Large Flow Rate Research Articles

CFD and Energy Loss Model Analysis of High-Speed Centrifugal Pump with Low Specific Speed

High-speed centrifugal pumps with low specific speed have the characteristics of a small flowrate, a high head, and being compact and light weight, making them promising candidates for applications in the thermal management of aerospace and electronic devices. The energy loss in the low specific speed pump is critical and complex due to the large impeller diameter, the narrow and long flow channel, and the small outlet width. In this paper, an analysis method based on an energy loss model and computational fluid dynamics simulations (ELM/CFD) is proposed to analyze the performance of the low specific speed pump with a fully sealed structure. Experiments were carried out under variable water flowrates. The results show that the empirical correlation method failed to accurately predict the performance of high-speed centrifugal pumps, because the bearing clearance leakage and motor channel leakage are ignored. Moreover, the volume loss and hydraulic loss are calculated based on the empirical parameters of commonly used pumps that are different from the high-speed pump with the low specific speed in the complex flow channel structure. The ELM/CFD method calculates various loss power based on the simulation results and can predict the head and efficiency with deviations less than 2% and 5%, respectively. ELM/CFD can accurately analyze the optimization direction of the pump. The hydraulic loss and the volume loss of the impeller are the dominant factors that restrict the pump efficiency under the lower flowrates, while the hydraulic loss of subsequent flow channels becomes important under the larger flowrates.

Control of distillation columns with dual steam and hot-oil reboilers

Many distillation columns achieve process intensification by utilizing hot streams from other units in the plant to substitute for some of the utility-supplied steam used in the reboiler. This thermal coupling requires adequate differential temperature driving forces so that heat-exchanger area is not excessive. It also requires that the units are reasonably close together so that piping cost and pressure drops are not too large. There are two reboilers at the base of the column that operate in parallel with the two independent heat sources providing vapor boilup. If the external hot stream is vapor that is condensed in the one reboiler, the heat transferred is latent heat. If the external hot stream is hot liquid, the heat transferred is sensible heat, which requires much larger flowrates. Since pumping liquid is relatively inexpensive, larger flowrates and larger pressure drops are less important than in vapor streams.This paper explores the dynamic control of dual-reboiler distillation columns in which a hot liquid stream from another unit is fed to one reboiler and steam is fed as needed to the other reboiler. The key simulation implementation issue is how to dynamically model the heat transfer in the hot-oil reboiler since it is governed by log-mean differential temperature driving forces. Several alternative control structures are evaluated.

Influence of Tubular Turbine Runaway for Back Pressure Power Generation on the Stability of Circulating Cooling Water System

With the increasing maturity of tubular turbine power generation technology, an increasing number of industrial applications use it to recover the rich back pressure energy of a circulating cooling water system (CCWS). However, the influence of tubular turbine runaway on the stability of CCWS is still unclear. This work combines the one-dimensional (1D) method of characteristics (MOC) with the three-dimensional (3D) computational fluid dynamics (CFD), develops a 1D CCWS and 3D tubular turbine coupling simulation method, and simulates the runaway and runaway shutdown processes of tubular turbine under small flow rate condition and large flow rate condition in the real system. Results show that the main operating parameters of the system slightly change when the tubular turbine transitions from the steady state to the runaway condition. The runner’s radial force substantially increases in the runaway condition of the tubular turbine, and the phenomenon of violent oscillation is observed compared with the steady state. During the shutdown process of the tubular turbine runaway condition, the valves in parallel and series with the faulty turbine adopt a reasonable cooperative control strategy, which allows for a smooth recovery of the system operating pressure to the original steady state conditions.

Simulation of turbulent flow over roughness strips

Heterogeneous roughness in the form of streamwise aligned strips is known to generate large scale secondary motions under turbulent flow conditions that can induce the intriguing feature of larger flow rates above rough than smooth surface parts. The hydrodynamical definition of a surface roughness includes a large scale separation between the roughness height and the boundary layer thickness which is directly related to the fact that the drag of a laminar flow is not altered by the presence of roughness. Existing simplified approaches for direct numerical simulation of roughness strips do not fulfil this requirement of an unmodified laminar base flow compared with a smooth wall reference. It is shown that disturbances induced in a modified laminar base flow can trigger large-scale motions with resemblance to turbulent secondary flow. We propose a simple roughness model that allows us to capture the particular features of turbulent secondary flow without impacting the laminar base flow. The roughness model is based on the prescription of a spanwise slip length, a quantity that can directly be translated into the Hama roughness function for a homogeneous rough surface. The heterogeneous application of the slip-length boundary condition results in very good agreement with existing experimental data in terms of the secondary flow topology. In addition, the proposed modelling approach allows us to quantitatively evaluate the drag increasing contribution of the secondary flow. Both the secondary flow itself and the related drag increase reveal a very small dependence on the gradient of the transition between rough and smooth surface parts only. Interestingly, the observed drag increase due to secondary flows above the modelled roughness is significantly smaller than the one previously reported for roughness resolving simulations. We hypothesise that this difference arises from the fact that roughness resolving simulations cannot truly fulfil the requirement of large scale separation.

Analysis and experimental investigation on the flow rate controller for PWR accumulator

During the large break loss coolant accident (LBLOCA), the emergency safety injection system is used to inject the safety water into the reactor pressure vessel (RPV) via the primary circuit or direct vessel injection (DVI) to avoid any uncovering of the core. The accumulator (ACC) is an important device to act as a water supplier during the safety injection. A flow rate controller (FRC) was designed to provide the large-flow-rate injection to reflood core quickly at the beginning of the injection and then turn to the small-flow-rate injection later. It makes the safety injection longer than those normal ACCs with large flow rate only and improve the efficiency of the safety injection. A FRC concept was evaluated with computational fluid dynamics (CFD) software in the paper. The fluid flow pattern of the fast mode and slow mode were investigated to reveal the mechanism of the FRC operation. To perform the experiment on a small test section, a scaling analysis was done to find the criteria between the model and the prototype. Then a test facility was established to simulate the operation condition of the FRC based on the scaling results. A test section was tested in transient condition with 1/4 diameter and equal height of the prototype. The results show the flow rate ratio was 3.57:1 at the critical point of the flow rate. The paper also presents the thermal hydraulic parameters such as pressure, injection rate, liquid level, temperature of the gas and water in transient during the injection. The flow resistance coefficients of the two modes were obtained in the experiment too.

Numerical investigation on indicated power and discharge process of three different discharge methods of swing compressor

Pressure variation during the discharge process is important to the discharge flow loss and indicated power of swing compressor. Due to the small effective discharge area and the large discharge volume flow rate at the beginning of discharge process, pressure shoots up to a high value, which is 25%-35% higher than the nominal discharge pressure. Using a suitable discharge method is beneficial to reduce the maximum pressure and indicated power. This paper presents a numerical model to study the indicated power and pressure variation of three different discharge methods. The power consumption per revolution has been discussed to analyze the discharge flow loss. And the effects of over-compression, under-compression and operation speed have been analyzed. Simulation results show that the errors of indicated power are within 3% and the errors of mass flow rates are within 2%, which proves that the accuracy of the presented model is good enough. Furthermore, the major reason affecting the discharge flow loss is the effective discharge area rather than over-compression or under-compression. And compared with the discharge port with valve, the discharge port without valve has a larger effective discharge area. Adding discharge port without valve in swing compressor can reduce the indicated power.

Study on Setting Elevation of Double-Suction Centrifugal Pump Based on Cavitation Characteristics

Setting elevation is an important factor affecting the safe operation of pumps, and the empirical calculation method in engineering cannot fully reflect the cavitation characteristics. In this paper, numerical simulation of cavitation in double-suction centrifugal pump with clearances is carried out. The cavitation characteristics under different flow rates was analyzed based on the setting elevation from the empirical method. It was found that there was cavitation inception under both large flow rate and small flow rate. The cavitation characteristics of the pump with different net positive suction head available (NPSHa) is analyzed. It is found that there is no obvious change in the pump characteristics from cavitation inception to critical cavitation, but after the point of the critical cavitation is reached, a large number of cavities plug the blade passage, and the efficiency decreases rapidly. The results show that in engineer although critical net positive suction head (NPSHc) is considered and the safety margin is increased, it is difficult to ensure that there is no cavitation inception happened in the pump. The cavitation characteristics analyzed by numerical simulation in this paper can provide guidance for the selection of suitable setting elevation.

Optical diagnosis of a kHz-driven helium atmospheric pressure plasma jet

This paper focuses on utilizing several different optical diagnostics to experimentally characterize a pure helium atmospheric pressure plasma jet. Axial electric field measurements were carried out along the plasma plume through the use of a non-perturbing method based on polarization-dependent Stark spectroscopy of the helium $492.2$ nm line. The electric field is shown to increase with distance along the plume length, reaching values as high as $24.5$ kV cm $^{-1}$ . The rate of increase of the electric field is dependent on the helium gas flow rate, with lower gas flows rising quicker with distance in comparison with larger flow rates, with the typical values remaining within the same range. This sensitivity is linked to gas mixing between the helium and surrounding ambient air. Schlieren imaging of the gas flow is included to support this. The addition of a target is shown to further increase the measured electric field in close range to the target, with the magnitude of this increase being strongly dependent on the distance between the tube exit and target. The relative increase in the electric field is shown to be on average greater for a conducting target of water in comparison with plastic. A minimal equipment optical configuration, which is here referred to as fast two-dimensional monochromatic imaging, is introduced as an approach for estimating excited state densities within the plasma. Densities of the upper helium states for transitions, $1s3s$ $^{3}S_{1}$ $\rightarrow$ $1s2p$ $^{3}P^{0}_{0,1,2}$ at $706.5$ nm and $1s3s$ $^{1}S_{0}$ $\rightarrow$ $1s2p$ $^{1}P^{0}_{1}$ at $728.1$ nm, were estimated using this approach and found to be of the order of $10^{10}$ – $10^{11}$ cm $^{-3}$ .

Performance improvement of air-source heat pump heating system with variable water temperature difference

Heating electrification is a trend for the current carbon neutrality setting. The air-source heat pump (ASHP) has been widely used in residential or commercial buildings to replace household coal-burning stoves due to its higher operating efficiency. Previous studies mainly focused on the heat pump equipment, ignoring the whole system performance in practical application. Among the auxiliary system of the ASHP heating system, the power consumption of water pump cannot be ignored, especially in residential district heating with a large amount of pipeline. This paper proposes the coefficient of performance (COP) improvement of the ASHP heating system through variable temperature difference and flow rate of circulation water loop, showing the feasibility and benefit of large temperature difference with small flow rate. A high-fidelity dynamical model is first built using Dymola, followed by the experiments verification at the environmental laboratory. On all testing conditions, the system COP of large temperature difference with small water flow rate shows average 6% to 8% improvement compared to small temperature difference with large water flow rate. Further, a demonstration heating project of the ASHP system was tested onsite under a realistic operating condition. The recorded hourly operation data showed an average system COP of 2.15 at the condition of large temperature difference, which is about a 7% improvement compared to the small temperature difference condition for the typical heating day.

Seepage and heat transfer characteristics of sandstone thermal reservoir under aquitard damage

Flow and thermal breakthroughs are the main reasons for the reduction in the operational efficiency of a single-well groundwater heat pump (SWGWHP) system. Furthermore, a large initial pumping flow rate, attributed to the large initial heating/cooling load of the building, can consolidate and damage the aquifer. In this study, an aquitard damage test bench was constructed to investigate the formation and development of flow and thermal breakthroughs during the operation of the SWGWHP system by varying the initial recharge rate (Q), aquifer thickness (H), and the time difference between pumping and recharge (Δt); and to investigate the aquifer damage, seepage, and heat transfer patterns. The results indicated that pressure was the main factor that damaged the aquitard. Aquitard damage can cause or aggravate the flow breakthrough phenomenon. The flow breakthrough strength is the main factor affecting the thermal breakthrough strength. The results of the orthogonal test analysis indicate that the order of the primary and secondary influencing factors of the flow breakthrough strength and operating time efficiency is aquitard thickness (H) > initial recharge rate (Q) > pumping and recharging time difference (Δt). The existence of the aquitard reduced the flow breakthrough strength by 15.2–33.2% and prolonged the efficient operation time of the system by 2.5–5 times. Based on quantitative analyses of the flow and thermal breakthrough strengths, and the variation in the system coefficient of performance, this study reveals the reasons for the formation of thermal breakthrough and provides theoretical suggestions to ensure a safe and stable operation of the SWGWHP system. The results of the study can guide practical installations as well as future research on SWGWHP systems.

Dynamic Pressure Measurements During Vitrectomy in a Model of the Eye.

PurposeTo accurately evaluate pressure changes during vitrectomy in a rigid model of the vitreous chamber and to test the efficiency of the EVA phacovitrectomy system (Dutch Ophthalmic Research Center) in terms of compensation of intraocular pressure variations.MethodsWe tested 23-, 25-, and 27-gauge double-blade vitreous cutters in both vented global pressure control and automatic infusion compensation (AIC) modes in a vitreous chamber model, mimicking the real surgical procedure. Balanced salt solution and artificial vitreous, similar to the real vitreous body, were used. We tested both standard-flow (SF) and high-flow (HF) infusion systems, varying the infusion pressure between 20 and 40 mm Hg. In each experiment, flow rate was also measured.ResultsPressure drop was rapidly and efficiently compensated when 23- and 25-gauge cutters were used in AIC mode, with infusion pressures ranging between 30 and 55 mm Hg. The 27-gauge cutter was less efficient in compensating pressure variations. Pressure fluctuations related to the high-frequency motion of the cutter blade were small compared to the overall pressure variations. The use of the HF infusion system resulted in larger flow rates and lower pressure changes compared to the SF infusion system.ConclusionsDespite the rigid material of the model, the present pressure measurements are in line with previous studies performed on porcine eye. The use of AIC mode compensates intraoperative pressure drops efficiently, with both 23- and 25-gauge cutters. The HF infusion system is more efficient than the SF infusion system.Translational RelevanceThe AIC infusion mode efficiently compensates intraoperative pressure drops, in both 23- and 25-gauge experimental vitrectomy. The HF infusion system resulted in larger flow rate and lower pressure changes.

Performance investigation and feasibility study of novel gas foil thrust bearing for hydrogen fuel cell vehicles

Centrifugal air compressors are promising due to their zero emissions, long driving range, and wide fuel sources. The gas foil thrust bearing (GFTB) is considered as one of the key components in the centrifugal air compressor to guarantee the system is oil-free and reliable due to there is self-acting and high speed. However, the gas foil thrust bearings were all of lower capacity in previous research. In this study, the effects of each foil and nominal clearance on the static performance are developed experimentally. The optimal GFTB with higher capacity is obtained. The feasibility study of the proposed GFTB is carried out, which is installed on the ultra-high-speed centrifugal air compressor. The result shows that the proposed GFTB can run stably and efficiently in the full speed ring, and the high-pressure ratio and large flow rate of the air compressor also can be ensured. The results play an important role in guiding the stable operation of centrifugal air compressors applied in hydrogen fuel cell vehicles (HFCVs).

Experimental study on thermal hydraulic characteristics of natural circulation loop under motion condition

• Comparatively studied thermal hydraulic characteristics of natural circulation loop under various motion conditions. • Obtained the periodic average frictional resistance coefficient and Nu. • Obtained the empirical relation of frictional resistance coefficient in turbulent region. • Under large flow rate conditions, rolling motion affects heat transfer characteristics mainly by affecting flow rate. • Some suggestions on the layout of marine natural circulation loop were given. In this present paper, an experimental research was carried out to investigate the influence of various motion conditions on the flow and heat transfer characteristics in natural circulation loops. A natural circulation loop was built on the six-degree-of-freedom motion experiment platform at Xi’an Jiaotong University (XJTU). First, it was found that the small acceleration heaving would not cause significant changes on flow rate of the natural circulation loop. Then, the influence mechanism of rolling motion on the natural circulation loop is different as the central axis of rolling is changed. The increase of additional inertial force along the coolant flow direction causes larger flow fluctuation. The periodic average frictional resistance coefficient under different working conditions is obtained, which is divided into flow fluctuation region ( Re < 5000) and turbulence region (5000 < Re < 35000). Last, according to the experimental data, a mathematical model to predict the periodic average frictional resistance coefficient which is suitable for the turbulent region is obtained, and the deviation between the predicted value and the experimental data is less than 20%. Beyond that, the period average Nu under different working conditions is also achieved. It shows that the rolling motion promotes the heat transfer with the small flow rate, while the rolling motion affects the heat transfer characteristics mainly by affecting the flow rate under the large flow rate conditions. Based on our research, some suggestions on the layout of marine natural circulation loop were given.

Ice ablation by pyroclast impact during subglacial fragmentation-dominated eruptions

Understanding magma-ice interaction processes is critical for mitigation of the hazards generated by subglacial explosive volcanism, including large flowrate meltwater floods and fine-grained volcanic ash. We propose and evaluate a subglacial eruption mechanism with potential for rapid ablation of the overlying ice that involves the impact of pyroclasts on the ice surfaces of depressurised, vapour dominated ice cavities that surround subglacial vents. Such impacts are likely to cause considerable fracturing and mechanical fragmentation of the ice and thus increase the heat transfer area available for ice-melt. This mechanism has not, to our knowledge, been explored previously in the literature, but we find that published experimental work on impact cratering of icy solar system bodies can be used to predict fragmentation damage by pyroclast impact. Our principal conclusions are as follows. (1) Ice ablation rates of order 100 m h−1 are predicted, for typical pyroclast velocities, provided that the mechanism is sustained. (2) The thermal energy of the eruption, together with the size of the ice fragments produced, is sufficient to prevent accumulation of fractured ice within the cavity. (3) Upward ablation of the ice cavity roof results in a progressive decrease in pyroclast impact velocity that is partly compensated by downward movement of the roof by ductile ice flow. (4) This ice ablation mechanism is likely common during subglacial eruptions on the relatively steep slopes of ice-covered stratovolcanoes, where steepness of slope and ice thickness are favourable for rapid drainage of meltwater by gravity and consequent depressurisation of the cavity.

Numerical Simulation Research on the Pressure Relief and Permeability Enhancement Mechanism of Large-Diameter Borehole in Coal Seam

In order to achieve high-efficiency extraction of coal seams with large-diameter borehole and large flow rates, and to rapidly reduce coal seam gas content and pressure, a large-diameter borehole coal seam pressure relief and permeability enhancement technology is proposed. In this paper, numerical simulation is used to study the mechanism of pressure relief and permeability enhancement in coal seams with large-diameter boreholes, and the evolution of stress, cracks, gas, and permeability of coal bodies around boreholes with different diameters is discussed. The research results show that the stress changes in the coal body around the borehole are symmetrically distributed around the borehole. The stress evolution controls the evolution of the coal body’s cracks. Firstly, damage occurs around the borehole and then extends to the upper left and right corners, like a butterfly spreading its wings. The crushing zone increases with the increase of the hole diameter, and the impact radius of the 100-mm, 200-mm, 300-mm, and 350-mm diameter borehole rupture is 0.375 m, 0.65 m, 1.0 m, and 1.25 m, respectively. The rupture radius of the double 350-mm diameter borehole can reach 2.4 m. The larger the diameter of the borehole, the more fissures will be produced, and the air permeability of the coal body in the affected coal seam area will obviously increase. The research results provide theoretical support for gas drainage in soft, low-permeability, high-gas coal seams.

Prediction of Heat Transfer and Fluid Flow Effects on Entropy Generation in a Monolithic Catalytic Converter Using Large-Eddy Simulation.

In the present work, heat transfer and fluid flow and their effects on entropy generation in a realistic catalytic converter of a Lada Niva 21214 vehicle are studied using large eddy simulation. At first, the pressure drop over the catalytic converter is measured for dry air at constant temperature ( K), different volumetric flow rates, and extrapolated to large volumetric flow rates for dry air ( K) and for the exhaust gas under realistic engine conditions ( K) using the Darcy–Forchheimer relation. Then, coupled heat and fluid flow phenomena inside the catalytic converter are analyzed for nonreacting isothermal conditions and nonreacting conditions with conjugate heat transfer by using the large-eddy simulation. The predicted pressure drop agrees well with the measured and extrapolated data. Based on the obtained numerical results, the characteristic flow features are identified, namely: the impinging flow with stagnation, recirculation, flow separation and laminarization within the fine ducts of the monolith, which depends on the heat transfer through temperature-dependent thermophysical properties of exhaust gas. Moreover, due to high-velocity gradients at the wall of the narrow ducts in the monolith, entropy production by viscous dissipation is observed predominantly in the monolith region. In contrast, entropy production due to heat transport is relatively small in the monolith region, while it overwhelms viscous dissipation effects in the pipe regions.

Experimental Characterization of the Influence of Ore Drawing Parameters on Tailing Deposition

The sedimentary structure is important for the engineering design, operation, and safety evaluation of tailing dams. For upstream-method tailing dams, tailing slurry flows and deposits in the pond and forms a complex dam structure. Ore drawing parameters (e.g., slurry concentration and flow rate) have significant influence on the sedimentary structure of tailing dams. However, there is a lack of unified and quantitative understanding of the complicated effects of ore drawing parameters on the deposition behaviour of tailings. In the present study, flume tests were applied to investigate the characteristics of the sedimentary structure of tailing dams. Seven ore drawing experiments were conducted to simulate different slurry concentrations and flow rates. The distribution of characteristic particle sizes d 50 and d 10 of sediment was obtained. Furthermore, considering two dominant features of particle size distribution, a mathematical model for the equation between characteristic particle size and deposition distance was established. The exponential part of this equation describes the decreasing trend of the characteristic particle size, and a smooth step function is introduced to characterize the abrupt decrease in particle size. The experimental data of d 50 and d 10 in all these test cases can be approximated by the equation with correlation coefficients R 2 greater than 0.861. As the slurry concentration of ore drawing increases, the hydraulic sorting gradually weakens. The characteristic particle size distribution curves corresponding to a larger flow rate are generally located above those corresponding to a small flow rate, indicating that the larger the flow rate is, the coarser the sediment. This study provided useful information for the determination of ore drawing parameters in actual tailing dams. The mathematical model of tailings’ particle size distribution can be further used for refined modelling of tailing dams, so as to analyse the safety and stability of the dams.

Experimental study on fiber suspension in a centrifugal pump by PIV

Abstract To study the influence of fiber particles on the flow field within the passages of an open impeller centrifugal pump, an experiment was performed. The hair fiber was used as solid particle phase in this experiment. After measuring the performance characteristic and PIV data, the flow field in impeller was measured and analyzed. It was shown that at the concentration of 0.1%, a varied distribution of relative velocity from different flow channels was observed. The outlet velocity of the impeller in the second flow channel was obviously higher than that in the first flow channel. The variation of the relative velocity near the hub tended to be consistent at the position of the front plane and the middle plane of the impeller. At 0.2% concentration, the relative velocity at the suction surface of the two channels changes more sharply than the other positions. Within the second channel, it was found that the relative velocity under low flow condition was obviously higher than that under rated and large flow rates. Under different concentrations, the increase of the relative velocity at low flow rate changed intensely compared with the other two conditions. The low velocity zone will be formed near the middle part of the suction surface of the flow channel which gradually decreases with the increase of the flow rate. The external characteristic test shows that the efficiency of the pump and the drag reducing feature increase with the increase of concentration.

Experimental investigation on thermal management of lithium-ion battery with roll bond liquid cooling plate

• A liquid cooling plate with flexible flow channel design is fabricated using roll bond process, its thermal performance is verified experimentally. • Using proposed liquid cooling plate, the temperature of battery module is below 35 °C, and the temperature difference is within 5 °C at 2C discharge rate (750 W). • Compared with other studies, roll bond liquid cooling plate has strong heat transfer capacity, light weight and low cost. • Experimental results show that with Re increases, the improvement of the thermal performance of rib is greater than cavity. Lithium-ion batteries are widely used in energy storage systems owing to their high energy storage density, high energy storage efficiency, and stability. However, the power density of energy storage system is usually limited by thermal management. In this paper, the temperature distribution of the battery along the height direction is obtained. The thermal management analysis of two 100Ah lithium-ion batteries in series is carried out by using roll bond liquid cooling plate which has significant heat dissipation performance and low manufacturing cost. Cavity and rib structures are embedded in the serpentine channel and compared to the direct channel. Effects of flow rate and contact area are studied. The experimental results show that when charging and discharging at 1C, the cell temperature can be controlled by a low flow rate(12L/h) and the cavity structure with a large heat exchange area is dominant. In 2C discharge, large flow rate(>20L/h) is required. Rib structure with high flow rate and low water temperature has better performance. When discharged at 2C rate(750 W), roll bond liquid cooling plate can control the battery temperature below 35 °C and the temperature difference within 5 °C, at the cost of small pressure drop(5818 Pa). Compared with other studies, roll bond liquid cooling plate has strong heat transfer capacity, light weight and low cost, which is a promising solution for thermal management of energy storage batteries.

Diagnosis and control of abnormal combustion of hydrogen internal combustion engine based on the hydrogen injection parameters

In order to improve the limitation of evaluating the abnormal combustion problem of hydrogen internal combustion engine by single index, the abnormal combustion risk coefficient is proposed and defined based on AHP(Analytic Hierarchy Process)-entropy method. The abnormal combustion risk of PFI hydrogen internal combustion engine is comprehensively evaluated from multiple indexes such as the uniformity coefficient of the mixture, the temperature of the hot area, the maximum temperature rise rate, the residual amount of hydrogen in the intake port and the cylinder temperature at the end of the exhaust. The influence of hydrogen injection parameters on abnormal combustion was explored. The results show that the temperature and the maximum temperature rise rate in the hot area decrease first and then increase with the increase of hydrogen injection angle and hydrogen injection flow rate. Although large hydrogen injection angle and hydrogen injection flow rate can reduce the cylinder temperature at the end of exhaust, they will increase the residual hydrogen amount in the intake port. Appropriate hydrogen injection angle and hydrogen injection flow scheme can ensure that all parameters are at a better level, so that the risk coefficient of abnormal combustion decreases by 2.1%–5.5%, and the possibility of abnormal combustion is reduced. • Proposing the concept of abnormal combustion risk coefficient for the first time. • Comprehensive consideration of factors that may cause abnormal combustion. • The risk of abnormal combustion was assessed using the Analytic Hierarchy Process-entropy method. • This study helps to quantify the trend of abnormal combustion occurrence in hydrogen internal combustion engines. • It provides a new method for suppressing abnormal combustion issues in hydrogen internal combustion engines.