Rocket Propellant 3 Research Articles

Study on RP-3 Aviation Fuel Vapor Concentration

Fuel vapor concentration is a key parameter for assessing the flammability of aircraft fuel tanks. However, the current research on RP-3 (Rocket Propellant-3) fuel vapor concentration is inadequate. This study categorizes fuel components by the number of carbon atoms and utilizes Raoult’s law to estimate the gas–liquid equilibrium relationship of each constituent element under equilibrium conditions. The equilibrium-state model is experimentally validated, and the differences in the constituents and fuel vapor concentrations of RP-3 and Jet-A (Jet Fuel-A) fuels are analyzed. In addition, an empirical correlation between the overall hydrocarbon concentration of RP-3 fuel vapor and the temperature and pressure in the equilibrium state is established, providing a theoretical basis for determining RP-3 fuel vapor concentration in related investigations. Furthermore, a transient prediction model of fuel vapor concentration is developed using the lumped parameter approach that considers the heat exchange among the fuel, gas, wall, and environment. The model’s accuracy is confirmed by comparing it to existing literature. Then, the temperature and fuel vapor concentration variation patterns in the fuel tank are calculated and evaluated under two typical flight scenarios. The results show a significant difference between the calculated fuel vapor concentration values obtained through equilibrium-state and transient models. Therefore, in the design of fuel vapor catalytic inerting systems, it is crucial to consider both the equilibrium and transient fuel vapor concentration values rather than relying solely on the former. Throughout the flight envelope, gas phase and fuel phase temperatures in RP-3, Jet-A, and C10H22 fuel tanks exhibit minimal differences. However, significant variations in fuel vapor concentration exist depending on the flight state and envelope. Hence, regarding RP-3 as equivalent to C10H22 is inappropriate. Additionally, fuel vapor concentration is a more suitable metric than fuel temperature for assessing fuel tank flammability.

Molecular dynamics simulation of thermophysical properties of binary RP-3 surrogate fuel mixtures containing trimethylbenzene, n-decane, and n-dodecane

• Binary RP-3 surrogate fuel mixtures containing trimethylbenzene (TMB), n-decane, and n-dodecane are investigated via EMD simulations. • TraPPE-UA force field can appropriately describe the densities and thermal conductivities of TMB and the mixtures. • Variation ranges of the bond angles become broader and n-decanes shrink with the increasing of the temperature. • Analysis of RDFs and the ADFs are carried out. Trimethylbenzene (TMB), n-decane, n-dodecane and their mixtures are commonly used in surrogate fuel of aviation kerosene. To date, molecular dynamic studies on the thermophysical properties of TMB and their mixtures are very few. In this study, equilibrium molecular dynamics (EMD) simulations with the TraPPE-UA force field are carried out to simulate the densities and thermal conductivities of Rocket Propellant-3 (RP-3) aviation kerosene surrogate mixtures, C 10 + 1,2,4-TMB and C 10 + C 12 , under sub/supercritical pressure. Results show that the simulated densities and thermal conductivities of TMB and the mixtures are in good agreement with the NIST data, and the two surrogate models can provide reasonable surrogate accuracy in predicting the thermophysical properties of aviation kerosene RP-3. The analysis of radial distribution functions, angular distribution functions, end-end length and dihedral angle distributions is carried out to better understand the temperature effect on the structure and thermophysical properties of the surrogates. It is found that the n-decane chains become shrinking and more twisted with the increasing of the temperature which reduce the thermal conductivity of the surrogates. This research offers a good reference for the analysis thermophysical properties of n-alkanes and TMB-based fuels.

Characterizing combustion performance and PM emissions of an aviation compression ignition engine by fueling RP-3 kerosene and RP-3/pentanol blends

General aviation (GA) aircraft generally driven by aviation piston engines (APE) are currently experiencing promising growth globally. To relieve the fossil fuel scarce, the application of alternative fuels was extensively encouraged for green GA development. This study aims to investigate the suitability of using aviation kerosene rocket propellant 3 (RP-3) and its pentanol blends (by 30% volume fraction) in an aviation compression ignition (CI) engine, by comparing their combustion performance and emission characteristics differences under various injection timings with baseline diesel. The major combustion parameters including the in-cylinder pressure, heat release rate, ignition delay, combustion duration, indicated thermal efficiency (ITE), and indicated specific fuel consumption (ISFC) were evaluated as the crank angle (CA) 50 swept from 9 to 15° crank angle after top dead center (ATDC). The ITE of RP-3/Pentanol blends presented to be higher than those of diesel by 4.2%−5.0%, and pure RP-3 by 2.6%−3.4%. The improved ITE of the blended fuel is due to the longest ignition delay and the shortest combustion duration under all the CA50. Moreover, the particulate matter (PM) emissions with the number concentration, geometric mean diameter (GMD), size-resolved distribution characteristics were quantitatively analyzed for all the test fuels. RP-3/Pentanol dramatically reduced the number-based PM, by over 50% and two magnitudes of order lower than those of RP-3 and diesel, respectively. Improved PM emissions from the alcohol blends intensively was caused by the better premixing and evaporating states with subsequent homogeneous combustion. Additionally, the PM emissions of the three fuels exhibited different sensitivities to the varied injection timings. With the retardance of injection timings, the PM declined apparently for diesel and RP-3 due to prolonged ignition delay and decreased in-cylinder temperature, but remained nearly unchanged for RP-3/Pentanol because of the growth of nucleation mode PM.

Study of combustion characteristics of diesel, kerosene (RP-3) and kerosene-ethanol blends in a compression ignition engine

Due to safety, economy and other considerations, Heavy Fuel Aviation Piston Engines (HF-APES) powered by light diesel or aviation kerosene with high ignition point were expected to replace aviation gasoline engines. The present study compared the combustion characteristics of diesel, aviation kerosene rocket propellant 3 (RP-3) and RP-3/ethanol blends in a four-cylinder Turbo Diesel Common-rail Injection (TDCI) engine. The results demonstrated, compared with diesel, RP-3 had similar combustion performance at maximum torque speed and medium speed. The maximum in-cylinder pressure and temperature are almost the same. RP-3 can be applied to compression ignition engines and can replace diesel in civil and military aviation. The addition of ethanol could improve the overall combustion performance and increase the combustion stability of aviation kerosene in diesel engines, effectively solved the combustion deterioration of RP-3 under medium speed and low load (when indicated mean effective pressure (IMEP) was 0.24 MPa, the peak pressure in the cylinder of E20 was 10.5% higher than E0, and the second-stage maximum heat release rate was 2.9 times that of E0). Compared with diesel, the equivalent specific fuel consumption (ESFC) of RP-3 was lower under most working conditions. After adding ethanol to RP-3, the ESFC was increased by 2.0–9.1%; RP-3 showed higher indicated thermal efficiency (ITE) than diesel by 7.7–8.2%.

Experimental analysis on mechanism and prediction of thermo-acoustic instability of supercritical RP-3 fuel flowing in a vertical upward channel

This article presented an experimental investigation of thermo-acoustic instability of RP-3 (Rocket Propellant 3) aviation kerosene under supercritical pressures in a vertical upward circular channel. The oscillation characteristics of measured parameters were studied. The mechanisms and characteristics of unstable flow and heat transfer were analyzed. The effects of operating parameters, including the inlet fluid temperature, inlet fluid pressure, mass flow rate, and heat flux, on flow and heat transfer instabilities were discussed. The investigation on boundary between stable and unstable conditions under various operating parameters was performed, and two new empirical correlations for critical heat flux prediction were obtained. Results indicate that the coupling relation between the inside-wall temperature, outlet fluid temperature, and inlet-outlet pressure drop is found. The instability of pseudo-film boiling leads to this unstable phenomenon. The critical heat flux increases as the inlet fluid pressure rises, while increases first and then decreases with the increasing Reynolds number of inlet fluid. The proposed correlations work reasonably well in predicting the onset of thermo-acoustic instability.

Combustion and Emission Characteristics of a Diesel Engine Fueled with Diesel–Rocket Propellant-3 Wide Distillation Blended Fuels

AbstractIn this work, three diesel–rocket propellant-3 wide distillation blended fuels (WDBF) including D80K20 [80% diesel and 20% rocket propellant-3 (RP3) by volume], D60K40, and D40K60 were prep...

Numerical study on non-uniform heat transfer deterioration of supercritical RP-3 aviation kerosene in a horizontal tube

Abstract The convective heat transfer of supercritical-pressure RP-3 (Rocket Propellant 3) aviation kerosene in a horizontal circular tube has been numerically studied, focusing mainly on the non- uniform heat transfer deterioration along the circumferential direction. The governing equations of mass, momentum and energy have been solved using the pressure-based segregated solver based on the finite volume method. The re-normalization group (RNG) k-e turbulence model with an enhanced wall treatment was selected. Considering the heat conduction in the solid wall, the mechanism of heat transfer deterioration and the buoyancy effect on deteriorated heat transfer were discussed. The evolution of secondary flow was analyzed. Effects of the outer-wall heat flux, mass flux, pressure and tube thermal conductivity on heat transfer were investigated. Moreover, the buoyancy criterion and the heat transfer correlation were obtained. Results indicate that the poor flow performance of near-wall fluid causes the pseudo-film boiling, further leads to the heat transfer deterioration. The strong buoyancy has an effect of enhancing the heat transfer at the bottom of tube, and weakening the heat transfer at the top of tube, which results in the non-uniform inner-wall temperature and heat flux distributions. Decreasing the ratio of outer-wall heat flux and mass flux, increasing the pressure could weaken the heat transfer difference along the circumferential direction, while the effect of thermal conductivity of tube on the circumferential parameters distributions is more complicated. When the buoyancy criterion of (Grq/Grth)max ≤ 0.8 is satisfied, the effect of buoyancy could be ignored. The new correlations work well for non-uniform heat transfer predictions.

Weak Knock Characteristic Extraction of a Two-Stroke Spark Ignition UAV Engine Burning RP-3 Kerosene Fuel Based on Intrinsic Modal Functions Energy Method

To solve the problem of the weak knock characteristic extraction for a port-injected two-stoke spark ignition (SI) unmanned aerial vehicle (UAV) engine burning aviation kerosene fuel, which is also known as the Rocket Propellant 3 (RP-3), the Intrinsic modal Functions Energy (IMFE) method is proposed according to the orthogonality of the intrinsic modal functions (IMFs). In this method, engine block vibration signals of the two-stroke SI UAV engine are decomposed into a finite number of intrinsic modal function (IMF) components. Then, the energy weight value of each IMF component is calculated, and the IMF component with the largest energy weight value is selected as the dominant characteristic component. The knock characteristic frequency of the two-stroke SI UAV engine is obtained by analyzing the frequency spectrum of the dominant characteristic component. A simulation experiment is designed and the feasibility of the algorithm is verified. The engine block vibration signals of the two-stroke SI UAV engine at 5100 rpm and 5200 rpm were extracted by this method. The results showed that the knock characteristic frequencies of engine block vibration signals at 5100 rpm and 5200 rpm were 3.320 kHz and 3.125 kHz, respectively. The Wavelet Packet Energy method was used to extract the characteristics of the same engine block vibration signal at 5200 rpm, and the same result as the IMFE method is obtained, which verifies the effectiveness of the IMFE method.

ReacNetGenerator: an automatic reaction network generator for reactive molecular dynamics simulations.

Reactive molecular dynamics (MD) simulation makes it possible to study the reaction mechanism of complex reaction systems at the atomic level. However, the analysis of MD trajectories which contain thousands of species and reaction pathways has become a major obstacle to the application of reactive MD simulation in large-scale systems. Here, we report the development and application of the Reaction Network Generator (ReacNetGenerator) method. It can automatically extract the reaction network from the reaction trajectory without any predefined reaction coordinates and elementary reaction steps. Molecular species can be automatically identified from the cartesian coordinates of atoms and the hidden Markov model is used to filter the trajectory noises which makes the analysis process easier and more accurate. The ReacNetGenerator has been successfully used to analyze the reactive MD trajectories of the combustion of methane and 4-component surrogate fuel for rocket propellant 3 (RP-3), and it has great advantages in terms of efficiency and accuracy compared to traditional manual analysis.

Knock combustion investigation on a two-stroke spark ignition UAV engine burning RP-3 kerosene fuel

Purpose The purpose of this paper is to investigate the knock combustion characteristics, including the combustion pressure, heat release rate (HRR) and knock intensity of aviation kerosene fuel, that is, Rocket Propellant 3 (RP-3), on a port-injected two-stoke spark ignition (SI) engine. Design/methodology/approach Experimental investigation using a bench test and the statistical analysis of data to reflect the knock combustion characteristics of the two-stroke SI unmanned aerial vehicle (UAV) engine on RP-3 kerosene fuel. Findings Under the full load condition of 4,000 rpm, at the ignition timing of 25 degree of crank angle (°CA) before top dead centre (BTDC), the knock combustion is sensitive to the thinner mixture; therefore, the knock begins to occur when the excess air ratio is larger than 1.0. When the excess air ratio is set as 1.2, the knock obviously appears with the highest knock intensity. At the excess air ratio of 1.2, better engine performance is obtained at the ignition timing range of 20-30 °CA BTDC. However, the ignition timing at 30° CA BTDC significantly increases the peak combustion pressure and knock intensity with the advancing heat release process. Practical implications Gasoline has a low flash point, a high-saturated vapour pressure and relatively high volatility, and it is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. The authors adopt a low-volatility single RP-3 kerosene fuel for all vehicles and equipment to minimise the number of different devices using various fuels and improve the military application safety. Originality/value Most two-stroke SI UAV engines for military applications burn gasoline. A kerosene-based fuel for stable engine operation can be achieved because the knock combustion can be effectively suppressed through the combined adjustment of the fuel amount and spark timing.

Effects of injection timing and compression ratio on the combustion performance and emissions of a two-stroke DISI engine fuelled with aviation kerosene

In recent years, many civilian and military unmanned aerial vehicles (UAVs) have been powered by spark ignition (SI) piston engines fuelled with gasoline. However, the safety problems associated with the storage and transportation of gasoline are forcing manufacturers and researchers to develop an SI piston engine fuelled with heavy fuel, such as light diesel or aviation kerosene. In this study, the effects of injection timing and compression ratio on the combustion characteristics and emissions of a two-stroke engine fuelled with aviation kerosene rocket propellant 3 (RP-3) are investigated. The engine tests were carried out on a two-stroke, air cooled, direct injection, spark ignition engine at three compression ratios (7.2, 6.2, and 5.2) and injection timings from 120° crank angle (CA) before top dead center (BTDC) to 240° CA BTDC. The engine was run at 4000 rpm, 100% throttle opening, and spark timing at knock limited spark advance.The results showed that the brake power (BP) increased and the coefficient of variation of the indicated mean effective pressure (COVIMEP) decreased with the advance in injection timing. The best brake thermal efficiency (BTE) was obtained at a direct injection timing of 150 °CA BTDC. Hydrocarbon (HC) and nitric oxide (NO) emissions increased while carbon monoxide (CO) emission decreased as the direct injection timing advanced. The compression ratios were decreased from 7.2 to 5.2, and the maximum values of BP and BTE were obtained at the compression ratio of 6.2. However, the HC and NO emissions at the compression ratio of 6.2 were greater than those under other compression ratios.

Experimental investigation on heat transfer deterioration and thermo-acoustic instability of supercritical-pressure aviation kerosene within a vertical upward circular tube

The flow and heat transfer of China RP-3 (Rocket Propellant 3) aviation kerosene has been experimentally studied at supercritical pressures in a vertical upward circular tube, primarily focusing on the formation mechanisms and critical conditions for deteriorated heat transfer and thermo-acoustic instability in the regenerative cooling process. The effects of key parameters, including the heat flux, inlet fluid temperature, pressure and mass flow rate, on these two processes were investigated, and new empirical criteria regarding the critical condition for deteriorated heat transfer and thermo-acoustic instability prediction were established. Furthermore, a heat transfer correlation under stable flow conditions was developed. The results indicate that, for the supercritical convective heat transfer process, both heat transfer deterioration and thermo-acoustic instability occur when the temperature of the near-wall fluid reaches its pseudo-critical point, the former is caused by a high buoyancy and thermal acceleration, while the latter results from the pseudo-boiling effect. Increasing the inlet fluid temperature, pressure, and mass flow rate can effectively weaken these two phenomena. The critical condition and heat transfer prediction expressions can be applied to supercritical-pressure aviation kerosene-type endothermic hydrocarbon fuel.

Fuel Flow Control for Starting a Crankcase-Injected Two-Stroke Spark Ignition Engine Fueled with Kerosene (RP-3)

AbstractTo investigate the fuel flow control for starting a crankcase-injected two-stroke spark ignition (SI) engine that is fueled with rocket propellant 3 (RP-3), a fuel film compensation model f...

Diameter effect on the heat transfer of supercritical hydrocarbon fuel in horizontal tubes under turbulent conditions

This article presented a numerical investigation of supercritical heat transfer of the hydrocarbon fuel in a series of horizontal tubes with different diameters. The Reynolds averaging equations of mass, momentum and energy with the LS low-Reynolds number turbulence model have been solved using the pressure-based segregated solver based on the finite volume method. For the purpose of comparison, a four-species surrogate model and a ten-species surrogate model of the aviation kerosene RP-3 (Rocket Propellant 3) were tested against the published experimental data. In the current study, the tube diameter varied from 2 mm to 10 mm and the pressure was 3 MPa with heat flux to mass flux ratios ranging from 0.25 to 0.71 kJ/kg. It was found that the buoyancy has significant effect on the wall temperature non-uniformity in the horizontal tube. With the increase of the diameter, the buoyancy effect enhances and the thermal-induced acceleration effect reduces. The buoyancy effect makes wall temperature at the top and bottom generatrices of the horizontal tube increase and decrease, respectively. Due to the coupled effect of the buoyancy and thermal-induced acceleration caused by the significant change of the properties, as the diameter increases, the heat transfer deteriorates dramatically at the top generatrix but remains almost unchanged at the bottom generatrix at high heat flux to mass flux ratio. Heat transfer enhancement is observed at low heat flux to mass flux ratio when the tube diameter is less than 6 mm. Moreover, the safety analysis has been performed in order to optimally design the supercritical cooling system.

Combustion characteristics of a two-stroke spark ignition UAV engine fuelled with gasoline and kerosene (RP-3)

Purpose The purpose of this paper is to compare the combustion characteristics, including the combustion pressure, heat release rate (HRR), coefficient of variation (COV) of indicated mean effective pressure (IMEP), flame development period and combustion duration, of aviation kerosene fuel, namely, rocket propellant 3 (RP-3), and gasoline on a two-stoke spark ignition engine. Design/methodology/approach This paper is an experimental investigation using a bench test to reflect the combustion performance of two-stroke spark ignition unmanned aerial vehicle (UAV) engine on gasoline and RP-3 fuel. Findings Under low load conditions, the combustion performance and HRR of burning RP-3 fuel were shown to be worse than those of gasoline. Under high load conditions, the average IMEP and the COV of IMEP of burning RP-3 fuel were close to those of gasoline. The difference in the flame development period between gasoline and RP-3 fuel was similar. Practical implications Gasoline fuel has a low flash point, high-saturated vapour pressure and relatively high volatility and is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. Adopting a low volatility single RP-3 fuel of covering all vehicles and equipment to minimize the number of different devices with the use of a various fuels and improve the application safeties. Originality/value Most two-stroke spark ignition UAV engines continue to combust gasoline. A kerosene-based fuel operation can be applied to achieve a single-fuel policy.

Comparative study of combustion and emissions of kerosene (RP-3), kerosene-pentanol blends and diesel in a compression ignition engine

Aviation Piston Engines for small general aviation aircrafts are currently facing a transition from being powered by AVGAS (aviation gasoline) to being powered by heavy fuels (diesel or kerosene). The present study compared the combustion and emission characteristics of diesel, aviation kerosene rocket propellant 3 (RP-3) and RP-3-pentanol blends in a single cylinder compression ignition (CI) engine. Heat release rate, indicated thermal efficiency, ignition delay, combustion duration, and coefficient of variation (COV) of indicated mean effective pressure were experimentally determined to reflect the engine combustion performance. The results demonstrated the feasibility of RP-3 and its mild pentanol blend (20% by volume) in modern CI engines whilst further optimisation of the injection strategy is needed if a higher ratio of pentanol (40% by volume) is used. The discrepancy in terms of combustion and emissions between diesel, RP-3 and its pentanol blends are appreciable, especially for ignition delay, combustion duration and soot emissions. Compared with diesel, RP-3 improved the indicated thermal efficiency by 1.4–12.4%, but pentanol addition decreased that by 1–6.5%. RP-3 and its pentanol blends reduced the soot emissions by nearly an order of magnitude at high engine loads compared with diesel without evident impact on nitrogen oxide (NOx) emissions. Meanwhile, Carbon monoxide (CO) and total hydrocarbon (THC) emissions of RP-3 and its pentanol blends experienced a significant increase at low loads, but CO showed a slight decrease at high loads.

A simplified chemical reaction mechanism for surrogate fuel of aviation kerosene

n-Decane was chosen as a one-component surrogate fuel to investigate the combustion performance of Rocket Propellant-3(RP-3) aviation kerosene. Sensitivity analysis and the reaction-path analysis method were used to simplify the detailed reaction mechanism of n-decane, and a simplified mechanism including 36 species and 62 elementary reaction steps was obtained. Moreover, 38-step elementary reaction investigated in the reference was simulated in the paper. Numerical simulation method was conducted for both the 62-step and the 38-step reaction mechanisms using pre-evaporation combustion models. Simultaneously Bunsen burner for the combustion of premixed, pre-evaporated RP-3 aviation kerosene was designed to verify the simplified mechanism, and the temperature and gas component concentrations in the axial and radial directions at different heights were measured. The experimental results revealed that the reaction temperature and the CO2 concentration increased first and then decreased across the axial positions, but on the contrary for the O2 concentration. The temperature and the O2 concentration distributions of experimental results are in good agreement with that of numerical simulation results for the 62-step simplified reactions, and the CO2 concentration distribution is in general agreement with the numerical data. But the 38-step simplified reactions can only predict the change trend for the important parameters which are mentioned above. Through the contrastive analysis for these two kinds of simplified reactions, the 62-step reactions can more accurately simulate the combustion characteristics of RP-3 kerosene. And n-decane can be used as a one-component surrogate fuel for RP-3 aviation kerosene.