EXPERIMENTAL STUDY ON THE INJECTION CHARACTERISTICS OF HYDROTREATED VEGETABLE OIL IN A DIESEL ENGINE COMMON RAIL SYSTEM

The diesel combustion is primarily controlled by the fuel injection process. The start of injection therefore has a significant effect in the engine, which relates large amount of injected fuel at the beginning of injection to produces a strong burst of combustion with a high local temperature and high NOx formation. This paper investigated the impact of Hydrotreated Vegetable Oil (HVO) and blends of 10%, 20%, 30%, 50%, 80% by mass of HVO with commercial diesel fuel (mixed 7% FAME-B7) to injection process under the Zeuch’s method and compared to that of B7. The focus was on the injection flow rate in the variation of injection pressures, back pressures, and energizing times. The experimental results indicated that injection delay was inversely correlated to HVO fraction in the blend as well as injection pressure. At different injection pressures, HVO revealed a slightly lower injection rate than diesel that resulted in smaller injection quantity. Discharge coefficient was recognized larger with HVO and its blends. At 0.5ms of energizing time, injection rate profile displayed the incompletely opening of needle. Insignificant difference in injection rate was observed as increasing of back pressure.

Numerical investigation of the effect of injection strategy on a high-pressure isobaric combustion engine

High-pressure isobaric combustion adopted in the double compression expansion engine (DCEE) has the prospect to achieve higher thermal efficiency compared to conventional diesel combustion. This work numerically explored the effects of various injection strategies on the combustion and emission characteristics of isobaric combustion. The study developed a mathematical model to predict the injection rate profile. After validations, extensive simulations were conducted with a peak pressure of up to 300 bar – mimicking the high-pressure unit of DCEE. Several major engine design parameters such as the exhaust recirculation gas (EGR) rate, engine speed, injection strategy, and intake pressure were varied and evaluated. The results demonstrated that a higher EGR rate resulted in a higher exhaust loss but a lower heat transfer loss owing to the lower combustion temperature, so the thermal efficiency exhibited a firstly growing and then declining trend. Besides, a higher engine speed generated a higher thermal efficiency due to the shorter combustion duration and thus lower heat transfer loss. Consequently, a peak thermal efficiency of 47.5% was achieved at EGR = 50% and 1800 rpm. The high-pressure cylinder performance can also be improved with an appropriate introduction of the isochoric combustion, but its impact on the whole DCEE setup needs further investigation.

Generalized Guidance Formulation for Impact Angle Interception with Physical Constraints

This paper proposes an optimal impact angle control guidance law for homing missiles with a narrow field-of-view of the seekers. As groundwork for designing a guidance law, we first present a general guidance structure that can achieve any terminal constraint of the line-of-sight rate based on the optimal control theory. We configure the desired profile of the line-of-sight rate using a saturation function whose exact form is determined to satisfy the required boundary conditions. By combining the line-of-sight rate profile with the optimal guidance structure, we develop a guidance law that achieves an impact angle interception with the field-of-view constraint. Herein, as the entire guidance structure is derived based on exact kinematics without any approximation, the proposed law ensures the accurate impact angle interception for various engagement scenarios. This precise consideration of the engagement kinematics also accurately ensures the energy optimality of preventing the excessive use of control inputs when homing. To evaluate the performance of the proposed method, numerical simulations with various engagement scenarios are conducted, and the results demonstrate that the proposed law allows missiles to accurately intercept their targets with the desired impact angles and without violating the prescribed field-of-view constraint.

A Heuristic Algorithm for Rate-Profiling of Polarization Adjusted Convolutional (PAC) codes

<div>In this paper, we propose a heuristic algorithm for rate-profile construction of Arikan's Polarization Assisted Convolutional (PAC) codes. This method can be used for any blocklength, rate and convolutional precoding polynomial. The proposed algorithm tries to create a rate-profile for which the corresponding PAC code is, in a sense, locally optimized for having maximum possible minimum distance.</div><div>Simulation results show that PAC codes constructed with the proposed algorithm perform better in terms of frame erasure rate (FER) compared to the PAC codes constructed with rate profiling designs in existing literature for various list lengths. Further, by using a (64, 32) PAC code as an example, it is shown that the choice of convolutional precoding polynomial can have a significant impact on FER performance. Finally, we demonstrate that for a target FER of $\mathbf{10^{-5}}$, (128, 72) PAC codes constructed with our proposed algorithm is just 0.35 dB away from the information theoretic limit at this blocklength.</div>

A Heuristic Algorithm for Rate-Profiling of Polarization Adjusted Convolutional (PAC) codes

<div>In this paper, we propose a heuristic algorithm for rate-profile construction of Arikan's Polarization Assisted Convolutional (PAC) codes. This method can be used for any blocklength, rate and convolutional precoding polynomial. The proposed algorithm tries to create a rate-profile for which the corresponding PAC code is, in a sense, locally optimized for having maximum possible minimum distance.</div><div>Simulation results show that PAC codes constructed with the proposed algorithm perform better in terms of frame erasure rate (FER) compared to the PAC codes constructed with rate profiling designs in existing literature for various list lengths. Further, by using a (64, 32) PAC code as an example, it is shown that the choice of convolutional precoding polynomial can have a significant impact on FER performance. Finally, we demonstrate that for a target FER of $\mathbf{10^{-5}}$, (128, 72) PAC codes constructed with our proposed algorithm is just 0.35 dB away from the information theoretic limit at this blocklength.</div>

Effects of nozzle hole size and rail pressure on diesel spray and mixture characteristics under similar injection rate profile – experimental, computational and analytical studies under non-evaporating spray condition

In the present work, effects of nozzle hole size and rail pressure under non-evaporating spray condition are demonstrated. Three single hole injectors with the bore size of 0.101, 0.122, and 0.133 mm are experimented with injection pressures of 140, 45, and 38 MPa respectively to achieve similar injection rate profile. Diesel spray experiments implement Diffused Backlight Illumination Technique where diffused background is obtained for the High Speed Video camera imaging. Experimental results are then validated with computational and analytical studies. The CFD simulation requires the injection rate profile and spray cone angle as a primary input; thus, based on the High Speed Video Camera start of injection frame the 5 kHz Butterworth low-pass frequency filter is applied to the injection rate raw data. While, the spray cone angle is predicted using a simple model obtained from the relationship between the injection velocity, fluctuating velocity at the nozzle exit and total pressure loss factor of the injector. The experimental spray tip penetration of all three injectors is almost identical as the similar injection rate profile is adopted. Although, the mixture characteristics are better for 0.101 mm hole diameter since the smaller hole diameter with highest injection pressure depicts larger spray angle and better atomization. The computational study agrees with experiments qualitatively; however, the quantitative and qualitative agreements are seen in the analytical study.

A Single Residue on the WPD-Loop Affects the pH Dependency of Catalysis in Protein Tyrosine Phosphatases

<p>Catalysis by protein tyrosine phosphatases (PTPs) relies on the motion of a flexible protein loop (the WPD-loop) that carries a residue acting as a general acid/base catalyst during the PTP-catalyzed reaction. The orthogonal substitutions of a non-catalytic residue in the WPD-loops of YopH and PTP1B results in shifted pH-rate profiles, from an altered kinetic p<i>K</i>_a of the nucleophilic cysteine. Compared to WT, the G352T YopH variant has a broadened pH-rate profile, similar activity at optimal pH, but significantly higher activity at low pH. Changes in the corresponding PTP1B T177G variant are more modest and in the opposite direction, with a narrowed pH profile and less activity in the most acidic range. Crystal structures of the variants show no structural perturbations, but suggest an increased preference for the WPD-loop closed conformation. Computational analysis confirms a shift in loop conformational equilibrium in favor of the closed conformation, arising from a combination of increased stability of the closed state and destabilization of the loop-open state. Simulations identify the origins of this population shift, revealing differences in the flexibility of the WPD-loop and neighboring regions. Our results demonstrate that changes to the pH dependency of catalysis by PTPs can result from small changes in amino acid composition in their WPD-loops affecting only loop dynamics and conformational equilibrium. The perturbation of kinetic p<i>K</i>_a values of catalytic residues by non-chemical processes affords a means for nature to alter an enzyme’s pH dependency by a less disruptive path than altering electrostatic networks around catalytic residues themselves. </p>

A Novel Cardiac Force Index Measured by Digital Devices and Applied to the G Tolerance Test among Military Aircrew: An Observational Study (Preprint)

BACKGROUND Military aircrew are occupationally exposed to a high-G environment. G force causes blood to flow to the lower body region and challenges their cardiac function and anti-G straining maneuver effectiveness. A tolerance test is necessary for every military aircrew member before undergoing flight training. A novel cardiac force index (CFI) has been developed and used to assess long-distance running by mobile health (mHealth) technology. There is still no study to monitor the CFI by wearable devices during the G tolerance test. OBJECTIVE We added the cardiac function parameter CFI to the G tolerance test and elucidated the relationship between cardiac function and G tolerance among military aircrew. METHODS A noninvasive device, BioHarness 3.0, was used to measure heart rate (HR) and activity while resting and walking on the ground. The mathematical formula for cardiac function calculation is CFI = weight × activity/HR. The cardiac force ratio (CFR) is calculated by walking CFI (WCFI)/resting CFI (RCFI). G tolerance includes relaxed G tolerance (RGT) and straining G tolerance (SGT) tested by a human centrifuge under the gradual-onset-rate profile. RESULTS In total, 92 male participants voluntarily completed this study. The average values of RCFI, WCFI, and CFR were 0.02 [SD 0.04], 0.15 [SD 0.04], and 10.77 [SD 4.11], respectively. The mean RGT and SGT were 5.1G [SD 0.9] and 7.8G [SD 1.1], respectively, in the centrifuge. The percentages of participants with RGT greater than 5G or SGT greater than 8G were equally noted as 54.3%. Each 100-unit increase in WCFI increased RGT by 0.14G [SE 0.02, 95% CI 0.09 to 0.19] and by 0.17G [SE 0.03, 95% CI 0.11 to 0.22], corresponding to SGT. In addition, there was an increased chance of RGT values higher than 5G and SGT values higher than 8G according to the increase in WCFI. CONCLUSIONS Our results suggested that WCFI is positively correlated with G tolerance in the centrifuge and has the potential to be used for military aircrew selection.

A calculation method and experiment study of high-pressure common rail injection rate with solenoid injectors

The high-pressure common rail system has been widely used owing to its precise control of fuel injection rate profile, which plays a decisive role in cylinder combustion, atomization, and emission. The fuel injection rate profile of high-pressure common rail system was studied, and a fuel injection rate profile calculation model is proposed. The model treats the injector as a black box. Some measured data are needed to calculate the parameters in the model. The rise and fall of injection rate is regarded as trigonometric function to reduce the complexity and increase the accuracy. The model was verified using two different types of fuel injectors. The model calculation results were evaluated under various data input conditions. The results show that the model has good applicability to different input data and injectors. In addition, because the model building requires a large amount of experimental data, a comprehensive analysis of various input data was also conducted. The injection profile was analyzed from a new perspective and the regularity of injection rate profile was established.