on theoretical calculations and CFD simulations, which will give more confidence in the results. Considering the comparative analysis results, the ball check valve with a spherical seat shows better flow dynamics than the ball check valve with a conical seat. In addition to the improved flow dynamics, the ball check valve with spherical seat seems to have a uniformly distributed fluid pressure inside the valve. In contrast, the conical seat ball check valve has high local fluid pressures, leading to fatigue.

Wear’s issues on high-pressure common rail pumps

High-pressure pumps are the most important components of modern fuel injection systems. A modern system is the common rail one, equipping vehicles with a diesel or a gasoline engine. Depending on the fuel type, the design of the pumps is completely different, and it is more complex for diesel engines that are more prone to wear. The components subjected to wear are those in contact and continuous motion like drive shaft with roller and shoe, plunger and hydraulic head assembly with valves. Wear is initiated as a result of a process and product deviations or inadequate exploitation of the high-pressure pump. The factors influencing the wear can be improper material hardness, improper coating, incomplete or wrong machining, wrong clearance or misalignment between components, inadequate surface finish, dimensions out of tolerances, wrong assembly process, poor lubrication, contamination or running at high loads and temperatures. Our paper aims to identify, describe and discuss the types of wear encountered at common rail high-pressure pumps, highlighting the effects on their functionality. The wear occurrence can be prevented by paying more attention to the design details, manufacturing processes and correct exploitation of the high-pressure pumps.

Analysis of the applicability of a common rail pump for an aircraft engine

The paper presents an analysis of the possibility of using a common rail pump to supply an aircraft compression-ignition engine. It is an engine with a two-stroke cycle, three cylinders, opposing pistons and 100 kW power. Its each combustion chamber is supply by one or two injectors controlled by electromagnetic valves. In order to assess the possibility of using a common rail pump, four high-pressure pumps were tested on a bench. They are piston pumps differing in the number and geometry of their pumping sections. The analysis included the pumping output, the torque on the pump drive shaft and the power needed to drive the pump. The weight and overall dimensions of the pump were also considered, including the arrangement of the pumping sections and the way the drive is transmitted. The research allowed to optimize the engine power supply system depending on fuel demand and the way the pump is mounted on the engine.

Analysis of the noise emissions of a common-rail pump before and after an endurance test

One of the problems of the modern era that we are facing nowadays, besides the pollution caused by fuel burning, is the level of noise pollution in constant growth in agglomerated cities. The main source of noise is the transport sector where the number of passenger cars had dramatically increased in recent years. Most of the vehicles around the world are powered by internal combustion engines equipped with a fuel injection system and a small percentage with an electric one. Researchers have shown that noise pollution affects human health from a psychological and physical point of view. Due to the manufacturing process of high-pressure pumps, some pumps mounted on the engine and running under certain conditions can produce a higher audible noise than the engine. The paper presents an experimental investigation on a high-pressure pump that provides a comparison between the noise level at the beginning of its lifetime and that resulting after an endurance test performed on a special test bench. It has been found that the greatest contributor to noise emissions is the high-pressure pump outlet valve when it opens. To improve the sound quality of the high-pressure pump, it is essential to further develop the outlet valve design and better control over the manufacturing process.

Numerical Analysis of a Fuel Pump for an Aircraft Diesel Engine

The paper reports on the process of modelling a high-pressure common rail pump designed to supply a two-stroke compression-ignition engine, which includes the presentation of methodology for model construction and results of simulation tests. A one-dimensional model of the pump was developed in the AVL Hydsim environment. A single-section positive displacement pump driven by a double cam was used for modelling. The developed model enables simulation of pump operation in various conditions defined by shaft speed, pumping pressure, settings of pump executive elements as well as fuel properties. The obtained results were compared with the results of bench tests and theoretical calculations. The analysis included the flow rate fuel overflow and changes in pumping pressure depending on the fuel dispenser settings. The model will also be used to build a complete fuel supply system model consisting of an injector model, a rail model and a control system model. The research is carried out with a view to optimising individual components and the operation of the entire supply system, taking into account the regulation of pumping pressure and synchronisation of the pumping process with fuel injection cycles.

Influence of ball-seat contact on the noise emissions from common-rail pump outlet valve opening

Nowadays, most engines which equip agricultural machines, ships and cars are diesel ones with a common-rail high-pressure direct injection system. They are providing the advantages of fuel economy, low emission level, and reduced noise in comparison to conventional direct or indirect injection systems. The heart and the most stressed part of the common-rail system is the high-pressure fuel pump which is driven by the engine camshaft, and its role key is to compress the fuel at pressures over 2000 bar. The high-pressure fuel is delivered from pump to the engine combustion chamber via high rail pipes, high-pressure accumulator (rail) and injectors. Compressing the fuel and sending it towards high-pressure accumulator (rail), in some specific cases the pump generates an audible disturbing noise that gets louder than the engine combustion noise. The paper first offers an overview of our experiments performed on common-rail high-pressure fuel pumps in order to find the noise contributor and to develop measures to reduce the disturbing noise. The experimental investigations have proved that the noise occurs when the fuel is compressed and the outlet valve is opening. Then, our experimental study focuses on outlet valve behaviour from design and noise emissions point of view at idle engine speed.

Instantaneous torque, energy saving and flow rate ripple analysis of a common rail pump equipped with different delivery-pressure control systems

A mechanical model of a high-pressure pump of a common rail fuel injection system is presented and validated by comparison with experimental instantaneous pump shaft torque and pump piston lift data. The instantaneous torque has been measured with a high-performance torque meter installed on a hydraulic rig for testing pieces of injection apparatus. In the model, the mechanics of the piston plunger and the forces exchanged between pistons and cam are simulated, and friction losses between mobile parts are taken into account. The numerical tool is used to investigate the dynamical performance of the high-pressure pump and to analyse the impact of the rail pressure control strategy on instantaneous torque, energy saving and flow rate ripple. The rail pressure control strategy, based on the application of a fuel metering valve at the pump inlet, gives rise to an improved hydraulic efficiency of the injection system at part loads and to a moderate rate of pressure increase in the pumping chamber at part loads. However, the rail pressure control strategy based on the installation of a pressure control valve at one rail extremity leads to a reduction in the pump flow rate ripple and to a diminution in the fatigue stress. Furthermore, cavitation problems can occur during intake and early compression phases of the pump cycle when the fuel metering unit is working.

The development of a data acquisition system for measuring the injection rate of a multihole diesel injector

In this research, two types of sensors systems (an ‘amplifier integrated sensor with a fixed measuring range’ and an ‘amplifier-sensor setup with adjustable measuring range’) are analyzed and compared with each other. From experimental results obtained simultaneously from the nozzle holes, the two sensors reliability and robustness were analyzed with regards to injection rate and cycle fuel injection quantity. Afterwards, series of different experiments were conducted using an eight holed nozzle to determine the limits or the degree of freedom within which experimental results could be deemed reliable. From the analysis, and with reference to conventional standards, the new sensor (amplifier-sensor setup with adjustable measuring range) performed better with relatively wider application limits. Also the new sensor-system setup measurement accuracy, was studied experimentally with the aid of a common-rail pump test bench, where the influence of sensor target distance and sensor target-axis angles on the measured result were determined. Sensor target distance of not more than 15mm and sensor target-axis angle within 90°±5° (85°–95°) range were the optimum settings determine to ensure reliable measurements. Validation of cycle fuel injection quantities from each nozzle hole of the eight hole nozzle was performed with the aid of an EFS injection flow meter. This research presents insight into the effective data acquisition from multihole injectors, which is essential due to the increasing popularity of multihole injectors used in internal combustion (IC) engine nowadays.

Common Rail Pumps and Injectors for Large Diesel and Dual-fuel Two-stroke Engines

Common Rail Pumps and Injectors for Large Diesel and Dual-fuel Two-stroke Engines

A Case Study on Scrap Reduction of Transfer Pump in Common Rail Fuel Pump

The aim of the paper is to reduce the Scrap in Transfer Pump Tightening Assembly in Common rail Pump. Low Torque rejection phenomenon was considered as it was of more rejection in past 6 months and it was having average per month scrap cost to be excessive. The objective of the work was to reduce the scrap quantity of TPC Tightening Assembly phenomenon from 3% of total scrap quantity of CR – Pump assembly to an accepted level. Due to this more rejection quantity, Loss of production and quality, High scrap cost and utilization of more man power were noticed in CR-Pump Assembly. To solve these problems seven problem Solving tools were attempted. To reduce the scrap cost and increase productivity and quality were targets with good usage of man power.

Diesel Lubricity Requirements of Future Fuel Injection Equipment

This paper looks at the underlying fundamentals of diesel fuel system lubrication for the highly-loaded contacts found in fuel injection equipment like highpressure pumps. These types of contacts are already occurring in modern systems and their severity is likely to increase in future applications due to the requirement for increased fuel pressure. The aim of the work was to characterise the tribological behavior of these contacts when lubricated with diesel fuel and diesel fuel treated with lubricity additives and model nitrogen and sulphur compounds of different chemical composition. It is essential to understand the role of diesel fuel and of lubricity additives to ensure that future, more severely-loaded systems, will be free of any wear problem in the field. The lubricity with the High-Frequency Reciprocating Rig (HFRR) and the critical load of incipient scuffing (loadcarrying capacity) in the High-Temperature Oscillating Machine (HiTOM) using real components of a Common Rail (CR) pump as test samples depends on the composition of the base fuels. A content of 5 % rapeseed-methyl ester (RME) in fuel increases the loadcarrying capacity and increases the lubricity. Hydrodesulphurization decreases the lubricity of gas oil by 80 - 200 μm and the load-carrying capacity by 1500 N. Model sulphur compounds benzothiophene, dibenzothiophene and 4,6-dimethyldibenzothiophene cannot restore the lubricity of a hydrotreated diesel fuel, but can increase the load-carrying capacity. The model nitrogen compound 8-hydroxyquinoline improves the lubricity at very low concentrations (20 ppm nitrogen) whereas quinoline and acridine need a higher concentration (100 ppm nitrogen) for some lubricity improvement. The outcome of this work has confirmed that specific lubricity additive chemistries can stretch the mixed lubrication area where highly-loaded contacts can operate safely. Specific lubricity additives with carboxylic acid-, ester- and amide based chemistries can increase the lubricity in a variety of base fuels at a concentration of 200 ppm to meet the lubricity requirement according to EN 590. These compounds can provide protection against adhesive wear by increasing the incipient scuffing load. Higher than market-typical additive concentrations can further increase lubricity, but are levelling at concentrations between 1000 ppm and 2000 ppm. The ester-based additives level at a lower value than the acid and amide based additives and so can provide further protection to FIEs. The load-carrying capacity of test fuel - ULSD 1 - can be increased by 4500 N by an ester content of 1000 ppm. The acid can only provide an increase of 2500 N. The ester-based additive at 200 ppm can already provide an improvement of the load-carrying capacity by 3000 N at a fuel temperature of 90 °C. Tribological investigations with the HiTOM showed an excellent correlation between the results of this test and the HFRR results.